Manufacturing apparatus and manufacturing method for reflective volume holographic grating

Abstract

A manufacturing apparatus for a reflective volume holographic grating (209), the manufacturing apparatus comprising a light source (200) and an exposure module. The exposure module comprises a mask (112), which has at least one optical diffraction module (113), a recording medium (110), coupling prisms (106, 107) and an exposure modulation unit, wherein the optical diffraction module (113) receives incident recording light beams (100, 213) output by the light source (200), and diffracts and splits the incident recording light beams (100, 213) to obtain a reflected diffraction light beam; the coupling prisms (106, 107) adjust the incident recording light beams (100, 213) to enter the recording medium (110) at a preset angle, and after the incident recording light beams (100, 213) and the reflected diffraction light beam are input into the recording medium (110), a volume holographic grating is formed; and the exposure modulation unit controls an exposure parameter on the recording medium (110) to obtain an exposed reflective volume holographic grating (209). By adjusting an incident angle of an incident recording light beam and using an exposure modulation unit to control an exposure parameter, a reflective volume holographic grating (209) for multi-degree-of-freedom modulation is generated, and the implementation mode is simple and involves high efficiency. Further disclosed is a manufacturing method for a reflective volume holographic grating (209).

Description

A manufacturing device and method for a reflective volume holographic grating

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on October 27, 2023, with application number 202311404563.2 and invention name “A manufacturing device and manufacturing method for a reflective volume holographic grating”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the technical field of holographic grating manufacturing, and in particular to a manufacturing device and method for a reflective volume holographic grating. Background Art

[0004] Volume holographic grating waveguides are used in augmented reality display systems or mixed reality display systems because they can provide a larger field of view, better optical display effects and a lighter and thinner volume. However, the preparation process of volume holographic gratings in the existing technology requires dual-beam exposure equipment, and the interference fringes have strict requirements on environmental disturbances, temperature, humidity and other aspects. Therefore, it is difficult to achieve high-quality, large-scale batch production of volume holographic gratings.

[0005] Therefore, the existing technology needs to be improved.

[0006] Application Contents

[0007] In view of the above-mentioned deficiencies in the prior art, the purpose of this application is to provide a manufacturing device and method for a reflective volume holographic grating, so as to overcome the defect that the volume holographic grating manufacturing process in the prior art is difficult to achieve high-quality large-scale batch production of volume holographic gratings.

[0008] The technical solutions adopted by this application to solve the technical problems are as follows:

[0009] In a first aspect, an embodiment of the present application provides a device for manufacturing a reflective volume holographic grating, comprising: a light source and an exposure module located in the light path of the light source; the exposure module comprising: a mask having at least one optical diffraction module, a recording medium, a coupling prism, and an exposure modulation unit;

[0010] The light source is used to provide an incident recording light beam;

[0011] The optical diffraction module on the mask is used to receive the incident recording light beam and perform diffraction and splitting on the incident recording light beam to obtain a reflected diffracted light beam;

[0012] The coupling prism is used to adjust the angle at which the incident recording beam enters the mask, so that the incident recording beam enters the recording medium at a preset angle and eliminate background interference noise caused by non-ideal refraction and reflection of the incident recording beam on the interface, thereby further improving the signal-to-noise ratio of the target interference fringes;

[0013] The recording medium is used to generate interference fringes according to the input incident recording light beam and the reflected diffracted light beam, and to form a refractive index difference between the interference intensity enhanced area and the interference intensity weakened area to form a volume holographic grating;

[0014] The exposure modulation unit is used to control the exposure parameters on the recording medium to obtain the reflective volume holographic grating after exposure.

[0015] In a second aspect, an embodiment of the present application further provides a method for manufacturing a reflective volume holographic grating, comprising:

[0016] preparing a recording medium;

[0017] preparing an optical diffraction module;

[0018] A manufacturing device for a reflective volume holographic grating based on a recording medium and an optical diffraction module;

[0019] The reflective volume holographic grating is obtained by using the manufacturing device of the reflective volume holographic grating. Beneficial effects:

[0020] This embodiment discloses a device and method for manufacturing a reflective volume holographic grating. The device includes a light source and an exposure module. The exposure module includes a mask having at least one optical diffraction module, a recording medium, a coupling prism, and an exposure modulation unit. An incident recording beam provided by the light source is incident on the optical diffraction module on the mask. The optical diffraction module receives the incident recording beam and diffracts and splits it to produce a reflected diffracted beam. The coupling prism adjusts the angle at which the incident recording beam enters the mask so that the incident recording beam enters the recording medium at a preset angle. The recording medium generates interference fringes based on the input incident recording beam and the reflected diffracted beam, and changes its refractive index to form a volume holographic grating. The exposure modulation unit controls exposure parameters on the recording medium to produce a reflective volume holographic grating after exposure. In this embodiment, by adjusting the incident angle of the incident recording beam and controlling the exposure parameters using the exposure modulation unit, a reflective volume holographic grating with multi-degree-of-freedom modulation is generated, resulting in a simple and efficient implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic structural diagram of an exposure module in an embodiment of the present application;

[0022] FIG2 is a schematic structural diagram of a device for manufacturing a reflective volume holographic grating according to an embodiment of the present application;

[0023] FIG3 is a schematic diagram showing the principle of grating synchronous exposure with different grating parameters in an embodiment of the present application;

[0024] FIG4 is a flowchart of the steps of a method for manufacturing a reflective volume holographic grating in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0026] The following describes the embodiments of the present application through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present application from the disclosure herein. The present application may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present application.

[0027] For example, when describing the embodiments of this application, cross-sectional views of the device structure may be partially enlarged to a different scale for ease of explanation. Furthermore, these schematic views are merely illustrative and should not limit the scope of protection of this application. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0028] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present application in a schematic manner. Therefore, the illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0029] The planar optical waveguide integrated system is an indispensable key optical module in fields such as augmented reality (AR) and optical computing. In it, the light beam carrying object information is coupled into the planar waveguide through diffraction devices such as gratings. Then, the diffraction angle of the diffracted light beam meets the requirements of total internal reflection and is transmitted in the planar waveguide. Finally, it is output from the waveguide through another grating diffraction device. At present, although surface relief gratings based on nanoimprinting have been initially mass-produced, augmented reality (AR) systems based on surface relief gratings still face performance-limiting problems such as rainbow effect and small field of view (FOV).

[0030] Volume holographic gratings (VHGs) are considered an essential technology for next-generation augmented reality (AR) systems due to their ability to provide a wider field of view, better optical display quality, and a thinner and lighter footprint. However, the fabrication process often requires dual-beam exposure equipment, and the interference fringes are highly sensitive to environmental disturbances, temperature, humidity, and other factors. Therefore, a series of techniques, such as vibration isolation, fringe locking, and grating period measurement, must be employed to ensure the stability of the interference fringes. This makes high-quality, large-scale mass production of VHGs difficult.

[0031] Based on the diffraction effect of gratings, a technique for producing transmissive volume holographic gratings has been developed in the prior art. This involves illuminating the grating with an incident light beam, producing positive and negative first-order diffraction orders. The incident and diffracted beams enter the recording medium from the same side and converge at a specified location to produce exposure interference fringes. However, this method can only produce transmissive volume holographic gratings. Furthermore, because the incident light beam enters the air and passes through media such as the mask, transparent substrate, and recording medium, it generates multiple interfacial refractions and reflected light beams. These light beams further converge with the incident light beam, forming multiple sets of parasitic gratings or optical artifacts in the recording medium. This can further lead to problems such as reduced diffraction efficiency and increased haze in the volume holographic grating.

[0032] Furthermore, according to Bragg's theorem, for a constant refractive index contrast, the diffraction efficiency of a transmissive volume holographic grating varies sinusoidally with increasing grating thickness, reaching a maximum diffraction efficiency. In contrast, the diffraction efficiency of a reflective volume holographic grating varies logarithmically with increasing grating thickness, gradually approaching 100%. Typically, achieving higher diffraction efficiency requires the development of materials with high refractive index contrast, such as dispersible polymer liquid crystals. However, developing new materials is time-consuming and may result in changes in other properties, such as haze and thermal expansion.

[0033] Compared to transmissive volume holographic gratings, reflective volume holographic gratings are expected to achieve near-100% diffraction efficiency by increasing the grating thickness while maintaining a lower refractive index contrast, ultimately resulting in enhanced display effects with better performance. However, conventional dual-beam exposure faces numerous challenges, making it difficult to mass-produce volume holographic gratings. Furthermore, the exposure method based on a multilayer reflective film-coated substrate and Laue mirrors to prepare reflective volume holographic gratings struggles to meet the requirements of flexible, wide-angle, multi-region, and modulatable exposure. Therefore, existing technologies have only achieved transmissive volume holographic gratings through grating diffraction beam splitting. However, their diffraction efficiency is still limited by the refractive index contrast of the material, which in turn limits the manufacturing efficiency of volume holographic gratings.

[0034] However, the existing preparation methods of reflective volume holographic gratings, whether through reflective films or Laue mirrors, cannot achieve the preparation requirements of flexible, large-angle, multi-region and other multi-degree-of-freedom modulation.

[0035] Therefore, in order to overcome the above-mentioned problems in the prior art, the embodiment of the present application adopts an optical diffraction module to realize reflective diffraction beam splitting. The reflective diffraction beam splitting is combined with the original light beam to realize the preparation of a reflective volume holographic grating required for multi-degree-of-freedom modulation, which can make full use of all photosensitive medium materials and theoretically achieve a diffraction efficiency close to 100% by increasing the thickness of the photosensitive medium material.

[0036] Specifically, an embodiment of the present application provides a manufacturing device and method for a reflective volume holographic grating that can achieve multi-degree-of-freedom modulation. The manufacturing device includes an exposure module, which includes a mask having at least one optical diffraction module, a recording medium, a coupling prism and an exposure modulation unit. The coupling prism and the exposure modulation unit are used to adjust the light angles of the incident recording light beam and the reflected diffraction light beam incident on the recording medium, or to change the grating refractive index distribution, period, inclination and other parameters by adjusting the exposure parameters, so as to achieve volume holographic grating manufacturing through one or more optical diffraction modules. The method is simple, efficient, functional, and applicable to various photosensitive medium materials, and is expected to meet the stringent requirements of the next generation augmented reality (AR) system for optical display modules.

[0037] A method provided by this embodiment is described in detail below with reference to the accompanying drawings.

[0038] This embodiment provides a device for manufacturing a reflective volume holographic grating, comprising: a light source and an exposure module located on the light path of the light source; as shown in Figure 1, the exposure module comprises: a mask 112 having at least one optical diffraction module 113, a recording medium 110, a coupling prism (the coupling prism comprises: a first coupling prism 106 and a second coupling prism 107) and an exposure modulation unit; the mask 112, the recording medium 110 and the exposure modulation unit are arranged between the first coupling prism 106 and the second coupling prism 107.

[0039] The light source is used to provide an incident recording light beam.

[0040] The optical diffraction module 113 on the mask plate 112 is used to receive the incident recording beam 100 and diffract and split the incident recording beam 100 to obtain a reflected diffraction beam, wherein the reflected diffraction beam includes: a zero-order diffraction beam 102 and a positive first-order or negative first-order diffraction beam 103 reflected by the optical diffraction module.

[0041] The first coupling prism 106 and the second coupling prism 107 are used to adjust the angle at which the incident recording beam 100 is incident on the mask 112, so that the incident recording beam 100 is incident on the recording medium 110 at a preset angle, and eliminate background interference noise on the interface caused by non-ideal refraction and reflection of the incident recording beam, so as to further improve the signal-to-noise ratio of the target interference fringes.

[0042] The recording medium 110 is used to generate interference fringes according to the input incident recording light beam 100 and the positive first-order or negative first-order diffracted light beam 103, and change the refractive index to form a volume holographic grating.

[0043] The exposure modulation unit is used to control the exposure parameters on the recording medium to obtain the reflective volume holographic grating after exposure.

[0044] The manufacturing apparatus of the reflective volume holographic grating provided in this embodiment first uses a light source to provide an incident recording beam. During specific implementation, in order to obtain more stable interference fringes, a laser is used to provide the incident recording beam.

[0045] Furthermore, the exposure modulation unit includes: a gap block 108 and a transparent spacer 111 ; the recording medium 110 is embedded in the gap block 108 , and the transparent spacer 111 is disposed between the gap block 108 and the mask 112 .

[0046] As shown in FIG1 , an incident recording beam 100 emitted from a light source passes through a prism located above gap block 108 and then enters gap block 108 or a recording medium 110 located within gap block 108. The beams transmitted through gap block 108 and recording medium 110 are then incident on transparent spacer 111 and reticle 112, respectively, before being input into second coupling prism 107 located below reticle 112. After entering optical diffraction module 113 on reticle 112, incident recording beam 100 is diffracted and split by optical diffraction module 113 to produce reflected diffracted beams. The reflected diffracted beams include a zero-order diffracted beam 102 and a positive-first-order diffracted beam or a negative-first-order diffracted beam 103. Furthermore, the positive first-order or negative first-order diffracted light beam 103 transmitted from the optical diffraction module 113 and the zeroth-order diffracted light beam 105 transmitted from the optical diffraction module 113 are incident on the first coupling prism 106 and the second coupling prism 107, respectively. The exposure module further includes an absorption medium layer 114 disposed on the surface of the second coupling prism 107; the absorption medium layer 114 is configured to absorb excess incident recording light beam and transmitted light beam to avoid generating excess parasitic gratings or optical artifacts.

[0047] Furthermore, the incident recording beam 100 and the positive-first-order or negative-first-order diffracted beam 103 are transmitted to the recording medium 110, generating stable interference fringes and changing the refractive index of the recording medium 110 to obtain a holographic grating. A first coupling prism 106 directs the incident recording beam onto a mask 112 at a set angle of incidence. Spacers 108 and transparent spacers 111 control the exposure parameters on the recording medium 110 to adjust the exposure parameters, meeting the manufacturing requirements of multi-degree-of-freedom modulated reflective volume holographic gratings. This allows for the modification of parameters such as the grating's refractive index distribution, period, and exposure position.

[0048] Furthermore, the design parameters of the optical diffraction module 113 in the mask 112 can be changed to produce volume holographic gratings with different parameters. For example, a variable period volume holographic grating can be produced by designing the periodic variation of the diffraction parameters in the optical diffraction module 113.

[0049] In order to realize multi-beam multi-area exposure, the manufacturing device further includes: at least one rotatable semi-transparent and semi-reflective mirror arranged on the optical path of the incident recording beam.

[0050] The rotatable semi-transparent mirror is used to adjust the incident angle of the incident recording light beam transmitted to the recording medium. Each rotatable semi-transparent mirror is respectively arranged to correspond to a recording medium on a different area of ​​the reticle, so that different areas of the recording medium have different exposure parameters. The exposure parameters include, but are not limited to, the wavelength, phase, polarization, amplitude, and incident angle of the incident light beam.

[0051] Furthermore, as shown in FIG1 , the gap spacer 108 is filled with a refractive index matching liquid 109 ; the refractive index matching liquid 109 is used to fill the air gap between the coupling prism (the coupling prism includes: a first coupling prism 106 and a second coupling prism 107 ) and the recording medium 110 .

[0052] In a specific embodiment, in order to achieve a better exposure effect, the recording medium is one or more photosensitive materials such as photopolymer, photosensitive glass, photorefractive crystal, dispersible polymer liquid crystal, dichromate gelatin or silver halide gelatin.

[0053] In one embodiment, the surface shape of the optical diffraction module is a plane or a curved surface, and the optical diffraction module is a micro-nano optical structure or an optical micro-nano adjustable device. Specifically, the optical diffraction module is one or more micro-nano optical structures such as an amplitude grating, a phase grating, a diffraction optical element, a volume holographic grating, and a metasurface grating. Among them, the surface shape of the optical diffraction module can be set to be spherical. And the optical diffraction module used in this embodiment can be used to manufacture plane gratings, and can also be used to manufacture curved gratings, which can meet the needs of various optical elements with different functions, such as volume holographic lenses for focusing, volume holographic gratings for display, and volume holographic encoding and decoding for data storage.

[0054] Furthermore, as shown in FIG2 , the manufacturing apparatus further includes a collimating and expanding system arranged in sequence on the outgoing optical path of the light source 200 to collimate and expand the incident recording light beam. Specifically, the collimating and expanding system includes a focusing lens 201 , a pinhole stop 202 , and a collimating lens 203 .

[0055] The focusing lens 201 is used to focus the incident recording light beam emitted by the light source 200;

[0056] The pinhole diaphragm 202 is used to filter the incident recording light beam transmitted from the focusing lens 201 and adjust the beam diameter;

[0057] The collimating lens 203 is used to collimate the incident recording light beam emitted from the small aperture 202 .

[0058] The incident recording beam emitted by the light source is collimated and expanded by the collimating beam system, resulting in a collimated and expanded incident recording beam 213. After being modulated by the acousto-optic modulator 204, it is transmitted to the rotatable reflector 205. After being reflected by the rotatable reflector 205, it is reflected back to the exposure module. The incident recording beam 213 and the positive-first-order or negative-first-order diffracted beam 214 diffracted by the optical diffraction module in the reticle produce interference fringes on the recording medium 208 in the exposure module, and the refractive index of the recording medium 208 changes. The exposure module contains multiple recording media 208, including an unexposed recording medium 207 and an exposed recording medium 208. After exposure of the recording media is complete, a reflective volume holographic grating 209 is obtained. After exposure is complete, the prepared waveguide lens with the reflective volume holographic grating is packaged using a grating packaging device 210. In addition, when manufacturing holographic gratings, industrial control equipment 211 is used to control the operation of the roll-to-roll automatic loading equipment 212 and to control the parameters of the incident recording light beam 213 in the acousto-optic modulator 204 to adjust the parameters, so that the exposure time, the loading speed of the roll-to-roll automatic loading equipment, the various parameters of the incident light beam, etc. are matched with each other and automated production is achieved.

[0059] In order to achieve multi-area exposure and obtain the effect of multi-degree-of-freedom modulation, multiple optical diffraction modules are provided on the mask, and multiple recording areas for recording volume holographic gratings are provided at different positions. Each of the recording areas may be the same or different areas of the same medium, or the same or different areas of different media. The parameters of each optical diffraction module may be the same or different. After synchronous exposure of each of the recording areas under the exposure parameters, multi-block volume holographic gratings with different grating parameters are obtained. The multi-block volume holographic gratings may be coupling-in gratings, and / or coupling-out gratings, and / or turning gratings.

[0060] Since there can be multiple recording areas in the same medium, each recording area can be a different area in the same medium. Since the exposure parameters set are different, each recording area can also be the same area in the same medium. Furthermore, each recording area can also be the same area or different areas of different media. As long as the recording area can meet the conditions of generating interference fringes according to the input incident recording light beam and the reflected diffraction light beam under different exposure parameters, and forming a refractive index difference in the interference intensity enhanced area and the interference intensity weakened area to form a volume holographic grating, it will be sufficient.

[0061] As shown in Figure 3, taking the example of a mask having three optical diffraction modules with different parameters, the mask 317 is provided with a first optical diffraction module 313, a second optical diffraction module 314, and a third optical diffraction module 315 with different parameters. The recording media disposed at different locations include a first recording medium, a second recording medium, and a third recording medium. After synchronous exposure, the first, second, and third recording media respectively produce an in-coupling grating 310, a turning grating 311, and an out-coupling grating 312 with different grating parameters.

[0062] As shown in Figure 3, a transparent spacer 316 is provided on the mask plate 317, and a plurality of recording media are arranged in sequence between the transparent spacers 316. A plurality of rotatable semi-transparent and semi-reflective mirrors are arranged in sequence above the transparent spacer 316, namely a first rotatable semi-transparent and semi-reflective mirror 307, a second rotatable semi-transparent and semi-reflective mirror 308 and a third rotatable semi-transparent and semi-reflective mirror 309. Specifically, the transmittance of the first rotatable semi-transparent and semi-reflective mirror 307, the second rotatable semi-transparent and semi-reflective mirror 308 and the third rotatable semi-transparent and semi-reflective mirror 309 can be adjusted as needed, so that the angles of the light beams incident on each recording medium are different, and the light beam transmitted by the previous rotatable semi-transparent and semi-reflective mirror can continue to be transmitted and reflected by the next rotatable semi-transparent and semi-reflective mirror to different angles, thereby realizing the modulation of the incident recording light beam incident on the recording medium.

[0063] Specifically, an incident recording beam 301 emitted from a light source is reflected by a rotatable semi-transparent mirror and then transmitted to each recording medium of the reticle. The rotatable semi-transparent mirror can change the angle of the incident recording beam 301. The reticle 112 is provided with multiple optical diffraction modules. Each optical diffraction module diffracts the incident recording beam 301 to produce a first diffracted beam 304, a second diffracted beam 305, and a third diffracted beam 306 of the positive or negative first order. The incident recording beam 301 and the reflected diffracted beams converge at the recording medium to form stable interference fringes, thereby forming a volume holographic grating in each recording medium. Furthermore, based on different grating parameters, each recording medium forms an in-coupling grating 310, a turning grating 311, and an out-coupling grating 312. Transparent spacers 316 can be used to change the positional relationship between the in-coupling grating 310, the turning grating 311, and the out-coupling grating 312. In order to achieve better exposure effect, an absorption medium layer is provided under the mask 317 to absorb the excess transmitted light beam to avoid generating excess parasitic gratings or optical artifacts.

[0064] Since the exposure module in the manufacturing device provided in this embodiment can use multiple semi-transparent and semi-reflective mirrors to achieve multi-beam and multi-region exposure, the manufacturing device provided in this embodiment can realize multi-degree-of-freedom modulated reflective volume holographic grating through flexible settings, thereby meeting the manufacturing needs of large-angle and multi-region reflective volume holographic gratings.

[0065] The present application proposes a device, method and equipment for manufacturing a reflective volume holographic grating that can achieve multi-degree-of-freedom modulation. By adopting an optical diffraction module to realize diffraction beam splitting to prepare a volume holographic grating, it solves the problems of low efficiency, susceptibility to environmental influences, and difficulty in achieving multi-degree-of-freedom (large angle, multi-region) modulation in the existing technology for preparing volume holographic gratings.

[0066] In addition to providing the above-mentioned device for manufacturing a reflective volume holographic grating, the present application also discloses a method for manufacturing a reflective volume holographic grating, the method comprising the following steps:

[0067] Step S1, preparing a recording medium; preparing a photosensitive medium material, wherein the photosensitive medium material includes: photopolymer, photosensitive glass, photorefractive crystal, dispersible polymer liquid crystal, dichromate gelatin or silver halide gelatin.

[0068] Step S2: Prepare an optical diffraction module. The optical diffraction module includes, but is not limited to, diffraction optical elements such as amplitude gratings, phase gratings, volume holographic gratings, and metasurfaces. The shape of the optical diffraction module can be spherical, free-form, or aspherical. The size, shape, and number of the optical diffraction modules are designed according to preset design parameters.

[0069] Step S3: Use the recording medium and the optical diffraction module to build a manufacturing device for a reflective volume holographic grating; first, build the exposure light path in the exposure module according to the structure of each component in the exposure module, then build each component in the manufacturing device in sequence, and finally obtain the completed manufacturing device for the reflective volume holographic grating.

[0070] Step S4: using the reflective volume holographic grating manufacturing device to obtain an exposed reflective volume holographic grating.

[0071] According to a preset incident angle, the angle at which the incident recording light beam is incident on the recording medium is adjusted, the exposure modulation unit is adjusted according to preset exposure parameters, the position areas of each optical diffraction module on the mask are arranged, and the position of the rotatable semi-transparent and semi-reflective mirror is adjusted. The reflective volume holographic grating is manufactured using the adjusted manufacturing device to obtain an exposed reflective volume holographic grating.

[0072] Specifically, the flowchart of the method for recording a reflective volume holographic waveguide according to an embodiment of the present application is shown in FIG4 . First, a photosensitive dielectric material is prepared; second, an optical diffraction plane is prepared; and third, a holographic recording system is constructed, i.e., optical components such as a light source module, an optical diffraction plane, a reflector, and a beam splitter are selected according to specific application requirements. A laser beam is guided from a laser and split into two beams through the optical diffraction plane: an original beam and a diffracted beam. These two beams overlap in a specific area on a recording plate coated with a photosensitive dielectric material. Finally, a holographic pattern is recorded, and an electronic shutter is opened to record the interference pattern of the two beams in the photosensitive dielectric material.

[0073] After the exposed holographic grating is obtained, the performance of the manufactured holographic grating is analyzed and tested. According to the optical properties of the holographic interference sample, such as diffraction efficiency, refractive index contrast, thermal expansion coefficient, haze, long-term stability, high temperature and high humidity characteristics, etc., it is detected and analyzed, and error analysis and system improvement and optimization are carried out. According to the performance analysis results of the four holographic samples, the errors in the system are confirmed, and the entire system is improved and optimized. Finally, the formula of the photosensitive medium material, the recording parameters of the exposure system, the optical diffraction plane and other optical elements are adjusted to improve the recording effect and image quality, and further realize the manufacture of reflective volume holographic gratings with multi-degree-of-freedom modulation such as large angle and multi-region.

[0074] Furthermore, by designing an optical diffraction module, or adding optical elements such as light source modules of different wavelengths, reflectors, beam splitters, etc., the present application can flexibly change the exposure parameters to meet the manufacturing requirements of reflective volume holographic gratings with multi-degree-of-freedom modulation, so that it can be further used to modulate parameters such as grating period, duty cycle, tilt angle, etc. Furthermore, by changing the design parameters of the optical diffraction module in the mask, volume holographic gratings with different parameters can also be prepared, such as variable-period volume holographic gratings. The optical diffraction module used in the embodiment of the present application can use any optical element that can produce diffraction, which greatly expands the flexibility of preparation. The holographic exposure medium allowed by the present application is any optically sensitive medium, which can meet the needs of various fields for various materials. For example, resin can be used in the AR field that requires lightness, glass can be used in the optical computing field that requires reliability, and specially manufactured photosensitive media can be used in the military field, such as high temperature resistance, corrosion resistance, radiation resistance, etc.

[0075] This embodiment discloses a manufacturing device and a manufacturing method for a reflective volume holographic grating, wherein the manufacturing device for the reflective volume holographic grating includes a light source and an exposure module; the exposure module includes: a mask having at least one optical diffraction module, a recording medium, a coupling prism, and an exposure modulation unit; an incident recording beam provided by the light source is incident on the optical diffraction module on the mask, the optical diffraction module receives the incident recording beam and diffracts and splits the incident recording beam to obtain a reflected diffraction beam; the coupling prism adjusts the angle at which the incident recording beam is incident on the mask so that the incident recording beam is incident on the recording medium at a preset angle, and the recording medium generates interference fringes based on the input incident recording beam and the reflected diffraction beam, and changes the refractive index to form a volume holographic grating; the exposure modulation unit controls exposure parameters on the recording medium to obtain the reflective volume holographic grating after exposure. In the device of this embodiment, by adjusting the parameters of the incident recording light beam, such as wavelength, phase, polarization, amplitude, incident angle, etc., and using the exposure modulation unit to control the exposure parameters, a reflective volume holographic grating with multi-degree-of-freedom modulation is generated. The implementation method is simple, efficient, and has mass production capabilities.

[0076] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0077] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A device for manufacturing a reflective volume holographic grating, comprising: A light source and an exposure module located on the light path of the light source; The exposure module comprises: a mask having at least one optical diffraction module, a recording medium, a coupling prism and an exposure modulation unit; The light source is used to provide an incident recording light beam; The optical diffraction module on the mask is used to receive an incident recording light beam and perform diffraction and splitting on the incident recording light beam to obtain a reflected diffraction light beam; The coupling prism is used to adjust the angle at which the incident recording light beam is incident on the mask, so that the incident recording light beam is incident on the recording medium at a preset angle; The recording medium is used to generate interference fringes according to the input incident recording light beam and the reflected diffraction light beam, and to form a refractive index difference in the interference intensity enhancement area and the interference intensity reduction area to form a volume holographic grating; The exposure modulation unit is used to control the exposure parameters on the recording medium to obtain a reflective volume holographic grating after exposure.

2. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: The exposure modulation unit comprises: a gap spacer and a transparent spacer; the recording medium is embedded in the gap spacer, and the transparent spacer is arranged between the gap spacer and the mask.

3. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: Also includes: at least one rotatable semi-transparent and semi-reflective mirror disposed on the optical path of the incident recording light beam; The rotatable semi-transparent and semi-reflective mirror is used to adjust the incident angle of the incident recording light beam transmitted to the recording medium; wherein each rotatable semi-transparent and semi-reflective mirror is respectively arranged corresponding to the exposure area at different positions of the recording medium, so that the exposure parameters of the recording medium in different areas are different; the exposure parameters are one or more of the wavelength, phase, polarization, amplitude and incident angle of the incident light beam.

4. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: The exposure module further comprises: an absorption medium layer disposed on the surface of the coupling prism; The absorption medium layer is used to absorb the redundant incident recording light beam and the transmitted light beam passing through the optical diffraction module.

5. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: The surface shape of the optical diffraction module is a plane or a curved surface, and the optical diffraction module is a micro-nano optical structure or an optical micro-nano adjustable device.

6. The manufacturing device of the reflective volume holographic grating according to claim 2, wherein: The gap spacer is filled with a refractive index matching liquid; The refractive index matching liquid is used to fill the air gap between the coupling prism and the recording medium.

7. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: The recording medium is any one or more of photopolymer, photosensitive glass, photorefractive crystal, dispersible polymer liquid crystal, dichromate gelatin or silver halide gelatin.

8. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: Also includes: A focusing lens, a pinhole diaphragm and / or a collimating lens are arranged in sequence on the outgoing light path of the light source; The focusing lens is used to focus the incident recording light beam emitted by the light source; The pinhole aperture is used to filter the incident recording light beam transmitted from the focusing lens and adjust the beam diameter; The collimating lens is used to collimate the incident recording light beam emitted from the small aperture.

9. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: The mask is provided with a plurality of optical diffraction modules with different parameters; a plurality of recording areas for recording volume holographic gratings are provided at different positions; The recording areas are the same or different areas of the same medium, or the same or different areas of different media; after synchronous exposure under the exposure parameters, the recording areas respectively obtain multi-block holographic gratings with different grating parameters, and the multi-block holographic gratings are coupling-in gratings, and / or coupling-out gratings, and / or turning gratings.

10. The manufacturing device of the reflective volume holographic grating according to claim 1, wherein: The coupling prism includes a first coupling prism and a second coupling prism; The mask, the recording medium and the exposure modulation unit are arranged between the first coupling prism and the second coupling prism; The first coupling prism and the second coupling prism are used to adjust the angle at which the incident recording light beam is incident on the mask, so that the incident recording light beam is incident on the recording medium at a preset angle.

11. The manufacturing device of the reflective volume holographic grating according to claim 10, wherein: The exposure module further includes: an absorption medium layer arranged on the surface of the second coupling prism.

12. A method for manufacturing a reflective volume holographic grating, comprising: preparing a recording medium; preparing an optical diffraction module; A manufacturing device for building a reflective volume holographic grating based on a recording medium and an optical diffraction module; The reflective volume holographic grating is obtained by using the manufacturing device of the reflective volume holographic grating.

13. The method for manufacturing a reflective volume holographic grating according to claim 12, wherein: The method of obtaining the exposed reflective volume holographic grating by using the manufacturing device of the reflective volume holographic grating comprises: Adjusting the manufacturing device of the reflective volume holographic grating; The reflective volume holographic grating is manufactured by using the adjusted reflective volume holographic grating manufacturing device to obtain the exposed reflective volume holographic grating.

14. The method for manufacturing a reflective volume holographic grating according to claim 13, wherein: The manufacturing device of the reflective volume holographic grating includes the recording medium; The step of adjusting the manufacturing device of the reflective volume holographic grating comprises: The angle at which the incident recording light beam is incident on the recording medium is adjusted according to a preset incident angle.

15. The method for manufacturing a reflective volume holographic grating according to claim 13, wherein: The manufacturing device of the reflective volume holographic grating includes an exposure modulation unit; The step of adjusting the manufacturing device of the reflective volume holographic grating comprises: The exposure modulation unit is adjusted according to preset exposure parameters.

16. The method for manufacturing a reflective volume holographic grating according to claim 13, wherein: The manufacturing device of the reflective volume holographic grating comprises a mask having at least one optical diffraction module; The step of adjusting the manufacturing device of the reflective volume holographic grating comprises: The position areas of the optical diffraction modules on the mask are laid out.

17. The method for manufacturing a reflective volume holographic grating according to claim 13, wherein: The manufacturing device of the reflective volume holographic grating comprises at least one rotatable semi-transparent and semi-reflective mirror arranged on the optical path of the incident recording light beam; The step of adjusting the manufacturing device of the reflective volume holographic grating comprises: The position of the rotatable semi-transparent and semi-reflective mirror is adjusted.

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