Exposure method of volume holographic display equipment

Abstract

The invention discloses an exposure method of volume holographic display equipment, which comprises the following steps of: rotating a substrate and a grating vector in three dimensions and adjusting a rotation angle, so that an included angle between rotated object light and reference light and a normal line of a substrate is equal to a Brewster angle or is close to the range of + / -10 degrees of the Brewster angle, thereby realizing prism-free and matching-liquid-free double-beam exposure; the exposure light path is almost free of stray light, the grating diffraction efficiency and the grating quality are improved, and the final display effect is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of holographic display equipment, and in particular to an exposure method for a volume holographic display equipment. Background Art

[0002] The dual-beam exposure scheme of the existing volume holographic display device ensures that the light transmission in the waveguide meets the total reflection condition. During exposure, it requires prisms and matching liquids for auxiliary exposure. The prisms and matching introduced in the optical path will also cause a large amount of stray light and increase the number of grating derivative orders, reduce the diffraction efficiency of a single grating order, and increase the grating haze, thus affecting the final display effect. Since the inherent shrinkage rate of the material after the holographic material is exposed and cured is not considered during exposure, the grating vector and period change is caused, resulting in mismatch between the grating vectors of coupling in, turning, and coupling out, which ultimately deteriorates the display effect.

[0003] Furthermore, when the exposure beam enters and exits the interface between the prism, substrate and air, the stray light is cumbersome and difficult to trace, which also leads to an increase in the number of grating derivative orders, a decrease in the diffraction efficiency of a single grating order, and an increase in the grating haze.

[0004] In order to reduce the production difficulty of volume holographic display equipment, a prism-free and matching liquid-free exposure scheme can be adopted. However, the existing prism-free and matching liquid-free exposure scheme can only be applied to reflective grating exposure or exposure with a large double beam angle.

[0005] Therefore, there is an urgent need for an exposure method for a volume holographic display device that can solve one or more of the above problems. Summary of the invention

[0006] In order to solve one or more problems existing in the prior art, the present invention provides an exposure method for a volume holographic display device. The technical solution adopted by the present invention to solve the above problems is: the exposure method comprises: for a reflective grating: the incident light is a vector , the diffracted light is vector , the object light is a vector , the reference light is vector , the grating vector required for exposure is , the holographic grating material has an inherent shrinkage rate of , the shrinkage =( , , ), the adjusted raster vector is , then, ; Step 1: Place the substrate, photosensitive material, and object light vector , reference light vector and the raster vector is The whole body rotates around the Y axis by an angle of α, and then rotates around the X axis γ Angle, so that the rotated raster vector Parallel to the Z axis, the rotated object light vector is obtained , reference light vector ; Step 2: Object Light Vector , reference light vector and raster vector The whole is rotated around the Z axis by an angle of β to obtain the rotated object light vector , reference light vector and raster vector ; Step 3: Object Light Vector , reference light vector Normal to substrate The angles are recorded as the first angle and the second angle respectively, and by adjusting the angle α, the γ The angle β and the angle β make the first angle and the second angle equal to the Brewster's angle or close to the Brewster's angle within the range of ±10°.

[0007] In some embodiments, and The angle between two vectors And it is greater than 90 degrees. When the diffracted light enters the waveguide for transmission, the diffraction angle is greater than the total reflection angle.

[0008] In some embodiments, for a transmission grating: object light and reference light The recorded wavelength of light is recorded as , incident light and diffracted light The wavelength of the reconstructed light is recorded as , the first angle and the second angle are equal. If it is not possible to make the first angle and the second angle equal to the Brewster angle or close to the Brewster angle within ±10°, the recording light wavelength is used. >Reconstructing the wavelength of light The required transmission grating is recorded in a reflective manner and step 1, step 2 and step 3 are performed.

[0009] Furthermore, for the transmission grating: and The angle between two vectors And less than 90 degrees.

[0010] In some embodiments, the object light vector , reference light vector P-polarized light was used as the incident light.

[0011] In some embodiments, the incident light = , diffracted light = ; Then the raster vector ; in, is the refractive index of the holographic grating material, To reconstruct the wavelength of light, is the angle between the incident light and the positive direction of the Z axis, is the angle between the incident light and the positive direction of the X-axis, is the angle between the diffracted light and the positive direction of the Z axis, is the angle between the diffracted light and the positive direction of the X-axis, , , They are the shrinkage rates of the holographic grating material in the X, Y, and Z axes respectively.

[0012] Furthermore, = , reference light = ; in, To record the wavelength of light, is the angle between the object light and the positive direction of the Z axis, is the angle between the object light and the positive direction of the X-axis, is the angle between the reference light and the positive direction of the Z axis, is the angle between the reference light and the positive direction of the X-axis; set up = 0°, that is, the object light is in the XOZ plane and passes through and right , Solve and calculate the object light and reference light .

[0013] Furthermore, the rotation matrix for rotating around the Y axis by an angle α in step 1 is , the rotation around the X axis γ The rotation matrix of the angle is , then , , .

[0014] Furthermore, the rotation matrix of the angle β around the Z axis in step 2 is , then , , .

[0015] The technical effect achieved by the present invention is: the above exposure method realizes dual-beam exposure without prism and matching liquid; compared with the traditional exposure scheme without prism and matching liquid, which can only be applied to reflective grating exposure or exposure with a large dual-beam angle, the exposure method of the present application can be applied to a wider range of dual-beam angles and is applicable to transmission gratings and reflection gratings; Considering the changes in grating vector and period caused by the inherent shrinkage rate of the material after the holographic material is exposed and cured, the exposure method of the present application takes into account the inherent shrinkage rate s and introduces pre-compensation, thereby matching the grating vectors between the coupling-in, turning, and coupling-out, thereby improving the final display effect; Furthermore, during exposure, the exposure method of the present application uses P-polarized light as the double light beam to be incident on the substrate and the material, ultimately achieving the purpose of satisfying the Brewster angle condition, thereby making the exposure light path almost free of stray light, improving the grating diffraction efficiency and grating quality, and greatly improving the final display effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of grating vectors of the reflective grating of the present invention during the reproduction process; Figure 2 A schematic diagram of grating vectors of the reflective grating of the present invention during the exposure process; Figure 3 A schematic diagram of a raster vector of step 1 of the present invention; Figure 4 A schematic diagram of a raster vector of step 2 of the present invention; Figure 5 A schematic diagram of a raster vector of step 3 of the present invention; Figure 6 Schematic diagram of reflected light becoming stray light; Figure 7 is a schematic diagram of embodiment 1 of the present invention; Figure 8 A schematic diagram of grating vectors of the transmission grating of the present invention during the reproduction process; Fig. 9 A schematic diagram of grating vectors of the transmission grating of the present invention during the exposure process; Fig.10 This is a schematic diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more understandable, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from this description, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0018] The present invention discloses an exposure method for a volume holographic display device, the exposure method comprising: for a reflective grating: the incident light is a vector , the diffracted light is vector , the object light is a vector , the reference light is vector ; Combination Figure 1 As shown, the grating vector required for exposure is , the holographic grating material has an inherent shrinkage rate of , the shrinkage =( , , ), the adjusted raster vector is , then, ; and The angle between two vectors And it is greater than 90 degrees, and when the diffracted light enters the waveguide for transmission, the diffraction angle is greater than the total reflection angle; Incident light = , diffracted light = ; Raster Vector ; in, is the refractive index of the holographic grating material, To reconstruct the wavelength of light, is the angle between the incident light and the positive direction of the Z axis, is the angle between the incident light and the positive direction of the X-axis, is the angle between the diffracted light and the positive direction of the Z axis, is the angle between the diffracted light and the positive direction of the X-axis, , , They are the shrinkage rates of the holographic grating material in the three directions of X, Y, and Z axes; Combination Figure 2 As shown, the object light = , reference light = ; in, To record the wavelength of light, is the angle between the object light and the positive direction of the Z axis, is the angle between the object light and the positive direction of the X-axis, is the angle between the reference light and the positive direction of the Z axis, is the angle between the reference light and the positive direction of the X-axis; Depend on You can get: In order to facilitate the setting of the light path in the actual exposure process = 0°, that is, the object light is in the XOZ plane and passes through and right , Solve and calculate the object light and reference light .

[0019] Combination Figure 3 As shown, step 1: place the substrate, photosensitive material, and object light vector , reference light vector and the raster vector is The whole body rotates around the Y axis by an angle of α, and then rotates around the X axis γ Angle, so that the rotated raster vector Parallel to the Z axis, the rotated object light vector is obtained , reference light vector ; Then there is a rotation matrix and , can be obtained , , .

[0020] Combination Figure 4 As shown, step 2: transform the object light vector , reference light vector and raster vector The whole is rotated around the Z axis by an angle of β to obtain the rotated object light vector , reference light vector and raster vector ; Then there is a rotation matrix , can be obtained , , .

[0021] Combination Figure 5 As shown, step 3: object light vector , reference light vector Normal to substrate The angles are recorded as the first angle and the second angle respectively, and by adjusting the angle α, the γ Angle β and the angle β make the first angle and the second angle equal to Brewster's angle or close to Brewster's angle within a range of ±10°; Among them, the first angle is , the second angle is .

[0022] Hewuguang When P polarized light is incident on the substrate and material, = When the angle is equal to the Brewster angle, since both double beams have no S light component, there is no reflected light at the interface between the air and the substrate, so that there is almost no stray light in the exposure light path, which can improve the grating diffraction efficiency and grating quality, and greatly improve the final display effect, that is: ,in is the Brewster angle from air to substrate, is the refractive index of the substrate; if = Strictly equal to the Brewster angle, the appropriate rotation angle should be selected , γ and Make them as close as possible to Brewster's angle, that is , Within the range of ±10° of the Brewster angle (including 10°), the reflected light at the interface between the air and the substrate is weakened, thereby reducing stray light in the exposure light path.

[0023] Under the premise of ensuring that the light meets the total reflection condition when transmitting in the waveguide, dual-beam exposure without prism and matching liquid is achieved by 3D rotating the substrate and grating vector.

[0024] Combination Figure 6 As shown, the protective cover and the substrate are made of the same refractive index material. When the object light enters the substrate and passes through the grating material, the reflectivity is very low due to the small difference in refractive index between the grating material and the substrate, resulting in less stray light. However, the refractive index difference between the protective cover and the air is large, resulting in a very large energy of the reflected light at the interface 1. After the reflected light enters the grating material layer, it becomes stray light, resulting in poor quality of the formed grating.

[0025] In the exposure method of the application, when the object light is incident with P polarization and the interface with the air satisfies the Brewster angle, since there is no S light component, the energy of the reflected light at interface 1 is close to 0, so that there is almost no stray light in the exposure light path, thereby improving the grating diffraction efficiency and grating quality, and greatly improving the final display effect.

[0026] Example 1: Refractive index of holographic grating material =1.6, reconstructing the wavelength of light um, the angle between the incident light and the positive direction of the Z axis , the angle between the incident light and the positive direction of the X-axis , the angle between the diffracted light and the positive direction of the Z axis , the angle between the diffracted light and the positive direction of the X-axis , recording the wavelength of light , the refractive index of the substrate =1.71, the holographic grating material has an inherent shrinkage rate s=[0.005,0.005, 0.005], then: ; Combination Figure 7 As shown, adjust the rotation angle =17.5°, , ,but ; at this time Hewuguang When P polarized light is incident on the substrate and material, = and is equal to the Brewster angle Since both light beams have no S light component, there is no reflected light at the interface between the air and the substrate, so there is almost no stray light in the exposure light path, which can improve the grating diffraction efficiency and grating quality, and greatly improve the final display effect.

[0027] Specifically, combined Figure 8 , Fig. 9 As shown, for a transmission grating: object light and reference light The recorded wavelength of light is recorded as , incident light and diffracted light The wavelength of the reconstructed light is recorded as , and The angle between two vectors and less than 90 degrees, the first angle and the second angle are equal, if the first angle and the second angle cannot be equal to the Brewster angle or close to the Brewster angle within ±10°, the recording light wavelength is used >Reconstructing the wavelength of light The required transmission grating is recorded in a reflective manner and step 1, step 2 and step 3 are performed.

[0028] Embodiment 2, combined Fig.10 As shown, the refractive index of the holographic grating material is =1.5, reconstruct the wavelength of light um, the angle between the incident light and the positive direction of the Z axis , the angle between the incident light and the positive direction of the X-axis , the angle between the diffracted light and the positive direction of the Z axis , the angle between the diffracted light and the positive direction of the X-axis At 90°, record the wavelength of light , the refractive index of the substrate =1.65, the holographic grating material has an inherent shrinkage rate s=[0.005, 0.005,0.005], then: ; Adjust the rotation angle = 14.24°, , , ; at this time Hewuguang When P polarized light is incident on the substrate and material, = and is equal to the Brewster angle Since both light beams have no S light component, there is no reflected light at the interface between the air and the substrate, so there is almost no stray light in the exposure light path, which can improve the grating diffraction efficiency and grating quality, and greatly improve the final display effect.

[0029] In summary, the above exposure method realizes dual-beam exposure without prism and matching liquid. Compared with the traditional exposure scheme without prism and matching liquid, which can only be applied to reflective grating exposure or exposure with a large dual-beam angle, the exposure method of the present application can be applied to a wider range of dual-beam angles and is applicable to transmissive gratings and reflective gratings. Considering the changes in grating vector and period caused by the inherent shrinkage rate of the material after the holographic material is exposed and cured, the exposure method of the present application takes into account the inherent shrinkage rate s and introduces pre-compensation, thereby matching the grating vectors between the coupling-in, turning, and coupling-out, thereby improving the final display effect; Furthermore, during exposure, the exposure method of the present application uses P-polarized light as the double light beam to be incident on the substrate and the material, ultimately achieving the purpose of satisfying the Brewster angle condition, thereby making the exposure light path almost free of stray light, improving the grating diffraction efficiency and grating quality, and greatly improving the final display effect.

[0030] The above-described embodiments only express one or more implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. An exposure method for a volume holographic display device, characterized in that: The exposure method comprises: for a reflective grating: the incident light is a vector , the diffracted light is vector , the object light is a vector , the reference light is vector , the grating vector required for exposure is , the holographic grating material has an inherent shrinkage rate of , the shrinkage =( , , ), the adjusted raster vector is , then, ; Step 1: Place the substrate, photosensitive material, and object light vector , reference light vector and the raster vector is The whole body rotates around the Y axis by an angle of α, and then rotates around the X axis c Angle, so that the rotated raster vector Parallel to the Z axis, the rotated object light vector is obtained , reference light vector ; Step 2: Object Light Vector , reference light vector and raster vector The whole is rotated around the Z axis by an angle of β to obtain the rotated object light vector , reference light vector and raster vector ; Step 3: Object Light Vector , reference light vector Normal to substrate The angles are recorded as the first angle and the second angle respectively, and by adjusting the angle α, the c The angle β and the angle β make the first angle and the second angle equal to the Brewster's angle or close to the Brewster's angle within the range of ±10°.

2. The exposure method of the volume holographic display device according to claim 1, characterized in that: and The angle between two vectors And it is greater than 90 degrees. When the diffracted light enters the waveguide for transmission, the diffraction angle is greater than the total reflection angle.

3. The exposure method of the volume holographic display device according to claim 1, characterized in that: For transmission gratings: Object light and reference light The wavelength of recorded light is recorded as , incident light and diffracted light The wavelength of the reconstructed light is recorded as , the first angle and the second angle are equal. If it is not possible to make the first angle and the second angle equal to the Brewster angle or close to the Brewster angle within ±10°, the recording light wavelength is used. >Reconstructing the wavelength of light The required transmission grating is recorded in a reflective manner and step 1, step 2 and step 3 are performed.

4. The exposure method of the volume holographic display device according to claim 3, characterized in that: For transmission gratings: and The angle between two vectors And less than 90 degrees.

5. The exposure method of the volume holographic display device according to claim 1, characterized in that: Object Light Vector , reference light vector P-polarized light was used as the incident light.

6. The exposure method of the volume holographic display device according to claim 1, characterized in that: Incident light = , diffracted light = ; Then the raster vector ; in, is the refractive index of the holographic grating material, To reconstruct the wavelength of light, is the angle between the incident light and the positive direction of the Z axis, is the angle between the incident light and the positive direction of the X-axis, is the angle between the diffracted light and the positive direction of the Z axis, is the angle between the diffracted light and the positive direction of the X-axis, , , They are the shrinkage rates of the holographic grating material in the X, Y, and Z axes respectively.

7. The exposure method of the volume holographic display device according to claim 6, characterized in that: Material Light = , reference light = ; in, To record the wavelength of light, is the angle between the object light and the positive direction of the Z axis, is the angle between the object light and the positive direction of the X-axis, is the angle between the reference light and the positive direction of the Z axis, is the angle between the reference light and the positive direction of the X-axis; set up = 0°, that is, the object light is in the XOZ plane and passes through and right , Solve and calculate the object light and reference light .

8. The exposure method of the volume holographic display device according to claim 7, characterized in that: The rotation matrix of the rotation angle α around the Y axis in step 1 is , the rotation around the X axis c The rotation matrix of the angle is , then , , .

9. The exposure method of the volume holographic display device according to claim 8, characterized in that: The rotation matrix of the angle β around the Z axis in step 2 is: , then , , .

Images