Two-dimensional holographic grating exposure device and industrial production method

Abstract

The invention discloses a two-dimensional holographic grating exposure device and an industrial production method. The two-dimensional holographic grating exposure device is composed of a light splitting collimation light path at the front end and an exposure module at the rear end. In a light splitting and collimating light path at the front end, light emitted by a laser (121) is modulated by a power modulator (111), passes through an electronic shutter (131) and then is split into a first sub-light beam (151), a second sub-light beam (152) and a third sub-light beam (153) by a light splitting unit (14), the three paths of light reach a first diaphragm, a second diaphragm and a third diaphragm after being subjected to turning, polarization modulation, beam expansion and collimation, and the spot size and shape of the light are limited through the diaphragms. The three beams of light passing through the diaphragm are introduced into the rear-end exposure module, the first path of light and the third path of light pass through the first coupling prism, the second coupling prism, the substrate material and the base material and then intersect with the second path of light passing through the substrate material and the base material at the holographic material, and the three beams of light interfere with each other to form a two-dimensional grating. The device can perform grating exposure in two dimensions at the same time, the two-dimensional grating exposure process is simplified, and the two-dimensional grating manufacturing efficiency is improved.

Description

Technical Field

[0001] The invention relates to a two-dimensional holographic grating exposure device and an industrial production method, belonging to the technical field of holographic grating exposure. Background Art

[0002] As a diffractive optical element made by interference principle, holographic grating is widely used because of its low cost, large-scale manufacturing and high diffraction efficiency when the Bragg condition is met, especially in the fields of augmented reality (AR) and virtual reality (VR). For example, in volume holographic diffraction waveguides, holographic gratings are used as light coupling, coupling and turning elements. However, in existing volume holographic waveguides, most holographic gratings are still one-dimensional gratings. Usually, two one-dimensional gratings are required to be combined in space in the waveguide to achieve the effect of two-dimensional gratings, which will undoubtedly increase the volume of the system. Based on the requirements of small and light AR / VR display devices in the consumer electronics field, how to reduce the volume while maintaining or optimizing the performance parameters of existing products has become a difficult problem to be solved at present. Replacing two one-dimensional gratings with a single two-dimensional grating is an effective way to reduce the volume of the system.

[0003] The manufacture of two-dimensional gratings requires recording two interference light fields in the holographic material. Some people use double exposure to successively record two one-dimensional gratings. The two one-dimensional gratings are superimposed to form a two-dimensional grating. This method has low production efficiency, and due to the photosensitive nature of the holographic material, the activity of the material decreases after the first exposure, affecting the grating formation of the second exposure, and finally affecting the performance of the two-dimensional grating, resulting in limited practical use. Summary of the invention

[0004] The purpose of the present invention is to realize one-time exposure to produce a two-dimensional grating and provide an industrial production method for a two-dimensional holographic grating, which is applied to the field of volume holographic diffraction optical waveguides and provides a two-dimensional holographic grating exposure device and an industrial production method.

[0005] The technical solution implemented by the present invention is as follows: a two-dimensional holographic grating exposure device includes a front-end splitting and collimating optical path and a rear-end exposure module.

[0006] The front-end splitting and collimating optical path includes a light source and its power modulator, an electronic shutter and a splitting unit; the splitting unit is used to split the main light beam into a first sub-beam, a second sub-beam and a third sub-beam; the first sub-beam, the second sub-beam and the third sub-beam are propagated along the first optical path, the second optical path and the third optical path respectively.

[0007] The first optical path includes a first turning unit, a first polarization unit, a first beam expansion unit, a first collimation unit and a first aperture; the second optical path includes a second polarization unit, a second beam expansion unit, a second collimation unit and a second aperture; the third optical path includes a second turning unit, a third polarization unit, a third beam expansion unit, a third collimation unit and a third aperture.

[0008] The first sub-beam and the second sub-beam interfere to form an interference pattern in a first direction, the second sub-beam and the third sub-beam interfere to form an interference pattern in a second direction, and the interference patterns in the two directions are superimposed to form a two-dimensional interference pattern; the second sub-beam serves as a multiplexed beam, and the device realizes a two-dimensional interference pattern using only three beams of light.

[0009] The first direction and the second direction refer to the directions of the interference pattern, that is, the stripe directions of the generated holographic grating. The first direction and the second direction are intended to distinguish the directions of the interference pattern. Different directions mean different dimensions, and are not limited to orthogonal two-dimensional gratings parallel to the X-axis and the Y-axis, respectively.

[0010] The rear-end exposure module includes a first coupling prism, a second coupling prism, a substrate material, a base material, a holographic material and a light absorbing element; the first coupling prism is used to couple in a first sub-beam; the second coupling prism is used to couple in a third sub-beam; the substrate material is located above the coupling prism, the base material is located above the substrate material, the holographic material is located above the base material, and the light absorbing element is located above the holographic material; after the first sub-beam and the third sub-beam pass through the coupling prism, the substrate material and the base material, they intersect with the second sub-beam that passes through the substrate material and the base material at the holographic material, and interfere with each other to form a two-dimensional grating.

[0011] The rear-end exposure module uses a method of stacking prisms and substrate materials, wherein the prism is used because when the holographic grating is applied to waveguide display, in order to make one of the light beams meet the total reflection transmission condition, prism coupling must be used, and the two-dimensional grating needs to use two prisms to couple the first sub-beam and the third sub-beam; and the substrate material is used to make the light coupled out from the prism continue to propagate for a distance along the original direction, so that the three beams of light overlap at the area to be exposed of the holographic material on the substrate, avoiding mutual interference between the substrate and the prism.

[0012] The light source includes at least one laser, and when there are more than one laser, at least one beam combiner is required; the electronic shutter is located at the output end of the laser, and the light splitting unit is located at the output end of the electronic shutter; The beam splitting unit is a combiner with three reflective surfaces, each of which needs to be coated to control the reflectivity so that the energy of the three sub-beams split by the beam splitter is equal or approximately equal; The first turning unit and the second turning unit each include at least one reflector, so that the first light path, the second light path, and the third light path maintain an appropriate distance and do not interfere with each other; The first optical path, the second optical path and the third optical path all include a polarization unit, a beam expansion unit, a collimation unit and an aperture, which are arranged in a front-to-back order; The polarization unit is a quarter wave plate or a half wave plate, which is an optical element used to adjust the polarization state and intensity of the light beam; The beam expansion unit is a spatial filter, which is used to expand the beam diameter; The collimating unit is a convex lens or an off-axis parabolic mirror, which is used to obtain collimated parallel light; The aperture is used to limit the spot size and shape of the light beam, so that the spots of the first sub-beam, the second sub-beam and the third sub-beam propagating to the surface of the holographic material just overlap.

[0013] In the rear-end exposure module, the refractive indexes of the first coupling prism, the second coupling prism, the substrate material, the base material and the holographic material are the same or very close.

[0014] The first coupling prism couples the first sub-beam passing through the first aperture, and the second coupling prism couples the third sub-beam passing through the third aperture; the propagation directions of the first sub-beam and the third sub-beam are different, and the propagation directions do not change after being coupled into the prism.

[0015] The substrate material is in optical contact with the first coupling prism and the second coupling prism to ensure that the propagation directions of the first sub-beam and the third sub-beam emitted from the coupling prism and incident on the substrate material do not change; refractive index matching oil is filled between the contact surfaces of the first coupling prism and the second coupling prism and the substrate material to ensure the optical contact between the coupling prism and the substrate material.

[0016] The base material is in optical contact with the substrate material to ensure that the propagation directions of the first sub-beam, the second sub-beam and the third sub-beam emitted from the substrate material and incident on the substrate material do not change; refractive index matching oil is filled between the contact surfaces of the first coupling prism and the second coupling prism and the substrate material to ensure the optical contact between the coupling prism and the substrate material.

[0017] The rear-end exposure module is used to receive the first sub-beam, the second sub-beam and the third sub-beam after passing through the first aperture, the second aperture and the third aperture; after the first sub-beam and the third sub-beam pass through the coupling prism, the substrate material and the base material, they intersect with the second sub-beam that passes through the substrate material and the base material at the holographic material, and interfere with each other to form a two-dimensional grating; the two-dimensional grating is on the base material.

[0018] The holographic material is provided with a protective layer, the protective layer is attached with a light absorbing element, and the light absorbing element is in optical contact with the holographic material protective layer; refractive index matching oil is filled between the light absorbing element and the holographic material protective layer to ensure that the light absorbing element and the holographic material protective layer are in optical contact; the absorption spectrum of the light absorbing glass at least includes the spectrum of the light source.

[0019] The invention discloses an industrial production method of a two-dimensional holographic grating, which is completed by five steps: holographic box production, holographic box alignment installation, automatic exposure program startup, holographic box removal and post-processing.

[0020] The holographic box is manufactured by coating so that the holographic material is evenly distributed on the surface of the base material, and the surface of the material is covered with a protective layer; the holographic box is installed in position, the manufactured holographic box is placed on the substrate material, and the coherent light beam is irradiated to the area to be exposed of the holographic box; the automatic exposure program is started, the shutter control program is started, and the two-dimensional grating is automatically exposed according to the designed program to form the two-dimensional grating; the holographic box is removed, and after the exposure program is finished, the holographic box with the two-dimensional grating formed is removed from the substrate material; the post-processing is to make the unreacted holographic material react completely through ultraviolet curing to make the two-dimensional grating firmly formed.

[0021] The beneficial effects of the present invention are as follows: the present invention provides a two-dimensional holographic grating exposure device, including a front-end splitting collimation optical path and a rear-end exposure module. The front-end splitting collimation optical path includes a light source and its power modulator, an electronic shutter, and a splitting unit. The rear-end exposure module is used to receive the first, second, and third sub-beams after passing through the first, second, and third apertures; after the first and third sub-beams pass through the coupling prism, the substrate material, and the base material, they intersect with the second sub-beam that passes through the substrate material and the base material at the holographic material, and interfere with each other to form a two-dimensional grating. The device realizes one-time exposure to produce a two-dimensional grating.

[0022] The present invention adopts a light splitting unit of a combiner with three reflecting surfaces, each of which needs to be coated to control the reflectivity, so that the energy of the three sub-beams separated by the beam splitter is equal or approximately equal.

[0023] The present invention uses a beam splitter to divide the light emitted by the laser into three sub-beams. The first sub-beam and the second sub-beam interfere to form an interference pattern in the first direction. The second sub-beam and the third sub-beam interfere to form an interference pattern in the second direction. The interference patterns in the two directions are superimposed to form a two-dimensional interference pattern. The present invention uses the second sub-beam as a multiplexed beam and realizes a two-dimensional interference pattern with only three beams, which is one less than the four beams of the traditional technology, simplifies the optical path, reduces the number of device components, and reduces the cost.

[0024] At the same time, based on the above two-dimensional holographic grating exposure device, a two-dimensional holographic grating industrial production method is proposed. The method is completed by five steps: holographic box production, holographic box alignment installation, automatic exposure program startup, holographic box removal, and post-processing. The use of the above two-dimensional holographic grating exposure device and industrial production method improves the production efficiency and product performance of the two-dimensional holographic grating. The produced two-dimensional grating can be applied to the field of volume holographic diffraction optical waveguides, effectively reducing the system volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a front-end splitting and collimating optical path of a two-dimensional holographic grating exposure device provided in an embodiment of the present application; Figure 2a It is a front view structural schematic diagram of the rear end exposure module of the two-dimensional holographic grating exposure device of the present invention; Figure 2b It is a rear view structural schematic diagram of the rear end exposure module of the two-dimensional holographic grating exposure device of the present invention; Figure 2c It is a left-side structural schematic diagram of a rear-end exposure module of a two-dimensional holographic grating exposure device of the present invention; Figure 2d It is a right view structural schematic diagram of the rear end exposure module of the two-dimensional holographic grating exposure device of the present invention; Figure 3a It is a schematic diagram of the isometric side view structure of the rear end exposure module of the two-dimensional holographic grating exposure device of the present invention; Figure 3b It is a schematic diagram of the front sight frame structure of the rear-end exposure module of the two-dimensional holographic grating exposure device of the present invention; Figure 3c It is a schematic diagram of the right sight frame structure of the rear-end exposure module of the two-dimensional holographic grating exposure device of the present invention; Figure 4 It is a schematic diagram of the front-end light splitting and collimating optical path structure of the two-dimensional holographic grating exposure device of the present invention; Figure 5 It is a schematic diagram of the industrial production method of the two-dimensional holographic grating exposure device of the present invention; Figure 6a It is a schematic diagram of the structure of the commonly used two-dimensional pupil expansion holographic diffraction optical waveguide; Figure 6b The schematic diagram of the structure of the two-dimensional grating made by the two-dimensional holographic grating exposure device of the present invention is applied to the volume holographic diffraction optical waveguide. DETAILED DESCRIPTION

[0026] This embodiment provides a two-dimensional holographic grating exposure device and an industrial production method, wherein the two-dimensional holographic grating exposure device includes a front-end splitting and collimating optical path and a rear-end exposure module.

[0027] like Figure 1As shown, the front-end spectroscopic collimating optical path 10 of the device of this embodiment includes a power modulator 111, a light source 121, an electronic shutter 131, a spectroscopic unit 14, a first turning unit 161, 162, a second turning unit 163, 164, a first polarization unit 171, a second polarization unit 172, a third polarization unit 173, a first beam expanding unit 181, a second beam expanding unit 182, a third beam expanding unit 183, a first collimating unit 191, a second collimating unit 192, a third collimating unit 193, a first aperture 201, a second aperture 202, a third aperture 203.

[0028] The power modulation device 111 in this embodiment is used to modulate the output power of the light source. The electronic shutter 131 is at the output end of the light source 121. When the shutter 131 is opened, the light is transmitted backward. The light splitting unit 14 divides the light transmitted from the shutter 131 into a first sub-beam 151, a second sub-beam 152, and a third sub-beam 153. The first sub-beam 151 is deflected by the first deflection units 161 and 162, and is incident on the first polarization unit 171. After being polarized and intensity modulated by the polarization unit 171, it is emitted to the first beam expansion unit 181. After the beam diameter is expanded, it is collimated by the first collimation unit 191, and then reaches the first aperture 201. The first aperture 201 limits its spot size and shape. The second sub-beam 152 is incident on the second polarization unit 172, and is polarized and intensity modulated by the second polarization unit 172, and is emitted to the second beam expansion unit 1 82, after the beam diameter is expanded, it is collimated by the second collimating unit 192, and then reaches the second aperture 202, and its spot size and shape are limited by the second aperture 202; wherein the third sub-beam 153 is turned by the third turning units 163 and 164, and is incident toward the third polarizing unit 173, and is polarized and intensity modulated by the polarizing unit 173, and is emitted to the third beam expanding unit 183, after the beam diameter is expanded, it is collimated by the third collimating unit 193, and then reaches the third aperture 203, and its spot size and shape are limited by the third aperture 203.

[0029] The power modulation device 111 in this embodiment is used to modulate the output power of the light source so that the intensity of light incident on the holographic material conforms to the photosensitivity characteristics of the holographic material.

[0030] The spectroscopic unit 14 in this embodiment includes a first spectroscope 141, a second spectroscope 142, and a first reflector 143; wherein the surfaces of the first spectroscope 141, the second spectroscope 142, and the first reflector 143 need to be coated to ensure that the light energy emitted by the light source 121 is evenly divided into three equal parts, so that the light intensities of the first sub-beam 151, the second sub-beam 152, and the third sub-beam 153 finally incident on the holographic material are as equal as possible.

[0031] In this embodiment, the first turning unit may be a reflector combination including a reflector 161 and a reflector 162 , and the second turning unit may be a reflector combination including a reflector 163 and a reflector 164 .

[0032] In this embodiment, the first polarization unit 171, the second polarization unit 172, and the third polarization unit 173 can be a half-wave plate or a quarter-wave plate, or a combination of the two; their purpose is to adjust the polarization states of the first sub-beam 151, the second sub-beam 152, and the third sub-beam 153 to ensure that the first sub-beam 151, the second sub-beam 152, and the third sub-beam 153 finally incident on the holographic material have the same polarization state, so the polarization unit here has the function of polarization compensation.

[0033] In this embodiment, the first beam expanding unit 181, the second beam expanding unit 182 and the third beam expanding unit 183 may be spatial filters.

[0034] In this embodiment, the first collimating unit 191, the second collimating unit 192 and the third collimating unit 193 may be a convex lens, a Fourier transform lens, or a concave parabolic mirror.

[0035] In this embodiment, the first aperture 201, the second aperture 202, and the third aperture 203 do not necessarily have the same size and shape, but it is required that by limiting the shapes and sizes of the first aperture 201, the second aperture 202, and the third aperture 203, the spot sizes and shapes of the first sub-beam 151, the second sub-beam 152, and the third sub-beam 153 that are finally converged onto the plane of the holographic material are the same.

[0036] like Figure 2a-2d As shown, Figure 2a is a front view structural diagram of the rear end exposure module 20, Figure 2b is a rear view structural diagram of the rear exposure module 20, Figure 2c It is a left view structural diagram of the rear end exposure module 20. Figure 2d It is a right view structural diagram of the rear end exposure module 20.

[0037] The rear exposure module 20 in this embodiment includes a first coupling prism 211, a second coupling prism 212, a substrate material 22, a base material 23, a holographic material 24 and a light absorbing element 25. Figure 2a-2d , the relative positions of the components in the rear exposure module can be easily obtained. The first coupling prism 211 and the second coupling prism 212 are both located below the substrate material 22, and have a right angle surface close to the lower surface of the substrate material 22; the base material 23 is located above the substrate material 22 and close to the substrate material 22; the holographic material 24 is located on the base material 23; and the light absorbing element 25 is attached to the holographic material 24.

[0038] like Figure 3a The figure shows an isometric side view of the rear exposure module 20. The light 151 passing through the first aperture 201, the light 152 passing through the second aperture, and the light 153 passing through the third aperture are respectively introduced into the rear exposure module along different paths by reflectors (not shown). Figure 3b The front sight frame structure diagram of the rear exposure module 20 is shown. The first sub-beam 151 is incident from the inclined surface of the first coupling prism 211, and is transmitted through the coupling prism 211, the substrate material 22, the substrate material 23, and reaches the holographic material 24; the second sub-beam 152 is directly transmitted through the substrate material 22, the substrate material 23, and reaches the holographic material 24; the first sub-beam 151 and the second sub-beam 152 intersect at the holographic material 24, and interfere to form a one-dimensional grating. Figure 3c The figure shows the right sight frame structure diagram of the rear-end exposure module 20, in which the second sub-beam 152 is directly transmitted through the substrate material 22, the base material 23, and reaches the holographic material 24; the third sub-beam 153 is incident from the inclined surface of the second coupling prism 212, and is transmitted through the coupling prism 212, the substrate material 22, the base material 23, and reaches the holographic material 24; the second sub-beam 152 and the third sub-beam 153 intersect at the holographic material 24, and interfere to form a one-dimensional grating; the two-to-two intersection interference of the three beams of light occurs simultaneously, so the superposition of two one-dimensional gratings can generate a two-dimensional grating at one time.

[0039] like Figure 3b As shown, the first sub-beam 151 and the second sub-beam 152 interfere at the holographic material 24, and the direction of the generated holographic grating stripes is parallel to the x-axis; Figure 3c As shown, the second sub-beam 152 and the third sub-beam 153 interfere at the holographic material 24, and the direction of the generated holographic grating stripes is parallel to the y-axis; the stripes of the two gratings are orthogonal to form a two-dimensional grating.

[0040] In this embodiment, the first sub-beam 151 is vertically incident from the inclined surface of the first coupling prism 211 , the second sub-beam 152 is vertically incident from the lower surface of the substrate material 22 , and the third sub-beam 153 is vertically incident from the inclined surface of the second coupling prism 212 .

[0041] In this embodiment, the base angles of the first coupling prism 211 and the second coupling prism 212 can be changed according to actual needs.

[0042] In this embodiment, the positions of the first coupling prism 211 and the second coupling prism 212 at the bottom surface of the substrate material 22 can be translated or rotated as required.

[0043] In this embodiment, the first coupling prism 211 , the second coupling prism 212 , the substrate material 22 , the base material 23 and the holographic material 24 are all made of transparent materials, and their refractive indices are the same, but slight differences are allowed.

[0044] In this embodiment, optical contact is maintained between the first coupling prism 211 and the substrate material 22, and between the second coupling prism 212 and the substrate material 22, such as by applying a refractive index matching liquid between the contact interfaces.

[0045] The thickness and shape of the substrate material glass in this embodiment can be adjusted according to the requirements as a degree of freedom to ensure that the three sub-beams intersect exactly at the holographic material 24 .

[0046] In this embodiment, the substrate material 22 and the base 23 are in optical contact with each other, for example, by applying a refractive index matching liquid between the contact interfaces.

[0047] The surface of the holographic material 24 in this embodiment has a protective layer, and the protective layer maintains optical contact with the light absorbing element 25, such as by coating a refractive index matching liquid between the contact interfaces.

[0048] The absorption spectrum of the light absorbing element 25 in this embodiment should at least include the spectrum of the light source 121 .

[0049] The light source in this embodiment includes at least one laser and a beam combiner; wherein each laser is arranged at each input end of the beam combiner, and the light splitting unit is arranged at the output end of the beam combiner.

[0050] like Figure 4 As shown, in this embodiment, at least one laser includes a red laser 121, a blue laser 122, and a green laser 123, and the beam combiner is a beam combining prism 301. The beam combining prism 301 has a first incident surface, a second incident surface, a third incident surface, and an exit surface; the red laser 121 is arranged at the first incident surface of the beam combining prism 301, the green laser 123 is arranged at the second incident surface of the beam combining prism 301, and the blue laser 122 is arranged at the third incident surface of the beam combining prism 301.

[0051] The beam combining prism 301 in this embodiment is an X-prism, which is formed by gluing four right-angle prisms. The diagonal surfaces of the X-prism are respectively provided with a first dichroic film and a second dichroic film that are orthogonal to each other, wherein the first dichroic film is a dichroic film that reflects red light and transmits green light and blue light; the second dichroic film is a dichroic film that reflects blue light and transmits red light and green light. Figure 4 As shown, the beam combining prism 301 can combine the red light emitted by the red laser 121, the green light emitted by the green laser 123, and the blue light emitted by the blue laser 122 into a laser beam for output. In practical applications, the arrangement of the lasers and the structure of the beam combining prism 301 can be set according to actual needs, and the beam combiner can also be other suitable spectral beam combining devices, and there is no need to stick to the limitations in this embodiment.

[0052] The holographic grating exposure in this embodiment adopts a combined-color laser light source, and the two-dimensional grating generated by the exposure can be applied to the diffraction of red, green and blue light.

[0053] This embodiment provides an industrial production method of a two-dimensional holographic grating, such as Figure 5 shown.

[0054] The production device of the method is composed of the above-mentioned device. The industrial production method of the two-dimensional holographic grating is completed by five steps: holographic box production S1, holographic box alignment installation S2, automatic exposure program start S3, holographic box removal S4, and post-processing S5.

[0055] In the holographic box manufacturing S1 of this embodiment, the holographic material 24 can be evenly spread on the surface of the base material 23 by coating or other methods. The surface of the holographic material 24 is covered with a protective layer. The base material 23, the holographic material 24 and the protective layer together form a holographic box.

[0056] The holographic box alignment installation S2 in this embodiment can place the manufactured holographic box on the substrate material 22, and make the coherent light beam irradiate the area to be exposed of the holographic box; specifically, firstly, the upper surface of the substrate material 22 is coated with refractive index oil, and then the holographic box is placed in the clamping tool (not shown) on the upper surface of the substrate material 22, and the refractive index oil is coated on the surface of the holographic box, and the light absorbing glass 25 is covered on the upper surface of the holographic box. The purpose of setting the clamping tool is to make the coherent light just irradiate the area to be exposed of the holographic box after the holographic box is fixed.

[0057] The automatic exposure program in this embodiment starts S3, which can start the shutter control program to automatically expose according to the designed program to form a two-dimensional grating. Specifically, the shutter control program can automatically control the switch state of the shutter, thereby controlling the exposure time.

[0058] In the holographic box removal S4 of this embodiment, the holographic box on which the two-dimensional grating has been formed needs to be removed from the substrate material after the exposure program is finished.

[0059] In the post-processing S5 of this embodiment, the unreacted holographic material can be completely reacted by UV curing or other methods, so that the two-dimensional grating is formed stably.

[0060] The purpose of the present invention is to provide a two-dimensional holographic grating exposure device and an industrial production method, and the device and method can produce a two-dimensional grating by one-time exposure, thereby improving the production efficiency and product performance of the two-dimensional holographic grating. The produced two-dimensional grating can be applied to the field of volume holographic diffraction optical waveguides, effectively reducing the system volume.

[0061] This embodiment can apply the two-dimensional holographic grating manufactured by the above-mentioned device and production method to the field of volume holographic diffraction optical waveguide, and use one two-dimensional grating to replace the original two one-dimensional gratings, thereby effectively compressing the system volume.

[0062] like Figure 6a As shown, Figure 6a The middle one is the current mainstream diffraction waveguide design method. In order to obtain a larger image observable area, that is, the eye movement range, the pupil needs to be expanded in two directions using a grating. Figure 6a The coupling grating 511 in the middle waveguide 51 couples the image light into the waveguide, firstly expands the pupil in the y direction through the turning grating 512, then expands the pupil in the x direction through the coupling grating, and finally couples it out to the human eye, so as to obtain a larger eye movement range. Figure 6b As shown, if the two-dimensional grating manufactured by the above method is directly used, one two-dimensional grating 522 can be used to directly replace two one-dimensional gratings to achieve pupil expansion in two directions, thus effectively compressing the system volume.

Claims

1. A two-dimensional holographic grating exposure device, characterized in that: The device comprises a front-end light splitting and collimating optical path and a rear-end exposure module; The front-end splitting and collimating optical path includes a light source and a power modulator thereof, an electronic shutter and a splitting unit; the splitting unit is used to split the main light beam into a first sub-beam, a second sub-beam and a third sub-beam; the first sub-beam, the second sub-beam and the third sub-beam propagate along the first optical path, the second optical path and the third optical path respectively; The beam splitting unit is a combiner with three reflective surfaces, each of which needs to be coated to control the reflectivity so that the energy of the three sub-beams split by the beam splitter is equal or approximately equal; The rear-end exposure module comprises a first coupling prism, a second coupling prism, a substrate material, a base material, a holographic material and a light absorbing element; the first coupling prism is used to couple in the first sub-beam; The second coupling prism is used to couple the third sub-beam; the substrate material is located above the coupling prism, the base material is located above the substrate material, the holographic material is located above the base material, and the light absorbing element is located above the holographic material; after the first sub-beam and the third sub-beam pass through the coupling prism, the substrate material, and the base material, they intersect with the second sub-beam that passes through the substrate material and the base material at the holographic material, and interfere with each other to form a two-dimensional grating; thereby realizing one-time exposure to produce a two-dimensional grating; The first sub-beam and the second sub-beam interfere to form an interference pattern in a first direction, the second sub-beam and the third sub-beam interfere to form an interference pattern in a second direction, and the interference patterns in the two directions are superimposed to form a two-dimensional interference pattern; the second sub-beam is used as a multiplexed beam, and the device realizes a two-dimensional interference pattern using only three beams of light; The rear-end exposure module uses a method of stacking prisms and substrate materials, wherein the prism is used because when the holographic grating is applied to waveguide display, in order to make one of the light beams meet the total reflection transmission condition, prism coupling must be used, and the two-dimensional grating needs to use two prisms to couple the first sub-beam and the third sub-beam; and the substrate material is used to make the light coupled out from the prism continue to propagate for a distance along the original direction, so that the three beams of light overlap at the area to be exposed of the holographic material on the substrate, avoiding mutual interference between the substrate and the prism.

2. A two-dimensional holographic grating exposure device according to claim 1, characterized in that: The light source includes at least one laser, and when there are more than one laser, at least one beam combiner is required; the electronic shutter is located at the output end of the laser, and the light splitting unit is located at the output end of the electronic shutter; The first optical path includes a first turning unit, a first polarizing unit, a first beam expanding unit, a first collimating unit and a first aperture; the second optical path includes a second polarizing unit, a second beam expanding unit, a second collimating unit and a second aperture; the third optical path includes a second turning unit, a third polarizing unit, a third beam expanding unit, a third collimating unit and a third aperture; The first turning unit and the second turning unit each include at least one reflector, so that the first light path, the second light path, and the third light path maintain an appropriate distance and do not interfere with each other; The first optical path, the second optical path and the third optical path all include a polarization unit, a beam expansion unit, a collimation unit and an aperture, which are arranged in a front-to-back order; The polarization unit is a quarter wave plate or a half wave plate, which is an optical element used to adjust the polarization state and intensity of the light beam; The beam expansion unit is a spatial filter, which is used to expand the beam diameter; The collimating unit is a convex lens or an off-axis parabolic mirror, which is used to obtain collimated parallel light; The aperture is used to limit the spot size and shape of the light beam, so that the spots of the first sub-beam, the second sub-beam and the third sub-beam propagating to the surface of the holographic material just overlap.

3. The two-dimensional holographic grating exposure device according to claim 1, characterized in that: Said In the rear-end exposure module, the refractive indexes of the first coupling prism, the second coupling prism, the substrate material, the base material and the holographic material are the same or very close.

4. The two-dimensional holographic grating exposure device according to claim 1, characterized in that: The first coupling prism couples the first sub-beam passing through the first aperture, and the second coupling prism couples the third sub-beam passing through the third aperture; the propagation directions of the first sub-beam and the third sub-beam are different, and the propagation directions do not change after being coupled into the prism.

5. The two-dimensional holographic grating exposure device according to claim 1, characterized in that: The substrate material is in optical contact with the first coupling prism and the second coupling prism, ensuring that the propagation directions of the first sub-beam and the third sub-beam emitted from the coupling prism and incident on the substrate material do not change; Refractive index matching oil is filled between the contact surfaces of the first coupling prism and the second coupling prism and the substrate material to ensure optical contact between the coupling prism and the substrate material.

6. The two-dimensional holographic grating exposure device according to claim 1, characterized in that: The base glass is in optical contact with the substrate material to ensure that the propagation directions of the first sub-beam, the second sub-beam and the third sub-beam emitted from the substrate material and incident on the substrate material do not change; refractive index matching oil is filled between the contact surfaces of the first coupling prism and the second coupling prism and the substrate material to ensure the optical contact between the coupling prism and the substrate material.

7. The two-dimensional holographic grating exposure device according to claim 1, characterized in that: The rear-end exposure module is used to receive the first sub-beam, the second sub-beam and the third sub-beam after passing through the first aperture, the second aperture and the third aperture; after the first sub-beam and the third sub-beam pass through the coupling prism, the substrate material and the base material, they intersect with the second sub-beam that passes through the substrate material and the base material at the holographic material, and interfere with each other to form a two-dimensional grating; the two-dimensional grating is on the base material.

8. The two-dimensional holographic grating exposure device according to claim 1, characterized in that: The holographic material is provided with a protective layer, the protective layer is attached with a light absorbing element, and the light absorbing element is in optical contact with the holographic material protective layer; refractive index matching oil is filled between the light absorbing element and the holographic material protective layer to ensure that the light absorbing element and the holographic material protective layer are in optical contact; the absorption spectrum of the light absorbing glass at least includes the spectrum of the light source.

9. An industrial production method of a two-dimensional holographic grating using a two-dimensional holographic grating exposure device according to any one of claims 1 to 8, characterized in that: The method comprises five steps: holographic box manufacturing, holographic box alignment installation, automatic exposure program startup, holographic box disassembly and post-processing.

10. The industrial production method of a two-dimensional holographic grating according to claim 9, characterized in that: The holographic box is manufactured by coating so that the holographic material is evenly spread on the surface of the base material, and the surface of the material is covered with a protective layer; the holographic box is installed in alignment, the manufactured holographic box is placed on the base material, and the coherent light beam is irradiated to the area of ​​the holographic box to be exposed; The automatic exposure program is started, the shutter control program is started, and the two-dimensional grating is automatically exposed according to the design program to form the two-dimensional grating; after the holographic box is removed, after the exposure program is finished, the holographic box with the two-dimensional grating formed is removed from the substrate material; the post-processing is to make the unreacted holographic material react completely by ultraviolet curing to make the two-dimensional grating firmly formed.

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