WO2019144596A1

WO2019144596A1 - Optical waveguide structure and display device

Info

Publication number: WO2019144596A1
Application number: PCT/CN2018/099467
Authority: WO
Inventors: 戴杰; 郭帮辉; 阮望超
Original assignee: 华为技术有限公司
Priority date: 2018-01-26
Filing date: 2018-08-08
Publication date: 2019-08-01
Also published as: CN110082907B; CN110082907A

Abstract

Provided are an optical waveguide structure and a display device, which are used for solving the problem in the prior art of difficulty in inhibiting stray light in an augmented reality waveguide. The optical waveguide structure comprises an upper-layer waveguide, a lower-layer waveguide, and a first beam splitting layer between the upper-layer waveguide and the lower-layer waveguide. The upper-layer waveguide comprises a first upper surface, a first lower surface, and a second beam splitting film array between the first upper surface and the first lower surface, wherein the second beam splitting film array comprises at least two wavelength splitting films; the at least two wavelength splitting films form an acute angle with the first lower surface; and the at least two wavelength splitting films are used for reflecting light of at least three wavebands of visible light, with the light of the remaining wavebands passing therethrough, the at least three wavebands being wavebands for projection imaging. The lower-layer waveguide comprises a second upper surface and a second lower surface, the second upper surface being parallel to the second lower surface. The first beam splitting layer is used for reflecting part of incident light, with the remainder passing therethrough.

Description

Optical waveguide structure and display device

The present application claims priority to Chinese Patent Application No. 201810078000.1, filed on Jan. 26, 2018, the entire disclosure of which is incorporated herein by reference. in.

Technical field

The present application relates to the field of optical technologies, and in particular, to an optical waveguide structure and a display device.

Background technique

Augmented reality (AR) technology is a new technology that integrates real world information and virtual world information "seamlessly". It is an entity information that is difficult to experience in a certain time and space of the real world (such as : visual information, three-dimensional appearance, sound, taste, touch, etc.), through optical, computer, electronic, etc., after simulation and superposition, not only shows the real world information, but also displays the virtual information at the same time, two kinds of information Replenish and superimpose each other. In visual augmented reality, users use optical display devices to combine real world and virtual images to form an immersive visual experience combining virtual and real.

The laminated reflective waveguide shown in Fig. 1 is a widely used AR waveguide implementation. Referring to Fig. 1, the laminated reflective waveguide is provided with a spectral film array capable of reflecting a part of incident light and transmitting a part thereof. Taking the incident light a as an example, after incident on the laminated reflective waveguide, it is reflected by the optical path b to the optical splitting film array, wherein a part of the light is reflected by the optical path c to the human eye, and another part of the light is transmitted through the optical path d, and the transmitted light continues to move forward. Propagation, each time separation occurs when the spectroscopic film array is incident, a part of the light is reflected to the human eye along the optical path defgh, and a part of the light is reflected to the human eye along the optical path defgij, and these rays are normal rays. However, after the light e is incident on the spectroscopic film array, a part of the light is reflected and reflected along the optical path k-l-m to the human eye, and the outgoing direction of the light m is deflected, which causes imaging deviation after being incident on the human eye, and this part of the light is stray light. In the prior art, the above-mentioned stray light is difficult to suppress.

Summary of the invention

The present application provides an optical waveguide structure and a display device for solving the problem in the prior art that it is difficult to suppress stray light in an AR waveguide.

In a first aspect, the present application provides an optical waveguide structure including an upper layer waveguide, a lower layer waveguide, and a first beam splitting layer between the upper layer waveguide and the lower layer waveguide. The upper waveguide includes a first upper surface, a first lower surface, and a second beam splitting film array between the first upper surface and the first lower surface, the first upper surface and the first lower surface Parallel to the surface, the second beam splitting film array comprises at least two wavelength splitting films, the at least two wavelength splitting films being parallel to each other and forming an acute angle with the first lower surface, the at least two wavelength splitting The film is configured to reflect light in at least three bands of visible light, and the remaining bands are transmitted, wherein the at least three bands are bands for projection imaging, for example, the at least three bands are respectively in a red spectrum One band, one band in the green spectrum, and one band in the blue spectrum. The lower waveguide includes a second upper surface and a second lower surface, the second upper surface being parallel to the second lower surface. Both sides of the first light splitting layer are in contact with the first lower surface and the second upper surface, respectively, and the first light splitting layer is for reflecting a part of incident light and transmitting the remaining part.

In the above optical waveguide structure, the side end of the lower layer waveguide can receive the projection light, and after the projection light is incident on the first beam splitting layer, the first beam splitting layer divides the projection light into two parts, and a part of the light passes through the first beam splitting layer and enters the upper layer waveguide. And after being incident on the second beam splitting film array, reflected back to the lower layer waveguide, exiting from the second lower surface and finally entering the human eye; another portion of the projected light separated by the first beam splitting layer is reflected back to the second lower surface, and is passed through the second The lower surface is reflected back to the first beam splitting layer and continues to be separated by the first beam splitting layer. When the projected light propagates in the above optical waveguide structure, there is less stray light. Moreover, the first light splitting layer only needs to reflect a part of the incident light to be partially transmitted, which has low process difficulty and low cost; otherwise, if the first light splitting layer is bonded by optical glue, the characteristics of the first light splitting layer are easy. The optical glue that is bonded is not required to have a very high refractive index, and the optical glue has a low cost.

In some optional implementations of the first aspect, the first beam splitting layer comprises a beam splitting film or a grating array. The spectroscopic film may be a light intensity splitting film, a polarizing beam splitting film, or the like.

In some optional implementations of the first aspect, the first beam splitting layer is configured to: transmit 90% to 99% of the light having an incident angle in the range of 0° to θ ₁ , 10% to 1% Partial reflection, and 5% to 20% of the light having an incident angle in the range of θ ₁ to 90° is partially transmitted, 95% to 80% is partially reflected, and θ _{1 is} greater than 0° and less than 90°. The technical solution can control the energy of the stray light to an extremely low level, and can enable the projected light to be emitted from a wider range of the second lower surface of the lower layer waveguide, thereby improving the display effect of the light emitted from the second lower surface of the lower layer waveguide. . Furthermore, the above-described angle selection characteristic of the first light splitting layer can also significantly improve the field of view (FOV) of the optical waveguide, thereby improving the user's viewing immersion.

In some optional implementations of the first aspect, the upper waveguide has a refractive index equal to a refractive index of the lower waveguide, and reduces stray light formed by a refractive index deviation between the upper waveguide and the lower waveguide.

In some optional implementation manners of the first aspect, the first light splitting layer is a light splitting film, and a splitting ratio of the one light splitting film is changed from small to large along a first direction; or The first light splitting layer includes at least two light splitting films, and a splitting ratio of the adjacent two light splitting films close to the first side end of the lower layer waveguide is not larger than a light splitting film of the second side end of the lower layer waveguide a splitting ratio; or, the first light splitting layer includes at least two light splitting films, and a spacing distance between two adjacent light splitting films varies from large to small along the first direction; or, the first The light splitting layer is a grating array, and the energy ratio of the 0th-order reflected light of the grating array varies from large to small along the first direction, and/or the diffraction efficiency of the effective diffraction order of the grating array is along The first direction changes from small to large; wherein the first direction is a direction in which the first side end points toward the second side end. The change in the spectral ratio of the above-mentioned spectral film can be realized based on a change in the thickness, refractive index, and the like of the spectral film.

In the above technical solution, the transmittance of the first light splitting layer to the light varies from small to large along the lateral propagation direction of the projected light in the lower waveguide, and the light emitted from the second lower surface near the incident side end of the projection light can be reduced. The energy so as not to be too strong, and to increase the energy of the light emerging from the second lower surface away from the incident side end position of the projection light so that it is not too weak to be emitted from different positions of the lower waveguide The energy of light is more balanced, improving the imaging effect of the emitted light.

In some optional implementations of the first aspect, the first upper surface of the upper waveguide and/or the second lower surface of the lower waveguide are further provided with an anti-reflection film to enhance the first upper surface and/or the second lower surface Transmittance rate.

In an alternative design, the second beam splitting film array in the upper layer waveguide of the first aspect is replaced with a reflective film array to reduce the cost of the yellow waveguide structure.

In a second aspect, the present application provides a display device comprising: a frame, an optical waveguide structure in the first aspect or any alternative implementation thereof, and a projection module. The optical waveguide structure and the projection module are fixed on the frame, and the projection module is configured to inject the projection light into the lower layer waveguide, the projection light comprising light in at least three bands, such as red, blue and green light.

In the above display device, after the projection light generated by the projection module is incident on the lower layer waveguide 120, it can be separated by the first light splitting layer 130, and finally exits from the second lower surface 122 at a plurality of positions to enter the human eye, and the ambient light can be from the first The surface enters the upper waveguide 110 and finally emerges from the second lower surface 122, and is superimposed with the projection light emitted from the second lower surface 122 to achieve an augmented reality effect, and the display device can effectively increase the FOV of the projected light and can effectively suppress the impurity. The generation of astigmatism.

In some optional implementations of the second aspect, the display device further includes: a first light homogenizing layer, including a first light homogenizing film disposed on the second lower surface or disposed under the lower layer waveguide and fixed on the a first light homogenizing sheet on the frame, the transmittance of the first light homogenizing layer is changed from small to large along a first direction, and the first direction is a first side end of the lower layer waveguide The direction of the second side end of the lower layer waveguide. The change in transmittance of the first uniform light film or the first light homogenizer can be achieved based on changes in shape, thickness, refractive index, and the like. The first light homogenizing layer can make the light intensity of the projected light entering the human eye more uniform.

In some optional implementation manners of the second aspect, the display device further includes a second light homogenizing layer, where the first light homogenizing layer is disposed on the first upper surface a light homogenizing film or a second light homogenizing sheet disposed above the upper waveguide and fixed on the frame, the transmittance of the second light homogenizing layer being changed from large to small along the first direction. The second light concentrating layer can compensate for the influence of the first light concentrating layer on the ambient light distribution, so that the ambient light incident on the human eye is more balanced.

In some optional implementations of the second aspect, the display device further includes a coupling out waveguide below the second lower surface and fixed to the frame for receiving, propagating, and outputting from the second The light emitted from the surface. The coupled out waveguide can change the optical path, and is convenient for designing products such as AR glasses. In addition, the coupled-out waveguide is a single-layer waveguide having a thickness smaller than that of the upper-layer waveguide and the formed double-layer waveguide structure. Since a single-layer coupled-out waveguide is used to emit light to the user, the light can be significantly emitted directly from the lower-layer waveguide to the user. Reduce the thickness at which the user views the image. Furthermore, by transforming the optical path of the lower layer wave to derive the ray by coupling out the waveguide, the ambient light incident by the upper waveguide can be viewed through the coupled waveguide to realize the augmented reality based on the potential.

In some optional implementations of the second aspect, the coupling out waveguide includes a coupling grating disposed on a third upper surface of the coupling out waveguide facing the second lower surface for The light received by the second lower surface is coupled into the coupling out waveguide. The structure is simple to implement and the effect of coupling the light into the grating is better.

In some optional implementations of the second aspect, the coupling out waveguide includes a first surface and a second surface, wherein the first surface is configured to receive light emitted by the second lower surface and receive Light is transmitted to the second surface, the second surface is for totally reflecting light transmitted through the first surface, the first surface is located on a surface of the coupling out waveguide, the second surface Located on a surface or interior of the coupled-out waveguide, the first surface is not parallel to the second surface. The above-mentioned coupling waveguide uses its own film layer to couple the light into the interior, and the light coupling structure can be omitted without additional light, and the effect of coupling the light into the grating is better.

In some optional implementations of the second aspect, when the second surface is located on the surface of the coupling out waveguide, one of the first surface and the second surface is a wedge surface or is provided with The optical structure of the wedge surface.

In some optional implementations of the second aspect, the coupling-out waveguide includes a coupling-out grating disposed at a waveguide wall of the coupling-out waveguide, and the coupling coupling is performed to propagate the coupling-out waveguide A portion of the light exiting the grating exits the wall of the waveguide and the other portion reflects. The above-mentioned coupling out waveguide has a simple structure for emitting light, and the effect of emitting light is better.

Optionally, the energy ratio of the 0-level reflected light of the coupled-out grating varies from large to small along the propagation direction of the light in the coupled-out waveguide, and/or the diffraction efficiency of the effective diffraction order of the coupled-out grating is along The direction of propagation of light within the coupled out waveguide is small to large. The above-mentioned coupling-out grating can make the energy of the light emitted therefrom more balanced and improve the viewing experience of the user.

In some optional implementations of the second aspect, the coupling out waveguide includes a third beam splitting film array disposed inside the coupling out waveguide, and the third beam splitting film array is configured to be coupled into the waveguide A portion of the propagating light incident on the third beam splitting film array is reflected to the waveguide wall of the coupled-out waveguide, and the remaining portion is transmitted. The above-mentioned coupling out waveguide has a simple structure for emitting light, and the effect of emitting light is better.

Optionally, in the plurality of light splitting films of the third light splitting film array, the transmittance of the light splitting film near the light incident from the lower waveguide is coupled to the waveguide, and the light splitting from the lower waveguide is incident on the waveguide. The transmittance of the film is large. The third spectroscopic film array can balance the energy of the light emitted from the coupled wave and improve the viewing experience of the user.

DRAWINGS

1 is a schematic view of a prior art optical waveguide structure;

2 is a schematic view showing a wavelength range of reflected light of a prismatic film;

3 to 4 are schematic views of an optical waveguide structure in an embodiment of the present application;

5a-5b are schematic diagrams showing possible implementation manners of a first light splitting layer in an embodiment of the present application;

6 is a schematic diagram of propagation of projection light in an embodiment of the present application;

7a-7d are schematic diagrams of propagation of ambient light in an embodiment of the present application;

FIG. 8 is a schematic diagram of a display device according to an embodiment of the present application; FIG.

9-10 are schematic views of possible implementations of a display device;

11a-11d are schematic structural views of a coupling out waveguide.

Detailed ways

The plurality referred to in the present application means two or more. In addition, in the description of the present application, the terms "first", "second" and the like are used for the purpose of distinguishing the description, and are not to be construed as indicating or implying a relative importance, and are not to be construed as indicating or implying the order. The term “and/or” in the present application is merely an association relationship describing an associated object, indicating that there may be three relationships, for example, A and/or B, which may indicate that A exists separately, and A and B exist simultaneously. There are three cases of B.

In the prior art, in order to suppress the stray light shown in FIG. 1, a surface-sensitive reflective film is coated on the surface of the spectroscopic film array, and the reflective film can reflect about 10% of the incident light at a small incident angle, which is large. 95 to 99% transmission of incident light at incident angle. The characteristic of the transmission film that transmits most of the incident light at a large incident angle can reduce the stray light caused by the reflection of the light e incident on the spectral film array through the optical path k in FIG. However, high transmission angle and high transmission are very difficult to achieve, and the incident angle sensitive reflective film is expensive, and a high refractive index optical glue is required to adhere the reflective film to the spectral film array. The process cost of optical glue is also very high.

In order to facilitate understanding of the technical solutions provided by the present application, some concepts are first introduced below.

The optical waveguide, which is simply referred to as a waveguide in the embodiment of the present application, is a medium device that guides light waves to propagate therein. The waveguide includes upper and lower surfaces. When the light in the waveguide is incident on the upper and lower surfaces of the waveguide, if the incident angle is greater than the critical angle, the light is totally reflected at the interface between the waveguide surface and the air, and the critical angle depends on the refractive index of the waveguide.

The light-splitting film is a film that can reflect a part of incident light and partially transmit it to separate the light into two parts. According to different splitting modes, the spectroscopic film includes a wavelength splitting film, a light intensity splitting film, a polarization splitting film, and the like.

A wavelength splitting film is a film that divides light into two parts according to a wavelength region. For example, after the light is incident on the wavelength splitting film, the wavelength splitting film reflects light having a wavelength in the first range, and the remaining portion transmits. It should be noted that the wavelength splitting film is not limited to reflecting light in a continuous bandwidth (see the left side of FIG. 2), and it is also possible to reflect a plurality of spaced narrow-band light rays in the spectrum (see the right side of FIG. 2).

The light intensity splitting film divides the incident light into two parts: the emitted light and the transmitted light according to a certain light intensity ratio. For example, a light intensity splitting film can reflect light of 10% of the intensity of incident light, and the remaining 90% of the light is transmitted.

The polarization beam splitting film is a film that separates the parallel direction component of the light from the vertical component.

A grating array comprising a plurality of parallel slits of equal width and equal spacing can be made for a large number of parallel indentations engraved on the glass sheet. The grating array can reflect a portion of the incident light back and the remainder is diffracted.

It should be understood that the above-mentioned beam splitting film or grating separates the light, and the sum of the separated reflected light and the transmitted light may be smaller than the energy of the incident light, because the energy of the light may be absorbed by the splitting film or the grating, resulting in Energy loss.

The light homogenizer, also known as the light homogenizing plate, is a light guide plate. Due to the size, shape and density of the homogenizer, the intensity distribution of the light changes after a beam of light passes through the homogenizer.

The uniform film is a light-transmissive film. Due to variations in the thickness and refractive index of the uniform film, the intensity distribution of the light after passing through the uniform film can also be changed.

FIG. 3 and FIG. 4 illustrate an optical waveguide structure 100 according to an embodiment of the present application, wherein FIG. 4 is a schematic diagram of components of the optical waveguide structure 100 when they are phase separated. Referring to FIGS. 3 and 4, the optical waveguide structure 100 includes an upper waveguide 110, a lower waveguide 120, and a first light splitting layer 130 between the upper waveguide and the lower waveguide.

The upper waveguide 110 includes a first upper surface 111, a first lower surface 112, and a second beam splitting film array 113. The first upper surface 111 is parallel to the first lower surface 112, and the second spectral film array 113 includes two or more wavelength splitting films. The wavelength splitting films are parallel to each other and form an acute angle with the first lower surface 112. An angle, wavelength splitting film is used to reflect light in at least three bands of visible light, and the remaining bands are transmitted, wherein the at least three bands are bands for projection imaging, such as a wavelength reflective film for use in red light spectrum One band, one band in the green spectrum, and one band in the blue spectrum reflect light in the rest of the spectrum. In some embodiments, referring to FIG. 3, both ends of the wavelength splitting film are respectively connected to the first upper surface 111 and the first lower surface 112. In other embodiments, the two ends of the wavelength splitting film may not be in contact with the first upper surface 111 and the first lower surface 112. One possible implementation of the upper waveguide 110 is an optical glass or resin optical component (such as a commercial optical plain film) having a certain thickness (for example, 0.5 to 5 mm, the thickness of different layers may be equal or not equal). , window, etc.), after precision grinding and polishing (up and down plane parallelism is less than 1 centimeter) and plating the above-mentioned wavelength spectroscopic film (such as metal film, dielectric film or grating structure), by optical glue bonding or direct photo-gluing, and then press Cutting at a certain angle (between 10° and 45°), and then performing precision grinding and polishing on the cut surface (the parallelism of the upper and lower planes is less than 1 cent), forming an upper waveguide structure containing the laminated wavelength splitting film. It should be understood that FIG. 3 shows a segment of the waveguide structure. The number of wavelength splitting films in the second beam splitting film array 113 in the upper layer waveguide 110 is not limited to two as shown in FIG. 3, and may be more, for example, FIG. The number of wavelength splitting films taken out was four.

The lower layer waveguide 120 includes a parallel second upper surface 121 and a second lower surface 122. One possible implementation of the lower layer waveguide 120 is an optical glass or resin optical part (such as a commercial one) which has a certain thickness (for example, 0.5 to 20 mm) and is subjected to precision polishing (up and down plane parallelism of less than 1 cent.). The optical waveguide, the window, and the like are formed. The material of the lower waveguide 120 may be the same as or different from the upper waveguide 110. The refractive index of the lower waveguide 120 may be the same as or similar to the refractive index of the upper waveguide 110.

The first light splitting layer 130 may be a light splitting film or a grating array. The spectroscopic film included in the first spectroscopic layer 130 may be a light intensity splitting film or a polarizing beam splitting film. Hereinafter, the light intensity spectroscopic film will be described as an example. When the first light splitting layer 130 is a light intensity splitting film, there may be various implementation manners. For example, the first light splitting layer 130 is a light intensity splitting film, or the first light splitting layer 130 is formed by multiple light intensity splitting films. As shown in FIG. 5a, the plurality of light intensity splitting films may be spliced together. As shown in FIG. 5b, the plurality of light intensity splitting films may not be spliced together, and a distance between adjacent light intensity splitting films is provided. In the following, the first spectroscopic layer is used as a spectroscopic film as an example for description.

The first light splitting layer 130 is disposed between the first lower surface 112 and the second upper surface 121, and the two surfaces of the first light splitting layer 130 are in contact with the first lower surface 112 and the second upper surface 121, respectively. The first light splitting layer 130 may be adhered to the first lower surface 112 or the second upper surface 121 by optical glue, or the first lower surface 112, the first light splitting layer 130, and the second may be physically squeezed. The upper surface 121 is pressed together, for example, the upper waveguide 110, the first beam splitting layer 130, and the lower layer waveguide 120 may be fixed together by a fixing member such as a jig.

Referring to FIG. 6, the projection light may be coupled from the side end of the lower layer waveguide 120 into the lower layer waveguide 120, wherein after the light beam a1 is incident on the first beam splitting layer 130, a portion of the light is transmitted along the optical path b1 to the upper layer waveguide 110, and is incident on the upper layer waveguide 110. The second beam splitting film array 113 is reflected back to the lower layer waveguide 120 along the optical path c1 and exits from the second lower surface 122 of the lower layer waveguide 120. The other portion d1 of the projection light a1 is reflected by the first light-splitting layer 130 to the second lower surface 122 of the lower-layer waveguide 120, and is totally reflected back to the first light-splitting layer 130 along the e1, and e1 is incident on the first light-splitting layer 130, and continues to occur. Separating, a part of the light is emitted from the second lower surface 122 of the lower layer waveguide 120 along the optical path f1-g1, and the other portion is reflected by the first light-splitting layer 130 along the optical path h1, and continues to propagate in the lower layer waveguide 120. Similarly, after the projection light a2 is incident on the lower layer waveguide, multiple separations occur in the first beam splitting layer 130, which can be along the optical paths a2-b2-c2, a2-d2-e2-f2-g2, a2-d2-e2-h2- I2-j2-k2 is emitted from the second lower surface 122 of the lower layer waveguide 120. In addition, light emitted from the second lower surface 122 of the lower waveguide 120 (e.g., d1, d2, g1, g2, k2, etc.) may be refracted by the difference in refractive index between the lower waveguide 120 and the air. In order to realize that the light entering the upper waveguide 110 can be reflected by the second spectral film array 113, the wavelength of the projected light is required to be within the wavelength range of the reflected light of the wavelength splitting film of the second spectral film array 113, or a second is required. The wavelength range of the reflected light of the wavelength splitting film of the spectral film array 113 can cover the wavelength range of the projected light. In addition, in order to realize that the reflected light formed by the projection light entering the first beam splitting layer 130 in the lower layer waveguide can be totally reflected on the second lower surface 122, the incident angle of the projected light may be greater than the critical angle at which the second lower surface 122 is totally reflected.

In the optical waveguide structure 100, the first beam splitting layer 130 is used to separate the projection light incident from the lower layer waveguide 120. The separated projection light partially enters the upper layer waveguide 110 and is reflected back to the lower layer waveguide 120 through the second beam splitting film array 113. And exiting from the second lower surface 122 of the lower layer waveguide 120, another portion of the projection light separated by the first beam splitting layer 130 is reflected back to the second lower surface 122 of the lower layer waveguide 120, and is reflected back to the first beam splitter via the second lower surface 122. Layer 130, first beam splitting layer 130 continues to separate the light. When the projected light propagates in the optical waveguide structure 100 described above, there is less stray light. In addition, the first light-splitting layer 130 only needs to reflect a part of the incident light, and the process is low in difficulty and low in cost; otherwise, if the first light-splitting layer 130 is bonded by optical glue, the first light-splitting layer 130 is The characteristics are easy to implement, and it is not required to have an extremely high refractive index for the optical glue to which it is bonded, and the optical glue has a low cost.

As an optional design, the first beam splitting layer 130 is capable of transmitting 90% to 99% of the light having an incident angle in the range of 0° to θ ₁ , and partially reflecting from 10% to 1%, and The incident angle is partially transmitted by 5% to 20% of the light in the range of θ ₁ to 90°, and partially reflected by 95% to 80%, and θ _{1 is} larger than 0° and smaller than 90°. For the implementation of the foregoing angle selection feature, reference may be made to various existing technical means, and the embodiments of the present application are not described in detail.

In the embodiment of the present application, θ ₁ may be set to be greater than 45°, and then the projection light in the lower waveguide 120 is incident on the first spectroscopic layer 130 at an incident angle of a larger angle (greater than θ ₁ ), and a part of the first spectroscopic layer is transmitted through the first spectroscopic layer. The layer 130 enters the upper waveguide 110, is reflected by the second beam splitting film array 113, and enters the second beam splitting film array 113 at a small angle (less than θ ₁ ), and then most (90% to 99%) of the light passes through A light splitting layer 130 enters the lower layer waveguide 120 and exits from the second lower surface 122. Since most of the projection light reflected by the second beam splitting film array 113 can pass through the first light separating layer 130 and exit from the second lower surface, The light intensity loss is reduced, the brightness of the image is ensured, and the stray light formed by the first beam splitting layer reflecting the projection light reflected back from the second beam splitting film array is also suppressed, and the energy of the stray light is controlled to an extremely low level. In addition, since the first beam splitting layer 130 can reflect most of the projection light incident from the lower layer waveguide 120, the reflected projection light is continuously reflected back to the first beam splitting layer 130 to continue separation, thereby enabling the projected light to be guided from the lower layer waveguide. The second lower surface 122 of 120 exits within a wider range, increasing the display effect of light emitted from the second lower surface 122 of the lower waveguide 120.

Furthermore, the above-described angle selection characteristic of the first beam splitting layer can also significantly improve the field of view (FOV) of the optical waveguide. Referring to FIG. 6, the FOV is one of the key indicators of the AR optical waveguide, and the larger FOV can be more Close to the human eye's observation habits, improve immersion. The following is described in conjunction with Table 1 and Table 2. Table 1 shows the FOV related parameters of the conventional waveguide structure of Fig. 1.

Table 1

As shown in Table 1, the conventional structure shown in Fig. 1 has a half angle of view of θ' = 14.22 ° in the substrate when FOV = 50° and the refractive index of the substrate of the waveguide is 1.72. The maximum and minimum values of the incident angle e of the large-angle light at the light separation interface (i.e., the spectral film array in Fig. 1) satisfy: e _min ≥ h + t = 55.55 °; e _max = e _min + 2 · θ.

If e _min = 55.55°, then e _max = 84°. In order to transmit most of the energy in the large angle light from the light separation interface, a very small part (1%-3%) of the energy is reflected by the light separation interface to form stray light, and the light separation interface film layer is required to be e _min = 55.55 ° to e. High transmittance (97-99%) was maintained in the range of _max = 84°. In a conventional waveguide, as the FOV further increases, the angle e _max will also increase further. When e _max >85° or more, it is difficult to meet the coating requirements of the transmittance in the visible light wavelength range (400nm-700nm) higher than 97%-99%, and the stray light intensity increases with the reflectance. The rapid increase, the formation of strong ghosts, directly degraded the quality of the viewing under the large FOV. Therefore, since the light separation interface and the light reflection interface are the same interface and are not parallel to the upper and lower surfaces of the waveguide, the maximum and minimum angles of the large angle light are limited by the total reflection condition and the coating processing capability, respectively, and the FOV angle of the conventional waveguide shown in FIG. The theoretical upper limit is about 50°, which is difficult to continue to expand.

Table 2 shows one possible FOV related parameter of the waveguide structure of Figure 3.

Table 2

The double-layer optical waveguide structure 100 in the present application serves as the first light-splitting layer 130 of the light-separating interface and the upper and lower surfaces of the optical waveguide structure 100 (ie, the first upper surface 111 of the upper waveguide 110 and the second lower surface of the lower waveguide 120) 122) Parallel, so the angle t=0, and the first beam splitting layer 130 is separated from the second beam splitting film array 113 as a light reflecting interface. Therefore, the maximum and minimum limits of the incident angle of the light on the first beam splitting layer 130 are: e _min ≥ h = 35.55; e _max = e _min + 2 · θ.

When the FOV is 80°, the upper waveguide 110 and the lower waveguide 120 use a substrate having a refractive index of 1.72, and the half angle of view in the substrate is θ ₂ = 21.94°. Taking e _min >35.55=38.06°, then e _max =81.94°. After the light is totally reflected by the second lower surface 122 of the lower layer waveguide 120, after being incident on the first beam splitting layer 130, a small portion of the light (10%-20%) is transmitted into the upper layer waveguide 110, and most of the light is reflected back to the lower layer waveguide 120 for further transmission. By designing the angle between the second beam splitting film array 113 and the first lower surface 112 of the upper layer waveguide 110, it is ensured that the incident angle of the light reflected from the upper layer waveguide 110 back to the lower layer waveguide 120 at the first beam splitting layer 130 is less than 22°. When the first light splitting layer 130 satisfies the incident light transmittance of more than 99% in a small angle (0°-22°), the stray light in the entire FOV is less than 1%, and the characteristic has high achievability, for example, the first The light-splitting layer 130 is a partially reflective film, and the above characteristics are easily realized under the existing process conditions. Therefore, using the substrate of the same refractive index, the double-layer optical waveguide structure 100 provided by the present application can expand the FOV from 50° to 80° under the premise of depressing the ghost light energy, thereby improving the viewing experience of the user.

The following describes the propagation mode of ambient light (outside natural light) in the optical waveguide structure 100. Referring to FIG. 7a, the reflection spectrum range of the second beam splitting film array may cover only the wavelength range of the projected light, and the projection light includes three or more reference rays. The reference rays of the same intensity are superimposed to form white light. Therefore, the ambient light enters the upper waveguide 110 through the first upper surface 111 and enters the second spectral film array 113, and only a small portion of the light (wavelength and wavelength range of the projected light) The overlapping rays are reflected, and most of the remaining light passes through the second beam splitting film array 113. Since the effect of superimposing the reflected rays is white light, the imaging chromatic aberration of the light transmitted through the second beam splitting film array 113 can be ignored. The light passing through the second prism film array 113 is incident on the first light splitting layer 130. Since the incident angle is small (less than θ1), most of the ambient light passes through the first light splitting layer 130 into the lower waveguide 120, and from the second lower Surface 122 exits.

In the above implementation manner, ambient light may be emitted from the second lower surface 122 of the lower layer waveguide 120 through the optical waveguide structure 100 together with the projection light to form a real world image (natural light) and a virtual world image (projection light) to realize augmented reality. Features.

Optionally, the second spectroscopic film array has a reflection spectrum ranging from a plurality of narrow bands. Taking the red green blue (RGB) mode as an example, the spectral range of the projected light can be controlled in a narrow range, that is, the wavelength of the red light in the projected light occupies a narrow range in the entire red spectrum, and the projection light The wavelength of the green light occupies a narrow range in the entire green light spectrum, and the wavelength of the blue light in the projected light occupies a narrow range in the entire blue light spectrum, corresponding to the red light reflected by the wavelength splitting film in the second light splitting film array. The wavelength occupies a narrow range in the entire red spectrum, and the wavelength of the reflected green light occupies a narrow range in the entire green spectrum, and the wavelength of the reflected blue light occupies a narrow range in the entire blue spectrum. Therefore, in the ambient light, only a part of the red light, the blue light, and the green light are reflected by the second light splitting film array 113, and the deviation of the color and the intensity of the light transmitted through the second light splitting film array 113 is small or even negligible, thereby improving The optical waveguide structure 100 is used for display effects at the time of AR imaging.

Alternatively, the second beam splitting film array 113 may be replaced with a reflective film. Referring to Figures 7b through 7d, in this implementation, ambient light can also be incident from the first upper surface 111 and exit from the second lower surface 122. As shown in FIG. 7b, ambient light may not be incident on the reflective film, but may be incident directly on the first lower surface 112 of the upper waveguide 110, and then transmitted to the lower waveguide 120, and transmitted from the second lower surface 122 of the lower waveguide 120. As shown in FIG. 7c and FIG. 7d, although the ambient light is incident on the reflective film, after being reflected by the reflective film, the other reflective film may be incident again, and after being reflected by the reflective film, the first lower surface 112 of the upper waveguide 110 may be incident and transmitted. The lower waveguide 120 is transmitted from the second lower surface 122 of the lower waveguide 120.

In the above implementation manner, the wavelength splitting film in the upper layer waveguide 110 is replaced with a reflective film, the cost is further reduced, and the ambient light can still be incident from the first upper surface 111 and exit from the second lower surface 122 to realize the augmented reality AR. Features.

As an alternative design, the transmittance ratio (also referred to as transmittance) of the first light-splitting layer 130 to the incident light may be uneven, and may be as small as the projection light in the lateral propagation direction of the lower-layer waveguide 120. Large variation, referring to Fig. 6, the lateral propagation direction is the direction in which the left end of the lower waveguide (the projection light enters the side end of the lower waveguide) is directed to the right end of the lower waveguide. The implementation of the above light transmittance change can be:

Mode 1, the first light splitting layer is a light intensity splitting film, and the splitting ratio of the one light intensity splitting film changes from small to large along the first direction, and the splitting ratio refers to the transmittance and reflectance of the light splitting film to the incident light. The ratio. The first direction is the direction in which the first side end of the lower layer waveguide 120 is directed to the second side end. In the embodiment of the present application, the first side end is designed to receive the side end of the projection light, as shown in FIG. The left end of the waveguide 120 is a side end opposite to the first side end, such as the right end of the lower layer waveguide in FIG. It should be understood that, in the embodiment of the present application, the splitting ratio change of the spectroscopic film may have various implementation manners, for example, the thickness of the spectroscopic film changes from large to small along the first direction, or the refractive index of the spectroscopic film is along the first direction. Variations, other implementations of the change in the split ratio of the light intensity splitting film can be referred to various prior art means.

The second light splitting layer includes at least two light intensity splitting films, and the splitting ratio of the adjacent two light intensity splitting films close to the light intensity splitting film of the first side end of the lower layer waveguide is not larger than that of the lower layer waveguide. The split ratio of the light intensity splitting film at the second side end. Taking FIG. 5a or FIG. 5b as an example, the splitting ratio of the wavelength splitting film positioned at the right of the two adjacent wavelength splitting films is not smaller than the splitting ratio of the wavelength splitting film positioned at the left. In a possible implementation, the splitting ratio of each wavelength splitting film may be a fixed value, wherein the wavelength splitting film away from the first side end of the lower waveguide is relatively large; in another possible implementation, part or all of the wavelength The splitting ratio of the light splitting film itself varies from small to large along the first direction.

Mode 3, the first light splitting layer 130 includes at least two light intensity splitting films, and a spacing distance between two adjacent light intensity splitting films varies from large to small along the first direction. As shown in FIG. 5b, the spacing between the light intensity splitting films on the left side is large, and the spacing between the light intensity splitting films on the right side is small, so that the duty ratio of the light intensity splitting film is along the aforementioned first direction. Small to big changes.

In a fourth mode, the first light splitting layer is a grating array, and an energy ratio of the 0th-order reflected light of the grating array varies from large to small along the first direction, and/or effective diffraction of the grating array The order diffraction efficiency varies from small to large along the first direction. The implementation of variations in the energy ratio of the 0-order reflected light of the grating array and the variation of the diffraction efficiency of the effective diffraction order can be referred to various prior arts.

The benefits of the transmittance of the first beam splitting layer from small to large along the first direction are described below. It is assumed that the first spectroscopic layer 130 has a uniform transmittance to light incident at an incident angle in the range of 0 to θ ₁ of 10%, that is, after the light is incident on the first spectroscopic layer 130 at an incident angle in the range of 0 to θ ₁ . 10% of the energy is transmitted and 90% of the energy is reflected. Taking the light a2 shown in FIG. 6 as an example, assuming that the light energy is 100 units, after entering the first light splitting layer 130, 10 energy units of light are emitted through the optical path b2-c2, 100*90%*10%= Light of 9 energy units is emitted through the optical path d2-e2-f2-g2, and light of 100*90%*90%*10%=8.1 energy units is emitted through the optical path d2-e2-h2-i2-j2-k2 to This type of push. It can be seen that after a beam of light a2 is incident on the lower layer waveguide, the plurality of beams are separated into different positions from the second lower surface 122 of the lower layer waveguide 120, and the energy of the emitted light at different positions is different, which will affect the outgoing light. Imaging effect.

According to any one of the above aspects 1 to 4, the transmittance of the light incident on the incident angle of the first light-splitting layer 130 in the range of 0 to θ ₁ is small along the lateral direction of the projection light in the lower waveguide. With a large change, the energy of light emitted from the second lower surface 122 near the first side end position (lights c1, c2 in FIG. 6) can be reduced so as not to be too strong, and increased from the second lower surface The energy of the light emerging from the first side end position of 122 (such as light g1, g2, k2 in FIG. 6) is not too weak, so that the energy of light emitted from different positions of the lower layer waveguide 120 is more Balance, improve the imaging effect of the outgoing light.

As an alternative design, the first upper surface 111 of the upper waveguide 110 and/or the second lower surface 122 of the lower waveguide 120 are further provided with an anti-reflection film to enhance the first upper surface 111 and/or the second lower surface. Transmittance of 122.

FIG. 8 is a schematic diagram of a display device according to an embodiment of the present disclosure. The display device includes a frame 200, a projection module 300, and the optical waveguide structure 100. The projection module 300 and the optical waveguide structure 100 are fixed on the frame 200. The specific form is not limited. For example, the form of the frame 200 may be smart glasses or a helmet type display device. The projection module 300 is configured to generate projection light and to project the projection light into the lower layer waveguide 120.

As an optional design, referring to FIG. 9 , the display device further includes: a first light homogenizing layer 400, and the first light homogenizing layer 400 may be a first light homogenizing film disposed on the second lower surface 122, or may be A first light homogenizer disposed below the second lower surface. The transmittance of the first light-homogenizing layer varies from small to large along a first direction, which is a direction in which the first side end of the lower layer waveguide 120 is directed to the second side end of the lower layer waveguide.

In the optional design, after the projection light emitted from the first lower surface passes through the first light-homogenizing layer, the light intensity distribution changes, and the light intensity of the light near the first side end position of the lower layer waveguide 120 is relatively far from the lower layer waveguide 120. The light intensity of the light at the first end is weakened, and the same effect as that of the above-described modes 1 to 4 is achieved, so that the light intensity of the projection light entering the human eye is more uniform.

It should be understood that, when the first light-homogenizing layer 400 is disposed, the transmittance of the first light-splitting layer 130 may remain unchanged, and the first light-splitting layer 130 may be adopted in the manner described in the foregoing modes (1) to (4). The transmittance varies from small to large along the first direction, and the latter case can further enhance the balance of the energy of light emitted from different positions of the lower waveguide 120, and improve the imaging effect of the emitted light.

As an alternative design, with continued reference to FIG. 9, when the first light-homogenizing layer 400 is disposed, the display device further includes: a second light-homogenizing layer 500, and the second light-homing layer 500 may be disposed on the first upper surface 111. The second uniform light film on the top may also be a first light homogenizer disposed above the first upper surface 111. The transmittance of the second light-homogenizing layer 500 varies from large to small along the first direction.

Since the transmittance of the first light-homogenizing layer 400 near the first side end is small, the ambient light energy emitted from the first light-receiving layer 400 near the first side end is small, and therefore, the first uniform light Layer 400 can cause ambient light that is incident on the human eye to be unbalanced. The function of the second light homogenizing layer 500 is to reversely compensate the influence of the first light homogenizing layer 400 on the ambient light balance. As shown in FIG. 9 , the transmittance of the left side of the second light homogenizing layer 500 is high, and the right side is transparent. The ambient light energy incident on the left side of the upper waveguide 110 is stronger than the ambient light incident on the right side of the upper waveguide 110, and the ambient light emitted from the left side of the lower waveguide 120 to the first uniform light layer 400 is stronger than the ambient light. The energy of the ambient light emitted to the first light-homogenizing layer 400 on the right side of the lower layer waveguide, and the light of the ambient light transmitted from the first light-homogenizing layer 400 tends to be equalized after the light-homing treatment of the first light-homogenizing layer 400. It can be seen that by providing the second light-homogenizing layer 500, the intensity of the ambient light entering the user's eyes can be more balanced, and the imaging effect and the viewing experience of the user can be improved.

As an alternative design, referring to FIG. 10, the display device further includes a coupling out waveguide 600 for coupling out the light (projected light and natural light) emitted by the second lower surface 122 of the lower layer waveguide 120, coupled The waveguide 600 is internally propagated and exited for viewing by the user. The material of the coupling out waveguide 600 may be optical glass, or an optical resin or the like. The coupling out of the waveguide 600 can change the optical path, and is convenient for designing products such as AR glasses. In addition, the out-coupling waveguide 600 is a single-layer waveguide having a thickness smaller than that of the upper-layer waveguide 110 and the lower-layer waveguide 120. Since the single-layer coupled-out waveguide 600 emits light to the user, it is directly compared to the lower-layer waveguide 120. Leaving light to the user can significantly reduce the thickness at which the user views the image. Moreover, by changing the optical path of the light emitted from the lower waveguide 120 by coupling out the waveguide 600, the ambient light incident by the upper waveguide 110 can be viewed through the coupled waveguide 600, thereby realizing augmented reality based on the potential.

Figures 11a through 11d illustrate various possible modes of propagation of light in the outcoupled waveguide 600. The manner in which the light emitted from the lower layer waveguide 120 is coupled into the waveguide 600 includes:

Coupling Mode 1, Referring to Figure 11a, the coupling out waveguide 600 includes a coupling grating 610 for receiving the outgoing light of the lower waveguide, changing the direction of the received light to couple the received light into the out-coupling waveguide 600.

Coupling mode 2, referring to FIG. 11b to FIG. 11d, the coupling out waveguide 600 includes a first surface 630 and a second surface 640, wherein the first surface 630 is configured to receive the outgoing light of the lower waveguide and transmit the received light to the first Two sides 640, the second side 640 are used to totally reflect the light transmitted through the first face 630. The first surface 630 is located on the surface of the coupling out waveguide, and the second surface 640 may be located on the surface of the coupling out waveguide 600 (as shown in FIG. 11c, FIG. 11d), or may be located inside the coupling out waveguide 600 (as shown in FIG. 11b). The first surface 630 and the second surface 640 are not parallel. Optionally, when the second surface is located on the surface of the waveguide, the one of the first surface and the second surface is a wedge surface or is provided with an optical structure including a wedge surface.

The way in which the light propagating out of the waveguide 600 is emitted includes:

Exiting Mode 1, Referring to Figure 11a, the coupling out waveguide 600 includes a coupling-out grating 620 disposed in the waveguide wall for exiting a portion of the light that is coupled into the waveguide 600 and incident on the coupling grating 620 from the waveguide wall. Part of the reflection.

The exiting mode 2, referring to FIG. 11b to FIG. 11d, the coupling out waveguide 600 includes a third beam splitting film array 650 disposed inside the coupling out waveguide 600, and the third beam splitting film array 650 is used to transmit the in-coupling waveguide 600. A part of the light of the third light-sense film array 650 is reflected to the coupling-out waveguide wall to be emitted, and another part is transmitted. The light-splitting film in the third light-sense film array 650 may be a light intensity splitting film or a polarization beam splitting film.

Taking FIG. 11a as an example, the light emitted from the lower waveguide 120 enters the coupling grating 610 of the coupling out waveguide 600, and changes the direction of the side wall of the coupling out waveguide, and is totally reflected to the coupling disposed on the wall of the other side of the coupling out waveguide. A grating 620 is emitted, one part is emitted from the coupling-out grating 620, and the other part is reflected back to the inside of the waveguide 600 to continue to propagate. The light that continues to propagate continues to separate after being incident on the coupling grating again, and a part is emitted from the coupling-out grating 620, and the other part is emitted. Continue to propagate in the coupled out waveguide.

Optionally, the energy ratio of the 0th-order reflected light coupled out of the grating 620 varies from large to small along the propagation direction of the light in the coupled out waveguide 600, and/or the diffraction efficiency of the effective diffraction order of the coupled grating 620. The direction of propagation along the ray in the outcoupled waveguide 600 varies from small to large. The above-mentioned coupling-out grating 620 can make the energy of the light emitted therefrom more balanced and improve the viewing experience of the user.

Taking FIG. 11b to FIG. 11d as an example, the light emitted from the lower layer waveguide 120 is transmitted from the first surface 630 of the coupling out waveguide 600 to the second surface 640, and is totally reflected to the third beam splitting film array 650, and a part of the light is reflected to be small. The angle of incidence is coupled out of the sidewall of the waveguide and transmitted from the sidewall, and the other portion is transmitted through the third beam splitting film array 650 to continue to propagate in the coupled-out waveguide, and continues to separate after being incident on the third beam splitting film array 650 again, part of Light is projected from the side wall of the coupled-out waveguide through the third spectroscopic film array 650, and the other portion is transmitted through the third spectroscopic film array 650 to continue to propagate in the coupled-out waveguide.

Optionally, among the plurality of splitting films of the third beam splitting film array 650, the transmittance of the spectroscopic film near the position where the light is incident from the lower waveguide 120 and coupled to the waveguide 600 (or the first side end) is smaller, away from the light. The transmittance of the spectroscopic film at the position where the lower waveguide 120 is incident on the waveguide 600 (or the first side end) is large, for example, in the adjacent two spectral films of the third spectroscopic film array 650 of FIG. 11b, on the left side The transmittance of the spectroscopic film is not greater than the transmittance of the spectroscopic film on the right side. The third beam splitting film array 650 can balance the energy of the light emitted from the coupling out waveguide 600 and improve the viewing experience of the user.

It should be understood that, in addition to the manner shown in FIG. 11a to FIG. 11d, the coupling out waveguide 600 may have other implementation manners. For example, the coupling out waveguide may realize the coupling of the outgoing light of the lower layer waveguide 120 in the foregoing coupling manner 1 and is based on The aforementioned coupling out mode 2 realizes the emission of light. For another example, the coupling out waveguide can realize the coupling of the light emitted by the lower layer waveguide 120 in the aforementioned coupling mode 2, and realize the light emission based on the aforementioned coupling out mode 1.

The above-mentioned plurality of coupled-out waveguide structures are not only simple to implement, but also low in cost, and can emit light from a wide area, improve the area of the emitted light, and improve the imaging effect. Furthermore, the above-described coupled-out waveguide structure can effectively reduce The user views the thickness at the image position. Taking the structure shown in FIG. 11a as an example, the thickness at which the user views the image position is the thickness of the coupled waveguide, and the thickness is compared to the double-layer waveguide structure formed by the upper waveguide 110 and the lower waveguide 120. Significantly lower.

It should be understood that the display device illustrated in FIGS. 10 to 11d may also include the aforementioned first light-homogenizing layer 400 and/or second light-homogenizing layer 500, etc., which are not all shown in the drawings.

The above is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application, and should cover Within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

Claims

An optical waveguide structure, comprising: an upper layer waveguide, a lower layer waveguide, and a first beam splitting layer between the upper layer waveguide and the lower layer waveguide;

The upper waveguide includes a first upper surface, a first lower surface, and a second beam splitting film array between the first upper surface and the first lower surface, the first upper surface and the first The lower surface is parallel, the second beam splitting film array includes at least two wavelength splitting films, the at least two wavelength splitting films are parallel to each other, and form an acute angle with the first lower surface, the at least two wavelengths The light splitting film is configured to reflect light in at least three bands of visible light, and the remaining bands are transmitted, wherein the at least three bands are bands for projection imaging;

The lower waveguide includes a second upper surface and a second lower surface, the second upper surface being parallel to the second lower surface;

Both sides of the first light splitting layer are in contact with the first lower surface and the second upper surface, respectively, and the first light splitting layer is for reflecting a part of incident light and transmitting the remaining part.
The optical waveguide structure according to claim 1, wherein said first light splitting layer comprises a beam splitting film or a grating array for: 90% to 99% of light having an incident angle in the range of 0° to θ 1 Partial transmission, 10% to 1% partial reflection, and 5% to 20% of the light having an incident angle in the range of θ 1 to 90°, 95% to 80% partial reflection, θ 1 is greater than 0° and less than 90°.
The optical waveguide structure according to claim 1 or 2, wherein a refractive index of said upper waveguide is equal to a refractive index of said lower waveguide.
The optical waveguide structure according to claim 1 or 2, wherein:

The first light splitting layer is a light splitting film, and the splitting ratio of the one light splitting film changes from small to large along the first direction; or

The first light splitting layer includes at least two light splitting films, and the splitting ratio of the adjacent two light splitting films near the first side end of the lower layer waveguide is not larger than the light splitting near the second side end of the lower layer waveguide The split ratio of the film; or

The first light splitting layer includes at least two light splitting films, and a spacing distance between two adjacent light splitting films varies from large to small along the first direction; or

The first light splitting layer is a grating array, and an energy ratio of the 0th-order reflected light of the grating array varies from large to small along the first direction, and/or an effective diffraction order of the grating array The diffraction efficiency varies from small to large along the first direction;

The first direction is a direction in which the first side end points toward the second side end.
A display device, comprising:

frame;

The optical waveguide structure according to any one of claims 1 to 4, fixed to said frame;

a projection module fixed on the frame for injecting light in the at least three bands into the lower waveguide.
The display device according to claim 5, further comprising:

a first light homogenizing layer comprising a first light homogenizing film disposed on the second lower surface or a first light homogenizing sheet disposed under the lower layer waveguide and fixed on the frame, the first light homogenizing layer The transmittance varies from small to large along a first direction that is a direction in which the first side end of the lower waveguide points toward the second side end of the lower waveguide.
The display device according to claim 6, further comprising:

a second light homogenizing layer comprising a second light homogenizing film disposed on the first upper surface or a second light homogenizing sheet disposed above the upper waveguide and fixed on the frame, the second light homogenizing layer The transmittance varies from large to small along the first direction.
The display device according to any one of claims 5 to 7, further comprising:

A coupling out waveguide is located below the second lower surface and is fixed to the frame for receiving, propagating, and outputting light emitted from the second lower surface.
The display device according to claim 8, wherein said coupling-out waveguide comprises a coupling grating disposed on a third upper surface of said coupling-out waveguide facing said second lower surface for Light received by the second lower surface is coupled into the coupling out waveguide.
The display device according to claim 8, wherein the coupling out waveguide comprises a first surface and a second surface, wherein the first surface is for receiving light emitted by the second lower surface, and Receiving light transmitted to the second face, the second face for totally reflecting light transmitted through the first face, the first face being located on a surface of the coupled out waveguide, the second The face is located on a surface or inside of the coupled-out waveguide, and the first face is not parallel to the second face.
The display device according to claim 10, wherein when the second surface is located on a surface of the coupling out waveguide, one of the first surface and the second surface is a wedge surface or is provided with An optical structure with a wedge surface.
The display device according to any one of claims 8 to 11, wherein the coupling-out waveguide comprises a coupling-out grating disposed at a waveguide wall of the coupling-out waveguide for propagating the coupling-out waveguide A portion of the light incident on the out-coupling grating exits the waveguide wall and the other portion reflects.
The display device according to any one of claims 8 to 11, wherein the coupling-out waveguide comprises a third spectral film array disposed inside the coupling-out waveguide, and the third spectral film array is used for A portion of the light propagating through the waveguide and incident on the third beam splitting film array is reflected to the waveguide wall of the coupling out waveguide, and the remaining portion is transmitted.