Volume holographic optical diffusion element and its manufacturing method and device

Abstract

This solution discloses a volume holographic optical diffusion element and its manufacturing method and device. By adding a first lens assembly between a first diffusion element and a holographic photosensitive material, the first lens assembly is used to project the real image of the first diffusion element onto the holographic photosensitive material layer. Due to the limited entrance pupil diameter of the first lens assembly, only light within a certain angle range of the light emitted by the random point light source generated when the signal light illuminates the first diffusion element can pass through the first lens assembly, resulting in a limited divergence angle for the light projected behind the real image of the holographic photosensitive material layer. Accordingly, the reproduced signal light generated during the display process also has a limited divergence angle, which not only meets the diffusion requirement that all real image points can enter the human eye, but also avoids the waste of light energy caused by excessive diffusion, thereby improving light energy utilization, increasing display brightness, and reducing device energy consumption, and has great practical value.

Description

Technical Field

[0001] The present invention belongs to the field of display technology, and specifically relates to a volume holographic optical diffusion element and a manufacturing method and device thereof. Background Art

[0002] Head-up display (HUD) technology projects driving information, such as the car's instrument panel and navigation system, onto the windshield. This information is then reflected off the windshield and enters the human eye, allowing passengers to see the instrument panel, navigation system, and other driving information through the windshield, thus avoiding safety hazards caused by the driver having to look down at driving information while the car is driving.

[0003] Projected head-up display technology uses a projector to project a real image of driving information onto a specially designed windshield. The windshield diffuses the light, allowing all image points to enter the human eye, allowing passengers to see the real image of the driving information on the windshield. To achieve this, an optical diffusion film is applied to the windshield to further diffuse the projected image light, giving it a wider divergence angle. For example, frosted glass can be used as a diffusion film. The random microparticles on its surface diffuse the projected image light in all directions, making the real image visible from all directions.

[0004] The characteristic of frosted glass is that all light that hits its surface will be diffused into the entire space, which means that it cannot be used directly to make windshields. Using volume holography technology, it is possible to create a diffusion film that only diffuses light within a specific range of incident angles. For example, frosted glass can be used as a template to generate a volume hologram. The frosted glass can be attached to a photosensitive material to replicate the diffusion characteristics of the frosted glass into the volume hologram. Figure 1 As shown in the example exposure process, when a laser beam strikes frosted glass, it is randomly refracted or reflected by the frosted glass, generating a large number of evenly distributed divergent sub-light sources. These divergent sub-light sources act as signal light, interfering with reference light from another direction. The interference fringes are recorded on the photosensitive material to form a volume hologram. When the projector's outgoing beam illuminates the volume hologram in the direction of the original reference light, the signal light is reproduced in the volume hologram in the area illuminated by the projector's pattern. This signal light appears as a point light source emanating from the photosensitive material layer. When this light enters the human eye, the pattern projected by the projector appears on the photosensitive material layer.

[0005] However, the diffusion angle of the light beam caused by the frosted glass is very large, basically covering the full solid angle (4π) range. Figure 1In the exposure method shown, the diffuse light beam within the half-space (2π) behind the frosted glass acts as the signal light. Therefore, the reproduced signal light also has a 2π three-dimensional divergence angle. Much of the reproduced signal light does not reach the human eye, resulting in low efficiency and reducing its practical value. Summary of the Invention

[0006] This solution aims to overcome at least one defect in the prior art and provides a method for manufacturing a volume holographic optical diffusion element. The manufactured volume holographic optical diffusion element has a limited divergence angle, can improve the utilization rate of light energy, enhance display brightness and reduce equipment energy consumption, greatly increasing its practical value.

[0007] In order to solve the above technical problems, the following technical solutions are adopted:

[0008] In a first aspect, a method for fabricating a volume holographic optical diffusion element is provided. The method includes: disposing a first diffusion element having light diffusion properties on one side of a holographic photosensitive material layer, so that signal light is irradiated onto the holographic photosensitive material layer through the first diffusion element, thereby interfering with reference light irradiated onto the holographic photosensitive material layer; and further including: disposing a first lens assembly between the holographic photosensitive material layer and the first diffusion element, and projecting a real image of the first diffusion element onto the holographic photosensitive material layer using the first lens assembly.

[0009] This solution adds a first lens assembly between the first diffusing element and the holographic photosensitive material. This assembly projects the real image of the first diffusing element onto the holographic photosensitive material layer. Due to the limited entrance pupil diameter of the first lens assembly, only light within a certain angle range of the random point light source generated when the signal light illuminates the first diffusing element is able to pass through the first lens assembly. This results in a limited divergence angle for the light projected behind the real image on the holographic photosensitive material layer. Accordingly, the reproduced signal light generated during the display process also has a limited divergence angle. This not only satisfies the diffusion requirement of ensuring that all real image points can enter the human eye, but also avoids light energy waste caused by excessive diffusion. This improves light energy utilization, boosts display brightness, and reduces device energy consumption, thus possessing significant practical value.

[0010] When a volume holographic optical diffusion element is illuminated by a light beam along the direction of the reference light, it generates reproduced signal light. The direction of the reproduced signal light is controlled by changing the inclination angle of the first diffusion element and / or the deviation distance of the first diffusion element. The three-dimensional divergence angle θ of the reproduced signal light is controlled by changing the distance between the first diffusion element and the first lens assembly, the image-side focal length of the first lens assembly, and / or the entrance pupil diameter of the first lens assembly. Therefore, a high-efficiency volume holographic optical diffusion element with arbitrary propagation direction and divergence angle can be manufactured, with flexible design and no stray light interference.

[0011] The first lens assembly may include one, two or more lenses, and may further include an aperture. The first diffusion element may be frosted glass, or other elements with light diffusion properties.

[0012] In a second aspect, a device for fabricating a volume holographic optical diffusion element is provided. The device includes a signal light generation system and a reference light generation system, which are used for interferometric exposure of a holographic photosensitive material layer to form the volume holographic optical diffusion element. The signal light generation system includes a first diffusion element and a first lens assembly positioned on one side of the holographic photosensitive material layer. The first diffusion element, the first lens assembly, and the holographic photosensitive material layer are sequentially arranged along the direction of the signal light. The first diffusion element has light diffusion properties, and its actual image is located on the holographic photosensitive material layer.

[0013] This solution adds a first lens assembly between the first diffusing element and the holographic photosensitive material. This assembly projects the real image of the first diffusing element onto the holographic photosensitive material layer. Due to the limited entrance pupil diameter of the first lens assembly, only light within a certain angle range of the random point light source generated when the signal light illuminates the first diffusing element is able to pass through the first lens assembly. This results in a limited divergence angle for the light projected behind the real image on the holographic photosensitive material layer. Accordingly, the reproduced signal light generated during the display process also has a limited divergence angle. This not only satisfies the diffusion requirement of ensuring that all real image points can enter the human eye, but also avoids light energy waste caused by excessive diffusion. This improves light energy utilization, boosts display brightness, and reduces device energy consumption, thus possessing significant practical value.

[0014] When a volume holographic optical diffusion element is illuminated by a light beam along the direction of the reference light, it generates reproduced signal light. Changing the inclination angle of the first diffusion element and / or the deviation distance of the first diffusion element can adjust the direction of the reproduced signal light. Changing the distance between the first diffusion element and the first lens assembly, the image-side focal length of the first lens assembly, and / or the entrance pupil diameter of the first lens assembly can adjust the three-dimensional divergence angle θ of the reproduced signal light. Therefore, a high-efficiency volume holographic optical diffusion element with arbitrary propagation direction and divergence angle can be manufactured, with flexible design and no stray light interference.

[0015] The reference light generation system may include a second diffuser element and a second lens assembly disposed on one side of the holographic photosensitive material layer. The second diffuser element, the second lens assembly, and the holographic photosensitive material layer are sequentially arranged along the reference light direction. The second diffuser element has light-diffusing properties, and its real image is located on the holographic photosensitive material layer and overlaps with the real image of the first diffuser element. This reduces the assembly precision requirements of the projection optical machine for the resulting volume holographic optical diffuser element, thereby simplifying assembly.

[0016] The first lens assembly may include one, two or more lenses, and may further include an aperture. The first diffusion element and the second diffusion element may be frosted glass, or other elements with light diffusion properties.

[0017] In a third aspect, a volume holographic optical diffusion element is provided. The volume holographic optical diffusion element includes a holographic photosensitive material layer that generates a reproduction signal light only when illuminated by light in the direction of a reference light. The source of the reproduction signal light is located on the holographic photosensitive material layer, and its three-dimensional divergence angle θ satisfies: θ∈(0,0.5π), preferably: θ∈[0.001π,0.5π], and more preferably: θ∈[0.002π,0.3π].

[0018] In this solution, the volume holographic optical diffuser generates reproduced signal light only when illuminated by light from the reference light direction. In other words, the volume holographic optical diffuser has a diffusion effect only for projection beams within a specific range of incident angles, and has no diffusion effect on incident light from other directions. Therefore, it has high transmittance in most directions. The reproduced signal light not only has its source located on the holographic photosensitive material layer but also has a limited three-dimensional divergence angle. This not only satisfies the diffusion requirement that all real image points can enter the human eye, but also avoids the waste of light energy caused by excessive diffusion. This improves light energy utilization, increases display brightness, and reduces device energy consumption, thus possessing great practical value. This volume holographic optical diffuser can be manufactured using the method proposed in the first aspect or the device proposed in the second aspect.

[0019] The volume holographic optical diffusion element may further include a transparent substrate on which the holographic photosensitive material layer is formed. The transparent substrate may be a vehicle window, a display window, etc., and the vehicle window may be a windshield, a side glass, or a rear glass.

[0020] In a fourth aspect, a projection screen product is provided. The projection screen product includes a projection light engine and the above-mentioned volume holographic optical diffusion element. Light emitted by the projection light engine is irradiated onto the volume holographic optical diffusion element along the reference light direction.

[0021] This solution uses the aforementioned volume holographic optical diffusion element, which has high transmittance in most directions, as a display interface. This allows the human eye to see both the virtual image projected by the projection light engine on the volume holographic optical diffusion element and the real world through the volume holographic optical diffusion element, presenting the virtual image above the real world. The reproduced signal light generated by the projection light engine illuminating the volume holographic optical diffusion element has a limited three-dimensional divergence angle, which not only meets the diffusion requirement that all real image points can enter the human eye, but also avoids the waste of light energy caused by excessive diffusion, thereby improving light energy utilization, increasing display brightness, and reducing equipment energy consumption, and has great practical value. This projection screen product can specifically be a projection-type head-up display product.

[0022] Compared with existing technologies, this solution offers the following advantages: The reproduced signal light from the volume holographic optical diffuser not only has its source located on the holographic photosensitive material layer but also has a limited three-dimensional divergence angle. This not only meets the diffusion requirement of ensuring that all real image points can enter the human eye, but also avoids light energy waste caused by excessive diffusion. This improves light energy utilization, enhances display brightness, and reduces device energy consumption, thus possessing significant practical value. The method and apparatus for fabricating this volume holographic optical diffuser can be controlled to create high-efficiency volume holographic optical diffusers with arbitrary propagation directions and divergence angles, offering flexible design and eliminating stray light interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the present invention. To better illustrate the present invention, some components in the accompanying drawings may be omitted, enlarged, or reduced in size, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the production process of traditional volume holographic diffusion film.

[0025] Figure 2 yes Figure 1 Schematic diagram of the display process of traditional volume holographic diffuser film.

[0026] Figure 3 It is a schematic diagram of the display process of the volume holographic optical diffusion element.

[0027] Figure 4 yes Figure 3 Schematic diagram of the production process of volume holographic optical diffusion element.

[0028] Figure 5 It is a schematic diagram of the principle of controlling the three-dimensional divergence angle of the reproduced signal light.

[0029] Figure 6 This is a schematic diagram of the principle of controlling the direction of the reproduced signal light.

[0030] Figure 7 This is another schematic diagram of the principle of controlling the direction of the reproduced signal light.

[0031] Figure 8 The diagram is a possible structure and optical path diagram of a signal light generation system.

[0032] Figures 1-2 Description of reference numerals: frosted glass 1, photosensitive material 2, substrate 3, volume hologram Figure 4 , lens group 5 of the projection light machine, signal light O, reference light R, projection light P, reproduced signal light O', reproduced signal light O" entering the human eye, pattern I projected by the projection light machine, real image I' of the pattern projected by the projection light machine, human eye E.

[0033] Figures 3 to 8 Explanation of the reference numerals: holographic photosensitive material layer 110, volume hologram 111, transparent substrate 120, signal light generating system 210, first diffusion element 211, first lens assembly 222, lens 2221, aperture 2222, reference light generating system 220, third lens assembly 310, signal light O, reference light R, projection light P, reproduced signal light O', pattern I projected by the projection light machine, real image I' of the pattern projected by the projection light machine, human eye E. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present solution, the present solution is further described in detail below with reference to specific embodiments.

[0035] Figure 3 An embodiment of a volume holographic optical diffusion element is shown. The volume holographic optical diffusion element comprises at least a holographic photosensitive material layer 110 formed of a holographic photosensitive material. The holographic photosensitive material layer 110 generates a volume hologram 111 under interference exposure of signal light and reference light. This allows the volume holographic optical diffusion element to have a diffusion effect only for a projection beam within a specific incident angle range (along the direction of the reference light) and has no diffusion effect for incident light in other directions. Therefore, the volume holographic optical diffusion element has a high transmittance in most directions. Figure 3 As shown, when the volume hologram 111 is illuminated by a beam carrying information along the reference light direction, it generates reproduction signal light carrying the aforementioned information, thereby presenting a real image of the aforementioned information. The source of these reproduction signal lights is located on the volume hologram 111, just like a point light source emanating from the holographic photosensitive material layer 110. Furthermore, they have a limited three-dimensional divergence angle, namely, their three-dimensional divergence angle θ satisfies: θ∈(0,0.5π). This allows the human eye to see all real image points, and the amount of reproduction signal light that does not enter the human eye is less than that of traditional volume holographic diffusion films. This improves light energy utilization, increases display brightness, and reduces device energy consumption, thus possessing great practical value.

[0036] The smaller the stereo divergence angle θ is, the less reproduced signal light that does not enter the human eye, and the higher the light energy utilization rate. However, if the stereo divergence angle θ is too small, it is not conducive to ensuring that all real image points can be seen by the human eye. Therefore, the stereo divergence angle θ preferably satisfies: θ∈[0.001π,0.5π], and more preferably satisfies: θ∈[0.002π,0.3π]. The specific design can be based on the application scenario.

[0037] The volume holographic optical diffuser element may also include a transparent substrate 120, with the holographic photosensitive material layer 110 formed on its surface. In specific applications, the transparent substrate 120 may be a vehicle window, a display window, or the like, including but not limited to a windshield, side windows, and rear glass. In a projection-type head-up display, the windshield can directly serve as the transparent substrate 120, providing the driver with real-time driving information. Alternatively, the transparent substrate 120 may be a transparent film with adhesive backing. The formed volume holographic optical diffuser element can then be attached to the display surface of a projection screen product, such as a vehicle window or display window.

[0038] The volume holographic optical diffusion element can be manufactured using the first diffusion element 211 having light diffusion properties as a template. Figure 4 A possible production process is shown in Figure 1. Figure 4 As shown, an apparatus for fabricating a volume holographic optical diffusion element includes a signal light generating system and a reference light generating system, which are used to perform interference exposure on a holographic photosensitive material layer 110 to fabricate the volume holographic optical diffusion element. The signal light generating system includes a first diffusion element 211 and a first lens assembly 222. The first diffusion element 211, the first lens assembly 222, and the holographic photosensitive material layer 110 are sequentially arranged along the direction of the signal light. The first diffusion element 211 has light diffusion properties, and its real image is located on the holographic photosensitive material layer 110. The fabrication method involves irradiating the first diffusion element 211 with signal light, and projecting the real image of the first diffusion element 211 onto the holographic photosensitive material layer 110 using the first lens assembly 222. The real image interferes with the reference light irradiated on the holographic photosensitive material layer 110, thereby replicating only a portion of the light diffusion properties of the first diffusion element 211 onto the holographic photosensitive material layer 110.

[0039] When signal light is illuminated by the first diffusion element 211, it diffuses the signal light, generating a large number of evenly distributed random point light sources behind it. The light emitted by these point light sources has a large divergence angle. Due to the limited entrance pupil diameter of the first lens assembly 222, only light within a certain angle range from the random point light sources can pass through the first lens assembly 222. After passing through the first lens assembly 222, these light rays form conjugate real images of the random point light sources in the holographic photosensitive material layer 110. Due to the pupil restriction effect of the first lens assembly 222, the light rays behind these conjugate real images have a limited divergence angle. At this time, if reference light is introduced to interfere with the signal light near the conjugate real images, the holographic photosensitive material layer 110 can be photosensitive and record the conjugate real images of the point light sources, forming a volume hologram 111. When projection display is required, light from the projector is projected onto the volume hologram 111, and the illuminated area will reproduce the signal light with a limited divergence angle. Through design, the divergence angle of the signal light can be constrained to only illuminate the area near the human eye, thereby ensuring the effective use of light energy.

[0040] The direction and divergence angle of the reproduced signal light often need to be adjusted according to the specific application scenario. For example, in a projection head-up display device, the plane where the holographic photosensitive material layer 110 is located has a certain inclination angle, such as Figure 7 As shown, the projected real image must be visible to the human eye within a certain eyebox. To achieve this goal, the signal light generation system 210 and the reference light generation system 220 must be specifically designed. The signal light generation system 210 requires that the conjugate real image plane of the first diffusing element 211 after passing through the system coincide with the plane of the holographic photosensitive material layer 110, and that the exit pupil size of the system be comparable to the eyebox size b. The reference light generation system 220 requires that the reference light, after passing through the system, illuminates the area in the plane of the holographic photosensitive material layer 110, covering the area illuminated by the signal light.

[0041] The direction of the reproduced signal light, the size of the three-dimensional divergence angle and other properties can be controlled by changing the distance between the first diffusion element 211 and the first lens assembly 222, the inclination angle of the first diffusion element 211, the deviation distance of the first diffusion element 211, the focal length of the first lens assembly 222, the entrance pupil diameter (entrance pupil radius) of the first lens assembly 222 and other parameters. Therefore, a high-efficiency volume holographic optical diffusion element with arbitrary propagation direction and divergence angle can be produced, with flexible design and no stray light interference. Figure 5 As shown, under the paraxial approximation, the three-dimensional divergence angle θ at each location of the volume hologram 111 is related to the image-side aperture angle u2, that is, θ≈2*u2. According to the imaging formula of the ideal optical system, it can be obtained: Where f is the image-side focal length of the first lens assembly 222, s is the distance between the first diffuser 211 and the object-side principal surface of the first lens assembly 222 (object distance), t is the distance between the image of the first diffuser 211 and the image-side principal surface (image distance), and h is the entrance pupil radius of the first lens assembly 222. It can be seen that the stereo divergence angle of the reproduced signal light is mainly determined by the entrance pupil radius of the first lens assembly 222, the image-side focal length of the first lens assembly 222, and the distance between the first lens assembly 222 and the first diffuser 211.

[0042] like Figure 6 As shown, taking the central light at the center of the volume hologram 111 as an example, its propagation direction angle is α, and according to the imaging law of the lens 2221 system, it can be obtained: Where d is the deviation distance of the center of the portion of the first diffusion element 211 that is illuminated by the initial signal light relative to the main optical axis of the first lens assembly 222, and s is the distance between the first diffusion element 211 and the object side principal surface of the first lens assembly 222 (object distance). It can be seen that by controlling the deviation distance of the center of the portion of the first diffusion element 211 that is illuminated by the initial signal light relative to the main optical axis of the first lens assembly 222, the emission angle of the central light emitted from the volume holographic optical diffusion element, that is, the direction of the reproduced signal light, can be controlled. The greater the deviation distance d, the greater the direction angle of the light beam emitted by the volume holographic optical diffusion element. In addition, the direction of the reproduced signal light can also be controlled by changing the inclination angle of the first diffusion element 211, such as Figure 7 shown.

[0043] The signal light generating system may further include a first beam expander to expand the signal light. The first beam expander, the first diffusion element 211 and the first lens assembly 222 are all arranged on one side of the holographic photosensitive material layer 110 and are arranged sequentially along the direction of the signal light. The first lens assembly 222 may include one or more lenses 2221. In addition to the lens 2221, the first lens assembly 222 may also include an aperture 2222, such as Figure 8 The first diffusion element 211 can be frosted glass or other elements with light diffusion properties.

[0044] The reference light generation system includes a second beam expander, which expands the reference light to ensure that the reference light, after passing through the system, overlaps the area illuminated by the signal light in the plane of the holographic photosensitive material layer 110. Alternatively, the reference light generation system can have the same optical system as the projection light engine, except that it lacks an image generator, or the image generator in the projection light engine is replaced with a second diffusing element. In the latter case, the reference light generation system includes a second diffusing element and a second lens assembly positioned on one side of the holographic photosensitive material layer 110. The second diffusing element, the second lens assembly, and the holographic photosensitive material layer 110 are sequentially arranged along the direction of the reference light. When a laser light source illuminates the second diffusing element, the real image formed by the reference light generation system coincides with the plane of the holographic photosensitive material layer 110 and the area illuminated by the signal light. The second diffusing element can be made of frosted glass or other light-diffusing elements, which reduces the assembly precision requirements of the projection light engine, thereby simplifying assembly.

[0045] The signal light is generated by a signal light source, and the reference light is generated by a reference light source. The signal light source can exist independently of the signal light generation system or be integrated into it. Similarly, the reference light source can exist independently of the reference light generation system or be integrated into it. Both the signal light source and the reference light source can be laser light sources, or they can be the same laser light source, which is then separated into signal light and reference light by a beam splitter.

[0046] The above-mentioned volume holographic optical diffusion element can be used to assemble a projection display device (projection screen product), especially a projection head-up display product. For example, Figure 3 A possible projection screen product is illustrated, comprising a projection engine and the aforementioned volume holographic optical diffuser. The projection engine, similar to a projector, comprises an image generator and a third lens assembly 310 positioned on one side of the volume holographic optical diffuser. The image generator, third lens assembly 310, and volume holographic optical diffuser are sequentially arranged along the reference light direction. Light carrying a virtual image is projected onto the volume holographic optical diffuser along the reference light direction, forming a real image of the virtual image on the volume holographic optical diffuser. Light from the projection engine illuminates the volume holographic optical diffuser, generating a reproduction signal light. This reproduction signal light enters the human eye, allowing the aforementioned virtual image to be perceived. If the volume holographic optical diffuser is positioned on a windshield, or its transparent substrate 120 is a windshield, then this projection screen product is effectively a projection-type head-up display product. The virtual image projected by the projection engine can be driving information such as speed and navigation. If the volume holographic optical diffusion element is disposed on a display window, or its transparent substrate 120 is a display window, the virtual image projected by the projection light machine may be introduction information of the items displayed in the display window.

[0047] Obviously, the above embodiments of this solution are merely examples for the purpose of clarifying this solution and are not intended to limit the implementation of this solution. Those skilled in the art will be able to make other variations or modifications based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this solution shall be included within the scope of protection of the claims of this solution.

Claims

1. A method for manufacturing a volume holographic optical diffusion element, the method comprising: A first diffusion element having light diffusion characteristics is provided on one side of the holographic photosensitive material layer, so that the signal light is irradiated onto the holographic photosensitive material layer through the first diffusion element and interferes with the reference light irradiated onto the holographic photosensitive material layer; characterized in that: The method also includes: arranging a first lens assembly between the holographic photosensitive material layer and the first diffusion element, and using the first lens assembly to project a real image of the first diffusion element onto the holographic photosensitive material layer; when the volume holographic optical diffusion element is irradiated by a light beam along the direction of the reference light, a reproduction signal light is generated, and a source point of the reproduction signal light is located on the holographic photosensitive material layer.

2. The method according to claim 1, characterized in that The direction of the reproduced signal light is controlled by changing the inclination angle of the first diffusion element and / or the deviation distance of the first diffusion element.

3. The method according to claim 1, characterized in that The three-dimensional divergence angle of the reproduced signal light θ The control is achieved by changing the distance between the first diffusion element and the first lens assembly, the image-side focal length of the first lens assembly and / or the entrance pupil diameter of the first lens assembly.

4. The method according to claim 1, wherein The first lens assembly comprises one, two or more lenses; and / or The first lens assembly comprises a lens and a stop; and / or The first diffusion element is frosted glass.

5. An apparatus for manufacturing a volume holographic optical diffusion element, comprising a signal light generating system and a reference light generating system, for interferometrically exposing a holographic photosensitive material layer to manufacture the volume holographic optical diffusion element; characterized in that: The signal light generating system includes a first diffusion element and a first lens assembly arranged on one side of a holographic photosensitive material layer, wherein the first diffusion element, the first lens assembly and the holographic photosensitive material layer are arranged sequentially along the direction of the signal light; the first diffusion element has a light diffusion characteristic, and its actual image is located on the holographic photosensitive material layer; when the volume holographic optical diffusion element is irradiated by a light beam along the direction of the reference light, it generates a reproduced signal light, and the source point of the reproduced signal light is located on the holographic photosensitive material layer.

6. The device according to claim 5, characterized in that The reference light generating system includes a second diffusion element and a second lens assembly arranged on one side of the holographic photosensitive material layer. The second diffusion element, the second lens assembly and the holographic photosensitive material layer are arranged in sequence along the direction of the reference light; the second diffusion element has a light diffusion characteristic, and its real image is located on the holographic photosensitive material layer and coincides with the real image of the first diffusion element.

7. The device according to claim 5, characterized in that The first lens assembly comprises one, two or more lenses; and / or The first lens assembly comprises a lens and a stop; and / or The first diffusion element is frosted glass; and / or The second diffusion element is frosted glass.

8. A volume holographic optical diffusion element, comprising a holographic photosensitive material layer, wherein the holographic photosensitive material layer generates a reproduction signal light when and only when irradiated by light in the direction of a reference light, characterized in that: The volume holographic optical diffusion element is made by the method according to any one of claims 1 to 4 or the device according to any one of claims 5 to 7. The source point of the reproduced signal light is located on the holographic photosensitive material layer, and its three-dimensional divergence angle is θ satisfy: θ ∈(0, 0.5π).

9. The volume holographic optical diffusion element according to claim 8, wherein: The solid divergence angle θ satisfy: θ ∈[0.001π, 0.5π]; and / or The volume holographic optical diffusion element further includes a transparent substrate, and the holographic photosensitive material layer is formed on the transparent substrate.

10. The volume holographic optical diffusion element according to claim 9, wherein: The solid divergence angle θ satisfy: θ ∈[0.002π, 0.3π]; and / or The transparent substrate is a vehicle window or a display window, and the vehicle window is a windshield, a side glass or a rear glass.

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