An optical waveguide device

Abstract

The present invention discloses an optical waveguide device, wherein the waveguide plate comprises a coupling structure and a coupling structure, wherein the waveguide plate has a first surface and a second surface which are parallel to each other, the coupling structure is arranged on the waveguide plate, and the coupling structure is arranged between the first surface and the second surface; the coupling structure is used to couple the light emitted by the image source into the waveguide plate, so that the light is transmitted to the coupling structure by total reflection between the first surface and the second surface; the coupling structure comprises a plurality of splitting surfaces, which are formed by molecular bonding after two transparent substrates without any dielectric coating are superimposed, the splitting surfaces are parallel to each other and arranged at intervals, and the splitting surfaces have a preset angle with the first surface and the second surface of the waveguide plate; the coupling structure is used to expand the pupil of the light and couple out the waveguide plate. The problem of dark bands, smearing and mirror stray light in array optical waveguide display can be solved, and the yield rate can be improved and the production cost can be reduced.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of display technology, and in particular to an optical waveguide device. Background Art

[0002] Augmented Reality (AR) technology is a technology that integrates computer-generated virtual information with the real environment. It can dynamically superimpose virtual information on the real world in real time, thereby enhancing users' perception and understanding of the real world.

[0003] AR optical waveguide is an optical device used in augmented reality near-eye display devices. It can project virtual images directly into the user's eyes while ensuring that the user's view of the real world is not blocked.

[0004] From the perspective of optical principles, AR optical waveguides are currently mainly divided into array optical waveguides and diffraction optical waveguides. Different types of AR optical waveguides differ in performance, cost, and application scenarios. Currently, both types of optical waveguides have representative products on the market. Among them, array optical waveguides are significantly superior to diffraction optical waveguides in terms of single-chip full-color, color reproduction, and low back light leakage. However, there are still problems such as dark bands, smears, and mirror stray light in the display, and the processing yield is low and the cost is high. Whether it is an array optical waveguide or a diffraction optical waveguide, the transmittance of the display area is significantly lower than that of the non-display area. The transmittance is usually about 85%, which affects the appearance.

[0005] In the existing array optical waveguide, light is coupled into the optical waveguide through refraction and reflection, and is transmitted by total reflection in the optical waveguide. The out-coupling part uses an array beam splitter with a dichroic coating so that part of the total reflected light beam is reflected and coupled out into the human eye, and part continues to be transmitted by total reflection, thereby achieving pupil expansion. The out-coupling beam splitter has a dichroic coating, which is usually coated on the waveguide substrate. Its reflectivity needs to be specially designed. In order to ensure brightness uniformity, multiple film systems are usually required to couple out multiple beam splitters, such as Figure 1 As shown, the film system has a certain reflectivity within a specific angle range, and the color difference needs to be strictly controlled, otherwise the display will have color deviation. In addition, the reflectivity needs to be lowered within a large angle range to reduce the problem of dark band mirror stray light. This brings great difficulty to the coating design and cannot be completely solved. In order to achieve better color uniformity, the film system usually needs to be designed with a variety of film materials. The thickness of the film layer must be at least several hundred nanometers. The surface polishing of the finished waveguide will cause microscopic defects at the junction of the coating and the waveguide surface, resulting in stray light on the display. Dark bands and streaks are currently plaguing array optical waveguides. In addition, the waveguide plate needs to be thinned to reduce weight. The thinner the waveguide plate, the more coupling splitter surfaces are required, and the higher the cost of the waveguide plate. Summary of the invention

[0006] In view of this, an embodiment of the present invention provides an optical waveguide device, which can solve the problems of dark bands, streaking images and mirror stray light in array optical waveguide displays.

[0007] In a first aspect, an embodiment of the present invention provides an optical waveguide device, including a waveguide sheet; The waveguide plate comprises a coupling-in structure and a coupling-out structure, wherein the waveguide plate has a first surface and a second surface which are parallel to each other, the coupling-in structure is arranged on the waveguide plate, and the coupling-out structure is arranged between the first surface and the second surface; A coupling-in structure, used for coupling the light emitted by the image source into the waveguide plate, so that the light is transmitted to the coupling-out structure by total reflection between the first surface and the second surface; The out-coupling structure includes a plurality of splitting surfaces, which are formed by superimposing two transparent substrates without any dielectric coating and then molecularly bonded. The splitting surfaces are parallel to each other and spaced apart, and the splitting surfaces have a preset angle with the first surface and the second surface of the waveguide. The out-coupling structure is used to expand the pupil of light and couple out the waveguide.

[0008] Optionally, the multiple light splitting surfaces in the outcoupling structure are arranged at equal intervals.

[0009] Optionally, along a direction away from the incoupling structure, the intervals between the multiple light-splitting surfaces in the outcoupling structure gradually decrease.

[0010] Optionally, the out-coupling structure includes a first out-coupling region, a second out-coupling region and a third out-coupling region which are sequentially arranged away from the in-coupling structure; The intervals between the multiple light-splitting surfaces in the first outcoupling region are greater than the intervals between the multiple light-splitting surfaces in the second outcoupling region; the intervals between the multiple light-splitting surfaces in the second outcoupling region are greater than the intervals between the multiple light-splitting surfaces in the third outcoupling region.

[0011] Optionally, the plurality of light splitting surfaces of the first outcoupling region, the second outcoupling region and at least one of the first outcoupling region are arranged at equal intervals.

[0012] Optionally, an anti-reflection film is also included, and the anti-reflection film is located on the first surface and / or the second surface for light outcoupling.

[0013] Optionally, the coupling-in structure includes a prism structure or a reflector coupling-in structure.

[0014] Optionally, the surface roughness of the transparent substrate is less than or equal to 10 nm.

[0015] Optionally, the interval thickness between adjacent light-splitting surfaces is less than or equal to 1 mm.

[0016] The optical waveguide device provided in the embodiment of the present invention abandons the design concept of using coating on the splitter surface of the existing array waveguide, and uses a transparent substrate whose surface is not coated with any other material for bonding to form a splitter surface of the out-coupling structure, which can solve the problems of dark bands, smears and mirror stray light in the array optical waveguide display. The transmittance can reach 98%, which solves the aesthetic problem, improves the yield and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a relationship diagram of a film system with a dichroic coating on a coupling-out beam splitter surface in the prior art; Figure 2 A schematic top view of an optical waveguide device provided in an embodiment of the present application; Figure 3 for Figure 2 A schematic cross-sectional view of another optical waveguide device provided along the AA' direction; Figure 4 for Figure 2 A schematic cross-sectional view of another optical waveguide device provided along the AA' direction. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be fully described below in combination with the drawings in the embodiments of the present invention through specific implementation methods. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work fall within the protection scope of the present invention.

[0019] Example An embodiment of the present invention provides an optical waveguide device. Figure 2 A schematic top view of an optical waveguide device provided in an embodiment of the present application, referring to Figure 2 The optical waveguide device provided by the embodiment of the present invention includes a waveguide plate 1, and the waveguide plate 1 includes a coupling structure 11 and a coupling structure 12. The waveguide plate 1 has a first surface M1 and a second surface M2 that are parallel to each other. The coupling structure 11 is arranged on the waveguide plate 1, and the coupling structure 12 is arranged between the first surface M1 and the second surface M2. The coupling structure 11 is arranged on the waveguide plate 1, and the coupling structure 11 is used to couple the light emitted by the image source into the waveguide plate 1, so that the light is transmitted to the coupling structure 12 by total reflection between the first surface M1 and the second surface M2.

[0020] in, Figure 2 Figure (a) is a top view of the optical waveguide device. Figure 2 Figure (b) is a cross-sectional view of the optical waveguide device along the AA' direction.

[0021] Specifically, refer to Figure 2 , the waveguide device is made of transparent material as a whole, and the length and thickness of the waveguide 1 can be set according to the needs of the actual scene. When used in AR glasses, the length should be adapted to the wearer, and the thickness should not be too large. The first surface M1 and the second surface M2 of the waveguide are parallel to each other, and have at least one coupling structure 11 and a coupling structure 12. The image source (not shown in the figure) is used to emit light carrying image information, which can be used for AR glasses virtual imaging, etc. The coupling structure 11 can couple the light into the waveguide 1 by reflection or refraction, and then perform total reflection transmission. The coupling structure 12 is responsible for expanding the pupil and coupling the light into the human eye.

[0022] Total internal reflection (TIR) ​​is an optical phenomenon. When light enters a medium with a higher refractive index from a medium with a lower refractive index, if the incident angle is greater than or equal to the critical angle, the refracted light will disappear and all the incident light will be reflected without entering the medium with a lower refractive index.

[0023] In the optical waveguide scene provided in the embodiment of the present application, the refractive index of the waveguide plate 1 is greater than the refractive index of air. After the light is coupled into the waveguide plate 1 through the coupling-in structure 11, the light that satisfies total reflection propagation is transmitted from the waveguide plate 1 to the coupling-out structure 12. Among them, the coupling-out structure 12 includes a plurality of splitting surfaces 120, which are formed by molecular bonding after two transparent substrates are superimposed, and the splitting surfaces 120 are parallel to each other and arranged at intervals. The splitting surfaces 120 have a preset angle with the first surface M1 and the second surface M2 of the waveguide plate 1, and the coupling-out structure 12 expands the pupil of the light and couples out the waveguide plate 1. Among them, pupil expansion means that the spot diameter of the light emitted by the image source at the coupling-out structure 12 is greater than the spot diameter of the light incident at the coupling-in structure. Exemplarily, the out-coupling structure 12 includes at least 10 mutually parallel splitting surfaces 120, the interval thickness of adjacent splitting surfaces 120 is less than or equal to 1 mm, and the splitting surfaces 120 have a certain preset angle α with the first surface M1 and the second surface M2 of the waveguide plate 1. The range of the preset angle can be 15 preset angles, and can also be reasonably adjusted according to the light output angle, which is not limited in the embodiments of the present application.

[0024] Different from the existing array optical waveguide technology, all the splitter surfaces 120 in the outcoupling structure 12 provided in the embodiment of the present application do not contain any coating material, and the splitter surface 120 is formed by superimposing two transparent substrates with a certain roughness and then using molecular bonding. The splitter surface 120 couples the light out of the waveguide sheet 1 into the user's pupil by reflection.

[0025] Among them, molecular bonding refers to the process of forming chemical bonds between different atoms or the same atoms by sharing or differentiating their respective electrons. The present application can use methods such as superimposing and pressing two transparent substrates with a certain roughness, vacuuming, heat treatment, chemical treatment, etc. to achieve molecular bonding between two transparent substrates. The embodiments of the present application do not limit the method of molecular bonding between the two transparent substrates.

[0026] Optionally, the surface roughness of the transparent substrate is less than or equal to 10 nm. Figure 2 The entire optical waveguide device looks completely transparent. Although it seems that there is no splitter surface 120, the microscopic physical characteristics of the bonding interface between the two transparent substrates actually produce a low reflectivity, which is very low in both small and large angle ranges. In this way, the problem of dark bands and mirror stray light caused by coating on the out-coupling splitter surface in the existing array optical waveguide can be solved. In addition, since the splitter surface 120 of the present application has no coating layer, there is no obvious microscopic defect caused by polishing at the junction of the waveguide plate 1 surface and the splitter surface 120, thereby solving the problem of smearing.

[0027] For example, taking K9 glass as a transparent substrate, it is tested that the surface roughness of two K9 glass substrates is about 0.5nm, and the bonding interface can produce a reflectivity of about 0.02%. Taking into account the low reflectivity, in order to improve the light efficiency, while ensuring the pupil expansion range, the embodiment of the present application can improve the light output efficiency of the coupling structure 12 by reducing the thickness of the transparent substrate and increasing the number of splitter surfaces 120. It has been verified that a transparent substrate with a thickness of 0.35mm is used to make the splitter surface 120, and the coupling structure 12 contains at least ten or more splitter surfaces 120 arranged in parallel and spaced apart from each other. The light output efficiency of the optical waveguide device can reach 50nit / lm, and there are no problems of dark bands, smearing and mirror stray light, and it has good display color and brightness uniformity.

[0028] Among them, "nit" is the unit of brightness, the full name is "cd / m^2", which is used to measure the brightness of the virtual display screen seen by the human eye. "lm" is the unit of luminous flux, the full name is "lumen", which is used to measure the intensity of the light source coupled into the optical machine. In the embodiment of the present application, "nit / lm" is used to represent the optical efficiency of the waveguide.

[0029] Optional, reference Figure 2, the multiple splitting surfaces 120 in the out-coupling structure 12 are parallel to each other and are arranged at equal intervals. Exemplarily, the light that is totally reflected after being coupled into the waveguide plate 1 by the coupling structure 11 passes through the splitting surfaces 120 in turn, about 0.02% of the light is reflected by the splitting surfaces 120 and then coupled out of the waveguide plate 1, and the remaining light passes through the splitting surfaces 120 to reach the next splitting surface 120, and is split by the splitting surfaces 120 in turn and then coupled out of the waveguide plate 1, thereby achieving pupil expansion and out-coupling of the light.

[0030] Optionally, the optical waveguide device further includes an anti-reflection film 14, which is located on the first surface M1 and / or the second surface M2 for light coupling out. In other words, the anti-reflection film 14 can also be plated on the first surface M1 and / or the second surface M2 of the waveguide plate 1, and the anti-reflection wavelength range of the anti-reflection film 14 is in the visible light range, so that the light output efficiency of the output light can be improved. According to tests, a light transmittance of more than 98% can be achieved, and the appearance looks completely like transparent glass.

[0031] Furthermore, the existing array optical waveguide technology usually has a coating on the outcoupling reflective surface, which will cause mirror stray light and limit the field of view angle of the pupil expansion direction of the beam splitter to a maximum of 56°. The technical solution provided in the embodiment of the present application can solve the problem of mirror stray light, which means that a larger field of view angle can be supported.

[0032] Optionally, the thickness of the transparent substrate used in the present application is less than or equal to 0.05 mm. The present application uses a thinner transparent substrate and more splitter surfaces 120 to achieve higher light efficiency. For example, the 0.35 mm thick transparent substrate in this embodiment is changed to a 0.05 mm thick transparent substrate. After testing, the light efficiency can be improved to 350 nit / lm. In addition, it was verified that the higher the refractive index of the transparent substrate, the higher the reflectivity of the bonding interface. To further improve the light efficiency, high-refractive materials can also be used, such as optical glass with a refractive index greater than 1.7.

[0033] Considering that, when the reflectivity of the splitter surface 120 provided in the embodiment of the present application is fixed, multiple splitter surfaces 120 are parallel to each other and arranged at intervals. After the light passes through each splitter surface 120 in turn, the higher the reflectivity of the splitter surface 120, the faster the intensity of the totally reflected light decays, which leads to the problem of decreased uniformity.

[0034] To solve this problem, the embodiment of the present application may also solve the problem by using a gradual change in the intervals of the light splitting surface 120 . Figure 3 for Figure 2 A schematic cross-sectional view of another optical waveguide device provided along the AA' direction, referring to Figure 3The out-coupling structure 12 includes a first out-coupling region 121, a second out-coupling region 122 and a third out-coupling region 123 which are sequentially arranged away from the in-coupling structure 11, and the intervals between the multiple splitting surfaces 120 in the first out-coupling region 121 are greater than the intervals between the multiple splitting surfaces 120 in the second out-coupling region 122; the intervals between the multiple splitting surfaces 120 in the second out-coupling region 122 are greater than the intervals between the multiple splitting surfaces 120 in the third out-coupling region 123.

[0035] Specifically, refer to Figure 3 , the area where the out-coupling structure 12 is located can also be called the out-coupling area. Along the direction away from the coupling-in structure 11, which can also be understood as the total reflection transmission direction of the light in the waveguide plate 1, the out-coupling area can be divided into three areas. The first out-coupling area 121 is close to the coupling-in structure 11. The area contains multiple splitting surfaces, and the intervals between the splitting surfaces 120 are large; the second out-coupling area 122 is located on the side of the first out-coupling area 121 away from the coupling-in structure 11. The area contains multiple splitting surfaces 120, and the intervals between the splitting surfaces 120 are small; the third out-coupling area 123 is located on the side of the second out-coupling area 122 away from the coupling-in structure 11. The area contains multiple splitting surfaces 120, and the intervals between the splitting surfaces 120 are the smallest. The present application can optimize the brightness uniformity of the waveguide plate 1 by changing the number of splitting surfaces 120 per unit area. It should be noted that the area division depends on the specific design.

[0036] In other embodiments, the light splitting surface 120 may be continuously and gradually changed. Figure 3 , the intervals between the multiple light splitting surfaces 120 in the out-coupling structure 12 gradually decrease along the direction away from the coupling-in structure 11. It can also be understood that the first out-coupling region 121, the second out-coupling region 122 and the second out-coupling region 122 are adjacent, and the light splitting surfaces 120 in the three are parallel to each other and the farther away from the coupling-in structure 11, the smaller the intervals between the light splitting surfaces 120. When the brightness uniformity is sufficient, the zoning process may not be required.

[0037] Based on the above embodiments, Figure 3 , the multiple splitting surfaces 120 of at least one of the first outcoupling region 121, the second outcoupling region 122, and the second outcoupling region 122 are arranged at equal intervals. In other words, only one, two, or three of the first outcoupling region 121, the second outcoupling region 122, and the second outcoupling region 122 may be optimized to improve the brightness uniformity of the waveguide sheet 1.

[0038] Figure 4 for Figure 2 A schematic cross-sectional view of another optical waveguide device provided along the AA' direction, referring to Figure 2 , Figure 3-Figure 4, the coupling structure 11 provided in the embodiment of the present application includes a prism structure or a reflector coupling structure. For example, referring to Figure 2 and Figure 3 The coupling structure 11 may be a prism structure as an example, or may be a structure such as Figure 4 The reflector coupling structure 11 is shown. In other embodiments, the coupling structure 11 may also be a periodically arranged grating structure, and the grating structure may be a one-dimensional grating, a two-dimensional grating, a straight tooth grating, a slanted tooth grating, etc. The above embodiments do not represent the application scope of the present technical solution, and more embodiments are not listed one by one in the embodiments of the present application.

[0039] Among them, the optical waveguide device provided in the embodiment of the present application is not limited to one-dimensional array optical waveguides, but can also be applied to two-dimensional array optical waveguides or other types of near-eye display devices.

[0040] In summary, the optical waveguide device provided in the embodiment of the present application abandons the design concept of using coating for the splitter surface of the existing array waveguide, and adopts a transparent substrate whose surface is not coated with any other material for bonding to form a splitter surface of the coupling structure, which can solve the problems of dark bands, smearing and mirror stray light in the array optical waveguide display. By encrypting the intervals of the splitter surfaces away from the coupling, uniformity optimization can be achieved, thereby improving the display effect and reducing the cost.

[0041] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and the features of the various embodiments of the present invention may be combined with each other in part or in whole, and may cooperate with each other in various ways and be technically driven. It is possible for those skilled in the art to make various obvious changes, readjustments, combinations and substitutions without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An optical waveguide device, characterized in that: Including waveguide; The waveguide plate comprises a coupling-in structure and a coupling-out structure, wherein the waveguide plate has a first surface and a second surface which are parallel to each other, the coupling-in structure is arranged on the waveguide plate, and the coupling-out structure is arranged between the first surface and the second surface; The coupling-in structure is used to couple the light emitted by the image source into the waveguide plate, so that the light is transmitted to the coupling-out structure by total reflection between the first surface and the second surface; The outcoupling structure comprises a plurality of splitting surfaces, which are formed by superimposing two transparent substrates without any dielectric coating and then molecularly bonding, the splitting surfaces are parallel to each other and arranged at intervals, and the splitting surfaces have a preset angle with the first surface and the second surface of the waveguide plate; The out-coupling structure is used to expand the pupil of the light and couple out the waveguide.

2. The optical waveguide device according to claim 1, characterized in that The multiple light splitting surfaces in the outcoupling structure are arranged at equal intervals.

3. The optical waveguide device according to claim 1, characterized in that Along the direction away from the coupling-in structure, the intervals between the multiple light-splitting surfaces in the coupling-out structure gradually decrease.

4. The optical waveguide device according to claim 1, characterized in that The coupling-out structure comprises a first coupling-out region, a second coupling-out region and a third coupling-out region which are sequentially arranged away from the coupling-in structure; The intervals between the multiple splitting surfaces in the first outcoupling region are greater than the intervals between the multiple splitting surfaces in the second outcoupling region; the intervals between the multiple splitting surfaces in the second outcoupling region are greater than the intervals between the multiple splitting surfaces in the third outcoupling region.

5. The optical waveguide device according to claim 4, characterized in that: The first outcoupling region, the second outcoupling region, and a plurality of light splitting surfaces of at least one of the first outcoupling region are arranged at equal intervals.

6. The optical waveguide device according to claim 1, characterized in that Also includes anti-reflection coating, The anti-reflection film is located on the first surface and / or the second surface of the light outcoupling.

7. The optical waveguide device according to claim 1, characterized in that The coupling-in structure comprises a prism structure or a reflector coupling-in structure.

8. The optical waveguide device according to claim 1, characterized in that The surface roughness of the transparent substrate is less than or equal to 10 nm.

9. The optical waveguide device according to claim 1, characterized in that: The thickness of the interval between adjacent light-splitting surfaces is less than or equal to 1 mm.

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