阅读说明：本技术 彩色微型led显示装置 (Color micro LED display device ) 是由 G·J·伍德盖特 J·哈罗德 M·G·鲁宾逊 于 2019-05-09 设计创作，主要内容包括：一种彩色微型LED显示装置,其包括反射光学元件的阵列和微型LED像素的阵列,该微型LED像素在整个阵列上发射均匀的颜色,该微型LED像素的阵列被布置在反射光学元件的阵列与输出基板之间。来自微型LED的光被引导到反射光学元件中,并且入射在装置中的散射区域上。经颜色转换的散射光由输出基板透射。可以提供薄且有效的显示装置,该显示装置具有高空间和角度颜色均匀性以及长的寿命。(A color micro LED display device comprising an array of reflective optical elements and an array of micro LED pixels emitting a uniform color across the array, the array of micro LED pixels being arranged between the array of reflective optical elements and an output substrate. Light from the micro-LEDs is directed into the reflective optical element and is incident on the scattering area in the device. The color-converted scattered light is transmitted by the output substrate. It is possible to provide a thin and efficient display device having high spatial and angular color uniformity and a long lifetime.)

1. A color display device comprising:

a plurality of LEDs arranged in an LED array, wherein the plurality of LEDs are unpackaged micro LEDs;

a plurality of reflective optical elements arranged in a reflective optical element array; and

a plurality of wavelength converting elements arranged in a wavelength converting array,

wherein each of the plurality of wavelength converting elements is arranged to receive light emitted by one or more of the plurality of LEDs, convert the received light to a different colorband of light, and output the different colorband of light for display,

wherein each of the plurality of reflective optical elements is arranged to redirect at least a portion of light emitted by one or more of the plurality of LEDs towards one or more of the plurality of wavelength converting elements.

2. The color display device of claim 1, wherein each of the plurality of wavelength converting elements is spaced apart from the one or more LEDs, the wavelength converting elements being arranged to receive light from the one or more LEDs.

3. A colour display device according to claim 1 or 2, wherein the LEDs are arranged to emit light in a direction opposite to the direction in which the wavelength converting element outputs light for display.

4. The color display device according to claim 1 or 2, wherein the LED is arranged to emit light in the same direction as the wavelength converting element outputs light for display.

5. The color display device of any one of claims 1 to 4, wherein each reflective optical element comprises a reflective rear surface and reflective walls extending from the reflective rear surface, the reflective rear surface and reflective walls defining a space between the reflective rear surface and the reflective walls.

6. The color display device of claim 5, wherein a transmissive material is disposed in a space defined by the reflective back surface and the reflective walls of each of the reflective optical elements.

7. The color display device of claim 5 or 6, wherein the reflective rear surface of each reflective optical element comprises a reflective light input structure; and is

Wherein each of the plurality of LEDs is aligned with a respective reflective light input structure.

8. The color display device of any one of claims 1 to 7, wherein the light emitted by each of the plurality of LEDs is the same color band.

9. The color display device of claim 8, wherein the colorband of light emitted by each of the plurality of LEDs is blue light.

10. The color display device of claim 8, wherein the colorband of light emitted by each of the plurality of LEDs is ultraviolet light.

11. The color display device of any one of claims 1 to 7, wherein the colorband of light emitted by at least one of the plurality of LEDs is red light and the colorband of light emitted by at least one of the plurality of LEDs is blue or ultraviolet light.

12. A colour display device according to any preceding claim, wherein the wavelength converting element comprises a phosphor or quantum dot material.

13. The color display device of any one of claims 5 to 12, wherein the wavelength converting elements are formed on the reflective rear surface of at least some of the reflective optical elements.

14. A colour display device according to any preceding claim, wherein some of the reflective optical elements are not aligned with a wavelength converting element.

15. A colour display device according to any preceding claim, wherein some of the reflective optical elements are aligned with diffusing regions.

16. The color display device according to any one of claims 6 to 15, wherein the diffusing region and/or wavelength converting element is formed on a surface of the transmissive material.

17. A color display device according to any of the preceding claims, wherein each micro-LED is an LED having a width of at most 150 microns, preferably at most 100 microns and more preferably at most 50 microns.

18. The color display device according to any one of claims 6 to 17, wherein the plurality of LEDs are formed on a surface of the transmissive material.

19. A colour display device according to any preceding claim, further comprising an output substrate.

20. The color display device of claim 19, wherein the wavelength converting element is formed on a first side of the output substrate, and the first side of the output substrate faces the reflective optical element.

21. The color display device of any of the preceding claims, further comprising a color filter array comprising a plurality of absorptive color filter regions arranged in an array.

22. The color display device of claim 21, wherein each of the color filter regions is aligned with only one respective reflective optical element of the array of reflective optical elements.

23. The color display device of claim 21 or 22, wherein the color filter array is formed on the output substrate.

24. The color display device of any one of claims 19-23, wherein each of the plurality of LEDs is formed between a respective optically reflective element and the output substrate.

25. The color display device of any one of claims 19-24, wherein the plurality of LEDs are formed on the output substrate.

26. A color display device according to any one of the preceding claims, further comprising a control system arranged to address the plurality of LEDs with display pixel data to control the plurality of LEDs to emit light in accordance with the display pixel data.

27. The color display device of claim 26, wherein the control system comprises a plurality of addressing electrodes arranged to provide color pixel data to each of the plurality of LEDs.

28. A color display device according to any of the preceding claims, further comprising a plurality of light blocking elements arranged in an array; wherein each light blocking element is aligned with a respective LED of the plurality of LEDs, and the respective aligned LED is arranged between the light blocking element and the reflective optical element.

29. The color display device of claim 28, wherein each light blocking element is reflective.

30. A colour display device according to claim 28 or 29, wherein each light-blocking element is an address electrode.

31. The color display device of any one of claims 19 to 30, wherein the output substrate comprises an optical isolator comprising a linear polarizer and at least one retarder.

32. The color display device of claim 31, wherein the at least one retarder is a quarter-wave plate.

33. A colour display device according to any preceding claim, wherein each LED is aligned with a respective reflective optical element.

34. The color display device of any one of claims 1-32, wherein at least one of the plurality of LEDs is not aligned with a reflective optical element.

35. The color display device of any one of claims 5 to 34, wherein the reflective rear surface of each reflective optical element comprises a white reflector.

36. The color display device of any one of claims 5 to 34, wherein the reflective rear surface of each reflective optical element comprises a metal layer.

37. The color display device of any one of claims 5 to 34, wherein the reflective rear surface of each reflective optical element comprises a flat area.

38. The color display device of any one of claims 5 to 34, wherein the reflective rear surface of each reflective optical element comprises a microstructure.

39. The color display device of any one of claims 5 to 34, wherein the reflective rear surface of each reflective optical element defines a recess.

40. The color display device of claim 39, wherein a wavelength converting element is located within the recess defined by the reflective rear surface of each reflective optical element.

41. The color display device of any one of claims 6 to 40, wherein a surface of the transmissive material has refractive input microstructures.

42. A colour display device according to claim 41, when claim 41 is appended to claim 7, wherein the refractive input microstructure is aligned with the reflective light input structure.

43. The color display device of any one of claims 7-42, wherein the reflective light input structure comprises at least one light deflecting surface in at least one cross-sectional plane;

wherein for each reflective optical element of the array of reflective optical elements, the at least one light deflecting surface is arranged to direct at least some light from at least one LED towards a wavelength converting element.

44. A colour display device according to any one of claims 7 to 43 when any one of claims 7 to 43 is dependent on claim 6, wherein, for each reflective optical element of the array of reflective optical elements, the reflective light input structure is arranged to direct at least some light from at least one LED to be directed between the surface of the transmissive material and the reflective rear surface.

45. The color display device of any one of claims 7-44, wherein the reflective light input structure has at least one curved surface.

46. The color display device of any one of claims 7-45, wherein the reflective light input structure has at least one concave surface.

47. A colour display device according to any preceding claim, wherein a catadioptric optical element is aligned with each reflective optical element.

48. The color display device of claim 47, wherein said catadioptric optical element comprises, in at least one catadioptric cross-sectional plane passing through its optical axis:

a first outer surface and a second outer surface facing the first outer surface;

wherein the first outer surface and the second outer surface comprise curved surfaces;

wherein the first outer surface and the second outer surface extend from a first end of the catadioptric optical element to a second end of the catadioptric optical element, the second end of the catadioptric optical element facing the first end of the catadioptric optical element;

wherein a distance between the first outer surface and the second outer surface at a first end of the catadioptric optical element is smaller than a distance between the first outer surface and the second outer surface at a second end of the catadioptric optical element; and is

At least one transparent inner surface is disposed between the first end and the second end and between the first outer surface and the second outer surface.

Technical Field

The present disclosure relates to a color micro LED display device comprising a plurality of addressable micro LEDs aligned with an array of reflective optical elements and an array of wavelength converting elements. Such a device may be used as a high resolution color display device.

Background

In this specification, "LED" or micro-LED (unless defined by the term "package") refers to an unpackaged LED die extracted directly from a monolithic wafer (i.e., semiconductor element). The micro LEDs may be formed by an array extraction method in which a plurality of LEDs are removed from a monolithic epitaxial wafer in parallel and may be arranged with a positional tolerance of less than 5 microns.

Unlike packaged LEDs. Packaged LEDs have a lead frame and a plastic or ceramic package with solder terminals suitable for standard surface mount PCB (printed circuit board) assembly. The size of the packaged LEDs and the limitations of PCB assembly technology mean that displays formed from packaged LEDs are difficult to assemble at pixel pitches less than 1 mm. The precision of the parts placed by such assembly machines is typically about plus or minus 30 microns. Such dimensions and tolerances prevent application to very high resolution displays.

One type of packaged LED display may provide color pixels emitting in different wavelength bands by means of a packaged LED array. For example, a packaged red LED array, a packaged green LED array, and a packaged blue LED array are soldered to the PCB. Such displays do not use wavelength converting layers or color filters to achieve color. For such displays, the operating voltages of the differently colored packaged LEDs are different from each other, thereby increasing the cost and complexity of the drive electronics. In addition, the emission efficiency of green direct emission is significantly lower than that of red and blue emission, thereby reducing display efficiency and brightness.

Liquid Crystal Displays (LCDs) typically provide color images by means of a white light backlight and a color filter array arranged at each pixel of the transmissive LCD. Organic Led (OLED) displays can provide color output through white light emitted from each pixel and aligned color filters, or through direct emission of red, green, and blue light emitted from different OLED materials at each pixel.

Wavelength conversion materials such as phosphors or quantum dot materials may absorb light in one wavelength band (e.g., blue) and emit light in a different wavelength band (e.g., yellow). There is some blue color transmitted through the phosphor, producing yellow plus blue color, which looks like white.

Catadioptric optical elements combine refractive (refractive) and reflective (reflective) surfaces, which can provide total internal reflection or reflection from a metallized surface. Backlights employing catadioptric optical elements having a small solid angle of output luminous intensity are described in WO 2010038025, which is incorporated herein by reference in its entirety.

Disclosure of Invention

It is desirable to provide thin, flexible and free-form color displays with high brightness and high efficiency.

According to a first aspect of the present disclosure, there is provided a color display device comprising: a plurality of LEDs arranged in an LED array, wherein the plurality of LEDs are unpackaged micro LEDs; a plurality of reflective optical elements arranged in a reflective optical element array; and a plurality of wavelength converting elements arranged in a wavelength converting array, wherein each of the plurality of wavelength converting elements is arranged to receive light emitted by one or more of the plurality of LEDs, convert the received light to a different colorband of light, and output the different colorband of light for display, wherein each of the plurality of reflective optical elements is arranged to redirect at least a portion of the light emitted by one or more of the plurality of LEDs towards one or more of the plurality of wavelength converting elements. Advantageously, emissive displays can be provided with high resolution, high contrast, high efficiency and low power consumption. The display may be thin, flexible, curved, foldable and have a low bezel width. The operating temperature of the wavelength converting material can be reduced, thereby improving efficiency and lifetime. A high color gamut can be provided for the color pixels. Low cross talk between pixels can be achieved to provide high image contrast. The color output of the display may be substantially independent of the viewing angle. Wavelength converting materials with particle sizes similar to the LED size can be used with high output efficiency, so that for example grounded phosphor materials can be used with micro LEDs, while achieving high image resolution.

Each of the plurality of wavelength converting elements may be spaced apart from the one or more LEDs, the wavelength converting elements being arranged to receive light from the one or more LEDs.

The LEDs may be arranged to emit light in a direction opposite to the direction in which the wavelength converting element outputs light for display.

The LEDs may be arranged to emit light in the same direction as the wavelength converting element outputs light for display.

Each reflective optical element may include a reflective back surface and a reflective wall extending from the reflective back surface, the reflective back surface and the reflective wall defining a space therebetween.

The transmissive material may be arranged in a space defined by the reflective rear surface and the reflective walls of each reflective optical element. Advantageously, dimensional stability can be increased and sensitivity to pressure and moisture changes reduced. Advantageously, the reliability and lifetime of the system is improved.

The reflective rear surface of each reflective optical element may include a reflective light input structure. Each of the plurality of LEDs may be aligned with a respective reflective light input structure. Advantageously, light can be efficiently directed from the micro-LEDs to improve efficiency.

The light emitted by each of the plurality of LEDs may have the same color band. Advantageously, the complexity of the micro LED array fabrication may be reduced, thereby reducing costs. Furthermore, the same drive voltage can be used for the micro LED array, thereby reducing the complexity of the control system.

The colorband of light emitted by each of the plurality of LEDs may be blue light.

The colorband of light emitted by each of the plurality of LEDs may be ultraviolet light.

The color band of light emitted by at least one of the plurality of LEDs may be red light and the color band of light emitted by at least one of the plurality of LEDs may be blue or ultraviolet light. Advantageously, the efficiency of the red light output may be increased and fewer wavelength converting elements may be provided, thereby reducing the complexity and cost of the wavelength converting array.

The wavelength converting element may comprise a phosphor or a quantum dot material. Advantageously, known LED material systems such as gallium nitride may be used to provide high efficiency optical output. Other known wavelength conversion materials may be provided, thereby reducing cost and complexity.

The wavelength converting elements may be formed on the reflective rear surface of at least some of the reflective optical elements. Advantageously, the wavelength converting element is remote from the micro-LEDs, thereby reducing operating temperature and increasing efficiency. The area of the wavelength converting element may be larger than the micro-LEDs so that the positional tolerance of the region may be relaxed, thereby reducing costs.

Some of the reflective optical elements may not be aligned with the wavelength converting element. Advantageously, output efficiency is improved. Furthermore, the complexity of the array of wavelength converting elements is reduced, thereby reducing costs.

Some of the reflective optical elements may be aligned with a diffusion region. Advantageously, the colour output may be uniform over the viewing angle.

The diffusing region and/or the wavelength converting element may be formed on a surface of the transmissive material.

Each micro LED may be an LED having a width of at most 150 microns, preferably at most 100 microns, and more preferably at most 50 microns. Advantageously, a high resolution display with high output efficiency may be provided.

A plurality of LEDs may be formed on a surface of the transmissive material. Advantageously, the wavelength converting material may be applied to the surface, which may be flat, by printing or other known deposition methods.

The color display device may further include an output substrate. Advantageously, the light output from the reflective optical element may be further controlled.

The wavelength converting element may be formed on a first side of the output substrate, and the first side of the output substrate may face the reflective optical element. Advantageously, the wavelength converting element can be conveniently aligned with the array of micro LEDs and the array of reflective optical elements, thereby reducing costs. Further, the wavelength converting element can be provided at a reduced cost.

The color display device may further include a color filter array including a plurality of absorptive color filter regions. The plurality of color filter regions may be arranged in an array. Each color filter region may be aligned with only one reflective optical element of the array of reflective optical elements. The color filter array may be formed on the output substrate. Advantageously, the color gamut may be increased.

Each of the plurality of LEDs may be formed between a respective optically reflective element and the output substrate.

A plurality of LEDs may be formed on the output substrate. Advantageously, an output substrate material may be provided that is resistant to the processing conditions of the micro LED array assembly. Higher temperatures can be provided for the micro LED assembly, advantageously improving reliability and efficiency. The entire array of micro-LEDs can be aligned to the entire array of reflective optical elements in a single alignment step, advantageously reducing costs.

The color display device may further comprise a control system arranged to address the plurality of LEDs with the display pixel data to control the plurality of LEDs to emit light in dependence on the display pixel data.

The control system may comprise a plurality of addressing electrodes arranged to provide color pixel data to each of the plurality of LEDs. Advantageously, a color image may be provided.

The color display device may further comprise a plurality of light blocking elements arranged in an array. Each light blocking element may be aligned with a respective LED of the plurality of LEDs. The respective aligned LEDs may be arranged between the light blocking element and the reflective optical element. Advantageously, the color gamut may be increased by preventing unwanted light from propagating directly from the aligned micro LEDs.

Each light blocking element may be reflective. Advantageously, light from the micro-LEDs can be efficiently directed into the reflective optical element. Each light blocking element may be an address electrode. Advantageously, cost and complexity may be reduced.

The output substrate may include an optical isolator including a linear polarizer and at least one retarder. The at least one retarder may be a quarter-wave plate. Advantageously, undesirable reflection of ambient light from the reflective interior surface may be reduced, thereby increasing display contrast.

Each LED may be aligned with a respective reflective optical element.

At least one of the plurality of LEDs may not be aligned with the reflective optical element. Advantageously, the complexity of the array of reflective optical elements may be reduced.

The reflective rear surface of each reflective optical element may comprise a white reflector. Advantageously, a wide-angle output may be provided. The number of manufacturing steps may be reduced, advantageously reducing cost and complexity.

The reflective rear surface of each reflective optical element may comprise a metal layer. Advantageously, the output efficiency of incident light can be improved.

The reflective rear surface of each reflective optical element may comprise a planar region. Advantageously, the light may be redirected within the reflective optical element, thereby increasing the uniformity of the illumination passing through the reflective optical element.

The reflective rear surface of each reflective optical element may comprise microstructures. Advantageously, the output light may be scattered to provide a wide-angle luminance distribution.

The reflective rear surface of each reflective optical element may define an aperture. The wavelength converting element may be located within a recess defined by the reflective rear surface of each reflective optical element. Advantageously, the wavelength converting material may be conveniently formed on the rear reflective surface. In contrast, when the phosphor is applied directly to the LED, the particles of the phosphor should be smaller than the LED. Larger wavelength converting particles than micro LEDs may be provided in the recess with high output color uniformity. Advantageously, larger wavelength converting particles may be cheaper than smaller wavelength converting particles.

The surface of the transmissive material may include refractive input microstructures. The refractive input microstructures may be aligned with the reflective light input structures. Advantageously, light can be efficiently directed from the micro-LEDs to the reflective rear surface.

In at least one cross-section, the reflective light input structure may comprise at least one light deflecting surface. For each reflective optical element of the array of reflective optical elements, the at least one light deflecting surface may be arranged to direct at least some light from the at least one LED towards the wavelength converting element. The reflective light input structure may comprise at least one curved surface. The reflective light input structure may comprise at least one concave surface. Advantageously, light can be efficiently coupled from the micro-LEDs to the output of the reflective optical element, thereby increasing efficiency and reducing power consumption.

For each reflective optical element of the array of reflective optical elements, the reflective optical input structure may be arranged to direct at least some light from the at least one LED to be directed between the surface of the transmissive material and the reflective rear surface. Advantageously, the light can be redistributed within the reflective optical element, thereby increasing the uniformity of the output.

A catadioptric optical element may be aligned with each reflective optical element. The catadioptric optical element may comprise, in at least one catadioptric cross-section through its optical axis: a first outer surface and a second outer surface facing the first outer surface. The first outer surface and the second outer surface may comprise curved surfaces. The first outer surface and the second outer surface may extend from a first end of the catadioptric optical element to a second end of the catadioptric optical element, the second end of the catadioptric optical element facing the first end of the catadioptric optical element. The distance between the first and second outer surfaces of the first end of the catadioptric optical element may be smaller than the distance between the first and second outer surfaces of the second end of the catadioptric optical element. At least one transparent inner surface may be disposed between the first end and the second end and between the first outer surface and the second outer surface. Advantageously, a directional display may be provided. A private display operation may be implemented such that switching between narrow and wide angle modes of operation is possible. Further power consumption can be reduced in the frontal direction for the viewer. For off-axis viewing positions, other stray light may be reduced, providing low display leakage for nighttime operation.

According to a second aspect of the present disclosure, there is provided a color display device comprising: a plurality of LEDs arranged in an LED array, wherein LEDs of the plurality of LEDs are micro LEDs; and a control system arranged to address the plurality of LEDs with display pixel data to provide input light; an array of reflective optical elements comprising a plurality of reflective optical elements arranged in an array; wherein each reflective optical element of the array of reflective optical elements comprises: (i) a reflective rear surface; (ii) a reflective wall extending away from the reflective rear surface; (iii) a light transmissive opening disposed between the reflective walls and facing the reflective rear surface, wherein each reflective optical element is aligned corresponding to a respective one or more of the plurality of LEDs, and the LEDs of the plurality of LEDs aligned with the reflective optical elements are aligned with only a respective one of the reflective optical elements; a wavelength conversion array comprising a plurality of wavelength converting elements arranged in an array, wherein each of the wavelength converting elements is aligned with only a respective one of the reflective optical elements; wherein input light from the respective aligned at least one LED is input through at least one light input area of the light transmissive opening and, upon incidence on at least one of the reflective rear surface and the respective aligned wavelength converting element, is output through at least one light output area different from the light input area of the light transmissive opening. Advantageously, emissive displays can be provided with high resolution, high contrast, high efficiency and low power consumption. The display may be thin, flexible, curved, foldable and have a low bezel width. The operating temperature of the wavelength converting material can be reduced, thereby improving efficiency and lifetime. A high color gamut can be provided for the color pixels. Low cross talk between pixels can be achieved to provide high image contrast. The color output of the display may be substantially independent of the viewing angle. Wavelength converting materials with particle sizes similar to the LED size can be used with high output efficiency, so that for example grounded phosphor materials can be used with micro LEDs, while achieving high image resolution.

The transmissive material may be arranged between the reflective back surface, the reflective walls and the light transmissive opening, and the light transmissive opening comprises the transmissive front surface. Advantageously, dimensional stability can be increased and sensitivity to pressure and moisture changes reduced. Advantageously, the reliability and lifetime of the system is improved.

The reflective rear surface may include a reflective light input structure; the reflective surface may comprise reflected light. Wherein an LED of the plurality of LEDs aligned with the reflective optical element may be aligned with the reflective light input structure. Advantageously, light can be efficiently directed from the micro-LEDs to improve efficiency.

The input light from each of the plurality of LEDs may be in the same color band. Advantageously, the complexity of the micro LED array fabrication may be reduced, thereby reducing costs. Furthermore, the same drive voltage can be used for the micro LED array, thereby reducing the complexity of the control system.

The input light color band may be blue light or may be ultraviolet light. Each wavelength converting element may be arranged to convert an input light colorband into a different colorband of visible light. The wavelength converting element may comprise a phosphor or a quantum dot material. Advantageously, known LED material systems such as gallium nitride may be used to provide high efficiency optical output. Other known wavelength conversion materials may be provided, thereby reducing cost and complexity.

The input light colorband from some of the plurality of LEDs may be red light and the input light colorband from some of the plurality of LEDs may be blue or ultraviolet light. Advantageously, the efficiency of the red light output may be increased and fewer wavelength converting elements may be provided, thereby reducing the complexity and cost of the wavelength converting array.

The wavelength converting elements may be formed on the reflective rear surface of at least some of the reflective optical elements. Advantageously, the wavelength converting element is remote from the micro-LEDs, thereby reducing operating temperature and increasing efficiency. The area of the wavelength converting element may be larger than the micro-LEDs so that the positional tolerance of the region may be relaxed, thereby reducing costs.

Some of the reflective optical elements may not be aligned with the wavelength converting element. Advantageously, output efficiency is improved. Furthermore, the complexity of the array of wavelength converting elements is reduced, thereby reducing costs.

Some of the reflective optical elements may be aligned with a diffusion region. Advantageously, the colour output may be uniform over the viewing angle.

The diffusing region and/or the wavelength converting element may be formed on an output region of the transmissive front surface. Advantageously, the wavelength converting material may be applied to the surface, which may be flat, by printing or other known deposition methods.

Each micro LED may be an LED having a width of at most 150 microns, preferably at most 100 microns, and more preferably at most 50 microns. Advantageously, a high resolution display with high output efficiency may be provided.

The color display device may further include an output substrate. Advantageously, the light output from the reflective optical element may be further controlled.

The wavelength converting element may be formed on a first side of the output substrate, and the first side of the output substrate may face the light transmissive opening of the reflective optical element. Advantageously, the wavelength converting element can be conveniently aligned with the array of micro LEDs and the array of reflective optical elements, thereby reducing costs. Further, the wavelength converting element can be provided at a reduced cost.

The color display device may further include a color filter array including a plurality of absorptive color filter regions arranged in an array. Each of the color filter regions may be aligned corresponding to a light output region of the light transmissive opening of only one of the respective reflective optical elements of the array of reflective optical elements. The color filter array may be formed on the output substrate. Advantageously, the color gamut may be increased.

A plurality of LEDs may be formed between the transmissive front surface and the output substrate. A plurality of LEDs are formed on the transmissive front surface. Advantageously, the complexity of the output substrate may be reduced, thereby reducing costs. A plurality of LEDs may be formed on the output substrate. An output substrate material that is resistant to the processing conditions of the micro LED array assembly may be provided. Higher temperatures can be provided for the micro LED assembly, advantageously improving reliability and efficiency. The entire array of micro-LEDs can be aligned to the entire array of reflective optical elements in a single alignment step, advantageously reducing costs.

The control system may comprise a plurality of addressing electrodes arranged to provide color pixel data to each of the plurality of LEDs. Advantageously, a color image may be provided.

The color display device may further include a plurality of light blocking elements arranged in an array; wherein each of the light blocking elements is aligned corresponding to an LED of the plurality of LEDs, and the respective aligned LEDs are arranged between the light blocking elements and the reflective optical element of each light blocking element. Advantageously, the color gamut may be increased by preventing unwanted light from propagating directly from the aligned micro LEDs.

Each light blocking element may be reflective. Advantageously, light from the micro-LEDs can be efficiently directed into the reflective optical element. Each light blocking element may comprise an address electrode. Advantageously, cost and complexity may be reduced.

The output substrate may include an optical isolator including a linear polarizer and at least one retarder. The at least one retarder may be a quarter-wave plate. Advantageously, undesirable reflection of ambient light from the reflective interior surface may be reduced, thereby increasing display contrast.

Some of the plurality of LEDs may not be aligned with the reflective optical element. Advantageously, the complexity of the array of reflective optical elements may be reduced.

The reflective rear surface may comprise a white reflector. Advantageously, a wide-angle output may be provided. The number of manufacturing steps may be reduced, advantageously reducing cost and complexity.

The reflective rear surface may comprise a metal layer. Advantageously, the output efficiency of incident light can be improved.

The reflective rear surface may comprise a planar area. Advantageously, the light may be redirected within the reflective optical element, thereby increasing the uniformity of the illumination passing through the reflective optical element. The reflective rear surface may comprise microstructures. Advantageously, the output light may be scattered to provide a wide-angle luminance distribution.

The reflective rear surface may comprise a recess or a recess. The recess may comprise a wavelength converting element. Advantageously, the wavelength converting material may be conveniently formed on the rear reflective surface. In contrast, when the phosphor is applied directly to the LED, the particles of the phosphor should be smaller than the LED. Larger wavelength converting particles than micro LEDs may be provided in the recess with high output color uniformity. Advantageously, larger wavelength converting particles may be cheaper than smaller wavelength converting particles.

The light input region of the transmissive front surface may include refractive input microstructures. The refractive input microstructures may be aligned with the reflective light input structures. Advantageously, light can be efficiently directed from the micro-LEDs to the reflective rear surface.

The reflective light input structure may comprise at least one light deflecting surface in at least one cross-sectional plane through its optical axis; wherein for each reflective optical element of the array of reflective optical elements, the at least one light deflecting surface may be arranged to direct at least some light from the respective aligned at least one LED towards the at least one light transmissive open output area. The reflective light input structure may comprise at least one curved surface. The reflective light input structure may comprise at least one concave surface. Advantageously, light can be efficiently coupled from the micro-LEDs to the output of the reflective optical element, thereby increasing efficiency and reducing power consumption.

For each reflective optical element of the array of reflective optical elements, the reflective optical input structure may be arranged to direct at least some light from the respective aligned at least one LED to be directed between the transmissive front surface and the reflective back surface. Advantageously, the light can be redistributed within the reflective optical element, thereby increasing the uniformity of the output.

The catadioptric optical element may be aligned with an output region of each reflective optical element. The catadioptric optical element may comprise, in at least one catadioptric cross-sectional plane passing through its optical axis: a first outer surface and a second outer surface facing the first outer surface; wherein the first outer surface and the second outer surface comprise curved surfaces; wherein the first outer surface and the second outer surface extend from a first end of the catadioptric optical element to a second end of the catadioptric optical element, the second end of the catadioptric optical element facing the first end of the catadioptric optical element; wherein a distance between the first outer surface and the second outer surface at the first end of the catadioptric optical element is smaller than a distance between the first outer surface and the second outer surface at the second end of the catadioptric optical element; and at least one transparent inner surface is disposed between the first end and the second end and between the first outer surface and the second outer surface. Advantageously, a directional display may be provided. A private display operation may be implemented such that switching between narrow and wide angle modes of operation is possible. Further power consumption can be reduced in the frontal direction for the viewer. For off-axis viewing positions, other stray light may be reduced, providing low display leakage for nighttime operation.

Such devices may be used for color displays and directional displays.

These and other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art upon reading the entirety of the present disclosure.

Drawings

Embodiments are illustrated by way of example in the figures of the accompanying drawings in which like references indicate similar elements.

FIG. 1 is a schematic diagram showing, in side perspective view, a color display device comprising an array of micro LEDs, an array of wavelength converting elements and an array of reflective optical elements, wherein the micro LEDs are arranged on the reflective optical elements;

FIG. 2A is a schematic diagram showing, in side perspective view, a reflective optical element and aligned micro LEDs arranged to provide pixel illumination, wherein the reflective optical element includes a diffusely reflective surface;

FIG. 2B is a schematic diagram showing a reflective optical element, a micro LED and a light blocking element in side view;

FIG. 2C is a schematic diagram showing the reflective optical element, micro-LED and light blocking element in front view;

FIG. 3A is a schematic diagram showing, in side view, the operation of a reflective optical element, a micro LED and an aligned wavelength converting element, with the output substrate separated from the reflective optical element;

FIG. 3B is a schematic diagram showing the alignment of a reflective optical element, a micro LED, and an output wavelength converting element in a front view, wherein the reflective optical element is aligned with each micro LED in the array of micro LEDs;

3C-3D are schematic diagrams illustrating the arrangement of wavelength converting elements and diffusing regions in front view;

FIG. 4 is a schematic diagram illustrating operation of a reflective optical element, a micro LED and an aligned wavelength converting element in a side view, wherein a transmissive material is provided between the output substrate and the reflective optical element;

FIG. 5A is a schematic diagram showing, in side perspective view, a color display device comprising an array of micro-LEDs, an array of wavelength converting elements, and an array of reflective optical elements, wherein the micro-LEDs are arranged on an output substrate;

FIG. 5B is a schematic diagram showing, in side perspective view, a reflective optical element including a wavelength converting element disposed on a reflective surface and an aligned micro LED arranged to provide pixel illumination;

FIG. 6A is a schematic diagram showing, in side view, a reflective optical element including a wavelength converting element disposed on a reflective surface, a micro LED, and an aligned wavelength converting element;

FIG. 6B is a schematic diagram showing, in side view, a reflective optical element, micro-LEDs and an aligned wavelength converting element, wherein the micro-LEDs are provided on a transmissive material disposed between a reflective back surface and a transmissive front surface;

fig. 6C to 6D are schematic diagrams showing the arrangement of color filters for a color display device in a front view;

FIG. 6E is a schematic diagram showing, in front view, the alignment of the reflective optical elements, the micro LEDs, and the wavelength conversion element arranged on the reflective surfaces of some of the reflective optical elements, wherein the reflective optical elements are aligned with each of the micro LEDs in the array of micro LEDs, and the micro LEDs are arranged to output the same color of light on the array of micro LEDs;

FIG. 7A is a schematic diagram showing, in front view, the alignment of a reflective optical element, a micro-LED, and a wavelength conversion element arranged on the reflective surface of at least some of the reflective optical elements, wherein the reflective optical element is aligned with each micro-LED in an array of micro-LEDs, and the micro-LEDs are arranged to output the same color of light on the array of micro-LEDs, wherein the area of the micro-LEDs varies according to the output wavelengths of the light emitting element and the aligned wavelength conversion element;

FIG. 7B is a schematic diagram showing, in front view, the alignment of a reflective optical element, micro-LEDs, and a wavelength conversion element arranged on the reflective surface of the reflective optical element, wherein the reflective optical element is aligned with some of the micro-LEDs in the array of micro-LEDs, and the micro-LEDs are arranged to output the same color of light on the array of micro-LEDs;

fig. 7C is a schematic diagram showing, in front view, alignment of reflective optical elements, micro-LEDs, and wavelength conversion elements arranged on reflective surfaces of some of the reflective optical elements, wherein the reflective optical elements are aligned with each of the micro-LEDs in the array of micro-LEDs, and the micro-LEDs are arranged to output different colors of light on the array of micro-LEDs.

FIG. 7D is a schematic diagram showing, in front view, the alignment of a reflective optical element, micro-LEDs, and a wavelength conversion element arranged on the reflective surface of the reflective optical element, where the reflective optical element is aligned with some of the micro-LEDs in the array of micro-LEDs, and the micro-LEDs are arranged to output different colors of light on the array of micro-LEDs;

FIG. 7E is a schematic diagram showing, in front view, alignment of reflective optical elements, micro-LEDs, and wavelength conversion elements arranged on reflective surfaces of some of the reflective optical elements, wherein each of the first plurality of reflective optical elements is aligned with a red-emitting micro-LED and a blue-emitting micro-LED, and further includes a light-diffusing region; and each of the second plurality of reflective optical elements is aligned with a micro LED that emits blue light and further includes a green wavelength converting element;

fig. 7F is a schematic diagram showing, in front view, alignment of reflective optical elements aligned with each micro-LED in the array of micro-LEDs, the micro-LEDs, and a wavelength conversion element arranged on a reflective surface of some of the reflective optical elements, and the micro-LEDs arranged to output ultraviolet light;

FIG. 8A is a schematic diagram showing another structure of a reflective optical element, aligned micro-LEDs and aligned wavelength converting elements in a side view, wherein the aligned micro-LEDs are arranged on an opaque support substrate;

FIG. 8B is a schematic diagram showing another configuration of a reflective optical element, aligned micro-LEDs and aligned wavelength converting elements in a side view, wherein a portion of the aligned micro-LEDs and reflective optical element are disposed on an opaque support substrate;

FIG. 9A is a schematic diagram showing another configuration of a reflective optical element, aligned micro-LEDs and aligned wavelength converting elements in a side view;

FIG. 9B is a schematic diagram showing in front view the reflective optical element, micro LEDs, and alignment arranged to provide an incremental pixel pattern;

FIG. 10A is a schematic diagram showing, in side view, a reflective optical element, a micro LED, and an aligned wavelength converting element, wherein the wavelength converting material comprises a large grain size material;

FIG. 10B is a schematic diagram showing, in top view, operation of a reflective optical element, a micro LED, and an aligned wavelength converting element, wherein the wavelength converting material comprises a large grain size material;

FIG. 10C is a schematic diagram showing, in side view, a reflective optical element, a micro-LED and an aligned wavelength converting element, wherein the wavelength converting material comprises a large grain size material, and wherein the micro-LED is disposed on a transmissive material disposed between a reflective back surface and a transmissive front surface;

FIG. 11A is a schematic diagram showing an array of reflective optical elements and an aligned micro LED array in a front view, wherein the width of the output of the reflective optical element transparent output region is reduced;

FIG. 11B is a schematic diagram showing, in top view, an array of reflective optical elements and an aligned micro LED array, wherein the width of the output of the reflective optical element transparent output region is reduced and arranged in alignment with the array of collimating catadioptric optical elements;

FIG. 11C is a schematic diagram of the directional display showing the primary user and the off-axis snooper in a top view;

FIG. 11D is a schematic diagram showing, in top view, an array of reflective optical elements and an aligned micro LED array aligned with an array of collimating catadioptric optical elements and an array of linear waveguides to provide a switchable privacy display;

FIG. 11E is a schematic diagram illustrating the structure and operation of a catadioptric optical element and an aligned reflective optical element in top view;

12A-12C are schematic diagrams illustrating an addressing system for a plurality of LEDs;

FIG. 13A is a schematic diagram showing, in side view, the luminous intensity emission distribution from a macroscopic LED;

fig. 13B is a schematic diagram showing a luminous intensity emission distribution from the micro LED in a side view.

FIG. 14 is a schematic diagram showing in side view the change in optical path length through a wavelength conversion coating for light from a micro LED;

FIG. 15A is a schematic diagram showing, in side view, output from a micro LED including a wavelength converting coating having a large particle size;

FIG. 15B is a schematic diagram showing output from a micro LED including a wavelength converting coating having a large particle size in a front view;

16A-16G are schematic diagrams illustrating a method of forming an array of reflective optical elements and an aligned array of micro LEDs in a side view; and

17A-17F are schematic diagrams illustrating in side view a method of forming an array of reflective optical elements and an aligned array of micro LEDs according to the present disclosure.

Detailed Description

It is desirable to provide a miniature LED color display device as a spatial light modulator that is addressed with color pixel information and achieves high luminous efficiency, color fidelity, and color uniformity over a wide range of viewing angles. Furthermore, it is desirable to provide illumination of wavelength conversion materials in a manner that minimizes performance changes over time and protects such materials from environmental degradation.

The structure and operation of various switchable display devices will now be described. In the present specification, common elements have common reference numerals. It is noted that the disclosure in relation to any element applies to each device in which the same or corresponding element is provided. Accordingly, for the sake of brevity, such disclosure is not repeated.

A color display device comprising an array of micro LEDs 3 and an array of wavelength converting elements 120 will now be described.

Fig. 1 is a schematic diagram showing in a side perspective view a color display device 100 comprising an array of micro-LEDs 3, an array 120 of wavelength converting elements 20R, 20G and an array 103 of reflective optical elements 102, wherein the micro-LEDs 3 are arranged on the reflective optical elements 102; FIG. 2A is a schematic diagram showing, in side perspective view, the reflective optical element 102 and the aligned micro LEDs 3 of FIG. 1 arranged to provide pixel illumination, wherein the reflective optical element 102 includes diffusely reflective surfaces 23a, 23 b; fig. 2B is a schematic diagram showing the reflective optical element, the micro-LEDs 3 and the light blocking element 5 in a side view; and fig. 2C is a schematic diagram showing the reflective optical element 102, the micro-LEDs 3, and the light blocking element 5 in a front view.

Fig. 1 shows a color display device 100 comprising a plurality of LEDs arranged in an LED array, wherein an LED of the plurality of LEDs is a micro LED 3.

The micro LEDs 3 are unpackaged micro LEDs, that is, they are semiconductor dies that are extracted directly from a monolithic wafer (i.e., semiconductor element). Unpackaged micro-LEDs may be formed by an array extraction method in which multiple LEDs are removed from a monolithic epitaxial wafer in parallel and may be arranged with a positional tolerance of less than 5 microns. Unlike packaged LEDs. Packaged LEDs have a lead frame and a plastic or ceramic package with solder terminals suitable for standard surface mount PCB (printed circuit board) assembly. The size of the packaged LEDs and the limitations of PCB assembly technology mean that displays formed from packaged LEDs are difficult to assemble at pixel pitches less than 1 mm. The precision of the parts placed by such assembly machines is typically about plus or minus 30 microns. Such dimensions and tolerances prevent application to very high resolution displays.

The array of reflective optical elements 103 may be formed in one piece such that the array 103 of reflective optical elements 102 provides a substrate on which the micro-LEDs 3 are formed. In the embodiment of fig. 1-2C, the micro-LEDs 3 are in a micro-LED array, which is formed on an integrated body with a reflector array. In other embodiments described below, the micro-LEDs may be formed on a separate substrate aligned with the array 103 of reflective optical elements 102. The micro LEDs 3 may be transferred to the array of reflective optical elements 103 by a parallel transfer method as described below. Thus, the alignment between the micro-LEDs 3 and the array of reflective optical elements 103 can be achieved in a single step or a small number of steps, as opposed to aligning each individual reflector with each individual micro-LED. The positions of the micro LEDs 3 and the reflective optical element 102 may be defined or formed with lithographic accuracy so that array alignment may be achieved with high accuracy. Advantageously, uniformity is increased and alignment time and cost are reduced. The wavelength converting material may be provided with a lower accuracy than the wavelength converting material provided for the micro-LEDs and the reflective optical element. Advantageously, a less costly method may be provided for forming the array 120 of wavelength converting elements 20.

The color display device thus comprises: a plurality of LEDs, which are unpackaged LEDs, arranged in an LED array, wherein the plurality of LEDs are micro LEDs 3; a plurality of reflective optical elements 102 arranged in an array of reflective optical elements 103; and a plurality of wavelength converting elements 20 arranged in a wavelength converting array 120, wherein each of the plurality of wavelength converting elements 20 is arranged to receive light emitted by one or more LEDs 3 of the plurality of LEDs, convert the received light to light of a different colorband, and output light of the different colorband, wherein each of the plurality of reflective optical elements 102 is arranged to redirect at least a portion of the light emitted by one or more LEDs 3 of the plurality of LEDs towards one or more of the plurality of wavelength converting elements 20. Each of the plurality of wavelength converting elements 20 is spaced apart from one or more LEDs 3, the wavelength converting elements 20 being arranged to receive light from the one or more LEDs.

In large television applications, the color sub-pixel pitch is typically about 200x 600 microns, and for an RGB stripe pixel arrangement, the color pixel pitch is 600x 600 microns. A micro LED3 size of about 100 microns or less may typically be provided for each color sub-pixel. In mobile displays, such as those used for cellular telephone applications, the color sub-pixel pitch may typically be on the order of 20 x 60 microns. For such pixels, a micro LED3 size of 10 microns or less may be provided. In the present disclosure, the micro-LEDs 3 are LEDs having a width or diameter of at most 150 microns, preferably at most 100 microns and more preferably at most 50 microns. The micro LEDs 3 in the micro LED array may be square, rectangular or other shapes, such as circular.

The control system is arranged to address the plurality of micro LEDs 3 with display pixel data to provide input light and comprises a plurality of address electrodes 210, 212 arranged to provide color pixel data to each micro LED3 of the plurality of micro LEDs 3. The control system further comprises row and column electrode drivers 202, 204 and a controller 200 arranged to provide image data to the drivers 202, 204. The control system may also include additional circuitry including, but not limited to, thin film transistors, capacitors, ICs, or transistors located within the array of micro LEDs 3 and adjacent to the micro LEDs 3.

In the present embodiment, the area of the micro LEDs 3 may be substantially smaller than the total pixel area defined by the pixel pitch. Other electronics, for example for touch sensing, may be provided between the micro LEDs 3. The controller 200 may also be arranged to process and sense measurement data from a touch sensor (not shown).

The reflective optical element array 103 comprises a plurality of reflective optical elements 102, the plurality of reflective optical elements 102 being arranged in an array. The reflective optical element may be formed in or on the optical body 47. The transmissive material 40 may be disposed between the reflective back surface 43 and the transmissive front surface 33.

The color display device 100 further comprises an output substrate 52 which is transmissive and arranged to receive light from the array of reflective optical elements 103. A plurality of micro-LEDs 3 are formed between the transmissive front surface 33 and the output substrate 52.

As further shown in fig. 2A-2C, each reflective optical element 102 in the array of reflective optical elements 103 includes: (i) a reflective rear surface 43; (ii) a reflective wall 49 extending away from the reflective rear surface 43; and (iii) a light transmissive opening 133 disposed between the reflective walls 49 and facing the reflective rear surface 43.

The transmissive material 40 is arranged between the reflective back surface 43, the reflective walls 49 and the light transmissive opening 133, and the light transmissive opening comprises the transmissive front surface 33.

The reflective rear surface 43 further comprises a reflective light input structure 44; wherein the micro-LEDs 3 of the plurality of LEDs aligned with the reflective optical element 102 are aligned with the reflective light input structure 44, for example, by an optical axis 111 that is centered between the reflective optical element 102 and the micro-LEDs 3.

In other words, each reflective optical element 102 of the reflective optical element array 103 includes: (i) a transmissive front surface 33 comprising a light input area 35 and at least one light output area 37a, 37 b; (ii) a reflective rear surface 43 facing the transmissive front surface 33, the reflective rear surface comprising a reflective light input structure 44, wherein the reflective light input structure 44 is aligned with the light input region 35; (iii) a reflective wall 49 extending between the reflective rear surface 43 and the transmissive front surface 33. The walls 49 of adjacent optical elements 102 are spaced apart by the upper surface 45 of the body 47.

As shown in fig. 2C, adjacent reflective optical elements 102a, 102b, 102C may be provided with individually addressed micro LEDs 3a, b, 3C. Thus, the reflective optical elements 102a, 102b, 102c can be addressed with red, green and blue pixel data, respectively. Further reflective optical elements 102 (not shown) may be further provided that are addressed with other colors of data, such as yellow and white.

Each reflective optical element 102 is aligned corresponding to a respective one or more micro-LEDs 3 of the plurality of micro-LEDs, the micro-LEDs 3 of the plurality of micro-LEDs aligned with the reflective optical element 102 being aligned with only a respective one of the reflective optical elements 102.

The light input region 35 of each reflective optical element 102 is aligned corresponding to a respective one or more micro LEDs 3a, 3b, 3c of the plurality of micro LEDs 3, each micro LED3 of the plurality of micro LEDs 3 aligned with a reflective optical element 102a, 102b, 102c being aligned with only a respective one of the reflective optical elements 102a, 102b, 102 c.

The color display device 100 further comprises a plurality of light-blocking elements 5, the plurality of light-blocking elements 5 being arranged in an array. Each of the light blocking elements 5 is aligned corresponding to a micro LED3 of the plurality of micro LEDs 3, and for each light blocking element 5 the respective aligned micro LED3 is arranged between the light blocking element 5 and the reflective optical element 102. The light-blocking element may also be used as a component such as an electrode or a capacitor plate in the addressing of the micro-LEDs 3.

In operation, the micro-LEDs 3 are arranged to input light rays 110 through the light input region 35 of the transmissive front surface 33. The light blocking element 5 may be reflective and may be arranged to block or reflect light rays from the micro LEDs 3 that would otherwise be directed away from the light input region 35. In other words, the light output from the micro LEDs 3 is directed away from the output direction of the display 100.

Each light-blocking element 5 may also be an address electrode, for example connected to the electrode 210. The light blocking element 5 may provide a large area of attachment electrodes for the micro-LEDs, advantageously enabling convenient tolerances for mounting of the micro-LEDs 3 and connection to the addressing electrodes 210 or 212.

The reflective rear surface 43 and the reflective walls 49 may comprise a reflective coating 41 which may be a metallic coating or a white reflective coating. Alternatively, the material of the optical body 47 may be a white material, such as a CEL-W epoxy material sold by Hitachi Chemical, so that the reflective coating 41 may be omitted, advantageously reducing cost and manufacturing complexity.

As shown in fig. 2B, the reflective back surface 43 may further comprise microstructures in the light diffusing region 23, including surface relief structures 46, and the reflective back surface may further comprise planar regions 48.

In at least one cross-sectional plane, the reflected light input structure 44 comprises a first light deflecting surface 64a and a second light deflecting surface 64b, wherein the first and second light deflecting surfaces 64a, 64b are arranged to be directed towards the first and second areas of the reflective optical element 102.

In operation, some of the input light rays 110 from the micro LEDs 3 are incident on the reflective light input structure 44 and are deflected so as to be incident on the light diffusing regions 23a, 23b, as will be described further below.

Input light rays 110 that are not incident on the input structure 44 are directly incident on the light diffusing regions 23a, 23b of the reflective rear surface 43.

Light rays 110 incident on the microstructures 46 of the light diffusing regions 23a, 23b of the reflective back surface 43 are diffused as output light such that light rays 112 are transmitted through the light output regions 37a, 37b of the transmissive front surface 33. As will be described below, some of the light rays 113 may be directed within the reflective optical element 113. Further, some of the light rays 114 may be reflected by the diffusing or planar reflective walls 49.

The light blocking layer 5 prevents light output from the input region 35 that transmits the front surface, and the input structure 44 efficiently guides input light onto the light diffusion regions 23a, 23 b. Advantageously, the output areas 37a, 37b of the transmissive front surface 33 are effectively filled with light from the micro LEDs.

Light from the micro-LEDs 3b is confined within a single reflective optical element 102b before being output to the transmissive front surface 33 output area 35. The light output from each reflective optical element 102b is optically separated from the adjacent elements 102a, 102 c. Advantageously, cross-talk between adjacent optical outputs is reduced and a high contrast ratio can be achieved.

The light propagation in the display device 100 will now be further described.

Fig. 3A is a schematic diagram showing the reflective optical element 102, micro-LEDs 3, and aligned wavelength conversion array 120 in a side view with the output substrate 52 separated from the reflective optical element 102.

The gap 50 is disposed between the reflective optical element 102 and the output substrate 52.

The light output from the micro-LEDs 3 is typically Lambertian, that is, the highest luminous intensity output is in the normal direction (parallel to the z-direction).

The reflective light input structure 44 includes a curved surface as a concave surface. In operation, light rays emitted from the micro LEDs in the normal direction are directed to the light diffusion region 23 without being directed toward the micro LEDs 3 and the light blocking element 5. By comparison, when the reflective light input structure 44 is planar, then light will be reflected back towards the micro-LEDs 3 and the light blocking elements 5. Advantageously, the reflective light input structure 44 increases the display light output efficiency.

For each reflective optical element 102 of the array of reflective optical elements 103, the reflective optical input structure 44 is arranged to direct at least some light rays 110 from the respective aligned at least one micro LED3 as light rays 116 between the transmissive front surface 33 and the reflective back surface 43 in the transmissive material 40 between transmitted light. Planar regions 48 on the reflective rear surface 43 between the microstructure 48 elements provide for the direction of light from the reflective rear surface 43. The light rays 110 are distributed over the light diffusion regions 23a, 23 b. Advantageously, this light distribution in the reflective optical element 102 reduces the peak energy density of the light at the wavelength converting element and achieves higher efficiency and longer lifetime, as will be described further below.

Fig. 3A further illustrates the propagation of light in the output substrate 52. The wavelength conversion array 120 is arranged on the input side of the transparent support substrate 53. Light rays 112 from the output area 37 of the transmissive front surface 33 of the reflective optical element 102 are incident on the wavelength converting elements of the array 120a and are wavelength converted at the wavelength conversion location 24. An optical isolator comprising a retarder 54 and a polarizer 56 is arranged on the output side of the transparent support substrate 53, the operation of which will be described further below.

The output substrate 52 includes an optical isolator comprising a linear polarizer and at least one retarder. At least one retarder is a quarter-wave plate.

The upper surface 45 of the body 47 may be further provided with a coating 145. The coating may be provided in the same step as the reflective coating 41 is provided, thereby advantageously reducing costs. The optical isolator eliminates visibility of reflections from surface 45. Alternatively, an absorptive coating 145 may be provided on the upper surface 45 of the body 47. The array 120 of wavelength converting elements 20 may further be provided with an absorption mask 25. Advantageously, stray light from the reflective optical element can be prevented from propagating between adjacent reflective optical elements, thereby improving crosstalk.

It may be assumed that features of the arrangement of fig. 3A that are not discussed in further detail correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 3B is a schematic diagram showing, in front view, the alignment of the reflective optical element 102, the micro-LEDs 3, and the output wavelength converting elements 20R, 20G and diffuser element 21 of fig. 1, with the reflective optical element 102 aligned with each micro-LED 3 in the array of micro-LEDs 3.

The wavelength converting array 120 comprises a plurality of wavelength converting elements 20R, 20G, the plurality of wavelength converting elements 2R, 20G being arranged in an array, wherein each of the wavelength converting elements 20R, 20G is aligned with only a respective one of the reflective optical elements 102. Each of the wavelength converting elements 20R, 20G is aligned correspondingly to the light output region 37 of the transmissive front surface 33 of the respective reflective optical element 102.

In the present disclosure, the wavelength converting element 20 is a region including a wavelength converting material. As will be described further below, the wavelength converting element 20 may be disposed on or in the reflective optical element 102, or may be disposed on the output substrate 52, as shown in fig. 3A.

The electrodes 211, 213 are arranged to connect the micro-LEDs 3 and the light-blocking elements 5 via addressing circuitry, such as TFTs (not shown), or directly with the row and column addressing electrodes 210, 212, respectively.

In the illustrative embodiment, the input light 110 from each of the plurality of micro LEDs 3 has the same color band as blue light. Advantageously, the micro-LEDs may be provided by a gallium nitride wafer over the entire micro-LED array. The forward voltage characteristics of the array may be the same for all the micro LEDs 3, thereby reducing the cost and complexity of the control system.

The wavelength converting elements 20R, 20G are formed on a first side of the output substrate 52, and the first side of the output substrate 52 faces the transparent front surface of the reflective optical element 102.

Each of the wavelength converting elements 20R, 20G is arranged to convert the input light 110 into visible light of a wavelength band different from that of the input light 110. The wavelength converting elements 20R, 20G may comprise phosphor or quantum dot materials. Highly efficient color conversion materials that have been tuned for the gallium nitride emission wavelength may be used, advantageously reducing cost and power consumption.

Input light rays 110 from the respectively aligned at least one micro LED3 are input through the light input region 35 of the transmissive front surface 33 and, after being incident on at least one of the reflective rear surfaces 43, are output through the at least one light output region 37 of the transmissive front surface 33. The output light 112 is incident on the wavelength converting array 120 and the corresponding wavelength converting elements 20R, 20G. At the wavelength conversion location 24, the light 112 undergoes wavelength conversion and the output light 118 is scattered. Some of the light rays 119 are scattered back and undergo reflection from the reflective rear surface 43 of the aligned reflective optical element 102 and are output as output light rays.

Advantageously, each reflective optical element 102 may provide an addressable color sub-pixel. Furthermore, if the wavelength converting material is provided directly on the micro LED3, the energy density at the wavelength converting material is significantly lower than the energy density. Furthermore, lowering the operating temperature of the wavelength converting material advantageously increases the conversion efficiency and material lifetime. Furthermore, a uniform angular illumination of the wavelength converting element 20 is provided, advantageously minimizing the color variation with angle.

In the case where the input light is blue light, it may be undesirable to provide wavelength conversion. Some of the reflective optical elements 102 are aligned with the diffusion region 21. In combination with the diffusion region 23 of the reflective rear surface 43 of the reflective optical element 102, the diffusion region 21 provides similar scattering properties to the light scattered by the wavelength converting elements 20R, 20G. Advantageously, uniform color can be provided from a wide range of viewing angles.

Features of the arrangement of fig. 3B that are not discussed in further detail may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 3C to 3D are schematic diagrams showing the arrangement of the wavelength converting elements 20R, 20G and the diffusion region 21 in a front view.

As shown in fig. 3C, the wavelength converting elements 20R, 20G and the diffusion region 23 may be arranged in a continuous strip, and the wavelength converting elements for adjacent reflective optical elements may be continuous in one direction. Each strip of consecutive wavelength converting elements 20R, 20G is arranged with an array of reflective optical elements 102.

Advantageously, this arrangement may be conveniently provided by printing or other known deposition methods on the support substrate 53. The angular diffusion characteristics of the regions 21 may be provided to match the diffusion produced by the wavelength converting elements 20A, 20B.

Fig. 3D shows that the wavelength converting elements 20R, 20G and the diffusion region 21 may be provided with a light absorbing mask 25, which may be provided between the regions 20A, 20G, 21. Advantageously, cross talk between adjacent colored sub-pixels may be provided, as stray light may be absorbed in the light absorbing mask 25.

Fig. 4 is a schematic diagram illustrating the operation of the reflective optical element 102, the micro-LEDs 3 and the aligned wavelength converting element in a side view, wherein the transmissive material 51 is arranged between the output substrate 52 and the reflective optical element 102.

Furthermore, for each reflective optical element 102 of the array of reflective optical elements 103, the reflective light input structure 44 is arranged to direct at least some light from the respective aligned at least one micro LED3 to at least one transmissive front surface 33 output area 37.

The diffusing region 21 and/or the wavelength converting elements 20R, 20G are formed on the output region 37 of the transmissive front surface 33. The output substrate 52 may be attached to the array 103 of reflective optical elements 102 by means of a material 51 which may be a transparent bonding material.

Further micro LEDs 3 and addressing electrodes 210, 212 may be arranged on the front surface 33 of the reflective optical element 102. Advantageously, a robust alignment of the micro-LEDs 3 and the reflective optical element 102 may be achieved.

Advantageously, an integrated optical structure without air gaps may be provided. Internal reflection and stray light can be reduced. In addition, sensitivity to ambient pressure changes may be reduced and alignment may be maintained between components of the display for temperature and pressure changes. Compared to fig. 3A, the parallax between the wavelength converting array 120 and the reflective optical element 102 may be reduced, thereby achieving improved crosstalk.

It may be assumed that features of the arrangement of fig. 4 that are not discussed in further detail correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Another arrangement of the array of micro-LEDs 3 and the array 103 of reflective optical elements 102 will now be described.

Fig. 5A is a schematic diagram showing, in a side perspective view, a color display device 100 including an array of micro LEDs 3, an array of wavelength converting elements 20R, 20G, an array of light diffusing regions 21, and an array of reflective optical elements 102 arranged on an output substrate 52. A plurality of micro LEDs 3 are formed on the output substrate 52.

Advantageously, the substrate 52 may comprise a material suitable for forming the addressing electrodes 210, 212 and for attaching micro LEDs 3 and other addressing electronics. For example, the substrate 52 may comprise a glass support substrate that may be processed at elevated temperatures compared to the polymeric material that may be used to form the body 47 of the reflective optical element 102. For example, the micro LEDs 3 may be attached to the substrate 52 by high temperature solder. Alternatively, the output substrate 52 may comprise a support substrate 53 comprising a flexible material, for example a polymer such as polyimide, which may be used with the electrode deposition techniques developed for flexible film OLED displays.

Features of the arrangement of fig. 5A, which are not discussed in further detail, may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Another arrangement of the reflective optical element 102 will now be described.

Fig. 5B is a schematic diagram showing, in a side perspective view, the reflective optical element 102 and the aligned micro-LEDs 3 arranged to provide pixel illumination, wherein the reflective optical element 102 comprises a wavelength converting element 20R arranged on the reflective rear surface 43.

Fig. 5B differs from fig. 2A in that the light input region 35 of the transmissive front surface 33 includes refractive input microstructures 72. The input microstructures 72 redistribute the cone of output light from the micro-LEDs 3 such that the input light rays 110 from the micro-LEDs 3 are directed towards the diffusing region 23 of the reflective rear surface 43. Advantageously, output efficiency can be improved.

Fig. 5B further illustrates that the reflective rear surface 43 includes recesses 70a, 70B. The wavelength converting elements 20R, 20G are formed on the reflective rear surface 43 of at least some of the reflective optical elements 102, and are formed in the recesses 70a, 70 b. The recesses 70a, 70b include the wavelength converting elements 20R. In other words, the material of the wavelength converting element 20R is arranged in the recesses 70a, 70 b. Alternatively, the recesses 70a and 70b may contain different wavelength converting materials, such as two different red phosphors, in order to create a wider color gamut for the display.

Features of the arrangement of fig. 5A, which are not discussed in further detail, may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 6A is a schematic diagram showing in side view the reflective optical element 102, the micro-LEDs 3 and the aligned wavelength converting element 20, wherein the reflective optical element 102 comprises a wavelength converting element arranged on the reflective rear surface 43. Recesses 70a, 70B may be provided in addition to or in place of the light diffusion regions 23a, 23B of fig. 2B. Thus, the recesses 70a, 70b may be provided with a wavelength converting material, such as quantum dots or phosphor material.

The transmissive material 40 arranged between the wavelength converting material in the region 20R and the transparent front surface 33 may additionally provide a protective coating for the material of the wavelength converting material. Advantageously, the material 40, the reflective coating 41, the material arranged to form the body 47 and the output substrate 52 may provide a barrier to migration of water and oxygen to the wavelength converting material. Other barrier layers 75, which may include inorganic coatings such as silicon oxide or aluminum oxide, may be disposed on the substrate 52 and the body 47. Advantageously, output efficiency can be improved and the life of the material can be extended.

The array 103 of reflective optical elements 102 may include an integrated body aligned with the substrate 52 on which the micro-LEDs 3 are formed. The array 103 and the integrated body of the substrate 52 comprising the micro LEDs 3 can be aligned in a single step without multiple individual alignments. Advantageously, alignment time and cost are reduced.

In operation, input light rays 110 from the respective aligned at least one micro LED3 are input through the light input region 35 of the transmissive front surface 33 and, after being incident on the at least one reflective rear surface 43 and the respective wavelength converting element 20R, 20G, are output as light rays 118 through the at least one light output region 37 of the transmissive front surface 33.

For the blue pixels, a diffusion region 23 may be provided instead of the wavelength converting elements 20R, 20G. The diffusing regions may be provided by a surface relief structure, such as that shown in fig. 2B, or may be provided by a volume diffuser, such as suspended white light scattering particles (such as titanium dioxide). For example, the bulk diffuser may be arranged in the curable material and in the recess 70 of the reflective optical element 102. Both bulk diffusion and surface relief diffusion may be provided, including microstructures 46 arranged on the reflective surface 43.

For color converted pixels, red and green pixels may scatter some blue light, which may undesirably reduce the color gamut.

It may be desirable to increase the color gamut.

The color display device 100 further comprises: a color filter array 122 comprising a plurality of absorptive color filter regions, the plurality of color filter regions 22 being arranged in an array; wherein each of the color filter regions is aligned corresponding to the light output region 37 of the transmissive front surface 33 of only one of the respective reflective optical elements 102 of the array of reflective optical elements 103.

The color filter array 122 may be disposed on an input surface of the output substrate 52 or may be formed on the output area 37 of the transmissive front surface 33. The color filter array 122 may transmit light rays 112 that are color converted by interaction with the material of the wavelength converting element 20 in the respective recess 70.

Features of the arrangement of fig. 6A that are not discussed in further detail may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 6B is a schematic diagram illustrating the operation of the reflective optical element 102, the micro-LEDs 3 and the aligned wavelength converting element 20 in a side view, wherein the micro-LEDs 3 are arranged on a transmissive material 40 arranged between the reflective back surface 43 and the transmissive front surface 33. Compared to the arrangement of fig. 6A, the micro-LEDs may be aligned on the reflective optical element 102 during manufacturing and further alignment steps are reduced, advantageously reducing cost and complexity. Features of the arrangement of fig. 6B that are not discussed in further detail may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 6C to 6D are schematic diagrams showing the arrangement of the color filters 22A, 22B for the color display device 100 of fig. 6A in a front view.

As shown in fig. 6C, the color filter array 122 may include a transparent region for a blue pixel, a green transmission filter 22A for a green pixel, and a red transmission filter 22B for a red pixel. Color leakage is reduced and, advantageously, the color gamut can be increased.

Fig. 6D shows that a further blue-absorbing color filter 22B may be provided. Advantageously, red and green light leakage due to stray light in the blue sub-pixel is reduced.

The arrangement of the wavelength converting element will now be further described.

Fig. 6E is a schematic diagram showing, in a front view, the alignment of the reflective optical elements 102, the micro-LEDs 3 and the wavelength converting elements 20R, 20G arranged on the reflective rear surfaces 43 of some of the reflective optical elements 102, wherein the reflective optical elements 102 are aligned with each micro-LED 3 of the array of micro-LEDs 3 and the micro-LEDs 3 are arranged to output light of the same color on the array of micro-LEDs 3.

Some of the reflective optical elements 102 are not aligned with the wavelength converting elements 20R, 20G and a diffuser 23, such as a bulk or surface relief diffuser, is provided, for example as described with respect to fig. 6A. The diffusion region 23 may be replaced by a color filter 23B so that, for example, the blue color of the micro LED3 emitting blue light may be changed.

Advantageously, an efficient color display with long lifetime materials and high color gamut can be provided.

It may be assumed that features of the arrangement of fig. 6E, which are not discussed in further detail, correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Various other arrangements of the micro LED3 array and the reflective optical element 102 will now be described.

Fig. 7A is a schematic diagram showing, in a front view, the alignment of the reflective optical elements 102, the micro-LEDs 3 and the wavelength converting elements 20R, 20G arranged on the reflective rear surfaces 43 of some of the reflective optical elements 102, wherein the reflective optical elements 102 are aligned with each of the micro-LEDs 3 in the array of micro-LEDs 3, and the micro-LEDs 3 are arranged to output light of the same color on the array of micro-LEDs 3, wherein the area of the micro-LEDs 3 varies according to the output wavelength of the light emitting element and the aligned wavelength converting element.

The size of the micro LEDs for the red, green and blue sub-pixels is different compared to fig. 6E. The efficiency of the luminous output may vary between the red, green and blue sub-pixels. The different sizes of the micro LEDs 3a, 3b, 3c may provide compensation for the difference in luminous efficiency of the red, green and blue sub-pixels. For the same driving voltage, a larger micro LED3 may provide a higher luminous flux than a smaller micro LED. Advantageously, the control system may be simpler with less complexity and cost.

Fig. 7B is a schematic diagram showing in front view the alignment of the reflective optical element 102, the micro-LEDs 3 and the wavelength converting elements 20R, 20G arranged on the reflective rear surface 43 of the reflective optical element 102, wherein the reflective optical element 102 is aligned with some of the micro-LEDs 3 of the array of micro-LEDs 3 and the micro-LEDs 3 are arranged to output light of the same color on the array of micro-LEDs 3.

Some of the micro LEDs 3B of the plurality of micro LEDs are not aligned with the reflective optical element 102 and further do not have the light blocking element 5. Light may be output directly through the output substrate 52 without being incident on the surface 45 of the body 47 by a reflector disposed between the micro LEDs 3B and the body 47. Alternatively, the surface 45 of the body 47 may include a reflective coating 41 so that light from the micro LEDs 3 is reflected and directed through the output substrate 52.

For example, the blue sub-pixel may be provided directly by the micro LED 3C, and the reflective optical element and wavelength converting element 20R, 20G may provide red and green light from the blue input light from the micro LED3R, 3G, 3B. Using the same color micro LEDs (e.g., blue) means that each display color channel (e.g., R, G, B) can be addressed by the same voltage. Advantageously, the cost and complexity of the array 103 of reflective optical elements may be reduced.

Fig. 7C is a schematic diagram showing the reflective optical element 102, the red-emitting micro LED3R, the blue-emitting micro LED 3G having the green wavelength converting element 20G, and the blue-emitting micro LED 3B in a front view. The green wavelength converting element 20G is arranged on the reflective rear surface 43 of some of the reflective optical elements 102, wherein the reflective optical elements 102 are aligned with each of the micro LEDs 3R, 3G, 3B in the array of micro LEDs, and the micro LEDs 3R, 3G, 3B are arranged to output light of different colors on the array of micro LEDs.

The input light 110 from some of the micro LEDs 3R of the plurality of micro LEDs 3 is red light and the input light 110 from some of the micro LEDs 3G, 3B of the plurality of micro LEDs is blue light.

Advantageously, the optical output distribution may be substantially the same for each color pixel and may provide an improved luminous efficiency for the red sub-pixel compared to the wavelength converting light from blue to red. The forward voltage difference between driving the red micro LEDs 3R and the blue micro LEDs 3B may be compensated for to control the current of the micro LEDs 3 and/or to adjust the driving voltage for different color columns of the micro LEDs 3.

Fig. 7D is a schematic diagram showing the reflective optical element 102, the red-emitting micro LED3R, the blue-emitting micro LED 3G having the green wavelength converting element 20G, and the blue-emitting micro LED 3B in a front view. The green wavelength converting element 20G is configured on the reflective rear surface 43 of the reflective optical element 102 aligned with the micro-LEDs 3G in the array of micro-LEDs, and the micro-LEDs 3R are arranged to output light of different colors to the micro-LEDs 3G, 3B in the array of micro-LEDs.

Thus, the color-converted sub-pixels may be illuminated by the blue micro LEDs 3B converted to green light by the wavelength converting element 20G, while the blue and red pixels are provided by the blue and red micro LEDs 3B, 3R without the reflective optical element 102. Advantageously, a less complex arrangement is provided, thereby reducing costs.

Fig. 7E is a schematic diagram showing, in front view, the alignment of the reflective optical elements 102, the micro-LEDs 3R, 3G, 3B, and the wavelength converting element 20G on the reflective rear surface 43 of some of the reflective optical elements 102, wherein each of the first plurality of reflective optical elements 102 is aligned with a red-emitting micro-LED 3R and a blue-emitting micro-LED 3B, and further includes a light diffusing region 21; and each of the second plurality of reflective optical elements 102 is aligned with a micro LED 3G that emits blue light and further includes a green wavelength converting element 20G.

In comparison to the arrangement of fig. 7A, the resolution of the display is advantageously increased, since some color reflective optical elements 102 can provide two different addressable colors. In addition, for a given pixel pitch, increased feature size may be provided, advantageously reducing cost and complexity of processing and replication.

Fig. 7F is a schematic diagram showing in front view the reflective optical element 102 and the aligned uv-emitting micro LEDs 3R, 3G, 3B, which are not red, green and blue light emitting micro LEDs but are instead uv-micro LEDs addressed with red, green and blue pixel data. The wavelength converting elements 20R, 20G, 20B are arranged on the reflective rear surface 43 of the respective reflective optical element 102, wherein the reflective optical element 102 is aligned with each micro LED3R, 3G, 3B in the array of micro LEDs, and the micro LEDs 3R, 3G, 3B are arranged such that the input light 110 is ultraviolet light.

In contrast to the arrangement of fig. 7A, a blue wavelength converting element 20B is provided to convert ultraviolet light into blue light. Advantageously, a uniform array of micro LEDs is provided, thereby reducing cost and complexity of assembly and addressing. By providing an ultraviolet filter on or in the output substrate 52, further leakage between pixels of the input light 110 may be minimized. . Thereby crosstalk can be reduced. There is no visible mixing of the input waveband of light with the wavelength conversion band of the output light and the color gamut of the display is improved.

Features of the arrangement of fig. 7A-7F, which are not discussed in further detail, may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 7F further shows the arrangement of electrodes 212, 213, 210 and a drive circuit 820 for addressing the micro LEDs 3R, 3G, 3B, as will be described further below.

It may be desirable to provide micro-LEDs on an opaque support substrate.

Fig. 8A is a schematic diagram showing another structure of the reflective optical element 102, the aligned micro-LEDs 3 and the aligned wavelength converting element 20 in a side view, wherein the aligned micro-LEDs 3 are arranged on an opaque support substrate 155. Transparent substrate 153 is provided with retarder 54, polarizer 56, and optional color filters as described elsewhere herein. It may be assumed that features of the arrangement of fig. 8A that are not discussed in further detail correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

In contrast to the arrangement with the transparent support substrate 53, the light emitted from the micro LEDs is provided in the same direction as the output substrate 52. The reflective light input structure 44 provides total internal reflection for the light rays 110 from the micro-LEDs 3 such that the light rays are directed onto the wavelength converting element 20 and the output surface 33.

The substrate 155 may be provided with an opaque electrode material and other control electronic components that do not reduce output efficiency. Advantageously, efficiency may be improved. Furthermore, the substrate 155 may be provided with thermally conductive regions and/or layers arranged to achieve a reduced semiconductor junction temperature during operation of the micro LED. Advantageously, the efficiency of the micro LEDs may be increased.

Fig. 8B is a schematic diagram showing another structure of the reflective optical element, the aligned micro-LEDs and the aligned wavelength converting element in a side view, wherein a portion of the aligned micro-LEDs and reflective optical element are arranged on an opaque support substrate 155. In contrast to fig. 8A, the reflective rear surface 43 may be formed on the substrate 155. The transmissive material 40 and the walls 49 may be formed on a surface of the substrate 155. Advantageously, the thickness can be reduced. Further differences in thermal expansion between the substrate 155 and the array of reflective optical elements 103 may be reduced, thereby achieving increased uniformity.

Fig. 9A is a schematic diagram showing yet another example structure of the reflective optical element 102, the aligned micro-LEDs 3 and the aligned wavelength converting elements in a side view. In contrast to fig. 6A, the reflective light input structure 44 includes a single inclined surface. This structure of the reflective optical element 102 can be more easily machined and/or reliably replicated than the structure of fig. 6A. Furthermore, only one recess 70 may be provided, thereby reducing the cost and complexity of forming the wavelength converting element 20 in the recess. Fig. 9A further illustrates that the reflective light input structure 44 may form a wall 49 of the reflective optical element 102.

It may be assumed that features of the arrangement of fig. 9A that are not discussed in further detail correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

Fig. 9B is a schematic diagram showing, in a front view, the arrangement of the reflective optical element 102, the micro LEDs 3, and the wavelength converting elements 20R, 20G, which are arranged to provide an incremental pixel pattern and use the reflective optical element 102 of fig. 9A. Advantageously, the appearance of the image that moves the image can be improved. Features of the arrangement of fig. 9B, which are not discussed in further detail, may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

It may be desirable to provide phosphors for wavelength conversion materials in high resolution displays.

Fig. 10A is a schematic diagram shown in a side view, and fig. 10B is a schematic diagram showing the reflective optical element 102, the micro-LEDs 3 and the aligned wavelength converting element in a top view, and wherein the wavelength converting material comprises a material 400 having the following characteristics: having a relatively large particle size compared to the size of the micro LEDs 3. Material 400 may include one or more phosphors.

In cellular phone applications, a typical sub-pixel size is 15x 45 microns. Phosphor materials can provide efficient wavelength conversion, but are typically produced by grinding into small particles 400, typically 5 microns in size or larger. The indentations 70 arranged on the reflective side 43 of the reflective optical element 102 may confine such particles in a bonding material 80 such as silicone and provide illumination of the phosphor of such particle size at smaller pixel pitch (i.e., at off-axis angles), thus increasing the effective area of the phosphor for incident illumination even for low packing density resulting from the large particle 400 size.

Advantageously, high conversion efficiency and color gamut can be provided for high resolution color displays 100. Compared to quantum dot materials, additional phosphors are generally insensitive to oxygen and water, and such devices can achieve long lifetimes. Furthermore, the phosphor particles 400 are far from the micro LEDs 3, and thus the operating temperature of the phosphor may be reduced and the phosphor efficiency may be improved.

The reflective optical element 102 may include an air gap 50 between the walls 49, thereby reducing cost and complexity of assembly. Input light rays 110 from the respective aligned at least one micro LED3 are input through at least one light input region 35 of the light transmissive opening 133 and, after being incident on the at least one reflective rear surface 43 and the respective aligned wavelength converting element 400, are output through a different light output region 37a, 37b than the light input region 35 of the light transmissive opening 133.

Fig. 10C is a schematic diagram showing in side view the reflective optical element 102, the micro-LEDs 3 and the aligned wavelength converting elements, wherein the wavelength converting material comprises a large particle size material 400, and wherein the micro-LEDs 3 are arranged on a light transmissive material 40 arranged between the reflective back surface 43 and the light transmissive front surface 33. Compared to the arrangement of fig. 10A, the micro-LEDs 3 can be aligned on the reflective optical element 102 during manufacturing and alignment of the separate substrates is reduced, advantageously reducing cost and complexity.

It may be assumed that features of the arrangement of fig. 10A-10C, which are not discussed in further detail, correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

It may be desirable to provide directional output from the display 100.

Fig. 11A is a schematic diagram showing an array of reflective optical elements 102 and an aligned array of micro-LEDs 3 in a front view, wherein the width of the output of the transparent output area of the reflective optical elements 102 is reduced. The input light 110 is confined within the width 192 of the output area of the reflective optical element 102, while no light is emitted in the area of the light blocking element 5. Thus, a narrow width pixelated light source is provided by each reflective optical element 102.

FIG. 11B is a schematic diagram showing the array of reflective optical elements 102 in a top view with the width 192 of the output of the transparent output region of the reflective optical elements 102 reduced and arranged to align with the array of collimating catadioptric optical elements 38 having an input width 712.

The catadioptric optical element 38 is aligned with the output of each reflective optical element 102 having a width 192 equal to or less than the width 712 of the input of the catadioptric optical element 38.

Illustrative light rays 190 are output from the reflective optical element 102 at high output angles relative to the normal direction of the display 100. Such light rays are guided through catadioptric optical element 38 by total internal reflection and/or refraction so as to be output at an angle close to the normal direction. Features of the arrangement of fig. 11A-11B that are not discussed in further detail may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

FIG. 11C is a schematic diagram of a directional display showing a primary user and an off-axis snooper of display 100 of FIG. 11B in a top view.

Catadioptric optical element 38 reduces the angular dimension 304 of the cone of light from reflective optical element 102. Advantageously, the front emission intensity is increased and the display efficiency of the front user 300 is enhanced.

In addition, a privacy display, as shown in FIG. 11C, may be provided such that the displayed image is not viewable by snoopers 302. Such privacy displays may also provide low stray light for off-axis operation, such as in night use and automotive displays.

The directional output includes a non-lambertian optical output light intensity distribution to achieve greater efficiency toward the front user. Such a directional distribution typically has a solid angle distribution with a full width of half maximum luminance in at least one axis, less than 50 degrees for wide-angle operation mode and less than 30 degrees for private or stray light operation mode.

It may be desirable to provide a switchable privacy display.

Fig. 11D is a schematic diagram showing, in top view, an array of reflective optical elements and an array of aligned micro-LEDs aligned to an array of collimating catadioptric optical elements 38 and an array of linear waveguides 39 to provide a switchable privacy color display 100.

Switchable private displays comprising micro LEDs are described in PCT/GB2018/050893, and the disclosure of this patent is incorporated herein by reference in its entirety.

In operation, light from the reflective optical element 102a is aligned with the catadioptric optical element 38 to provide a cone of light with a narrow angular dimension 304 as shown in FIG. 11C.

Light from the reflective optical element 102b is aligned with the linear waveguide 39 disposed between the catadioptric optical elements 38. Light rays 191 are provided having a distribution of substantially the same direction as the light rays in the reflective optical element 102 b. Returning to the description of FIG. 11C, the light cone 306 may be provided by illuminating the micro-LEDs 3 directed at the reflective optical element 102 b. Advantageously, the display may be switched between a narrow angle mode for power saving and privacy operation and a wide angle mode for multiple users and higher image uniformity.

It may be assumed that features of the arrangement of fig. 11D, which are not discussed in further detail, correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

The structure and operation of catadioptric optical element 38 will now be further described.

FIG. 11E is a schematic diagram illustrating the structure and operation of a catadioptric optical element and an aligned reflective optical element in a top view.

The catadioptric optical element 38 includes, in at least one catadioptric cross-section through its optical axis 711, a first outer surface 746a and a second outer surface 746b facing the first outer surface 746 a. First and second outer surfaces 746a, 746b include curved surfaces.

The first outer surface 746a and the second outer surface 746b extend from the first end 707 of the catadioptric optical element 38 to the second end 708 of the catadioptric optical element 38, the second end 708 of the catadioptric optical element 38 facing the first end 707 of the catadioptric optical element 38;

the distance 712 between the first and second outer surfaces 746a, 746b at the first end 707 of the catadioptric optical element 38 is less than the distance 714 between the first and second outer surfaces 746a, 746b at the second end 708 of the catadioptric optical element 38.

At least one transparent inner surface 742, 744 is disposed between first end 707 and second end 708 and between first outer surface 746a and second outer surface 746 b.

Reflective optical element 102 may be positioned between first end 707 of catadioptric optical element 38 and at least one transparent inner surface 742, 744 of catadioptric optical element 38 and aligned with the catadioptric optical element. For example, in a cross-sectional plane, the center of the reflective optical element 102 may be aligned with the optical axis 711 of the catadioptric optical element. In the present disclosure, the term "at the first end" of the catadioptric optical element includes, for example, that the micro-LEDs are small below the first end 707, in the same plane as the end 707 of the catadioptric optical element 38, or near the end 707, or near or adjacent to the end 707. In each case, this may include alignment with the optical axis of the catadioptric optical element. The above description can be applied to all embodiments.

Catadioptric optical systems use the reflection and refraction of light. Further, a catadioptric optical system is a system in which refraction and reflection are combined by a lens (dioptric) and a curved mirror (catadioptric) generally in an optical system. The catadioptric optical elements may include RXI optical elements that effect ray deflection through refraction (R), metal reflection (X), and total internal reflection (I).

The first outer surface 746a and the second outer surface 746b each include a curved surface extending from the first end 707 of the catadioptric optical element to the second end 708 of the catadioptric optical element 38, with the second end 708 of the catadioptric optical element facing the first end 707 of the catadioptric optical element 38. Further, the transparent inner surfaces 742, 744 comprise at least one curved surface 742. An outer angle 715 between the first end 707 and the first outer surface 746a at the first end 707 may be less than an outer angle 717 between the first outer surface 746a at the first end 707 and the second end 708. Further, an outer angle between first end 707 and second outer surface 746b at first end 707 is less than an outer angle between first end 707 and second outer surface 746b at second end 708.

Advantageously, collimated light can be provided with a directional light output distribution with a narrow cone angle.

The catadioptric optical element 38 can be arranged to provide substantially collimated output light from the reflective optical element 102 for light incident on at least one of the curved outer surfaces 746a, 746b and the transparent inner surface 744, which can have positive optical power. Further, at least one of the transparent inner surfaces 744 may have zero optical power. Advantageously, the surface 744 may be conveniently provided during the machining and molding steps of manufacture. Further, these surfaces may cooperate to provide collimated light for all light rays from the reflective optical element 102 over a high output solid angle.

Thus, some of the light output illustrated by rays 718 of a reflective optical element 102 of the plurality of reflective optical elements 102 is transmitted by the at least one transparent inner surface 744, then reflected at the first or second outer surfaces 746a, 746b and directed into the first directional light output distribution 120; and some light output shown by ray 716 of a reflective optical element 102 of the plurality of reflective optical elements 102 is transmitted by the at least one transparent inner surface 742 and directed into the first directional light output distribution 120 without reflection at the first or second outer surfaces 746a, 746 b.

In at least one cross-sectional plane, the present embodiment reduces the width of the output directional light output distribution to provide directivity with a directional light output distribution (as described by solid angle Ω out) that is smaller than the input directional light output distribution (as described by solid angle Ω in) of the catadioptric optical element.

FIG. 12A is a schematic diagram showing an addressing system for multiple LEDs. The electrodes 211, 213 of fig. 3B for each micro LED3 of the plurality of micro LEDs 3 are connected to a column address electrode 212 and a row address electrode 210, respectively, to form a matrix. In this embodiment, an array of current sources 816 is used to drive the address electrodes 212. The voltage on each of the row electrodes 210 is sequentially pulsed to scan or address the array of micro LEDs 3. The current source 816 may be provided for each column electrode 212 or may be time multiplexed (shared) between a set of column electrodes 212. The micro LEDs 3 have a relatively sharp voltage-current curve and can be operated with very short pulses without cross talk between them. The array of micro LEDs 3 forms an addressable display without the need for additional active components such as TFTs or integrated circuits at each pixel. However, all the energy to illuminate the micro-LEDs must be supplied during the addressing pulse. Advantageously, the addressing matrix is simple and low cost.

It may be desirable to reduce the peak LED current while maintaining the light output level. Returning to the description of fig. 7F, the drive circuit 820 and the additional address electrode 213 are shown in an embodiment where the circuit 820 at the pixel can achieve an extended drive time for each pixel.

FIG. 12B is a schematic diagram illustrating another addressing embodiment for multiple LEDs. The micro LEDs 3 of the plurality of micro LEDs 3 are addressed by the column address electrodes 212 and the row address electrodes 210 to form a two-dimensional matrix. For the sake of clarity, only one micro LED3 and one column electrode 212 and one row electrode 210 of the matrix are shown. Fig. 12B differs from fig. 12A in that each micro LED3 has associated with it an integrated circuit 808 that includes a memory or latching function. The integrated circuit 808 may be an analog or digital circuit and may be implemented as a separate chip that is positioned using a method similar to the micro LED3 positioning method, or may be implemented as a TFT. The integrated circuit 808 may be provided with one or more additional supply potentials V1, V3. The driver circuit 820 includes an integrated circuit 808. When the row electrode 210 is pulsed, a clock input 810 of the integrated circuit 808 stores the voltage of the column electrode 212 connected to a data input 812. The output 814 of the integrated circuit 808 drives the micro-LEDs 3. The other end of the micro-LED is connected to a supply potential V3. Depending on the design of the integrated circuit 808, the potential V1 may be different from V3. The integrated circuit 808 may include a voltage-to-current converter. The potential V3 on the electrode 213 and the anode and cathode connections of the micro-LED 3 may be configured such that the micro-LED is forward biased and emits light. The integrated circuit 808 provides drive to the micro-LEDs 3 for a longer time than the duration of the addressing pulse on the row electrodes 210 and reduces the peak current drive to the micro-LEDs 3. Advantageously, the peak current in each micro LED3 is reduced.

FIG. 12C is a schematic diagram illustrating another addressing embodiment for multiple LEDs. The micro LEDs 3 of the plurality of micro LEDs 3 are addressed by the column addressing electrodes 212 and the row addressing electrodes 210 to form a two-dimensional matrix or array. The driver circuit 820 includes the TFT 806, the amplifier 804, and the capacitor 818. In this embodiment, the row electrode 210 is connected to the gate of the TFT 806, and data from the column address electrode 212 is stored on the capacitor 818 when the row address electrode 210 is pulsed. The capacitor 818 may be small compared to the capacitors typically used in a matrix to drive an LCD panel, and may be provided by the input capacitance of the amplifier 804. The amplifier 804 may drive one or more micro LEDs 3. Amplifier 804 may be supplied with 1 or more supply voltages (not shown). The amplifier 804 may include a voltage-to-current converter circuit. V1 may be ground or reference potential. The voltage output from amplifier 804 must be greater than the voltage V3 on electrode 213 by the combined forward voltage drop (Vf) of micro LED3 in order for micro LED3 to emit light.

The time to drive each micro LED3 is increased. Advantageously, current crowding may be reduced and device efficiency improved.

The operation of the LEDs and micro LEDs 3 will now be described.

Fig. 13A is a schematic diagram showing, in side view, the luminous intensity emission distribution from a macroscopic LED 303, the dimensions of which are typically included in a packaged LED, for example 0.5 x 0.5mm or more.

Fig. 13B is a schematic diagram showing, in side view, the luminous intensity emission distribution from the micro LEDs 3 mounted on the backplane substrate 447 and arranged to emit light from the backplane substrate 447.

After the emitted light 440 within the macro LEDs 303 and the micro LEDs 3, the high refractive index of the gallium nitride causes the light to be guided within the chip.

For macroscopic LEDs 303, surface roughening may provide top surface light extraction, and such LEDs 330 typically output a substantially lambertian luminous intensity distribution 442 from their top surface, while emitting from the edge with a lower level of luminous intensity distribution 404.

Scaling to the micro-LED size, however, the surface roughening has less effect on the output scattered by the top surface, and thus the proportion of light output by edge emission increases, and thus the top surface emission intensity distribution 446 decreases compared to the edge emission intensity distribution 448. With known micro LED surface mount methods, such increased edge emission from the micro LED may reduce the light output efficiency for a desired output direction (e.g., normal direction).

Fig. 14 is a schematic diagram showing the variation in optical path length through a small particle size wavelength conversion coating 450 in side view.

The thickness of such a coating 450 is different from the thickness of a light ray 452 directed in the surface normal direction compared to a light ray 454 emitted in the lateral direction. Such different thicknesses may provide an undesirable output color change in the viewing direction. Further, light may be lost in thicker wavelength converting material layers, thereby reducing efficiency. Furthermore, a precise method with a very small amount of material can be used to provide control of the color output.

Further heating from the micro-LEDs 3 may degrade the efficiency and lifetime of the wavelength converting material 450.

Advantageously, this embodiment achieves a uniform illumination of the light 452, 454 from the micro LEDs 3 to the wavelength converting element 20 and reduces the operating temperature of the wavelength converting material.

The arrangement of phosphor particles 400 with micro LEDs in a known color output micro LED3 will now be described.

FIG. 15A is a schematic diagram showing, in side view, output from a micro LED including a wavelength converting coating having a large particle size; and fig. 15B is a schematic diagram showing the output from a micro LED including a wavelength conversion coating having a large particle size in a front view. As previously mentioned, the particles 400 of phosphor may have a size similar to the size of the micro LEDs 3 used for high resolution cell phone applications. As a result, light may be lost between the particles 400, and the color gamut may be reduced and the color output on the micro LED3 array may not be uniform. Advantageously, this embodiment achieves uniform illumination of the phosphor material as shown in fig. 10A-10B.

It may be assumed that features of the arrangement of fig. 15A-15B, which are not discussed in further detail, correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

The method of manufacturing the array 103 of reflective optical elements 102 and the color display 100 will now be described.

Fig. 16A-16G are schematic diagrams illustrating a method of forming an array of reflective optical elements 102 and an aligned micro LED array in a side view. For clarity of illustration, a representative pair of reflective optical elements 102 of the array 103 is shown, but in practice, the array 103 may include millions of reflective optical elements 102, numbering the total number of color sub-pixels in a display or a number of displays.

In a first step, as shown in fig. 16A, the tool 150 may be provided, for example, by diamond turning of a metal working blank.

In a second step, shown in fig. 16B, the body 47 may be formed by embossing, casting, injection molding or other known replication methods to the tool 150, and the tool 150 removed.

In a third step, shown in fig. 16C, a coating 41 may be applied to the body 47. The coating may be an evaporated, sprayed or sputtered metal coating or may comprise a coated white material formed, for example, by dip coating or spraying. Alternatively, the body may be formed of a reflective white material, such as CEL-W epoxy sold by Hitachi Chemical, and the third step is omitted.

In a fourth step, as shown in fig. 16D, a wavelength converting material may be applied on the surface or in the recesses 70 of the reflective surface to provide the wavelength converting element 20. The recesses 70 provide defined locations for the wavelength converting material when deposited from a liquid solution, for example by inkjet printing. After deposition, the liquid carrier is evaporated to leave the wavelength converting material.

In a fifth step, shown in fig. 16E, a filler material 40 is provided between the reflective surface and the mold and cured to provide the output surface 33. The reflective optical elements 102 have a spacing s2 in the first direction.

In a sixth step, as shown in fig. 16F, the micro-LEDs 3 and the address electrodes (not shown) are arranged on the surface 33, wherein the spacing s1 of the micro-LEDs 3 in the same first direction is the same as the spacing s 2.

In a seventh step shown in fig. 16G, a light blocking layer 5 is formed on the micro LED 3. The light blocking layer may be a metal or a black resin. In embodiments where the light-blocking layer 5 is a metal, it may also be used as part of the pixel addressing circuitry for addressing and controlling the micro LEDs 3.

Features of the arrangement of fig. 16A-16G, which are not discussed in further detail, may be assumed to correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

A highly parallel manufacturing method for the color display 100 will now be described.

Fig. 17A to 17F are schematic diagrams illustrating in side view a method of forming an array of displays 100 comprising an array of reflective optical elements 102 and an aligned array of micro LEDs 3 in a parallel manner.

As shown in fig. 17A, a monolithic LED wafer 2, which may be, for example, gallium nitride, may be formed on a substrate 4, which may be, for example, sapphire, silicon, or silicon carbide, for example.

As shown in fig. 17B, a non-monolithic array of micro-LEDs 3 may be extracted from a monolithic wafer 2 to provide micro-LEDs 3a, 3B with spacing s 1.

As shown in fig. 17C, the micro-LEDs 3a, 3b may be arranged on the substrate 52 in alignment with the addressing electrodes and other optical, electrical and thermal management elements (not shown) such that the spacing s1 is maintained.

As shown in fig. 17D, the substrate 52 may be aligned with a plurality of micro-LEDs spaced at s 1.

As shown in fig. 17E, the substrate 52 and the array 103 are aligned, and thus each micro-LED 3 is aligned with a respective reflective optical element 102.

It may be desirable to provide a plurality of illumination devices from a large area of aligned optical elements. As shown in fig. 17F, the substrate 52 and the array 103 may be provided at a much larger area than that of a single display. Thus, various different color displays 100 having different regions and shapes 600, 602, 604, 606 can be extracted.

Advantageously, a large number of displays 100 can be formed over a large area using a small number of extraction steps, while maintaining alignment with the corresponding array of optical elements.

Additional device seal lines 601 may be provided at the edges of each element to provide a hermetic seal of the optical element and to reduce the ingress of dust and other materials into the optical element during use.

Advantageously, manufacturing costs and complexity may be reduced, and reliability during use may be increased.

It may be assumed that features of the arrangement of fig. 17A-17F, which are not discussed in further detail, correspond to features having equivalent reference numerals as described above, including any potential variations in the features.

As may be used in this disclosure, the words "substantially" and "approximately" provide a tolerance that is accepted in the industry for the relativity between their corresponding words and/or items. Such industry accepted tolerances range from zero to ten percent and correspond to, but are not limited to, length, position, angle, and the like. The correlation between these items is between about zero percent and ten percent.

Embodiments of the present disclosure may be used in a variety of optical systems. This embodiment may include or work with various lighting, backlights, optical components, displays, tablets, and smart phones, for example. Aspects of the present disclosure may be used with virtually any device involving a display, ambient lighting, an optical device, an optical system, or with any device incorporating any type of optical system. Accordingly, embodiments of the present disclosure may be used in displays, ambient lighting, optical systems, and/or devices used in many consumer professional or industrial environments.

It is to be understood that the disclosure is not limited in its application or creation to the details of the particular arrangements illustrated, since the disclosure is capable of other embodiments. Moreover, aspects of the present disclosure may be set forth in different combinations and arrangements to define their own unique embodiments. Also, the terminology used in the present disclosure is for the purpose of description and not of limitation.

While embodiments in accordance with the principles disclosed herein have been described, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the described exemplary embodiments, but should be defined only in accordance with any claims and their equivalents that issue from the present disclosure. Additionally, the above-described advantages and features are provided in described embodiments, but shall not limit the application of these issued claims to processes and structures accomplishing any or all of the above-described advantages.

Section headings herein are included to provide organizational cues. These headings should not be used to limit or characterize the embodiments set forth in any claims that may issue from this disclosure. To take a specific example, although the headings refer to a "technical field," the claims should not be limited by the language selected under this heading to describe the field. Furthermore, the description of technology in the "background" should not be construed as an admission that certain technology is prior art to any embodiment in the present disclosure. The summary of the invention is not to be considered a characterization of the embodiments in the issued claims. Furthermore, any reference in this disclosure to the singular form of "the invention" should not be taken to claim that this disclosure is novel only. Embodiments may be set forth according to the limitations of the claims issuing from this disclosure, and these claims define the embodiments protected by them and their equivalents. In all cases, the scope of the claims should be considered in light of the present disclosure, in their own right, and should not be limited by the headings used in this disclosure.