Grating exposure system
By using mask plate exposure technology of holographic gratings in grating manufacturing, the problems of low stability and efficiency of grating manufacturing in the prior art are solved, and efficient and low-cost large-scale grating manufacturing is achieved.
Patent Information
- Application Number
- CN202510498199.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-21
- Publication Date
- 2025-06-24
AI Technical Summary
In the existing grating manufacturing technology, the dual-beam interference method is susceptible to environmental interference, the diffraction efficiency of the surface relief grating is low and the manufacturing cost is high, making it difficult to achieve large-scale and large-scale manufacturing.
A light source assembly and a mask plate are arranged in sequence along the optical axis. A first body holographic grating and a second body holographic grating are provided on the light-entry side of the mask plate. The light rays are diffracted through these holographic gratings to generate reference light and signal light to achieve stable exposure of the grating.
It realizes the grating exposure system with strong stability, high diffraction efficiency, low production cost, and can be manufactured in large-scale and large-scale.
Smart Images
Figure CN120195937A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of grating manufacturing, and more particularly, to a grating exposure system. Background Art
[0002] Diffractive optical waveguides based on gratings are one of the most promising technical solutions in the AR (Augmented Reality) industry. Among them, the grating is the core optical element in the diffractive optical waveguide. In the manufacturing of gratings, exposure is a key step, and the quality of exposure determines the quality of the periodic structure in the grating. The key point of exposure lies in the ability to form stable and high-contrast interference fringes.
[0003] Currently, there are mainly two common exposure methods in the industry, namely the two-beam interference method and the mask exposure based on surface relief gratings. However, each of these two methods has its own defects. The optical path components of two-beam interference exposure are numerous, and it is extremely vulnerable to environmental changes during exposure, resulting in grating exposure defects and affecting the final optical effect of the grating. When using mask exposure based on surface relief gratings, firstly, the diffraction efficiency is not high, which easily causes loss of incident light energy. And due to the low diffraction efficiency, high-power lasers often need to be used for exposure to meet the exposure amount required by the photosensitive material, which will in turn reduce the lifespan of other optical components in the entire exposure system due to long-term operation under high-power laser conditions. Secondly, when the size of the manufactured grating increases, the exposure area also increases accordingly, and the required mask size also increases. The manufacturing of surface relief gratings relies on semiconductor processing technology, and large-area exposure, etching, and imprinting pose a great challenge to both the process and cost. Summary of the Invention
[0004] The purpose of this application is to provide a grating exposure system, which has strong stability, high diffraction efficiency, low production cost, and can be used for large-size and large-scale manufacturing, aiming at the deficiencies in the above-mentioned existing technologies.
[0005] To achieve the above purpose, the technical solutions adopted in the embodiments of this application are as follows:
[0006] The embodiments of this application provide a grating exposure system, including: a light source component and a mask arranged in sequence along the optical axis. A first volume holographic grating and a second volume holographic grating are provided on the light incident side of the mask. The light source component emits a first incident light to the first volume holographic grating and a second incident light to the second volume holographic grating. The first incident light is diffracted by the first volume holographic grating to convert into a reference light and irradiate on the substrate to be exposed. The second incident light is diffracted by the second volume holographic grating to convert into a signal light and irradiate on the substrate to be exposed.
[0007] Optionally, the mask includes a grating layer and a dielectric layer attached to the light-emitting side of the grating layer. The first volume holographic grating and the second volume holographic grating are both located on the light-incident side of the grating layer. The dielectric layer is used to prevent total internal reflection of light within the mask.
[0008] Optionally, the refractive index of the dielectric layer is equal to that of the grating layer.
[0009] Optionally, the refractive index of the dielectric layer is equal to that of the upper substrate of the substrate to be exposed, and the upper substrate is the substrate close to the dielectric layer.
[0010] Optionally, a bonding layer is provided on the light-emitting side of the dielectric layer. One surface of the bonding layer is attached to the surface of the dielectric layer, and the opposite surface is attached to the surface of the upper substrate. The refractive index of the bonding layer is equal to that of the dielectric layer.
[0011] Optionally, the grating exposure system further includes an absorbing glass, which is used to be attached to the surface of the substrate to be exposed facing away from the mask.
[0012] Optionally, the incident angles of the first incident light and the second incident light are the same.
[0013] Optionally, the first volume holographic grating is the same as the second volume holographic grating.
[0014] Optionally, the light source assembly includes a light source, a filter, a beam expander, and a diaphragm arranged in sequence along the optical axis. The light emitted by the light source is filtered by the filter to remove high-order stray light, and then converted into parallel and collimated expanded light by the beam expander. The expanded light is divided into the first incident light and the second incident light after passing through the diaphragm.
[0015] Optionally, the light source assembly further includes an attenuation sheet located between the diaphragm and the mask, and the attenuation sheet is used to adjust the light intensity difference between the first incident light and the second incident light.
[0016] The beneficial effects of this application include:
[0017] This application provides a grating exposure system, including: a light source assembly arranged in sequence along the optical axis
[0018] and a mask. The light-incident side of the mask is provided with a first volume holographic grating and a second volume holographic grating. The light source assembly emits the first incident light to the first volume holographic grating and the second incident light to the second volume holographic grating. The first incident light is diffracted by the first volume holographic grating to convert into reference light and irradiate on the substrate to be exposed, and the second incident light is diffracted by the second volume holographic grating to convert into signal light and irradiate on the substrate to be exposed. This grating exposure system is provided with the first volume holographic grating and the second volume holographic grating on the mask, and uses the first volume holographic grating and the second volume holographic grating to diffract and expose light. The mask exposure based on the volume holographic grating has strong stability, high diffraction efficiency, and can be manufactured at low cost, in large sizes, and in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.
[0020] Figure 1 It is a schematic diagram of the exposure principle of a volume holographic grating;
[0021] Figure 2 It is a schematic structural diagram of the grating exposure system provided by the embodiment of the present application;
[0022] Figure 3 It is a schematic partial structural diagram of the grating exposure system provided by the embodiment of the present application.
[0023] Reference numerals: 10 - grating exposure system; 11 - light source assembly; 111 - light source; 112 - filter; 113 - beam expander; 114 - aperture; 115 - attenuation sheet; 12 - mask plate; 121 - first volume holographic grating; 122 - second volume holographic grating; 123 - grating layer; 124 - dielectric layer; 13 - light-absorbing glass; 31 - first incident light; 32 - second incident light; 20 - substrate to be exposed; 21 - upper substrate; 22 - lower substrate; 23 - photosensitive material; K R - reference light; K S - signal light. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. The components of the embodiments of the present application described and illustrated in the drawings here can be arranged and designed in various different configurations.
[0025] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application to be protected, but merely represents the selected embodiments of the present application. It should be noted that, without conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the protection scope of the present application.
[0026] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.
[0027] In the description of this application, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this application is usually placed when in use. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to this application. In addition, terms such as "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.
[0028] In the description of this application, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "linked" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0029] One of the core processes in grating manufacturing is exposure. By double-beam interference, light and dark interference fringes are generated and irradiated on the surface of the photosensitive material. Through light intensity induction, a periodic distribution of refractive index is generated inside the photosensitive material. In the manufacture of holographic gratings, these two beams of light are respectively called the reference light and the signal light, and are usually represented by vectors K R and K S . The period of the exposed holographic grating is related to the wavelength of the incident light, the incident angle θ R of the reference light, and the incident angle θ S of the signal light. The relationship between the grating period and each parameter is as follows:
[0030]
[0031] where Λ is the grating period, λ is the wavelength of the incident light, and n is the refractive index of the spatial medium.
[0032] The principle of grating exposure is as Figure 1 shown. Usually, the target period of the grating to be manufactured is known, the wavelength of the incident light is determined by the laser, and the exposure environment is usually in air. Therefore, the refractive index of the spatial medium takes the refractive index of air. It can be found from this that there are multiple solutions for the incident angle θ R of the reference light and the incident angle θ S of the signal light. The appropriate incident angle can be selected for exposure according to the actual usage conditions.
[0033] Please refer to Figure 2, the grating exposure system 10 provided by the embodiments of the present application is used to provide a reference light K for the grating to be manufactured R and a signal light K S , and make them irradiate on the substrate 20 to be exposed, so as to form the grating to be manufactured on the substrate 20 to be exposed.
[0034] Specifically, the grating exposure system 10 includes: a light source assembly 11 and a mask 12 arranged in sequence along the optical axis. A first volume holographic grating 121 and a second volume holographic grating 122 are provided on the light incident side of the mask 12, and the light outgoing side faces the substrate 20 to be exposed. The light source assembly 11 emits a first incident light 31 to the first volume holographic grating 121 and a second incident light 32 to the second volume holographic grating 122. The first incident light 31 is diffracted by the first volume holographic grating 121 to convert into a reference light K R and irradiate on the substrate 20 to be exposed. The second incident light 32 is diffracted by the second volume holographic grating 122 to convert into a signal light K S and irradiate on the substrate 20 to be exposed.
[0035] After the first incident light 31 passes through the first volume holographic grating 121 on the mask 12, diffraction occurs, and its diffraction angle is the incident angle of the reference light K required for the grating to be manufactured R , so that after the first incident light 31 passes through the first volume holographic grating 121, the reference light K required for the grating to be manufactured can be converted R . After the second incident light 32 passes through the second volume holographic grating 122 on the mask 12, diffraction occurs, and its diffraction angle is the incident angle of the signal light K required for the grating to be manufactured S , so that after the second incident light 32 passes through the second volume holographic grating 122, the signal light K required for the grating to be manufactured can be converted S . After the reference light K R and the signal light K S are superimposed, interference fringes will be formed on the substrate 20 to be exposed, and the exposure of the grating will be completed.
[0036] It can be understood that the parameters of the first volume holographic grating 121 and the second volume holographic grating 122 need to be determined according to the target period of the grating to be manufactured. The parameters of the first volume holographic grating 121 and the second volume holographic grating 122 can be the same or different. Preferably, the first volume holographic grating 121 is the same as the second volume holographic grating 122, that is, all parameters are the same, so as to simplify the structure of the mask 12 and facilitate the manufacture of the mask 12.
[0037] In addition to the required reference light K, other lights will also be formed after the first incident light 31 is diffracted by the first volume holographic grating 121 R , and in addition to the required signal light K, other lights will also be formed after the second incident light 32 is diffracted by the second volume holographic grating 122 SOther light, other than this, is not used to manufacture the grating. The surface of the substrate 20 to be exposed can be locally shielded to avoid its influence on the exposure.
[0038] The incident angle of the first incident light 31 and the incident angle of the second incident light 32 can be the same or different. Preferably, the incident angle of the first incident light 31 is the same as the incident angle of the second incident light 32. Further, both the first incident light 31 and the second incident light 32 are perpendicularly incident on the mask plate 12.
[0039] The above grating exposure system 10 is provided with a first volume holographic grating 121 and a second volume holographic grating 122 on the mask plate 12. The first volume holographic grating 121 and the second volume holographic grating 122 are used to diffract and expose light. The mask plate 12 based on the volume holographic grating has strong exposure stability, high diffraction efficiency, and can be manufactured at low cost, in large sizes, and in large quantities.
[0040] Optionally, please refer to Figure 2 and Figure 3 , the mask plate 12 includes a grating layer 123 and a dielectric layer 124 attached to the light-emitting side of the grating layer 123. Both the first volume holographic grating 121 and the second volume holographic grating 122 are located on the light-incident side of the grating layer 123. The dielectric layer 124 is used to prevent total internal reflection of light in the mask plate 12.
[0041] In many actual application processes, for example, when manufacturing the holographic grating in the holographic diffraction optical waveguide, the diffraction angle (corresponding to θ S ) of the required mask plate 12 is often greater than the total internal reflection angle of the waveguide medium, which will cause the signal light K S to be unable to exit from the mask plate 12. Therefore, the mask plate 12 of the embodiment of the present application includes a grating layer 123 and a dielectric layer 124, and the dielectric layer 124 is used to reduce the total internal reflection of light in the mask plate 12, so that the light can smoothly leave the mask plate 12.
[0042] The principle of the dielectric layer 124 to avoid total internal reflection is as follows. According to the total internal reflection angle formula:
[0043] sinC = n2 / n1
[0044] where C is the critical angle of total internal reflection, n1 is the refractive index of the incident medium, and n2 is the refractive index of the exit medium. In this embodiment, the incident medium is the grating layer 123, and the exit medium is the dielectric layer 124.
[0045] It can be seen from the formula that by selecting an appropriate refractive index of the dielectric layer 124, n2 is close to n1, and then the critical angle of total internal reflection C is close to 90 degrees, so total internal reflection is not likely to occur.
[0046] Optionally, the refractive index of the dielectric layer 124 is equal to the refractive index of the grating layer 123.
[0047] With such a setting, it is possible to avoid the refraction and deflection of the reference light K R and the signal light K S when entering the dielectric layer 124, and it is also possible to avoid total reflection.
[0048] Of course, the refractive index of the dielectric layer 124 may also not be equal to that of the grating layer 123. At this time, according to the law of refraction, the light will have a certain angular deflection after entering the dielectric layer 124 from the grating layer 123.
[0049] As Figure 3 shown, the photosensitive material 23 is protected and supported by the upper substrate 21 and the lower substrate 22. Therefore, the substrate 20 to be exposed includes the upper substrate 21, the lower substrate 22, and the photosensitive material 23 located between the upper substrate 21 and the lower substrate 22. During exposure, the upper substrate 21 faces the dielectric layer 124 of the mask 12, and the light emitted from the mask 12 needs to penetrate the upper substrate 21 before irradiating on the photosensitive material 23.
[0050] To avoid the deflection of light when penetrating the upper substrate 21, optionally, the refractive index of the dielectric layer 124 is equal to that of the upper substrate 21 of the substrate 20 to be exposed. In this way, the conversion of the light deflection angle can be reduced, and the design of the mask 12 can be simplified.
[0051] Optionally, a bonding layer is provided on the light-emitting side of the dielectric layer 124. One surface of the bonding layer is attached to the surface of the dielectric layer 124, and the other opposite surface is attached to the surface of the upper substrate 21. The refractive index of the bonding layer is equal to that of the dielectric layer 124.
[0052] With such a setting, the light emitted from the mask 12 can reach the upper substrate 21 along a straight line, avoiding angular deflection, thereby simplifying the design of the mask 12.
[0053] Optionally, the grating exposure system 10 further includes a light-absorbing glass 13, and the light-absorbing glass 13 is used to be attached to the surface of the substrate 20 to be exposed facing away from the mask 12.
[0054] The light-absorbing glass 13 can avoid the light from returning to the photosensitive material 23 to form stray light by absorbing the light of the lower substrate 22 of the substrate 20 to be exposed, thereby reducing the interference to the exposure.
[0055] Optionally, please refer to Figure 2, the light source assembly 11 includes a light source 111, a filter 112, a beam expander 113, and a diaphragm 114 arranged in sequence along the optical axis. The light emitted by the light source 111 is filtered by the filter 112 to remove high-order stray light, and then is converted into collimated and expanded light by the beam expander 113. The expanded light is divided into a first incident light 31 and a second incident light 32 after passing through the diaphragm 114.
[0056] The light source 111 (such as a laser) emits light with a fixed wavelength and irradiates it into the filter 112. The filter 112 is composed of a microscope objective lens and a pinhole, and is used to filter out high-order stray light at the edge of the light spot. The light emitted from the filter 112 passes through a beam expander 113 again. The beam expander 113 is a curved lens or a mirror with collimating and expanding functions, such as a Fourier lens or an off-axis concave mirror. If the beam expander 113 uses a mirror (off-axis concave mirror), Figure 2 the optical path in it will turn in the corresponding direction. The light after passing through the beam expander 113 will become collimated parallel light, and the radius of the light is determined by the aperture of the beam expander 113 used. Behind the beam expander 113 is a diaphragm 114, whose function is to divide the expanded light into two beams of light, namely the first incident light 31 and the second incident light 32, and their sizes and positions respectively correspond to two volume holographic gratings on the mask 12.
[0057] Optionally, the light source assembly 11 further includes an attenuation sheet 115 located between the diaphragm 114 and the mask 12, and the attenuation sheet 115 is used to adjust the light intensity difference between the first incident light 31 and the second incident light 32.
[0058] There is also an attenuation sheet 115 behind the diaphragm 114. Place it in the light path with higher energy to control the light intensities of the two beams of light to the closest state, which will help improve the contrast of the interference fringes and thus improve the exposure quality of the grating.
[0059] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A grating exposure system, characterized in that: include: A light source assembly and a mask are sequentially arranged along the optical axis, wherein a first volume holographic grating and a second volume holographic grating are arranged on the light incident side of the mask, and the light source assembly emits a first incident light to the first volume holographic grating and emits a second incident light to the second volume holographic grating; The first incident light is diffracted by the first volume holographic grating and converted into reference light, which is irradiated onto the substrate to be exposed. The second incident light is diffracted by the second volume holographic grating and converted into signal light, which is irradiated onto the substrate to be exposed.
2. The grating exposure system according to claim 1, characterized in that: The mask includes a grating layer and a dielectric layer bonded to the light-emitting side of the grating layer. The first volume holographic grating and the second volume holographic grating are both located on the light-incoming side of the grating layer. The dielectric layer is used to prevent total reflection of light in the mask.
3. The grating exposure system according to claim 2, characterized in that: The refractive index of the medium layer is equal to the refractive index of the grating layer.
4. The grating exposure system according to claim 2, characterized in that: The refractive index of the dielectric layer is equal to the refractive index of the upper substrate of the substrate to be exposed, and the upper substrate is a substrate close to the dielectric layer.
5. The grating exposure system according to claim 4, characterized in that: A bonding layer is provided on the light-emitting side of the dielectric layer, one surface of the bonding layer is bonded to the surface of the dielectric layer, and the other opposite surface is bonded to the surface of the upper substrate, and the refractive index of the bonding layer is equal to the refractive index of the dielectric layer.
6. The grating exposure system according to claim 1, characterized in that: It also includes light-absorbing glass, which is used to adhere to the surface of the substrate to be exposed away from the mask.
7. The grating exposure system according to claim 1, characterized in that: The first incident light and the second incident light have the same incident angle.
8. The grating exposure system according to claim 1, characterized in that: The first volume holographic grating is identical to the second volume holographic grating.
9. The grating exposure system according to claim 1, characterized in that: The light source assembly includes a light source, a filter, a collimator and an aperture arranged in sequence along the optical axis. The light emitted by the light source is filtered by the filter for high-order stray light, and then converted into parallel collimated expanded light by the collimator. The expanded light is divided into the first incident light and the second incident light after passing through the aperture.
10. The grating exposure system according to claim 9, characterized in that: The light source assembly further includes an attenuation plate located between the aperture and the mask, and the attenuation plate is used to adjust the light intensity difference between the first incident light and the second incident light.