Method for exposing multi-region distributed waveguide grating

Abstract

According to the exposure method of the multi-region distributed waveguide grating, the waveguide grating comprises a waveguide substrate, and is characterized in that a first grating, a second grating and a third grating which are independent and adjacent are arranged on the waveguide substrate, and the first grating, the second grating and the third grating are located in different regions of the waveguide substrate. Gratings with different periods and stripe directions are processed in a short-wave coherent laser double-beam holographic interference exposure mode, and a multi-area distributed waveguide grating is formed. Compared with the prior art, the exposure difficulty of the waveguide grating can be reduced, the assembling and debugging simplicity of a light path is improved, the processing efficiency is improved, the processing cost is reduced, and engineering production is easier.

Description

Technical Field

[0001] The present invention belongs to the field of augmented reality display technology, and in particular relates to a method for exposing a multi-region distributed waveguide grating. Background Art

[0002] Augmented reality display technology uses advanced optoelectronic means to present virtual display images to the observer's front field of view and effectively integrate them with the real world outside. By deeply integrating the calculated information with the real world, it provides richer information and immersive experience. In the information age, augmented reality, as the most direct way to obtain information, has extremely broad application scenarios, such as military training, medical assistance, education and learning, the gaming industry, entertainment and art, etc. It is widely regarded as the next generation of human-computer interaction display platform after mobile terminals.

[0003] Augmented reality display optical technology, typically includes free prism, geometric optical waveguide, super lens, computer generated holographic light field display, PANCAKE, etc. Free prism can obtain a larger display field of view, but the overall thickness and volume are relatively large; geometric optical waveguide can obtain a lens-like appearance, but the safety risk and low yield rate of glass stacked sheet structure are difficult to solve; augmented reality display based on super lens technology can obtain a larger field of view, but the observation eye box range is small; computer generated holographic light field display can obtain corresponding diopter adjustment, but there are usually problems of small display field of view and observation range; PANCAKE technology can support a larger display field of view and lightweight display structure, but it is difficult to directly see through the outside scene. Augmented reality technology based on waveguide grating can achieve a comprehensive balance of display field of view, observation eye box range and thin sheet appearance. However, the augmented reality display waveguide grating is based on the total internal reflection and diffraction principle of light imaging, and has the characteristics of high line density and large diameter. The existing technology usually uses a coupled prism for exposure, which has a long production cost and cycle, and reduces the efficiency of use. Summary of the invention

[0004] In view of this, the method for exposing a multi-region distributed waveguide grating provided by the present invention can reduce the difficulty of exposing a waveguide grating, improve the simplicity of optical path assembly and debugging, improve processing efficiency, reduce processing costs, and facilitate engineering production.

[0005] A method for multi-region distributed waveguide grating exposure is provided, wherein the waveguide grating comprises a waveguide substrate, on which independent and adjacent first grating, second grating and third grating are arranged, wherein the first grating, the second grating and the third grating are located in different regions of the waveguide substrate, and the method comprises:

[0006] Gratings with different periods and stripe directions are processed by short-wave coherent laser double-beam holographic interference exposure to form a multi-region distributed waveguide grating.

[0007] The technical beneficial effects of the present invention are:

[0008] High-density periodic stripes are formed by short-wavelength coherent laser dual-beam exposure, which can be freely arranged on the optical platform, avoiding the use of coupling prisms, reducing multiple interface stray light, making the optical path adjustment simpler, and ensuring exposure stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0010] Figure 1 is a schematic diagram of a waveguide grating exposure method of the present invention;

[0011] Figure 2 is a schematic diagram of the waveguide grating groove of the present invention;

[0012] Figure 3 It is a schematic diagram of substrate deviation regulation grating period of the present invention. DETAILED DESCRIPTION

[0013] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0014] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0015] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0016] like Figures 1 to 3 The method for exposing a multi-region distributed waveguide grating shown in the figure, the waveguide grating includes a waveguide substrate, characterized in that independent and adjacent first grating, second grating and third grating are arranged on the waveguide substrate (preferably, three gratings are processed on the same side of the waveguide substrate), and the first grating, the second grating and the third grating are located in different regions of the waveguide substrate, and the method includes:

[0017] Gratings with different periods and stripe directions are processed by short-wave coherent laser double-beam holographic interference exposure to form multi-region distributed waveguide gratings. Specifically,

[0018] The surface of the waveguide substrate is a plane or a curved surface, and a straight edge is reserved at the edge of the waveguide substrate, and the straight edge is used as a reference for positioning the grating stripe direction;

[0019] The first grating, the second grating and the third grating are located on the same side of the waveguide substrate and in different areas, the first grating and the third grating have the same period and different stripe directions, and the period of the second grating is greater than the period of the first grating and the third grating;

[0020] The first light beam and the second light beam are used to irradiate the waveguide substrate in an overlapping interference manner to form periodic grating stripes, the first light beam and the second light beam are ultraviolet short-wave lasers, and preferably, the overlapping interference manner of irradiating the waveguide substrate includes:

[0021] Use short-wave coherent laser double-beam holographic interference to expose on the waveguide substrate, and after development, form multiple periodic gratings that meet the design requirements;

[0022] Since each grating period and stripe direction are usually different, a two-dimensional high-precision turntable is used to adjust the stripe direction of all periodic gratings. The stripe direction is processed by one-dimensional control of the two-dimensional high-precision turntable, and the grating period is adjusted by another one-dimensional control. The turntable accuracy of the two-dimensional high-precision turntable is 0.01°~0.001°, and the wave of the ultraviolet short-wave laser is 380nm~395nm.

[0023] Gratings with different periods and stripe directions are realized by short-wave coherent laser double-beam holographic interference exposure. Beam 1 (first beam) and beam 2 (second beam) overlap and interfere in the grating area to be recorded to form periodic grating stripes. Compared with the waveguide grating exposure technology used in the prior art, the use of short-wave coherent laser exposure can effectively simplify the optical path construction, avoid the use of large-aperture coupling prisms, improve processing efficiency, reduce processing costs, and make it easier to engineer waveguide grating production.

[0024] The multi-region distributed waveguide grating of the above method is used to expand the image light in two dimensions. The image light is coupled into the waveguide substrate through the first grating and propagates to the second grating in the waveguide substrate in the form of total internal reflection. The second grating expands the image light in the waveguide substrate for multiple turns. The image light after the turns and expansion continues to propagate in the waveguide substrate. When the image light in the waveguide substrate is incident on the third grating region, the image light after the turns and expansion is diffracted and output to form a two-dimensionally expanded image light, thereby realizing the expansion of the display observation area.

[0025] Example

[0026] like Figure 1 As shown, the waveguide grating includes a waveguide substrate and a first grating, a second grating and a third grating prepared on the waveguide substrate. The first grating, the second grating and the third grating are located in different areas of the waveguide substrate. Gratings with different periods and stripe directions are realized by short-wave coherent laser double-beam holographic interference exposure. Light beam 1 and light beam 2 overlap and interfere in the grating area to be recorded to form periodic grating stripes. The specific period wavelength is recorded by tilting the grating substrate away from the recording, and the specific grating stripe direction is formed by rotating the photosensitive substrate with a turntable. The grating in a specific area is realized by blocking a specific area. Finally, after the exposure and development are completed by this method, a surface relief grating is formed. The schematic diagram of the waveguide grating groove is shown as follows. Figure 2 The process shown is as follows:

[0027] 1) preparing a photosensitive dry plate by spin coating or scraping photoresist on a glass substrate;

[0028] 2) Interference periodic fringes are formed by superposition of two 390nm blue-violet coherent laser beams. Taking the first grating and the third grating with a period of 410nm as an example, the double-beam interference angle is 28.88°, and the deviation angle of the glass substrate is 10°. The specific calculation equation of the grating is as follows:

[0029]

[0030] N new =1 / 410

[0031] λ=390

[0032] Set the deviation angle δ = 10 degrees

[0033] The interference angle α is calculated to be 28.88 degrees.

[0034] Schematic diagram of substrate deviation control recording cycle, such as Figure 3 shown.

[0035] 3) First, the first grating is exposed so that the first grating is in the same direction as the interference fringes. After the first grating is exposed, the glass substrate is rotated 112° by the turntable according to the angle between the first grating and the third grating to record the third grating. When a specific grating area is exposed, other non-exposed areas need to be shielded;

[0036] 4) performing exposure of the second grating 366.6nm grating in the 390nm coherent laser double-path interference optical path, with an optical path interference angle of 32.69° and a deviation angle of 10°; performing alignment of the grating lines before exposure, placing the substrate that has completed the exposure of the first grating and the third grating back into the exposure fixture, rotating the lower turntable and the upper turntable so that the third grating can adjust the thickest moiré fringes in the 366.6nm light field, rotating the lower turntable back to its original position, and rotating the upper turntable according to the angular relationship between the third grating lines and the second grating lines so that the second grating lines are parallel to the light field lines;

[0037] In order to further suppress stray light during the waveguide grating exposure process, a light-absorbing material, such as black paint or matte tape, may be attached or coated on the back of the glass substrate.

[0038] High-density periodic stripes are formed by short-wavelength coherent laser dual-beam exposure, which can be freely arranged on the optical platform, avoiding the use of coupling prisms, reducing multiple interface stray light, making the optical path adjustment simpler, and ensuring exposure stability and reliability.

[0039] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for exposing a multi-region distributed waveguide grating, the waveguide grating comprising a waveguide substrate, characterized in that: An independent and adjacent first grating, a second grating and a third grating are arranged on a waveguide substrate, wherein the first grating, the second grating and the third grating are located in different areas of the waveguide substrate. The method comprises: Gratings with different periods and stripe directions are processed by short-wave coherent laser double-beam holographic interference exposure to form a multi-region distributed waveguide grating.

2. The method according to claim 1, characterized in that The surface of the waveguide substrate is a plane or a curved surface, and a straight edge is reserved at the edge of the waveguide substrate, and the straight edge is used as a reference for positioning the direction of the grating stripes.

3. The method according to claim 1, characterized in that The first grating, the second grating and the third grating are located on the same side of the waveguide substrate and in different areas. The first grating and the third grating have the same period and different stripe directions. The second grating period is greater than the first grating and the third grating period.

4. The method according to claim 1, characterized in that The first light beam and the second light beam are used to irradiate the waveguide substrate in an overlapping interference manner to form periodic grating stripes, and the first light beam and the second light beam are ultraviolet short-wave lasers.

5. The method according to claim 4, characterized in that The overlapping interference method of irradiating the waveguide substrate includes: Use short-wave coherent laser double-beam holographic interference to expose on the waveguide substrate, and after development, form multiple periodic gratings that meet the design requirements; A two-dimensional high-precision turntable is used to adjust the stripe orientation of all periodic gratings, wherein the stripe orientation is processed through one-dimensional control of the two-dimensional high-precision turntable, and the grating period is adjusted through another one-dimensional control.

6. The method according to claim 5, characterized in that The turntable accuracy of the two-dimensional high-precision turntable is 0.01° to 0.001°, and the wavelength of the ultraviolet short-wave laser is 380nm to 395nm.

7. The method according to claim 1, characterized in that Multi-area distributed waveguide gratings are used to expand image light in two dimensions.

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