Optical waveguide structure and AR display device

Abstract

The utility model provides an optical waveguide structure and AR display equipment. The optical waveguide structure includes: a waveguide substrate; the coupling-in area is arranged on the waveguide substrate; a plurality of diffraction grating areas, the two side surfaces of the waveguide substrate are both provided with the diffraction grating areas, the number of the diffraction grating areas on at least one side surface of the waveguide substrate is greater than or equal to 2, the periods of the plurality of diffraction grating areas are equal, and the plurality of diffraction grating areas are used for performing pupil expansion on light for multiple times; the coupling-in area is arranged on the waveguide substrate, the coupling-out area is arranged on the waveguide substrate, the diffraction grating areas are all located between the coupling-in area and the coupling-out area, and the coupling-out area is used for pupil-expanding transmission and emission of light in the waveguide substrate. According to the utility model, the problem that color uniformity and diffraction efficiency of an optical waveguide structure in the prior art are difficult to consider at the same time is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of optical devices, and particularly to an optical waveguide structure and an AR display device. Background Art

[0002] With the continuous development of AR technology, various types of AR display devices have gradually appeared in people's lives. Taking AR glasses as an example, an optical waveguide structure is usually equipped in AR glasses to realize image display. Currently, the solutions of optical waveguide structures mainly include surface relief, volume holography, and array waveguide. Among them, both surface relief and volume holography are based on physical optics. When light of different wavelengths diffracts, chromatic dispersion will occur, resulting in asynchronous propagation of light of different wavelengths in the optical waveguide in the same field of view, introducing an efficiency difference of different wavelengths in the subsequent light propagation process, that is, the transmission efficiencies of different wavelengths are inconsistent, which is reflected as a color deviation in the finally coupled-out light field. The array waveguide is based on the principle of geometric optics and mainly uses the process of light transmission by reflection or total reflection or partial reflection and partial transmission. No chromatic dispersion is introduced during the process. Although its uniformity is better than that of the surface relief and volume holography solutions, the diffraction efficiency is poor.

[0003] That is to say, there is a problem in the optical waveguide structure in the prior art that it is difficult to simultaneously take into account color uniformity and diffraction efficiency. Summary of the Utility Model

[0004] The main purpose of the present utility model is to provide an optical waveguide structure and an AR display device to solve the problem in the optical waveguide structure in the prior art that it is difficult to simultaneously take into account color uniformity and diffraction efficiency.

[0005] To achieve the above purpose, according to one aspect of the present utility model, an optical waveguide structure is provided, including: a waveguide substrate; an input region provided on the waveguide substrate; a plurality of diffraction grating regions, with diffraction grating regions provided on both side surfaces of the waveguide substrate and the number of diffraction grating regions on at least one side surface of the waveguide substrate being greater than or equal to 2. The periods of the plurality of diffraction grating regions are equal, and the plurality of diffraction grating regions are used for performing multiple pupil expansions on light; an output region provided on the waveguide substrate, with the plurality of diffraction grating regions all located between the input region and the output region, and the output region is used for expanding the pupil of the light in the waveguide substrate and transmitting and emitting it.

[0006] Further, the plurality of diffraction grating regions include a first diffraction grating region, a second diffraction grating region, and a third diffraction grating region. The first diffraction grating region and the second diffraction grating region are located on one side surface of the waveguide substrate, and the third diffraction grating region is located on the other side surface of the waveguide substrate. The first diffraction grating region is used for receiving the light from the input region and performing the first pupil expansion, and the second diffraction grating region and the third diffraction grating are used for receiving the light from the first diffraction grating region and realizing the second pupil expansion.

[0007] Further, the first diffraction grating region and the second diffraction grating region are arranged continuously or at intervals, the second diffraction grating region is the same as the third diffraction grating region, and at least a part of the projection of the second diffraction grating region on the waveguide substrate coincides with the projection of the third diffraction grating region on the waveguide substrate; and / or the first diffraction grating region performs a first pupil expansion on the light, the second diffraction grating region performs a second pupil expansion on the light, and the third diffraction grating region performs a third pupil expansion on the light, wherein the pupil expansion propagation directions of the light on the first diffraction grating region and the third diffraction grating region are the same, and the pupil expansion propagation direction of the light on the first diffraction grating region is different from the pupil expansion propagation direction of the light on the second diffraction grating region.

[0008] Further, the periods of the first diffraction grating region, the second diffraction grating region, and the third diffraction grating region are equal; and / or the angles between the grating vector directions of the first diffraction grating region, the second diffraction grating region, and the third diffraction grating region and the y-axis in the K-domain diagram are equal.

[0009] Further, the magnitudes of the grating vectors of the first diffraction grating region, the second diffraction grating region, and the third diffraction grating region are equal; and / or the grating vector direction of the second diffraction grating region is the same as the grating vector direction of the third diffraction grating region, and the grating vector direction of the first diffraction grating region is opposite to the grating vector direction of the second diffraction grating region.

[0010] Further, the 0th-order diffraction efficiency R of the first diffraction grating region 0 satisfies: 5% < R 0 < 60%, and the +1st or -1st order diffraction efficiency R 1 satisfies: 40% < R 1 < 95%; and / or the 0th-order diffraction efficiency R of the second diffraction grating region 0 satisfies: 10% < R 0 < 95%, and the +1st or -1st order diffraction efficiency R 1 satisfies: 5% < R 1 < 80%.

[0011] Further, at least one of the first diffraction grating region, the second diffraction grating region, and the third diffraction grating region is divided into multiple blocks, and at least one of the sag heights and duty cycles of the multiple blocks changes regularly. When one of the sag height and duty cycle changes regularly, the other of the sag height and duty cycle is a fixed value.

[0012] Further, the multiple diffraction grating regions include one or more of surface relief gratings and volume holographic gratings.

[0013] Further, the light coupling region includes one of a reflective surface and a prism. When the light coupling region includes the reflective surface, the reflective surface is located on the side surface of the waveguide substrate. The waveguide substrate has a first surface and a second surface which are oppositely arranged, and the reflective surface is arranged at an acute angle with one of the first surface and the second surface.

[0014] Further, the light extraction region includes a plurality of light splitting layers. The plurality of light splitting layers are arranged in an array in the waveguide substrate. The plurality of light splitting layers are located on one side of the diffraction grating region away from the light coupling region. The waveguide substrate has a first surface and a second surface which are oppositely arranged. Each light splitting layer is inclined to the first surface and the second surface. The number of the light splitting layers is greater than or equal to 3 and less than or equal to 10; and / or the reflectivity of the light splitting layer is greater than 5% and less than or equal to 55%; and / or the included angle between the light splitting layer and the second surface is equal to the included angle between the reflective surface of the light coupling region and the second surface.

[0015] According to another aspect of the present invention, there is provided an AR display device, including: an optical engine; the above-mentioned optical waveguide structure, and the optical engine is configured to emit image light to the optical waveguide structure.

[0016] Applying the technical solution of the present invention, the optical waveguide structure includes a waveguide substrate, a diffraction grating region, and a light extraction region. The light coupling region is arranged on the waveguide substrate; there are a plurality of diffraction grating regions. Diffraction grating regions are arranged on both side surfaces of the waveguide substrate, and the number of diffraction grating regions on at least one side surface of the waveguide substrate is greater than or equal to 2. The periods of the plurality of diffraction grating regions are equal. The plurality of diffraction grating regions are configured to perform multiple pupil expansions on light; the light extraction region is arranged on the waveguide substrate. The plurality of diffraction grating regions are all located between the light coupling region and the light extraction region. The light extraction region is configured to expand the pupil of the light in the waveguide substrate and transmit and emit it.

[0017] The light coupling region is configured to introduce the light emitted by the external optical engine into the waveguide substrate and transmit it in the waveguide substrate, and then transmit it to the plurality of diffraction grating regions. The plurality of diffraction grating regions receive the light transmitted by the light coupling region and perform multiple pupil expansion transmissions. By reasonably planning the positions of the plurality of diffraction grating regions, diffraction grating regions are arranged on both side surfaces of the waveguide substrate, and the number of diffraction grating regions on at least one side surface is multiple. Further planning the periods of the respective diffraction grating regions to be equal, so that the diffraction grating regions on the two surfaces can fully expand the pupil of the light in the waveguide substrate, which is beneficial to reducing the total reflection step length of the light in the waveguide substrate, beneficial to improving the field density after pupil expansion, avoiding pupil separation, and at the same time beneficial to improving the diffraction efficiency, and can improve the color uniformity and illuminance uniformity of the extracted image. Description of the Drawings

[0018] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0019] Figure 1 Shows the k-domain diagram of the optical waveguide structure of Embodiment 1 of the present utility model;

[0020] Figure 2 Shows a schematic diagram of one side of the optical waveguide structure of Embodiment 1 of the present utility model;

[0021] Figure 3 Shows a schematic diagram of the other side of the optical waveguide structure of Embodiment 1 of the present utility model;

[0022] Figure 4 Shows Figure 2 The pupil expansion optical path diagram of the optical waveguide structure in;

[0023] Figure 5 And Figure 6 Respectively show the optical path diagrams of the optical waveguide structure of Embodiment 1 of the present utility model with and without the third diffraction grating region;

[0024] Figure 7 Shows the path energy schematic diagram after the first diffraction of the first diffraction grating region of the optical waveguide structure of Embodiment 1 of the present utility model;

[0025] Figure 8 Shows the path energy schematic diagram after the second diffraction of the first diffraction grating region of the optical waveguide structure of Embodiment 1 of the present utility model;

[0026] Figure 9 Shows the efficiency distribution schematic diagram of the first diffraction grating region of the optical waveguide structure of Embodiment 1 of the present utility model for regulating large-wavelength light;

[0027] Figure 10 Shows the efficiency distribution schematic diagram of the first diffraction grating region of the optical waveguide structure of Embodiment 1 of the present utility model for regulating small-wavelength light;

[0028] Figure 11 Shows the path energy schematic diagram after the second diffraction of the first diffraction grating region of the optical waveguide structure of Embodiment 1 of the present utility model for regulating large and small wavelength lights;

[0029] Figure 12 Shows the structural schematic diagram of the optical waveguide structure of Embodiment 1 of the present utility model;

[0030] Figure 13 Shows Figure 12 The cross-sectional view in the A-A direction of;

[0031] Figure 14 And Figure 15 Respectively show Figure 13 The enlarged views at B and C in;

[0032] Figure 16 Shows the k-domain diagram of the optical waveguide structure of the second embodiment of the present invention;

[0033] Figure 17 Shows the structural schematic diagram of the optical waveguide structure of the second embodiment of the present invention;

[0034] Figure 18 Shows the k-domain diagram of the optical waveguide structure of the third embodiment of the present invention;

[0035] Figure 19 Shows the structural schematic diagram of the optical waveguide structure of the third embodiment of the present invention;

[0036] Figure 20 Shows the structural comparison diagram of the optical waveguide structure of the third embodiment of the present invention and the first embodiment.

[0037] Among them, the above-mentioned drawings include the following reference numerals:

[0038] 10. Waveguide substrate; 11. First surface; 12. Second surface; 21. Reflective surface; 31. First diffraction grating region; 32. Second diffraction grating region; 33. Third diffraction grating region; 40. Coupling-out region; 41. Beam splitting layer. Detailed implementation manners

[0039] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0040] It should be pointed out that, unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0041] In the present invention, unless otherwise stated, the orientation words such as "upper, lower, top, bottom" are usually in the direction shown in the drawings, or in the vertical, perpendicular or gravitational direction of the component itself; similarly, for the convenience of understanding and description, "inner, outer" refer to the inner and outer of the contour of each component itself, but the above orientation words do not limit the present invention.

[0042] In order to solve the problem that it is difficult to simultaneously take into account the color uniformity and diffraction efficiency in the existing optical waveguide structure, the present invention provides an optical waveguide structure and an AR display device.

[0043] Such as Figures 1 to 20As shown, the optical waveguide structure includes a waveguide substrate 10, a diffraction grating region, and an output region 40. The input region is disposed on the waveguide substrate 10. There are multiple diffraction grating regions. Diffraction grating regions are provided on both side surfaces of the waveguide substrate 10, and the number of diffraction grating regions on at least one side surface of the waveguide substrate 10 is greater than or equal to 2. The periods of the multiple diffraction grating regions are equal. The multiple diffraction grating regions are used to perform multiple pupil expansions on light. The output region 40 is disposed on the waveguide substrate 10. All the multiple diffraction grating regions are located between the input region and the output region 40. The output region 40 is used to expand the pupil of the light in the waveguide substrate 10 and transmit and output it.

[0044] The input region is used to introduce the light emitted by the external optical machine into the waveguide substrate 10 and transmit it in the waveguide substrate 10, and then transmit it to the multiple diffraction grating regions. The multiple diffraction grating regions receive the light transmitted by the input region and perform multiple pupil-expanded transmissions. By reasonably planning the positions of the multiple diffraction grating regions, diffraction grating regions are provided on both side surfaces of the waveguide substrate 10, and the number of diffraction grating regions on at least one side surface is multiple. Further planning the periods of the respective diffraction grating regions to be equal, so that the diffraction grating regions on the two surfaces can fully expand the pupil of the light in the waveguide substrate 10, which is beneficial to reducing the total reflection step length of the light in the waveguide substrate 10, beneficial to improving the field density after pupil expansion, avoiding pupil separation, and at the same time beneficial to improving the diffraction efficiency, and can improve the color uniformity and illuminance uniformity of the output image.

[0045] It should be noted that the above input region and output region 40 are both geometric structures, and the transmission of light is realized by using the principles of reflection, total reflection, and beam splitting. The diffraction grating region can realize the diffraction effect on light. By selecting geometric structures for the input region and the output region 40, it is beneficial to avoid the light leakage and dispersion of the diffraction structure, beneficial to improving the input efficiency and output efficiency, avoiding the loss of light, and further improving the diffraction efficiency of the entire optical waveguide structure.

[0046] In an embodiment of the present application, the multiple diffraction grating regions include a first diffraction grating region 31, a second diffraction grating region 32, and a third diffraction grating region 33. The first diffraction grating region 31 and the second diffraction grating region 32 are located on one side surface of the waveguide substrate 10, and the third diffraction grating region 33 is located on the other side surface of the waveguide substrate 10. The first diffraction grating region 31 is used to receive the light from the coupling-in region and perform the first pupil expansion, and the second diffraction grating region 32 and the third diffraction grating are used to receive the light from the first diffraction grating region 31 and achieve the second pupil expansion. Specifically, the waveguide substrate 10 has a first surface 11 and a second surface 12 that are oppositely arranged. The first diffraction grating region 31 and the second diffraction grating region 32 are arranged continuously or at intervals on the first surface 11, and the third diffraction grating region 33 is arranged on the second surface 12. Moreover, the projection of the second diffraction grating region 32 on the waveguide substrate 10 and the projection of the third diffraction grating region 33 on the waveguide substrate 10 at least partially overlap. By adding the third diffraction grating, the third diffraction grating region 33 can control the diffraction efficiency distribution of different wavelengths through multiple diffractions, realize the first pupil expansion while improving the chromatic aberration introduced by diffraction in the optical waveguide structure. Furthermore, the third pupil expansion is realized through the coupling-out region 40. The optical waveguide structure of the present application integrates geometric structures and diffraction gratings, and can achieve two-dimensional pupil expansion with high efficiency, low chromatic aberration, and low light leakage.

[0047] In a preferred embodiment of the present application, the projection of the second diffraction grating region 32 on the waveguide substrate 10 and the projection of the third diffraction grating region 33 on the waveguide substrate 10 completely overlap. The projected area of the second diffraction grating region 32 on the waveguide substrate 10 is larger than the projected area of the first diffraction grating region 31 on the waveguide substrate 10, and the projected area of the second diffraction grating region 32 on the waveguide substrate 10 is equal to the projected area of the third diffraction grating region 33 on the waveguide substrate 10.

[0048] Specifically, the structures and parameters of the second diffraction grating region 32 and the third diffraction grating region 33 are the same. Specifically, the grating line direction of the second diffraction grating region 32 is the same as that of the third diffraction grating region 33, the vector magnitude of the second diffraction grating region 32 is the same as that of the third diffraction grating region 33, and the grating period of the second diffraction grating region 32 is equal to the grating period of the third diffraction grating region 33. Such a setting is beneficial for the second diffraction grating region 32 and the third diffraction grating region 33 to receive the light from the first diffraction grating region 31 to ensure more sufficient secondary pupil expansion. At the same time, it is beneficial for the third diffraction grating region 33 to control the diffraction efficiency distribution of different wavelengths through multiple diffractions, which is beneficial for improving the chromatic aberration introduced by diffraction and increasing color uniformity. In some alternative embodiments, the second diffraction grating region 32 and the third diffraction grating region 33 being the same also includes the same duty cycle and the same height.

[0049] In one embodiment of the present application, the first diffraction grating region 31 performs the first pupil expansion on the light, the second diffraction grating region 32 performs the second pupil expansion on the light, and the third diffraction grating region 33 performs the third pupil expansion on the light. Among them, the pupil expansion propagation directions of the light on the first diffraction grating region 31 and the third diffraction grating region 33 are the same, and the pupil expansion propagation direction of the light on the first diffraction grating region 31 is different from the pupil expansion propagation direction of the light on the second diffraction grating region 32. That is to say, the light completes the first pupil expansion while propagating forward in the first diffraction grating region 31, completes the second pupil expansion while propagating forward in the second diffraction grating region 32, and completes the third pupil expansion while propagating forward in the third diffraction grating region 33. Among them, the propagation directions of the light in the first diffraction grating region 31 and the third diffraction grating region 33 are the same, the propagation direction of the light in the first diffraction grating region 31 is different from the propagation direction of the light in the second diffraction grating region 32, and the propagation direction of the light in the third diffraction grating region 33 is different from the propagation direction of the light in the second diffraction grating region 32. Such a setting effectively improves the overall efficiency difference of different wavelengths in the same field of view and enhances the color and illuminance uniformity of the coupled output light field.

[0050] In a specific embodiment of the present application, the periods of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 are equal. Such a setting is beneficial to ensuring the stability of pupil expansion transmission and high diffraction efficiency.

[0051] In a specific embodiment of the present application, reference can be made to Figure 1 , the included angles between the grating vector directions of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 on the K-domain diagram and the y-axis are equal. Specifically, the included angle between the grating vector direction of the first diffraction grating region 31 and the y-axis on the K-domain diagram, the included angle between the grating vector direction of the second diffraction grating region 32 and the y-axis on the K-domain diagram, and the included angle between the grating vector direction of the third diffraction grating region 33 and the y-axis on the K-domain diagram are equal. Such a setting is beneficial to the diffraction of the three diffraction grating regions away from the matching K-domain closed-loop requirements, is beneficial to planning the transmission path of the light in the waveguide substrate 10, avoiding light loss, and ensuring diffraction efficiency.

[0052] Specifically, reference can be made to Figure 1, the grating vector magnitudes of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 are equal, thus ensuring the K-domain closed loop. The grating vector directions of the second diffraction grating region 32 and the third diffraction grating region 33 are the same, so as to ensure that the second diffraction grating region 32 and the third diffraction grating region 33 can simultaneously achieve secondary pupil expansion, and ensure that the light after pupil expansion can be stably transmitted to the output region 40, ensuring the reliability of diffraction transmission. The grating vector direction of the first diffraction grating region 31 is opposite to the grating vector direction of the second diffraction grating region 32, and the grating vector direction of the first diffraction grating region 31 is opposite to the grating vector direction of the third diffraction grating region 33. Such a setting is conducive to ensuring that the diffraction dispersion of the grating is compensated to 0, ensuring the K-domain closed loop.

[0053] In a specific embodiment of the present application, the multiple diffraction grating regions include one or more of surface relief gratings and volume holographic gratings. The gratings in the volume holographic gratings are structures with a gradually changing refractive index to achieve the diffraction function. The multiple diffraction grating regions are all one-dimensional grating structures. The three diffraction grating regions cooperate with each other and have pupil expansion in two directions, so that the optical waveguide structure can achieve two-dimensional pupil expansion and ensure the uniformity of the final color display and the illuminance uniformity. At least one of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 is divided into multiple blocks, and at least one of the vector heights and duty cycles of the multiple blocks changes regularly. When one of the vector height and duty cycle changes regularly, the other of the vector height and duty cycle is a fixed value. By dividing the grating region into multiple blocks and modulating the duty cycle or vector height of different blocks at the same time, it not only ensures that the grating region can complete one-time pupil expansion while achieving turning, which is beneficial to the compensation of diffraction dispersion in the subsequent propagation process, making the color distribution of the light field of the finally output waveguide substrate 10 more uniform; the setting of dividing into blocks can modulate the diffraction efficiency of different levels of different blocks, which is beneficial to modulating the illuminance and color uniformity of the output light field, making the color uniformity of the output light field better.

[0054] Specifically, the first diffraction grating region 31 is a surface relief grating or a volume holographic grating. In an alternative embodiment of the present application, the first diffraction grating region 31 is integrally provided. In another alternative embodiment of the present application, the first diffraction grating region 31 is divided into multiple blocks, and one of the sagittal height and the duty cycle of the multiple blocks changes regularly, and the other of the sagittal height and the duty cycle is a fixed value. When the sagittal height of the multiple blocks changes regularly, the sagittal height of each block is different, and the sagittal height of each block can gradually increase or gradually decrease along the diffraction transmission path. When the duty cycle of the multiple blocks changes regularly, the duty cycle of each block is different, and the duty cycle of each block can gradually increase or gradually decrease along the diffraction transmission path. When the light beam irradiates the first diffraction grating region 31, +1st order and 0th order light beams or -1st order and 0th order light beams are diffracted. The +1st order or -1st order light beam propagates in the direction of the second diffraction grating region 32 and the third diffraction grating region 33, and the 0th order light beam continues to propagate by total internal reflection in the waveguide substrate 10 while maintaining the propagation direction unchanged. When it contacts the first diffraction grating region 31 again next time, +1st order and 0th order light beams or -1st order and 0th order light beams are diffracted again. After multiple diffractions, one pupil expansion is completed. Such a facility is beneficial to improving the zero-order diffraction fringe.

[0055] More specifically, the zero-order diffraction efficiency R of the first diffraction grating region 31 0 Satisfies: 5% < R 0 < 60%, and the +1st order or -1st order diffraction efficiency R 1 Satisfies: 40% < R 1 < 95%. By dividing the first diffraction grating region 31 into multiple blocks and modulating the sagittal height or the duty cycle of each block, the distribution of the diffraction efficiency ratio of different small blocks can be realized to weaken the color deviation caused by the difference in the total internal reflection step length and the diffraction efficiency of different wavelengths during subsequent propagation. The small block that the light contacts first has a high zero-order efficiency for the long-wavelength spectrum and a low +1st order or -1st order diffraction efficiency, and vice versa for the short wavelength, so as to improve the spatial energy coincidence degree of the transmission paths of different wavelengths in the next grating region.

[0056] It should be noted that when the first diffraction grating region 31 is divided into multiple blocks, the multiple blocks can be arranged in a grid-like array, or divided into multiple blocks along the light transmission direction of the coupling-in region, and each block matches the light of different wavelength ranges.

[0057] Specifically, the second diffraction grating region 32 is a surface relief grating or a volume holographic grating. In an alternative embodiment of the present application, the second diffraction grating region 32 is integrally provided. In another alternative embodiment of the present application, the second diffraction grating region 32 is divided into multiple blocks, and one of the vector heights and duty cycles of the multiple blocks changes regularly, and the other of the vector height and duty cycle is a fixed value. When the vector heights of the multiple blocks change regularly, the vector heights of each block are different, and the vector heights of each block can gradually increase or gradually decrease along the diffraction transmission path. When the duty cycles of the multiple blocks change regularly, the duty cycles of each block are different, and the duty cycles of each block can gradually increase or gradually decrease along the diffraction transmission path. After the light beam contacts the block, -1st order and 0th order or +1st order and 0th order light beams are diffracted, where the -1st order or +1st order turns to the coupling-out region 40, and the 0th order continues to propagate in the original direction until the next block, and continues to split and turn at the next block to complete secondary pupil expansion. The 0th order diffraction efficiency R of the second diffraction grating region 32 0 satisfies: 10% < R 0 < 95%, and the +1st order or -1st order diffraction efficiency R 1 satisfies: 5% < R 1 < 80%. Such a setting enables the second diffraction grating region 32 to receive the light field turned by the first diffraction grating region 31, turn the light field to the coupling-out region 40, and achieve secondary pupil expansion during this process. The diffraction order efficiency of each block can be set separately by modulating the duty cycle or the vector height, which is beneficial to modulating the light field color and illuminance distribution and ensuring the uniformity of the coupling-out color. It should be noted that when the second diffraction grating region 32 is divided into multiple blocks, the multiple blocks can be arranged in a grid-like array, or divided into multiple blocks along the light transmission direction perpendicular to the first diffraction grating region 31, and each block matches light rays in different wavelength ranges.

[0058] Specifically, the third diffraction grating region 33 is a surface relief grating or a volume holographic grating. The third diffraction grating region 33 is integral or divided into multiple blocks, and the partition modulation method of the third diffraction grating region 33 is the same as that of the second diffraction grating region 32, that is, the structural parameters of the third diffraction grating region 33 are the same as those of the second diffraction grating region 32. The third diffraction grating region 33 can reduce the total reflection step length of the light beam in the waveguide substrate 10 while expanding the pupil, which is beneficial to improving the field of view density after pupil expansion and avoiding pupil separation. At the same time, the diffraction efficiency of small blocks is adjusted to make the coupled light field achieve high color and illuminance uniformity. The setting of the third diffraction grating region 33 plays a role in improving the field of view density after pupil expansion. On the premise of no pupil separation, the maximum thickness allowed by the waveguide substrate 10 is increased, and then the number of splitting layers 41 in the coupling-out region 40 is reduced, which is beneficial to improving the overall processability of the optical waveguide structure.

[0059] In addition, by setting the three diffraction grating regions in the form of diffraction gratings to achieve light turning, it is possible to avoid the process problems brought about by the need for multiple overlays in the geometric array for turning, and improve the processability and mass producibility of the optical waveguide structure.

[0060] In a specific embodiment of the present application, both the coupling-in region and the coupling-out region 40 are geometric structures. Specifically, the coupling-in region includes one of a reflecting surface 21 and a prism. When the coupling-in region includes the reflecting surface 21, one side surface of the waveguide substrate 10 is inclined with respect to the upper and lower surfaces, and a reflective film is deposited on this side surface to form the reflecting surface 21. The light beam refracts from the surface of the waveguide substrate 10 in contact with air into the waveguide substrate 10, and then is incident on the reflecting surface 21. The light beam is reflected or totally reflected by the reflecting surface 21 and is trapped in the waveguide substrate 10 to continue propagating. When the coupling-in region includes a prism, the prism is a refracting prism, specifically a triangular prism. One side surface of the triangular prism is attached to the surface of the waveguide substrate 10, and the light beam of the optical machine is introduced into the waveguide substrate 10 through the refraction of the prism, and then undergoes total reflection transmission in the waveguide substrate 10.

[0061] In a specific embodiment of the present application, when the coupling-in region includes the reflecting surface 21, the reflecting surface 21 is located on the side surface of the waveguide substrate 10. The waveguide substrate 10 has a first surface 11 and a second surface 12 that are oppositely arranged. The reflecting surface 21 is arranged at an obtuse angle with respect to the first surface 11 and at an acute angle with respect to the second surface 12. Both sides of the reflecting surface 21 are connected to the first surface 11 and the second surface 12 respectively. The angle θ between the reflecting surface 21 and the second surface 12 in Satisfies:

[0062] θ in > 1 / 2·*asin(sinθ H / n wg ) + asin(1 / n wg ) +;

[0063] Wherein, n wg is the refractive index of the waveguide substrate 10, D θ is the field of view angle of the optical machine, and k is the aspect ratio of the length and width of the projection screen of the optical machine. k > 1. D θ is actually the longitudinal field of view angle of the optical machine. θ H is the lateral field of view angle of the optical machine. Such a setting is beneficial to ensuring the reflection efficiency of the reflecting surface 21. Ensure that the light beam can be coupled in through the geometric reflection of the reflecting surface 21, and achieve two-dimensional pupil expansion, avoid light leakage of diffraction coupling out, and can achieve high efficiency; θ in Combined with parameters such as the material and FOV of the waveguide substrate 10 to determine the range, ensure that the incident light beam FOV can be completely transmitted in the waveguide substrate 10 without picture distortion.

[0064] Reference Figures 2 to 15As shown, the output region 40 includes a plurality of beam splitting layers 41. The plurality of beam splitting layers 41 are arranged in an array in the waveguide substrate 10. The plurality of beam splitting layers 41 are located on the side of the diffraction grating region away from the input region. Each beam splitting layer 41 is inclined with respect to the first surface 11 and the second surface 12. Any two adjacent beam splitting layers 41 among the plurality of beam splitting layers 41 are arranged in parallel. Each beam splitting layer 41 is formed by laminating a beam splitting film layer with angular selectivity and the waveguide substrate 10. The number of beam splitting layers 41 is preferably greater than or equal to 3 and less than or equal to 10; the reflectivity of each beam splitting layer 41 is greater than 5% and less than or equal to 55%, and the parallelism of each beam splitting layer 41 is preferably less than 6 ‘’ , the angle between the beam splitting layer 41 and the second surface 12 is equal to the angle between the reflecting surface 21 of the input region and the second surface 12, that is, θ out = θ in ; the plurality of beam splitting layers 41 perform a third pupil expansion on the light beam after the second diffraction grating region 32 and the third diffraction grating region 33 are turned. Thus, the optical waveguide structure completes three two-dimensional pupil expansions and couples out the light field. The output region 40 couples out the light beam through the beam splitting layers 41 of the geometric array and realizes two-dimensional pupil expansion, which is beneficial to avoiding light leakage in diffraction coupling and ensuring the output efficiency and output uniformity.

[0065] This application also provides an AR display device. The AR display device includes an optical engine and the above-mentioned optical waveguide structure. The optical engine is used to emit image light to the optical waveguide structure. In an alternative embodiment of this application, the AR display device can be an AR glasses, and the optical engine can emit colored light. The AR display device equipped with the above-mentioned optical waveguide structure can have the advantages of no dispersion, high efficiency, and high color uniformity.

[0066] The optical waveguide structure of this application will be described below in conjunction with specific embodiments and drawings.

[0067] Embodiment 1

[0068] As Figures 1 to 15 shown, the optical waveguide structure of Embodiment 1 is described.

[0069] Figure 1 The k-domain diagram of the optical waveguide structure of this embodiment is shown. The condition for the light ray to be able to completely transmit in the waveguide substrate 10 is that the field of view FOV of the light ray can satisfy the K-domain closed loop. As Figure 1 shown, among them, the light field emitted by the optical engine is reflected as the main ray perpendicular to the Z-axis in the K-domain diagram. The rectangular region k-in, that is, the rectangular array region formed by the plurality of central red dots, along the vector direction of the black solid arrow, the k vector after passing through the reflecting surface 21 is k-reflect, that is, the rectangular array region formed by the plurality of blue dots on the right. The vector k-r of the reflecting surface 21 is determined by θ in and the azimuth angle decide, The black solid arrow slanting downward is the vector direction of the first diffraction grating region 31. The k domain after passing through the first diffraction grating region 31 is k-g, and k-g includes k-g(b), k-g(g), and k-g(r), thereby forming a rectangular red dot matrix, a rectangular green dot matrix, and a rectangular blue dot matrix below. The vector directions of the second diffraction grating region 32 and the third diffraction grating region 33 are the dotted line directions slanting upward. The k domain after passing through the second diffraction grating region 32 and the third diffraction grating region 33 is k-g back, that is, a rectangular array formed by a plurality of pink-purple circles. The rectangular array formed by the plurality of pink-purple circles coincides with k-reflect. The black dotted arrow to the left is the vector direction of the coupling-out region 40. The k domain after passing through the coupling-out region 40 is k-out, that is, a rectangular array formed by a plurality of red circles in the center. The rectangular array formed by the plurality of red circles coincides with k-in, thereby forming a k domain closed loop. After the k-in coupled into the waveguide substrate 10 undergoes vector transformation in the first diffraction grating region 31, the second diffraction grating region 32, and the coupling-out region 40, it is finally coupled out of the waveguide substrate 10 with k-out having the same magnitude and opposite direction, forming a closed loop in the k domain diagram. During the process, the transformation of the FOV also satisfies the conditions of waveguide transmission, and the complete FOV can be transmitted. As can be seen from the figure, the grating vector magnitudes of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 on the K domain diagram are equal. The grating vector direction of the first diffraction grating region 31 is opposite to the grating vector direction of the second diffraction grating region 32, that is, the grating vector directions of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 on the K domain diagram are all arranged in parallel.

[0070] Figure 2 and Figure 3 shows a schematic diagram of both side surfaces of the optical waveguide structure of this embodiment. Figure 4 shows the optical path diagram of the optical waveguide structure of this embodiment. In this embodiment, the coupling-in region is the coating reflective surface 21, and the coupling-out region 40 includes a plurality of parallel splitting layers 41, specifically 6 splitting layers 41. The first diffraction grating region 31 and the second diffraction grating region 32 are arranged at intervals on the first surface 11 of the waveguide substrate 10 and are located between the coupling-in region and the coupling-out region 40. The arrangement direction of the first diffraction grating region 31 and the second diffraction grating region 32 forms an acute angle or an obtuse angle with the splitting layers 41. The third diffraction grating region 33 is located on the second surface 12 of the waveguide substrate 10 and corresponds to the second diffraction grating region 32, and the projected area of the second diffraction grating region 32 on the waveguide substrate 10 completely coincides with and is equal to the projected area of the third diffraction grating on the waveguide substrate 10.

[0071] As Figure 5 and Figure 6 shown, Figure 5 the third diffraction grating is not provided in Figure 6A third diffraction grating is provided. As can be seen from the figure, adding the third diffraction grating is beneficial to reducing the total reflection step length of light in the waveguide substrate 10, improving the field density after pupil expansion, avoiding pupil separation, and at the same time improving the diffraction efficiency, which can improve the color uniformity and illumination uniformity of the coupled-out image.

[0072] As Figures 12 to 15 shown, the longitudinal field of view angle D θ of the optical machine is 30°, the angle θ in between the reflecting surface 21 and the second surface 12 is 25.7°, the azimuth angle of the reflecting surface 21, the refractive index n wg of the waveguide substrate 10 is 1.64, the angle θ colck between the grating vector direction of any one of the first diffraction grating region 31, the second diffraction grating region 32 and the third diffraction grating region 33 on the K-domain diagram and the y-axis is 120°, the grating periods of any one of the first diffraction grating region 31, the second diffraction grating region 32 and the third diffraction grating region 33 are the same, and are all d = 420 nm, the angle θ out between the beam splitting layer 41 and the second surface 12 is 25.7°. Each beam splitting layer 41 is coated with a beam splitting film, and the reflectivities of the six beam splitting layers 41 in the direction away from the diffraction grating region are r 1 = 10%, r 2 = 11.1%, r 3 = 12.5%, r 4 = 14.28%, r 5 = 16.67%, r 6 = 20%.

[0073] As Figures 7 to 11 shown, the first diffraction grating region 31 is a whole, the sag height of the first diffraction grating region 31 is 55.8 um, and the duty cycle is 66.25%; the duty cycles of the second diffraction grating region 32 and the third diffraction grating region 33 are the same as that of the first diffraction grating region 31. The second diffraction grating region 32 is divided into multiple blocks, and the duty cycle of each block is 66.25%. The sag heights of different blocks are different. Specifically, the sag heights of multiple blocks gradually increase in the direction away from the second diffraction grating region 32, and the sag heights of multiple blocks gradually increase from 66.32 um to 145.95 um in the direction away from the second diffraction grating region 32. The third diffraction grating region 33 is the same as the second diffraction grating region 32. Thus, the diffraction efficiencies of different orders of different blocks can be modulated, which is beneficial to modulating the illumination and color uniformity of the coupled-out light field, making the color uniformity of the coupled-out light field better. The spatial propagation regions of large-wavelength and small-wavelength light are planned to ensure the stability of diffraction transmission. Figure 7The figure shows the schematic diagram of the path energy coincidence after the first diffraction grating region 31 diffracts the light. It can be seen from the figure that the overlapping region of the spatial propagation of the large and small wavelengths is small. Figure 8 The figure shows the schematic diagram of the path energy coincidence after the first diffraction grating region 31 diffracts the light twice. It can be seen from the figure that the overlapping region of the spatial propagation of the large and small wavelengths increases. As Figure 9 and Figure 10 shown, by adjusting the duty cycle and the vector height of the first diffraction grating, the efficiency distribution of the two diffractions of the large wavelength and the small wavelength is adjusted. Thus, Figure 11 is obtained. It can be known from Figure 11 that the energy proportion of the overlapping region of the spatial propagation of the large and small wavelengths increases.

[0074] Embodiment 2

[0075] As Figure 16 and Figure 17 shown, the optical waveguide structure of Embodiment 2 is described.

[0076] Figure 16 The figure shows the k-domain diagram of the optical waveguide structure of this embodiment. For the explanation of the k-domain diagram, reference can be made to the description of Embodiment 1. Figure 17 The figure shows the schematic diagram of the structure of the optical waveguide structure of this embodiment.

[0077] In this embodiment, the azimuth angle of the reflecting surface 21 The included angle θ between the grating vector direction of any one of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 and the y-axis on the K-domain diagram colck = 130°. The grating periods of any one of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 are the same, and are all d = 450 nm. The remaining parameters are the same as those in Embodiment 1.

[0078] As Figure 17 shown, both the reflecting surface 21 and the beam splitting layer 41 are tilted by a certain angle compared with Embodiment 1. Such a setting makes the light beam obtain an additional y-direction component when reflecting on the reflecting surface 21, so that the FOV range in the k-domain is no longer rectangular, but rotates close to a rhombus. In this configuration, the grating period decreases, and the dispersion of the light beams with different wavelengths also decreases accordingly, which is beneficial to improving the chromaticity uniformity of the finally coupled output.

[0079] Embodiment 3

[0080] As Figures 18 to 20 shown, the optical waveguide structure of Embodiment 3 is described.

[0081] Figure 18 The figure shows the k-domain diagram of the optical waveguide structure of this embodiment. For the explanation of the k-domain diagram, reference can be made to the description of Embodiment 1. Figure 19The structural schematic diagram of the optical waveguide structure of this embodiment is shown. Figure 20 The comparison diagram of the optical waveguide structures of this embodiment and the first embodiment is shown.

[0082] In this embodiment, the longitudinal field of view angle D of the optical engine θ = 40°, the included angle θ between the reflecting surface 21 and the second surface 12 in = 25.7°, the azimuth angle of the reflecting surface 21 The refractive index n of the waveguide substrate 10 wg = 1.84, the included angle θ between the grating vector direction of any one of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 and the y-axis on the K-domain diagram colck = 135°, the grating periods of any one of the first diffraction grating region 31, the second diffraction grating region 32, and the third diffraction grating region 33 are the same, and are all d = 280 nm. The included angle θ between the beam splitting layer 41 and the second surface 12 out = 25.7°. Each beam splitting layer 41 is coated with a beam splitting film. The reflectivities of the six beam splitting layers 41 in the direction away from the diffraction grating region are respectively r 1 = r 2 = 11.45%, r 3 = r 4 = 14.28%, r 5 = r 6 = 22%. The 6 beam splitting layers 41 of this embodiment only adopt three sets of film systems. At this time, the uniformity of the coupled output slightly decreases, but the number of film systems decreases, which is beneficial to reducing the cost of the film system. At the same time, due to the reduction of the number of film systems, material control is easier, and process control also becomes simple, which is conducive to improving the mass producibility of the optical waveguide structure product.

[0083] As Figure 18 shown, in the K-domain diagram, the y-direction component of the beam angle propagation direction after passing through the first diffraction grating region 31 is larger and is close to vertically downward. Therefore, the propagation distance of the beam in the x-direction is shorter. Compared with the first embodiment, the structural layout on the waveguide substrate 10 is more compact laterally and has more advantages in products with a smaller area of the waveguide substrate 10.

[0084] As Figure 19 and Figure 20 shown, the first diffraction grating region 31 and the second diffraction grating region 32 of this embodiment are continuously arranged, that is, there is no gap between them. Such a setting makes the appearance of the optical waveguide structure of this embodiment more beautiful than that of the first embodiment.

[0085] Obviously, the embodiments described above are only a part of the embodiments of the present utility model, rather than all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present utility model.

[0086] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0087] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order different from those illustrated or described herein.

[0088] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. For those skilled in the art, the present utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. An optical waveguide structure, characterized in that: include: A waveguide substrate (10); A coupling-in region, the coupling-in region being arranged on the waveguide substrate (10); a diffraction grating region, wherein there are a plurality of diffraction grating regions, the diffraction grating regions are arranged on both side surfaces of the waveguide substrate (10), and the number of the diffraction grating regions on at least one side surface of the waveguide substrate (10) is greater than or equal to 2, the periods of the plurality of diffraction grating regions are equal, and the plurality of diffraction grating regions are used to perform multiple pupil expansion on light; An outcoupling region (40), the outcoupling region (40) being arranged on the waveguide substrate (10), a plurality of the diffraction grating regions being located between the incoupling region and the outcoupling region (40), the outcoupling region (40) being used to dilate and transmit the light in the waveguide substrate (10) and emit it.

2. The optical waveguide structure according to claim 1, characterized in that: The plurality of diffraction grating regions include a first diffraction grating region (31), a second diffraction grating region (32) and a third diffraction grating region (33); the first diffraction grating region (31) and the second diffraction grating region (32) are located on one side surface of the waveguide substrate (10); the third diffraction grating region (33) is located on the other side surface of the waveguide substrate (10); the first diffraction grating region (31) is used to receive light from the coupling region and perform a first pupil expansion; the second diffraction grating region (32) and the third diffraction grating are used to receive light from the first diffraction grating region (31) and perform a second pupil expansion.

3. The optical waveguide structure according to claim 2, characterized in that: The first diffraction grating region (31) and the second diffraction grating region (32) are arranged continuously or alternately, the second diffraction grating region (32) is the same as the third diffraction grating region (33), and a projection of the second diffraction grating region (32) on the waveguide substrate (10) and a projection of the third diffraction grating region (33) on the waveguide substrate (10) at least partially overlap; and / or The first diffraction grating area (31) performs a first pupil dilation on the light, the second diffraction grating area (32) performs a second pupil dilation on the light, and the third diffraction grating area (33) performs a third pupil dilation on the light, wherein the pupil dilation propagation direction of the light in the first diffraction grating area (31) and the third diffraction grating area (33) are the same, and the pupil dilation propagation direction of the light in the first diffraction grating area (31) is different from the pupil dilation propagation direction of the light in the second diffraction grating area (32).

4. The optical waveguide structure according to claim 2, characterized in that: The periods of the first diffraction grating region (31), the second diffraction grating region (32) and the third diffraction grating region (33) are equal; and / or The angles between the grating vector directions of the first diffraction grating region (31), the second diffraction grating region (32) and the third diffraction grating region (33) and the y-axis on the K-domain diagram are equal.

5. The optical waveguide structure according to claim 2, characterized in that: The grating vectors of the first diffraction grating region (31), the second diffraction grating region (32), and the third diffraction grating region (33) are equal in magnitude; and / or The grating vector direction of the second diffraction grating region (32) is the same as that of the third diffraction grating region (33), and the grating vector direction of the first diffraction grating region (31) is opposite to that of the second diffraction grating region (32).

6. The optical waveguide structure according to claim 2, wherein The 0th-order diffraction efficiency R0 of the first diffraction grating region (31) satisfies: 5% < R0 < 60%, and the +1st or -1st-order diffraction efficiency R1 satisfies: 40% < R1 < 95%; and / or The 0th-order diffraction efficiency R0 of the second diffraction grating region (32) satisfies: 10% < R0 < 95%, and the +1st or -1st-order diffraction efficiency R1 satisfies: 5% < R1 < 80%.

7. The optical waveguide structure according to claim 2 or 6, characterized in that: At least one of the first diffraction grating region (31), the second diffraction grating region (32), and the third diffraction grating region (33) is divided into a plurality of blocks, and at least one of the sag height and the duty ratio of the plurality of blocks changes regularly. When one of the sag height and the duty ratio changes regularly, the other of the sag height and the duty ratio is a fixed value.

8. The optical waveguide structure according to any one of claims 1 to 6, characterized in that: The plurality of diffraction grating regions include one or more of surface relief gratings and volume holographic gratings.

9. The optical waveguide structure according to any one of claims 1 to 6, characterized in that: The coupling-in region includes one of a reflective surface (21) and a prism. When the coupling-in region includes the reflective surface (21), the reflective surface (21) is located on the side surface of the waveguide substrate (10). The waveguide substrate (10) has a first surface (11) and a second surface (12) arranged opposite to each other, and the reflective surface (21) is arranged at an acute angle with one of the first surface (11) and the second surface (12).

10. The optical waveguide structure according to any one of claims 1 to 6, characterized in that: The coupling-out region (40) includes a plurality of beam splitting layers (41). The plurality of beam splitting layers (41) are arranged in an array in the waveguide substrate (10). The plurality of beam splitting layers (41) are located on the side of the diffraction grating region away from the coupling-in region. The waveguide substrate (10) has a first surface (11) and a second surface (12) arranged opposite to each other, and each beam splitting layer (41) is inclined with respect to the first surface (11) and the second surface (12). The number of the beam splitting layers (41) is greater than or equal to 3 and less than or equal to 10; and / or The reflectivity of the beam splitting layer (41) is greater than 5% and less than or equal to 55%; and / or The angle between the beam splitting layer (41) and the second surface (12) is equal to the angle between the reflective surface (21) of the coupling-in region and the second surface (12).

11. An AR display device, characterized in that: Comprising: An optical machine; The optical waveguide structure according to any one of claims 1 to 10, wherein the optical machine is configured to emit image light to the optical waveguide structure.

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