阅读说明：本技术 一种基于相位延迟部件的投影系统 (Projection system based on phase delay component ) 是由 吴尚亮 陈俊逸 谢前森 于 2020-06-04 设计创作，主要内容包括：本发明涉及一种投影系统,包括：光源阵列,用于发出用于投影的光；以及光调制元件,位于光源阵列发出的光的光路上,用于调制光源阵列发出的光,其中,光调制元件包括：由透明材料或半透明材料形成的基底；以及在基底上形成的DOE阵列,该DOE阵列包括不同形状构造的相位延迟部件,用于对入射的光产生不同的相位延迟,从而投影出图案。(The invention relates to a projection system comprising: a light source array for emitting light for projection; and a light modulation element, located on a light path of the light emitted from the light source array, for modulating the light emitted from the light source array, wherein the light modulation element includes: a substrate formed of a transparent material or a translucent material; and a DOE array formed on the substrate, the DOE array including phase retarding members of different shape configurations for imparting different phase retardations to incident light, thereby projecting a pattern.)

1. A projection system, comprising:

a light source array for emitting light for projection; and

a light modulation element positioned on a light path of the light emitted from the light source array for modulating the light emitted from the light source array,

characterized in that the light modulation element comprises:

a substrate formed of a transparent material or a translucent material; and

a DOE array formed on the substrate, the DOE array including differently shaped structured phase retarding components for imparting different phase retardations to incident light, thereby projecting a pattern.

2. The projection system of claim 1, wherein the phase delay component comprises greater than or equal to 8 different shape configurations.

3. The projection system of claim 2, wherein the shape configuration comprises one or more of a square or a cylinder of unequal size.

4. The projection system of claim 2 or 3, wherein the phase retarding component in the DOE array is such that the incident light contains eight or more phase gradients within a 0-2 π light phase period.

5. The projection system of claim 1, wherein the light from the array of light sources comprises light having two polarization states, the projection system further comprising:

an adjustable polarization element positioned between the light source array and the light modulation element for changing the polarization state of the light emitted by the light source array,

wherein the phase retardation component of the light modulation element causes different phase retardation of light emitted through the adjustable polarization element, thereby projecting two patterns.

6. The projection system of claim 5, wherein the single one of the shape structures is formed to exhibit different phases for light of different polarization states, thereby imparting different phase delays to light of different polarization states.

7. The projection system of claim 1, wherein the light from the light source array comprises light having two wavelengths, and wherein the phase retarding component of the light modulating element causes the two different wavelengths of light to be phase retarded differently to project two patterns.

8. A method of forming a projection system, the projection system comprising: a light source array for emitting light for projection, and a light modulation element positioned on an optical path of the light emitted from the light source array for modulating the light emitted from the light source array, the method comprising:

forming a substrate of the light modulation element from a transparent material or a translucent material;

forming a DOE array comprising differently shaped configured phase delay elements on the substrate, comprising:

selecting the number of phase gradients in an optical phase period of 0-2 pi;

selecting the shape of the phase delay member according to the number of desired projection patterns or the wavelength or polarization state of the received light;

reversely deducing required phases of different positions on the DOE surface according to Fresnel holographic theory based on the required projection pattern, the wavelength or polarization state of the incident light and the distance from the projection pattern to the DOE;

based on the deduced phase required for different positions of the DOE surface, a shape of a phase delay element having a corresponding phase is formed at the corresponding position.

9. The method of claim 8, wherein the step of selecting the shape of the phase retarding component based on the number of desired projected patterns or the wavelength or polarization state of the received light comprises:

when a pattern is projected, the shape of the phase delay section is one or more of a square or a cylinder having different sizes.

10. The method of claim 8, wherein the step of selecting the shape of the phase retarding component based on the number of desired projected patterns or the wavelength or polarization state of the received light comprises:

when two patterns are projected, the shape of the phase delay member is one or more of a rectangular shape, an elliptical shape, and a cross shape having different sizes.

Technical Field

The invention relates to a vehicle-mounted projection system, in particular to a projection system based on a phase delay component.

Background

Different patterns need to be projected at a distance in vehicle-mounted application, and communication between drivers and passengers is facilitated. The traditional vehicle-mounted projection pattern solution consists of films. However, the common film scheme can only project one pattern, and needs a plurality of lenses to be combined, so that the overall length of the system is long; although the double-sided microlens array scheme can realize compact and small-volume vehicle-mounted projection, the projection pattern can still be only one.

With the development of vehicle-mounted projection systems, people have made higher and higher demands on the miniaturization and the dynamism of projection schemes. In order to reduce the length of the whole system, we adopt a phase delay component scheme. The length of the whole projection system can be greatly reduced by utilizing the scheme of the phase delay component, and the optical energy utilization rate is high. In order to increase the functionality of the projection system, it is desirable that the projection system can project different patterns as much as possible in a dynamically adjustable manner. Based on this requirement, we propose a dynamic projection system solution based on DOE (Diffractive Optical Elements).

The scheme can realize the switching of two projection patterns and can greatly reduce the volume of the projection system.

Disclosure of Invention

Therefore, the projection system can reduce the length of the whole projection system, has the characteristics of high light energy utilization rate and the like, and further can realize the switching of two projection patterns and greatly reduce the volume of the projection system.

One aspect of the present application provides a projection system comprising: a light source array for emitting light for projection; and a light modulation element, located on a light path of light emitted from the light source array, for modulating the light emitted from the light source array, wherein the light modulation element includes: a substrate formed of a transparent material or a translucent material; and a DOE array formed on the substrate, the DOE array including phase retarding members of different shape configurations for imparting different phase retardations to incident light, thereby projecting a pattern.

In one embodiment, a phase delay element in a DOE array of a projection system includes greater than or equal to 8 different shape configurations.

In one embodiment, the shape configuration of the phase delay elements in the DOE array of the projection system includes one or more of squares or cylinders of unequal size.

In one embodiment, the phase retarding component in the DOE array of the projection system is such that the incident light contains eight or more phase gradients within a 0-2 π light phase period.

In one embodiment, the phase gradients of eight or more phase delay elements in the DOE array of the projection system are uniformly discrete.

Another aspect of the present application provides a projection system comprising: an array of light sources emitting light comprising light having two polarization states; the light modulation element is positioned on a light path of the light emitted by the light source array and is used for modulating the light emitted by the light source array; and an adjustable polarization element, located between the light source array and the light modulation element, for changing the polarization state of the light emitted by the light source array, wherein the light modulation element comprises: a substrate formed of a transparent material or a translucent material; and a DOE array formed on the substrate, the DOE array comprising phase retarding components of different shape configurations, the phase retarding components causing different phase retardations of light emitted by the adjustable polarizing element, thereby projecting two patterns.

In one embodiment, a phase delay element in a DOE array of a projection system includes greater than or equal to 64 different shape configurations.

In one embodiment, a single configuration of the shape configuration of the phase retarding components in the DOE array of the projection system is formed to exhibit different phases for different polarization states of light, thereby imparting different phase retardations to the different polarization states of light.

In one embodiment, the shape configuration of the phase delay elements in the DOE array of the projection system includes one or more of oblong, elliptical, and cross-shaped shapes of varying sizes.

In one embodiment, the phase retarding component in the DOE array of the projection system is such that incident light of each polarization state contains eight or more phase gradients within a phase period of 0-2 π light.

In one embodiment, the phase gradients of eight or more phase delay elements in the DOE array of the projection system are uniformly discrete.

Yet another aspect of the present application provides a projection system comprising: a light source array emitting light including light having two wavelengths; and a light modulation element, located on a light path of light emitted from the light source array, for modulating the light emitted from the light source array, wherein the light modulation element includes: a substrate formed of a transparent material or a translucent material; and a DOE array formed on the substrate, the DOE array including phase retarding members of different shape configurations, the phase retarding members causing different phase retardations of the two different wavelengths of light, thereby projecting the two patterns.

In one embodiment, the phase delay element of the projection system includes greater than or equal to 64 different shape configurations.

In one embodiment, a single configuration of the shape configuration of the phase retarding components in the DOE array of the projection system is formed to exhibit different phases for different wavelengths of light, thereby imparting different phase delays to the different wavelengths of light.

In one embodiment, the shape configuration of the phase delay elements in the DOE array of the projection system includes one or more of oblong, elliptical, and cross-shaped shapes of varying sizes.

In one embodiment, the phase retarding component in the DOE array of the projection system is such that each wavelength of incident light contains eight or more phase gradients within a 0-2 π light phase period.

In one embodiment, the phase gradients of eight or more phase delay elements in the DOE array of the projection system are uniformly discrete.

In one embodiment, the differently shaped materials forming the DOE array in the projection system are dielectric materials.

In one embodiment, the differently shaped configurations of the dielectric material of which the projection system forms an array of DOEs include at least one of TiO2 and Si.

In one embodiment, the material in the projection system that forms the different shape configurations of the DOE array is a metallic material.

In one embodiment, the differently shaped configurations of the metallic material of which the projection system forms the DOE array include at least one of Au and Ag.

Yet another aspect of the present application provides a method of forming a projection system, the projection system comprising: a light source array for emitting light for projection, and a light modulation element located on an optical path of the light emitted from the light source array for modulating the light emitted from the light source array, wherein the method comprises: forming a substrate of the light modulation element from a transparent material or a translucent material; forming a DOE array comprising differently shaped configured phase delay elements on a substrate, comprising: selecting the number of phase gradients in an optical phase period of 0-2 pi; selecting the shape of the phase delay member according to the number of desired projection patterns or the wavelength or polarization state of the received light; based on the required projection pattern, the wavelength or polarization state of incident light and the distance between the projection pattern and the DOE, reversely deducing phases required by different positions on the DOE surface according to a Fresnel holographic theory; based on the phase required for different positions of the surface of the DOE, which is inversely deduced, the shape of the phase delay element having the corresponding phase is formed at the corresponding position.

In one embodiment, the method of forming a projection system has eight phase gradients within a 0-2 π light phase period.

In one embodiment, the method of forming a projection system has a plurality of phase gradients uniformly dispersed over a 0-2 π light phase period.

In one embodiment, the step of selecting the shape of the phase delay member according to the number of desired projection patterns or the wavelength or polarization state of the received light of the method of forming a projection system includes: when a pattern is projected, the shape of the phase delay section is one or more of a square or a cylinder having different sizes.

In one embodiment, the step of selecting the shape of the phase delay member according to the number of desired projection patterns or the wavelength or polarization state of the received light of the method of forming a projection system includes: when two patterns are projected, the shape of the phase delay member is one or more of a rectangular shape, an elliptical shape, and a cross shape having different sizes.

In one embodiment, the method of forming a projection system includes greater than or equal to 8 different shapes for the phase delay element when projecting a pattern.

In one embodiment, the method of forming a projection system, when projecting two patterns, the phase delay element comprises greater than or equal to 64 different shapes.

This application not only can reduce entire system's length through being applied to on-vehicle projection system with the DOE array, can also provide entire system's light energy utilization rate. And through carrying out rational design with the phase delay part on DOE array surface to the light of different wavelength or the light of different polarization states, realized the dynamic adjustment to the pattern of projection to can throw out different patterns as required, can make things convenient for the middle interchange of driver passenger.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of a phase delay component of a DOE implementing projection according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a projection system according to an embodiment of the present application;

FIG. 3 is a diagram of a pattern projected by the projection system;

FIG. 4 is a schematic diagram of a phase delay component of a DOE implementing dynamic projection according to another embodiment of the present application;

FIG. 5 is a schematic diagram of a projection system implementing dynamic projection according to an embodiment of the present application;

FIG. 6 is a projected pattern of light of a first polarization state for a dynamic projection system;

FIG. 7 is a projected pattern of light of a second polarization state for a dynamic projection system;

FIG. 8 is a schematic diagram of a phase delay component of a DOE implementing dynamic projection according to yet another embodiment of the present application;

FIG. 9 is a schematic diagram of a projection system implementing dynamic projection according to an embodiment of the present application;

FIG. 10 is a projected pattern of light at a first wavelength for a dynamic projection system;

FIG. 11 is a pattern projected by light of a second wavelength for a dynamic projection system.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that the expressions first, second, etc. in this specification are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, a first material discussed below may also be referred to as a second material without departing from the teachings of the present application.

In the drawings, the thickness, size, and shape of each component may have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.

It will be further understood that the terms "comprises," "comprising," "has," "having," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears in the list of listed features, that statement modifies all features in the list rather than merely individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Additionally, the word "exemplary" is intended to mean exemplary or illustrative.

As used herein, the terms "approximately," "about," and the like are used as words of table approximation and not as words of table degree, and are intended to account for inherent deviations in measured or calculated values that can be appreciated by one of ordinary skill in the art.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In addition, the embodiments and features of the embodiments in the present application may be combined with each other without conflict. In addition, unless explicitly defined or contradicted by context, the specific steps included in the methods described herein are not necessarily limited to the order described, but can be performed in any order or in parallel. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

In order to realize a small-size vehicle-mounted projection system, the application provides a projection system.

Referring to the drawings, FIG. 2 is a schematic diagram of a projection system according to an embodiment of the present application, FIG. 1 is a schematic diagram of a phase retardation component of a DOE for use in the projection system of FIG. 2 to effect projection, and FIG. 3 is a pattern projected by the projection system.

As shown, a projection system according to an embodiment of the present application may include: a light source array 11 for emitting light for projection; and a light modulation element 12, which is located on an optical path of the light emitted from the light source array 11, for modulating the light emitted from the light source array 11. The light modulation element includes a substrate 121 formed of a transparent material or a translucent material; and a DOE array formed on the substrate, the DOE array including phase retarding members 122 of different shape configurations for imparting different phase retardations to incident light, thereby projecting a pattern. Specifically, the phase delay unit 122 is determined by calculating a phase profile required for different positions of the DOE by using a fresnel holography program of Matlab, based on the projection distance of the projection system, the incident light parameter of the light source array 11 (in the present embodiment, the wavelength of the light source array 11), and a projection pattern (in the present embodiment, the pattern shown in fig. 3) to be obtained. The DOE array is used to modulate the phase of the light emitted from the light source array 11, so that when the light is incident on the DOE array, the different phase delay components 122 can exhibit different phases to the light, thereby generating different phase delays and projecting the required pattern as shown in fig. 3. Therefore, compared to the prior art in which a pattern is projected using a film in cooperation with a plurality of lenses, the projection system according to the present embodiment achieves a reduction in size by employing the DOE array.

The determination step of the phase delay element 122 on the surface of the DOE array is detailed below:

step 1, selecting the type of phase delay components contained in the DOE surface: in order to better reproduce the projection pattern, the DOE surface optionally comprises eight phase gradients in the optical phase period of 0-2 pi. When a pattern is projected according to this embodiment, the required retardation elements can be square or quasi-square such as circle, and the corresponding retardation element types (in this embodiment, the size of the circle) included in the surface of the DOE should be greater than or equal to 8, so as to correspond to the eight phase gradients included in the optical phase period of 0-2 pi.

Step 2, determining phases required by different positions of the DOE surface: based on the pattern required for projection, as shown in fig. 3, the wavelength of the incident light emitted from the light source array 11, and the distance from the projection pattern of the projection system to the DOE array, the phase required by the phase delay elements arranged at different positions on the DOE surface is reversely deduced according to the fresnel hologram. The phase derived from the projection pattern is uniformly dispersed between 0 and 2 pi, the dispersion number is more than or equal to 8, and when the dispersion number is 8, for example, the dispersed phase is pi/4, 2 pi/4, 3 pi/4, …, 8 pi/4.

Step 3, determining phase delay components on all positions of the DOE surface: according to the phases required by different positions of the DOE surface reversely deduced in the step 2, the phase delay components with corresponding phases in the step 1 are selected and placed corresponding to one of the phase delay components, and the exemplary effect is shown in fig. 1.

Referring to fig. 1, it can be seen that the structure of the DOE array is formed by cylinders of different radii. The radius of each cylinder is obtained by screening according to the steps through a finite time domain difference algorithm, so that the incident light emitted by the light source array 11 can delay different phases after passing through structures with different radii. A total of 8 structures are selected, namely the 8 structures respectively correspond to eight gradient phases in the range of 0-2 pi. The details are shown in table 1 below:

structure 1

Structure 2

Structure 3

…

Structure 7

Structure 8

Phase delay

π/4

2π/4

3π/4

…

7π/4

8π/4

TABLE 1

According to the embodiment of the present application, the material of the phase delay element of the DOE array may be a dielectric material such as TiO2, Si, or the like.

According to an embodiment of the present application, a material of the phase delay element of the DOE array may be a metal material such as Au, Ag, or the like.

In order to realize a dynamic vehicle-mounted projection system with a small volume, the application provides a projection system.

Referring to the drawings, fig. 5 is a schematic structural diagram of a projection system implementing dynamic projection, fig. 4 is a schematic diagram of a phase retardation component of a DOE used in the projection system of fig. 5 to implement dynamic projection, fig. 6 is a projected pattern of light of a first polarization state of the dynamic projection system, and fig. 7 is a projected pattern of light of a second polarization state of the dynamic projection system, according to an embodiment of the present application.

As shown, the dynamic projection system of fig. 5 includes: a light source array 21, the light emitted by the light source array 21 including light having two polarization states; a light modulation element 22, which is located on the optical path of the light emitted from the light source array, and modulates the light emitted from the light source array; and an adjustable polarization element, located between the light source array 21 and the light modulation element 22, for changing the polarization state of the light emitted by the light source array, wherein the light modulation element 22 includes: a substrate 221 formed of a transparent material or a translucent material; and a DOE array formed on the substrate 221, the DOE array including phase retarding members 222 of different shapes, the phase retarding members 222 causing different phase retardations of light emitted through the adjustable polarizing element, thereby projecting two patterns. Specifically, the phase delay unit 222 is determined by calculating a phase distribution map required for different positions of the DOE by using a fresnel holography program of Matlab, according to the projection distance of the projection system, the incident light parameters (in the present embodiment, the wavelength of the light source array 21, and the polarization state of the light after passing through the adjustable polarization element 23, that is, the first polarization state and the second polarization state), and a projection pattern (in the present embodiment, the pattern shown in fig. 6 and 7) to be obtained. The DOE array is used to modulate the phase of the light emitted from the adjustable polarization element, so that after the light is incident on the DOE array, different phase retardation components 222 can exhibit different phases for the light, and different phase retardations can be generated, and a single phase retardation component 222 can exhibit different phases for the light in different polarization states, so that the light in different polarization states can generate different phase retardations. This way a light having a first polarization state may carry a phase distribution as the projected picture 6 when passing through the structure and a light having a second polarization state may carry a phase distribution as the projected picture 7 when passing through the structure. By dynamically controlling the rotation direction of the adjustable polarization element 23 in the dynamic projection system of the present embodiment to control the polarization incident on the DOE array, it is possible to realize real-time switching of the projection pattern 6 and the projection pattern 7. Thus, the projection system according to the present embodiment achieves volume miniaturization by employing the DOE array, and achieves dynamic projection by allowing light of the first polarization state to project a pattern as shown in fig. 6 and light of the second polarization state to project a pattern as shown in fig. 7.

The determination of the phase delay element 222 on the surface of the DOE array is detailed below:

step 1, selecting the type of phase delay components contained in the DOE surface: for better reproduction of the projection pattern, the DOE surface should contain eight phase gradients within the optical phase period of 0-2 π. When two vertical polarization states of incident light with the same wavelength are required to correspond to different patterns according to the embodiment, the phase delay component is in a quasi-rectangular shape such as a rectangle or an ellipse, that is, the two vertical polarization states respectively correspond to the length, the width or the length and the short axis of the phase delay component; that is to say: the length and width of the rectangle correspond to different phases, and the major and minor axes of the quasi-rectangle such as the ellipse correspond to different phases, so that the single phase delay component can show different phases under different polarization states; the types of the phase delay components included in the surfaces of the corresponding DOEs are greater than or equal to 64, so that the incident light in two polarization states respectively corresponds to eight phase gradients included in an optical phase period of 0-2 pi.

Step 2, determining phases required by different positions of the DOE surface: based on the patterns shown in fig. 6 and 7 required by projection, the wavelength of the incident light emitted from the light source array 21, the polarization state of the light after passing through the adjustable polarization element 22, and the distance from the projection pattern to the DOE, the phase required by the phase retardation components arranged at different positions on the DOE surface is reversely deduced according to the fresnel hologram. It should be noted that: the phase derived from the projection graph is uniformly dispersed between 0 pi and 2 pi, the dispersion number is more than or equal to 8, and when the dispersion number is 8, the dispersed phase is pi/4, 2 pi/4, 3 pi/4, … and 8 pi/4.

Step 3, determining phase delay components on all positions of the DOE surface: according to the phases required by different positions of the DOE surface reversely deduced in step 2, the phase delay components with corresponding phases in step 1 are selected and placed corresponding to one of the phase delay components, and an exemplary effect is shown in fig. 4.

Referring to fig. 4, it can be seen that the structure in the figure consists of elliptical columns with different major and minor axes. The height of the elliptic cylinder can be selected within 400-800 nm, and the short axis of the elliptic cylinder can be selected within 100-450 nm. And each parameter of each elliptic cylinder is respectively optimized by the phase delay of the light which is obtained by scanning the light in the first polarization state and the light in the second polarization state through the structure by a finite time domain difference algorithm. In total, 64 structures are preferred, namely 8 × 8 structures. Of these 64 configurations, there are eight gradients of phase retardation for light of the first polarization state and eight gradients of phase retardation for light of the second polarization state. The phase retardation for different polarized light is shown in table 2 below:

structure 1_1

Structure 1_2

Structure 1_3

…

Structure 1_7

Structure 1_8

First polarization phase retardation

π/4

π/4

π/4

…

π/4

π/4

Second polarization phase retardation

π/4

2π/4

3π/4

…

7π/4

8π/4

Structure 2_1

Structure 2_2

Structure 2_3

…

Structure 2_7

Structure 2_8

First polarization phase retardation

2π/4

2π/4

2π/4

…

2π/4

2π/4

Second polarization phase retardation

π/4

2π/4

3π/4

…

7π/4

8π/4

…

…

…

…

…

…

…

Structure 8_1

Structure 8_2

Structure 8_3

…

Structure 8_7

Structure 8_8

First polarization phase retardation

8π/4

8π/4

8π/4

…

8π/4

8π/4

Second polarization phase retardation

π/4

2π/4

3π/4

…

7π/4

8π/4

TABLE 2

According to the embodiment of the present application, the material of the phase delay element of the DOE array may be a dielectric material such as TiO2, Si, or the like.

According to an embodiment of the present application, a material of the phase delay element of the DOE array may be a metal material such as Au, Ag, or the like.

In order to realize a dynamic vehicle-mounted projection system with small volume, the application provides another projection system.

Referring to the drawings, fig. 9 is a schematic structural diagram of a projection system implementing dynamic projection, fig. 8 is a schematic diagram of a phase delay element of a DOE for use in the projection system of fig. 9 to implement dynamic projection, fig. 10 is a projected pattern of light of a first wavelength of the dynamic projection system, and fig. 11 is a projected pattern of light of a second wavelength of the dynamic projection system, according to an embodiment of the present application.

As shown, the dynamic projection system of fig. 9 includes: a light source array 31 that emits light including light having two wavelengths; and a light modulation element 32, located on an optical path of light emitted from the light source array, for modulating the light emitted from the light source array, wherein the light modulation element includes: a substrate 321 formed of a transparent material or a translucent material; and a DOE array formed on the substrate 321, the DOE array including phase retarding members 322 of different shapes, the phase retarding members 322 causing different phase retardations of the two different wavelengths of light, thereby projecting two patterns. Specifically, the phase delay unit 322 is determined by calculating a phase profile required for different positions of the DOE by using the Matlab fresnel holography program according to the projection distance of the projection system, the incident light parameters (in the present embodiment, the wavelengths of the light source array 31, i.e., the first wavelength and the second wavelength), and the projection pattern (in the present embodiment, the patterns shown in fig. 10 and 11) to be obtained. The DOE array is used to modulate the phase of the light with different wavelengths emitted from the light source array, so that when the light is incident on the DOE array, different phase delay components 322 can exhibit different phases for the light, which can generate different phase delays, and a single phase delay component 322 can exhibit different phases for the light with different wavelengths, thereby generating different phase delays for the light with different wavelengths. This way a phase distribution with e.g. the projected picture 10 is carried when light with a first wavelength passes through the structure and a phase distribution with the projected picture 11 is carried when light with a second wavelength passes through the structure. By dynamically controlling the wavelength of the light source array 31 in the dynamic projection system of the present embodiment to control the wavelength incident on the DOE array, it is possible to realize real-time switching between the projection pattern 10 and the projection pattern 11. Thus, the projection system according to the present embodiment achieves volume miniaturization by employing the DOE array, and achieves dynamic projection by allowing light of the first wavelength to project a pattern shown in fig. 10 and light of the second wavelength to project a pattern shown in fig. 11.

The determination of phase delay element 322 on the surface of the DOE array is detailed below:

step 1, selecting the type of phase delay components contained in the DOE surface: for better reproduction of the projection pattern, it is preferable that the DOE surface should contain eight phase gradients within an optical phase period of 0-2 π. When the incident light with two wavelengths is required to correspond to different patterns according to the present embodiment, the shape of the phase delay member is not limited, but different phase information is required to be provided at different wavelengths, so that a single phase delay member can exhibit different phases at different wavelengths; the types of the phase delay components included in the surfaces of the corresponding DOEs are greater than or equal to 64, so that the incident light with two wavelengths respectively corresponds to eight phase gradients included in an optical phase period of 0-2 pi.

Step 2, determining phases required by different positions of the DOE surface: based on the patterns shown in fig. 10 and 11 required for projection, the different wavelengths of the incident light emitted from the light source array 31 and the distances from the DOE to the projection patterns reversely deduce the required phases of the phase delay elements arranged at different positions on the DOE surface according to the fresnel hologram. It should be noted that: the phase derived from the projection graph is uniformly dispersed between 0 pi and 2 pi, the dispersion number is more than or equal to 8, and when the dispersion number is 8, the dispersed phase is pi/4, 2 pi/4, 3 pi/4, … and 8 pi/4.

Step 3, determining phase delay components on all positions of the DOE surface: according to the phases required by different positions of the DOE surface reversely deduced in step 2, the phase delay components with corresponding phases in step 1 are selected and placed corresponding to one of the phase delay components, and an exemplary effect is shown in fig. 8.

Referring to fig. 8, it can be seen that the structure in the figure is formed of square columns of different length on a side. The height range of the square pillar can be selected within 200-800 nm, and the side length range of the square pillar can be selected within 80-600 nm. The parameters of each square are preferably selected by the finite time domain difference algorithm scanning the phase delay of the light with the first wavelength and the second wavelength after passing through the structure. In total, 64 structures are preferred, namely 8 × 8 structures. Of these 64 configurations, there are eight gradients of phase retardation for the first wavelength and eight gradients of phase retardation for the second wavelength. The phase delays for wavelength light are shown in table 3 below:

TABLE 3

According to the embodiment of the present application, the material of the phase delay element of the DOE array may be a dielectric material such as TiO2, Si, or the like.

According to an embodiment of the present application, a material of the phase delay element of the DOE array may be a metal material such as Au, Ag, or the like.

The above description is only an embodiment of the present application and an illustration of the technical principles applied. It will be appreciated by a person skilled in the art that the scope of protection covered by the present application is not limited to the embodiments with a specific combination of the features described above, but also covers other embodiments with any combination of the features described above or their equivalents without departing from the technical idea. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.