阅读说明：本技术 投影式裸眼三维显示装置 (Projection type naked eye three-dimensional display device ) 是由 范宸逸 乔文 钱小行 张晨 陈林森 于 2019-11-25 设计创作，主要内容包括：本申请涉及一种投影式裸眼三维显示装置,属于显示技术领域,包括：投影装置和设置于投影装置的出光端的指向性投影屏幕；指向性投影屏幕包括谐衍射透镜阵列,谐衍射透镜阵列用于将具有不同波长的光线会聚至目标视点；可以解决现有的大幅面裸眼3D显示装置的衍射效率低、难以消除零级光的影响的问题；由于谐衍射透镜阵列具有更高的衍射效率,因此可以根据空间光调制器上滤光片的中心波长设计谐衍射透镜阵列的谐衍射的相位因子,使得不同波长的出射光聚焦至空间同一点以实现裸眼彩色3D显示,可以消除色散；同时谐衍射透镜阵列为连续形面,理论衍射效率可以达到100％,可以提高衍射效率,从而提高光能利用率。(The application relates to a projection type naked eye three-dimensional display device, which belongs to the technical field of display and comprises: the projection device comprises a projection device and a directional projection screen arranged at a light outlet end of the projection device; the directional projection screen comprises a harmonic diffraction lens array, wherein the harmonic diffraction lens array is used for converging light rays with different wavelengths to a target viewpoint; the problems that an existing large-format naked eye 3D display device is low in diffraction efficiency and difficult to eliminate influence of zero-order light can be solved; because the harmonic diffraction lens array has higher diffraction efficiency, the harmonic diffraction phase factor of the harmonic diffraction lens array can be designed according to the central wavelength of the optical filter on the spatial light modulator, so that the emergent light with different wavelengths is focused to the same point in space to realize naked eye color 3D display, and the chromatic dispersion can be eliminated; meanwhile, the harmonic diffraction lens array is a continuous surface, the theoretical diffraction efficiency can reach 100%, and the diffraction efficiency can be improved, so that the light energy utilization rate is improved.)

1. A projection-type naked eye three-dimensional display device, comprising:

a projection device for projecting a projection image;

the directional projection screen is arranged at the light emitting end of the projection device; the directional projection screen includes a harmonic diffractive lens array for converging light rays having different wavelengths to a target viewpoint.

2. The projective naked-eye three-dimensional display device of claim 1, wherein the harmonic diffraction lens array comprises a plurality of pixel units, each pixel unit being one harmonic diffraction lens or being a part of one harmonic diffraction lens, each pixel unit being configured to converge the received light rays with different wavelengths to the target viewpoint.

3. The projective naked-eye three-dimensional display device according to claim 2, wherein the number of the target viewpoints is n, and n is a positive integer;

the n pixel units form a volume pixel, and the n pixel units in each volume pixel correspond to the n target viewpoints one by one.

4. The projective naked-eye three-dimensional display device of claim 3, wherein the plurality of pixel units are closely arranged; and/or the plurality of volume pixels are closely arranged.

5. The projective naked-eye three-dimensional display device of claim 3, wherein a light-transmitting medium is arranged between the plurality of pixel units; and/or a light-transmitting medium is arranged among the plurality of volume pixels.

6. The projective naked-eye three-dimensional display device of claim 3, wherein the n pixel units in each volume pixel have different periods and different orientations so as to converge the incident light rays with different wavelengths to the corresponding target viewpoints.

7. The projective naked-eye three-dimensional display device of claim 2, wherein the projection device comprises a plurality of sub-pixels, and the plurality of sub-pixels are in one-to-one correspondence with the plurality of pixel units.

8. The projective, naked-eye three-dimensional display device of claim 2, wherein the phase factor of the harmonic diffraction of each pixel unit is determined according to the central wavelength of the light.

9. The projection type naked eye three-dimensional display device according to any one of claims 1 to 8, wherein the projection device comprises a display chip and a projection lens which are sequentially arranged at a light outlet end of the directional light source; the display chip is used for acquiring an optical signal irradiated by the directional light source; modulating the optical signal and the multi-view image signal to obtain a modulation signal; outputting the modulation signal to the projection lens; the projection lens is used for amplifying the modulation signal to obtain a projection image and projecting the projection image to a directional projection screen.

10. The projective naked-eye three-dimensional display device of claim 9, wherein the display chip comprises a spatial light modulator.

Technical Field

The application relates to a projection type naked eye three-dimensional display device, and belongs to the technical field of display.

Background

Three-dimensional (3D) display technology refers to a technology in which a picture becomes stereoscopic and realistic and an image is no longer limited to a two-dimensional plane of a screen. The 3D display technology includes a glasses type and a naked eye type, and the glasses type 3D display technology requires additional auxiliary equipment (such as 3D glasses and the like) to observe a stereoscopic image. The naked eye type 3D display technology becomes a main development trend of the future 3D display technology due to the fact that auxiliary equipment is not needed, and the viewing is convenient and fast.

Naked eye 3D display technologies based on the principle of parallax include the visual barrier method, the micro-cylindrical lens method and the like. In these techniques, a view-blocking screen or a micro-cylinder lens array is disposed on a surface of a liquid crystal display panel to achieve separation of images of different viewing angles in spatial angle. The existing large-format naked-eye 3D display device comprises a projection device and a directional projection screen, wherein the directional projection screen comprises a plurality of pixel arrays, and a single pixel is a nanometer diffraction grating.

However, the conventional naked-eye 3D display device using a common diffraction element has low diffraction efficiency, is difficult to eliminate the influence of zero-order light, and has low light energy utilization rate.

Disclosure of Invention

The application provides a three-dimensional display device of projection bore hole, can solve the problem that current big breadth bore hole 3D display device's diffraction efficiency is low, be difficult to eliminate the influence of zero order light. The application provides the following technical scheme: the projection type naked eye three-dimensional display device comprises:

a projection device for projecting a projection image;

the directional projection screen is arranged at the light emitting end of the projection device; the directional projection screen includes a harmonic diffractive lens array for converging light rays having different wavelengths to a target viewpoint.

Optionally, the harmonic diffractive lens array comprises a plurality of pixel elements, each pixel element being one or part of one harmonic diffractive lens, each pixel element being configured to converge received light rays having different wavelengths to the target viewpoint.

Optionally, the number of the target viewpoints is n, where n is a positive integer;

the n pixel units form a volume pixel, and the n pixel units in each volume pixel correspond to the n target viewpoints one by one.

Optionally, the plurality of pixel units are closely arranged; and/or the plurality of volume pixels are closely arranged.

Optionally, a light-transmitting medium is arranged between the plurality of pixel units; and/or a light-transmitting medium is arranged among the plurality of volume pixels.

Optionally, the n pixel cells in each volume pixel have different periods and different orientations to converge the incident light rays with different wavelengths to the corresponding target viewpoints.

Optionally, the projection device includes a plurality of sub-pixels, and the plurality of sub-pixels correspond to the plurality of pixel units one to one.

Optionally, the phase factor of the harmonic diffraction of each pixel element is determined from the central wavelength of the light.

Optionally, the display chip comprises a spatial light modulator.

Optionally, the projection device includes a display chip and a projection lens sequentially disposed at a light exit end of the directional light source; the display chip is used for acquiring an optical signal irradiated by the directional light source; modulating the optical signal and the multi-view image signal to obtain a modulation signal; outputting the modulation signal to the projection lens; the projection lens is used for amplifying the modulation signal to obtain a projection image and projecting the projection image to a directional projection screen.

Optionally, the display chip comprises a spatial light modulator.

The beneficial effect of this application lies in: the projection device comprises a display chip and a projection lens which are sequentially arranged at the light-emitting end of the directional light source; the display chip is used for acquiring an optical signal irradiated by the directional light source; modulating the optical signal and the multi-view image signal to obtain a modulation signal; and outputting the modulation signal to a projection lens; the projection lens is used for amplifying the modulation signal to obtain a projection image and projecting the projection image to the directional projection screen; the directional projection screen is arranged at the light emitting end of the projection device; the directional projection screen comprises a harmonic diffraction lens array, wherein the harmonic diffraction lens array is used for converging light rays with different wavelengths to a target viewpoint; the problems that an existing large-format naked eye 3D display device is low in diffraction efficiency and difficult to eliminate influence of zero-order light can be solved; because the harmonic diffraction lens array has higher diffraction efficiency, the harmonic diffraction phase factor of the harmonic diffraction lens array can be designed according to the central wavelength of the optical filter on the spatial light modulator, so that the emergent light with different wavelengths is focused to the same point in space to realize naked eye color 3D display, and the chromatic dispersion can be eliminated; meanwhile, the harmonic diffraction lens array is a continuous surface, the theoretical diffraction efficiency can reach 100%, and the diffraction efficiency can be improved, so that the light energy utilization rate is improved.

The foregoing description is only an overview of the technical solutions of the present application, and in order to make the technical solutions of the present application more clear and clear, and to implement the technical solutions according to the content of the description, the following detailed description is made with reference to the preferred embodiments of the present application and the accompanying drawings.

Drawings

FIG. 1 is a schematic diagram of a collapse process for a harmonic diffractive lens provided by one embodiment of the present application;

FIG. 2 is a top view of a harmonic diffractive lens provided by one embodiment of the present application;

FIG. 3 is a schematic diagram of a thickness comparison of a harmonic diffractive lens provided by one embodiment of the present application with a conventional diffractive element;

FIG. 4 is a cross-sectional view of a sawtooth prism in various harmonic diffractive lens arrays provided by one embodiment of the present application;

FIG. 5 is a schematic structural diagram of a projection type naked eye three-dimensional display device according to an embodiment of the present application;

FIG. 6 is a schematic diagram of light transmission of a projection-type naked-eye three-dimensional display device according to an embodiment of the present application;

FIG. 7 is a schematic diagram of a harmonic diffractive lens array provided by one embodiment of the present application converging light rays to the same viewpoint;

FIG. 8 is a schematic diagram of a harmonic diffractive lens pixelation process provided by one embodiment of the present application;

fig. 9 is a schematic diagram of a multi-view 3D display in a projection-type naked eye three-dimensional display device according to an embodiment of the present application;

fig. 10 is a schematic diagram of multi-view 3D display in a projection-type naked eye three-dimensional display device according to another embodiment of the present application.

Detailed Description

The following detailed description of embodiments of the present application will be described in conjunction with the accompanying drawings and examples. The following examples are intended to illustrate the present application but are not intended to limit the scope of the present application.

It should be noted that the detailed description set forth in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The apparatus embodiments and method embodiments described herein are described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, units, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The terms first, second, etc. in the description and claims of the present application and in the drawings of the specification, if used to describe various elements, are used to distinguish one element from another, and are not used to describe a particular sequence.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It is also to be understood that the terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the specification of the present application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

It should be noted that, unless otherwise specifically indicated, various technical features in the embodiments of the present application may be regarded as being capable of being combined or coupled with each other as long as the combination or coupling is not technically impossible to implement. While certain exemplary, optional, or preferred features may be described in combination with other features in various embodiments of the application for a fuller understanding of the application, such combination is not essential, and it is to be understood that the exemplary, optional, or preferred features and other features may be separable or separable from each other, provided such separation or separation is not technically impractical. Some functional descriptions of technical features in method embodiments may be understood as performing the function, method, or step, and some functional descriptions of technical features in apparatus embodiments may be understood as performing the function, method, or step using the apparatus.

First, several nouns to which the present application relates are explained.

Harmonic Diffractive lens (HDE): the lens is a lens with one plane and the other plane engraved with concentric inclined threads. The inclination angle and the radius of the thread are determined by the requirement of the thread on the position of converging light to a focus, and the harmonic diffraction lens can overcome the influence of dispersion through structural design and converge light with multiple wavelengths to the same point in space.

Since the general diffractive optical element uses +1 order diffracted light, it exhibits large negative dispersion. Based on the problem, the harmonic diffraction lens is designed by utilizing harmonic diffraction theory, compared with the common diffraction which uses +1 order, the design method of harmonic diffraction is to use + m order diffraction light, and the dispersion performance of the harmonic diffraction lens is between the common diffraction and refraction.

The harmonic diffraction lens changes the phase modulation function of the common diffraction element by increasing the etching depth of the surface microstructure of the common diffraction element, so that the phase difference of the harmonic diffraction lens in the adjacent annular zone is equal to integral multiple of 2 pi. By utilizing the characteristics that the theoretical diffraction efficiency of 100 percent can be realized by harmonic diffraction at a plurality of discrete harmonic wavelengths, and different harmonic wavelengths realize the same focal power at different diffraction orders, the idea of realizing harmonic diffraction achromatization in a visible light broadband and realizing multiband common path confocal by applying harmonic diffraction in an optical system is provided. Harmonic diffraction can overcome defocusing of a general diffraction element due to dispersion, has the same optical power in a series of harmonic wavelengths, and can theoretically maintain the diffraction efficiency of 100%. The red R, green G and blue B lights have the same focal power, namely R, G of the same pixel and the B light have the same focal point and are focused at the same position after passing through the linear Fresnel lens, and color 3D display is realized.

Referring to the schematic diagrams of the harmonic diffractive lens shown in fig. 1 and 2, the surface phase distribution of a common spherical lens (the rightmost side) can be a superposition of a plurality of 2 pi, and different phases can cause light rays to be bent to different degrees. And (3) dividing the phase of the lens surface by taking 2 pi as a unit, then collapsing, removing the phase of integral multiple of 2 pi to leave remainder, wherein the remainder is distributed in a range of 0-2 pi, and finally forming a concentric ring.

According to harmonic diffraction theory, the harmonic wavelength satisfies the following formula:

wherein λ is₀To design the wavelength, λ is the center wavelength of the actual incident light, p is the phase factor of the harmonic diffraction, and m is the diffraction order. By reasonably designing p and m, incident light beams emitted by the sub-pixels (R, G and B) with three different wavelengths are ensured to be subjected to harmonicThe diffraction lens can obtain higher diffraction efficiency.

The order of the steps corresponds to the diffraction efficiency:

λ₀to design the wavelength, λ is the center wavelength of the actual incident light, p is the phase factor of the harmonic diffraction, and m is the diffraction order. According to the above formula, the diffraction efficiency is higher as the number of steps is larger, and the number of steps of the continuous interface tends to be infinite, so that the diffraction efficiency approaches 100%.

The height of the harmonic diffraction lens designed according to the harmonic diffraction design method is as follows:

wherein n is the refractive index.

In a cross section, the surface of the harmonic diffraction lens is composed of a series of sawtooth prisms (sawtooth gratings or blazed annuluses), and the central part of the harmonic diffraction lens is an elliptic arc. Each prism has a different angle from the adjacent prism, but concentrates the light to a point where it forms the central focal point, i.e., the focal point of the lens, and the height of the prism is related to the design wavelength. If the collapse unit of the prism is P x 2 pi, the radii of all concentric circles are correspondingly enlarged simultaneously, and the height of the prism is also enlarged P times simultaneously, but the focal length is still unchanged.

The energy distribution at the focal plane of the diffractive lens can be seen as a result of interference of light rays at the focal plane after passing through the respective sawtooth prisms. If the wavelength of the light is λ, the focal length is:

wherein λ is₀To design the wavelength, f₀To design the focal length of the wavelength.

With common derivativesCompared with the transmission lens, the optical path difference between the HDE annular bands is p lambda₀Is not λ₀. Corresponding to a design wavelength of p λ₀Focal length of f₀The special lens of (1). If m-order imaging is performed on light with wavelength λ, the focal length is:

the effective focal length is related to the phase factor p of harmonic diffraction and the diffraction order m. If f is₀If the coefficient of (1) is greater than the first threshold, the focus of the m-th diffraction order coincides with the focus of the designed wavelength, thereby achieving the purpose of eliminating dispersion.

In fig. 3, (a) is the thickness of a normal diffraction element, and (b) is the thickness of a harmonic diffraction lens.

Alternatively, referring to fig. 4, the sawtooth type prism may be a triangular pyramid (a); or, triangular pyramids (b) and (c) in which at least one plane is a curved surface; or a quadrangular frustum pyramid (d) in which at least one plane is a curved surface. The information such as the inclination angle and the depth of the sawtooth prism can be obtained through calculation according to the formula and actual requirements, so that wide-spectrum incident light is modulated through the micro-nano structure on the pixel, and emergent light has certain directivity and directivity.

The prism structure of the harmonic diffraction lens can be prepared by methods such as gray scale photoetching and laser etching, and can be cleaned by ultrasonic to remove redundant residual glue on the surface, and the surface appearance is leveled by adopting a hot baking mode, so that the dispersion caused by structural burrs generated by processing errors is eliminated to the maximum extent.

Optionally, the harmonic diffractive lens comprises a linear fresnel lens.

Fig. 5 is a schematic structural diagram of a projection type naked eye three-dimensional display device according to an embodiment of the present application, and as shown in fig. 5, the projection type naked eye three-dimensional display device at least includes: a projection device 110 and a directional projection screen 120.

The projection device 110 is used to project a projection image. Optionally, a display chip 111 and a projection lens 112 are included, which are sequentially disposed at the light-emitting end of the directional light source. The display chip 111 is used for acquiring an optical signal irradiated by the directional light source; modulating the optical signal and the multi-view image signal to obtain a modulation signal; and outputs the modulated signal to the projection lens 112; the projection lens 112 is configured to amplify the modulation signal to obtain a projection image, and project the projection image to the directional projection screen.

Optionally, the display chip 111 includes a spatial light modulator. The spatial light modulator may be implemented as a polysilicon liquid crystal panel, a silicon-based liquid crystal panel, or a digital mirror. The specific implementation manner can be selected according to practical situations, and the implementation manner of the spatial light modulator is not limited in this embodiment.

The directional projection screen 120 is disposed at the light emitting end of the projection device 110. Directional projection screen 120 includes a harmonic diffractive lens array for converging light rays having different wavelengths to a target viewpoint.

Referring to the light transmission diagram of the projection type naked eye three-dimensional display device shown in fig. 6, light is incident on the harmonic diffraction lens array from the projection device 110, and is modulated by the harmonic diffraction lens to form a plurality of observation viewpoints in the observation space.

The harmonic diffraction lens array comprises a plurality of pixel units, each pixel unit is a harmonic diffraction lens or a part of a harmonic diffraction lens, and each pixel unit is used for converging received light rays with different wavelengths to a target viewpoint.

Alternatively, the phase factor of the harmonic diffraction lens array can be determined according to the central wavelength of the filter on the liquid crystal panel, and the phase factor of the harmonic diffraction and the central wavelength of the lens are designed to enable the emergent light with the three wavelengths of RGB on the liquid crystal panel to be focused to the same point in space, and the diffraction efficiency is high.

Alternatively, referring to fig. 7, the plurality of pixel units have different periods and different orientations so that incident light rays having different wavelengths are converged to corresponding target viewpoints. Since the parallax image is observed only at the viewpoint position in the observation space, the parallax image is not observed at another position. To enlarge the viewing field, the parallax image can be converged to a plurality of target viewpoints by pixelating the harmonic diffractive lens. Since the spatial position of the target viewpoint corresponds to the central position of the harmonic diffraction lens, the parallax image can be converged to a plurality of target viewpoints by designing the coordinates of the central points of different harmonic diffraction lenses.

In one example, the number of target viewpoints is n; the n pixel units form a volume pixel, the n pixel units in each volume pixel correspond to the n target viewpoints one by one, and n is a positive integer.

Referring to the pixelation process of the harmonic diffraction lens shown in fig. 8, if the number of target viewpoints is n (n is 4 in fig. 8, and n is a positive integer in actual implementation), the n harmonic diffraction lenses are divided into m parts (m is a positive integer), and the central positions of the n harmonic diffraction lenses correspond to the spatial positions of the n target viewpoints one by one; a portion of the n harmonic diffractive lenses collectively make up a volume pixel 81. At this time, if a bundle of parallel light is incident into the volume pixel 81, n target viewpoints will be formed in the free space range. That is, the n pixel units of the harmonic diffraction lens constitute one volume pixel, and the n pixel units in each volume pixel correspond one-to-one to the n target viewpoints.

If a single harmonic diffractive lens is divided into more parts, there will be correspondingly more voxels, and the parallax image will have a higher resolution.

If the number of the harmonic diffraction lenses is increased, more viewpoints are formed in the space, more parallax images are gathered to the spatial viewpoint positions, the viewing angle range of the observation is increased, and the amount of parallax information is increased.

Optionally, the n sections in each harmonic diffractive lens are equally divided.

Alternatively, the n pixel units in each volume pixel 81 have different periods and different orientations so that incident light rays having different wavelengths are converged to the corresponding target viewpoints.

The positions of the plurality of sub-pixels in the projection device 110 correspond to the positions of the plurality of pixel units in the volume pixel 81 one by one.

In one example, a plurality of pixel units are closely arranged; and/or a plurality of volume pixels are closely arranged.

See fig. 9 for a schematic diagram of a pixelated harmonic diffractive lens array implementing multiple viewpoints. In fig. 9, the number of target viewpoints is 4 for illustration, and each of the volume pixels of the harmonic diffractive lens array has four sub-pixels, and each of the sub-pixels can focus the outgoing light to a corresponding target viewpoint position. As shown in fig. 10, the light transmitted through the spatial light modulator 120 is changed in direction after passing through the harmonic diffraction lens, information corresponding to the number 1 is focused at the viewpoint 1, and information of other numbers is focused at the viewpoint positions of the corresponding numbers. Different parallax images generated by live-action shooting or computer software synthesis are focused to each viewpoint position, and different parallax images can be observed when human eyes are positioned at different spatial positions, so that the naked eye 3D effect is realized.

In another example, a plurality of pixel cells have a light-transmissive medium therebetween; and/or a light-transmitting medium is arranged among a plurality of volume pixels. Namely, a plurality of pixel units are sparsely arranged; and/or a plurality of volume pixels are sparsely arranged.

See fig. 10 for a schematic diagram of a pixelated harmonic diffractive lens array implementing multiple viewpoints. In fig. 10, the number of target viewpoints is 4 for illustration, and each of the volume pixels of the harmonic diffractive lens array has four sub-pixels, and each of the sub-pixels can focus the outgoing light to a corresponding target viewpoint position. As shown in fig. 10, the light transmitted through the spatial light modulator 120 is changed in direction after passing through the harmonic diffraction lens, information corresponding to the number 1 is focused at the viewpoint 1, and information of other numbers is focused at the viewpoint positions of the corresponding numbers. Different parallax images generated by live-action shooting or computer software synthesis are focused to each viewpoint position, and different parallax images can be observed when human eyes are positioned at different spatial positions, so that the naked eye 3D effect is realized. Meanwhile, the area without the pixel unit is a light-transmitting medium, so that a real object behind the harmonic diffraction lens screen can be directly transmitted, and a virtual-real fusion 3D display effect of fusion of virtual objects and the real object is realized.

In summary, the projection-type naked-eye three-dimensional display device provided in this embodiment includes, by providing the projection device, a display chip and a projection lens sequentially disposed at the light-emitting end of the directional light source; the display chip is used for acquiring an optical signal irradiated by the directional light source; modulating the optical signal and the multi-view image signal to obtain a modulation signal; and outputting the modulation signal to a projection lens; the projection lens is used for amplifying the modulation signal to obtain a projection image and projecting the projection image to the directional projection screen; the directional projection screen is arranged at the light emitting end of the projection device; the directional projection screen comprises a harmonic diffraction lens array, wherein the harmonic diffraction lens array is used for converging light rays with different wavelengths to a target viewpoint; the problems that an existing large-format naked eye 3D display device is low in diffraction efficiency and difficult to eliminate influence of zero-order light can be solved; because the harmonic diffraction lens array has higher diffraction efficiency, the harmonic diffraction phase factor of the harmonic diffraction lens array can be designed according to the central wavelength of the optical filter on the spatial light modulator, so that the emergent light with different wavelengths is focused to the same point in space to realize naked eye color 3D display, and the chromatic dispersion can be eliminated; meanwhile, the harmonic diffraction lens array is a continuous surface, the theoretical diffraction efficiency can reach 100%, and the diffraction efficiency can be improved, so that the light energy utilization rate is improved.

In addition, one pixel unit in the harmonic diffraction lens array can focus emergent light with different wavelengths to the same point in space, so that different diffraction structures do not need to be designed for light with different wavelengths, and the structure of the three-dimensional display device can be simplified.

In addition, the harmonic diffraction lens can be industrially produced by the existing nanoimprint technology, the manufacturing process is mature, and the production difficulty is low.

In addition, the harmonic diffraction lenses are arranged sparsely, and real objects behind the screen of the harmonic diffraction lenses directly penetrate through the harmonic diffraction lenses, so that a virtual-real fusion 3D display effect that virtual objects and real objects are fused is achieved.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.