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

Abstract

An optical waveguide structure (100), a near-eye display system (200), a head-mounted display device (300), a grating preparation apparatus (400), and a grating preparation method. The optical waveguide structure (100) comprises a waveguide substrate (10), and an in-coupling grating (20) and an out-coupling grating (40), which are arranged on the waveguide substrate (10), wherein the out-coupling grating (40) is a partitioned grating, the partitioned grating comprises a plurality of grating regions, and the grating vectors of at least some of the plurality of grating regions are different.

Description

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

[0001] Priority information

[0002] This application claims priority to and the benefit of patent application number 202411273885.2 filed with the China National Intellectual Property Office on September 11, 2024, and incorporates by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of optical waveguide, in particular to an optical waveguide structure, a near-eye display system, a head-mounted display device, a grating preparation device and a grating preparation method. BACKGROUND

[0004] Augment Reality (AR) is an important frontier of new generation information technology, which will profoundly change the way of human production and life. AR display technology based on optical waveguide can be mainly divided into three categories: array optical waveguide, surface relief optical waveguide and volume holographic optical waveguide. Among them, the volume holographic optical waveguide uses Bragg volume grating, which has strong wavelength and angle selectivity, so the volume holographic optical waveguide has weak rainbow stripes and low forward light leakage. At the same time, due to the advantage of low cost preparation, the volume holographic optical waveguide has become one of the most potential AR display technologies. However, the current holographic optical waveguide has poor exit pupil uniformity. SUMMARY

[0005] The present application provides an optical waveguide structure, a near-eye display system, a head-mounted display device, a grating preparation device and a grating preparation method to solve at least one of the above technical problems.

[0006] The optical waveguide structure of the present application comprises a waveguide substrate, a coupling-in grating and a coupling-out grating 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.

[0007] The coupling-out grating is a partitioned grating, and the coupling-out grating is partitioned according to a first action point of the light in the waveguide substrate on the coupling-out grating.

[0008] The partitioned grating comprises a plurality of grating regions, and the grating vectors of at least part of the grating regions are different.

[0009] The near-eye display system of the present application comprises the optical waveguide structure.

[0010] The head-mounted display device of the present application comprises the above-mentioned near-eye display system.

[0011] The grating preparation device of the embodiment of the application is used for preparing the optical waveguide structure, and the grating preparation device comprises a laser, a polarization beam splitter, two phase modulation elements and two sets of coherent optical systems;

[0012] The laser is used for emitting laser light;

[0013] The polarization beam splitter is used for splitting the laser light into two paths to be transmitted to a to-be-modulated grating for partition exposure by the two sets of coherent optical systems respectively;

[0014] The two phase modulation elements are used for respectively performing phase modulation on the two paths of the laser light according to different grating regions of the to-be-modulated grating;

[0015] The two sets of coherent optical systems are used for superimposing the phases modulated by the two phase modulation elements to interfere at corresponding grating regions of the to-be-modulated grating to obtain the partition grating.

[0016] The grating preparation method of the embodiment of the application is applied to the grating preparation device, and the grating preparation method comprises the following steps:

[0017] Determining grating vector distributions of different grating regions of the to-be-modulated grating according to a predetermined optical design;

[0018] Determining grating phase distributions according to the grating vector distributions;

[0019] Respectively determining phases of the two phase modulation elements according to the grating phase distributions;

[0020] Performing partition exposure on the to-be-modulated grating, and controlling the phase modulation elements to adjust the phases according to different grating regions of the to-be-modulated grating to obtain the partition grating.

[0021] In the optical waveguide structure, the near-eye display system, the head-mounted display device, the grating preparation device and the grating preparation method of the embodiment of the application, the coupling-out grating adopts the partition grating, grating vectors of at least part of the grating regions in the partition grating are different, so as to regulate the Bragg offset of the incident light. In this way, the diffraction efficiency is regulated, the exit pupil uniformity of the optical waveguide structure is improved, the field of view of the optical waveguide structure is not affected, and mass production is facilitated.

[0022] Additional aspects and advantages of the embodiments of the application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the following drawings of which:

[0024] FIG. 1 is a schematic diagram of an optical waveguide structure according to certain embodiments of the present application;

[0025] FIG. 2 is a schematic diagram of ray transmission of normal incidence light in an optical waveguide structure according to the related art;

[0026] FIG. 3 is a schematic diagram of ray transmission of non-normal incidence light in an optical waveguide structure according to the related art;

[0027] FIG. 4 is a schematic diagram of modules of a near-eye display system according to certain embodiments of the present application;

[0028] FIG. 5 is a schematic diagram of modules of a head-mounted display device according to certain embodiments of the present application;

[0029] FIG. 6 is a schematic diagram of a structure of a grating fabrication apparatus according to certain embodiments of the present application;

[0030] FIG. 7 is a schematic diagram of a structure of a grating fabrication apparatus according to certain embodiments of the present application;

[0031] FIG. 8 is a flowchart of a grating fabrication method according to certain embodiments of the present application;

[0032] FIG. 9 is a flowchart of a grating fabrication method according to certain embodiments of the present application;

[0033] FIG. 10 is a flowchart of a grating fabrication method according to certain embodiments of the present application.

[0034] Legend: optical waveguide structure 100, waveguide substrate 10, in-coupling grating 20, turning grating 30, out-coupling grating 40, near-eye display system 200, head-mounted display device 300, grating preparation device 400, grating to be modulated 401, laser 410, polarization beam splitter (first polarization beam splitter) 420, second polarization beam splitter 421, third polarization beam splitter 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, seventh lens 4436, objective optical system 444, first objective optical system 4441, fifth lens 4442, first objective 4443, second objective optical system 4444, eighth lens 4445, second objective 4446, moving platform 450, shutter 461, mirror 462, first mirror 4621, second 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 DESCRIPTION

[0035] Embodiments of the present application will be further described below with reference to the drawings. The same or similar reference numerals are used throughout the drawings to represent the same or similar elements or elements having the same or similar functions. In addition, the embodiments of the present application described below with reference to the drawings are exemplary and are for the purpose of explaining the embodiments of the present application, and cannot be understood as limiting the present application.

[0036] Referring to FIG. 1, an optical waveguide structure 100 is provided according to an embodiment of the present application. The optical waveguide structure 100 includes a waveguide substrate 10 and an in-coupling grating 20 and an out-coupling grating 40 disposed on the waveguide substrate 10. The in-coupling grating 20 is configured to couple an incident light into the waveguide substrate 10, and the out-coupling grating 40 is configured to couple the light in the waveguide substrate 10 out of the waveguide substrate 10. The out-coupling grating 40 is a zoned grating, and the out-coupling grating 40 is zoned according to a first action point of the light in the waveguide substrate 10 on the out-coupling grating 40. The zoned grating includes a plurality of grating regions, and grating vectors of at least some of the plurality of grating regions are different.

[0037] In the light waveguide structure 100 of the embodiments of the present application, the out-coupling grating 40 is a zoned grating, and the grating vectors of at least some of the grating regions of the zoned grating are different, so as to control the Bragg offset of the incident light. In this way, the diffraction efficiency is controlled, the pupil uniformity of the light waveguide structure 100 is improved, the field of view of the light waveguide structure 100 is not affected, and mass production is facilitated.

[0038] Specifically, the in-coupling grating 20 and the out-coupling grating 40 can be volume holographic gratings. The transmission path of the light in the light waveguide structure 100 is as follows: the light emitted by the image source passes through the collimation system and reaches the light waveguide structure 100, is coupled into the waveguide substrate 10 from the in-coupling grating 20, and is coupled out of the waveguide substrate 10 from the out-coupling grating 40 in the waveguide substrate 10, so that the pupil expansion can be achieved.

[0039] The out-coupling grating 40 can be a zoned grating, and the surface of each zoned grating is divided into a plurality of grating regions. The division of the grating regions is related to the point of action of the light on the grating. For the out-coupling grating 40, the first point of action of the light in the waveguide substrate 10 on the out-coupling grating 40 can be used for zoning. The specific process is as follows: by tracing the incident light of different angles, the positions of the in-coupled light on the out-coupling grating 40 are the first points of action, as shown by point A in FIG. 1. According to the first points of action, the out-coupling grating 40 can be zoned to form a zoned grating, and each grating region includes a first point of action.

[0040] It should be noted that the number of grating regions is not limited, and can be 3, 4, 5 or more. The grating vectors of at least some of the plurality of grating regions are different, that is, the grating vectors of the plurality of grating regions can all be different, or some can be the same and some can be different.

[0041] In the related art, in order to improve the pupil uniformity of the light waveguide, the diffraction efficiency of the grating in the light waveguide is controlled by zoning. As shown in FIG. 2, the out-coupling grating is divided into three regions R1, R2 and R3, and the diffraction efficiencies of the three regions are the same. At this time, the intensity of the out-coupled light gradually decreases from left to right, and the pupil uniformity is poor. As shown in FIG. 3, the diffraction efficiencies of the three regions are set to 33%, 50% and 100% from left to right, respectively. At this time, the pupil uniformity of the normally incident light is best. However, for non-normally incident light, the number of actions with the three regions of the out-coupling grating is different, and the pupil becomes non-uniform.

[0042] It is found through research that the diffraction efficiency of the grating is mainly determined by two parts, one part is the thickness and refractive index modulation of the grating, and the other part is the Bragg offset of the incident light. In the related art, the diffraction efficiency of the grating is controlled by adjusting the thickness and refractive index modulation of the grating, but the refractive index modulation of different positions of the grating will affect the field angle of the optical waveguide structure, and the thickness control of the grating will increase the difficulty of mass production.

[0043] In the embodiments of the present application, the out-coupling grating 40 adopts a zoned grating. Compared with dividing the out-coupling grating 40 into three regions, the zoned grating can be divided into more regions. The grating vectors of at least some of the multiple grating regions of the zoned grating are different. By adjusting the grating vectors of different grating regions, the Bragg offset of the incident light is adjusted. In this way, the diffraction efficiency is adjusted, the pupil uniformity of the optical waveguide structure 100 is improved, compared with adjusting the refractive index modulation, the field angle of the optical waveguide structure 100 is not affected; compared with controlling the grating thickness, it is convenient for mass production.

[0044] Please refer to FIG. 1. In some embodiments, the optical waveguide structure 100 further includes a turning grating 30. The turning grating 30 is used to turn the in-coupled light, and the out-coupling grating 40 is used to couple the turned light out of the waveguide substrate 10. The turning grating 30 is a zoned grating, and the turning grating 30 is divided into zones according to the first action point of the in-coupled light on the turning grating 30.

[0045] Specifically, the optical waveguide structure 100 further includes a turning grating 30, and the turning grating 30 can be a volume holographic grating. After the incident light is coupled into the waveguide substrate 10 from the in-coupling grating 20, the turning grating 30 is used to turn the in-coupled light, at this time, the out-coupling grating 40 is used to couple the turned light out of the waveguide substrate 10, so that two-dimensional pupil expansion can be achieved. The turning grating 30 can also adopt a zoned grating.

[0046] The zoned process is as follows: by tracing different angles of incident light, after the multi-angle incident light is coupled into the waveguide substrate 10, the position of the in-coupled light acting on the turning grating 30 is the second action point, as shown by point B in FIG. 1. According to the first action point, the turning grating 30 can be divided into zones to form a zoned grating, and each grating region includes a second action point.

[0047] In this case, the in-coupled light is turned by the turning grating 30, and the position of the turned light acting on the out-coupling grating 40 is the first action point, as shown by point A in FIG. 1. According to the first action point, the out-coupling grating 40 can be divided into zones to form a zoned grating, and each grating region includes a first action point. In this way, based on the positions of the incident light of different angles interacting with the grating, the pupil uniformity of the optical waveguide structure 100 can be improved.

[0048] In the embodiments of the present application, the coupling-out grating 40 and the turning grating 30 are both partitioned gratings, and the grating vectors of at least some of the grating regions of the partitioned gratings are different, so as to control the Bragg offset of the incident light. In this way, the diffraction efficiency is further controlled, the pupil uniformity of the optical waveguide structure 100 is improved, the field of view of the optical waveguide structure 100 is not affected, and mass production is facilitated.

[0049] In some embodiments, the grating vectors can be different in direction, different in amplitude, or different in both direction and amplitude. The specific cases of different grating vectors are not limited herein.

[0050] In some embodiments, the grating vectors can be different in direction and / or amplitude, but the components of the grating vectors in the waveguide substrate 10 are the same. The components being the same means that the projections of the grating vectors on the surface of the waveguide substrate 10 are the same. It should be noted that in the same partitioned grating, the components of the grating vectors of the multiple grating regions in the waveguide substrate 10 are the same; in different partitioned gratings, the components of the grating vectors in the waveguide substrate 10 can be different. For example, the components of the grating vectors in the coupling-out grating 40 in the waveguide substrate 10 can be different from the components of the grating vectors in the turning grating 30 in the waveguide substrate 10. In this way, the diffraction distances of the multiple grating regions of the same partitioned grating can be ensured to be the same, the diffraction efficiency of the light incident at the same angle on different grating regions can be controlled, the pupil uniformity of the optical waveguide structure 100 is improved, the field of view of the optical waveguide structure 100 is not affected, and mass production is facilitated.

[0051] Referring to FIG. 1, in some embodiments, the multiple grating regions form a Voronoi polygon.

[0052] Specifically, the Voronoi polygon is a set of continuous polygons, each polygon includes only one control point, and the distance from any point in the polygon to the control point of the polygon is less than the distance to the control points of other polygons. For the partitioned grating corresponding to the turning grating 30, the second action point is the control point, the perpendicular bisectors of the lines connecting adjacent two second action points are drawn, and all the perpendicular bisectors are connected, thereby forming a Voronoi polygon, and each polygon is a grating region.

[0053] Similarly, for the partitioned grating corresponding to the coupling-out grating 40, the first action point is the control point, the perpendicular bisectors of the lines connecting adjacent two first action points are drawn, and all the perpendicular bisectors are connected, thereby forming a Voronoi polygon, and each polygon is a grating region.

[0054] Then, according to the partition result, the grating vectors of each grating region are adjusted to obtain a partitioned grating, so as to realize the regulation of the Bragg shift of the incident light. The specific process of grating vector adjustment is as follows: the grating vector includes a first component along the plane direction of the waveguide substrate 10 and a second component along the thickness direction of the waveguide substrate 10, the first component of each grating region is kept consistent, and the second component is set differently, so that the multiple grating regions have different grating vectors.

[0055] The grating regions divided by the Voronoi diagram can optimize the distribution of the grating and will not affect the field of view angle of the optical waveguide structure 100. By adjusting the grating vectors of each grating region, the light energy distribution in different field of view angles can be accurately controlled, so as to improve the pupil uniformity of the optical waveguide structure 100.

[0056] Please refer to FIG. 1 and FIG. 4, the embodiment of the present application further provides a near-eye display system 200, which comprises the optical waveguide structure 100 of any of the above embodiments. In addition, the near-eye display system 200 can further comprise an image source and a collimation system, and the light emitted by the image source is at least partially input to the optical waveguide structure 100 through the collimation system.

[0057] Please refer to FIG. 5, the embodiment of the present application further provides a head-mounted display device 300, which comprises the near-eye display system 200 described above. The head-mounted display device 300 is, for example, an augmented head-mounted display device.

[0058] Please refer to FIG. 1, FIG. 6 and FIG. 7, the embodiment of the present application further provides a grating preparation device 400. The grating preparation device 400 is used for preparing the optical waveguide structure 100 of any of the above embodiments. The grating preparation device 400 comprises 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 for emitting laser. The polarization beam splitter 420 is used for splitting the laser into two paths to be transmitted to a to-be-modulated grating 401 for partitioned exposure through the two sets of coherent optical systems 440. The two phase modulation elements 430 are used for respectively modulating the phases of the two paths of laser according to different grating regions of the to-be-modulated grating 401. The two sets of coherent optical systems 440 are used for superimposing the phases modulated by the two phase modulation elements 430 at the corresponding grating regions of the to-be-modulated grating 401 to obtain a partitioned grating.

[0059] In the grating preparation device 400 of the embodiment of the present application, the sub-region grating is prepared by using the phase modulation exposure method. Two phase modulation elements 430 modulate the phases of two laser beams according to different grating regions of the to-be-modulated grating 401. The phases modulated by the two phase modulation elements 430 pass through corresponding coherent optical systems 440 and are superimposed by interference at corresponding grating regions of the to-be-modulated grating 401, so as to obtain the sub-region grating. In this way, the degree of freedom of the optical waveguide design is improved, and the exit pupil uniformity and light efficiency of the obtained optical waveguide structure 100 are better.

[0060] Specifically, the to-be-modulated grating 401 in the optical waveguide structure 100 (i.e., the pre-modulation turning grating 30 or the out-coupling grating 40) is arranged between the two sets of coherent optical systems 440. The laser 410 emits laser beams, which are split into two beams by the polarization beam splitter 420. The two laser beams are transmitted to the to-be-modulated grating 401 through the two sets of coherent optical systems 440, so as to perform double-beam sub-region exposure on the to-be-modulated grating 401.

[0061] The two phase modulation elements 430 are arranged between the polarization beam splitter 420 and the light paths of the corresponding coherent optical systems 440. The phase modulation elements 430 can modulate the phases of the two laser beams according to different grating regions of the to-be-modulated grating 401, so that at least part of the grating regions in the plurality of grating regions have different grating vectors. The coherent optical system 440 is used to superimpose the phases modulated by the corresponding phase modulation element 430 by interference at the corresponding grating region of the to-be-modulated grating 401, so as to obtain the sub-region grating.

[0062] The grating vectors corresponding to different grating regions are different. Therefore, when performing exposure preparation, the phase needs to be adjusted according to the grating vector that the current to-be-exposed region desires to have, so that the coherent optical system 440 can superimpose the phases by interference at the to-be-exposed region according to the adjusted phase, thereby exposing the grating vector.

[0063] In the related art, it is difficult to control the diffraction efficiency of each region with high degree of freedom in the preparation process of the grating, resulting in poor exit pupil uniformity of the optical waveguide structure. In the embodiment of the present application, the sub-region grating is prepared by using the phase modulation exposure method. Two phase modulation elements 430 modulate the phases of two laser beams according to different grating regions of the to-be-modulated grating 401, and the degree of freedom of phase modulation is high. The phases modulated by the two phase modulation elements 430 pass through corresponding coherent optical systems 440 and are superimposed by interference at corresponding grating regions of the to-be-modulated grating 401, so as to obtain the sub-region grating. Different grating regions in the sub-region grating have different diffraction efficiencies. In this way, the degree of freedom of the optical waveguide design is improved, and the exit pupil uniformity and light efficiency of the obtained optical waveguide structure 100 are better.

[0064] In some embodiments, in addition to the polarization beam splitter 420 (hereinafter referred to as the first polarization beam splitter 420), the grating preparation device 400 can further include a second polarization beam splitter 421 and a third polarization beam splitter 422. The first polarization beam splitter 420 is used to split the laser emitted by the laser 410 into two paths, i.e., a first optical path (e.g., the left optical path in FIGS. 6 and 7) and a second optical path (e.g., the right optical path in FIGS. 6 and 7). 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.

[0065] The second polarization beam splitter 421 is arranged on the first optical path between the first phase modulation element 431 and the first coherent optical system 441. The third polarization beam splitter 422 is arranged on the second optical path 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 to the phase modulation element 430 for phase modulation, and then transmit the phase-modulated laser to the coherent optical system 440.

[0066] In some embodiments, the grating preparation device 400 further includes a shutter 461, a mirror 462, and a half-wave plate 463. The shutter 461 is arranged between the laser 410 and the first polarization beam splitter 420, and is used to control the time of laser emission, thereby controlling the time of exposure to the grating to be modulated 401. The mirror 462 is used to turn the laser path. In one example, the grating preparation device 400 includes two mirrors 462, i.e., a first mirror 4621 and a second mirror 4622. The first mirror 4621 is arranged between the shutter 461 and the first polarization beam splitter 420, and the second mirror 4622 is arranged between the first polarization beam splitter 420 and the second polarization beam splitter 421.

[0067] The half-wave plate 463 is used to adjust the polarization state of the laser. The half-wave plate 463 can cooperate with the polarization beam splitter 420 to control the energy ratio of the two paths of the split laser. In one example, the grating preparation device 400 includes four half-wave plates 463, i.e., 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 arranged between the first mirror 4621 and the first polarization beam splitter 420, the second half-wave plate 4632 is arranged between the first polarization beam splitter 420 and the second mirror 4622, the third half-wave plate 4633 is arranged between the second mirror 4622 and the second polarization beam splitter 421, and the fourth half-wave plate 4634 is arranged between the first polarization beam splitter 420 and the third polarization beam splitter 422.

[0068] In some embodiments, the grating preparation device 400 further comprises spatial filters 464, lenses 465 and aperture stops 466. The number of the spatial filters 464, the lenses 465 and the aperture stops 466 is two, which are respectively arranged in the first light path and the second light path. The spatial filters 464 comprise a first spatial filter 4641 and a second spatial filter 4642, the first spatial filter 4641 is arranged between the second mirror 4622 and the third half-wave plate 4633, and the second spatial filter 4642 is arranged between the first polarization beam splitter 420 and the fourth half-wave plate 4634, for removing high-order modes and noise in the laser beam.

[0069] The lenses 465 comprise a first lens 4651 and a second lens 4652, the first lens 4651 is arranged between the first spatial filter 4641 and the third half-wave plate 4633, and the second lens 4652 is arranged between the second spatial filter 4642 and the fourth half-wave plate 4634. The aperture stops 466 comprise a first aperture stop 4661 and a second aperture stop 4662, the first aperture stop 4661 is arranged in the first coherent optical system 441, and the second aperture stop 4662 is arranged in the second coherent optical system 442, for optically filtering the laser beam.

[0070] Referring to FIGS. 6 and 7, in some embodiments, the phase modulation element 430 comprises one of a spatial light modulator, a diffractive optical element, a blazed grating and a metasurface.

[0071] Specifically, the spatial light modulator, the diffractive optical element, the blazed grating and the metasurface can all modulate the phase of the laser beam, and one of them can be used as the phase modulation element 430. For example, the spatial light modulator can be used as the phase modulation element 430; or the diffractive optical element can be used as the phase modulation element 430; or the blazed grating can be used as the phase modulation element 430; or the metasurface can be used as the phase modulation element 430.

[0072] Referring to FIG. 6, in some embodiments, the phase modulation element 430 comprises a spatial light modulator. Each set of coherent optical system 440 comprises a lens optical system 443 and an objective optical system 444. The grating preparation device 400 further comprises a moving platform 450. Each laser is transmitted to the grating to be modulated 401 in turn through the lens optical system 443 and the objective optical system 444. The moving platform 450 is used to carry the grating to be modulated 401 and can drive the grating to be modulated 401 to move, so that the laser is irradiated on different grating regions of the grating to be modulated 401 in turn for exposure in different regions. Each phase modulation element 430 is used to modulate the phase according to different grating regions of the grating to be modulated 401 in turn.

[0073] Specifically, when the spatial light modulator is used as the phase modulation element 430, each set of coherent optical systems 440 includes a lens optical system 443 and an objective optical system 444, and the lens optical system 443 and the objective optical system 444 can be 4f optical systems, that is, each set of coherent optical systems includes two 4f optical systems, and the 4f optical systems have the effect of optical filtering.

[0074] The lens optical system 443 includes two lenses, and the objective optical system 444 includes one lens and one objective lens. The above-mentioned aperture stop 466 can be arranged in the lens optical system 443, and the lens optical system 443 combines the aperture stop 466 to perform optical filtering on the laser beam. The objective optical system 444 is used to reduce the spot radius of the laser beam and increase the exposure range.

[0075] The first coherent optical system 441 includes a first lens optical system 4431 and a first objective optical system 4441, the first lens optical system 4431 includes a third lens 4432 and a fourth lens 4433, and the first objective 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 optical system 4444, the second lens optical system 4434 includes a sixth lens 4435 and a seventh lens 4436, and the second objective optical system 4444 includes an eighth lens 4445 and a second objective lens 4446.

[0076] The laser of the first light path is transmitted to the to-be-modulated grating 401 through the first lens optical system 4431 and the first objective optical system 4441 in sequence; and the laser of the second light path is transmitted to the to-be-modulated grating 401 through the second lens optical system 4434 and the second objective optical system 4444 in sequence, so as to interfere and superimpose at the corresponding grating area of the to-be-modulated grating 401.

[0077] It should be noted that, since the pixel size of the spatial light modulator is large, the range of modulatable grating vectors is small, and the moving platform 450 needs to be arranged in the grating preparation device 400 to improve the range of modulatable grating vectors. The moving platform 450 is used to carry the to-be-modulated grating 401, and adjusting the position of the moving platform 450 can drive the to-be-modulated grating 401 to move, so that the laser can irradiate different grating areas of the to-be-modulated grating 401 in sequence, and the exposure is performed in sequence. In the process of the laser irradiating different grating areas of the to-be-modulated grating 401 in sequence, the phase modulation element 430 modulates the phase in sequence according to different grating areas, so that different grating areas have different diffraction efficiencies.

[0078] In the related art, different exposure spots with different light intensities are formed on a to-be-modulated grating by using a spatial light modulator, the exposure amounts of different regions are different, and thus the diffraction efficiency of different regions of the volume holographic grating is controlled. However, due to the speckle of the intensity control of the spatial light modulator, the quality of the volume holographic grating manufactured is affected, and finally the picture clarity of the near-eye display system is affected.

[0079] In the embodiments of the present application, the phase modulation function of the spatial light modulator is used, different phase modulations are performed according to different grating regions of the to-be-modulated grating 401 in sequence, so that different grating regions have different diffraction efficiencies. In this way, the influence of speckle on the quality of the manufactured partitioned grating can be eliminated, and the picture clarity of the near-eye display system 200 can be ensured.

[0080] Please refer to FIG. 7. In 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 is transmitted to the to-be-modulated grating 401 through the lens optical system 443. The lasers irradiate different grating regions of the to-be-modulated grating 401 at the same time to perform simultaneous partitioned exposure. Each phase modulation element 430 is used to perform phase modulation according to different grating regions of the to-be-modulated grating 401 at the same time.

[0081] Specifically, when any one of the diffractive optical element, the blazed grating, and the metasurface is used as the phase modulation element 430, each coherent optical system 440 includes one 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.

[0082] The laser of the first light path is transmitted to the to-be-modulated grating 401 through the first lens optical system 4431; and the laser of the second light path is transmitted to the to-be-modulated grating 401 through the second lens optical system 4434, so as to perform interference superposition at the corresponding grating region of the to-be-modulated grating 401.

[0083] Since the pixel size of the diffractive optical element, the blazed grating, and the metasurface is smaller than that of the spatial light modulator, the modulatable grating vector range is larger, and the diffractive optical element, the blazed grating, and the metasurface can be partitioned; therefore, when any one of the diffractive optical element, the blazed grating, and the metasurface is used as the phase modulation element 430, the grating manufacturing device 400 does not need to be provided with the objective optical system 444 and the moving platform 450. The lasers can irradiate different grating regions of the to-be-modulated grating 401 at the same time to perform simultaneous partitioned exposure. The phase modulation element 430 can perform phase modulation according to different grating regions at the same time, so that different grating regions have different diffraction efficiencies.

[0084] Referring to FIGS. 6-8, the embodiment of the present application further provides a grating preparation method. The grating preparation method is applied to the grating preparation device 400 of any of the above embodiments. The grating preparation method comprises:

[0085] 010: determining a grating vector distribution of the to-be-modulated grating 401 at different grating regions according to a predetermined optical design;

[0086] 020: determining a grating phase distribution according to the grating vector distribution;

[0087] 030: respectively determining phases of the two phase modulation elements 430 according to the grating phase distribution;

[0088] 040: performing partition exposure on the to-be-modulated grating 401, and controlling the phase modulation elements 430 to adjust the phases according to different grating regions of the to-be-modulated grating 401, so as to obtain a partition grating.

[0089] In the grating preparation method of the embodiment of the present application, the partition grating is prepared by using the phase modulation exposure mode, and the two phase modulation elements 430 adjust the phases according to different grating regions of the to-be-modulated grating 401, so as to obtain the partition grating. In this way, the degree of freedom of the optical waveguide design is improved, and the exit pupil uniformity and light efficiency of the obtained optical waveguide structure 100 are better.

[0090] Specifically, ignoring the influence of the coherent optical system 440 and the polarization beam splitter 420, the phases modulated by the two phase modulation elements 430 at the position C of the to-be-modulated grating 401 can be respectively represented as:

[0091] wherein, is the phase modulated by the first phase modulation element 431 at the position C of the to-be-modulated grating 401, is the phase modulated by the second phase modulation element 432 at the position C of the to-be-modulated grating 401. X, Y, and Z are X-axis, Y-axis, and Z-axis coordinates of the position C, respectively. x1 , k y1 , and k z1 are components of the laser beam wave vector of the first light path on the X-axis, Y-axis, and Z-axis, respectively, x2 , k y2 , and k z2 are components of the laser beam wave vector of the second light path on the X-axis, Y-axis, and Z-axis, respectively. The wave vectors and satisfy

[0092] The phase of the interference superposition of the two laser beams at the position C is:

[0093] According to the relationship between the wave vector and the phase, the grating vector K can be obtained The relationship is satisfied:

[0094] The grating vector K is expressed as: K x = k x1 + k x2 (5) K y = k y1 + k y2 (6)

[0095] wherein K x is the component of the grating vector K in the X-axis, K y is the component of the grating vector K in the Y-axis, and K z is the component of the grating vector K in the Z-axis.

[0096] The predetermined optical design refers to the design of the optical waveguide structure 100, including the position of the to-be-modulated grating 401 in the optical waveguide structure 100 and the related exit pupil uniformity requirements, etc. Based on the above process, when the grating is prepared, the grating vector distribution of the to-be-modulated grating 401 in different grating regions can be determined according to the predetermined optical design, and the grating vector K is shown in the above formula (5), (6), and (7). It should be noted that in the design of the optical waveguide structure 100, the period along the waveguide substrate 10 plane needs to be consistent for each grating, therefore, needs to be kept constant, and K z is taken as the adjustable variable of the to-be-modulated grating 401.

[0097] After obtaining the grating vector distribution, the grating phase distribution can be determined according to the grating vector distribution based on the above formula (4). Based on the above formula (3), the phases of the two phase modulation elements 430 can be determined according to the grating phase distribution, respectively. and are shown in the above formula (1) and (2).

[0098] After determining the phases of the two phase modulation elements 430, the to-be-modulated grating 401 is exposed in sections, and the phase modulation elements 430 are controlled to adjust the phases according to the different grating regions of the to-be-modulated grating 401, so as to obtain a sectional grating.

[0099] Referring to FIGS. 6 and 9, in some embodiments, the phase modulation element 430 includes a spatial light modulator. The grating preparation device 400 further includes a moving platform 450. The to-be-modulated grating 401 is exposed in a partitioned manner, and the phase modulation element 430 is controlled to adjust the phase according to different grating regions of the to-be-modulated grating 401, so as to obtain a partitioned grating (i.e., 040), including:

[0100] 041: According to the position of the to-be-modulated grating 401 in the waveguide substrate 10, the to-be-modulated grating 401 is moved by the moving platform 450, so that different grating regions of the to-be-modulated grating 401 are exposed in a partitioned manner, and the phase modulation element 430 is controlled to adjust the phase according to different grating regions of the to-be-modulated grating 401, so as to obtain a partitioned grating.

[0101] Specifically, when the spatial light modulator is used as the phase modulation element 430, because the pixel size of the spatial light modulator is large, the range of modulatable grating vectors is small, and therefore the moving platform 450 needs to be arranged in the grating preparation device 400 to increase the range of modulatable grating vectors. According to the position of the to-be-modulated grating 401 in the waveguide substrate 10, the position of the moving platform 450 is adjusted to move the to-be-modulated grating 401, so that the laser can irradiate different grating regions of the to-be-modulated grating 401 in sequence, so that different grating regions are exposed in a partitioned manner. During the process in which the laser irradiates different grating regions of the to-be-modulated grating 401 in sequence, the phase modulation element 430 adjusts the phase according to different grating regions in sequence, so as to obtain a partitioned grating, so that different grating regions of the partitioned grating have different diffraction efficiencies.

[0102] In the embodiments of the present application, the phase modulation function of the spatial light modulator is used to adjust the phase according to different grating regions of the to-be-modulated grating 401 in sequence, so that different grating regions have different diffraction efficiencies. In this way, the influence of speckle on the quality of the prepared partitioned grating in the intensity control of the spatial light modulator can be eliminated, so as to ensure the picture clarity of the near-eye display system 200.

[0103] Referring to FIGS. 7 and 10, in some embodiments, the phase modulation element 430 includes a diffractive optical element, a blazed grating, or a metasurface. The to-be-modulated grating 401 is exposed in a partitioned manner, and the phase modulation element 430 is controlled to adjust the phase according to different grating regions of the to-be-modulated grating 401, so as to obtain a partitioned grating (i.e., 040), including:

[0104] 042: Different grating regions of the to-be-modulated grating 401 are exposed in a partitioned manner at the same time, and the phase modulation element 430 is controlled to adjust the phase according to different grating regions of the to-be-modulated grating 401, so as to obtain a partitioned grating.

[0105] Specifically, when any one of the diffractive optical element, the blazed grating and the metasurface is adopted as the phase modulation element 430, due to the smaller pixel size of the diffractive optical element, the blazed grating and the metasurface compared with the spatial light modulator, the modulated grating vector range is larger, and the diffractive optical element, the blazed grating and the metasurface can be partitioned by itself; therefore, when any one of the diffractive optical element, the blazed grating and the metasurface is adopted as the phase modulation element 430, the grating preparation device 400 does not need to be provided with the moving platform 450. The laser can irradiate on different grating regions of the to-be-modulated grating 401 at the same time, and the partitioned exposure is performed at the same time. The phase modulation element 430 can perform phase modulation according to different grating regions at the same time, and the partitioned grating is obtained, so that different grating regions of the partitioned grating have different diffraction efficiencies.

[0106] In summary, in the optical waveguide structure 100, the near-eye display system 200, the head-mounted display device 300, the grating preparation device 400 and the grating preparation method of the embodiments of the present application, the coupling-out grating 40 adopts the partitioned grating, the grating vectors of at least part of the grating regions in the partitioned grating are different, so as to control the Bragg offset of the incident light. In this way, the diffraction efficiency is controlled, the exit pupil uniformity of the optical waveguide structure 100 is improved, the field of view of the optical waveguide structure 100 is not affected, and mass production is facilitated.

[0107] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the different embodiments or examples described in the present specification and the features of the different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0108] Any process or method descriptions in flow charts or described elsewhere herein can be understood as representing code modules, segments, or portions of code which include one or more executable instructions for performing specific logic functions or steps in the process. The various embodiments of the application can include additional or fewer steps or processes in addition to or other than those of the specific embodiments described herein, and the order of the steps can be changed from the order described.

[0109] The logic and / or steps represented in the flow diagrams and / or described herein, for example, can be considered as a sequence of executable instructions, and can be embodied in any computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor- containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this specification, a computer-readable storage medium can be any tangible means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable storage medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable storage medium include the following: an electrical connection having one or more wires (electronic), a portable computer diskette (magnetic), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber (optical), and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable storage medium can even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, for example via an optical scanner, then compiled, interpreted, or otherwise processed, and stored in a computer memory in a form that can be later executed by the computer. In the context of this specification, a computer-readable storage medium can be any tangible means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable storage medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable storage medium include the following: an electrical connection having one or more wires (electronic), a portable computer diskette (magnetic), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber (optical), and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable storage medium can even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, for example via an optical scanner, then compiled, interpreted, or otherwise processed, and stored in a computer memory in a form that can be later executed by the computer.

[0110] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the above embodiments, various steps or methods can be implemented in software or firmware that is stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any of the following technologies, known in the art, or combinations thereof, can be used: a discrete logic circuit having logic gates for implementing logic functions upon data signals, an application specific integrated circuit having appropriate combinational logic gates, a programmable gate array (PGA), a field programmable gate array (FPGA), and / or the like.

[0111] Those skilled in the art of the present technology can understand that all or part of the steps carried out by the above-mentioned embodiment methods can be completed by programs instructing related hardware, and the programs can be stored in a computer readable storage medium. When the program is executed, it includes one of the steps of the method embodiment or a combination thereof. In addition, each functional unit in each embodiment of the present application can be integrated in one processing module, or each unit can exist physically alone, or two or more units can be integrated in one module. The above-mentioned integrated module can be realized in the form of hardware or in the form of software function module. The integrated module, if realized in the form of software function module and sold or used as an independent product, can also be stored in a computer readable storage medium. The above-mentioned storage medium can be a read-only memory, a magnetic disk or an optical disk, etc.

[0112] Although the embodiments of the present application have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application. Those skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. An optical waveguide structure, wherein, The light waveguide structure comprises a waveguide substrate and an in-coupling grating and an out-coupling grating arranged on the waveguide substrate, the in-coupling grating is used for coupling incident light into the waveguide substrate, and the out-coupling grating is used for coupling light in the waveguide substrate out of the waveguide substrate; The out-coupling grating is a zoned grating, and the out-coupling grating is zoned according to a first action point of the light in the waveguide substrate on the out-coupling grating. The zoned grating comprises a plurality of grating regions, and grating vectors of at least some of the grating regions are different.

2. The optical waveguide structure of claim 1, wherein, The light waveguide structure further comprises a turning grating, the turning grating is used for turning the in-coupled light, and the out-coupling grating is used for coupling the turned light out of the waveguide substrate. The turning grating is a zoned grating, and the turning grating is zoned according to a second action point of the in-coupled light on the turning grating.

3. The optical waveguide structure of claim 1 or 2, wherein, The grating vectors are different in that: The directions of the grating vectors are different, and / or the amplitudes of the grating vectors are different.

4. The optical waveguide structure of claim 3, wherein, In the zoned grating, components of the grating vectors of the plurality of grating regions in the waveguide substrate are the same.

5. The optical waveguide structure of claim 1 or 2, wherein, The plurality of grating regions form a Voronoi polygon.

6. A near-eye display system, wherein, The near-eye display system comprises the light waveguide structure of any one of claims 1-5.

7. A head-mounted display device, wherein, The head-mounted display device comprises the near-eye display system of claim 6.

8. An apparatus for grating fabrication, wherein, The grating preparation device comprises a laser, a polarization beam splitter, two phase modulation elements, and two sets of coherent optical systems, and is used for preparing the light waveguide structure of any one of claims 1-5. The laser is used for emitting laser light. The polarization beam splitter is used for splitting the laser light into two paths to be transmitted to a to-be-modulated grating for zoned exposure by the two sets of coherent optical systems, respectively. The two phase modulation elements are used for respectively performing phase modulation on the two paths of the laser light according to different grating regions of the to-be-modulated grating. The two sets of coherent optical systems are used for interfering and superimposing phases modulated by the two phase modulation elements at corresponding grating regions of the to-be-modulated grating to obtain the zoned grating.

9. The grating fabrication apparatus of claim 8, wherein, The phase modulation element comprises one of a spatial light modulator, a diffractive optical element, a blazed grating, and a metasurface.

10. The grating fabrication apparatus of claim 9, wherein, The phase modulation element comprises a spatial light modulator, each set of the coherent optical systems comprises a lens optical system and an objective optical system, and the grating preparation device further comprises a moving platform. Each path of the laser light is sequentially transmitted to the to-be-modulated grating through the lens optical system and the objective optical system. The moving platform is used for carrying the to-be-modulated grating and can move the to-be-modulated grating to enable the laser light to sequentially irradiate different grating regions of the to-be-modulated grating for zoned exposure. Each phase modulation element is used for sequentially performing phase modulation according to different grating regions of the to-be-modulated grating.

11. The grating fabrication apparatus of claim 9, wherein, The phase modulation element comprises a diffractive optical element, a blazed grating, or a metasurface, and each set of the coherent optical systems comprises a lens optical system. Each path of the laser light is transmitted to the to-be-modulated grating through the lens optical system. The laser light simultaneously irradiates different grating regions of the to-be-modulated grating for zoned exposure. Each of the phase modulation elements is configured to simultaneously perform phase modulation according to different grating regions of the to-be-modulated grating.

12. A method of making an optical grating, wherein, The grating preparation method comprises: determining grating vector distribution of the to-be-modulated grating in different grating regions according to a predetermined optical design; determining grating phase distribution according to the grating vector distribution; determining phases of the two phase modulation elements respectively according to the grating phase distribution; performing zoned exposure on the to-be-modulated grating, and adjusting phases of the phase modulation elements according to different grating regions of the to-be-modulated grating to obtain the zoned grating.

13. The method of claim 12, wherein, The phase modulation elements comprise a spatial light modulator, and the grating preparation device further comprises a moving platform, and the performing zoned exposure on the to-be-modulated grating and adjusting phases of the phase modulation elements according to different grating regions of the to-be-modulated grating to obtain the zoned grating comprises: moving the to-be-modulated grating by the moving platform according to a position of the to-be-modulated grating in the waveguide substrate, so that different grating regions of the to-be-modulated grating are sequentially zoned exposed, and phases of the phase modulation elements are sequentially adjusted according to different grating regions of the to-be-modulated grating to obtain the zoned grating.

14. The method of claim 12, wherein, The phase modulation elements comprise a diffractive optical element, a blazed grating or a metasurface, and the performing zoned exposure on the to-be-modulated grating and adjusting phases of the phase modulation elements according to different grating regions of the to-be-modulated grating to obtain the zoned grating comprises: simultaneously performing zoned exposure on different grating regions of the to-be-modulated grating, and adjusting phases of the phase modulation elements according to different grating regions of the to-be-modulated grating to obtain the zoned grating.

Images