Diffraction optical waveguide and augmented reality display device

Abstract

The embodiment of the present application discloses a diffraction optical waveguide and an augmented reality display device, wherein the diffraction optical waveguide comprises: a waveguide substrate and an in-coupling grating, a turning grating, and an out-coupling grating arranged on the waveguide substrate; the in-coupling grating is used to couple light into the waveguide substrate and propagate toward the turning grating; the turning grating is used to deflect light to propagate toward the out-coupling grating; the out-coupling grating is used to couple light from the waveguide substrate into the human eye; wherein the turning grating has multiple diffraction turning regions, and the boundary lines of at least two of the diffraction turning regions match the transmission direction of the light after being deflected by the turning grating. The diffraction optical waveguide provided in the embodiment of the present application can, to a certain extent, avoid the problem of dark or bright areas in the shape of stripes appearing in the displayed image after the turning grating is partitioned, thereby weakening or even eliminating the display problem of dark or bright areas, and optimizing the brightness uniformity of the display.

Description

Technical Field

[0001] The present application relates to the field of augmented reality, and in particular to a diffraction optical waveguide and an augmented reality display device. Background Art

[0002] Augmented Reality (AR) is a technology that merges the real world with virtual information, and optical waveguide systems are a key component in enabling AR. In AR display scenarios, an optical machine projects a beam of imagery to be superimposed on the real scene onto the waveguide system. The waveguide system then deflects the beam, directing it toward the eye. Existing one-dimensional waveguide systems typically use one-dimensional gratings for pupil expansion and outcoupling.

[0003] To improve display brightness and brightness uniformity, the turning grating and outcoupling grating are typically divided into multiple regions with different grating parameters. However, this partitioning of the turning grating can result in streaky dark or bright areas in the displayed image, severely affecting the brightness uniformity of the displayed image. Summary of the Invention

[0004] The present application aims to alleviate the phenomenon in the prior art that after the turning grating is partitioned, dark areas or bright areas in the shape of stripes may appear in the displayed image, which seriously affects the brightness uniformity of the displayed image.

[0005] Based on this, a diffraction optical waveguide is provided, comprising:

[0006] A waveguide substrate and an input grating, a turning grating and an output grating arranged on the waveguide substrate; the input grating is used to couple light into the waveguide substrate and propagate toward the turning grating; the turning grating is used to deflect light to propagate toward the output grating; the output grating is used to couple light from the waveguide substrate into the human eye; wherein the turning grating has a plurality of diffraction turning regions, and the boundary line of at least two of the diffraction turning regions matches the transmission direction of the light after being deflected by the turning grating, and the boundary line matches the transmission direction, that is, the boundary line is basically parallel to the transmission direction of the central field of view light after being deflected by the turning grating; specifically defined as the angle between the boundary line and the positive direction of the X-axis in the spatial rectangular coordinate system The range is [ ];in, is the angle between the transmission direction of the light after being deflected by the turning grating and the positive direction of the X-axis, which satisfies the following relationship:

[0007] in, for In arc form, is the central wavelength of the light, is the angle between the optical axis of the optical machine and the YZ plane, for In arc form, is the angle between the optical axis of the optical machine and the XZ plane, for In arc form, is the angle between the grating vector coupled into the grating and the positive direction of the X axis, for In arc form, is the angle between the grating vector of the turning grating and the positive direction of the X axis, for In arc form, for In arc form, is the grating period of the coupled grating, is the grating period of the transition grating, is the tolerance value.

[0008] Optionally, a boundary line between any two of the diffraction turning regions is substantially parallel to a transmission direction of the central field light after being deflected by the turning grating.

[0009] Optionally, any one of the coupling-in grating, the turning grating and / or the coupling-out grating is a one-dimensional grating or a two-dimensional grating, or a combination thereof.

[0010] Optionally, the diffraction efficiencies of at least two of the diffraction turning regions for the same diffraction order gradually increase in a direction away from the coupling-in grating.

[0011] Optionally, the grating depth, duty cycle or tilt angle in at least two of the diffraction turning regions gradually changes in a direction away from the coupling-in grating.

[0012] Optionally, the outcoupling grating has a plurality of diffraction outcoupling regions, and the diffraction efficiencies of at least two of the diffraction outcoupling regions for the same diffraction order gradually increase along the transmission direction.

[0013] Optionally, the grating depth, duty cycle or tilt angle in at least two of the diffraction turning regions gradually changes away from the transmission direction.

[0014] Optionally, a high refractive index film layer is provided on a surface of at least one of the coupling-in grating, the turning grating and the coupling-out grating.

[0015] The present application also provides an augmented reality display device, which includes an optical machine and a diffraction optical waveguide as described in any one of the above items.

[0016] The diffraction light waveguide and augmented reality display device provided by the present application specially set the position of the dividing line between two adjacent diffraction turning areas so that the propagation direction of the light after deflection by the turning grating matches. This can, to a certain extent, avoid the problem of striped dark or bright areas appearing in the displayed image caused by the difference in the diffraction efficiency change trend between the effective part and the loss part during the propagation of light, thereby weakening or even eliminating the display problem of dark or bright areas and optimizing the brightness uniformity of the display. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts.

[0018] Figure 1 Schematic diagram of the structure of a diffraction optical waveguide in the prior art;

[0019] Figure 2 This is a schematic diagram of the design of a diffraction optical waveguide in one embodiment of the present application;

[0020] Figure 3 Schematic diagram comparing the dark fringes displayed on the optical waveguide before and after improvement in one embodiment of the present application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0022] In the description of the present application specification, it should be understood that the terms "upper", "lower", "upper end", "lower end", "lower surface", "upper surface", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present application.

[0023] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of such features.

[0024] In the description of the present application, “plurality” means multiple, such as two, three, four, etc., unless otherwise clearly defined.

[0025] In the description of this application, unless otherwise specified or limited, the term "connection" and other terms should be understood in a broad sense. For example, it can mean fixed connection, detachable connection, or integration; it can mean mechanical connection, electrical connection, or mutual communication; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0026] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0027] Existing one-dimensional optical waveguide systems usually use one-dimensional gratings for coupling in, pupil expansion, and coupling out, such as Figure 1 As shown, the diffraction optical waveguide includes a coupling-in grating 101, a turning grating 102, and a coupling-out grating 103. After the light passes through the coupling-in grating 101 and diffracts into the waveguide substrate, it is transmitted by total internal reflection in the direction of the turning grating 102. When the light is incident on the turning grating 102, due to the diffraction effect of the turning grating 102, it will split into new light rays and turn to the direction of the coupling-out grating 103 for total internal reflection. The light rays are diffracted and coupled out by the coupling-out grating 103 and enter the human eye, allowing the human eye to see the display image. However, when the diffraction efficiency remains unchanged, the light is continuously diffracted during the transmission process, resulting in continuous energy attenuation, which in turn leads to poor display uniformity. In the prior art, in order to improve the brightness and uniformity of the diffraction optical waveguide display, the turning grating and / or the coupling-out grating are often divided into several regions with different grating parameters. By setting the grating parameters, the diffraction efficiency of different regions gradually changes along the light transmission direction. This can improve display uniformity.

[0028] However, the inventors of the present application discovered that after the turning grating 102 is partitioned, in some cases, there will be a phenomenon of stripe-shaped dark areas or bright areas on the displayed image. However, the cause of this technical defect is not obvious. According to conventional thinking in the field, the inventors of the present application generally believe that it is the problem of setting the grating parameters in each zone after partitioning that causes the phenomenon of stripe-shaped dark areas or bright areas on the displayed image, and then optimize the grating parameters in the partition, but find that the mitigation of this phenomenon does not have a good effect. Finally, after creative work, it is found that the cause of this technical defect is related to the setting position of the turning grating partition boundary line. The exemplary explanation is as follows, and continue to refer to Figure 1 , the turning grating 102 is exemplarily divided into four diffraction turning regions along the propagation direction of the light: 1021, 1022, 1023 and 1024. After the light 104 diffracted by the coupling grating 101 enters the turning grating 102, it will split into new light rays 1041, 1043 and 1045 due to the first-order diffraction of the turning grating 102. After each total internal reflection transmission cycle P, the light rays 1041, 1043 and 1045 will be split into new light rays such as light rays 1042 and 1044 through the -1 diffraction order of the turning grating. Here, the energy of the light 104 is defined as Po1, the first-order diffraction efficiency of region 1021 is Z1, the -1-order diffraction efficiency is Z12, the first-order diffraction efficiency of region 1022 is Z2, and the -1-order diffraction efficiency is Z22, then Figure 1 The energy of 1041, 1043 and 1045 leaving the turning grating 、 、 They are approximately:

[0029]

[0030] Generally, in order to improve the brightness and brightness uniformity of the diffraction waveguide display, the diffraction efficiency is higher in the diffraction turning area farther away from the coupling grating, so there will be a situation of Z2>Z22>Z1>Z12, and then > > , that is, the energy of light 1045 is higher than that of light 1041, which is higher than that of light 1043. Since light 1043 is located between light 1041 and light 1045, a stripe-shaped dark area will appear, affecting the brightness uniformity. Moreover, due to the different transmission angles and transmission periods of light of different wavelengths, the dark areas of each wavelength will be separated, which will also affect the color uniformity. It is worth noting that Figure 1 The rays shown in the figure are only examples. The actual interactions between rays and gratings are more numerous and complex. The energy will be significantly weaker than and .

[0031] In view of this, an embodiment of the present application provides a diffraction optical waveguide, which includes: a waveguide substrate and an in-coupling grating, a turning grating, and an out-coupling grating arranged on the waveguide substrate; the in-coupling grating is used to couple light into the waveguide substrate and propagate toward the turning grating; the turning grating is used to deflect light to propagate toward the out-coupling grating; and the out-coupling grating is used to couple light from the waveguide substrate into the human eye; wherein the turning grating has multiple diffraction turning regions, and the boundary line of at least two diffraction turning regions matches the transmission direction of the light after being deflected by the turning grating. In practice, the diffraction efficiency of at least two diffraction turning regions for the same diffraction order gradually increases in a direction away from the in-coupling grating. Specifically, the grating depth, duty cycle, or tilt angle in at least two diffraction turning regions gradually changes in a direction away from the in-coupling grating.

[0032] It can be understood that it is precisely because the boundary line of the diffraction turning region does not match the transmission direction of the light after being deflected by the turning grating that the following occurs: Class 1 light: turns in the diffraction turning region with low diffraction efficiency and is lost in the diffraction turning region with low diffraction efficiency; Class 2 light: turns in the diffraction turning region with low diffraction efficiency and is lost in the diffraction turning region with high diffraction efficiency; Class 3 light: turns in the diffraction turning region with high diffraction efficiency and is lost in the diffraction turning region with high diffraction efficiency. Moreover, Class 2 light is located between Class 1 and Class 3 light, and its energy is significantly weaker than that of Class 1 and Class 3 light, resulting in the appearance of striped dark areas. Among them, the light that turns in the diffraction turning region and transmits toward the coupling grating is effectively utilized light, while the light that transmits along the original direction in the diffraction turning region is lost light.

[0033] In this application, by specifically positioning the boundary line between two adjacent diffraction turning regions, such that at least one of the turning grating's dividing lines matches the propagation direction of light after being deflected by the turning grating, this can, to a certain extent, avoid the problem of streaky dark or bright areas in the displayed image caused by the difference in diffraction efficiency between effectively utilized light and lost light as the light propagates. This can then mitigate or even eliminate the display problem of dark or bright areas, optimizing display brightness uniformity. Furthermore, improved brightness uniformity can also improve color uniformity.

[0034] In practice, the boundary line of the diffraction turning area matches the transmission direction of the light from the diffraction grating turning to the outcoupling grating, so that the boundary line of the diffraction turning area is basically parallel to the transmission direction of the central field light from the diffraction grating turning to the outcoupling grating.

[0035] Furthermore, in the present application, the dividing line of any two diffraction turning areas can be set to be basically parallel to the transmission direction of the central field of view light after being deflected by the turning grating, that is, the dividing line of all turning gratings is basically parallel to the propagation direction of the central field of view light after being deflected by the turning grating.

[0036] It should be noted that the division boundary line of the turning grating in this application is substantially parallel to the propagation direction of the light after the turning grating is deflected. This means that the division boundary line of the turning grating and the propagation direction of the light after the turning grating are not required to be absolutely parallel in a geometric sense, and there may be a deviation within a certain angle range. Specifically, each "direction" in this application is described by its angle with the positive direction of the X-axis in the spatial rectangular coordinate system, with reference to Figure 3 , the angle between the transmission direction of the light after deflection by the turning grating and the positive direction of the X axis It can be calculated by the following formula:

[0037] in, is the central wavelength of light 404, is the angle between the optical axis of the optical machine and the YZ plane, for In arc form, is the angle between the optical axis of the optical machine and the XZ plane, for In arc form, is the angle between the grating vector coupled into the grating 401 and the positive direction of the X axis, for In arc form, is the angle between the grating vector of the turning grating 402 and the positive direction of the X axis, for In arc form, for In arc form, is the grating period of the coupling-in grating 401, is the grating period of the turning grating 402, and the diffraction waveguide includes the coupling-in grating 401, the turning grating 402, and the coupling-out grating 403. Then, the boundary line of the diffraction turning area is substantially parallel to the transmission direction of the central field of view light after being deflected by the turning grating, which can be realized as follows: the angle between the boundary line of the diffraction turning area and the positive direction of the X axis is for[ ],in, is the tolerance value for substantially parallelism. The value range is [0,1].

[0038] Optionally, any one of the coupling-in grating, the turning grating and / or the coupling-out grating is a one-dimensional grating or a two-dimensional grating or a combination thereof. Figure 3, Figure 3 (a) is a diagram of the grating structure when the partition boundary of the turning grating does not match the propagation direction of the light after being deflected by the turning grating. Figure 3 (b) is a diagram of the grating structure when the partition boundary of the turning grating matches the propagation direction of the light after being deflected by the turning grating. Figure 3 (c) Figure 3 (a) Display image under the architecture shown, Figure 3 (d) Figure 3 (b) The display image under the architecture shown. It can be clearly seen that Figure 3 In (c), there is a dark area marked by an ellipse. Figure 3 (d) relative to Figure 3 The brightness uniformity of (c) has been greatly improved.

[0039] In some embodiments, the outcoupling grating has multiple diffraction outcoupling regions, with at least two of the diffraction outcoupling regions having diffraction efficiencies for the same diffraction order gradually increasing along the transmission direction. In some implementations, the grating depth, duty cycle, or tilt angle within at least two of the diffraction turning regions gradually changes away from the transmission direction. This can further improve the display uniformity of the diffraction waveguide.

[0040] In some embodiments, a high refractive index film layer is provided on the surface of at least one of the coupling-in grating, the turning grating, and the coupling-out grating, thereby improving the light energy utilization rate of the diffraction light waveguide and enhancing the display brightness.

[0041] The diffraction optical waveguide provided in the present application can be a monochromatic optical waveguide or a color optical waveguide, and can be a single full-color waveguide or multiple full-color waveguides.

[0042] The present application also provides an augmented reality display device, comprising an optical engine and a diffractive optical waveguide as described above. The augmented reality display device includes, but is not limited to, augmented reality glasses, an in-vehicle head-up reality device, and the like.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diffractive optical waveguide comprising: A waveguide substrate and an input grating, a turning grating and an output grating arranged on the waveguide substrate; the input grating is used to couple light into the waveguide substrate and propagate toward the turning grating; the turning grating is used to deflect the light to propagate toward the output grating; the output grating is used to couple light from the waveguide substrate into the human eye; wherein the turning grating has a plurality of diffraction turning regions, and the boundary line between any two of the diffraction turning regions matches the transmission direction of the light after being deflected by the turning grating, so as to reduce the difference in the diffraction efficiency change trend between the effectively utilized light and the lost light as they propagate; the dividing line matches the transmission direction, that is, the dividing line is substantially parallel to the transmission direction of the central field of view light after being deflected by the turning grating, and is specifically defined as the range of the angle θ3 between the dividing line and the positive direction of the X-axis in the spatial rectangular coordinate system is [θ out -Δ,θ out +Δ]; where θ out is the angle between the transmission direction of the light after being deflected by the turning grating and the positive direction of the X-axis, which satisfies the following relationship: Among them, θ' out is θ out In radian form, λ is the central wavelength of the light, θ inx is the angle between the optical axis of the optical machine and the YZ plane, θ' inx is θ inx In radian form, θ iny is the angle between the optical axis of the optical machine and the XZ plane, θ' iny is θ iny is in radian form, θ1 is the angle between the grating vector of the coupled grating and the positive direction of the X-axis, θ'1 is the radian form of θ1, θ2 is the angle between the grating vector of the turning grating and the positive direction of the X-axis, θ'2 is the radian form of θ2, θ'3 is the radian form of θ3, p1 is the grating period of the coupled grating, p2 is the grating period of the turning grating, and Δ is the tolerance value.

2. The diffractive optical waveguide according to claim 1, wherein Any one of the coupling-in grating, the turning grating and / or the coupling-out grating is a one-dimensional grating or a two-dimensional grating, or a combination thereof.

3. The diffractive optical waveguide according to claim 1, wherein The diffraction efficiencies of at least two of the diffraction turning regions for the same diffraction order gradually increase in a direction away from the coupling-in grating.

4. The diffractive optical waveguide according to claim 3, characterized in that The grating depth, duty cycle or tilt angle in at least two of the diffraction turning regions gradually changes in a direction away from the coupling-in grating.

5. The diffractive optical waveguide according to claim 1, wherein The outcoupling grating has a plurality of diffraction outcoupling regions, and the diffraction efficiencies of at least two of the diffraction outcoupling regions for the same diffraction order gradually increase along the transmission direction.

6. The diffractive optical waveguide according to claim 5, characterized in that The grating depth, duty cycle or tilt angle in at least two of the diffraction turning regions gradually changes away from the transmission direction.

7. The diffractive optical waveguide according to claim 1, wherein A high refractive index film layer is provided on the surface of at least one of the coupling-in grating, the turning grating and the coupling-out grating.

8. An augmented reality display device, characterized in that: The augmented reality display device includes an optical engine and a diffraction optical waveguide according to any one of claims 1 to 7.

Images