Optical waveguide structure, coating method and display equipment

Abstract

The invention relates to an optical waveguide structure, a coating method and a display device, and belongs to the technical field of optical display, the optical waveguide structure comprises a waveguide substrate and an entrance pupil area, the entrance pupil area is arranged on the waveguide substrate and used for coupling an image light beam emitted by an optical machine into the waveguide substrate, the entrance pupil area comprises sub-areas, and the sub-areas are arranged on the waveguide substrate. The sub-regions at least comprise a first region and a second region, optical film layers are arranged on the first region and the second region, and the thicknesses of the optical film layers on the sub-regions are different. Different light energy emitted by the left eye and the right eye, which is possibly caused by factors such as tiny deviation of a preparation process or asymmetry of a light source under the condition of uniform entrance pupil design, can be avoided, the effect of enabling the energy emitted by the eyes to be the same can be achieved, and the problems of energy loss and energy loss in the prior art are solved. Therefore, the technical problem of poor brightness uniformity of the emergent image is solved, and the uniformity of waveguide emergent energy is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical display, and in particular to an optical waveguide structure, a coating method and a display device. BACKGROUND

[0002] As a core component of augmented reality (AR), virtual reality (VR) and mixed reality (MR) near-eye display systems, optical waveguide technology is widely used in various head-mounted display devices due to its high resolution, thin form factor and good imaging quality. With the development of augmented reality (AR) technology, thin, low-power and high-efficiency display solutions have become the key to the commercialization of AR glasses. Among them, diffractive optical waveguide is a key technology for image transmission and pupil expansion in AR devices, and has become one of the mainstream optical solutions for near-eye display. The basic principle is that the image light from the micro display engine is diffractively coupled into the optical waveguide substrate through the "entrance pupil area" (input coupling grating), then transmitted in the substrate by total reflection, and finally diffractively coupled out to the human eye through the "exit pupil area" (output coupling grating).

[0003] In existing diffractive optical waveguides, the entrance pupil area is usually designed to have uniform parameters such as grating shape, period, depth and coating thickness, etc., so as to maintain a substantially uniform diffraction efficiency throughout the area. When the light source is incident on the entrance pupil area at a certain field of view (FOV), the total reflection angles of light rays of different angles are different in the waveguide. Among them, the light rays with smaller total reflection angles (usually corresponding to a part of the large field of view light rays) have shorter optical paths and will encounter the entrance pupil area again more quickly.

[0004] However, due to the uniform and high grating efficiency of the existing entrance pupil area, this part of the light rays will have a high probability of being diffractively coupled out of the waveguide when passing through the entrance pupil area for the second or even third time, resulting in serious energy loss. This loss is not uniform for different fields of view, which leads to poor brightness uniformity of the exit image. In addition, in binocular waveguide design, the left and right eye waveguides usually adopt a symmetrical structure. However, due to slight deviations in the preparation process or the asymmetry of the light source itself, the light energy emitted by the left and right eyes may be different, affecting the user experience. The existing optical waveguide with uniform efficiency entrance pupil structure cannot be adjusted at the structural level to compensate for the energy difference between the two eyes. SUMMARY

[0005] Therefore, the purpose of the present application is to provide an optical waveguide structure to solve the problem of different exit energies of the left and right eyes of the existing binocular waveguide, which leads to a large binocular energy difference, and the technical problem of energy loss in the prior art, which leads to poor brightness uniformity of the exit image.

[0006] The present application provides an optical waveguide structure, comprising: a waveguide substrate; an entrance pupil region arranged on the waveguide substrate, for coupling image light beams emitted by a light engine into the waveguide substrate; the entrance pupil region comprises sub-regions, and at least two of the sub-regions are provided, and an optical film layer is arranged on each of the sub-regions, and the thicknesses of the optical film layers on the at least two sub-regions are different.

[0007] Optionally, the two sub-regions are a first region and a second region, respectively, and the thickness of the optical film layer on the first region is greater than the thickness of the optical film layer on the second region.

[0008] Optionally, the n sub-regions are arranged along a first direction, the thickness of the optical film layer on the nth sub-region is not greater than the thickness of the optical film layer on the (n-1)th sub-region, and the thickness of the optical film layer on the nth sub-region is less than the thickness of the optical film layer on the first sub-region.

[0009] Optionally, the thicknesses of the optical film layers on the plurality of sub-regions decrease in sequence along the first direction.

[0010] Optionally, a plurality of diffraction gratings are arranged on the first region and the second region, respectively, the plurality of diffraction gratings are arranged along a first direction, and the optical film layer is arranged on the surface of the plurality of diffraction gratings.

[0011] Optionally, the diffraction gratings can be rectangular gratings, blazed gratings, triangular gratings or inclined gratings.

[0012] Optionally, the application further comprises an exit pupil region arranged on the waveguide substrate, for emitting image light beams in the waveguide substrate to a human eye, and the exit pupil region is provided with two exit pupil regions, and the entrance pupil region is arranged between the two exit pupil regions.

[0013] Optionally, the application further comprises a turning region arranged on the waveguide substrate and receiving light from the entrance pupil region, the turning region and the exit pupil region are arranged correspondingly, and the image light beams coupled into the waveguide substrate by the entrance pupil region are transmitted to the corresponding exit pupil region through the turning region.

[0014] The application further provides a film coating method, comprising: selecting a waveguide substrate, and forming an entrance pupil region on the waveguide substrate; exposing one of the sub-regions through a mask and shielding other sub-regions; forming an optical film layer on the surface of the exposed sub-region; By shielding of the mask, a predetermined thickness of the optical film layer is formed on the surface of each sub-region in sequence.

[0015] The application also provides a display device, comprising the optical waveguide structure as described above, and further comprising an optical engine configured to emit an image beam, wherein the optical engine is disposed at and aligned with the entrance pupil region.

[0016] The technical scheme of the application has the following advantages: The optical waveguide structure provided by the application comprises a first region and a second region with different thicknesses of optical film layers in the entrance pupil region, thereby forming a non-uniform diffraction efficiency regulation structure, and the two exit pupil regions and the turning region are configured to realize binocular waveguide, so that different entrance pupil diffraction efficiencies can be realized, and when the energy received by the left and right turning regions is different or the exit energy of the left and right eyes is different, the diffraction efficiency of the two sub-regions can be actively regulated by the different thicknesses of the optical film layers, thereby breaking the limitation of the traditional uniform entrance pupil design, making the exit energy of the binoculars the same, and avoiding the different exit light energy of the left and right eyes due to the small deviation of the preparation process or the asymmetry of the light source itself in the case of the uniform entrance pupil design.

[0017] Meanwhile, at least two sub-regions with different thicknesses of optical film layers can be arranged in the entrance pupil region to form a non-uniform diffraction efficiency regulation structure, and the diffraction efficiency of the sub-regions can be actively regulated by the different thicknesses of the optical film layers, thereby breaking the limitation of the traditional uniform entrance pupil design, reducing the ability of light with a small total reflection angle to couple out of the waveguide in the entrance pupil region, optimizing the energy utilization rate, and improving the uniformity of the light energy. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical scheme of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope, and other related drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 FIG. 1 is a schematic diagram of the cross-sectional structure of the entrance pupil region of the optical waveguide structure in the application; Figure 2 FIG. 2 is a schematic diagram of the cross-sectional structure of the optical waveguide structure in the application; Figure 3 FIG. 3 is a schematic diagram of another embodiment of the cross-sectional structure of the entrance pupil region of the optical waveguide structure in the application; Figure 4 FIG. 4 is a schematic diagram of the optical waveguide structure of the monocular waveguide in the application; Figure 5A structural schematic diagram of a light waveguide structure of a binocular waveguide in the application; Figure 6 A step diagram of a film coating method in the application.

[0020] Explanation of reference signs: 1, waveguide substrate; 2, entrance pupil area; 21, sub-area; 211, first area; 212, second area; 3, optical film layer; 4, exit pupil area; 5, turning area. DETAILED DESCRIPTION

[0021] The specific embodiments of the application will be described below in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the description of the application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the application.

[0022] Unless otherwise explicitly specified and limited, the terms "arrange", "mount", "connect" and the like shall be interpreted in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium. The specific meanings of the above terms can be understood according to the specific circumstances by those of ordinary skill in the art.

[0023] The terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the application is used, and are only for the convenience of description and simplification of description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0024] In the figure, the direction indicated by the arrow x is the first direction.

[0025] The terms "first", "second", "third" and the like are only used to distinguish similar attributes of elements, and do not indicate or imply relative importance or a specific order.

[0026] The terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, in addition to including the listed elements, other elements not explicitly listed can also be included.

[0027] Example 1 Reference Figures 1-6As shown, the present application provides an optical waveguide structure, comprising a waveguide substrate 1 and an entrance pupil area 2, wherein the waveguide substrate 1 is arranged as a slab waveguide, usually optical-grade glass or high-refractive optical plastic, and the entrance pupil area 2 is arranged on the waveguide substrate 1 for coupling the image light beams emitted by the light source into the waveguide substrate 1, and the entrance pupil area 2 comprises sub-areas 21, each of which comprises a first area 211 and a second area 212, and each of the sub-areas 21 is provided with an optical film layer 3, so that the surfaces of the first area 211 and the second area 212 are both provided with the optical film layer 3, and the thickness of the optical film layer 3 on the first area 211 is different from the thickness of the optical film layer 3 on the second area.

[0028] By arranging the first area 211 and the second area 212 with different thicknesses of the optical film layer 3 on the entrance pupil area 2, a non-uniform diffraction efficiency control structure is formed, and the diffraction efficiency of the sub-area 21 is actively controlled by differentiating the thickness of the optical film layer 3, which breaks the limitation of the traditional uniform entrance pupil design, reduces the ability of the light with a small total reflection angle to be coupled out of the waveguide at the entrance pupil area 2, optimizes the energy utilization rate, and improves the uniformity of the light energy; at the same time, the diffraction efficiency of the first area 211 and the second area 212 is actively controlled by differentiating the thickness of the optical film layer, so that the energy of the binocular exit is the same, which avoids the different light energy of the left and right eyes caused by the small deviation of the preparation process or the asymmetry of the light source itself in the case of the uniform entrance pupil design, so that the uniformity of the light energy is improved, and the energy of the binocular exit is the same.

[0029] Specifically, the thickness of the optical film layer 3 on the first area 211 is greater than the thickness of the optical film layer 3 on the second area 212, and for the optical film layer 3, in this embodiment, a high-refractive optical film (such as TiO2, Nb2O5, SiN, etc.) or a metal material or a non-metal material is arranged to adjust the efficiency of the diffraction grating at the entrance pupil area 2. For light rays with small total reflection angles and short optical paths, which usually correspond to light rays with large field angles, they will quickly turn back and encounter other sub-regions 21 of the entrance pupil area 2 with optical film layers 3 of small thickness. Due to the reduced thickness of the optical film layers 3 of the sub-regions 21, the diffraction efficiency is reduced, thereby greatly reducing the probability of unintended secondary coupling of light rays at this location, thereby retaining more energy within the waveguide substrate 1 and significantly improving the energy utilization of the system. This high diffraction efficiency area couples long optical path light rays, and the low diffraction efficiency area releases short optical path light rays, compensating for the inconsistent energy attenuation caused by the difference in wide path, fundamentally improving the uniformity of light brightness output from the exit pupil area 4, and making the binocular exit energy the same. As a specific embodiment, the optical waveguide structure further comprises an exit pupil area 4 disposed on the waveguide substrate 1 for coupling out and emitting the image light beams coupled into the waveguide substrate 1 by the entrance pupil area 2 to the human eye, and a certain gap is left between the exit pupil area 4 and the entrance pupil area 2. As shown in Figure 2 and Figure 5 The exit pupil area 4 is provided with two exit pupil areas 4, which are respectively located on both sides of the entrance pupil area 2, and the entrance pupil area 2 is located between the two exit pupil areas 4. The two exit pupil areas 4 are symmetrically arranged about the central axis of the optical waveguide structure, and the entrance pupil area 2 is located on the central axis, thereby realizing binocular waveguide.

[0030] The optical waveguide structure further comprises a turning area 5 disposed on the waveguide substrate 1 for receiving light rays from the entrance pupil area 2, and the turning area 5 is located between the entrance pupil area 2 and the exit pupil area 4.

[0031] When the exit pupil area 4 is provided with two exit pupil areas 4, the turning area 5 is also provided with two turning areas 5, which are located on both sides of the entrance pupil area 2, and the entrance pupil area 2 is located between the two turning areas 5. After the image light beams emitted by the light machine are coupled into the waveguide substrate 1 through the entrance pupil area 2, they will be transmitted to the two turning areas 5 respectively, and then transmitted to the corresponding exit pupil areas 4, thereby realizing binocular waveguide.

[0032] When the exit pupil area 4 is provided with two exit pupil areas 4 and the turning area 5 realizes binocular waveguide, different entrance pupil diffraction efficiencies can be realized, and the diffraction efficiency of the sub-region 21 is actively regulated by differentiating the thickness of the optical film layer 3, so that the binocular exit energy is the same, and the energy received by the left and right turning areas 5 or the exit energy of the left and right eyes is different due to the uniform entrance pupil design.

[0033] Specifically, when there are two exit pupil regions 4 and two transition regions 5, it is a binocular waveguide structure. In binocular waveguide design, the left and right eye waveguides usually adopt a symmetrical structure, that is, the exit pupil region 4 and the transition region 5 are both set symmetrically. However, due to slight deviations in the manufacturing process or the asymmetry of the light source itself, the light energy emitted from the left and right eyes will be different, which will affect the user experience. Existing optical waveguides with uniform efficiency entrance pupil structures cannot be adjusted at the structural level to compensate for this energy difference between the two eyes.

[0034] by Figure 5 Taking the transition region 5 in the middle as an example, the diffraction efficiency of the right transition region 5 is higher than that of the left transition region 5. If the efficiency of the exit pupil region 4 on both sides is the same, and the entrance pupil region 2 is symmetrical, the brightness of the right eye of the waveguide will be higher than that of the left eye of the waveguide, which will affect the user experience. Alternatively, the efficiency of the system composed of the left transition region 5 and the exit pupil region 4 is higher than that of the system composed of the right transition region 5 and the exit pupil region 4, which will make the brightness of the left eye higher or lower than that of the right eye, resulting in a large difference between the left and right eyes.

[0035] By changing the thickness of the optical film layers in the first region 211 and the second region 212 to be inconsistent, the diffraction efficiency of the first region 211 on the left is greater than that of the second region 212, i.e., the left side is greater than the right side. The light energy coupled into the left transition region 5 from the left first region 211 is greater than the light energy coupled into the right transition region 5 from the right second region 212. This changes the situation where the light energy coupled out of the left exit pupil region 4 is less than that coupled out of the right exit pupil region 4 because the diffraction efficiency of the left transition region 5 is less than that of the right transition region 5. Instead, the left first region 211 coupled in more light energy than the right second region 212. The total light energy coupled out of the two transition regions 5 into the exit pupil region 4 is equivalent, thus making the binocular emission energy the same.

[0036] In one specific implementation, multiple diffraction gratings are provided on both the first region 211 and the second region 212. The multiple diffraction gratings are arranged sequentially along the first direction. The optical film layer 3 is disposed on the surface of the multiple diffraction gratings in each sub-region 21 facing away from the waveguide substrate 1. The diffraction gratings can be rectangular gratings, blazed gratings, or tilted gratings that are symmetrical, so that the diffraction efficiency of the first region 211 is greater than that of the second region 212. Multiple one-dimensional or two-dimensional diffraction gratings are also provided on the turning region 5 and the exit pupil region 4, arranged sequentially along the first direction.

[0037] As an alternative implementation method, such as Figure 3 and Figure 4As shown, the entrance pupil area 2 and the exit pupil area 4 are each provided with one, thereby realizing a monocular waveguide, when the exit pupil area 4 is provided with one, the turning area 5 is also provided with one, when the image light beam emitted by the light engine is coupled into the waveguide substrate 1 through the entrance pupil area 2, it is first transmitted to the turning area 5, and then transmitted to the corresponding exit pupil area 4, and the turning area 5 can accept the image light beam coupled into the waveguide substrate 1 at any position of the entrance pupil area 2.

[0038] At this time, the sub-area 21 is provided with multiple, the diffraction grating on the sub-area 21 can be provided as a rectangular grating, a blazed grating, a triangular grating or an inclined grating, the multiple sub-areas 21 are arranged in the first direction and provided with n, wherein the thickness of the optical film layer 3 on the nth sub-area 21 is not greater than the thickness of the optical film layer 3 on the n-1th sub-area 21, and the thickness of the optical film layer 3 on the nth sub-area 21 is less than the thickness of the optical film layer 3 on the first sub-area 21. Further, the thickness of the optical film layer 3 on the multiple sub-areas 21 decreases in the first direction, i.e. the direction of the light propagation of the entrance pupil area 2 to the turning area 5.

[0039] Wherein, n is a positive integer.

[0040] Embodiment 2 Referring to Figures 1-6 As shown, the embodiment provides a coating method, including the following steps: S1, selecting a waveguide substrate 1, the waveguide substrate 1 is an optical grade glass or a high refractive index optical plastic, and a diffraction grating is formed on the surface of the waveguide substrate 1 to form an entrance pupil area 2, the entrance pupil area 2 is divided into at least two sub-areas 21; S2, shielding on the waveguide substrate 1 through a mask, exposing one of the sub-areas 21 and shielding the other sub-areas 21; S3, depositing an optical film layer 3 on the surface of the exposed sub-area 21 by vapor deposition, electron beam evaporation or magnetron sputtering; S4, forming an optical film layer 3 with a predetermined thickness on the surface of each sub-area 21 in turn through the shielding of the mask, so that the thickness of the optical film layer 3 on at least two sub-areas 21 is different. After the above process, the produced optical waveguide realizes the intelligent management of "high-efficiency area coupling long light path light, low-efficiency area releasing short light path light", and finally realizes the dual goals of energy utilization rate improvement, light uniformity improvement and binocular exit energy same at the system level.

[0041] Embodiment 3 The embodiment provides a display device, like Figures 1-5As shown, the optical waveguide structure in embodiment 1 or prepared by the coating method of embodiment 2, further comprises an optical engine for emitting an image light beam, the optical engine is arranged at and aligned with the entrance pupil area 2; by arranging two sub-areas 21 with different thickness optical film layers 3 at the entrance pupil area 2, a non-uniform diffraction efficiency control structure is formed, the diffraction efficiency of the first area 211 and the second area 212 is actively controlled by differentiating the thickness of the optical film layer, so that the energy of the binocular exit is the same, avoiding the situation that the energy of the left and right eye exit may be different due to the small deviation of the preparation process or the asymmetry of the light source itself and other factors under the design of the uniform entrance pupil, so that the uniformity of the light energy can be improved, and the energy of the binocular exit is the same, at the same time, the diffraction efficiency of the sub-area 21 is actively controlled by differentiating the thickness of the optical film layer 3, breaking the limitation of the traditional uniform entrance pupil design, reducing the ability of the light with small total reflection angle to couple out the waveguide in the entrance pupil area 2, optimizing the energy utilization, and improving the uniformity of the light energy.

[0042] It should be noted that each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0043] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. An optical waveguide structure, characterized in that, include: Waveguide substrate (1); An entrance pupil region (2) is disposed on the waveguide substrate (1) for coupling the image beam emitted by the optomechanical system into the waveguide substrate (1); The entrance pupil region (2) includes a sub-region (21), and there are at least two sub-regions (21). Each sub-region (21) is provided with an optical film layer (3), and the thickness of the optical film layer (3) on at least two sub-regions (21) is different.

2. The optical waveguide structure as described in claim 1, characterized in that, The sub-region (21) is provided in two parts, namely a first region (211) and a second region (212), wherein the thickness of the optical film layer (3) on the first region (211) is greater than the thickness of the optical film layer (3) on the second region (212).

3. The optical waveguide structure as described in claim 1, characterized in that, The sub-regions (21) are arranged in n directions, wherein the thickness of the optical film layer (3) on the nth sub-region (21) is not greater than the thickness of the optical film layer (3) on the (n-1)th sub-region (21), and the thickness of the optical film layer (3) on the nth sub-region (21) is less than the thickness of the optical film layer (3) on the first sub-region (21).

4. The optical waveguide structure as described in claim 3, characterized in that, The thickness of the optical film layer (3) on the multiple sub-regions (21) decreases sequentially along the first direction.

5. The optical waveguide structure as described in claim 1, characterized in that, Multiple diffraction gratings are provided on both the first region (211) and the second region (212), and the multiple diffraction gratings are arranged along the first direction. The optical film layer (3) is disposed on the surface of the multiple diffraction gratings.

6. The optical waveguide structure as described in claim 1, characterized in that, The diffraction grating can be configured as a rectangular grating, a blazed grating, a triangular grating, or a tilted grating.

7. The optical waveguide structure as described in claim 1, characterized in that, It also includes an exit pupil region (4), which is disposed on the waveguide substrate (1) and is used to emit the image beam in the waveguide substrate (1) to the human eye. There are two exit pupil regions (4), and the entrance pupil region (2) is disposed between the two exit pupil regions (4).

8. The optical waveguide structure as described in claim 7, characterized in that, It also includes a transition region (5), which is disposed on the waveguide substrate (1) and receives light from the entrance pupil region (2). The transition region (5) and the exit pupil region (4) are disposed correspondingly. The image beam coupled into the waveguide substrate (1) by the entrance pupil region (2) is transmitted to the corresponding exit pupil region (4) through the transition region (5).

9. A coating method, characterized in that, include: Select a waveguide substrate (1) and form an entrance pupil region (2) on the waveguide substrate (1). Using a mask, one sub-region (21) is exposed, while the other sub-regions (21) are hidden. An optical film layer (3) is formed on the surface of the exposed sub-region (21); By using a mask, an optical film layer (3) of a predetermined thickness is formed on the surface of each sub-region (21) in sequence.

10. A display device, characterized in that, The optical waveguide structure includes any one of claims 1-8, and further includes an optical engine for emitting an image beam, the optical engine being disposed at the entrance pupil region (2) and aligned with the entrance pupil region (2).

Images