Waveguide structure, binocular display module and method for switching monocular display and binocular display

Abstract

The invention provides a waveguide structure, a binocular display module and a method for switching monocular and binocular display, and relates to the technical field of AR, the waveguide structure comprises a waveguide substrate, at least one side of the waveguide substrate is provided with a thin film structure layer, the thin film structure layer comprises a first refractive index layer arranged on the waveguide substrate and a second refractive index layer arranged on the first refractive index layer, the electrochromism layer is arranged on the second refractive index layer and used for being connected with an electric control driving module, and the electric control driving module provides driving voltage for the electrochromism layer. The driving voltage state of the electrochromic layer is adjusted, so that the refractive index complex part (n + i * k) of the electrochromic layer is changed, the reflectivity and absorptivity of the waveguide substrate interface are changed, the waveguide substrate interface can be electrically switched between a transparent state and an absorption state, the pure electric control monocular and binocular switching function is achieved, independent and continuous adjustment of brightness of left and right eyes is achieved, and binocular brightness uniformity is improved. The purposes of integration, low power consumption and quick response are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of AR technology, in particular to a waveguide structure, a binocular display module and a method for switching between binocular display and monocular display. BACKGROUND

[0002] An AR (Augmented Reality) head-mounted display provides a visual fusion experience for users by superimposing virtual images on real scenes. The core display channel of the AR head-mounted display usually adopts a diffractive waveguide structure. The diffractive waveguide structure realizes multiple total reflection of light by introducing an in-coupling grating and an out-coupling grating in a high refractive index substrate, thereby obtaining a large field of view and a thin display effect.

[0003] In order to realize binocular display, the light path of a single light engine in a common AR display system is split and controlled by angles, and then the light path is introduced into left and right eye waveguide channels to form left and right images. However, the existing single light engine binocular waveguide system has the following outstanding problems: Firstly, the existing structure generally has a fixed light path, and the left and right eye waveguides simultaneously introduce light signals. It is impossible to selectively close a certain light channel as needed. If monocular display or light path interruption is needed, external liquid crystal shutters, mechanical shutters or polarization switches are usually used. Such devices have slow response, high power consumption and large thickness. When integrated with the waveguide, additional interface reflections and complex adjustments are introduced, which is not conducive to the realization of a lightweight AR optical module.

[0004] Secondly, the output optical path of the single light engine is long, and there are differences in diffraction efficiency and waveguide coupling angles, which often cause uneven brightness of the left and right eyes. Since the waveguide light guiding is a multiple total reflection process, the light energy is continuously attenuated during the propagation process, and the coupling and out-coupling efficiencies of different channels are significantly different, resulting in uneven brightness of the final human eye imaging. The traditional system is difficult to realize dynamic brightness compensation or local light energy distribution adjustment in the light path, which limits the binocular fusion effect and reduces the user's viewing experience.

[0005] Therefore, the existing single light engine binocular waveguide display system still lacks an effective technical solution that is simple in structure, fast in response, easy to integrate with the waveguide, and capable of realizing independent adjustment of the brightness of the left and right eyes and switching between binocular display and monocular display. This problem has become an important bottleneck restricting the further optimization and mass production of AR systems. SUMMARY

[0006] The purpose of the embodiments of the present application is to provide a waveguide structure, a binocular display module and a method for switching between binocular display and monocular display, which can realize the functions of monocular display and binocular display switching and left and right eye brightness adjustment, and have fast response speed, thin structure and low power consumption.

[0007] In an aspect of the embodiments of the present application, a waveguide structure is provided, comprising a waveguide substrate, at least one side of the waveguide substrate is provided with a thin film structure layer, the thin film structure layer comprises a first refractive index layer provided on the waveguide substrate, a second refractive index layer provided on the first refractive index layer, and an electrochromic layer provided on the second refractive index layer, the electrochromic layer is used to connect an electrically controlled driving module, the electrically controlled driving module provides a driving voltage to the electrochromic layer.

[0008] Optionally, the complex refractive index n ec of the electrochromic layer is n+i·k, where n is the refractive index of the electrochromic layer in a transparent state, k is an extinction coefficient, and k continuously changes with the applied driving voltage.

[0009] Optionally, the refractive index n g of the first refractive index layer is 1.0-1.3, and the thickness is 200-600 nm.

[0010] Optionally, the refractive index n H of the second refractive index layer is 1.8-2.4, and the thickness is about 40-150 nm.

[0011] Optionally, the waveguide substrate is provided with a coupling-in region and a coupling-out region, and the thin film structure layer is arranged between the coupling-in region and the coupling-out region.

[0012] Optionally, the waveguide substrate is further provided with a turning region, the thin film structure layer is arranged between the coupling-in region and the turning region, and / or the thin film structure layer is arranged on the other side of the waveguide substrate opposite to the turning region, and the projection of the thin film structure layer covers or partially covers the turning region.

[0013] Optionally, the thin film structure layer is arranged on the side of the waveguide substrate away from the grating.

[0014] Optionally, the material of the first refractive index layer comprises any one of SiO2, porous silicon oxide, magnesium fluoride, an air layer, or an organic polymer layer with low refractive characteristics; the material of the second refractive index layer comprises TiO2, HfO2, Ta2O5, ZnS, or any combination of stacked layer materials; and the material of the electrochromic layer comprises WO3, NiO, MoO3, V2O5, or a composite multi-layer structure thereof.

[0015] In another aspect of the embodiments of the present application, a binocular display module is provided, comprising: an optical-mechanical projection module, an electrically-controlled driving module, and the waveguide structure described above, at least two coupling-out areas are symmetrically arranged on the waveguide substrate of the waveguide structure, each of the coupling-out areas corresponds to one of the thin-film structure layers and one of the electrically-controlled driving modules, and the electrically-controlled driving module is connected with the electrochromic layer corresponding to the thin-film structure layer.

[0016] In still another aspect of the embodiments of the present application, a method for switching between binocular display and monocular display is provided, which adopts the binocular display module described above, and the method comprises: The electrochromic layer of the thin-film structure layer corresponding to the coupling-out area is controlled by the electrically-controlled driving module, so as to adjust the extinction coefficient k of the electrochromic layer to a preset value, and thus the brightness of the coupling-out area is reduced to a preset brightness interval.

[0017] The waveguide structure, the binocular display module, and the method for switching between binocular display and monocular display provided by the embodiments of the present application introduce the first refractive index layer, the second refractive index layer, and the electrochromic layer on at least one side of the waveguide substrate, change the refractive index complex part of the electrochromic layer by adjusting the driving voltage state of the electrochromic layer, and thus change the reflectivity and absorption of the interface of the waveguide substrate. In the transparent state, the reflectivity is high and the loss is low. In the colored state, the absorption is enhanced and the reflection is reduced. The light path can be electrically controlled to be turned on and off. The light path can be electrically switched between the transparent state and the absorption state. The purpose of selective transmission or cutoff of single-side light energy is achieved. The left and right waveguide regions can be independently controlled. The switching between binocular display and monocular display and the continuous adjustment of brightness are realized. The function of electrically controlled switching between binocular display and monocular display is realized. The left and right eyes can be independently and continuously adjusted. The uniformity of binocular brightness is improved. The display mode flexibility of the system is expanded. On the premise of not increasing the volume and complexity of the waveguide substrate, the purposes of integration, low power consumption, and fast response are achieved. BRIEF DESCRIPTION OF DRAWINGS

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

[0019] Figure 1 is one of the waveguide structure structure schematic diagrams provided by the embodiments of the present application; Figure 2 is the second waveguide structure structure schematic diagram provided by the embodiments of the present application; Figure 3 is the third waveguide structure structure schematic diagram provided by the embodiments of the present application; Figure 4 is the fourth waveguide structure structure schematic diagram provided by the embodiments of the present application; Figure 5 Figure 5 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 6 Figure 6 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 7 Figure 7 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 8 Figure 8 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 9 Figure 9 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 10 Figure 10 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 11 Figure 11 is a schematic diagram of a waveguide structure provided by the embodiment; Figure 12 Figure 12 is a schematic diagram of a waveguide structure provided by the embodiment. Figure 13 Figure 13 is a schematic diagram of a waveguide structure provided by the embodiment.

[0020] Figure 14 is a schematic diagram of a waveguide structure provided by the embodiment. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application.

[0022] In the description of the present application, it should be noted that the directions or position relationships indicated by the terms “inner”, “outer” and the like are based on the directions or position relationships shown in the drawings, or the directions or position relationships in which the products of the present application are usually placed, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms “first”, “second” and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0023] It should also be noted that, unless otherwise explicitly specified and limited, the terms “provided”, “connected” should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] In existing single-optical-mechanical binocular waveguide substrate systems, the left and right eye optical paths are simultaneously led out based on diffraction symmetry, making it impossible to close or open a single-sided optical path without adding mechanical or liquid crystal devices. Furthermore, the brightness difference in traditional waveguide substrate systems is caused by differences in optomechanical output power, diffraction efficiency, and light guide path length, and existing solutions lack adjustable means.

[0025] In view of this, and in response to the problems existing in the current single-optical binocular diffractive waveguide substrate display system, such as fixed structure, inability to switch between single and binocular light paths as needed, and uneven brightness between the left and right eyes, this application provides a waveguide structure, including: a waveguide substrate 10, a thin film structure layer disposed on at least one side of the waveguide substrate 10, the thin film structure layer including a first refractive index layer 11 disposed on the waveguide substrate 10, a second refractive index layer 12 disposed on the first refractive index layer 11, and an electrochromic layer 13 disposed on the second refractive index layer 12, the electrochromic layer 13 being used to connect an electronically controlled drive module, the electronically controlled drive module providing a drive voltage to the electrochromic layer 13.

[0026] like Figure 1 , Figure 2 As shown, the first refractive index layer 11, the second refractive index layer 12, and the electrochromic layer 13 are sequentially disposed on at least one side of the waveguide substrate 10.

[0027] Generally, this application provides an electrochromic loss resonant cavity structure with adjustable absorption characteristics on the light-emitting side of the waveguide substrate 10. Specifically, the electrochromic layer 13, together with the first refractive index layer 11 and the second refractive index layer 12, forms a thin film structure layer. By electrically controlling and adjusting the optical state of the electrochromic layer 13, the reflectivity and transmittance of light at the interface of the waveguide substrate 10 are dynamically controlled, thereby achieving the purpose of independently adjustable brightness for the left and right eyes and switching between single and binocular light paths.

[0028] The extinction coefficient k of the electrochromic layer 13 can be continuously varied. Combined with the first refractive index layer 11 and the second refractive index layer 12 with matching design, the single reflection loss of the system can be continuously adjusted in the range of low loss to high loss. Thus, grayscale adjustment is performed according to the brightness deviation of the left and right eyes to achieve dynamic balance of binocular brightness.

[0029] Specifically, an electrochromic layer 13 is provided to achieve electrically controlled absorption adjustment: an electrochromic layer 13 is provided on the outer surface of the waveguide substrate 10. The extinction coefficient k in the complex refractive index of the electrochromic layer 13 can continuously change under different applied voltages. In the transparent state, k≈0, and light absorption is almost nonexistent; in the colored state, k increases, and absorption is enhanced. By controlling the change in the driving voltage of the electrically controlled driving module, a continuous and controllable change in the extinction coefficient k of the electrochromic layer 13 can be achieved from low-loss transmission to high absorption cutoff.

[0030] In addition, the first refractive index layer 11 and the second refractive index layer 12 form an adjustable loss resonant cavity, and the first refractive index layer 11 (n g ≈1.0-1.3, and the thickness is about 200-600 nm) and the second refractive index layer 12 (n H ≈2.0, for example, between 1.8-2.4, and the thickness is about 40-150 nm) are sequentially arranged between the waveguide substrate 10 (refractive index n1≈1.8, for example, the refractive index n1 can be between 1.5-2.0, and the waveguide substrate 10 can even have a higher refractive index) and the electrochromic layer 13. The three layers form a single-side open optical cavity.

[0031] The first refractive index layer 11 is used to form an evanescent wave isolation zone to ensure that the light is basically fully reflected in the transparent state and to reduce light guiding loss; the second refractive index layer 12 is used to adjust the out-coupling loss rate and the cavity phase to realize the conversion of under-coupling and high reflection in the transparent state and critical coupling and high absorption in the colored state; the above arrangement enables the system to automatically complete the switching of reflection enhancement and reflection cancellation when the electrochromic layer 13 absorbs changes.

[0032] The rapid electrically controlled switching of monocular and binocular display can be realized: by arranging independent electrodes (electrically controlled driving modules) on the left and right eye regions, the coloring state of the electrochromic layer 13 on the corresponding side can be controlled to selectively turn off the light output of the waveguide substrate 10 on one side, thereby realizing the switching of monocular and binocular modes. Compared with the traditional mechanical or liquid crystal light valve scheme, the structure of the present application is simple, the response speed is fast, and the power consumption is low.

[0033] The brightness can be continuously adjusted and the binoculars can be balanced: the absorption changes of the electrochromic layer 13 can continuously adjust the reflection loss in the cavity in the range of 0.1%-80%, so as to finely control the single reflection loss without affecting the integrity of the light path. By adjusting the driving voltage of the electrically controlled driving module, the left and right eye light paths can be in different absorption states, the brightness compensation and balance can be realized, and the binocular fusion consistency and visual comfort can be significantly improved.

[0034] The waveguide substrate 10 process and thin film deposition process can be compatible: all layers can be realized by physical vapor deposition (PVD), atomic layer deposition (ALD), or sol-gel method, the film thickness can be controlled at the nanometer level, and the film can be directly integrated on the existing AR waveguide substrate 10 glass or polymer substrate without affecting the original diffraction grating structure and light guiding performance.

[0035] The application realizes the electrically controlled adjustment of the reflectivity and the absorption of the light exit area of the waveguide substrate 10 through the composite optical design of "first refractive index layer 11 + second refractive index layer 12 + electrochromic layer 13", so that the waveguide substrate 10 has the functions of single-doublet switchable and brightness adjustable, the brightness can be continuously adjustable in a wide range, the left-right eye brightness difference can be effectively compensated, the picture uniformity and visual comfort are improved, and a light-weight and high-response optical modulation scheme is provided for a single-light machine doublet AR system.

[0036] In summary, the waveguide structure provided by the embodiment of the application introduces the first refractive index layer 11, the second refractive index layer 12 and the electrochromic layer 13 on at least one side of the waveguide substrate 10, adjusts the driving voltage state of the electrochromic layer 13, changes the complex part (n + i·k, i is the imaginary unit) of the refractive index of the electrochromic layer 13, changes the reflectivity and the absorption of the interface of the waveguide substrate 10, the reflectivity is high and the loss is low in the transparent state; the absorption is enhanced and the reflectivity is reduced in the colored state, the electrically controlled opening and closing of the light path can be realized, the waveguide substrate 10 can be electrically switched between the transparent state and the absorption state, the purpose of selective transmission or cutoff of single-side light energy is achieved, the left and right waveguide regions can be independently controlled, the single-doublet display switching and the brightness continuous adjustment are realized, the single-doublet switching function is realized by pure electric control, the left and right eye brightness is independently and continuously adjusted, the doublet brightness uniformity is improved, and the display mode flexibility of the system is expanded, the purposes of integration, low power consumption and fast response are achieved on the premise of not increasing the volume and complexity of the waveguide substrate 10. The application directly integrates the thin film structure layer on one side of the waveguide substrate 10, realizes the reflectivity regulation of the light path, does not need to introduce additional light valves or polarization components, the response time can reach milliseconds, the film layer structure is simple, can be directly compatible with the existing waveguide packaging, the driving voltage is low, the power consumption is small, and is suitable for large-scale AR light machine packaging and mass production.

[0037] Further, the refractive index n g of the first refractive index layer 11 is 1.0-1.3, and the thickness is 200-600 nm. The material of the first refractive index layer 11 can be any one of SiO2, porous silicon oxide, magnesium fluoride, a vacuum deposition air gap (air layer) or an organic polymer layer with low refractive characteristics, so as to limit the penetration depth of the evanescent wave in the waveguide substrate 10, ensure that the waveguide light is almost fully reflected in the transparent state, and reduce unnecessary energy leakage.

[0038] The refractive index n HThe second refractive index layer 12 has a refractive index of 1.8-2.4 and a thickness of about 40-150 nm. The material of the second refractive index layer 12 is usually TiO2, HfO2, Ta2O5, ZnS or any combination of stacked materials thereof to achieve broadband loss adjustment at different wavelengths. The adjustment is achieved by sputtering, atomic layer deposition (ALD) or electron beam evaporation to adjust the reflection phase and the intensity of the out-coupling of the cavity, so that the system is in a high reflection state (under-coupling state) when the electrochromic layer 13 is in a transparent state, and reaches critical coupling when the electrochromic layer 13 is in a colored state, achieving maximum absorption.

[0039] The electrochromic layer 13 is the core control medium, and its complex refractive index n ec = n + i k, where n is the refractive index of the electrochromic layer 13 in the transparent state, and k is the extinction coefficient, which continuously changes with the driving voltage applied by the electrically controlled driving module.

[0040] For example, the complex refractive index is n ec = 1.5 + i k, k ≈ 0 in the transparent state, almost no absorption; 0.01 < k < 0.05 in the partial colored state, corresponding to different absorption levels; k ≈ 0.08-0.1 in the fully colored state, which can achieve strong absorption. Common materials include electrochromic oxides such as WO3, NiO, MoO3, V2O5 or composite multilayer structures thereof, which can be prepared by sputtering or chemical deposition.

[0041] The material of the waveguide substrate 10 is usually a glass or polymer waveguide substrate 10 (refractive index n1 ≈ 1.8) containing diffraction coupling-in and out structures inside. The guided light propagates in the waveguide substrate 10 by multiple total internal reflections at an angle of 40-55°. The waveguide substrate 10 layer also serves as the reflection interface basis of the entire light control structure.

[0042] The working principle of the present application is based on the principle of evanescent wave coupling and loss resonance cavity interference absorption. By adjusting the optical absorption coefficient of the electrochromic layer 13, the interface reflectivity of the waveguide substrate 10 is reversibly changed, thereby realizing controllable reflection and absorption of light energy. This principle can be used for single or binocular light path switching, as well as for continuous brightness adjustment.

[0043] Evanescent wave generation and isolation principle: when the high refractive index light in the waveguide substrate 10 is totally reflected on the interface of the waveguide substrate 10 at an incident angle θ, the light field is not completely confined inside the waveguide substrate 10, but forms an exponentially decaying evanescent wave in the first refractive index layer 11 outside the interface. The penetration depth δ of the evanescent wave is determined by the wavelength λ, the refractive index n1 of the waveguide substrate 10, the low refractive index n g and the incident angle θ, and the formula is: ; The evanescent wave represents the energy coupling ability of the optical field in the waveguide substrate 10 to the outside environment. If there is an absorbing medium in the evanescent wave action range, the optical energy will be transmitted and absorbed through the tunneling effect, thereby generating reflection loss. The present application is to design the first refractive index layer 11 with a thickness of about 3-3.5 times the penetration depth δ, so that the evanescent wave energy is basically attenuated (low loss) in the transparent state, and the absorption is enhanced by the electrochromic layer 13 in the colored state, so that the tunneling energy is significantly consumed (high loss).

[0044] Loss resonant cavity formation principle: after inserting the first refractive index layer 11 and the second refractive index layer 12 between the waveguide substrate 10 and the electrochromic layer 13, a three-layer optical cavity structure is formed. While the light is reflected at the interface of the waveguide substrate 10, part of the evanescent wave energy enters the cavity and interferes back and forth between the first refractive index layer 11 and the second refractive index layer 12. The reflection characteristics of the cavity depend on: Out-coupling loss rate (γ e ): the ability of light to couple into the cavity and be reflected back into the waveguide substrate 10, determined by the thickness and refractive index of the second refractive index layer 12; Internal loss rate (γ i ): the energy loss of light absorbed in the cavity, determined by the extinction coefficient k of the electrochromic layer 13.

[0045] When the electrochromic layer 13 is in different states, γ i changes significantly, thereby making the reflectivity R of the cavity present different patterns: ; When γ i γ e (transparent state): the cavity is in an under-coupling state, most of the light energy returns to the waveguide substrate 10 after being reflected back and forth in the cavity, the overall reflectivity is high (R≈1), and the waveguide light is almost unaffected; When γ i =γ e (critical coupling): the cavity is in a complete matching state, the reflected waves cancel each other out (coherent cancellation), and the light energy is completely absorbed, with the reflectivity being at a minimum (R≈0); When γ i >γ e (over-coupling): the absorption is too strong, part of the energy is still reflected back to the waveguide substrate 10, and the reflectivity rises slightly.

[0046] As can be seen, by accurately designing the thickness of the second refractive index layer 12 and the absorption range of the electrochromic layer 13, the system can naturally switch between the transparent state and the colored state to enhance reflection and cancel reflection, achieving an electrically controlled conversion from "high reflection" to "high absorption".

[0047] Monocular and binocular switching mechanism: In the binocular waveguide substrate 10, the left and right coupling-out areas 103 are respectively provided with independent electrically controlled driving modules. When the left and right electrochromic layers 13 are both in the transparent state, the light in the waveguide substrate 10 propagates symmetrically and is emitted from both sides at the same time, forming binocular display. When monocular display is needed, only one side of the electrochromic layer 13 is made to enter the colored state (γ i ≈γ e , reflection cancellation), the light of this side is absorbed by the cavity, and the waveguide light is no longer guided out, while the other side still maintains the normal emission in the transparent state, thereby realizing fast monocular and binocular display switching.

[0048] Luminance adjustment and uniformization mechanism: The extinction coefficient k of the electrochromic layer 13 has a continuous adjustable relationship with the driving voltage of the electrically controlled driving module. When in the intermediate state, γ i is between under-coupling and critical coupling. At this time, the reflectivity of the system is between high reflection and complete absorption, that is, the single reflection loss can be adjusted in the range of 0.1% to 80%. Since the waveguide light undergoes multiple reflections (10-20 times) in the light guide path, even if the single loss changes only by 1%-3%, it will have a significant impact on the total emission brightness. By accurately adjusting the driving voltage, the cumulative brightness of the left and right eye waveguide substrates 10 tends to be consistent, that is, the luminance balance and grayscale control can be realized.

[0049] Coherent cancellation and light energy absorption mechanism: In the colored state, the real and imaginary parts of the refractive index of the electrochromic layer 13 change simultaneously, so that the light waves (R1) reflected from the interface of the waveguide substrate 10 and the light waves (R2) reflected back from the electrochromic layer 13 in the cavity differ in phase by nearly π. After superposition, the two reflected waves undergo coherent cancellation, and the reflected energy is significantly reduced, and the remaining energy is absorbed or scattered by the cavity. This phenomenon is the "loss resonance absorption" or "critical coupling absorption" effect. In the transparent state, the phases of the two waves are consistent, forming a coherent enhanced reflection, and the reflectivity returns to nearly 1.

[0050] The functions of the waveguide structure of the present application can be realized in actual work according to the following steps: (1) At the initialization, the electrochromic layer 13 is controlled to be in the transparent state (low absorption), the system is kept in the high reflection state, the waveguide light is fully reflected and guided out, and binocular display is realized; (2) When monocular display is needed, the electrically controlled driving module applies voltage to one side of the electrochromic layer 13 to gradually color it and increase the absorption, and the light path of this side is closed by absorption; (3) If the left and right luminances are not uniform or luminance adjustment is needed, the electrically controlled driving module can apply an intermediate voltage to the electrochromic layer 13 to make k in the partially colored state, and realize luminance gradual compensation; (4) After the voltage is removed, the electrochromic layer 13 spontaneously returns to the transparent state, and the system restores the high-brightness binocular display.

[0051] The whole process only relies on optical phase and absorption regulation in the thin film structure layer, without mechanical components, with fast response speed and high stability, and can complete light path switching or brightness adjustment within milliseconds.

[0052] Therefore, the principle of the present application is to realize reversible switching of high reflection in transparent state and high absorption in colored state by the lossy resonant cavity formed by the adjustable absorption of the electrochromic layer 13 and the phase interference of the second refractive layer 12 and the first refractive layer 11, and to realize gray-scale brightness control by continuously regulating the extinction coefficient k. This principle enables the single-optical machine binocular diffraction waveguide substrate 10 to have multiple functions such as electrically controlled display, brightness equalization, and light path switching, without changing the structure.

[0053] The following is specifically described by different embodiments: Example one is used to verify the feasibility of the present application in realizing single and binocular switching display in the single-optical machine binocular diffraction waveguide substrate 10 system. The waveguide substrate 10 used is high refractive glass (n1=1.8), the incident angle is about 50°, and the working wavelength is 520 nm. The first refractive layer 11, the second refractive layer 12, and the electrochromic layer 13 are sequentially deposited on the outer surface of the waveguide substrate 10, wherein the first refractive layer 11 is made of SiO2 with a thickness of 320 nm; the second refractive layer 12 is made of TiO2 with a thickness of 80 nm; the electrochromic layer 13 is made of WO3 with a thickness of 200 nm, and the electrochromic layer 13 is outside the complete electrochemical unit composed of a Ta2O5 ion conductive layer and an ITO counter electrode.

[0054] In the initial state of the system, the left and right electrochromic layers 13 are both in the transparent state, the extinction coefficient k≈0, the cavity is in the under-coupling state, the waveguide light is almost totally reflected on the interface, the light guide efficiency is >99%, the binocular display mode of simultaneous emission from the left and right sides is realized, and the partial view is as shown in Figure 3 , and the global view is as shown in Figure 5 .

[0055] When the electrically controlled driving module applies a driving voltage of about 2.5V to the left electrochromic layer 13, the electrochromic layer 13 gradually colors, the extinction coefficient k increases to 0.06-0.08, the cavity enters the critical coupling state, the right side emission light energy is absorbed by the cavity by about 80%, the waveguide light is cut off at this side, and multiple positions are provided with electrochromic layers 13 to completely prevent light from being guided out, as shown in Figure 4 and Figure 6 . The left side still maintains the transparent state high reflection, and the light energy is normally emitted. The left side can also be colored, and the right side can be cut off, which can be adjusted by the user. Thus, the system completes the switching from binocular display to monocular display within milliseconds without any mechanical shielding or liquid crystal shutter structure.

[0056] The experimental results show that the single reflection loss can be adjusted from <0.1% to >70%, and the cumulative output brightness contrast is more than 20dB. The whole switching process has low voltage, fast response, good repeatability, and no obvious fatigue attenuation in long-term cycle, which verifies the effectiveness of the application in single-double eye fast electrically controlled switching display.

[0057] Embodiment two verifies the function of the application in realizing left and right eye brightness balance and gray scale adjustment in single light machine double eye waveguide substrate 10. The experimental sample structure is the same as that of embodiment one. The system is detected at the factory and found that the left eye brightness is about 10% higher than the right eye. By adjusting the driving voltage of the left electrochromic layer 13, it is in a partially colored state, as shown in Figure 7 and Figure 8 , the extinction coefficient k≈0.025 is controlled, and the single reflection loss is about 1%. Since the waveguide light experiences an average of 12 times of total reflection before being emitted, the cumulative output brightness is reduced by about 12%, which is consistent with the right eye brightness, as shown in Figure 9 , the left and right eye brightness has a relatively obvious brightness difference before adjustment, and after the above adjustment, the left and right eye brightness is close to consistent; thereby making the binocular display more uniform.

[0058] In this state, the image color has no obvious change, and the brightness difference is controlled within ±3%, which meets the comfort requirements of human eye fusion vision. Further tests show that by changing the driving voltage of the electrochromic layer 13, the single loss can be continuously adjusted in the range of 0.5% to 10%, and the output brightness can be changed in the range of 5% to 80%.

[0059] This function can be dynamically adjusted according to the actual display environment, the output difference of left and right eye light machines, or the subjective brightness preference of users, and automatic brightness correction can also be realized. This scheme does not need to adjust the light machine power or re-correct the grating parameters, and only realizes the brightness balance through electrical control, which ensures the stability of the overall optical structure of the waveguide substrate 10.

[0060] Embodiment three is mainly about the setting position of the thin film structure layer: As shown in Figure 10 , in an example, the thin film structure layer can be set on both sides of the waveguide substrate 10, that is, the thin film structure layer can be set on the side of the waveguide substrate 10 where the grating is arranged, or on the side of the waveguide substrate 10 away from the grating, and the side of the waveguide substrate 10 where the grating is arranged forms the coupling-in region 101 and the coupling-out region 103. The advantage of such arrangement is that the absorption effect of light is better when the electrochromic layer 13 is in the colored state. If the thin film structure layer is single-layered, the first reflection will be absorbed only once, and if it is double-layered, the first reflection will be absorbed twice, which can achieve better light absorption effect.

[0061] As shown in Figure 11 , Figure 12As shown, in an example, the waveguide substrate 10 is further provided with a turning area 102. The thin film structure layer can be located between the entrance pupil area and the turning area 102, or can be located on the back of the waveguide substrate 10, and the projection of the thin film structure layer covers the turning area 102 entirely or partially. The advantage of this arrangement is that better light blocking effect can be achieved, and the light is blocked in front of the exit pupil area. Therefore, the thin film structure layer does not need to be additionally arranged between the turning area 102 and the exit pupil area, and the appearance of the product is also improved.

[0062] As shown in FIG. 1, the thin film structure layer can be arranged on the waveguide substrate 10 in three ways. Figure 13 As shown, in some cases, the waveguide substrate 10 does not necessarily have a turning area 102, but only includes an entrance pupil area and an exit pupil area. In this case, the thin film structure layer only needs to be arranged between the entrance pupil area and the exit pupil area.

[0063] The above three arrangement modes of the thin film structure layer can be implemented alone or in combination.

[0064] Therefore, the waveguide structure provided by the embodiments of the present application can be used to deposit a first refractive layer 11, a second refractive layer 12 and an electrochromic layer 13 on the outer surface of the existing diffractive waveguide substrate 10, and form a micro-patterned electrode. This structure does not affect the thickness and grating layout of the original waveguide substrate 10, and is compatible with the existing AR optical module package.

[0065] In system integration, the thin film structure layer can be packaged between the waveguide substrate 10 and the protective cover plate, or directly used as part of the surface coating of the waveguide substrate 10 to realize modularization. By applying different driving voltages to the electrochromic layer 13 through an electrically controlled driving module, the following functions can be realized: independent switching of left and right eye channels (single or double eye switching); gray scale brightness control of light channels (brightness balance); local area brightness distribution adjustment (field uniformization or local light blocking).

[0066] The design of the present application takes into account the optical performance, response speed and process compatibility, and can be widely used in AR waveguide substrate 10 display, optical HUD, adjustable transmittance privacy display and other products. The reflectivity and absorptivity of the guided light wave under different electrochromic states are adjusted, so that the single or double eye display switching and brightness adjustable functions are realized.

[0067] The waveguide structure of the present application is mainly applied to an augmented reality (AR) display system based on a diffractive waveguide substrate 10, and is particularly suitable for a binocular display module formed by using a single optical machine input and a symmetric diffractive exit structure.

[0068] Based on this, the embodiment of the application further provides a binocular display module, which comprises an optical machine projection module, an electric control driving module and the above-mentioned waveguide structure, and at least two coupling-out areas 103 are symmetrically arranged on the waveguide substrate 10 of the waveguide structure, each coupling-out area 103 corresponds to a thin film structure layer and an electric control driving module, and the electric control driving module is connected with the electrochromic layer 13 of the corresponding thin film structure layer.

[0069] The overall architecture of the system comprises an optical machine projection module, an electric control driving module and the above-mentioned waveguide structure, the waveguide structure comprises a waveguide substrate 10, and a first refractive index layer 11, a second refractive index layer 12 and an electrochromic layer 13 arranged outside the waveguide substrate 10 to form an adjustable absorption structure, and at least a coupling-in area 101 and a coupling-out area 103 are arranged on the waveguide substrate 10, the coupling-in area 101 is provided with a diffraction coupling-in grating, and the coupling-out area 103 is provided with a diffraction coupling-out grating.

[0070] And at least two coupling-out areas 103 are symmetrically arranged on the waveguide substrate 10 to correspond to the left and right eyes respectively. Each coupling-out area 103 corresponds to a thin film structure layer and an electric control driving module, and the electric control driving module is connected with the electrochromic layer 13 of the corresponding thin film structure layer to control the electrochromic layer 13 of the left and right eyes respectively. When both sides of the electrochromic layer 13 are in a transparent state, the light in the waveguide substrate 10 propagates symmetrically and is emitted from both sides of the coupling-out area 103 at the same time, forming binocular display. When monocular display is needed, only one side of the electrochromic layer 13 is allowed to enter the colored state (γ i ≈γ e , reflection cancellation), the light energy of this side is absorbed by the cavity, and the waveguide light is no longer guided out, while the other side still maintains the transparent state and normally emits, thereby realizing fast switching between monocular and binocular display.

[0071] In the above application scenarios, the image light emitted by the optical machine projection module is guided into the waveguide substrate 10 through the diffraction coupling-in grating (coupling-in area 101) and propagates in the waveguide substrate 10 by multiple total reflections at a specific angle. Since the diffraction coupling-out grating (coupling-out area 103) is symmetrically designed, the light propagates in the left and right directions respectively and is emitted from both sides of the waveguide substrate 10 to form the left and right eye fields, thereby realizing single optical machine binocular display. By arranging the first refractive index layer 11, the second refractive index layer 12 and the electrochromic layer 13 on one side of the waveguide substrate 10 to form an electrochromic loss resonant cavity structure, the emission intensity of the waveguide light can be dynamically regulated.

[0072] In the monocular display mode, only one side of the electrochromic layer 13 is allowed to be in a transparent state (low absorption), and the other side of the electrochromic layer 13 is allowed to be in an absorption state (high loss), thereby only outputting single-sided image light, which is suitable for privacy display, monocular calibration, contrast test and other scenarios.

[0073] In binocular display mode, both sides of the electrochromic layer 13 remain transparent state, and the light guide substrate 10 keeps high reflection and low loss in the light guide process, realizing normal output of binocular image and ensuring high brightness and high transmittance display.

[0074] In brightness balance and gray scale adjustment mode, by adjusting the driving voltage of the electrochromic layer 13 of a side or a local area, the extinction coefficient k of the area can be in the middle value (partially colored state), so as to change the single reflection loss ratio without closing the light path, and achieve fine brightness control effect. This function is particularly suitable for compensating the binocular brightness unevenness caused by the output power difference of the light machine, the diffraction efficiency deviation or the imbalance of human eye brightness perception.

[0075] In addition, the present application can also be extended to a multi-region partition control scene. The waveguide substrate 10 surface is divided into multiple electrically controlled blocks according to the field of view or the coupling-in area 101, and each block corresponds to an independent electrode and a driving channel, which can be set to transparent, semi-absorbing or high-absorbing state. Through partition control, local brightness distribution adjustment, privacy display, environment adaptive display, field of view brightness gradient compensation or partial view area shutdown can be realized, which is suitable for high-end AR headsets, vehicle-mounted AR-HUD or optical privacy protection scenes.

[0076] In summary, the system architecture of the present application can realize dynamic management of the light path through the integrated electro-optical control layer without changing the existing light machine and waveguide main structure, which significantly improves the display flexibility, uniformity and functional expansion of the single light machine binocular waveguide substrate 10 system.

[0077] On the other hand, the embodiment of the present application also provides a method for switching binocular and monocular display, which adopts the above-mentioned binocular display module, and the method comprises: The electrochromic layer 13 of the corresponding thin film structure layer of the coupling-out area 103 is controlled by the electrically controlled driving module, so as to adjust the extinction coefficient k of the electrochromic layer 13 to a preset value, so that the brightness of the coupling-out area 103 is reduced to a preset brightness interval.

[0078] When the left eye brightness is uneven or monocular display is desired, the extinction coefficient k of the electrochromic layer 13 corresponding to a certain side of the coupling-out area 103 is adjusted to a suitable value, so that the brightness of the coupling-out area 103 on that side is reduced to a suitable interval.

[0079] The electrically controlled driving module is connected with the electrochromic layer 13 of the corresponding thin film structure layer, so as to control the electrochromic layer 13 of the left and right eyes respectively. When both sides of the electrochromic layer 13 are in transparent state, the light in the waveguide substrate 10 propagates symmetrically and exits from both sides of the coupling-out area 103 at the same time, forming binocular display. When monocular display is needed, only one side of the electrochromic layer 13 enters colored state (γ i ≈γ e, reflection cancellation), the light of the side can be absorbed by the cavity, and the waveguide light is no longer guided out, and the other side still maintains the transparent state and normally exits, thereby realizing fast single-double display switching.

[0080] The binocular display module and the method of switching binocular display contain the same structure and beneficial effects as the waveguide structure in the foregoing embodiments. The structure and beneficial effects of the waveguide structure have been described in detail in the foregoing embodiments, and will not be described here again.

[0081] The above only describes the embodiments of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A waveguide structure, characterized in that, include: A waveguide substrate, wherein a thin film structure layer is disposed on at least one side of the waveguide substrate, the thin film structure layer including a first refractive index layer disposed on the waveguide substrate, a second refractive index layer disposed on the first refractive index layer, and an electrochromic layer disposed on the second refractive index layer, the electrochromic layer being used to connect an electronically controlled drive module, the electronically controlled drive module providing a drive voltage to the electrochromic layer.

2. The waveguide structure according to claim 1, characterized in that, The complex refractive index n of the electrochromic layer ec =n+i·k, where n is the refractive index of the electrochromic layer in the transparent state, k is the extinction coefficient, and k changes continuously with the applied driving voltage.

3. The waveguide structure according to claim 1, characterized in that, The refractive index n of the first refractive index layer g The thickness ranges from 1.0 to 1.3 nm and from 200 nm to 600 nm.

4. The waveguide structure according to claim 1, characterized in that, The refractive index n of the second refractive index layer H The diameter is 1.8 to 2.4, and the thickness is 40 nm to 150 nm.

5. The waveguide structure according to any one of claims 1 to 4, characterized in that, The waveguide substrate has a coupling-in region and a coupling-out region, and the thin film structure layer is disposed between the coupling-in region and the coupling-out region.

6. The waveguide structure according to claim 5, characterized in that, The waveguide substrate is further provided with a transition region, and the thin film structure layer is disposed between the coupling region and the transition region, and / or the thin film structure layer is disposed on the other side of the waveguide substrate opposite to the transition region, and the projection of the thin film structure layer covers or partially covers the transition region.

7. The waveguide structure according to any one of claims 1 to 4, characterized in that, The thin film structure layer is disposed on the side of the waveguide substrate opposite to the grating.

8. The waveguide structure according to any one of claims 1 to 4, characterized in that, The material of the first refractive index layer includes any one of SiO2, porous silica, magnesium fluoride, an air layer, or an organic polymer layer with low refractive index properties; the material of the second refractive index layer includes TiO2, HfO2, Ta2O5, ZnS, or any combination of stacked materials thereof; the material of the electrochromic layer includes WO3, NiO, MoO3, V2O5, or a composite multilayer structure thereof.

9. A binocular display module, characterized in that, The device includes an optomechanical projection module, an electronically controlled drive module, and a waveguide structure as described in any one of claims 1 to 8. At least two coupling regions are symmetrically arranged on the waveguide substrate of the waveguide structure. Each coupling region corresponds to a thin film structure layer and an electronically controlled drive module. The electronically controlled drive module is connected to the electrochromic layer corresponding to the thin film structure layer.

10. A method for switching between monocular and binocular displays, employing the binocular display module as described in claim 9, characterized in that, The method includes: The electrochromic layer of the thin film structure corresponding to the coupling region is controlled by the electronically controlled drive module to adjust the extinction coefficient k of the electrochromic layer to a preset value, so that the brightness of the coupling region is reduced to a preset brightness range.

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