Optical waveguide structure, near-eye display system and grating preparation device and method

Abstract

The invention discloses an optical waveguide structure, a near-to-eye display system, head-mounted display equipment, a grating preparation device and a grating preparation method. The optical waveguide structure comprises a waveguide substrate, a coupling-in grating and a coupling-out grating, the coupling-in grating and the coupling-out grating are arranged on the waveguide substrate, the coupling-in grating is used for coupling incident light into the waveguide substrate, and the coupling-out grating is used for coupling light in the waveguide substrate out of the waveguide substrate. The out-coupling grating is a partition grating, and the out-coupling grating is partitioned according to a first action point of light in the waveguide substrate on the out-coupling grating. The partitioned grating comprises a plurality of grating areas, and grating vectors of at least part of the grating areas are different. Therefore, diffraction efficiency regulation and control are realized, the exit pupil uniformity of the optical waveguide structure is improved, the field angle of the optical waveguide structure is not affected, and mass production is facilitated.

Description

Technical Field

[0001] This application relates to the field of optical waveguide technology, and in particular to an optical waveguide structure, a near-eye display system, a head-mounted display device, a grating fabrication apparatus, and a grating fabrication method. Background Technology

[0002] Augmented Reality (AR) is a crucial frontier in next-generation information technology, profoundly changing human production and lifestyles. AR display technologies based on optical waveguides can be mainly divided into three categories: arrayed waveguides, surface-embossed waveguides, and volume holographic waveguides. Among them, volume holographic waveguides utilize Bragg volume gratings, which possess strong wavelength and angle selectivity. Therefore, volume holographic waveguides exhibit weaker rainbow patterns and lower forward leakage. Furthermore, due to their low-cost fabrication, volume holographic waveguides have become one of the most promising AR display technologies. However, current holographic waveguides suffer from poor exit pupil uniformity. Summary of the Invention

[0003] This application provides an optical waveguide structure, a near-eye display system, a head-mounted display device, a grating fabrication apparatus, and a grating fabrication method to solve at least one of the aforementioned technical problems.

[0004] The optical waveguide structure of this application includes a waveguide substrate and a coupling grating and a coupling grating disposed on the waveguide substrate. The coupling grating is used to couple incident light into the waveguide substrate, and the coupling grating is used to couple light from the waveguide substrate out of the waveguide substrate.

[0005] The output grating is a partitioned grating, and the output grating is partitioned according to the first point of action of the light rays in the waveguide substrate on the output grating;

[0006] The partitioned grating includes multiple grating regions, and at least some of the grating regions have different grating vectors.

[0007] In some embodiments, the optical waveguide structure further includes a folding grating for folding the coupled light rays, and an output grating for coupling the folded light rays out of the waveguide substrate;

[0008] The folding grating is a partitioned grating, and the folding grating is partitioned according to the second point of action of the coupled light rays on the folding grating.

[0009] In some embodiments, the different grating vectors include:

[0010] The directions of the grating vectors are different; and / or the amplitudes of the grating vectors are different.

[0011] In some embodiments, in the partitioned grating, the grating vectors of the plurality of grating regions have the same component in the waveguide substrate.

[0012] In some implementations, the plurality of grating regions are in the form of Thiessen polygons.

[0013] The near-eye display system according to the embodiments of this application includes the optical waveguide structure of any of the above embodiments.

[0014] The head-mounted display device according to the embodiments of this application includes the above-described near-eye display system.

[0015] The grating fabrication apparatus of this application is used to fabricate optical waveguide structures of any of the above embodiments. The grating fabrication apparatus includes a laser, a polarization beam splitter, two phase modulation elements, and two sets of coherent optical systems.

[0016] The laser is used to emit laser light;

[0017] The polarization beam splitter is used to split the laser beam into two paths, which are then transmitted to the grating to be modulated for zoned exposure through the two sets of coherent optical systems respectively.

[0018] The two phase modulation elements are used to perform phase modulation on the two laser beams according to different grating regions of the grating to be modulated;

[0019] The two sets of coherent optical systems are used to interfere and superimpose the phases modulated by the two phase modulation elements at the corresponding grating regions of the grating to be modulated, so as to obtain the partitioned grating.

[0020] In some embodiments, the phase modulation element includes one of a spatial light modulator, a diffractive optical element, a blazed grating, and a metasurface.

[0021] In some embodiments, the phase modulation element includes a spatial light modulator, each set of coherent optical systems includes a lens optical system and an objective lens optical system, and the grating fabrication apparatus further includes a moving platform;

[0022] Each laser beam is transmitted sequentially through the lens optical system and the objective lens optical system to the grating to be modulated;

[0023] The mobile platform is used to carry the grating to be modulated and can drive the grating to be modulated to move so that the laser sequentially irradiates different grating areas of the grating to be modulated for sequential partitioned exposure.

[0024] Each of the phase modulation elements is used to sequentially perform phase modulation according to different grating regions of the grating to be modulated.

[0025] In some embodiments, the phase modulation element includes a diffractive optical element, a blazed grating, or a metasurface, and each set of coherent optical systems includes a lens optical system;

[0026] Each laser beam is transmitted to the grating to be modulated via the lens optical system;

[0027] The laser simultaneously illuminates different grating regions of the grating to be modulated to achieve simultaneous zoned exposure;

[0028] Each of the phase modulation elements is used to simultaneously perform phase modulation according to different grating regions of the grating to be modulated.

[0029] The grating fabrication method of this application, applied to the grating fabrication apparatus of any of the above embodiments, includes:

[0030] The grating vector distribution of the grating to be modulated in different grating regions is determined according to the predetermined optical design;

[0031] The grating phase distribution is determined based on the grating vector distribution;

[0032] The phases of the two phase modulation elements are determined according to the grating phase distribution;

[0033] The grating to be modulated is exposed in sections, and the phase modulation element is controlled to adjust the phase according to different grating regions of the grating to be modulated, so as to obtain the sectioned grating.

[0034] In some embodiments, the phase modulation element includes a spatial light modulator, and the grating fabrication apparatus further includes a moving platform. The step of performing partitioned exposure on the grating to be modulated and controlling the phase modulation element to adjust the phase according to different grating regions of the grating to be modulated to obtain the partitioned grating includes:

[0035] Based on the position of the grating to be modulated in the waveguide substrate, the moving platform drives the grating to be modulated to move, so that different grating regions of the grating to be modulated are exposed sequentially in sections, and the phase modulation element is controlled to adjust the phase sequentially according to the different grating regions of the grating to be modulated, so as to obtain the sectioned grating.

[0036] In some embodiments, the phase modulation element includes a diffractive optical element, a blazed grating, or a metasurface. The step of performing zoned exposure on the grating to be modulated and controlling the phase modulation element to adjust the phase according to different grating regions of the grating to be modulated to obtain the zoned grating includes:

[0037] The different grating regions of the grating to be modulated are simultaneously exposed in separate sections, and the phase modulation element is controlled to adjust the phase according to the different grating regions of the grating to be modulated, so as to obtain the partitioned grating.

[0038] In the waveguide structure, near-eye display system, head-mounted display device, grating fabrication apparatus, and grating fabrication method of this application, the coupling grating is a partitioned grating, and at least some of the grating regions in the partitioned grating have different grating vectors to control the Bragg shift of the incident light. This achieves diffraction efficiency control, improving the exit pupil uniformity of the waveguide structure without affecting the field of view, and is easy to mass-produce.

[0039] Additional aspects and advantages of embodiments of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of this application. Attached Figure Description

[0040] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0041] Figure 1 This is a schematic diagram of an optical waveguide structure according to certain embodiments of this application;

[0042] Figure 2 This is a schematic diagram of the transmission of normally incident light in an optical waveguide structure of related technologies;

[0043] Figure 3 This is a schematic diagram of the transmission of non-normally incident light in the optical waveguide structure of related technologies;

[0044] Figure 4 This is a schematic diagram of a near-eye display system according to certain embodiments of this application;

[0045] Figure 5 This is a schematic diagram of a head-mounted display device according to certain embodiments of this application;

[0046] Figure 6 This is a schematic diagram of the structure of a grating fabrication apparatus according to certain embodiments of this application;

[0047] Figure 7 This is a schematic diagram of the structure of a grating fabrication apparatus according to certain embodiments of this application;

[0048] Figure 8 This is a schematic flowchart of a grating fabrication method according to certain embodiments of this application;

[0049] Figure 9 This is a schematic flowchart of a grating fabrication method according to certain embodiments of this application;

[0050] Figure 10 This is a schematic flowchart of a grating fabrication method according to certain embodiments of this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] Optical waveguide structure 100, waveguide substrate 10, coupling grating 20, folding grating 30, coupling out grating 40, near-eye display system 200, head-mounted display device 300, grating fabrication device 400, grating to be modulated 401, laser 410, polarization beamsplitter (first polarization beamsplitter) 420, second polarization beamsplitter 421, third polarization beamsplitter 422, phase modulation element 430, first phase modulation element 431, second phase modulation element 432, coherent optical system 440, first coherent optical system 441, second coherent optical system 442, lens optical system 443, first lens optical system 4431, third lens 4432, fourth lens 4433, second lens optical system 4434, sixth lens 4435, and so on. 7-lens 4436, objective lens optical system 444, first objective lens optical system 4441, fifth lens 4442, first objective lens 4443, second objective lens optical system 4444, eighth lens 4445, second objective lens 4446, moving platform 450, shutter 461, reflecting mirror 462, first reflecting mirror 4621, second reflecting mirror 4622, half-wave plate 463, first half-wave plate 4631, second half-wave plate 4632, third half-wave plate 4633, fourth half-wave plate 4634, spatial filter 464, first spatial filter 4641, second spatial filter 4642, lens 465, first lens 4651, second lens 4652, aperture stop 466, first aperture stop 4661, second aperture stop 4662. Detailed Implementation

[0053] The embodiments of this application will be further described below with reference to the accompanying drawings. The same or similar reference numerals in the drawings denote the same or similar elements or elements having the same or similar functions throughout. Furthermore, the embodiments of this application described below with reference to the accompanying drawings are exemplary and are only used to explain the embodiments of this application, and should not be construed as limiting this application.

[0054] Please see Figure 1This application provides an optical waveguide structure 100. The optical waveguide structure 100 includes a waveguide substrate 10 and a coupling grating 20 and a coupling grating 40 disposed on the waveguide substrate 10. The coupling grating 20 couples incident light into the waveguide substrate 10, and the coupling grating 40 couples light out of the waveguide substrate 10. The coupling grating 40 is a partitioned grating, and the coupling grating 40 partitions the waveguide substrate 10 according to the first point of action of the light on the coupling grating 40. The partitioned grating includes multiple grating regions, and at least some of the grating regions have different grating vectors.

[0055] In the optical waveguide structure 100 of this embodiment, the coupling grating 40 employs a partitioned grating, where at least some of the grating regions in the partitioned grating have different grating vectors to control the Bragg shift of the incident light. This achieves diffraction efficiency control, improving the exit pupil uniformity of the optical waveguide structure 100 without affecting its field of view, and is also easy to mass-produce.

[0056] Specifically, the insertion grating 20 and the output grating 40 can be volume holographic gratings. The propagation path of light in the optical waveguide structure 100 is as follows: the light emitted from the image source reaches the optical waveguide structure 100 after passing through the collimation system, and is coupled into the waveguide substrate 10 from the insertion grating 20. The light in the waveguide substrate 10 is coupled out of the waveguide substrate 10 through the output grating 40, thereby realizing the expansion of the exit pupil.

[0057] The coupling grating 40 can be a partitioned grating, with the surface of each partitioned grating divided into multiple grating regions. The division of the grating regions is related to the point of action of the light rays on the grating. For the coupling grating 40, the partitioning can be based on the first point of action of the light rays in the waveguide substrate 10 on the coupling grating 40. The specific process is as follows: by tracing incident light rays at different angles, after the incident light rays from multiple angles are coupled into the waveguide substrate 10, the position where the coupled light rays act on the coupling grating 40 is the first point of action, such as... Figure 1 As shown at midpoint A. The coupled grating 40 can be partitioned according to the first point of action to form a partitioned grating, with each grating region including a first point of action.

[0058] It should be noted that there is no limit to the number of grating regions; there can be 3, 4, 5, or more. At least some of the grating regions must have different grating vectors; that is, the grating vectors of multiple grating regions can be completely different, or they can be partially the same and partially different.

[0059] In related technologies, to improve the uniformity of the exit pupil of an optical waveguide, the diffraction efficiency of the grating in the optical waveguide is controlled by partitioning. For example... Figure 2As shown, the coupling grating is divided into three regions, R1, R2, and R3. All three regions have the same diffraction efficiency. Therefore, the intensity of the coupled light gradually decreases from left to right, resulting in poor exit pupil uniformity. Figure 3 As shown, the diffraction efficiencies of the three regions are set to 33%, 50%, and 100% from left to right, respectively. At this point, the exit pupil uniformity of normally incident light is optimal. However, for non-normally incident light, the number of interactions with the three regions of the coupling grating is different, resulting in an uneven exit pupil.

[0060] Research has revealed that the diffraction efficiency of a grating is primarily determined by two factors: the grating thickness and refractive index modulation, and the Bragg shift of the incident light. Related technologies control the grating diffraction efficiency by adjusting its thickness and refractive index modulation. However, the refractive index modulation at different positions of the grating affects the field of view of the waveguide structure, and controlling the grating thickness increases the difficulty of mass production.

[0061] In this embodiment, the coupling grating 40 employs a partitioned grating. Compared to dividing the coupling grating 40 into three regions, the partitioned grating allows for finer partitioning and can include more grating regions. At least some of the grating regions within the partitioned grating have different grating vectors. By adjusting the grating vectors of different grating regions, the Bragg shift of the incident light is controlled. This achieves diffraction efficiency control, improves the exit pupil uniformity of the optical waveguide structure 100, and, compared to adjusting the refractive index modulation, does not affect the field of view of the optical waveguide structure 100; and, compared to controlling the grating thickness, facilitates mass production.

[0062] Please see Figure 1 In some embodiments, the optical waveguide structure 100 further includes a folding grating 30. The folding grating 30 is used to fold the incident light, and the coupling grating 40 is used to couple the folded light out of the waveguide substrate 10. The folding grating 30 is a partitioned grating, and the folding grating 30 partitions the light according to the first point of action of the incident light on the folding grating 30.

[0063] Specifically, the optical waveguide structure 100 also includes a folding grating 30, which can be a volume holographic grating. After the incident light is coupled into the waveguide substrate 10 from the coupling grating 20, the folding grating 30 is used to fold the coupled light. At this time, the coupling grating 40 is used to couple the folded light out of the waveguide substrate 10, thereby realizing two-dimensional exit pupil expansion. The folding grating 30 can also be a partitioned grating.

[0064] The partitioning process is as follows: By tracing incident light rays at different angles, after the incident light rays from multiple angles are coupled into the waveguide substrate 10, the position where the coupled light rays act on the folding grating 30 is the second point of action, such as... Figure 1As shown at midpoint B. Based on the first point of action, the folding grating 30 can be divided into sections to form a partitioned grating, with each grating region including a second point of action.

[0065] In this case, the incident ray is deflected by the deflection grating 30, and the position where the deflected ray acts on the output grating 40 is the first point of action, such as... Figure 1 As shown at midpoint A. The coupling grating 40 can be partitioned according to the first point of action to form a partitioned grating, with each grating region including a first point of action. Thus, partitioning based on the positions where incident light rays at different angles interact with the grating can improve the uniformity of the exit pupil of the optical waveguide structure 100.

[0066] In this embodiment, both the coupling grating 40 and the folding grating 30 are partitioned gratings. At least some of the grating regions in the partitioned grating have different grating vectors to control the Bragg shift of the incident light. This further achieves diffraction efficiency control, improving the exit pupil uniformity of the optical waveguide structure 100 without affecting its field of view, and is also easy to mass-produce.

[0067] In some embodiments, different grating vectors can mean different grating vector directions, different grating vector amplitudes, or different grating vector directions and amplitudes. Specific cases of different grating vectors are not limited here.

[0068] In some embodiments, the grating vectors may differ in direction and / or amplitude, but their components in the waveguide substrate 10 are the same. Same components mean that the projection size of the grating vector along the surface of the waveguide substrate 10 is the same. It should be noted that within the same partitioned grating, the grating vectors of multiple grating regions have the same components in the waveguide substrate 10; however, in different partitioned gratings, the components of the grating vectors in the waveguide substrate 10 may differ. For example, the components of the grating vector in the coupling grating 40 and the grating vector in the folded grating 30 may differ. This ensures that the diffraction distances of multiple grating regions within the same partitioned grating are the same, ensuring the control of diffraction efficiency of light incident at the same angle in different grating regions. This improves the exit pupil uniformity of the optical waveguide structure 100 without affecting the field of view of the optical waveguide structure 100, and facilitates mass production.

[0069] Please see Figure 1 In some implementations, the multiple grating regions are in the form of Thiessen polygons.

[0070] Specifically, the Thiessen polygons are a set of continuous polygons, each containing only one control point. The distance from any point within a polygon to the control point constituting that polygon is less than the distance to the control points of other polygons. For the partitioned grating corresponding to the folding grating 30, the second action point is the control point. The perpendicular bisectors of the lines connecting two adjacent second action points are drawn, and all perpendicular bisectors are connected to form the Thiessen polygons, with each polygon constituting a grating region.

[0071] Similarly, for the partitioned grating corresponding to the coupling grating 40, the first point of action is the control point. The perpendicular bisector of the line connecting two adjacent first points of action is drawn. Connecting all the perpendicular bisectors forms a Thiessen polygon, and each polygon is a grating region.

[0072] Subsequently, based on the partitioning results, the grating vector of each grating region is adjusted to obtain a partitioned grating, thereby controlling the Bragg offset of the incident light. The specific process of grating vector adjustment is as follows: The grating vector includes a first component along the plane of the waveguide substrate 10 and a second component along the thickness of the waveguide substrate 10. The first component of each grating region is kept consistent, while the second component is set differently. In this way, multiple grating regions have different grating vectors.

[0073] The grating regions divided by the Thiessen polygon can optimize the distribution of the grating without affecting the field of view of the optical waveguide structure 100. By adjusting the grating vector of each grating region, the energy distribution of light rays in different field of view directions can be precisely controlled, thereby improving the uniformity of the exit pupil of the optical waveguide structure 100.

[0074] Please see Figure 1 and Figure 4 This application also provides a near-eye display system 200, which includes the optical waveguide structure 100 of any of the above embodiments. Furthermore, the near-eye display system 200 may also include an image source and a collimation system, wherein light emitted from the image source is at least partially input into the optical waveguide structure 100 via the collimation system.

[0075] Please see Figure 5 This application also provides a head-mounted display device 300, which includes the aforementioned near-eye display system 200. The head-mounted display device 300 is, for example, an augmented reality head-mounted display device.

[0076] Please see Figure 1 , Figure 6 and Figure 7This application also provides a grating fabrication apparatus 400. The grating fabrication apparatus 400 is used to fabricate the optical waveguide structure 100 of any of the above embodiments. The grating fabrication apparatus 400 includes a laser 410, a polarization beam splitter 420, two phase modulation elements 430, and two sets of coherent optical systems 440. The laser 410 is used to emit laser light. The polarization beam splitter 420 is used to split the laser beam into two paths, which are then transmitted to the grating 401 to be modulated for partitioned exposure via the two sets of coherent optical systems 440. The two phase modulation elements 430 are used to modulate the phases of the two laser beams according to different grating regions of the grating 401 to be modulated. The two sets of coherent optical systems 440 are used to interfere and superimpose the phases modulated by the two phase modulation elements 430 at corresponding grating regions of the grating 401 to obtain a partitioned grating.

[0077] In the grating fabrication apparatus 400 of this application embodiment, a partitioned grating is fabricated using phase modulation exposure. Two phase modulation elements 430 modulate the phases of two laser beams according to different grating regions of the grating 401 to be modulated. The phases modulated by the two phase modulation elements 430 pass through corresponding coherent optical systems 440 and are interferometrically superimposed at the corresponding grating regions of the grating 401 to be modulated, thus obtaining the partitioned grating. This increases the degree of freedom in optical waveguide design, and the resulting optical waveguide structure 100 has better exit pupil uniformity and optical efficiency.

[0078] Specifically, the grating 401 to be modulated (i.e., the folded grating 30 or the coupling grating 40 before modulation) in the optical waveguide structure 100 is placed between two sets of coherent optical systems 440. The laser 410 emits laser light, which is split into two beams by the polarization beam splitter 420. The two laser beams are transmitted to the grating 401 to be modulated through the two sets of coherent optical systems 440 respectively, so as to perform dual-beam partitioned exposure on the grating 401 to be modulated.

[0079] Two phase modulation elements 430 are respectively disposed between the polarization beam splitter 420 and the corresponding coherent optical system 440. The phase modulation elements 430 can modulate the phase of the two lasers according to different grating regions of the grating 401 to be modulated, so that at least some of the grating regions have different grating vectors. The coherent optical system 440 is used to perform interference superposition of the phases modulated by the corresponding phase modulation elements 430 at the corresponding grating regions of the grating 401 to be modulated, to obtain a partitioned grating.

[0080] Different grating regions correspond to different grating vectors, which means that during exposure preparation, phase adjustment is required based on the desired grating vector of the current area to be exposed. This allows the coherent optical system 440 to interfere and superimpose at the area to be exposed based on the adjusted phase, thereby exposing the grating vector.

[0081] In related technologies, it is difficult to control the diffraction efficiency of each region with a high degree of freedom during the fabrication of gratings, resulting in poor exit pupil uniformity of the optical waveguide structure. In this embodiment, a partitioned grating is fabricated using phase modulation exposure. Two phase modulation elements 430 modulate the phases of two laser beams according to different grating regions of the grating 401 to be modulated, allowing for a high degree of freedom in phase modulation. The phases modulated by the two phase modulation elements 430 are then passed through corresponding coherent optical systems 440 and interferometrically superimposed at the corresponding grating regions of the grating 401 to be modulated, resulting in a partitioned grating. Different grating regions within the partitioned grating have different diffraction efficiencies. This improves the freedom of optical waveguide design, resulting in an optical waveguide structure 100 with better exit pupil uniformity and optical efficiency.

[0082] In some embodiments, in addition to polarization beamsplitter 420 (hereinafter referred to as first polarization beamsplitter 420), the grating fabrication apparatus 400 may also include a second polarization beamsplitter 421 and a third polarization beamsplitter 422. The first polarization beamsplitter 420 is used to split the laser beam emitted by the laser 410 into two paths, namely a first optical path (e.g., ...). Figure 6 and Figure 7 The left optical path) and the second optical path (such as Figure 6 and Figure 7 (Right optical path in the middle). For ease of distinction, the coherent optical system 440 and the corresponding phase modulation element 430 on the first optical path are defined as the first coherent optical system 441 and the first phase modulation element 431, and the coherent optical system 440 and the corresponding phase modulation element 430 on the second optical path are defined as the second coherent optical system 442 and the second phase modulation element 432.

[0083] The second polarization beam splitter 421 is disposed in the first optical path, located between the first phase modulation element 431 and the first coherent optical system 441. The third polarization beam splitter 422 is disposed in the second optical path, located between the second phase modulation element 432 and the second coherent optical system 442. The second polarization beam splitter 421 and the third polarization beam splitter 422 are used to split the laser beam to the phase modulation element 430 for phase modulation, and then transmit the phase-modulated laser to the coherent optical system 440.

[0084] In some embodiments, the grating fabrication apparatus 400 further includes a shutter 461, a mirror 462, and a half-wave plate 463. The shutter 461 is positioned between the laser 410 and the first polarizing beam splitter 420 to control the laser emission time, thereby controlling the exposure time of the grating 401 to be modulated. The mirror 462 is used to deflect the laser beam path. In one example, the grating fabrication apparatus 400 includes two mirrors 462, namely a first mirror 4621 and a second mirror 4622. The first mirror 4621 is positioned between the shutter 461 and the first polarizing beam splitter 420, and the second mirror 4622 is positioned between the first polarizing beam splitter 420 and the second polarizing beam splitter 421.

[0085] A half-wave plate 463 is used to adjust the polarization state of the laser. The half-wave plate 463 can cooperate with a polarization beam splitter 420 to control the energy ratio of the two laser beams after splitting. In one example, the grating fabrication apparatus 400 includes four half-wave plates 463: a first half-wave plate 4631, a second half-wave plate 4632, a third half-wave plate 4633, and a fourth half-wave plate 4634. The first half-wave plate 4631 is disposed between the first reflector 4621 and the first polarization beam splitter 420; the second half-wave plate 4632 is disposed between the first polarization beam splitter 420 and the second reflector 4622; the third half-wave plate 4633 is disposed between the second reflector 4622 and the second polarization beam splitter 421; and the fourth half-wave plate 4634 is disposed between the first polarization beam splitter 420 and the third polarization beam splitter 422.

[0086] In some embodiments, the grating fabrication apparatus 400 further includes a spatial filter 464, a lens 465, and an aperture stop 466. There are two spatial filters 464, two lenses 465, and two aperture stops 466, respectively disposed in the first optical path and the second optical path. The spatial filter 464 includes a first spatial filter 4641 and a second spatial filter 4642. The first spatial filter 4641 is disposed between the second reflector 4622 and the third half-wave plate 4633, and the second spatial filter 4642 is disposed between the first polarizing beam splitter 420 and the fourth half-wave plate 4634, used to remove higher-order modes and noise from the laser beam.

[0087] Lens 465 includes a first lens 4651 and a second lens 4652. The first lens 4651 is disposed between the first spatial filter 4641 and the third half-wave plate 4633, and the second lens 4652 is disposed between the second spatial filter 4642 and the fourth half-wave plate 4634. Aperture stop 466 includes a first aperture stop 4661 and a second aperture stop 4662. The first aperture stop 4661 is disposed in the first coherent optical system 441, and the second aperture stop 4662 is disposed in the second coherent optical system 442, for optical filtering of the laser beam.

[0088] Please see Figure 6 and Figure 7 In some embodiments, the phase modulation element 430 includes one of a spatial light modulator, a diffractive optical element, a blazed grating, and a metasurface.

[0089] Specifically, spatial light modulators, diffractive optical elements, blazed gratings, and metasurfaces can all be used to phase modulate laser beams, and one of them can be used as the phase modulation element 430. For example, a spatial light modulator can be used as the phase modulation element 430; or a diffractive optical element can be used as the phase modulation element 430; or a blazed grating can be used as the phase modulation element 430; or a metasurface can be used as the phase modulation element 430.

[0090] Please see Figure 6 In some embodiments, the phase modulation element 430 includes a spatial light modulator. Each coherent optical system 440 includes a lens optical system 443 and an objective lens optical system 444. The grating fabrication apparatus 400 also includes a moving platform 450. Each laser beam is sequentially transmitted through the lens optical system 443 and the objective lens optical system 444 to the grating 401 to be modulated. The moving platform 450 is used to carry the grating 401 to be modulated and can move the grating 401 to be modulated so that the laser sequentially illuminates different grating regions of the grating 401 to be modulated for sequential partitioned exposure. Each phase modulation element 430 is used to sequentially perform phase modulation according to different grating regions of the grating 401 to be modulated.

[0091] Specifically, when a spatial light modulator is used as the phase modulation element 430, each coherent optical system 440 includes a lens optical system 443 and an objective lens optical system 444. The lens optical system 443 and the objective lens optical system 444 can be 4f optical systems, that is, each coherent optical system includes two 4f optical systems. The 4f optical system has the effect of optical filtering.

[0092] The lens optical system 443 includes two lenses, and the objective lens optical system 444 includes one lens and one objective lens. The aperture stop 466 can be disposed within the lens optical system 443, and the lens optical system 443, in conjunction with the aperture stop 466, performs optical filtering on the laser beam. The objective lens optical system 444 is used to reduce the spot radius of the laser beam and increase the exposure range.

[0093] The first coherent optical system 441 includes a first lens optical system 4431 and a first objective lens optical system 4441. The first lens optical system 4431 includes a third lens 4432 and a fourth lens 4433. The first objective lens optical system 4441 includes a fifth lens 4442 and a first objective lens 4443. The second coherent optical system 442 includes a second lens optical system 4434 and a second objective lens optical system 4444. The second lens optical system 4434 includes a sixth lens 4435 and a seventh lens 4436. The second objective lens optical system 4444 includes an eighth lens 4445 and a second objective lens 4446.

[0094] The laser in the first optical path is transmitted to the grating 401 to be modulated by passing through the first lens optical system 4431 and the first objective lens optical system 4441 in sequence; the laser in the second optical path is transmitted to the grating 401 to be modulated by passing through the second lens optical system 4434 and the second objective lens optical system 4444 in sequence, thereby performing interference superposition at the corresponding grating region of the grating 401 to be modulated.

[0095] It should be noted that, due to the large pixel size of the spatial light modulator and the small modulotable grating vector range, a moving platform 450 needs to be set in the grating fabrication apparatus 400 to increase the modulotable grating vector range. The moving platform 450 is used to carry the grating 401 to be modulated. Adjusting the position of the moving platform 450 can move the grating 401 to be modulated, so that the laser can sequentially irradiate different grating regions of the grating 401 to be modulated, and perform segmented exposure sequentially. During the process of the laser sequentially irradiating different grating regions of the grating 401 to be modulated, the phase modulation element 430 sequentially performs different phase modulations according to different grating regions, so that different grating regions have different diffraction efficiencies.

[0096] In related technologies, spatial light modulators are used to form exposure spots of different intensities on the grating to be modulated. Different regions have different exposure amounts, thereby controlling the diffraction efficiency of different regions of the volume holographic grating. However, due to the speckle effect in the intensity control of the spatial light modulator, the quality of the fabricated volume holographic grating is affected, which ultimately affects the image clarity of the near-eye display system.

[0097] In this embodiment, the phase modulation function of a spatial light modulator is used to sequentially perform different phase modulations on different grating regions of the grating 401 to be modulated, resulting in different diffraction efficiencies for different grating regions. This eliminates the influence of speckle on the quality of the fabricated partitioned grating, ensuring the image clarity of the near-eye display system 200.

[0098] Please see Figure 7In some embodiments, the phase modulation element 430 includes a diffractive optical element, a blazed grating, or a metasurface, and each coherent optical system 440 includes a lens optical system 443. Each laser beam is transmitted to the grating 401 to be modulated via the lens optical system 443. The laser beams simultaneously illuminate different grating regions of the grating 401 to achieve simultaneous zoned exposure. Each phase modulation element 430 is used to simultaneously perform phase modulation according to different grating regions of the grating 401.

[0099] Specifically, when any one of diffractive optical elements, blazed gratings, and metasurfaces is used as the phase modulation element 430, each coherent optical system 440 includes a lens optical system 443. The first coherent optical system 441 includes a first lens optical system 4431, and the second coherent optical system 442 includes a second lens optical system 4434.

[0100] The laser in the first optical path is transmitted to the grating 401 to be modulated through the first lens optical system 4431; the laser in the second optical path is transmitted to the grating 401 to be modulated through the second lens optical system 4434, thereby performing interference superposition at the corresponding grating region of the grating 401 to be modulated.

[0101] Because the pixel size of diffractive optical elements, blazed gratings, and metasurfaces is smaller than that of spatial light modulators, the modulated grating vector range is larger, and these elements can be partitioned. Therefore, when any one of these elements is used as the phase modulation element 430, the grating fabrication apparatus 400 does not require an objective lens optical system 444 and a moving platform 450. The laser can simultaneously irradiate different grating regions of the grating 401 to be modulated, allowing for simultaneous partitioned exposure. The phase modulation element 430 can simultaneously perform phase modulation according to different grating regions, resulting in different grating regions having different diffraction efficiencies.

[0102] Please see Figures 6 to 8 This application also provides a grating fabrication method. The grating fabrication method is applied to the grating fabrication apparatus 400 of any of the above embodiments. The grating fabrication method includes:

[0103] 010: Determine the grating vector distribution of the grating 401 to be modulated in different grating regions according to the predetermined optical design;

[0104] 020: Determine the grating phase distribution based on the grating vector distribution;

[0105] 030: Determine the phase of the two phase modulation elements 430 according to the grating phase distribution;

[0106] 040: Perform zoned exposure on the grating 401 to be modulated, and control the phase modulation element 430 to adjust the phase according to the different grating regions of the grating 401 to obtain a zoned grating.

[0107] In the grating fabrication method of this application, a partitioned grating is fabricated using phase modulation exposure. Two phase modulation elements 430 adjust the phase according to different grating regions of the grating 401 to be modulated, thereby obtaining a partitioned grating. This increases the degree of freedom in optical waveguide design, and the resulting optical waveguide structure 100 has better exit pupil uniformity and luminous efficiency.

[0108] Specifically, ignoring the effects of the coherent optical system 440 and the polarization beam splitter 420, the phases modulated by the two phase modulation elements 430 at position C of the grating 401 to be modulated can be expressed as follows:

[0109]

[0110] in, The phase modulated by the first phase modulation element 431 at position C of the grating 401 to be modulated. This represents the phase modulated by the second phase modulation element 432 at position C of the grating 401 to be modulated. X, Y, and Z are the X-axis, Y-axis, and Z-axis coordinates of position C, respectively. x1 k y1 and k z1 The laser beam wave vectors of the first optical path are respectively The components along the X, Y, and Z axes, k x2 k y2 and k z2 The laser beam wave vectors of the second optical path are respectively Components on the X, Y, and Z axes.

[0111] Hasaya and satisfy

[0112] The phase of the superposition of the interference of the two laser beams at position C is:

[0113]

[0114] Based on the relationship between the wave vector and the phase, the grating vector can be obtained. Satisfying the relation:

[0115]

[0116] grating vector Represented as:

[0117] K x =kx1 +k x2 (5)

[0118] K y =k y1 +k y2 (6)

[0119]

[0120] Among them, K x raster vector The component on the X-axis, K y For grating vectors The component on the Y-axis, K z For grating vectors The component on the Z-axis.

[0121] The predetermined optical design refers to the design of the optical waveguide structure 100, including the position of the grating 401 to be modulated 401 within the optical waveguide structure 100 and related exit pupil uniformity requirements. Based on the above process, during grating fabrication, the grating vector distribution of the grating 401 to be modulated 401 in different grating regions can be determined according to the predetermined optical design. As shown in equations (5), (6), and (7) above. It should be noted that in the design of the optical waveguide structure 100, each grating needs to ensure consistent periodicity along the plane of the waveguide substrate 10. Therefore, K needs to be kept constant. z As an adjustable variable of the grating 401 to be modulated.

[0122] After obtaining the grating vector distribution, the grating phase distribution can be determined based on equation (4) above. Based on equation (3) above, the phases of the two phase modulation elements 430 can be determined respectively based on the grating phase distribution. and As shown in equations (1) and (2) above.

[0123] After determining the phase of the two phase modulation elements 430, the grating 401 to be modulated is exposed in sections, and the phase modulation elements 430 are controlled to adjust the phase according to the different grating regions of the grating 401 to obtain the sectioned grating.

[0124] Please see Figure 6 and Figure 9 In some embodiments, the phase modulation element 430 includes a spatial light modulator. The grating fabrication apparatus 400 also includes a moving platform 450. Partition exposure of the grating 401 to be modulated and control of the phase modulation element 430 to adjust the phase according to different grating regions of the grating 401 to obtain a partitioned grating (i.e., 040) include:

[0125] 041: Based on the position of the grating 401 to be modulated in the waveguide substrate 10, the grating 401 to be modulated is moved by the moving platform 450 so that different grating regions of the grating 401 to be modulated are exposed in sequence, and the phase modulation element 430 is controlled to adjust the phase in sequence according to the different grating regions of the grating 401 to obtain the partitioned grating.

[0126] Specifically, when a spatial light modulator is used as the phase modulation element 430, due to the large pixel size of the spatial light modulator and the small modulated grating vector range, a moving platform 450 needs to be set in the grating fabrication apparatus 400 to increase the modulated grating vector range. Based on the position of the grating 401 to be modulated in the waveguide substrate 10, the position of the moving platform 450 is adjusted, causing the grating 401 to move. The laser can sequentially irradiate different grating regions of the grating 401, allowing for sequential exposure of different grating regions. During the sequential irradiation of different grating regions of the grating 401, the phase modulation element 430 sequentially performs different phase modulations according to different grating regions, obtaining partitioned gratings, thus resulting in different grating regions of the partitioned grating having different diffraction efficiencies.

[0127] In this embodiment, the phase modulation function of the spatial light modulator is utilized to sequentially perform different phase modulations on different grating regions of the grating 401 to be modulated, resulting in different diffraction efficiencies for different grating regions. This eliminates the influence of speckle on the quality of the fabricated partitioned gratings during the intensity control of the spatial light modulator, thereby ensuring the image clarity of the near-eye display system 200.

[0128] Please see Figure 7 and Figure 10 In some embodiments, the phase modulation element 430 includes a diffractive optical element, a blazed grating, or a metasurface. Partition exposure of the grating 401 to be modulated, and control of the phase modulation element 430 to adjust the phase according to different grating regions of the grating 401 to obtain a partitioned grating (i.e., 040), includes:

[0129] 042: Simultaneously expose different grating regions of the grating 401 to be modulated in separate sections, and control the phase modulation element 430 to adjust the phase according to the different grating regions of the grating 401 to be modulated in separate sections, so as to obtain a partitioned grating.

[0130] Specifically, when any one of diffractive optical elements, blazed gratings, and metasurfaces is used as the phase modulation element 430, the pixel size of these elements is smaller than that of spatial light modulators, resulting in a larger modulated grating vector range. Furthermore, these elements themselves can be partitioned. Therefore, when any one of these elements is used as the phase modulation element 430, the grating fabrication apparatus 400 does not require a moving platform 450. The laser can simultaneously irradiate different grating regions of the grating 401 to be modulated, performing partitioned exposure simultaneously. The phase modulation element 430 can simultaneously perform phase modulation according to different grating regions to obtain partitioned gratings, thus giving different grating regions of the partitioned grating different diffraction efficiencies.

[0131] In summary, in the waveguide structure 100, near-eye display system 200, head-mounted display device 300, grating fabrication apparatus 400, and grating fabrication method of this application, the coupling grating 40 employs a partitioned grating, where at least some of the grating regions in the partitioned grating have different grating vectors to control the Bragg shift of the incident light. This achieves diffraction efficiency control, improving the exit pupil uniformity of the waveguide structure 100 without affecting its field of view, and is also suitable for mass production.

[0132] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0133] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0134] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable storage medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, a computer-readable storage medium can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable storage medium could be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0135] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0136] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments. Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc.

[0137] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An optical waveguide structure, characterized in that, It includes a waveguide substrate and a coupling grating and a coupling grating disposed on the waveguide substrate. The coupling grating is used to couple incident light into the waveguide substrate, and the coupling grating is used to couple light from the waveguide substrate out of the waveguide substrate. The output grating is a partitioned grating, and the output grating is partitioned according to the first point of action of the light rays in the waveguide substrate on the output grating; The partitioned grating includes multiple grating regions, and at least some of the grating regions have different grating vectors.

2. The optical waveguide structure according to claim 1, characterized in that, The optical waveguide structure also includes a folding grating, which is used to fold the coupled-in light rays, and the coupling-out grating is used to couple the folded light rays out of the waveguide substrate; The folding grating is a partitioned grating, and the folding grating is partitioned according to the second point of action of the coupled light rays on the folding grating.

3. The optical waveguide structure according to claim 1 or 2, characterized in that, The differences in the grating vectors include: The directions of the grating vectors are different; and / or the amplitudes of the grating vectors are different.

4. The optical waveguide structure according to claim 3, characterized in that, In the partitioned grating, the grating vectors of the multiple grating regions have the same component in the waveguide substrate.

5. The optical waveguide structure according to claim 1 or 2, characterized in that, The multiple grating regions are in the shape of Thiessen polygons.

6. A near-eye display system, characterized in that, The near-eye display system includes the optical waveguide structure as described in any one of claims 1-5.

7. A head-mounted display device, characterized in that, The head-mounted display device includes the near-eye display system as described in claim 6.

8. A grating fabrication apparatus, characterized in that, The grating fabrication apparatus for fabricating the optical waveguide structure according to any one of claims 1-5 includes a laser, a polarization beam splitter, two phase modulation elements, and two sets of coherent optical systems. The laser is used to emit laser light; The polarization beam splitter is used to split the laser beam into two paths, which are then transmitted to the grating to be modulated for zoned exposure through the two sets of coherent optical systems respectively. The two phase modulation elements are used to perform phase modulation on the two laser beams according to different grating regions of the grating to be modulated; The two sets of coherent optical systems are used to interfere and superimpose the phases modulated by the two phase modulation elements at the corresponding grating regions of the grating to be modulated, so as to obtain the partitioned grating.

9. The grating fabrication apparatus according to claim 8, characterized in that, The phase modulation element includes one of a spatial light modulator, a diffractive optical element, a blazed grating, and a metasurface.

10. The grating fabrication apparatus according to claim 9, characterized in that, The phase modulation element includes a spatial light modulator, each coherent optical system includes a lens optical system and an objective lens optical system, and the grating fabrication device also includes a moving platform; Each laser beam is transmitted sequentially through the lens optical system and the objective lens optical system to the grating to be modulated; The mobile platform is used to carry the grating to be modulated and can drive the grating to be modulated to move so that the laser sequentially irradiates different grating areas of the grating to be modulated for sequential partitioned exposure. Each of the phase modulation elements is used to sequentially perform phase modulation according to different grating regions of the grating to be modulated.

11. The grating fabrication apparatus according to claim 9, characterized in that, The phase modulation element includes a diffractive optical element, a blazed grating, or a metasurface, and each set of coherent optical systems includes a lens optical system; Each laser beam is transmitted to the grating to be modulated via the lens optical system; The laser simultaneously illuminates different grating regions of the grating to be modulated to achieve simultaneous zoned exposure; Each of the phase modulation elements is used to simultaneously perform phase modulation according to different grating regions of the grating to be modulated.

12. A method for fabricating a grating, characterized in that, The grating fabrication apparatus according to any one of claims 8-11, wherein the grating fabrication method comprises: The grating vector distribution of the grating to be modulated in different grating regions is determined according to the predetermined optical design; The grating phase distribution is determined based on the grating vector distribution; The phases of the two phase modulation elements are determined according to the grating phase distribution; The grating to be modulated is exposed in sections, and the phase modulation element is controlled to adjust the phase according to different grating regions of the grating to be modulated, so as to obtain the sectioned grating.

13. The grating fabrication method according to claim 12, characterized in that, The phase modulation element includes a spatial light modulator, and the grating fabrication apparatus further includes a moving platform. The step of performing partitioned exposure on the grating to be modulated and controlling the phase modulation element to adjust the phase according to different grating regions of the grating to be modulated to obtain the partitioned grating includes: Based on the position of the grating to be modulated in the waveguide substrate, the moving platform drives the grating to be modulated to move, so that different grating regions of the grating to be modulated are exposed sequentially in sections, and the phase modulation element is controlled to adjust the phase sequentially according to the different grating regions of the grating to be modulated, so as to obtain the sectioned grating.

14. The grating fabrication method according to claim 12, characterized in that, The phase modulation element includes a diffractive optical element, a blazed grating, or a metasurface. The step of performing zoned exposure on the grating to be modulated and controlling the phase modulation element to adjust the phase according to different grating regions to obtain the zoned grating includes: The different grating regions of the grating to be modulated are simultaneously exposed in separate sections, and the phase modulation element is controlled to adjust the phase according to the different grating regions of the grating to be modulated, so as to obtain the partitioned grating.

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