Holographic exposure method for manufacturing optical waveguide, optical waveguide and display device

Abstract

The invention discloses a holographic exposure method for manufacturing an optical waveguide, the optical waveguide and a display device. A coupling-in holographic grating, a folding holographic grating and a coupling-out holographic grating are sequentially arranged on the optical waveguide along an optical path; the holographic exposure method comprises the steps of establishing a space coordinate system according to an optical waveguide; calculating propagation constants of two beams of coherent light coupled into the holographic grating to obtain a first array; calculating a propagation constant of the incident light to obtain a second array; calculating an incident array based on the first array and the second array; calculating a propagation constant of emergent light on the folded holographic grating based on the position coordinates of the folded holographic grating and the coupled-out holographic grating to obtain an emergent array; and dividing the folded holographic grating based on the incident array and the emergent array to obtain N exposure partitions with different exposure angles, N being a positive integer. By partitioning the folded holographic grating and setting different exposure angles, the utilization rate of light energy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of holographic grating preparation, and in particular to a holographic exposure method for manufacturing an optical waveguide, an optical waveguide and a display device. Background Art

[0002] With the promotion of augmented reality (AR) technology, the use of optical waveguide display systems is increasing. In the optical waveguide display system, light is emitted through an optical machine, and the light enters the optical waveguide from the coupling grating, completes one-dimensional pupil expansion at the folded grating, and is coupled out by the coupling grating, thereby achieving AR display effects. The setting of the grating in the optical waveguide structure is crucial. In the existing process of making optical waveguides, exposure processing is required, and two beams of coherent light are emitted by two exposure light sources, and interference exposure is performed on the optical waveguide substrate.

[0003] However, currently, during exposure processing, only the light incident vertically from the center of the field of view of the self-coupled grating, that is, the light incident along the normal direction of the optical waveguide substrate, is considered as the incident light for grating design. In actual use, the incident light also has light incident obliquely toward the optical waveguide, which will also be coupled into the grating and transmitted to the folded grating. However, the incident angle of this part of light is inconsistent with that of the central light, and it will not propagate in the folded grating according to the designed direction and diffraction efficiency, so it will gradually dissipate during the propagation process, causing the loss of light energy and reducing the brightness of the displayed image.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a holographic exposure method, an optical waveguide and a display device for manufacturing an optical waveguide, aiming to solve the problem that the existing optical waveguide only considers vertically incident light during the manufacturing process, so that the diffraction propagation of obliquely incident light cannot be completed, causing light energy damage and affecting the display brightness.

[0006] The technical solution of the present invention is as follows:

[0007] A holographic exposure method for manufacturing an optical waveguide, wherein an in-coupling holographic grating, a folded holographic grating and an out-coupling holographic grating are sequentially arranged along an optical path on the optical waveguide; the exposure method comprises:

[0008] Establishing a spatial coordinate system based on the optical waveguide;

[0009] Calculating the propagation constants of the two coherent light beams coupled into the holographic grating to obtain a first array;

[0010] Selecting a light ray perpendicularly irradiated toward the coupled-in holographic grating and at least one light ray obliquely irradiated toward the coupled-in holographic grating as incident light rays, calculating propagation constants of the incident light rays, and obtaining a second array;

[0011] Calculate an incident array based on the first array and the second array; the incident array is a propagation constant of incident light on the folded holographic grating;

[0012] Calculating the propagation constant of the outgoing light on the folded holographic grating based on the position coordinates of the folded holographic grating and the out-coupled holographic grating to obtain an outgoing array;

[0013] The folded holographic grating is divided based on the incident array and the output array to obtain N exposure partitions with differentiated exposure angles, where N is a positive integer.

[0014] In the holographic exposure method for manufacturing an optical waveguide, the N exposure subareas are arranged along a direction perpendicular to the light incident direction of the folded holographic grating.

[0015] In the holographic exposure method for manufacturing an optical waveguide, the step of establishing a spatial coordinate system based on the optical waveguide specifically includes:

[0016] A space coordinate system is established with the plane where the optical waveguide is located as the XY plane and the normal line perpendicular to the optical waveguide radiating toward the center point of the coupled holographic grating as the Z axis.

[0017] The holographic exposure method for manufacturing an optical waveguide, wherein the propagation constant is used to express the light vector in the spatial coordinate system;

[0018] The propagation constant is (θ, ), wherein θ is the angle between the light and the Z axis of the spatial coordinate system, ranging from 0° to 180°; It is the angle of the vector projected by the light on the XY plane of the spatial coordinate system turning clockwise to the positive direction of the X axis, ranging from -180° to 180°.

[0019] In the holographic exposure method for manufacturing an optical waveguide, the step of calculating the propagation constant of the outgoing light on the folded holographic grating based on the position coordinates of the folded holographic grating and the out-coupling holographic grating to obtain the outgoing array specifically comprises:

[0020] Based on the position coordinates of the folded holographic grating and the out-coupling holographic grating, the corresponding propagation constant when the light incident on the folded holographic grating is turned to the out-coupling holographic grating is calculated to obtain an output array.

[0021] The holographic exposure method for manufacturing an optical waveguide, wherein the folded holographic grating is divided based on the incident array and the output array to obtain N exposure partitions with differentiated exposure angles, and after the step where N is a positive integer, the method further includes:

[0022] The folded holographic grating is divided along the light incident direction to obtain M diffraction partitions, where M is a positive integer.

[0023] The holographic exposure method for manufacturing an optical waveguide, wherein the size of the light spot of the coupled holographic grating directed toward the folded holographic grating is 1-35 mm;

[0024] Along the light incident direction of the folded holographic grating, a diffraction partition is divided every 0.5-1.5 of the spot size;

[0025] And / or, along a direction perpendicular to the incident light on the folded holographic grating, the exposure partition is divided into each 0.5-1.5 of the spot size.

[0026] The holographic exposure method for manufacturing an optical waveguide, wherein the step of dividing the folded holographic grating along the light incident direction to obtain M diffraction partitions, wherein M is a positive integer, specifically comprises:

[0027] Along the light incident direction of the folded holographic grating, the diffraction efficiency of the last diffraction partition is set as the maximum diffraction efficiency of the folded holographic grating; and, except for the last diffraction partition, the diffraction efficiency of each diffraction partition satisfies the following relationship:

[0028]

[0029] Wherein, n is the serial number of the diffraction partition, and n is a natural number greater than 1; η n-1 is the diffraction efficiency of the n-1th partition; η n is the diffraction efficiency of the nth partition.

[0030] The present application also discloses an optical waveguide, which is made by any of the above-described holographic exposure methods for making an optical waveguide; wherein the optical waveguide includes an input holographic grating, a folded holographic grating and an output holographic grating arranged in sequence along an optical path, and the folded holographic grating is provided with a plurality of diffraction partitions along the incident light direction, and a plurality of exposure partitions are provided along a direction perpendicular to the incident light direction.

[0031] The present application also discloses a display device, which includes an optical machine and the optical waveguide as described above, wherein the optical waveguide is manufactured by any of the above-described holographic exposure methods for manufacturing an optical waveguide.

[0032] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0033] The holographic exposure method of the optical waveguide disclosed in the present application is based on the design requirements of the optical path in the optical waveguide, fully considers the propagation of incident light in different directions, selects the light that is vertically incident on the coupled-in holographic grating and the light that is obliquely incident on the coupled-in holographic grating as the incident light; by pre-establishing a spatial coordinate system, the propagation constant of the light incident on the folded grating is calculated as the incident array; then the propagation constant of the light when the folded holographic grating is emitted to the coupled-out grating is calculated as the output array; according to the incident array and the output array, the requirements for the exposure angle of the light at each position on the folded holographic grating can be obtained, so that the folded holographic grating can be accurately partitioned, and different exposure angles are set in different exposure partitions, so that the light incident on the folded holographic grating can be emitted from the folded holographic grating with the best diffraction efficiency and angle, and then can be coupled out from the coupled-out holographic grating, thereby increasing the brightness of the final light output of the optical waveguide structure and reducing the loss of light energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 is a flow chart of a holographic exposure method for manufacturing an optical waveguide in the present invention;

[0036] Figure 2 is a schematic diagram of the structure of the optical waveguide in the present invention;

[0037] Figure 3 A schematic diagram of the optical path of light from the image display screen to the optical waveguide in the present invention;

[0038] Figure 4 It is a schematic diagram of the structure of the folded holographic grating in the present invention.

[0039] Among them, 10, optical waveguide; 11, coupled-in holographic grating; 12, folded holographic grating; 13, coupled-out holographic grating. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] See also Figure 1 and Figure 2 In one embodiment of the present invention application, a holographic exposure method for making an optical waveguide 10 is disclosed, wherein an input holographic grating 11, a folded holographic grating 12, and an output holographic grating 13 are sequentially provided along the optical path on the optical waveguide 10. The optical waveguide 10 made in this embodiment is used on an AR device, and can guide light waves to propagate therein, and is a part of an optoelectronic integrated device. An L-shaped optical path is set in the optical waveguide 10, and an input holographic grating 11 is set at the light entrance to couple in light; a folded holographic grating 12 is set at the corner to perform one-dimensional pupil expansion; and an output holographic grating 13 is set at the light exit to couple out light; thereby completing the propagation of light and completely displaying the image emitted by the optical machine.

[0042] In the manufacture of the optical waveguide 10, the exposure angle of the folded holographic grating 12 needs to be calculated based on the angle of the light incident on the folded holographic grating 12. These light rays are diffracted at a specific angle by the coupled holographic grating 11 and then coupled into the optical waveguide 10. In the existing design, only the incident angle of the light rays vertically incident on the coupled holographic grating 11 when reaching the folded holographic grating 12 is considered. In fact, the light rays incident on the coupled holographic grating 11 include multiple directions. For the light rays obliquely incident on the coupled holographic grating 11, the diffraction angle is different from the angle of the vertical incident light rays, and the angle of the light rays incident on the folded holographic grating 12 after being reflected by the optical waveguide 10 is also different. However, this part of the light rays is not considered when the folded holographic grating 12 is exposed, so that this part of the light rays cannot be transmitted in the optical waveguide 10 without loss at the designed efficiency and direction. The loss during the transmission process reduces the brightness of the image display.

[0043] To this end, the exposure method disclosed in this embodiment includes:

[0044] S100 , establishing a space coordinate system according to the optical waveguide 10 .

[0045] By establishing a coordinate system, the positions of the coupled-in holographic grating 11, the folded holographic grating 12 and the coupled-out holographic grating 13 in the optical waveguide 10, as well as their mutual relationships, can be expressed by coordinates, and the propagation vector of the light can be expressed by propagation constants, thereby conveniently and accurately calculating the optical path, facilitating the division of exposure areas, and improving the accuracy of production design.

[0046] Specifically, as another implementation of this embodiment, step S100 is disclosed to specifically include:

[0047] S110, establishing a space coordinate system with the plane where the optical waveguide 10 is located as the XY plane and the normal line perpendicular to the optical waveguide 10 radiating toward the center point of the coupled holographic grating 11 as the Z axis.

[0048] In the optical waveguide 10 provided in this embodiment, a plurality of gratings are provided. For the convenience of calculation and expression, the plane where the optical waveguide 10 is located is defined as the XY plane. The positive direction of the coordinate is consistent with the advancing direction of the light, and the coordinate expression is simple. Moreover, the center point of the coupled holographic grating 11 is the center point of the light incident, so the normal line of this position is defined as the Z axis, and the center point of the coupled holographic grating 11 is the origin. The light vector perpendicular to this position coincides with the Z axis, and is coupled from the origin position to the optical waveguide 10, and then propagates, which is obviously conducive to simplifying the coordinate calculation and the vector expression of the light path.

[0049] It should be noted that, in this embodiment, only one method for establishing a spatial coordinate system is exemplified, but the protection scope of the present invention is not limited thereto. Other establishment methods, such as changing the origin position, changing the Z-axis direction, etc., as long as the established spatial coordinate system can express the position of the grating on the optical waveguide 10 and the propagation vector of the optical path through coordinates, can achieve the technical effect disclosed in this application. As an equivalent replacement of the concept of the present invention, it should also be within the scope of protection of this application.

[0050] Specifically, the propagation constant disclosed in this embodiment is used to express the light vector in the spatial coordinate system. The propagation constant is (θ, ), wherein θ is the angle between the light and the Z axis of the spatial coordinate system, ranging from 0° to 180°; It is the angle of the vector projected by the light on the XY plane of the spatial coordinate system turning clockwise to the positive direction of the X axis, ranging from -180° to 180°.

[0051] In this embodiment, different incident light rays are selected as objects for description, and the propagation direction of the light rays is accurately located by using the propagation constant, so that the incident angle of the incident light rays can be accurately calculated and described in combination with the coordinates of the folded holographic grating 12 .

[0052] S200, calculating the propagation constants of the two coherent light beams coupled into the holographic grating 11 to obtain a first array.

[0053] The coupled holographic grating 11 disclosed in this embodiment is formed by coupling two coherent light beams during the manufacturing process, so its characteristic of changing the optical path is determined by the propagation constants of the two coherent light beams. The propagation constants of the two coherent light beams are obtained in advance and recorded to facilitate the subsequent calculation of the incident array.

[0054] S300, selecting a light ray perpendicularly irradiated toward the coupled-in holographic grating 11 and at least one light ray obliquely irradiated toward the coupled-in holographic grating 11 as incident light rays, calculating propagation constants of the incident light rays, and obtaining a second array.

[0055] In this embodiment, both the diffraction of the light incident vertically on the coupled holographic grating 11 and the diffraction of the light incident obliquely are taken into account, so at least two beams of light are used as the design basis. The propagation constants when the two beams of light are incident on the coupled holographic grating 11 and propagated to the folded holographic grating 12 are calculated to describe the optical path of the light incident at different angles on the folded holographic grating 12.

[0056] Specifically, in this embodiment, the light rays incident on the coupled holographic grating 11 must include light rays incident vertically toward the optical waveguide 10, so as to set the exposure path of the light rays propagating along the center of the optical path in the optical waveguide 10; at the same time, light rays incident obliquely toward the optical waveguide 10 must also be included to simulate the light rays incident obliquely when displaying an image. In actual situations, the size of the viewing angle of the optical machine screen determines the range of the obliquely incident light rays. On this basis, in this embodiment, the light rays at the edge of the display image can be selected as the basis for exposure design.

[0057] In addition, in this embodiment, by establishing a spatial coordinate system, it is convenient to accurately express the light in combination with the field of view of the displayed image, so as to clarify the vector direction of the incident light to the folded holographic grating 12. In this embodiment, each beam of light has its own propagation constant. If at least two beams of light are selected, at least two groups of propagation constants can be used to express them in the spatial coordinate system. By combining these propagation constants to form a second array, it is convenient to perform subsequent unified calculations and improve calculation efficiency.

[0058] S400, calculating an incident array based on the first array and the second array; the incident array is a propagation constant of the incident light on the folded holographic grating 12.

[0059] When the incident light enters the coupled holographic grating 11, it diffracts, thereby changing the propagation direction. The diffraction angle is determined by the characteristics of the coupled holographic grating 11, and its characteristics depend on the information of the two coherent lights (i.e., the first array) when the coupled grating is prepared. Therefore, the propagation constant of the incident light after diffraction to the folded holographic grating 12, i.e., the incident array, can be accurately calculated by combining the second array and the first array. The calculation process is simple and direct, and the measurement results are accurate, which is conducive to the accurate design of the structure of the folded holographic grating 12.

[0060] S500, calculating the propagation constant of the outgoing light on the folded holographic grating 12 based on the position coordinates of the folded holographic grating 12 and the out-coupling holographic grating 13, and obtaining an outgoing array.

[0061] At the beginning of the design, the position of the folded holographic grating 12 and the position of the coupled holographic grating 13 on the optical waveguide 10 disclosed in this embodiment have been determined. Therefore, the light emitting direction of the folded holographic grating 12 is the direction of the line between the two, which is also determined, so it only needs to be expressed by the propagation constant.

[0062] Specifically, as another implementation of this embodiment, step S500 is disclosed to specifically include:

[0063] S510, based on the position coordinates of the folded holographic grating 12 and the out-coupling holographic grating 13, calculate the corresponding propagation constant when the light incident on the folded holographic grating 12 is turned to be incident on the out-coupling holographic grating 13, and obtain an output array.

[0064] In the spatial coordinate system, once the positions of the folded holographic grating 12 and the out-coupling holographic grating 13 are determined, the angle at which the light needs to be deflected at the folded holographic grating 12 can be determined, so that after the light is emitted from the folded holographic grating 12, it can continue to be totally reflected and propagated to the out-coupling holographic grating 13. By adding the value to the angle at which the light is deflected, we can get the output array.

[0065] S600, dividing the folded holographic grating 12 based on the incident array and the output array to obtain N exposure partitions with differentiated exposure angles, where N is a positive integer.

[0066] Specifically, as another implementation of this embodiment, it is disclosed that the N exposure partitions are arranged along a direction perpendicular to the incident direction of the folded holographic grating 12 .

[0067] Specifically, as another implementation of this embodiment, it is disclosed that the size of the light spot emitted by the coupled holographic grating 11 to the folded holographic grating 12 is 1-35 mm; along the direction perpendicular to the incident light on the folded holographic grating 12, one exposure zone is divided every 0.5-1.5 of the light spot size.

[0068] The optical waveguide 10 disclosed in this embodiment is used on an AR device. Depending on the application scenario and the selected optical machine, the sizes of the light spots emitted by different optical machines are different, usually in the range of 1-35 mm, that is, the cross-sectional width of the light beam transmitted in the optical waveguide 10 is 1-35 mm.

[0069] Specifically, the exposure partition disclosed in this embodiment starts from the center position of the folded holographic grating 12 and is gradually divided into several areas on both sides. The angles at which the light reaches different areas are different, and the exposure angles are different. The exposure angle is calculated according to the actual situation; generally, one exposure partition is divided at a distance of 0.5-1.5 spot sizes. In one exposure partition, the steering angles of the light are close and can be divided into an integral area, in which the exposure angles are the same. Areas with similar exposure angles can be combined and divided into one exposure partition. By setting a suitable number of exposure partitions, it can meet the requirements of partition exposure and adapt to the diffraction of various incident lights; it can also appropriately reduce the process difficulty and avoid too many partitions that lead to difficulty in manufacturing or too high manufacturing costs.

[0070] In particular, the exposure area on the folded holographic grating 12 can be divided into an integer number; the width of the divided area is adjusted according to the spot size of the incident light beam. If the width of the folded holographic grating 12 at the edge position is less than a standard divided area, the size of the folded holographic grating 12 can be appropriately increased.

[0071] For example, if the initial design size of the folded holographic grating 12 is 50 mm and the spot size is 18 mm, there are two ways of division: the first is to divide it into three exposure partitions with widths of 18 mm, 18 mm, and 14 mm respectively; the second is to increase the size of the folded holographic grating 12 to 54 mm and divide it into three exposure partitions, each of which is 18 mm wide.

[0072] In summary, the holographic exposure method of the optical waveguide 10 disclosed in the present embodiment is based on the design requirements of the optical path in the optical waveguide 10. First, the light that is vertically incident on the coupled-in holographic grating 11 and the light that is obliquely incident on the coupled-in holographic grating 11 are selected as the incident light. The propagation constant of the light when reaching the folded holographic grating 12 is calculated to obtain the incident array; then, according to the relative positions of the coupled-out holographic grating 13 and the folded holographic grating 12, the exit array of the light when the folded holographic grating 12 exits toward the coupled-out holographic grating 13 is calculated; finally, the incident array and the exit array are compared to obtain the requirements for the exposure angle of the light at each position on the folded holographic grating 12, so that the folded holographic grating 12 can be accurately partitioned, and different exposure angles are set in different exposure partitions, so that the light incident on the folded holographic grating 12 can be propagated toward the coupled-out holographic grating 13, thereby increasing the brightness of the final light output of the optical waveguide 10 structure and reducing the loss of light energy.

[0073] Specifically, as another implementation of this embodiment, after the step S600 is disclosed, the following further includes:

[0074] S700, dividing the folded holographic grating 12 along the incident light direction to obtain M diffraction partitions, where M is a positive integer.

[0075] In the present embodiment, the diffraction efficiency of the folded holographic grating 12 is designed, and a plurality of diffraction partitions are divided on the folded holographic grating 12. The diffraction efficiency of each diffraction partition is different. The diffraction efficiency of the partition close to the coupled-in holographic grating 11 is low, and the diffraction efficiency of the partition far from the coupled-in holographic grating 11 is high, so that the intensity of the light propagating to the coupled-out holographic grating 13 is uniform, thereby improving the uniformity of the final image.

[0076] Specifically, as another implementation of this embodiment, it is disclosed that the diffraction partition is divided into a diffraction partition every 0.5-1.5 light spot sizes along the incident direction of the folded holographic grating 12. In this embodiment, the diffraction efficiency in each diffraction partition is the same, and the partition is divided according to 0.5-1.5 times the size of the light spot, and the diffraction efficiency of light at different positions is reasonably allocated, so that the overall uniformity of the final displayed image is better.

[0077] Specifically, as another implementation of this embodiment, step S700 is disclosed to specifically include:

[0078] S710, along the light incident direction of the folded holographic grating 12, setting the diffraction efficiency of the last diffraction subarea as the maximum diffraction efficiency of the folded holographic grating 12; and, except for the last diffraction subarea, the diffraction efficiency of each diffraction subarea satisfies the following relationship:

[0079]

[0080] Wherein, n is the serial number of the diffraction partition, and n is a natural number greater than 1; η n-1 is the diffraction efficiency of the n-1th partition; η n is the diffraction efficiency of the nth partition.

[0081] In this embodiment, the diffraction efficiency of each partition is accurately calculated by a formula, thereby improving the design accuracy of the folded holographic grating 12.

[0082] like Figure 3 and Figure 4 As shown, in another implementation of this embodiment, the process of selecting 8 edge rays and the central vertically incident ray as a basis to set the exposure partition and the diffraction partition of the folded holographic grating 12 on the optical waveguide 10 is disclosed as follows:

[0083] (1) The plane where the optical waveguide 10 is located is defined as the XY plane, and the center point of the coupled holographic grating 11 is the center point of the light incident, which is defined as the origin. Therefore, the normal line of this position is defined as the Z axis to construct a spatial coordinate system.

[0084] (2) Acquire the propagation constants of the two beams of related light used when coupling into the holographic grating 11 for exposure, which are (0°, 0°) and (123.5°, -90°) respectively, as the first array.

[0085] (3) According to the initial parameters of the optical machine and the optical waveguide 10, the horizontal field of view angle of the image display screen of the selected optical machine is determined to be 10°, the vertical field of view angle is 3°, and the field of view angle is 10.44°. A total of 8 edge rays and 1 central ray from the center of the screen, the two sides of the horizontal field of view angle, the two sides of the vertical field of view angle, and the four end points of the screen field of view are selected as incident rays, and their propagation constants are used as the second array. The propagation constants of these 9 incident rays are (0°, 0°), (1.5°, 90°), (1.5°, -90°), (5°, 0°), (5°, 180°), (5.22°, 16.7°), (5.22°, -16.7°), (5.22°, 163.3°), (5.22°, -163.3°).

[0086] (4) According to Kogelnik's coupled wave theory, the propagation constants of the nine incident light rays when they are coupled into the holographic grating 11 and incident on the folded holographic grating 12 are calculated, which are (123.5°, -90°), (125.27°, -90°), (121.64°, -90°), (123.29°, -86°), (123.29°, -93°), (125.06°, -85.92°), (121.43°, -86.09°), (125.06°, -94.07°), and (121.43°, -93.9°), and the incident array is obtained.

[0087] (5) The connection direction between the coupling-in holographic grating 11 and the folded holographic grating 12 disclosed in this embodiment is the first connection direction; the connection direction between the folded holographic grating 12 and the coupling-out holographic grating 13 is the second connection direction; the angle between the first connection direction and the second connection direction is 90°, that is, the light is deflected 90° at the folded holographic grating 12, which is the initial parameter set for the optical waveguide 10. On this basis, it can be known that the propagation constants of the 9 light rays emitted from the folded holographic grating 12 are respectively (123.5°, -180°), (125.27°, -180°), (121.64°, -180°), (123.29°, -176°), (123.29°, -183°), (125.06°, -175.92°), (121.43°, -176.09°), (125.06°, -184.07°), (121.43°, -183.9°), and the output array is obtained.

[0088] (6) According to the incident array and the output array, it can be known that the incident light rays with different directions (propagation constants) are incident to the folded holographic grating 12 at different angles (propagation constants) after being diffracted by the coupled holographic grating 11. The value can be used to divide the direction of light incident on the folded holographic grating 12 into three directions of -93.9°, -90°, and -86°. The folded holographic grating 12 is divided into three exposure partitions along the direction of the incident light perpendicular to the folded holographic grating 12. When the three exposure partitions are exposed, the propagation constants of the two coherent light beams are respectively (121.43°, -93.9°) and (121.43°, -183.9°), (123.5°, -90°) and (123.5°, -180°), (123.29°, -86°) and (123.29°, -176°).

[0089] In the above example, three exposure zones are divided, which can take into account the propagation of light in all directions and the exposure process will not be too complicated. The value divides the direction of the light incident on the folded holographic grating 12 into more directions such as -90°, -86°, -93°, -85.92°, -86.09°, -94.07°, and -93.9°, making the control more precise, but the exposure operation is also more complicated.

[0090] (7) Along the direction of light propagation from the coupled holographic grating 11 to the folded holographic grating 12, four diffraction partitions are divided on the folded holographic grating 12. In this embodiment, due to material limitations, the maximum achievable diffraction efficiency of the folded holographic grating 12 is 90%, so the diffraction efficiencies of the four diffraction partitions are 24.4%, 32.2%, 47.4%, and 90%, respectively.

[0091] like Figure 4 As shown, through the holographic exposure method disclosed in this embodiment, the folded holographic grating 12 of the optical waveguide 10 is divided into 3 columns and 4 rows, a total of 12 areas, the exposure angles of the partitions in the same column are the same, and the diffraction efficiency of the partitions in the same row is the same, so that the folded holographic grating 12 can transmit all the incident light to the out-coupling holographic grating 13, increase the utilization rate of light energy, improve the image brightness, and make the brightness of the image uniform everywhere.

[0092] It should be understood that the various parts of the present application can be implemented in hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array, a field programmable gate array, etc.

[0093] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0094] As another embodiment of the present application, an optical waveguide 10 is disclosed, which is made by any of the above-described holographic exposure methods for making the optical waveguide 10; wherein the optical waveguide 10 includes an input holographic grating 11, a folded holographic grating 12 and an output holographic grating 13 arranged in sequence along the optical path, and the folded holographic grating 12 is provided with a plurality of diffraction partitions along the incident light direction, and a plurality of exposure partitions are provided along a direction perpendicular to the incident light direction.

[0095] As another embodiment of the present application, a display device is disclosed, which includes an optical machine and the optical waveguide 10 as described above, and the optical waveguide 10 is manufactured by using any of the above-described holographic exposure methods for manufacturing the optical waveguide 10 .

[0096] In summary, the present application discloses a holographic exposure method for manufacturing an optical waveguide 10, wherein the optical waveguide 10 is provided with an in-coupling holographic grating 11, a folded holographic grating 12 and an out-coupling holographic grating 13 in sequence along an optical path; the exposure method comprises: S100, establishing a spatial coordinate system according to the optical waveguide; S200, calculating the propagation constants of two coherent light beams for preparing the in-coupling holographic grating to obtain a first array; S300, selecting a light beam perpendicular to the in-coupling holographic grating and at least one light beam obliquely directed to the in-coupling holographic grating as incident light beams, and calculating the propagation constants of the two coherent light beams for preparing the in-coupling holographic grating ... The propagation constant of the incident light is calculated to obtain a second array; S400, based on the first array and the second array, an incident array is calculated; the incident array is the propagation constant of the incident light on the folded holographic grating; S500, based on the position coordinates of the folded holographic grating 12 and the outcoupling holographic grating 13, the propagation constant of the outgoing light on the folded holographic grating 12 is calculated to obtain an outgoing array; S600, based on the incident array and the outgoing array, the folded holographic grating 12 is divided to obtain N exposure partitions with different exposure angles, where N is a positive integer. The holographic exposure method of the optical waveguide 10 disclosed in this embodiment is based on the design requirements of the optical path in the optical waveguide 10, fully considers the propagation of incident light in different directions, accurately partitions the folded holographic grating 12, and sets different exposure angles in different exposure partitions, so that the light incident on the folded holographic grating 12 can propagate to the outcoupling holographic grating 13, thereby increasing the brightness of the final light output of the optical waveguide 10 structure and reducing the loss of light energy.

[0097] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0098] It should be noted that the present invention takes the holographic exposure method for manufacturing an optical waveguide as an example to introduce the specific structure and working principle of the present invention, but the application of the present invention is not limited to the holographic exposure method for manufacturing an optical waveguide, and can also be applied to the production and use of other similar workpieces.

[0099] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A holographic exposure method for making an optical waveguide, characterized in that: The optical waveguide is provided with an in-coupling holographic grating, a folded holographic grating and an out-coupling holographic grating in sequence along the optical path; the exposure method comprises: Establishing a spatial coordinate system based on the optical waveguide; Calculating the propagation constants of the two coherent light beams coupled into the holographic grating to obtain a first array; Selecting a light ray perpendicularly irradiated toward the coupled-in holographic grating and at least one light ray obliquely irradiated toward the coupled-in holographic grating as incident light rays, calculating propagation constants of the incident light rays, and obtaining a second array; Calculate an incident array based on the first array and the second array; the incident array is a propagation constant of incident light on the folded holographic grating; Calculating the propagation constant of the outgoing light on the folded holographic grating based on the position coordinates of the folded holographic grating and the out-coupled holographic grating to obtain an outgoing array; The folded holographic grating is divided based on the incident array and the output array to obtain N exposure partitions with differentiated exposure angles, where N is a positive integer.

2. The holographic exposure method for manufacturing an optical waveguide according to claim 1, characterized in that: The N exposure subareas are arranged along a direction perpendicular to the light incident direction of the folded holographic grating.

3. The holographic exposure method for manufacturing an optical waveguide according to claim 1, characterized in that: The step of establishing a spatial coordinate system based on the optical waveguide specifically includes: A space coordinate system is established with the plane where the optical waveguide is located as the XY plane and the normal line perpendicular to the optical waveguide radiating toward the center point of the coupled holographic grating as the Z axis.

4. The holographic exposure method for manufacturing an optical waveguide according to claim 3, characterized in that: The propagation constant is used to express the light vector in the spatial coordinate system; The propagation constant is Wherein, θ is the angle between the light and the Z axis of the spatial coordinate system, ranging from 0° to 180°; It is the angle of the vector projected by the light on the XY plane of the spatial coordinate system turning clockwise to the positive direction of the X axis, ranging from -180° to 180°.

5. The holographic exposure method for manufacturing an optical waveguide according to claim 1, characterized in that: The step of calculating the propagation constant of the outgoing light on the folded holographic grating based on the position coordinates of the folded holographic grating and the out-coupling holographic grating to obtain the outgoing array specifically comprises: Based on the position coordinates of the folded holographic grating and the out-coupling holographic grating, the corresponding propagation constant when the light incident on the folded holographic grating is turned to the out-coupling holographic grating is calculated to obtain an output array.

6. The holographic exposure method for manufacturing an optical waveguide according to claim 1, characterized in that: After the step of dividing the folded holographic grating based on the incident array and the output array to obtain N exposure partitions with differentiated exposure angles, wherein N is a positive integer, the method further includes: The folded holographic grating is divided along the light incident direction to obtain M diffraction partitions, where M is a positive integer.

7. The holographic exposure method for manufacturing an optical waveguide according to claim 6, characterized in that: The size of the light spot of the coupled holographic grating directed toward the folded holographic grating is 1-35 mm; Along the light incident direction of the folded holographic grating, a diffraction partition is divided every 0.5-1.5 of the spot size; And / or, along a direction perpendicular to the incident light on the folded holographic grating, the exposure partition is divided into each 0.5-1.5 of the spot size.

8. The holographic exposure method for manufacturing an optical waveguide according to claim 6, characterized in that: The step of dividing the folded holographic grating along the incident direction of light to obtain M diffraction partitions, wherein M is a positive integer, specifically comprises: Along the light incident direction of the folded holographic grating, the diffraction efficiency of the last diffraction partition is set as the maximum diffraction efficiency of the folded holographic grating; and, except for the last diffraction partition, the diffraction efficiency of each diffraction partition satisfies the following relationship: Wherein, n is the serial number of the diffraction partition, and n is a natural number greater than 1; η n-1 is the diffraction efficiency of the n-1th partition; η n is the diffraction efficiency of the nth partition.

9. An optical waveguide, manufactured by the holographic exposure method for manufacturing an optical waveguide according to any one of claims 1 to 8; characterized in that: The optical waveguide comprises an in-coupling holographic grating, a folded holographic grating and an out-coupling holographic grating which are sequentially arranged along an optical path; the folded holographic grating is provided with a plurality of diffraction partitions along a light incident direction and a plurality of exposure partitions perpendicular to the light incident direction.

10. A display device, characterized in that: The invention comprises an optical machine and the optical waveguide as claimed in claim 9, wherein the optical waveguide is manufactured by the holographic exposure method for manufacturing an optical waveguide as claimed in any one of claims 1 to 8.

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