An optical waveguide device

Abstract

The present invention discloses an optical waveguide device. The waveguide sheet includes an input coupling structure and an output coupling structure. The waveguide sheet has a first surface and a second surface that are parallel to each other. The input coupling structure is disposed on the waveguide sheet, and the output coupling structure is disposed between the first surface and the second surface. The input coupling structure is configured to couple the light emitted from the image source into the waveguide sheet, so that the light is totally reflected between the first surface and the second surface and transmitted to the output coupling structure. The output coupling structure includes a plurality of beam splitting surfaces. The beam splitting surfaces are formed by molecular bonding after two transparent substrates without any dielectric coating are stacked. The beam splitting surfaces are parallel to each other and spaced apart. The beam splitting surfaces have a preset angle with the first surface and the second surface of the waveguide sheet. The output coupling structure is configured to expand the pupil of the light and couple the light out of the waveguide sheet. It can solve the problems of dark bands, ghosting, and mirror stray light in the array waveguide display, improve the yield, and reduce the production cost.

Description

Technical Field

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

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

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

[0004] Currently, AR optical waveguides are mainly divided into array optical waveguides and diffractive optical waveguides from the perspective of optical principles. Different types of AR optical waveguides have differences in performance, cost, application scenarios, etc. Currently, there are representative products of these two different types of optical waveguides on the market. Among them, the array optical waveguide is significantly superior to the diffractive optical waveguide in terms of display effects such as single-chip full color, color reproducibility, and low backlight leakage rate. However, there are still problems such as dark bands, ghosting, 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 diffractive optical waveguide, the light transmittance of the display area is significantly lower than that of the non-display area, usually about 85%, which affects the aesthetics.

[0005] In the existing array optical waveguide, light is coupled into the optical waveguide through refraction and reflection, and is totally reflected and transmitted in the optical waveguide. The coupled-out part uses an array beam-splitting surface with a dichroic coating to partially reflect and couple out the totally reflected light beam into the human eye, and the other part continues to be totally reflected and transmitted, thereby realizing pupil expansion. The coupled-out beam-splitting surface has a dichroic coating, which is usually covered on the waveguide substrate by a coating method. Its reflectivity needs to be specially designed. In order to ensure brightness uniformity for multiple coupled-out beam-splitting surfaces, multiple film systems are usually required. As Figure 1 shown, the film system has a certain reflectivity within a specific angle range, and chromatic aberration needs to be strictly controlled, otherwise there will be color deviation in the display. In addition, the reflectivity needs to be reduced within a large angle range to reduce the problems of dark bands and mirror stray light, which brings great difficulty to the coating design and cannot be completely solved. To achieve better color uniformity for the film system, multiple film materials usually need to be designed, and the film layer thickness is at least several hundred nanometers. The surface polishing of the waveguide finished product will cause microscopic defects at the junction of the coating and the waveguide surface, resulting in ghosting and stray light in the display. Dark bands and ghosting are currently the problems that plague the array optical waveguide. In addition, the waveguide sheet needs to be thinned to reduce weight. The thinner the waveguide sheet, the more coupled-out beam-splitting surfaces are required, and the higher the cost of the waveguide sheet. 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, ghosting, and mirror stray light in arrayed waveguide displays.

[0007] In a first aspect, an embodiment of the present invention provides an optical waveguide device, including a waveguide sheet;

[0008] The waveguide sheet includes an input coupling structure and an output coupling structure. The waveguide sheet has a first surface and a second surface that are parallel to each other. The input coupling structure is disposed on the waveguide sheet, and the output coupling structure is disposed between the first surface and the second surface;

[0009] The input coupling structure is configured to couple the light emitted from the image source into the waveguide sheet, so that the light is totally reflected between the first surface and the second surface and transmitted to the output coupling structure;

[0010] The output coupling structure includes a plurality of beam splitting surfaces. The beam splitting surfaces are formed by molecular bonding after two transparent substrates without any dielectric coatings are stacked. The beam splitting surfaces are parallel to each other and spaced apart. The beam splitting surfaces have a preset angle with the first surface and the second surface of the waveguide sheet; The output coupling structure is configured to expand the pupil of the light and couple the light out of the waveguide sheet.

[0011] Optionally, the plurality of beam splitting surfaces in the output coupling structure are equally spaced.

[0012] Optionally, along the direction away from the input coupling structure, the spacing between the plurality of beam splitting surfaces in the output coupling structure gradually decreases.

[0013] Optionally, the output coupling structure includes a first output coupling region, a second output coupling region, and a third output coupling region that are sequentially arranged away from the input coupling structure;

[0014] The spacing between the plurality of beam splitting surfaces in the first output coupling region is greater than the spacing between the plurality of beam splitting surfaces in the second output coupling region; The spacing between the plurality of beam splitting surfaces in the second output coupling region is greater than the spacing between the plurality of beam splitting surfaces in the third output coupling region.

[0015] Optionally, the plurality of beam splitting surfaces in at least one of the first output coupling region, the second output coupling region, and the second output coupling region are equally spaced.

[0016] Optionally, an anti-reflection film is further included, and the anti-reflection film is located on the first surface and / or the second surface where the light is coupled out.

[0017] Optionally, the input coupling structure includes a prism structure or a mirror input coupling structure.

[0018] Optionally, the surface roughness of the transparent substrate is less than or equal to 10 nm.

[0019] Optionally, the spacing thickness between adjacent beam splitting surfaces is less than or equal to 1 mm.

[0020] The optical waveguide device provided by the embodiment of the present invention abandons the design idea of coating the beam splitting surface of the existing array waveguide, and uses a transparent substrate without coating any other material for bonding to form the beam splitting surface of the coupling-out structure, which can solve the problems of dark bands, ghosting and mirror stray light in array optical waveguide displays. The light transmittance can reach 98% to solve the aesthetics problem, improve the yield and reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments read with reference to the accompanying drawings:

[0022] Figure 1 It is a diagram of the film system relationship of the dichroic coating on the beam splitting surface in the prior art;

[0023] Figure 2 It is a top view schematic diagram of an optical waveguide device provided by an embodiment of the present application;

[0024] Figure 3 For Figure 2 It is a cross-sectional schematic diagram of another optical waveguide device provided along the AA' direction in

[0025] Figure 4 For Figure 2 It is a cross-sectional schematic diagram of another optical waveguide device provided along the AA' direction in DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the purpose, technical solutions and advantages of the present invention clearer, the following will combine the accompanying drawings in the embodiments of the present invention to completely describe the technical solutions of the present invention through specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the protection scope of the present invention.

[0027] Embodiment

[0028] The embodiment of the present invention provides an optical waveguide device. Figure 2 It is a top view schematic diagram of an optical waveguide device provided by 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 sheet 1, the waveguide sheet 1 includes an input structure 11 and an output structure 12, and the waveguide sheet 1 has a first surface M 1 and a second surface M 2 , the input structure 11 is arranged on the waveguide sheet 1, and the output structure 12 is arranged on the first surface M 1 and the second surface M 2Therebetween. The coupling-in structure 11 is disposed on the waveguide sheet 1. The coupling-in structure 11 is configured to couple the light emitted from the image source into the waveguide sheet 1, so that the light is totally reflected between the first surface M 1 and the second surface M 2 and transmitted to the coupling-out structure 12 through total internal reflection.

[0029] Wherein, Figure 2 Figure (a) in [reference] is a top view of the optical waveguide device, Figure 2 and figure (b) in [reference] is a cross-sectional view of the optical waveguide device along the AA' direction.

[0030] Specifically, referring to Figure 2 , the overall waveguide sheet device is made of a transparent material. The length and thickness of the waveguide sheet 1 can be set according to the needs of the actual scenario. For example, when applied to AR glasses, the length should be adapted to the wearer, and the thickness should not be too large. The first surface M of the waveguide sheet 1 and the second surface M 2 are parallel to each other and have at least one coupling-in structure 11 and one coupling-out structure 12. The image source (not shown in the figure) is configured to emit light carrying image information and can be applied to virtual imaging of AR glasses, etc. The coupling-in structure 11 can couple the light into the waveguide sheet 1 through reflection, refraction, or other means and then perform total internal reflection transmission. The coupling-out structure 12 is responsible for pupil expansion and coupling out the light into the human eye.

[0031] Total internal reflection (TIR) is an optical phenomenon. When light travels from a medium with a higher refractive index to 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 lower refractive index medium.

[0032] In the optical waveguide scenario provided by the embodiments of the present application, the refractive index of the waveguide sheet 1 is greater than the refractive index of air. After the light is coupled into the waveguide sheet 1 through the coupling-in structure 11, the light that satisfies total internal reflection propagation is transmitted in the waveguide sheet 1 to the coupling-out structure 12. The coupling-out structure 12 includes a plurality of beam splitting surfaces 120. The beam splitting surfaces 120 are formed by molecular bonding after two transparent substrates are stacked. The beam splitting surfaces 120 are parallel to each other and spaced apart. The beam splitting surfaces 120 have a preset angle with the first surface M of the waveguide sheet 1 and the second surface M 2 and expand the pupil of the light and couple out the waveguide sheet 1. The pupil expansion means that the spot diameter of the light emitted from the image source at the coupling-out structure 12 is larger than the spot diameter at the coupling-in structure. Exemplarily, the coupling-out structure 12 includes at least 10 or more parallel beam splitting surfaces 120. The spacing thickness between adjacent beam splitting surfaces 120 is less than or equal to 1 mm. The beam splitting surfaces 120 have a preset angle with the first surface M of the waveguide sheet 1 and the second surface M 2It has a certain preset included angle α, and the range of this preset included angle can be 15 (for the preset included angle), or it can be reasonably adjusted according to the light output angle, and the embodiments of the present application do not limit it.

[0033] Different from the existing array optical waveguide technology, all the light splitting surfaces 120 in the light coupling out structure 12 provided in the embodiments of the present application do not contain any coating materials. The light splitting surface 120 is formed by stacking two transparent substrates with a certain roughness and then bonding them with molecular bonds. The light splitting surface 120 couples out the light from the waveguide sheet 1 into the user's pupil by reflection.

[0034] Among them, molecular bonding refers to the process in which different atoms or the same atoms form chemical bonds by sharing or differentiating their respective electrons. In the present application, the molecular bonding of two transparent substrates can be realized by means such as stacking and pressing two transparent substrates with a certain roughness, evacuating, heat treatment, chemical treatment, etc. The embodiments of the present application do not limit the way of molecular bonding between the two transparent substrates.

[0035] Optionally, the surface roughness of the transparent substrate is less than or equal to 10 nm. Refer to Figure 2 , the appearance of the entire optical waveguide device looks completely transparent. Although there seems to be no light splitting surface 120 at all, in fact, the microscopic physical characteristics of the bonding interface between the two transparent substrates will generate a relatively low reflectivity, and this reflectivity is very low in both the small angle range and the large angle range. In this way, the problems of dark bands and mirror image stray light caused by coating on the light coupling out light splitting surface in the existing array optical waveguide can be solved. In addition, since there is no coating layer on the light splitting surface 120 of the present application, there are no obvious microscopic defects caused by polishing at the junction of the surface of the waveguide sheet 1 and the light splitting surface 120, so the smear problem can be solved.

[0036] Exemplarily, taking the transparent substrate made of K9 glass as an example, after testing, the surface roughness of two K9 glass substrates is about 0.5 nm, and the bonding interface can generate a reflectivity of about 0.02%. Considering the low reflectivity, in order to improve the light efficiency, under the condition of ensuring the pupil expansion range, the embodiments of the present application can increase the light output efficiency of the light coupling out structure 12 by reducing the thickness of the transparent substrate and increasing the number of light splitting surfaces 120. It has been verified that when using a transparent substrate with a thickness of 0.35 mm to make the light splitting surface 120, the light coupling out structure 12 has at least ten or more light splitting surfaces 120 arranged in parallel at intervals. The light output efficiency of this optical waveguide device can reach 50 nit / lm, and there are no problems of dark bands, smear and mirror image stray light, and at the same time, it has good display color and brightness uniformity.

[0037] Among them, "nit" is the unit of luminance, and its full name is "candela per square meter (cd / m^2)", which is used to measure the luminance of the virtual display screen seen by the human eye. "lm" is the unit of luminous flux, and its full name is "lumen", which is used to measure the intensity of the light source coupled into the optical engine. In the embodiments of the present application, "nit / lm" is used to represent the optical efficiency of the waveguide plate.

[0038] Optionally, referring to Figure 2 , the multiple light splitting surfaces 120 in the light extraction structure 12 are parallel to each other and arranged at equal intervals. Exemplarily, the light rays that are totally reflected after being coupled into the waveguide plate 1 through the light coupling structure 11 sequentially pass through the light splitting surfaces 120, and about 0.02% of the partial light rays are reflected by the light splitting surfaces 120 and then extracted from the waveguide plate 1, and the remaining light rays pass through the light splitting surfaces 120 to reach the next light splitting surface 120, and are sequentially split by the light splitting surfaces 120 and then extracted from the waveguide plate 1, so as to realize the pupil expansion and extraction of the light rays.

[0039] Optionally, the optical waveguide device further includes an anti-reflection film 14, and the anti-reflection film 14 is located on the first surface M 1 and / or the second surface M 2 , that is to say, an anti-reflection film 14 can also be coated on the first surface M 1 and / or the second surface M 2 of the waveguide plate 1. The anti-reflection wavelength range of the anti-reflection film 14 is the visible light range, so that the light extraction efficiency of the outgoing light rays can be improved. After testing, a light transmittance of more than 98% can be achieved, and it looks completely like transparent glass in appearance.

[0040] Furthermore, in the existing array optical waveguide technology, a film is usually coated on the light extraction and reflection surface, which will cause mirror stray light and limit the maximum field of view angle of 56° in the pupil expansion direction of the light splitting surface. The technical solution provided by the embodiments of the present application can solve the problem of mirror stray light, which means that a larger field of view angle can be supported.

[0041] 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 light splitting surfaces 120 to achieve higher optical 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 optical efficiency can be increased to 350 nit / lm. In addition, it is verified that the higher the refractive index of the transparent substrate, the higher the reflectivity of the bonding interface. To further improve the optical efficiency, a high-refractive index material can also be used, such as an optical glass with a refractive index greater than 1.7.

[0042] Considering that when the reflectivity of the light splitting surface 120 provided by the embodiments of the present application is fixed, the multiple light splitting surfaces 120 are parallel to each other and arranged at intervals, and after the light rays sequentially pass through each light splitting surface 120, the higher the reflectivity of the light splitting surface 120, the faster the light intensity attenuation of the totally reflected light rays, and there is a problem of decreased uniformity.

[0043] To solve this problem, the embodiment of the present application can also adopt a gradually changing interval of the light splitting surface 120 to solve it. Figure 3 For Figure 2 FIG. is a schematic cross-sectional view of another optical waveguide device provided along the AA' direction in [reference], Figure 3 , the coupling-out structure 12 includes a first coupling-out region 121, a second coupling-out region 122, and a third coupling-out region 123 that are sequentially arranged away from the coupling-in structure 11. The interval between multiple light splitting surfaces 120 in the first coupling-out region 121 is greater than the interval between multiple light splitting surfaces 120 in the second coupling-out region 122; the interval between multiple light splitting surfaces 120 in the second coupling-out region 122 is greater than the interval between multiple light splitting surfaces 120 in the third coupling-out region 123.

[0044] Specifically, referring to Figure 3 , the region where the coupling-out structure 12 is located can also be referred to as the coupling-out region. Along the direction away from the coupling-in structure 11, which can also be understood as along the total reflection transmission direction of light in the waveguide sheet 1, the coupling-out region can be divided into three regions. The first coupling-out region 121 is close to the coupling-in structure 11, and this region contains multiple light splitting surfaces with a relatively large interval between the light splitting surfaces 120; the second coupling-out region 122 is located on the side of the first coupling-out region 121 away from the coupling-in structure 11, and this region contains multiple light splitting surfaces 120 with a relatively small interval between the light splitting surfaces 120; the third coupling-out region 123 is located on the side of the second coupling-out region 122 away from the coupling-in structure 11, and this region contains multiple light splitting surfaces 120 with the smallest interval between the light splitting surfaces 120. The present application can optimize the brightness uniformity of the waveguide sheet 1 by changing the number of light splitting surfaces 120 per unit area. It should be noted that the region division depends on the specific design.

[0045] In other embodiments, a continuously gradually changing interval of the light splitting surfaces 120 can also be adopted. Continuing to refer to Figure 3 , along the direction away from the coupling-in structure 11, the interval between multiple light splitting surfaces 120 in the coupling-out structure 12 gradually decreases. It can also be understood that the first coupling-out region 121, the second coupling-out region 122, and the second coupling-out region 122 are adjacent, and the light splitting surfaces 120 in the three are parallel to each other and the interval of the light splitting surfaces 120 becomes smaller as it is farther away from the coupling-in structure 11. When the requirement for brightness uniformity is sufficient, the partition processing may not be required.

[0046] On the basis of the above embodiments, referring to Figure 3, a plurality of light splitting surfaces 120 of at least one of the first output region 121, the second output region 122, and the second output region 122 are equally spaced. That is to say, it is also possible to optimize only one, two, or three of the first output region 121, the second output region 122, and the second output region 122 to improve the brightness uniformity of the waveguide sheet 1.

[0047] Figure 4 is Figure 2 a schematic cross-sectional view of another optical waveguide device provided along the AA' direction in [reference], Figure 2 , Figures 3 - 4 , the coupling structure 11 provided in the embodiments of the present application includes a prism structure or a mirror coupling structure. Exemplarily, referring to Figure 2 and Figure 3 , the coupling structure 11 can be an exemplary prism structure, or a mirror coupling structure 11 as shown in Figure 4 . In other embodiments, the coupling structure 11 can also be a periodically arranged grating structure, and the grating structure can be a one-dimensional grating, a two-dimensional grating, a straight-tooth grating, a helical-tooth grating, etc. The above embodiments do not represent the application scope of the technical solution of the present application. For more embodiments, the embodiments of the present application will not be listed one by one.

[0048] Among them, the optical waveguide device provided in the embodiments of the present application is not limited to a one-dimensional array optical waveguide, and can also be applied to a two-dimensional array optical waveguide or other types of near-eye display devices, etc.

[0049] In summary, the optical waveguide device provided in the embodiments of the present application abandons the design idea of coating the light splitting surface of the existing array waveguide, and uses a transparent substrate without coating any other material to bond to form the light splitting surface of the coupling structure, which can solve the problems of dark bands, ghosting, and mirror stray light in array waveguide displays. By encrypting the spacing of the light splitting surfaces far from the coupling, the uniformity can be optimized, the display effect can be improved, and the cost can be reduced at the same time.

[0050] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. The features of the various embodiments of the present invention can be partially or fully combined with each other, and can cooperate with each other in various ways and be driven technically. Various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope 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. Without departing from the concept of the present invention, more other equivalent embodiments can be included, 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 at least ten or more splitter surfaces, wherein the splitter surfaces are formed by superimposing two transparent substrates without any dielectric coating and then molecularly bonding, the splitter surfaces are parallel to each other and arranged at intervals, and the splitter surfaces have a preset angle with the first surface and the second surface of the waveguide plate; wherein the interval thickness between adjacent splitter surfaces is less than or equal to 1 mm; 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.

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