Rainbow pattern elimination AR display device based on angle correlation filtering film

Abstract

The invention provides a rainbow pattern elimination AR display device based on an angle correlation filtering film, and relates to the field of augmented reality display. The device comprises a micro display, an optical waveguide structure lens and angle correlation filtering films on the surfaces of the two sides of the lens. The angle correlation filtering film sequentially comprises a second protection layer, a second grating layer and a substrate layer; the second grating layer is composed of light-transmitting units and light-shading units in an alternating mode. The shading unit adopts an asymmetric structure, and the asymmetric angle response of the angle correlation filtering film is matched with the lens coupling-out grating; and the second grating layer adopts a special arrangement mode to inhibit the diffraction effect. According to the augmented reality display device, large-angle external environment light is prevented from entering the grating area through the angle correlation filtering film, so that rainbow lines of the augmented reality display device are eliminated, the augmented reality display device has the advantages of being insensitive to wavelength and polarization and light and thin, diffraction artifacts cannot be additionally introduced, and the imaging quality and user experience of the augmented reality display device can be improved.

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 filtering film for eliminating rainbow patterns. Background Art

[0002] The augmented reality display device superimposes virtual images on the real world to achieve mutual reinforcement and enhancement between real scenes and virtual information, which enables users to see the external real world and virtual images at the same time, enriching people's visual experience. This augmented reality display device consists of a micro-display and a lens with an optical waveguide structure, in which the micro-display serves as an image source, and the virtual image emitted is imaged to the human eye through a lens with a transparent optical waveguide structure. The optical waveguide lens consists of a waveguide layer, a grating layer and a protective layer. After the light is emitted from the image source, it enters the waveguide layer, where it is fully reflected and propagates back and forth, and finally reaches the grating layer and is coupled out of the waveguide due to the diffraction effect, so that the observer can observe the virtual image and the surrounding real scene at the same time.

[0003] However, existing augmented reality technology faces the problem of rainbow effect. When external large-angle ambient light is incident on the grating layer, due to the dispersion effect of diffraction, light of different wavelengths will be diffracted to different degrees, forming rainbow patterns, which seriously affects the wearer's experience. In addition, the more open the augmented reality display device is, the more light from the external ambient light source can enter the system, especially large-angle light from the side or behind the user will cause serious rainbow artifacts.

[0004] The present invention suppresses large-angle external ambient light from being incident on the grating area through an angle-dependent filter film, thereby eliminating the rainbow patterns of the augmented reality display device. It has the advantages of wavelength insensitivity, polarization insensitivity, and lightness and thinness, 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 view of the rainbow effect of current augmented reality display devices, the present invention provides an AR display device with rainbow elimination based on an angle-dependent filter film.

[0006] In order to achieve the above object, the technical solution adopted by the present invention to solve the technical problem is as follows:

[0007] On the one hand, the present invention proposes a rainbow pattern elimination AR display device 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 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 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 out through the out-coupling grating, and the external environment object beam directly transmits the optical waveguide structure lens and combines with the image beam to realize AR display;

[0009] 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, and 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 light-transmitting units and light-shielding units alternately, and is used to limit the passage of incident light beams exceeding the cutoff angle of the second grating layer; the first grating layer and the second grating layer both have asymmetric angle response characteristics, the asymmetric angle response characteristics of the angle-dependent filter film are matched with the out-coupling grating, and the asymmetric angle response characteristics of the two angle-dependent filter films are complementary.

[0010] On the other hand, the present invention also provides a method for preparing an angle-dependent filter film, wherein the angle-dependent filter film is used in the above-mentioned device, and the preparation method comprises:

[0011] S1: According to the design index requirements and process limitations, determine the cutoff angle, high transmittance requirements, asymmetric angle response characteristics, maximum relative intensity of diffraction orders and transmittance cutoff effect required for the two angle-dependent filter films;

[0012] S2: According to the required cut-off angle, high transmittance requirement, and asymmetric angle response characteristics, the shading unit width b, height h, and period p of the angle-dependent filter film are calculated using the following formula:

[0013]

[0014] Where θ1 and θ2 represent the two cutoff angles of the angle-dependent filter film, and θ3 represents the maximum angle of high transmittance;

[0015] S3: Selecting a quasi-periodic grating arrangement or a zigzag grating arrangement as the grating arrangement of the second grating layer. If the quasi-periodic grating arrangement is selected, random perturbations are added on the basis of the determined period p to determine the center positions of all shading units in the x-direction, so that the second grating layer satisfies the required maximum relative intensity of the diffraction order and the transmittance cutoff effect; if the zigzag grating arrangement is selected, the length a and width c of the repeating unit of the shading unit are determined, so that the second grating layer satisfies the required maximum relative intensity of the diffraction order and is within the process limit;

[0016] S4: According to 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 respectively 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, so that the asymmetric angle response characteristics of the angle-dependent filter film are matched with the out-coupling grating, and the asymmetric angle 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 being incident on the grating area through an angle-dependent filter film, thereby eliminating the rainbow patterns 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 pattern elimination solutions, the present invention has the advantages of wavelength insensitivity, polarization insensitivity, and lightness, and will not introduce additional diffraction artifacts, nor 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 It is a light path diagram of a conventional augmented reality display device and an augmented reality display device for eliminating rainbow patterns based on an angle-dependent filter film in one embodiment of the present invention;

[0021] Figure 2 It is a 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 A schematic diagram of the structure of an angle-dependent filter film in one embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of the structure of the second grating layer 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 FIG. 1 is a schematic diagram of a filter film structure with a zigzag grating arrangement in one embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[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, wherein 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] At present, the diffraction light waveguide augmented reality display device generally has the rainbow pattern phenomenon. The rainbow pattern phenomenon refers to the phenomenon that when the external environment large-angle light is incident on the light waveguide structure lens of the augmented reality display device, diffraction dispersion occurs and rainbow patterns are generated. The rainbow pattern phenomenon seriously affects the imaging quality and user experience of the augmented reality display device. In order to solve this problem, the present invention proposes an angle-dependent filter film. The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Example 1

[0032] This embodiment provides an augmented reality display device for eliminating rainbow patterns based on an angle-dependent filter film, such as 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 filtering 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, wherein the waveguide layer faces the human eye when in use, the first protective layer faces the external environment, and the first grating layer is sandwiched between the first protective layer and the waveguide layer, and includes an in-coupled grating and an out-coupled grating. The micro display is used to send an image beam to 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 coupling grating, propagates through total reflection in the waveguide layer, and enters the human eye after diffraction and deflection by the coupling grating, realizing the display of virtual images; at the same time, the external environment object beam directly enters the human eye through the optical waveguide structure lens, realizing the combination of real scenes and virtual images; when the incident angle of the external environment object beam is too large, this type of beam is called the external environment large-angle beam, which is refracted at the interface of the protective layer or the waveguide layer, propagates to the coupling grating to produce diffraction dispersion, and thus causes the rainbow pattern phenomenon.

[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 object beam from the external environment 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 comprises 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 to form a micro shutter structure, such as Figure 3 The light-transmitting unit may be a cavity structure, and the light-shielding unit may 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, such as 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 do not fit 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 turns to the interface normal at an acute angle, clockwise is a positive angle, and counterclockwise is a negative angle; 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 the positive-angle incident light beam is asymmetric with that to the negative-angle incident light beam, that is, it has an asymmetric angle response characteristic.

[0039] Due to the second grating layer structure of the angle-dependent filter film, the angle-dependent filter film has a maximum high transmittance angle and two cutoff angles. There is a flat-top high transmittance distribution on one side of the film transmittance function, and the maximum absolute value of the angle of the flat-top distribution is the maximum high transmittance angle; the incident light beam between the two cutoff angles can pass through the angle-dependent filter film (transmittance is greater than 0), otherwise it cannot pass (transmittance is equal to 0), and the angle limiting this range is the cutoff angle. The smoother the transmittance change near the cutoff angle, the worse the transmittance cutoff effect, and vice versa. The angle-dependent filter film eliminates the rainbow pattern phenomenon caused by large-angle light beams by preventing the transmission of light beams exceeding the cutoff angle.

[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 in a straight line along the y direction, and the right angle side that fits 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 center position of the nth shading unit in the x direction, p is the period of the shading unit, Δx is the random disturbance, rand(.) is the random function, and k is the coefficient, which is preferably 3 to 5.

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

[0046] Example 2

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

[0048] Step (1) Determine the working wavelength, cut-off angle, high transmittance requirement, asymmetric angle response characteristics, maximum relative intensity of diffraction order, transmittance cut-off effect, area and angle transmittance function of the angle-dependent filter film according to the design index requirements and process limitations. The high transmittance requirement includes the high transmittance angle range and the 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 angle response characteristics are different responses under incident light beams at positive and negative angles.

[0049] The angle 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 according to the cut-off angle, high transmittance requirement, and asymmetric angle response characteristics obtained in step (1), so that the angle-dependent filter film meets the angle transmittance requirement required by the design index. The calculation method is as follows: Figure 4 shown.

[0051]

[0052]

[0053]

[0054] Among them, 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, area and process level of the diffraction order obtained in step (1); the process difficulty of the quasi-periodic grating arrangement mode is not great, and it is suitable for suppressing the diffraction effect of a large area, but it will affect the transmittance cutoff effect of the cutoff angle; the zigzag grating arrangement mode has a better diffraction effect suppression capability, and is suitable for the situation where the diffraction effect suppression effect is high, but the process difficulty is slightly greater, and additional diffraction orders with lower relative intensity will be generated in other directions; if the quasi-periodic grating arrangement is selected, the x-direction center position of the shading unit is determined according to formulas (1)-(2), thereby increasing the disturbance to determine the x-direction center position of all shading units, and the coefficient k of formulas (1)-(2) is determined by the required maximum relative intensity of the diffraction order and the transmittance cutoff effect; if the zigzag grating arrangement is selected, the length a of the repeating unit of the zigzag shading unit and the width c in the x-direction are determined according to the maximum relative intensity of the diffraction order and the process level.

[0056] Step (4) preparing an angle-dependent filter film: using nanoimprinting technology to prepare a second grating layer on a high-transmittance substrate, and bonding the filter grating to the second protective layer, thereby preparing an angle-dependent filter film.

[0057] Step (5) adjusts the orientation of the angle-dependent filter film according to the asymmetric angular response characteristics of the out-coupling grating and the angle-dependent filter film, and adheres the angle-dependent filter 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 angular response characteristics of the angle-dependent filter film match the out-coupling 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.

[0058] The meaning of the matching of the asymmetric angle response characteristics is that the diffraction dispersion response of the out-coupled grating and the filter absorption response of the filter film are stronger when they are incident at a positive angle than at a negative angle, or stronger when they are incident at a negative angle than at a positive angle. The asymmetric angle 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. For the light beam of an object in the external environment, the transmittance of one is higher when it is incident at a positive angle than when it is incident at a negative angle, but the transmittance of the other is higher when it is incident at a negative angle than when it is incident at a positive angle, thereby making the relative illumination of the image uniform.

[0059] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A rainbow-strip elimination AR display device 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 micro display is used to provide an image 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 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 out through the out-coupling grating, and 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, and 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 light-transmitting units and light-shielding units alternately, and is used to limit the passage of incident light beams exceeding the cutoff angle of the second grating layer; the first grating layer and the second grating layer both have asymmetric angle response characteristics, the asymmetric angle response characteristics of the angle-dependent filter film are matched with the out-coupling grating, and the asymmetric angle response characteristics of the two angle-dependent filter films are complementary.

2. The rainbow-strip elimination AR display device based on angle-dependent filter film according to claim 1, characterized in that: The base layer is attached 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-eliminating 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-strip elimination AR display device based on angle-dependent filter film according to claim 1, characterized in that: The light-transmitting unit is a cavity structure.

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

6. The rainbow-strip elimination AR display device based on angle-dependent filter film according to claim 1, characterized in that: 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 rainbow-strip elimination AR display device 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 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 extending 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: According to the design index requirements and process limitations, determine the cutoff angle, high transmittance requirements, asymmetric angle response characteristics, maximum relative intensity of diffraction orders and transmittance cutoff effect required for the two angle-dependent filter films; S2: According to the required cut-off angle, high transmittance requirement, and asymmetric angle response characteristics, the shading unit width b, height h, and period p of the angle-dependent filter film are calculated using the following formula: 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 as the grating arrangement of the second grating layer. If the quasi-periodic grating arrangement is selected, random perturbations are added on the basis of the determined period p to determine the center positions of all shading units, so that the second grating layer satisfies the required maximum relative intensity of the diffraction order and the transmittance cutoff effect; if the zigzag grating arrangement is selected, the length a and width c of the repeating unit of the shading unit are determined, so that the second grating layer satisfies the required maximum relative intensity of the diffraction order and is within the process limit; S4: According to 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 respectively 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, so that the asymmetric angle response characteristics of the angle-dependent filter film are matched with the out-coupling grating, and the asymmetric angle 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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