Optical waveguide systems and electronic devices

Abstract

The present application discloses an optical waveguide system and an electronic device. The optical waveguide system includes a waveguide, an input coupler for coupling light into the waveguide, and an output coupler. The input coupler includes a right portion and a left portion, wherein the right portion includes a first polarizer grating and a second polarizer grating stacked together, and the left portion includes a third polarizer grating and a fourth polarizer grating stacked together. The first polarizer grating and the fourth polarizer grating are polarizer gratings optimized for the right-side viewing angle of light, while the third polarizer grating and the second polarizer grating are polarizer gratings optimized for the left-side viewing angle of light.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical waveguide systems, and in particular to an optical waveguide system and an electronic device. Background Art

[0002] In optical display systems such as near-eye displays (NEDs), light emitted from a display with a certain field of view (FOV) is in-coupled into a waveguide (WG) through an input coupler grating (ICG), undergoes total internal reflection (TIR) ​​and pupil expansion, and is finally out-coupled by an output coupler grating (OCG).

[0003] Rendered image reconstruction relies on TIR conditions and grating equations that must be satisfied at all angles within the field of view. Traditional waveguide systems based on surface-relief gratings (SRGs) have limited angular response due to the first-order grating equations for specific wavelengths. The limited angular response of the grating can allow most of the field of view to be transmitted for different wavelengths of light. But more often, some fields may be outside the first-order conditions or TIR conditions, resulting in the loss of these fields. Compared with blazed gratings and binary gratings, the tilted gratings of surface relief gratings can have a wider angular response, but the tilted gratings are still limited to a limited field of view. For augmented reality (AR) technology, a wider field of view system with a small size and a large eyebox is ideal for better image rendering, thereby improving the user experience.

[0004] The article “Improved saturation and wide-viewing angle color filters based on multi-twist retarders” published by Li L, Shi S, and Escuti MJ in Opt Express (see 2021; 29(3): 4124-4138) discloses saturation and wide-viewing angle color filters based on multi-twist retarders, which is incorporated herein by reference in its entirety.

[0005] The article “Super achromatic wide-angle quarter-wave plates using multi-twist retarders” published by Li L, Escuti MJ in Opt Express (see 2021; 29(5): 7464-7478) discloses super achromatic wide-angle quarter-wave plates using multi-twist retarders, which is incorporated herein by reference in its entirety.

[0006] The article “Numerical analysis of Bragg polarization gratings” published by Xiang X, Escuti MJ in JOSA B. (see 2019; 36(5): D1--D8) discloses Bragg polarization gratings, which is incorporated herein by reference in its entirety.

[0007] The article “Nanoscale liquid crystal polymer Bragg polarization gratings” published by Xiang X, Kim J, Komanduri R, and Escuti MJ in Opt Express (see 2017; 25(16): 19298. doi: 10.1364 / OE.25.019298) discloses nanoscale liquid crystal polymer Bragg polarization gratings, which is incorporated herein by reference in its entirety.

[0008] The article “Bragg polarization gratings for wide angular bandwidth and high efficiency at steep deflection angles” published by Xiang X, Kim J, and Escuti MJ in Sci Rep. (see 2018; 8(1): 7202. doi: 10.1038 / s41598-018-25535-0) discloses Bragg polarization gratings, which is incorporated herein by reference in its entirety.

[0009] Lee YH, Yin K, Wu ST published an article in Opt Express titled “Reflective polarization volume gratings for high efficiency waveguide-coupling augmented reality displays” (see 2017; 25(22): 27008. doi: 10.1364 / OE.25.027008), which is incorporated herein by reference in its entirety.

[0010] The article “Volume Bragg gratings for near-eye waveguide display” published online by Chi W, Lee HY, and Saarikko P in 2021 discloses volume Bragg gratings, which is incorporated herein by reference in its entirety.

[0011] The article “Dispersion compensation in volume bragg grating-based waveguide display” published online by Chi W, Meiser D, Yang Y, Lam WST, and Saarikko P in 2021 discloses a waveguide display based on volume Bragg grating, which is incorporated herein by reference in its entirety.

[0012] The article “Optical waveguide beam splitter with polarization volume gratings for display” by Geng Y, Gollier, Jacques published in Amirsolaimani B. (see 2021; 2) discloses polarization volume gratings, which is incorporated herein by reference in its entirety.

[0013] The article “Polarization-sensitive components in optical systems for large pupil acceptance angles” published online by Amali A, Lu L, Maimone A, Moheghi A, Lam WST, McEldowney, S. Charles Lanman DR in 2020 discloses polarization-sensitive elements in optical systems for large pupil acceptance angles, which is incorporated herein by reference in its entirety.

[0014] Holographic waveguides are disclosed in the article “Holographic waveguides incorporating birefringence control and methods for their fabrication” by David WJ, Popvich M, Grant AJ., published online in 2021, which is incorporated herein by reference in its entirety.

[0015] The article “Polarization volume gratings for near-eye displays and novel photonic devices” published by Yin K, Zhan T, Xiong J, He Z, and Wu ST in Crystals. (see 2020; 10(7): 561) discloses polarizer gratings for near-eye displays, which is incorporated herein by reference in its entirety.

[0016] The article by Li L, Shi S, Escuti MJ. “Solc-style birefringent color filters based on multi-twist retarders” (see Hahlweg CF, Mulley JR, ed., Novel Optical Systems, Methods and Applications XXIII. Vol 11483. SPIE; 2020: 136-149. doi: 10.1117 / 12.2569133) discloses Solc-style birefringent color filters based on multi-twist retarders, which is incorporated herein by reference in its entirety. Summary of the Invention

[0017] One object of the present disclosure is to provide a new technical solution for optical waveguide systems.

[0018] According to a first aspect of the present disclosure, an optical waveguide system is provided, comprising: a waveguide; an input coupler, disposed on the input side of the waveguide and coupling light into the waveguide; and an output coupler, disposed on the output side of the waveguide and coupling light out of the waveguide, wherein the input coupler comprises a right portion and a left portion. As viewed from the incident direction of light, the right portion is located on the right side of the input coupler, and the left portion is located on the left side of the input coupler. The right portion comprises a first polarizer grating and a second polarizer grating stacked below the first polarizer grating, and the left portion comprises a third polarizer grating and a fourth polarizer grating stacked below the third polarizer grating. The first polarizer grating and the fourth polarizer grating are polarizer gratings optimized for a right-side viewing angle of light, and the third polarizer grating and the second polarizer grating are polarizer gratings optimized for a left-side viewing angle of light.

[0019] According to a first aspect of the present disclosure, there is provided an electronic device including: a display that generates image light; and the light waveguide system according to the embodiment that receives the image light.

[0020] According to the embodiments of the present disclosure, the performance of an optical waveguide system can be improved.

[0021] Further features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the invention.

[0023] Figure 1 A schematic diagram showing an optical waveguide system according to one embodiment.

[0024] Figure 2 express Figure 1 Schematic diagram of the input coupler structure.

[0025] Figure 3 A schematic diagram showing an optical waveguide system according to another embodiment.

[0026] Figure 4 express Figure 3 Schematic diagram of the input coupler structure.

[0027] Figure 5 FIG. 1 is a schematic structural diagram of an input coupler according to another embodiment.

[0028] Figure 6 A schematic block diagram illustrating an electronic device according to an embodiment.

[0029] Figure 7 An example of an electronic device is shown. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of components and steps described in these embodiments do not limit the scope of the present disclosure.

[0031] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention, its application, or uses.

[0032] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail but will become part of the description where appropriate.

[0033] In all examples illustrated and discussed herein, any specific numerical values ​​should be interpreted as merely illustrative and non-limiting. Therefore, other examples of the exemplary embodiments may have different numerical values.

[0034] Please note that in the following figures, like reference numbers and letters refer to like items, so once an item is defined in one figure, it may not be necessary to further discuss that item in subsequent figures.

[0035] Polarization Bragg gratings (PBG) or polarization volume gratings (PVG) made of liquid crystal (LC) or liquid crystal polymer (LCP) can achieve a wider field of view (FOV). Polarization volume gratings are usually made by a holographic method in which the wave vectors of the target wave and the reference wave are added or subtracted using orthogonal polarization coherent light. Combining the holographic method with the polarization interference method, the interference pattern between the two waves with orthogonal circular polarizations produces the grating vector of the polarization volume grating. The grating period of the liquid crystal cell (LC cell) or LCP film can be obtained using the above method. In order to further control the wavelength and angular response of the grating, twist can also be applied to one or two layers of the LCP film. Unlike systems based on surface relief gratings, polarization volume gratings are a polarization active mechanism.

[0036] In this regard, the present disclosure investigates the possibility of multiplexing different angles of a light field by combining several polarizer gratings and other polarization elements into a stack. With the help of wide-angle liquid crystal polymer films, the polarization of one or all visible wavelengths can be controlled to be right-handed or left-handed circularly polarized. It was found that angular multiplexing of polarizer gratings can benefit augmented reality systems with extended field of view.

[0037] The present disclosure found that a transmissive polarizer grating generally has a longer operating wavelength than a reflective polarizer grating. Therefore, a transmissive polarizer grating operating in a transmissive mode is employed herein.

[0038] This disclosure proposes multiplexing the field of view (FOV) angle by using two stacked polarizer gratings, each responsible for half of the FOV. When these two polarizer gratings, each responsible for the positive and negative halves of the FOV, are stacked, the actual FOV can be extended to the full wide FOV angle. Because the azimuthal response of the input coupler grating (ICG) to the right differs from that to the left, stacking two polarizer gratings on each side of the image can be applied to either the right or left side of the image.

[0039] In this paper, angle-multiplexed polariton gratings are used to optimize the operating angle range of the polariton grating. The use of stacked angle-optimized polariton gratings can effectively extend the in-coupling FOV.

[0040] In one embodiment, Figure 1 As shown, the optical waveguide system includes a waveguide 100, an input coupler 300A, and an output coupler 303. The input coupler 300A is provided at the input side of the waveguide 100 and couples light into the waveguide 100. The output coupler 303 is provided at the output side of the waveguide 100 and couples light out of the waveguide 100.

[0041] The output coupler 303 may be a two-dimensional surface relief grating that can expand and outcouple the light. Such a two-dimensional surface relief grating can improve the uniformity of the displayed image. The two-dimensional surface relief grating may have a diamond lattice.

[0042] The input coupler 300A includes a right portion 301 and a left portion 302. Those skilled in the art will appreciate that, viewed from the light incident direction, the right portion 301 is located on the right side of the input coupler 300A, and the left portion 302 is located on the left side of the input coupler 300A.

[0043] like Figure 2 As shown, the right portion 301 includes a first polarizer grating 301A and a second polarizer grating 301B. The second polarizer grating 301B is stacked below the first polarizer grating 301A. The left portion 302 includes a third polarizer grating 302A and a fourth polarizer grating 302B. The fourth polarizer grating 302B is stacked below the third polarizer grating 302A.

[0044] The first polarizer grating 301A and the fourth polarizer grating 302B are polarizer gratings optimized for the right viewing angle of light. The third polarizer grating 302A and the second polarizer grating 301B are polarizer gratings optimized for the left viewing angle of light.

[0045] Optimization for the right / left side means that at least one property of the grating at the right / left side is better than at least one property of the grating at the left / right side. Herein, this property can be the field of view. For example, the first polarizer grating 301A and the fourth polarizer grating 302B have an asymmetric field of view, wherein the field of view of the right side is greater than the field of view of the left side. The third polarizer grating 302A and the second polarizer grating 301B have an asymmetric field of view, wherein the field of view of the left side is greater than the field of view of the right side.

[0046] In this embodiment, first polarizer grating 301A and second polarizer grating 301B are stacked together, but they have different optimizations. Similarly, third polarizer grating 302A and fourth polarizer grating 301B are stacked together, but they have different optimizations. By adopting these configurations, image uniformity across the viewing angle can be improved. Furthermore, diffraction efficiency can be improved.

[0047] like Figure 1 As shown, light / ray 201 on the right and light / ray 202 on the left enter the output coupler 303 and are coupled out of the waveguide 100 .

[0048] Because light / ray 201 and light / ray 202 have wide-angle responses, the out-coupling of these two beams into the two-dimensional surface relief grating 303 can have a wide field of view and maintain good RGB color uniformity, resulting in highly uniform color and brightness output from the two-dimensional surface relief grating 303. Furthermore, because the stacking of grating 301 preserves the high intensity on the right side of the input image, light / ray 201 inherits the high intensity and full RGB field of view, and continues to transmit to the right side of the eyebox, resulting in even better brightness and color uniformity. A similar situation applies to the left side.

[0049] For example, the field of view (FOV) of the first polarizer grating 301A and the fourth polarizer grating 302B is (-30°, 10°), and the field of view of the third polarizer grating 302A and the second polarizer grating 301B is (-10°, 30°).

[0050] For example, the first polarizer grating 301A, the second polarizer grating 301B, the third polarizer grating 302A, and the fourth polarizer grating 302B are transmissive polarizer gratings.

[0051] Figure 3 and Figure 4 : shows an optical waveguide system according to another embodiment. Figure 3 and Figure 4 As shown, the input coupler 300B further includes a central polarizer grating 304. The central polarizer grating 304 is disposed between the right portion 301 and the left portion 302. The central polarizer grating 304 is optimized for the central viewing angle and can further improve the brightness at the central viewing angle.

[0052] The central polarizer grating 304 has a symmetrical viewing angle that overlaps at least a portion of the viewing angles of the first polarizer grating 301A, the second polarizer grating 301B, the third polarizer grating 302A, and the fourth polarizer grating 302B.

[0053] For example, the field angle of the central polarizer grating 304 is (-15°, 15°).

[0054] Figure 5 FIG. 3 is a schematic structural diagram of an input coupler 300C according to another embodiment. The input coupler 300C can be used for Figure 1 or Figure 3 The optical waveguide system shown.

[0055] exist Figure 5 In the input coupler 300C, the first polarizer grating 301A and the third polarizer grating 302A are made of liquid crystal polymer in the first liquid crystal layer 301E, and the second polarizer grating 301B and the fourth polarizer grating 302B are made of liquid crystal polymer in the second liquid crystal layer 301F.

[0056] The first liquid crystal layer 301E and the second liquid crystal layer 301F have the same period variation along the grating plane, but have different grating vectors and / or period localizations.

[0057] In this embodiment, since the four gratings are implemented in two liquid crystal layers, and both layers have the same periodic variation, the structure is produced in a continuous manner, reducing the energy retained at discontinuous locations. This improves diffraction efficiency and the performance of the input coupler.

[0058] The optical waveguide system further includes a polarizer, which is disposed before the input coupler 300A, 300B, or 300C. The polarizer can convert light into polarized light, which can be diffracted by the output coupler 300A, 300B, or 300C. This allows for efficient processing of polarized light in the optical waveguide system and reduces stray light in the system.

[0059] The polarizer grating in various embodiments may be a liquid crystal based polarizer grating.

[0060] The field of view angles of the polarization volume gratings in different embodiments may intentionally have some overlap to ensure that there is no transmission gap in the image in terms of angle. Table 1 lists the field of view angle and wavelength response of each polarization volume grating PVG.

[0061] Table 1: Summary of grating working angles

[0062]

[0063] Figure 6 A schematic block diagram illustrating an electronic device according to an embodiment.

[0064] exist Figure 6In the embodiment, electronic device 60 includes display 61 and optical waveguide system 62. Display 61 generates image light. Optical waveguide system 62 may be the optical waveguide system described above and receives the image light. Optical waveguide system 62 includes input coupler 63, waveguide 65, and output coupler 64, as described above. Optical waveguide system 62 may further include polarizer 66, as described above, to convert the image light into polarized image light, which is then processed by input coupler 63.

[0065] Figure 7 An example of an electronic device according to an embodiment is shown. Figure 7 In the embodiment, the electronic device 71 may be a near-eye display, such as AR glasses. The electronic device 71 may include a display 73 and an optical waveguide system 72 as described above.

[0066] Although some specific embodiments of the present invention have been described in detail using examples, those skilled in the art should understand that the above examples are only for illustration and are not intended to limit the scope of the present disclosure.

Claims

1. An optical waveguide system comprising: waveguide; an input coupler, disposed on an input side of the waveguide and coupling light into the waveguide; as well as an output coupler, disposed at an output side of the waveguide and coupling light out of the waveguide; wherein the input coupler comprises a right part and a left part, Wherein, viewed from the light incident direction, the right portion is located on the right side of the input coupler, and the left portion is located on the left side of the input coupler. wherein the right portion includes a first polarizer grating and a second polarizer grating stacked below the first polarizer grating, wherein the left portion includes a third polarizer grating and a fourth polarizer grating stacked below the third polarizer grating, Wherein, viewed from the light incident direction, the first polarizer grating and the second polarizer grating are both located on the right side of the third polarizer grating and the fourth polarizer grating, The first polarizer grating and the fourth polarizer grating are polarizer gratings optimized for the right viewing angle of light. The third polarizer grating and the second polarizer grating are polarizer gratings optimized for the left viewing angle of light. wherein the first polarizer grating and the fourth polarizer grating have a first asymmetric viewing angle, wherein the viewing angle of the right portion is greater than the viewing angle of the left portion, and The third polarizer grating and the second polarizer grating have a second asymmetric viewing angle, wherein the viewing angle of the left portion is greater than the viewing angle of the right portion.

2. The optical waveguide system according to claim 1, wherein the field angles of the first polarizer grating and the fourth polarizer grating are (-30°, 10°), and The viewing angles of the third polarizer grating and the second polarizer grating are (-10°, 30°).

3. The optical waveguide system according to claim 1 , further comprising: A central polarizer grating is disposed between the right portion and the left portion and is optimized for a central field of view.

4. The optical waveguide system of claim 3, wherein the central polarizer grating has a symmetric viewing angle that overlaps at least a portion of the viewing angles of the first polarizer grating, the second polarizer grating, the third polarizer grating, and the fourth polarizer grating. 5 . The optical waveguide system according to claim 4 , wherein the field angle of the central polarizer grating is (−15°, 15°).

6. The optical waveguide system of claim 1, wherein the output coupler comprises a two-dimensional surface relief grating.

7. The optical waveguide system of claim 1, wherein the first polarizer grating, the second polarizer grating, the third polarizer grating, and the fourth polarizer grating are transmissive polarizer gratings.

8. The optical waveguide system according to claim 1 , further comprising: A polarizer is provided before the input coupler and converts the light into polarized light, which can be diffracted by the output coupler.

9. The optical waveguide system according to claim 1 , wherein the first polarizer grating and the third polarizer grating are made of liquid crystal polymer in the first liquid crystal layer, in, The second polarizer grating and the fourth polarizer grating are made of liquid crystal polymer in the second liquid crystal layer, and The first liquid crystal layer and the second liquid crystal layer have the same period variation along the grating plane, but have different grating vectors and / or period positioning.

10. An electronic device comprising: a display, which generates image light; as well as The optical waveguide system according to claim 1, wherein the image light is received.

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