An angularly dependent filter film based rainbow stripe cancellation ar display device

Abstract

The application provides an AR display device based on an angle-dependent filtering film, and relates to the field of augmented reality display.The application comprises a micro display, a light waveguide structure lens and an angle-dependent filtering film on the surfaces of the two sides of the lens; the angle-dependent filtering film comprises a second protective layer, a second grating layer and a base layer in sequence; the second grating layer is composed of light-transmitting units and light-blocking units alternately; the light-blocking units adopt an asymmetric structure, the asymmetric angle response of the angle-dependent filtering film is matched with the out-coupling grating of the lens; and the second grating layer adopts a special arrangement mode to suppress the diffraction effect.The application suppresses the incidence of external ambient light at a large angle into the grating area through the angle-dependent filtering film, thereby eliminating the rainbow stripes of the augmented reality display device, has the advantages of wavelength insensitivity, polarization insensitivity, lightness and thinness, does not introduce diffraction artifacts additionally, and helps to improve the imaging quality and user experience of the augmented reality display device.

Description

Technical Field

[0001] The present invention relates to the field of augmented reality, and in particular to an AR display device based on an angle-dependent filter film for eliminating rainbow patterns. Background Art

[0002] Augmented reality displays superimpose virtual images on the real world, complementing and enhancing the real scene and virtual information. This allows users to simultaneously see both the real world and the virtual image, enriching their visual experience. This augmented reality display device consists of a microdisplay and a lens with an optical waveguide structure. The microdisplay serves as the image source, and the virtual image it emits is imaged to the human eye through the transparent optical waveguide lens. The optical waveguide lens consists of a waveguide layer, a grating layer, and a protective layer. After emitting light from the image source, it enters the waveguide layer, where it propagates back and forth through total reflection, ultimately reaching the grating layer and being coupled out of the waveguide due to the diffraction effect. This allows the observer to simultaneously observe the virtual image and the surrounding real scene.

[0003] However, existing augmented reality technology faces the problem of rainbow artifacts. When ambient light from a wide angle strikes the grating layer, the dispersion effect of diffraction causes different wavelengths of light to be diffracted to varying degrees, creating rainbow artifacts that severely impact the wearer's experience. Furthermore, the more open an augmented reality display device is, the more light from ambient sources can enter the system. In particular, wide-angle light from the sides or behind the user can cause severe rainbow artifacts.

[0004] The present invention uses an angle-dependent filter film to suppress large-angle external ambient light from entering the grating area, thereby eliminating the rainbow patterns of the augmented reality display device. It has the advantages of wavelength insensitivity, polarization insensitivity, and lightweight, and does not introduce additional diffraction artifacts, which helps to improve the imaging quality and user experience of the augmented reality display device. Summary of the Invention

[0005] In response to the rainbow effect of current augmented reality display devices, the present invention provides an AR display device that eliminates rainbow patterns based on an angle-dependent filter film.

[0006] In order to achieve the above-mentioned purpose, the technical solutions adopted by the present invention to solve the technical problems are as follows:

[0007] On the one hand, the present invention proposes an AR display device for eliminating rainbow patterns based on an angle-dependent filter film, comprising a micro display, an optical waveguide structure lens, and two angle-dependent filter films;

[0008] The micro display is used to provide an image light beam; the optical waveguide structure lens comprises a first protective layer, a first grating layer and a waveguide layer in sequence, wherein the waveguide layer faces the human eye in use; the first grating layer comprises a coupling-in grating and a coupling-out grating, the coupling-in grating diffracts the image light beam to be coupled into the waveguide layer for total reflection propagation, and the image light beam is diffracted and coupled out through the coupling-out grating, and an external environment object light beam directly transmits through the optical waveguide structure lens and combines with the image light beam to realize AR display.

[0009] The two angle-dependent filtering thin films are respectively located on the outer surface of the first protective layer and the outer surface of the waveguide layer of the optical waveguide structure lens, and the angle-dependent filtering thin film comprises a second protective layer, a second grating layer and a substrate layer in sequence; the second grating layer is composed of light-transmitting units and light-blocking units alternately arranged, and is used to limit the incident light beam exceeding the cut-off angle of the second grating layer from passing through; the first grating layer and the second grating layer both have an asymmetric angle response characteristic, the asymmetric angle response characteristic of the angle-dependent filtering thin film is matched with the coupling-out grating, and the asymmetric angle response characteristics of the two angle-dependent filtering thin films are complementary.

[0010] In another aspect, the application further provides a preparation method of an angle-dependent filtering thin film, which is used in the above-mentioned device, and the preparation method comprises the following steps:

[0011] S1: according to the design index requirements and process limitations, the required cut-off angle, high transmittance requirement, asymmetric angle response characteristic, maximum relative intensity of diffraction order and transmittance cut-off effect of the two angle-dependent filtering thin films are determined;

[0012] S2: according to the required cut-off angle, high transmittance requirement and asymmetric angle response characteristic, the width b, height h and period p of the light-blocking unit of the angle-dependent filtering thin film are calculated, and the calculation formula is as follows:

[0013]

[0014] Wherein θ1 and θ2 represent two cut-off angles of the angle-dependent filtering thin film, and θ3 represents a maximum angle of high transmittance;

[0015] S3: the grating arrangement mode of the second grating layer is selected to be quasi-periodic grating arrangement or zigzag grating arrangement, if the quasi-periodic grating arrangement is selected, random disturbance is added on the basis of the determined period p to determine the x-direction center position of all light-blocking units, so that the second grating layer meets the required maximum relative intensity of diffraction order and transmittance cut-off effect; if the zigzag grating arrangement is selected, the length a and width c of the repeating unit of the light-blocking unit are determined, so that the second grating layer meets the required maximum relative intensity of diffraction order and is within the process limitation;

[0016] S4: Based on the results obtained in S2-S3, a second grating layer is prepared on the base layer, and the filter grating is laminated to the second protective layer, thereby preparing two angle-dependent filter films;

[0017] S5: Adjust the orientation of the angle-dependent filter film, and attach the two angle-dependent filter films to the outer surface of the first protective layer and the outer surface of the waveguide layer of the optical waveguide structure lens respectively, so that the asymmetric angular response characteristics of the angle-dependent filter film are matched with the outcoupling grating, and the asymmetric angular response characteristics of the angle-dependent filter film on the surface of the first protective layer are complementary to the angle-dependent filter film on the surface of the waveguide layer.

[0018] The beneficial effects of the present invention are:

[0019] The present invention suppresses large-angle external ambient light from entering the grating area through an angle-dependent filter film, thereby eliminating the rainbow stripes of the augmented reality display device. The angle-dependent filter film of the present invention adopts an asymmetric unit structure and has an asymmetric angle response, which can match the asymmetric angle response of the grating coupled out of the augmented reality display device. The angle-dependent filter film of the present invention adopts a special grating arrangement method, which can effectively suppress the diffraction effect of the film itself. Compared with the existing rainbow stripe elimination solutions, the present invention has the advantages of wavelength insensitivity, polarization insensitivity, and lightness and thinness, and does not introduce additional diffraction artifacts, nor does it increase the design difficulty and process difficulty of the optical waveguide lens, while taking into account mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The optical path diagram of a conventional augmented reality display device and an augmented reality display device that eliminates rainbow patterns based on an angle-dependent filter film according to an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the overall structure of an augmented reality display device for eliminating rainbow patterns based on an angle-dependent filter film in one embodiment of the present invention;

[0022] Figure 3 Schematic diagram of the angle-dependent filter film structure in one embodiment of the present invention;

[0023] Figure 4 Schematic diagram of the second grating layer structure in one embodiment of the present invention;

[0024] Figure 5 A schematic diagram of a filter film structure with a quasi-periodic grating arrangement in one embodiment of the present invention;

[0025] Figure 6 Schematic diagram of the filter film structure with a zigzag grating arrangement in one embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described and illustrated below in conjunction with specific embodiments. The embodiments are merely illustrative of the present disclosure and do not limit its scope. The technical features of the various embodiments of the present invention may be combined accordingly, provided that there is no conflict between them.

[0027] Before introducing the present invention, the keywords of the present invention are first explained:

[0028] Augmented Reality (AR) technology is a technology that superimposes virtual images and real scenes on the same screen or space, allowing users to see both the real world outside and virtual images.

[0029] Augmented reality display devices, such as AR glasses, include a microdisplay and an optical waveguide structure lens, in which the microdisplay serves as an image source, and the virtual image emitted is imaged to the human eye through a transparent optical waveguide structure lens.

[0030] Currently, diffractive waveguide augmented reality (AR) displays commonly suffer from rainbow streaks. This phenomenon occurs when ambient light at high angles strikes the AR device's waveguide lens, causing diffraction and dispersion. This phenomenon severely impacts the AR device's imaging quality and user experience. To address this issue, the present invention proposes an angle-dependent filter film. An embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0031] Example 1

[0032] This embodiment provides an augmented reality display device based on an angle-dependent filter film to eliminate rainbow stripes. Figure 1 、 2 shown.

[0033] The augmented reality display device includes a micro display for providing an image light beam, an optical waveguide structure lens for transmitting the image light beam, and an angle-dependent filter film on the surface of the optical waveguide structure lens for eliminating rainbow patterns.

[0034] The optical waveguide structure lens includes a first protective layer, a first grating layer, and a waveguide layer. The waveguide layer faces the human eye during use, while the first protective layer faces the external environment. The first grating layer is sandwiched between the first protective layer and the waveguide layer and includes an in-coupling grating and an out-coupling grating. The microdisplay is used to send an image beam into the waveguide layer.

[0035] If the angle-dependent filter film is not provided, the optical path diagram is as follows Figure 1As shown in the upper part, the image beam is coupled into the waveguide layer by the in-coupling grating, propagates through total internal reflection in the waveguide layer, and is diffracted and deflected by the out-coupling grating before entering the human eye, displaying the virtual image. Simultaneously, the external object beam is directly transmitted through the optical waveguide structure lens into the human eye, combining the real scene with the virtual image. When the incident angle of the external object beam is too large, this beam is called a high-angle external beam. It refracts at the interface of the protective layer or waveguide layer, propagates to the out-coupling grating, and generates diffraction dispersion, resulting in rainbow patterns.

[0036] In this embodiment, the angle-dependent filter films are arranged on both sides of the optical waveguide structure lens. The optical path diagram is as follows: Figure 1 As shown in the lower part, the large-angle beam from the external environment is absorbed by the filter film, and the image beam diffracted and deflected by the outcoupling grating and the external object beam are transmitted by the filter film.

[0037] The angle-dependent filter film is located on the outer surface of the first protective layer and the outer surface of the waveguide layer of the optical waveguide structure lens, such as Figure 2 The angle-dependent filter film includes a second protective layer, a second grating layer, and a base layer; wherein the second grating layer is composed of light-transmitting units and light-shielding units alternately, forming a micro shutter structure, such as Figure 3 The light-transmitting unit can be a cavity structure, and the light-shielding unit can be obtained by preparing a micro-nano structure using a template and then spraying a black body paint coating.

[0038] The shading unit adopts an asymmetric cross-sectional structure, and the second grating layer has an asymmetric angle-dependent response that matches the out-coupling grating in the optical waveguide structure lens. Figure 4 As shown. Specifically, the shading unit adopts a strip structure, and the cross-section of the strip structure is the same right triangle, and one of the right-angled sides of the right triangle is in close contact with the base layer; of the two surfaces of the shading unit that are not in contact with the base layer, the side perpendicular to the surface of the base layer is a vertical surface, and the other side is an inclined surface. For the light beam incident on the interface, the light is turned at an acute angle to the normal of the interface, with a positive angle being clockwise and a negative angle being counterclockwise; the angle between the vertical surface and the inclined surface of the shading unit is the maximum angle of high transmittance at a negative angle of incidence. The response of the second grating layer to a light beam incident at a positive angle is asymmetric to that to a light beam incident at a negative angle, that is, it has an asymmetric angle response characteristic.

[0039] Due to the second grating layer structure of the angle-dependent filter film, the film has a maximum high transmittance angle and two cutoff angles. A flat-top high transmittance distribution exists on one side of the film's transmittance function, with the angle with the maximum absolute value of the flat-top distribution representing the maximum high transmittance angle. Incident light beams between the two cutoff angles can pass through the angle-dependent filter film (transmittance greater than 0), but cannot (transmittance equal to 0). The angle defining this range is the cutoff angle. The flatter the transmittance variation near the cutoff angle, the worse the transmittance cutoff effect, and vice versa. By preventing light beams exceeding the cutoff angle from transmitting, the angle-dependent filter film eliminates the rainbow pattern phenomenon caused by large-angle beams.

[0040] The second grating layer adopts a special grating arrangement, including a quasi-periodic grating arrangement and a zigzag grating arrangement, which has the ability to suppress the diffraction effect.

[0041] The shading unit of the quasi-periodic grating arrangement extends linearly along the y direction, and the right angle side aligned with the base layer is in the x direction. Figure 5 As shown, the spacing between adjacent shading units is randomly perturbed based on the period p. Specifically, the center position of the shading unit in the x direction satisfies equations (1) and (2). Compared with the other arrangement method, the quasi-periodic grating arrangement is less difficult to process and is suitable for suppressing the diffraction effect over a large area. However, the diffraction effect suppression capability is weak, which has a negative impact on the transmittance cutoff effect at the cutoff angle.

[0042] x center (n) = n × p - 0.5 × p + Δx (1)

[0043]

[0044] where x center (n) is the x-direction center position of the nth shading unit, p is the period of the shading unit, Δx is the random disturbance, rand(.) is the random function, and k is the coefficient, preferably 3 to 5.

[0045] The shading units of the zigzag grating arrangement extend in a zigzag shape along the y direction, and the shading units are evenly distributed according to the period p, such as Figure 6 As shown, the y-axis transmittance of the second grating layer in this arrangement satisfies a trapezoidal periodic distribution. Compared to the previous arrangement, the zigzag grating arrangement has better diffraction effect suppression capabilities and is suitable for situations where diffraction effect suppression is required. However, it is more difficult to manufacture and will produce additional diffraction orders of relatively lower intensity in other directions.

[0046] Example 2

[0047] An angle-dependent filter film for eliminating rainbow patterns in an augmented reality display device, the preparation method of which comprises the following steps:

[0048] Step (1) determines parameters such as the operating wavelength, cutoff angle, high transmittance requirement, asymmetric angular response characteristics, maximum relative intensity of diffraction orders, transmittance cutoff effect, area, and angular transmittance function of the angle-dependent filter film based on design index requirements and process limitations. The high transmittance requirement includes a high transmittance angle range and a minimum transmittance within the range. For example, when the incident light beam is within the angle range of -30° to 40°, the transmittance of the film is greater than 70%. The asymmetric angular response characteristics are different responses under positive and negative angles of the incident light beam.

[0049] The angular transmittance function of the angle-dependent filter film is determined according to design requirements.

[0050] Step (2) calculates the shading unit size (including width b and height h) and structural period p of the angle-dependent filter film based on the cutoff angle, high transmittance requirement, and asymmetric angle response characteristics obtained in step (1), so that the angle-dependent filter film meets the angular transmittance requirement required by the design index. The calculation method is formula (3)-(5), as follows: Figure 4 shown.

[0051]

[0052]

[0053]

[0054] Here, θ1 represents the transmittance cutoff angle at negative angle of incidence, θ2 represents the transmittance cutoff angle at positive angle of incidence, and θ3 represents the maximum angle of high transmittance at negative angle of incidence.

[0055] Step (3) selects a grating arrangement mode (quasi-periodic grating arrangement or zigzag grating arrangement) of the second grating layer according to the maximum relative intensity of the diffraction order, the area and the process level obtained in step (1); the quasi-periodic grating arrangement mode has a small process difficulty and is suitable for diffraction effect suppression of a large area, but affects the transmittance cutoff effect of the cutoff angle; the zigzag grating arrangement mode has better diffraction effect suppression capability and is suitable for a case with a higher diffraction effect suppression effect, but has a slightly larger process difficulty and can additionally generate diffraction orders with lower relative intensity in other directions; if the quasi-periodic grating arrangement is selected, the x-direction center positions of all the shading units are determined according to the x-direction center positions of the shading units and formulae (1)-(2), and the coefficient k of formulae (1)-(2) is determined according to the maximum relative intensity of the diffraction order and the transmittance cutoff effect; if the zigzag grating arrangement is selected, the length a and the width c in the x-direction of the repeating unit of the zigzag-shaped shading unit are determined according to the maximum relative intensity of the diffraction order and the process level.

[0056] Step (4) prepares an angle-dependent filtering thin film: a second grating layer is prepared on a high-transmittance substrate using a nanoimprinting technology, and the filtering grating is attached to the second protective layer, thereby obtaining the angle-dependent filtering thin film.

[0057] Step (5) adjusts the orientation of the angle-dependent filtering thin film according to the asymmetric angle response characteristics of the out-coupling grating and the angle-dependent filtering thin film, attaches the angle-dependent filtering thin film to the outer surface of the first protective layer and the outer surface of the waveguide layer of the optical waveguide structure lens, so that the asymmetric angle response characteristics of the angle-dependent filtering thin film match the out-coupling grating, and the asymmetric angle response characteristics of the angle-dependent filtering thin film on the surface of the first protective layer are complementary to the angle-dependent filtering thin film on the surface of the waveguide layer.

[0058] The meaning of the matching of the asymmetric angle response characteristics is that the diffraction dispersion response of the out-coupling grating and the filtering absorption response of the filtering thin film are stronger at positive angle incidence than at negative angle incidence, or are stronger at negative angle incidence than at positive angle incidence. The complementary asymmetric angle response characteristics of the angle-dependent filtering thin film on the surface of the first protective layer and the angle-dependent filtering thin film on the surface of the waveguide layer are that, for the light beams of external environmental objects, one has a higher transmittance at positive angle incidence than at negative angle incidence, but the other has a higher transmittance at negative angle incidence than at positive angle incidence, so that the relative luminance of the image is uniform.

[0059] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. For ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. An AR display device with rainbow stripe elimination based on an angle-dependent filter film, characterized in that: It includes a micro display, an optical waveguide structure lens and two angle-dependent filter films; The microdisplay is used to provide an image beam. The optical waveguide structure lens sequentially comprises a first protective layer, a first grating layer, and a waveguide layer, wherein the waveguide layer faces the human eye when in use. The first grating layer comprises an in-coupling grating and an out-coupling grating. The in-coupling grating diffracts and couples the image beam into the waveguide layer for total reflection propagation, and diffracts and couples it out through the out-coupling grating. The external environment object beam directly transmits the optical waveguide structure lens and combines with the image beam to realize AR display. The two angle-dependent filter films are respectively located on the outer surface of the first protective layer and the outer surface of the waveguide layer of the optical waveguide structure lens. The angle-dependent filter film includes a second protective layer, a second grating layer, and a base layer in sequence. The second grating layer is composed of alternating light-transmitting units and light-shielding units, and is used to limit the passage of incident light beams that exceed the cutoff angle of the second grating layer. The first grating layer and the second grating layer both have asymmetric angular response characteristics. The asymmetric angular response characteristics of the angle-dependent filter film match those of the outcoupling grating, and the asymmetric angular response characteristics of the two angle-dependent filter films complement each other.

2. The rainbow-strip elimination AR display device based on the angle-dependent filter film according to claim 1, characterized in that: The base layer is adhered to the outer surface of the first protective layer or the outer surface of the waveguide layer of the optical waveguide structure lens.

3. The rainbow-relief AR display device based on an angle-dependent filter film according to claim 1, characterized in that: The shading unit is a strip structure, and the cross section of the strip structure is a same right triangle, and one of the right angle sides of the right triangle is in close contact with the base layer.

4. The rainbow-striping AR display device based on an angle-dependent filter film according to claim 1, characterized in that: The light-transmitting unit is a cavity structure.

5. The rainbow-relief AR display device based on an angle-dependent filter film according to claim 1, characterized in that: The shading unit is sprayed with a black paint coating.

6. The rainbow-relief AR display device based on an angle-dependent filter film according to claim 1, wherein: The second grating layer adopts a quasi-periodic grating arrangement, the shading units extend linearly in the same direction, and the spacing between adjacent shading units is randomly disturbed based on the period p.

7. The AR display device with rainbow stripe elimination based on angle-dependent filter film according to claim 6, characterized in that: The center position of the shading unit along the arrangement direction satisfies the following formula: x center (n)=n×p-0.5×p+Δx where x center (n) is the center position of the nth shading unit along the arrangement direction, p is the period of the shading unit, Δx is the random disturbance, rand(.) is the random function, and k is the coefficient.

8. The rainbow-strip elimination AR display device based on an angle-dependent filter film according to claim 1, characterized in that: The second grating layer adopts a zigzag grating arrangement, and the shading units extend in a zigzag shape. The extension direction is the same as that when the quasi-periodic grating arrangement is adopted, and the shading units are evenly distributed according to the period p.

9. A method for preparing an angle-dependent filter film, wherein the angle-dependent filter film is used in the device according to claim 1, characterized in that: The preparation method comprises: S1: Based on the design requirements and process limitations, determine the cutoff angle, high transmittance requirement, asymmetric angular response characteristics, maximum relative intensity of diffraction orders, and transmittance cutoff effect required for the two angle-dependent filter films; S2: Calculate the shading unit width b, height h, and period p of the angle-dependent filter film based on the required cutoff angle, high transmittance requirement, and asymmetric angle response characteristics. The calculation formula is: Where θ1 and θ2 represent the two cutoff angles of the angle-dependent filter film, and θ3 represents the maximum angle of high transmittance; S3: Selecting a quasi-periodic grating arrangement or a zigzag grating arrangement for the second grating layer. If the quasi-periodic grating arrangement is selected, adding random perturbations to the determined period p to determine the center positions of all shading units so that the second grating layer meets the required maximum relative intensity of the diffraction order and transmittance cutoff effect. If the zigzag grating arrangement is selected, determining the length a and width c of the repeating unit of the shading unit so that the second grating layer meets the required maximum relative intensity of the diffraction order and is within the process limit. S4: Based on the results obtained in S2-S3, a second grating layer is prepared on the base layer, and the filter grating is laminated to the second protective layer, thereby preparing two angle-dependent filter films; S5: Adjust the orientation of the angle-dependent filter film, and attach the two angle-dependent filter films to the outer surface of the first protective layer and the outer surface of the waveguide layer of the optical waveguide structure lens respectively, so that the asymmetric angular response characteristics of the angle-dependent filter film are matched with the outcoupling grating, and the asymmetric angular response characteristics of the angle-dependent filter film on the surface of the first protective layer are complementary to the angle-dependent filter film on the surface of the waveguide layer.

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