Augmented reality waveguide structure and manufacturing device thereof

Abstract

According to the augmented reality waveguide structure and the manufacturing device thereof disclosed by the invention, the grating vector distribution is estimated by sampling the position of an eye movement range effective area of a plurality of sub-view fields and the grating vector of a light matching Bragg diffraction condition, and the diffraction of invalid light which finally enters out of the eye movement range is not considered; most of effective light rays with different incident angles have high diffraction efficiency on the volume holographic grating, so that the overall brightness uniformity of output light beams is ensured, and the expansion of the view field range is realized. On the basis, the grating vector of each sub-view field light accurately matched with the Bragg diffraction condition is arranged at the coupling tail end of the effective area of the eye movement range, so that the diffraction efficiency is maximized at the coupling tail end as far as possible, the brightness uniformity of effective light output from different positions of the volume holographic grating by each sub-view field is improved, and the brightness uniformity of the volume holographic grating is improved. Therefore, the uniformity of the field of view and the uniformity of the eye movement range are improved.

Description

Technical Field

[0001] The present invention belongs to the field of augmented reality waveguide display technology, and specifically relates to an augmented reality waveguide structure and a manufacturing device thereof. Background Art

[0002] Optical waveguide display technology is the mainstream solution for achieving highly transparent and lightweight augmented reality glasses. It also has great potential in expanding the field of view and further improving the display effect. Light is transmitted in a transparent optical waveguide by total reflection. At the same time, coupling elements such as gratings are arranged in the optical waveguide to control light input, output, steering, pupil expansion, energy distribution, etc., thereby guiding the image light signal into the human eye. As a Bragg diffraction element, the diffraction energy of the volume holographic grating is mostly concentrated in the zeroth and first order diffraction. The ratio of the two can be adjusted by adjusting the grating parameters. Therefore, the optical waveguide with the volume holographic grating as a coupling element has special advantages in improving light efficiency and reducing light leakage.

[0003] The field of view and eye movement range of the optical waveguide display are important indicators for evaluating the performance of the optical waveguide. In order to expand the field of view and eye movement range and improve the uniformity of the field of view and eye movement range, it is necessary to locally adjust the variable grating parameters in space. Compared with the surface microstructure grating, the structure of the volume holographic grating is relatively simple, and the variable parameters that can be adjusted are thickness, refractive index modulation and grating vector.

[0004] In the augmented reality waveguide display, the eye movement range is the range within which the human eye can move to see the complete field of view image. Outside the eye movement range, the human eye can only see part of the field of view image. Taking the two-dimensional pupil expansion waveguide as an example, the waveguide structure includes two layers of transparent glass substrates, and volume holographic gratings arranged between the two layers of substrates as coupling-in gratings, turning gratings, and coupling-out gratings. For a beam of light at a specific input angle, it enters the waveguide for total reflection transmission at the specific input angle from the micro-projection optical machine through the coupling of the coupling-in grating, and is expanded in two directions through the turning grating. Finally, it is coupled through the coupling of the coupling-out grating and output from the waveguide at an angle corresponding to the input angle. Only a part of it enters the eye movement range and is finally received by the human eye to form an image, such as Figure 1 As shown in the figure, the area covered by the light entering the eye movement range on the volume holographic grating is tentatively defined as the effective area of ​​the eye movement range for the light at the specific input angle on the volume holographic grating. Since the angles of light with different input angles entering the eye movement range from the waveguide through the outcoupling grating are also different, the effective areas of the eye movement range for light with different input angles on the volume holographic grating are different. The effective areas of the eye movement range for light with multiple input angles on the volume holographic grating are shown in Figure 1. Figure 2As shown in the figure, light with different input angles often overlaps with each other in the effective eye movement range area on the volume holographic grating. In addition, the grating vectors of the Bragg diffraction conditions matched by light with different input angles are different. The grating vectors at different positions on the volume holographic grating need to support the diffraction of light with many different input angles, so the grating vector distribution cannot be directly obtained. Single parameter control, such as only the refractive index modulation or thickness control, is not conducive to high-degree-of-freedom control of light transmission, and thus cannot achieve a larger field of view, field of view uniformity, and eye movement range uniformity of the optical waveguide display.

[0005] Moreover, it is difficult to prepare volume holographic gratings with these spatially varying parameters, especially the regulation of the grating vector. The requirement of the basic principle of waveguide display that the surface component of the grating vector should remain constant must be met. At the same time, the grating vector variation range must be able to support the light at all angles within the field of view to match the Bragg diffraction conditions as much as possible. Therefore, regardless of whether dual-beam exposure or mask exposure is used, the requirements for the exposure device and exposure process are very stringent. Utility Model Content

[0006] The present invention aims to overcome at least one defect in the prior art and provide an augmented reality waveguide structure, wherein the volume holographic grating has a large angular bandwidth, which helps to expand the field of view of the optical waveguide and improve the uniformity of the field of view and the uniformity of the eye movement range.

[0007] In order to solve the above technical problems, the following technical solutions are adopted:

[0008] In the first aspect, a method for formulating a grating vector distribution target is proposed. The method comprises the following steps:

[0009] Sampling multiple sub-fields of view;

[0010] Record the position of the effective area of ​​the eye movement range of each sub-field of view, and calculate the grating vector of the light of each sub-field of view matching the Bragg diffraction condition;

[0011] According to the positions of the effective areas of the eye movement range of the multiple sub-fields of view and the grating vectors of the multiple sub-fields of view that match the Bragg diffraction conditions, the grating vector distribution of the volume holographic grating is estimated;

[0012] The grating vector distribution of the volume holographic grating is determined based on the estimated grating vector distribution and the principle that the grating vector at the coupling end of the effective area of ​​the eye movement range of each sub-field of view accurately matches the Bragg diffraction condition.

[0013] This scheme estimates the grating vector distribution by sampling the positions of the effective areas of the eye movement range of multiple sub-fields and the grating vectors whose rays match the Bragg diffraction conditions, without considering the diffraction of invalid rays that eventually enter outside the eye movement range, so that most of the effective rays with different incident angles have high diffraction efficiency on the volume holographic grating, so as to ensure the overall brightness uniformity of the output beam and achieve the expansion of the field of view. On this basis, the grating vectors of each sub-field of view that accurately match the Bragg diffraction conditions are placed at the coupling end of its effective area of ​​the eye movement range, so that the diffraction efficiency can be maximized at the coupling end as much as possible, which helps to improve the brightness uniformity of the effective rays output from different positions of the volume holographic grating in each sub-field of view, thereby improving the uniformity of the field of view and the uniformity of the eye movement range.

[0014] In the second aspect, a volume holographic grating is proposed. The grating vector distribution of the volume holographic grating is estimated by sampling the positions of the effective areas of the eye movement range of multiple sub-fields of view and the grating vectors of their light matching the Bragg diffraction conditions, and the grating vectors of the coupling ends of the effective areas of the eye movement range of each sub-field of view accurately match the Bragg diffraction conditions. Among them, the grating vector distribution has at least one change direction, and at least one change direction is the same as the direction of the grating vector surface component, and the surface components of the grating vectors at different positions remain constant; the sub-field of view refers to the set of light rays with the same incident angle that eventually enter the entire field of view; the effective area of ​​the eye movement range refers to the area covered by the light rays that eventually enter the eye movement range on the volume holographic grating.

[0015] The grating vector distribution of this scheme is estimated by sampling the positions of the effective areas of the eye movement range of multiple sub-fields and the grating vectors of their rays matching the Bragg diffraction conditions. The diffraction of invalid rays that eventually enter outside the eye movement range is not considered, so that most of the effective rays with different incident angles have high diffraction efficiency on the volume holographic grating to ensure the overall brightness uniformity of the output beam and achieve the expansion of the field of view. On this basis, the grating vector of each sub-field of view that accurately matches the Bragg diffraction conditions is placed at the coupling end of its effective area of ​​the eye movement range, so that the diffraction efficiency can be maximized at the coupling end as much as possible, which helps to improve the brightness uniformity of the effective rays output from different positions of the volume holographic grating in each sub-field of view, thereby improving the uniformity of the field of view and the uniformity of the eye movement range.

[0016] Preferably, the volume holographic grating and its grating vector distribution include a plurality of discrete grating units, and the plurality of grating units are arranged at least along the direction of the surface component of their grating vectors. The grating vectors at different positions of the same grating unit remain constant, which can avoid the use of a high-precision exposure device in combination with a customized beam shaping element or a customized mask grating production, thereby reducing the production difficulty and cost.

[0017] In a third aspect, an augmented reality waveguide structure using the above-mentioned volume holographic grating is proposed. The augmented reality waveguide structure includes two layers of transparent substrates, and a first volume holographic grating (i.e., the above-mentioned volume holographic grating) disposed between the two layers of substrates. The first volume holographic grating may be an in-coupling grating, an out-coupling grating, a turning grating, or a combination of any two or three of the in-coupling grating, the turning grating, and the out-coupling grating, i.e., the first volume holographic grating may include an in-coupling region, a turning region, and / or an out-coupling region. Preferably, the first volume holographic grating includes an in-coupling region and an out-coupling region. More preferably, the first volume holographic grating includes an in-coupling region, a turning region, and an out-coupling region.

[0018] This solution adopts the volume holographic grating proposed in this case as the coupling-in grating, the turning grating and / or the coupling-out grating, so that the field of view is expanded and the uniformity of the field of view and the uniformity of the eye movement range are improved.

[0019] In a fourth aspect, a method for manufacturing the above-mentioned augmented reality waveguide structure is proposed. The method comprises the following steps:

[0020] Discretizing the grating vector distribution into a plurality of grating units arranged at least along the direction of the grating vector surface component thereof, wherein the grating vectors at different positions of the same grating unit remain constant;

[0021] Select or make a mask grating whose surface period is equal to the surface period of the volume holographic grating to be made, so that the surface component of the grating vector of the volume holographic grating to be made is parallel to the surface component of the grating vector of the mask grating;

[0022] Calculating the incident angle of the collimated light beam corresponding to each grating unit according to the grating vector of the grating unit and the grating vector of the mask grating;

[0023] At the same time, the exposure position and incident angle of the collimated light beam corresponding to a certain grating unit are switched to make the zero-order light and the first-order light generated by the diffraction of the collimated light beam through the mask grating interfere with the augmented reality waveguide structure to be manufactured, and each grating unit is exposed in turn.

[0024] This solution discretizes the volume holographic grating to be produced and its grating vector distribution into multiple grating units with specific grating vectors, which can avoid the use of high-precision exposure devices with customized beam shaping elements or customized mask gratings, reducing the difficulty and cost of production. At the same time, the zero-order light and the first-order light used to sequentially expose each grating unit are generated by diffracting the collimated light beam by the mask grating. The incident angle of the collimated light beam can be adjusted to adjust the incident angle of the zero-order light and the first-order light at the same time, which is less complex and cost-controllable than other methods.

[0025] In a fifth aspect, a device for manufacturing the above-mentioned augmented reality waveguide structure is proposed. The device includes a collimated light generating mechanism, a mask grating and a light-transmitting carrier arranged in sequence, and also includes a first switching mechanism and a second switching mechanism that act simultaneously. The light-transmitting carrier is used to carry the augmented reality waveguide structure to be manufactured, the mask grating has the same surface period as the grating unit, and the grating vector surface components of the mask grating and the grating unit are parallel, the collimated light generating mechanism is used to generate a collimated light beam that can be incident on the mask grating, and the collimated light beam is diffracted by the mask grating into zero-order light and first-order light, and the zero-order light and the first-order light are interferingly exposed on the augmented reality waveguide structure to be manufactured through the light-transmitting carrier. The first switching mechanism is used to switch the exposure position so that the zero-order light and the first-order light just cover only the grating unit to be exposed, and the second switching mechanism is used to switch the incident angle of the collimated light beam so that the incident angle of the collimated light beam corresponds to the grating unit to be exposed.

[0026] This solution generates zero-order light and first-order light for sequentially exposing each grating unit by diffracting a collimated light beam through a mask grating. The incident angle of the collimated light beam can be adjusted simultaneously to adjust the incident angles of the zero-order light and the first-order light. Compared with other methods, this solution has low complexity and controllable costs.

[0027] Compared with the prior art, this solution has the following beneficial effects: This solution estimates the grating vector distribution by sampling the positions of the effective areas of the eye movement range of multiple sub-fields and the grating vectors whose light matches the Bragg diffraction conditions, without considering the diffraction of invalid light that eventually enters outside the eye movement range, so that most of the effective light with different incident angles has a high diffraction efficiency on the volume holographic grating, so as to ensure the overall brightness uniformity of the output light beam and achieve the expansion of the field of view. On this basis, the grating vector of each sub-field of view light that accurately matches the Bragg diffraction conditions is placed at the coupling end of its effective area of ​​the eye movement range, so that the diffraction efficiency can be maximized at the coupling end as much as possible, which helps to improve the brightness uniformity of the effective light output from different positions of the volume holographic grating in each sub-field of view, thereby improving the uniformity of the field of view and the uniformity of the eye movement range. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are for illustrative purposes only and should not be construed as limitations on the present invention. In order to better illustrate the present invention, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0029] Figure 1 It is a schematic diagram of the transmission of light with an incident angle of α in a two-dimensional pupil expansion waveguide structure.

[0030] Figure 2 This is a schematic diagram of the effective area of ​​the eye movement range on the volume holographic grating for light with different incident angles.

[0031] Figure 3 It is a flow chart of the method for formulating raster vector distribution targets.

[0032] Figure 4 Schematic diagram of light transmission of a volume holographic grating with a spatially varying grating vector.

[0033] Figure 5 It is a flow chart of the method for making a volume holographic grating.

[0034] Figure 6 It is a schematic diagram of a volume holographic grating composed of multiple grating units.

[0035] Figure 7 This is a schematic diagram of the device for making volume holographic grating.

[0036] Figure 8 yes Figure 7 A top view of the device shown.

[0037] Fig. 9 It is an application Figure 4 Schematic diagram of the waveguide structure of the volume holographic grating shown.

[0038] Fig.10 It is the diffraction efficiency curve of the mask grating as it changes with angle.

[0039] Fig.11 Is adopted Fig.10 The diffraction efficiency curve of the volume holographic grating with spatially varying grating vector obtained by exposing the mask grating shown.

[0040] Description of the reference numerals: volume holographic grating 110, coupling-in grating 111, turning grating 112, coupling-out grating 113, substrate 120, mask 220, mask grating 221, light-transmitting carrier 230, light L0 output by the micro-projection optical machine, light L111 coupled in by the coupling-in grating, effective light L112a that eventually enters the eye movement range after the turning grating is expanded, invalid light L112b that eventually enters the outside of the eye movement range after the turning grating is expanded, effective light L112a that eventually enters the eye movement range after the coupling-out grating is coupled out Line L113a, invalid light L113b that finally enters outside the eye movement range after coupling out the grating, collimated light beam L210, zero-order light L2210, first-order light L2211, eye movement range effective area A of the light beam with an incident angle of α, eye movement range effective area A1 of the light beam with an incident angle of α1, eye movement range effective area A1 of the light beam with an incident angle of α2, eye movement range effective area A3 of the light beam with an incident angle of α3, eye movement range effective area A4 of the light beam with an incident angle of α4, grating unit u , grating vector surface component rxoy, coupling end e . DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the present solution, the present solution is further described in detail below in conjunction with specific embodiments.

[0042] Figure 3 The method for setting a grating vector distribution target is shown. The method can be used to set a grating vector distribution target for a volume holographic grating (especially a volume holographic grating for an augmented reality waveguide display), thereby expanding the angular bandwidth of the volume holographic grating obtained, which helps to expand the field of view of the optical waveguide, improve the uniformity of the field of view and the uniformity of the eye movement range. Figure 3 As shown, the method may include the following steps:

[0043] S11: Sampling multiple sub-fields of view.

[0044] In the display system, the field of view is the angle between the edge of the display and the line connecting the human eye. Light within the output angle of the entire field of view can enter the human eye to form a complete field of view image. In other words, the complete field of view image is presented by light entering the human eye at different input angles. For the convenience of description, this case defines the set of light rays with the same incident angle that eventually enter the entire field of view as a sub-field of view. All light rays in the same sub-field of view have the same incident angle, and the angles after diffraction by the volume holographic grating are also the same. The number of samples of the sub-field of view can be determined specifically based on the field of view size of the display system design. The sampling process can adopt random sampling methods such as simple random sampling, systematic sampling, group sampling, stratified sampling, etc., or non-random sampling methods such as encounter sampling, judgment sampling, equal sampling, and snowball sampling.

[0045] S12: Record the position of the effective area of ​​the eye movement range of each sub-field of view, and calculate the grating vector of the light of each sub-field of view matching the Bragg diffraction condition.

[0046] After the light of the sub-field of view is diffracted by the volume holographic grating, only a part of it enters the eye movement range and is finally received by the human eye. This part of the light can be called effective light. For the convenience of description, this case defines the area covered by the light that eventually enters the eye movement range on the volume holographic grating as the effective area of ​​the eye movement range. Therefore, the area covered by the light that eventually enters the eye movement range in the sub-field of view on the volume holographic grating is the effective area of ​​the eye movement range of the sub-field of view. Only the light in this area will enter the eye movement range after being output, and contribute to the complete picture seen by the human eye. The area outside of this area is invalid for the sub-field of view. The grating vector is a vector with an amplitude of 2π / P perpendicular to the grating plane, where P is the interval between adjacent grating planes, that is, the grating period. The grating vector that matches the Bragg diffraction condition can be calculated based on the Bragg diffraction condition and the incident angle of the light.

[0047] S13: Estimate the grating vector distribution of the volume holographic grating according to the positions of the effective areas of the eye movement range of the multiple sub-fields of view and the grating vectors of the light rays of the multiple sub-fields of view matching the Bragg diffraction conditions.

[0048] The grating vector distribution refers to the change of the grating vector in space, which describes how the grating vector changes with the change of position. Among them, the surface component of the grating vector refers to the component of the grating vector projected on the plane of the entire volume holographic grating. For the optical waveguide display, this surface component must be constant on the entire volume holographic grating, that is, the surface component of the grating vector at different positions remains constant, so as to ensure the one-to-one correspondence between the input angle and the output angle of the optical waveguide for different light rays, that is, to ensure the accuracy of waveguide imaging.

[0049] The grating vector distribution has at least one change direction, which can be a one-dimensional distribution or a two-dimensional distribution. The one-dimensional distribution has one change direction, and the two-dimensional distribution has two change directions that are perpendicular to each other. Generally speaking, at least one change direction in the grating vector distribution should be along the direction of the surface component of the grating vector. If the grating vector distribution is a one-dimensional distribution, its change direction is the same as the direction of the surface component of the grating vector; if the grating vector distribution is a two-dimensional distribution, one of its two change directions is the same as the direction of the surface component of the grating vector.

[0050] The grating vector distribution of the volume holographic grating is estimated by the positions of the effective areas of the eye movement range of multiple sub-fields of view and the grating vectors of their light matching the Bragg diffraction conditions. The diffraction of invalid light that eventually enters outside the eye movement range is not considered, so that most of the effective light with different incident angles has a higher diffraction efficiency on the volume holographic grating, so as to ensure the overall brightness uniformity of the output light beam and realize the expansion of the field of view.

[0051] S14: Determine the grating vector distribution of the volume holographic grating based on the estimated grating vector distribution and the principle that the grating vector at the coupling end of the effective area of ​​the eye movement range of each sub-field of view accurately matches the Bragg diffraction condition.

[0052] Based on the estimated grating vector distribution, for each sub-field of view, a grating vector that precisely matches the Bragg diffraction condition is placed at the coupling end of its effective area of ​​the eye movement range, so that the diffraction efficiency can be maximized as much as possible at the coupling end, which helps to improve the brightness uniformity of the effective light output from different positions of the volume holographic grating in each sub-field of view, thereby improving the uniformity of the field of view and the uniformity of the eye movement range.

[0053] Figure 4 The volume holographic grating (which can be called the first volume holographic grating) with a grating vector that varies in space is illustrated. The volume holographic grating can be used in optical waveguide display technology, specifically as an in-coupled grating, a turning grating, and an out-coupled grating in an augmented reality waveguide structure.

[0054] like Figure 4 As shown, the grating vector distribution of the volume holographic grating is estimated by sampling the positions of the effective areas of the eye movement range of multiple sub-fields of view and the grating vectors of the light rays matching the Bragg diffraction conditions, and the grating vectors of the coupling ends of the effective areas of the eye movement range of each sub-field of view accurately match the Bragg diffraction conditions. Among them, the grating vector distribution has at least one change direction, and at least one change direction is the same as the direction of the grating vector surface component, and the surface components of the grating vectors at different positions remain constant; the sub-field of view refers to the set of light rays with the same incident angle that eventually enter the entire field of view; the effective area of ​​the eye movement range refers to the area covered by the light rays that eventually enter the eye movement range on the volume holographic grating.

[0055] The grating vector distribution of the volume holographic grating is estimated by sampling the positions of the effective areas of the eye movement range of multiple sub-fields and the grating vectors of their rays matching the Bragg diffraction conditions. The diffraction of invalid rays that eventually enter outside the eye movement range is not considered, so that most of the effective rays with different incident angles have high diffraction efficiency on the volume holographic grating to ensure the overall brightness uniformity of the output beam and achieve the expansion of the field of view. On this basis, the grating vector of each sub-field of view that accurately matches the Bragg diffraction conditions is placed at the coupling end of its effective area of ​​the eye movement range, so that the diffraction efficiency is maximized at the coupling end as much as possible, which helps to improve the brightness uniformity of the effective light output from different positions of the volume holographic grating in each sub-field of view, thereby improving the uniformity of the field of view and the uniformity of the eye movement range. The grating vector of the volume holographic grating changes in space, but the surface components of the grating vectors at different positions remain constant, ensuring the one-to-one correspondence between the input angle and the output angle of different rays, that is, ensuring the accuracy of imaging.

[0056] Depending on the number of directions in which the grating vector changes, the grating vector distribution can be one-dimensional or two-dimensional. A one-dimensional distribution has one direction of change, and a two-dimensional distribution has two directions of change that are perpendicular to each other. If the grating vector distribution is one-dimensional, its direction of change is the same as the direction of the grating vector surface component; if the grating vector distribution is two-dimensional, one of its two directions of change is the same as the direction of the grating vector surface component.

[0057] The grating vector distribution of the above volume holographic grating can be expressed as Figure 3 The method shown is formulated.

[0058] Figure 5 The method of making a volume holographic grating is shown in FIG. Figure 4 The volume holographic grating shown in FIG. Figure 5 As shown, the method may include the following steps:

[0059] S21. Discretize the grating vector distribution into a plurality of grating units arranged at least along the direction of the grating vector surface component thereof, and the grating vectors at different positions of the same grating unit remain constant.

[0060] The production of volume holographic gratings with continuously changing grating vector distribution requires a high-precision exposure device with a customized beam shaping element or a customized mask grating, which is difficult and costly to produce. Discrete the grating vector distribution into multiple grating units, that is, discretize the volume holographic grating to be produced into multiple grating units, and keep the grating vectors at different positions of the same grating unit constant, which can reduce the production difficulty to a certain extent. The grating vector distribution can be discretized into one-dimensionally arranged grating units (such as Figure 6 ), can also be discretized into two-dimensionally arranged grating units. Generally speaking, at least one arrangement direction should be along the surface component direction of the grating vector. For optical waveguide displays, one-dimensionally arranged grating units are generally sufficient to meet the field of view requirements. The grating unit needs to select a suitable length or width. By evaluating the overall grating angular bandwidth formed by the grating vector distribution, a larger grating unit length or width is selected for ease of manufacturing. The lengths or widths of different grating units can be the same or different. A small amount of overlap is allowed at the boundaries between adjacent grating units.

[0061] S22. Select or make a mask grating whose surface period is equal to the surface period of the volume holographic grating to be made, so that the surface component of the grating vector of the volume holographic grating to be made is parallel to the surface component of the grating vector of the mask grating.

[0062] According to the diffraction principle, a collimated light beam is incident on the mask grating and diffracted. The diffracted zero-order light and the first-order light overlap and interfere on the volume holographic photosensitive material to be exposed. The amplitude of the surface component of the grating vector of the generated volume holographic grating is equal to that of the mask grating. Therefore, the amplitude of the surface component of the grating vector of the mask grating and the volume holographic grating to be produced should be set equal, that is, the surface periods of the two are equal.

[0063] The mask grating can specifically be an amplitude grating or phase grating made by photolithography, nanoimprinting or other micro-nano processing technologies, or a volume holographic grating made in advance by double-beam exposure. Using a volume holographic grating made by double-beam exposure as a mask grating can greatly reduce the production cost of the mask, but due to the Bragg diffraction characteristics of the volume holographic grating, its angular bandwidth is small, and the diffraction efficiency is very low at incident angles far from the Bragg diffraction conditions, which is not conducive to the production of a holographic grating for an optical waveguide with a large grating vector space variation range. Using a thinner volume holographic grating as a mask grating can expand the angular bandwidth, thereby expanding the grating vector space variation range of the optical waveguide. Specifically, the thickness of the volume holographic grating used as a mask grating is preferably 1~5μm.

[0064] The exposure precursor volume holographic photosensitive material should be placed on the exposure device in the correct orientation so that the grating vector surface component of the volume holographic grating to be produced is parallel to the grating vector surface component of the mask grating, such as Figure 8 shown.

[0065] S23. Calculate the incident angle of the collimated light beam corresponding to each grating unit according to the grating vector of the grating unit and the grating vector of the mask grating.

[0066] When the incident angle of the incident collimated light beam is changed, the amplitude of the surface component of the grating vector of the generated volume holographic grating remains unchanged, but the normal component of the grating vector changes, and the synthesized grating vector also changes. This method can be used to make a volume holographic grating whose grating vector varies with space. To facilitate subsequent rapid exposure, the incident angle of the collimated light beam corresponding to each grating unit can be calculated in advance based on the grating vector of the grating unit and the grating vector of the mask grating.

[0067] S24. Simultaneously switch to the exposure position and incident angle of the collimated light beam corresponding to a certain grating unit, so that the zero-order light and the first-order light generated by the diffraction of the collimated light beam through the mask grating interfere with each other on the volume holographic photosensitive material, and expose each grating unit in turn.

[0068] The area corresponding to each grating unit with a specific grating vector can be exposed in sequence. Each time a grating unit is switched, the angle of the incident collimated light beam needs to be readjusted to a pre-calculated angle according to the corresponding grating vector, so as to generate the corresponding grating vector by exposure at the corresponding grating unit.

[0069] Figure 7-8 The apparatus for making volume holographic grating is shown in FIG. Figure 5 The method shown is to make Figure 4 The volume holographic grating shown in FIG. Figure 7-8As shown, the device includes a collimated light generating mechanism (not shown in the figure), a mask grating and a transparent carrier which are arranged in sequence, and also includes a first switching mechanism (not shown in the figure) and a second switching mechanism (not shown in the figure). The transparent carrier is used to carry the volume holographic photosensitive material, the surface period of the mask grating is the same as the surface period of the volume holographic grating to be made, and its grating vector surface component is parallel to the grating vector surface component of the volume holographic grating to be made, the collimated light generating mechanism is used to generate a collimated light beam that can be incident on the mask grating, the collimated light beam is diffracted by the mask grating into zero-order light and first-order light, and the zero-order light and the first-order light are transmitted through the transparent carrier to interfere with the exposure on the volume holographic photosensitive material. It should be noted that if the prepared volume holographic grating is used for an augmented reality waveguide structure, the transparent carrier can directly carry the augmented reality waveguide structure to be made, that is, carry two layers of transparent substrates and the volume holographic photosensitive material arranged between the two layers of substrates, and after interference exposure, the volume holographic photosensitive material forms a volume holographic grating arranged between the two layers of substrates.

[0070] The first switching mechanism is used to switch the exposure position so that the zero-order light and the first-order light just cover the grating unit to be exposed; the second switching mechanism is used to switch the incident angle of the collimated light beam so that the incident angle of the collimated light beam corresponds to the grating unit to be exposed. Since the incident light beam angle for exposing each grating unit corresponds to the grating vector one by one, the incident angle of the collimated light beam must be switched when switching the exposure position, that is, the first switching mechanism and the second switching mechanism must act together. If both the first switching mechanism and the second switching mechanism are automated mechanisms, they can act simultaneously, which helps to quickly expose multiple grating units in sequence.

[0071] The mask grating can specifically be an amplitude grating or phase grating made by photolithography, nanoimprinting or other micro-nano processing technology, or a volume holographic grating made in advance by double-beam exposure (which can be called a second volume holographic grating). Using a volume holographic grating made by double-beam exposure as a mask grating can greatly reduce the production cost of the mask, but due to the Bragg diffraction characteristics of the volume holographic grating, its angular bandwidth is small, and the diffraction efficiency is very low at the incident angle far from the Bragg diffraction condition, which is not conducive to the production of a holographic grating of an optical waveguide with a large grating vector space variation range. Using a thinner volume holographic grating as a mask grating can expand the angular bandwidth, thereby expanding the grating vector space variation range of the optical waveguide. Specifically, the thickness of the volume holographic grating used as a mask grating is preferably 1~5μm.

[0072] Fig. 9The structure of the augmented reality waveguide is shown. The waveguide structure includes two transparent substrates, and an in-coupling grating, a turning grating, and an out-coupling grating arranged between the two substrates. The in-coupling grating, the turning grating, and the out-coupling grating all use the above-mentioned volume holographic grating whose grating vector varies in space. It can be understood that the waveguide structure can also be a one-dimensional pupil expansion waveguide that does not include the turning grating, and only one or two of the in-coupling grating, the turning grating, and the out-coupling grating can also use the above-mentioned volume holographic grating whose grating vector varies in space.

[0073] The above scheme can expand the angular bandwidth of the volume holographic grating, which actually provides different Bragg matching angles that can effectively contribute at different positions of the volume holographic grating, thereby helping to expand the field of view and improve the uniformity of the field of view and the uniformity of the eye movement range. Moreover, the manufacturing method and device provided by the above scheme are less complex and cost-controlled than other methods. For example, Fig.10 The figure shows a possible curve of the diffraction efficiency of the mask grating changing with the angle. The collimated light beams with three incident angles of about -6 degrees, 2.5 degrees, and 10 degrees are selected to expose three different grating units in sequence to obtain the out-coupled grating composed of grating units with three different grating vectors. The curve of the diffraction efficiency changing with the angle is shown in FIG. Fig.11 As shown, the angular bandwidth of the combination is extended.

[0074] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. An augmented reality waveguide structure, characterized in that: The augmented reality waveguide structure includes two transparent substrates and a first volume holographic grating arranged between the two substrates; the grating vector distribution of the first volume holographic grating is obtained by sampling the positions of the effective areas of the eye movement range of multiple sub-fields of view and estimating the grating vectors of the light rays matching the Bragg diffraction conditions, and the grating vectors of the coupling ends of the effective areas of the eye movement range of each sub-field of view accurately match the Bragg diffraction conditions; Wherein, the grating vector distribution has at least one changing direction, and at least one changing direction is the same as the direction of the grating vector surface component, and the surface components of the grating vectors at different positions remain constant; the sub-field of view refers to the set of light rays with the same incident angle that eventually enter the entire field of view; the effective area of ​​the eye movement range refers to the area covered by the light rays that eventually enter the eye movement range on the first volume holographic grating.

2. The augmented reality waveguide structure according to claim 1, characterized in that: The grating vector distribution is a one-dimensional distribution or a two-dimensional distribution.

3. The augmented reality waveguide structure according to claim 1, characterized in that: The volume holographic grating and its grating vector distribution include a plurality of discrete grating units, wherein the plurality of grating units are arranged at least along the direction of the surface component of the grating vector thereof, and the grating vectors at different positions of the same grating unit remain constant.

4. The augmented reality waveguide structure according to claim 3, characterized in that: The volume holographic grating and its grating vector distribution include a plurality of grating units arranged in one dimension or two dimensions.

5. The augmented reality waveguide structure according to claim 3 or 4, characterized in that: The first volume holographic grating includes an incoupling region, a turning region and / or an outcoupling region.

6. The augmented reality waveguide structure according to claim 5, characterized in that: The first volume holographic grating includes an incoupling region and an outcoupling region.

7. The augmented reality waveguide structure according to claim 5, characterized in that: The first volume holographic grating includes an incoupling region, a turning region and an outcoupling region.

8. A device for manufacturing an augmented reality waveguide structure as claimed in any one of claims 3 to 7, characterized in that: The device comprises a collimated light generating mechanism, a mask grating and a light-transmitting carrier which are arranged in sequence, wherein the light-transmitting carrier is used to carry an augmented reality waveguide structure to be manufactured, the mask grating has the same surface period as a grating unit, and the grating vector surface components of the mask grating and the grating unit are parallel, the collimated light generating mechanism is used to generate a collimated light beam which can be incident on the mask grating, the collimated light beam is diffracted by the mask grating into zero-order light and first-order light, and the zero-order light and the first-order light are transmitted through the light-transmitting carrier to perform interference exposure on the augmented reality waveguide structure to be manufactured; The device also includes a first switching mechanism and a second switching mechanism that act simultaneously, wherein the first switching mechanism is used to switch the exposure position so that the zero-order light and the first-order light just cover only the grating unit to be exposed, and the second switching mechanism is used to switch the incident angle of the collimated light beam so that the incident angle of the collimated light beam corresponds to the grating unit to be exposed.

9. The device according to claim 8, characterized in that The mask grating is an amplitude grating, a phase grating or a second volume holographic grating.

10. The device according to claim 9, characterized in that The mask grating is a second volume holographic grating with a thickness of 1-5 μm.

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