A near-eye display viewpoint spacing control method for expanding the field of view

Abstract

The present invention relates to a method for controlling viewpoint spacing for near-eye displays capable of expanding the field of view. The method utilizes an array of output coupling elements in a waveguide system to achieve viewpoint spacing control. Multiple first output coupling elements are arranged side by side, closely aligned, and in close proximity on the waveguide surface to form an array, for multiple coupling out of first-type circularly polarized light, thereby achieving multiple first-type viewpoints. Multiple second output coupling elements are arranged side by side, closely aligned, or spaced apart, in close proximity above the first output coupling elements to form an array, for multiple coupling out of second-type circularly polarized light, thereby achieving multiple second-type viewpoints. The first and second viewpoints formed by the arrays of the first and second output coupling elements are spaced to conform to the interpupillary distance of the human eye. The diameters of the first and second output coupling elements can be up to twice the spatial spacing between the viewpoints, thereby expanding the field of view while maintaining the spatial spacing of the viewpoints consistent with the interpupillary distance of the human eye. This method achieves both a wide field of view and an appropriate viewpoint spacing.

Description

Technical Field

[0001] The present invention relates to the field of near-eye display technology, and in particular to a near-eye display viewpoint spacing control method capable of expanding the field of view. Background Art

[0002] Augmented reality (AR) enables the human eye to simultaneously see virtual images and the real environment by overlaying digital content with the real world. To achieve a comfortable visual experience, AR display systems need to maintain a large field of view while also accommodating a large eyebox. Retinal scanning methods use off-axis lens couplers to form a Maxwell view directly on the observer's retina. Its FOV is directly determined by the f-number (F#) of the coupler lens and is therefore unbounded, but it is affected by the tiny eyebox of a single Maxwell view. To enlarge the eyebox, the observation point needs to be multiplied or rotated. Traditional waveguide displays replicate the exit pupil through total internal reflection (TIR) ​​of propagating light to provide a large eyebox without sacrificing FOV. However, in traditional waveguide displays, the light propagation angle is limited by the lower and upper limits of the TIR conditions to maintain good uniformity of the outcoupled light, thus setting a theoretical limit on the total field of view. This limitation is largely due to the use of an outcoupler, which is typically a grating with a fixed deflection angle but no optical power. In order to maintain a large field of view while taking into account a large eye box, we replace the grating without any optical power with an element with optical power, such as a lens array. In this way, we can transfer the limitation of the light propagation angle to the element with optical power.

[0003] Due to the method of combining optical waveguides and retinal scanning, the observer can observe a clear image directly at the viewpoint or observe the overall image formed by the stack of Maxwell views at a distance. However, for the normal viewing experience of a glasses-type AR display, the distance from the viewer's pupil to the glasses is about 1 cm. If you want to observe the image of the viewpoint at a normal viewing experience distance and maintain a large field of view, the size of each small lens also needs to be large accordingly. When designing such a near-eye display system, the human eye should also be considered, that is, the size of the small lens should not exceed the human pupil. Therefore, it is difficult to simultaneously take into account the appropriate viewpoint spacing and a large field of view angle at a normal viewing experience distance using the method combining optical waveguides and retinal scanning. Summary of the Invention

[0004] The object of the present invention is to provide a near-eye display viewpoint spacing control method capable of expanding the field of view, wherein the method can ensure a larger field of view while taking into account an appropriate viewpoint spacing.

[0005] To achieve the above objectives, the present invention employs a technical solution: a method for controlling viewpoint spacing for near-eye display capable of expanding the field of view, wherein the viewpoint spacing is controlled through an array of output coupling elements of a waveguide system. A plurality of identical first output coupling elements are provided and arranged in close proximity, side by side, on the surface of the waveguide to form an array, for multiple coupling out first-type circularly polarized light that matches and responds to the first output coupling elements, thereby achieving multiple first-type viewpoints. A plurality of identical second output coupling elements are provided and arranged in close proximity, side by side, or at intervals, above the first output coupling elements to form an array, for multiple coupling out second-type circularly polarized light that matches and responds to the second output coupling elements, thereby achieving multiple second-type viewpoints. The first-type viewpoints formed by the array of first output coupling elements and the second-type viewpoints formed by the array of second output coupling elements are arranged in a manner that conforms to the interpupillary distance of the human eye. The diameters of the first and second output coupling elements can be twice the spatial spacing between the viewpoints, thereby effectively expanding the field of view while ensuring that the spatial spacing between the viewpoints conforms to the interpupillary distance of the human eye.

[0006] Furthermore, the first output coupling element and the second output coupling element are focusing diffraction elements with polarization characteristics manufactured using chiral liquid crystal (CLC) polarization holography. The first output coupling element converges a first type of circularly polarized light image with the same chirality as the first output coupling element at the human eye to form a first type of viewpoint, and the second output coupling element converges a second type of circularly polarized light image with the same chirality as the second output coupling element at the human eye to form a second type of viewpoint. The F#, i.e., f-value, of the first output coupling element and the second output coupling element are the same to ensure that the field of view angles of the first type of viewpoint and the second type of viewpoint are the same.

[0007] Furthermore, the first type of viewpoint is formed by the first type of circularly polarized convergent light, and the second type of viewpoint is formed by the second type of circularly polarized convergent light; the viewpoints are arranged in a cross-arrangement by the first type of viewpoint and the second type of viewpoint diffracted by the first output coupling element array and the second output coupling element array respectively, the viewpoint spacing formed by the first output coupling element array is twice the diameter of the human eye pupil, and the viewpoint spacing formed by the second output coupling element array is twice the diameter of the human eye pupil, then the spacing of the cross-arranged viewpoints conforms to the distance of the human eye pupil diameter, and the spacing between the center of the first output coupling element and the center of the second output coupling element also conforms to the distance of the human eye pupil diameter.

[0008] Furthermore, the field of view angle is no longer limited by the outcoupled light propagation angle, but is limited by the output coupling element, and the field of view angle FOV is only determined by the F# of the output coupling element, or by the entrance pupil diameter D and the focal length f, satisfying the formula As a result, the field of view can exceed the upper limit of traditional waveguides.

[0009] Furthermore, the waveguide system includes an input coupling region, a waveguide, and an output coupling region; the input coupling region includes at least a first input coupling element and a second input coupling element having polarization characteristics, or is composed of an array of the first and second input coupling elements; the first input coupling element is used to couple an imaging beam of a first type of circularly polarized light into the waveguide at a first diffraction angle to form total reflected light; the second input coupling element is used to couple an imaging beam of a second type of circularly polarized light into the waveguide at a second diffraction angle to form total reflected light; the waveguide surface is provided with an input coupling region and an output coupling region, for propagating the total reflected light diffracted from the input coupling region to the output coupling region; the output coupling region includes at least a first output coupling element and an array thereof, and a second output coupling element and an array thereof, having polarization characteristics; the array of the first output coupling elements matches the first input coupling element to respond to the same first type of circularly polarized light, for converging the first type of circularly polarized light to form a first type of viewpoint and redirecting it into the human eye; the second output coupling element matches the second input coupling element to respond to the same second type of circularly polarized light, for converging the second type of circularly polarized light to form a second type of viewpoint and redirecting it into the human eye.

[0010] Furthermore, the first input coupling element and the second input coupling element are reflective or transmissive polarization holographic gratings, which diffract left-handed circularly polarized light images and right-handed circularly polarized light images at first and second diffraction angles, respectively, and the first and second diffraction angles are the same to ensure the same viewpoint spacing. The first input coupling element and the second input coupling element are located on the same side or on opposite sides of the waveguide surface. If they are on the same side, the first input coupling element and the second input coupling element are arranged side by side, closely attached to each other, or spaced apart. If they are on opposite sides, the first input coupling element and the second input coupling element overlap in the waveguide thickness direction.

[0011] Furthermore, the waveguide is a single-layer planar waveguide or a single-layer curved waveguide.

[0012] Furthermore, the waveguide system can be a retinal projection display system, in which the circularly polarized light image beam is coupled into the waveguide through the input coupling region at a set diffraction angle and a set position for total reflection, and finally, in the output coupling region, the first and second types of circularly polarized light image beams are converged into a viewpoint at the human eye through the first output coupling element and the second output coupling element, and are directly projected onto the retina of the human eye to form an image without being affected by the focusing of the human eye.

[0013] Furthermore, the positions and sizes of the first input coupling element, the second input coupling element, the first output coupling element, and the second output coupling element are strictly arranged on the surface of the waveguide according to the designed viewpoint spacing and field of view angle; assuming that the waveguide thickness is d, the center spacing between the first output coupling elements is D1, and the center spacing between the second output coupling elements is D2, then the formula is: The first diffraction angle θ1 and the second diffraction angle θ2 are calculated, and then the positions of the first input coupling element and the second input coupling element are deduced based on the first diffraction angle θ1, the second diffraction angle θ2 and the total internal reflection of the waveguide. The size of the first input coupling element does not exceed 2D1, and the size of the second input coupling element does not exceed 2D2. The grating tilt angle and grating period inside the grating are both derived from the desired designed diffraction angle and operating wavelength.

[0014] Compared with the existing technology, the present invention has the following beneficial effects: this method uses waveguides to expand the pupil and realize retinal projection display, which can not only expand the field of view angle and expand the eye box, but also effectively shorten the distance between adjacent viewpoints while ensuring a large field of view angle, which is more in line with the normal observation experience of the human eye. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the application structure of the method for controlling the viewpoint distance of near-eye display capable of expanding the field of view provided in Example 1 of the present invention;

[0016] Figure 2 A schematic diagram of the propagation of left-handed circularly polarized light in the application structure of the method for controlling the viewpoint distance of near-eye display capable of expanding the field of view provided in Example 1 of the present invention;

[0017] Figure 3 A schematic diagram of the propagation of right-handed circularly polarized light in the application structure of the method for controlling the viewpoint distance of near-eye display capable of expanding the field of view provided in Example 1 of the present invention;

[0018] Figure 4 Schematic diagram of the operation of the left-handed reflective polarization volume holographic grating in Example 1 of the present invention;

[0019] Figure 5 Schematic diagram of the operation of the left-handed transmissive polarization holographic grating in Example 1 of the present invention;

[0020] Figure 6 Schematic diagram of the working method of the viewpoint distance control method in Example 1 of the present invention;

[0021] Figure 7 A schematic diagram of an application structure of a method for controlling viewpoint spacing of near-eye display capable of expanding the field of view provided in Example 2 of the present invention;

[0022] Figure 8 A schematic diagram of another application structure of the method for controlling the viewpoint distance of near-eye display capable of expanding the field of view provided in Example 2 of the present invention;

[0023] Figure 9 A schematic diagram of another application structure of the method for controlling the viewpoint distance of near-eye display capable of expanding the field of view provided in Example 2 of the present invention;

[0024] Figure 10 A schematic diagram of the application structure of the method for controlling the viewpoint distance of near-eye display capable of expanding the field of view provided in Example 3 of the present invention;

[0025] Figure 11 This is a schematic diagram of the gaze matching effect in the application structure of a near-eye display viewpoint distance control method capable of expanding the field of view provided in Example 3 of the present invention.

[0026] The reference numerals are as follows:

[0027] Figure 1 Middle: 100 - slab waveguide; 101 - left-handed reflective polarizer holographic grating; 102 - right-handed reflective polarizer holographic grating; 103 - right-handed and left-handed reflective polarizer liquid crystal lens; 104 - left-handed reflective polarizer liquid crystal lens; 105 - human eye; 201 - left-handed parallel beam; 202 - left-handed totally reflected beam; 203 - left-handed converging light; 204 - right-handed parallel beam; 205 - right-handed totally reflected beam; 206 - right-handed converging light; 301 - first viewpoint; 302 - second viewpoint;

[0028] Figure 2 Center: 100 - slab waveguide; 101 - left-handed reflective polarization holographic grating; 102 - right-handed reflective polarization holographic grating; 103 - right-handed and left-handed reflective polarization liquid crystal lens; 104 - left-handed reflective polarization liquid crystal lens; 105 - human eye; 201 - left-handed parallel light beam; 202 - left-handed totally reflected light beam; 203 - left-handed converging light; 301 - first-class viewpoint;

[0029] Figure 3 Middle: 100 - slab waveguide; 101 - left-handed reflective polarization holographic grating; 102 - right-handed reflective polarization holographic grating; 103 - right-handed and left-handed reflective polarization liquid crystal lens; 104 - left-handed reflective polarization liquid crystal lens; 105 - human eye; 204 - right-handed parallel light beam; 205 - right-handed totally reflected light beam; 206 - right-handed converging light; 302 - second viewpoint;

[0030] Figure 4 Middle: 101-left-handed reflective polarization holographic grating; 1-linearly polarized beam; 2-right-handed circularly polarized beam; 3-left-handed circularly polarized beam;

[0031] Figure 5 Middle: 106-left-handed transmission polarization holographic grating; 2-right-handed circularly polarized beam; 3-left-handed circularly polarized beam;

[0032] Figure 6Middle: 103 - right-handed and left-handed reflective polarized liquid crystal lens; 104 - left-handed reflective polarized liquid crystal lens; 105 - human eye; 203 - left-handed converging light; 206 - right-handed converging light; 301 - first viewpoint; 302 - second viewpoint;

[0033] Figure 7 Middle: 100 - slab waveguide; 101 - left-handed reflective polarization holographic grating; 106 - left-handed transmissive polarization holographic grating; 103 - right-handed left-handed reflective polarization liquid crystal lens; 104 - left-handed reflective polarization liquid crystal lens; 105 - human eye; 201 - left-handed parallel light beam; 202 - left-handed totally reflected light beam; 203 - left-handed converging light beam; 205 - right-handed totally reflected light beam; 206 - right-handed converging light beam; 301 - first viewpoint; 302 - second viewpoint;

[0034] Figure 8 Middle: 100 - slab waveguide; 106 - left-handed transmissive polarization holographic grating; 107 - right-handed transmissive polarization holographic grating; 108 - right-handed transmissive polarization liquid crystal lens; 109 - left-handed transmissive polarization liquid crystal lens; 105 - human eye; 201 - left-handed parallel light beam; 202 - left-handed totally reflected light beam; 203 - left-handed converging light beam; 204 - right-handed parallel light beam; 205 - right-handed totally reflected light beam; 206 - right-handed converging light beam; 301 - first viewpoint; 302 - second viewpoint;

[0035] Figure 9 Middle: 100 - slab waveguide; 101 - left-handed reflective polarizer holographic grating; 102 - right-handed reflective polarizer holographic grating; 108 - right-handed transmissive polarizer liquid crystal lens; 109 - left-handed transmissive polarizer liquid crystal lens; 105 - human eye; 201 - left-handed parallel beam; 202 - left-handed totally reflected beam; 203 - left-handed converging light; 204 - right-handed parallel beam; 205 - right-handed totally reflected beam; 206 - right-handed converging light; 301 - first viewpoint; 302 - second viewpoint;

[0036] Figure 10 Middle: 110 - curved waveguide; 101 - left-handed reflective polarization volume holographic grating; 102 - right-handed reflective polarization volume holographic grating; 103 - right-handed and left-handed reflective polarization liquid crystal lens; 104 - left-handed reflective polarization liquid crystal lens; 105 - human eye; 201 - left-handed parallel light beam; 202 - left-handed totally reflected light beam; 203 - left-handed converging light; 204 - right-handed parallel light beam; 205 - right-handed totally reflected light beam; 206 - right-handed converging light; 301 - first type viewpoint; 302 - second type viewpoint;

[0037] Figure 11Middle: 6: first main ray; 7: second main ray; 8: third main ray; 9: fourth main ray; 10: fifth main ray; 105-human eye. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] The present invention provides a method for controlling viewpoint spacing in a near-eye display capable of expanding the field of view. The method achieves control of the viewpoint spacing by replicating and arranging output coupling elements of a waveguide system. A plurality of first output coupling elements are replicated and arranged side by side in close proximity on the surface of the waveguide to form an array, for multiple coupling out first-type circularly polarized light that matches and responds to the first output coupling element, thereby replicating multiple first-type viewpoints. A plurality of second output coupling elements are replicated and arranged side by side or at intervals in close proximity on top of the first output coupling element to form an array, for multiple coupling out second-type circularly polarized light that matches and responds to the second output coupling element, thereby replicating multiple second-type viewpoints. The first-type viewpoints formed by the array of first output coupling elements and the second-type viewpoints formed by the array of second output coupling elements are arranged in a manner that conforms to the interpupillary distance of the human eye, and the spacing is between 2 mm and 8 mm, or can be larger. Therefore, the diameters of the first and second output coupling elements can reach twice the spatial spacing between the viewpoints, effectively expanding the field of view. At the same time, the spatial spacing between the viewpoints conforms to the interpupillary distance of the human eye.

[0042] The first output coupling element and the second output coupling element include but are not limited to an off-axis reflective or transmissive chiral lens manufactured using chiral liquid crystal (CLC) polarization holography, or an off-axis reflective or transmissive metasurface or other focusing diffraction element with polarization characteristics. The first output coupling element converges a first type of circularly polarized light image with the same chirality as the first output coupling element at the human eye to form a first type of viewpoint, and the second output coupling element converges a second type of circularly polarized light image with the same chirality as the second output coupling element at the human eye to form a second type of viewpoint. The F#, i.e., the f-value, of the first output coupling element and the second output coupling element are the same to ensure that the field of view angles of the first type of viewpoint and the second type of viewpoint are the same.

[0043] The difference between the first type of viewpoint and the second type of viewpoint is that the first type of viewpoint is formed by the first type of circularly polarized convergent light, and the second type of viewpoint is formed by another type of circularly polarized convergent light, namely the second type; the viewpoints are arranged in a cross-arrangement of the first type of viewpoint and the second type of viewpoint diffracted by the first output coupling element array and the second output coupling element array respectively, the viewpoint spacing formed by the first output coupling element array can be twice the diameter of the human eye pupil, and the viewpoint spacing formed by the second output coupling element array can be twice the diameter of the human eye pupil, then the spacing of the cross-arranged viewpoints conforms to the distance of the human eye pupil diameter, and the spacing between the centers of the first output coupling element and the second output coupling element also conforms to the distance of the human eye pupil diameter.

[0044] The field of view angle is no longer limited by the outcoupled light propagation angle, but is limited by the output coupling element, and the field of view angle FOV is only determined by the F# of the output coupling element, or by the entrance pupil diameter D and the focal length f, satisfying the formula As a result, the field of view can exceed the upper limit of traditional waveguides.

[0045] The waveguide system includes an input coupling region, a waveguide, and an output coupling region. The input coupling region includes at least a first input coupling element and a second input coupling element with polarization characteristics, or is composed of an array of the first and second input coupling elements. The first input coupling element is used to couple an imaging beam of a first type of circularly polarized light into the waveguide at a first diffraction angle to form total reflected light. The second input coupling element is used to couple an imaging beam of a second type of circularly polarized light into the waveguide at a second diffraction angle to form total reflected light. The waveguide surface is provided with an input coupling region and an output coupling region, which are used to propagate the total reflected light diffracted from the input coupling region to the output coupling region. The output coupling region includes at least a first output coupling element and an array thereof, and a second output coupling element and an array thereof, both with polarization characteristics. The array of first output coupling elements matches the first input coupling element and responds to the same first type of circularly polarized light, and is used to converge the first type of circularly polarized light to form a first type of viewpoint and redirect it into the human eye. The second output coupling element matches the second input coupling element and responds to the same second type of circularly polarized light, and is used to converge the second type of circularly polarized light to form a second type of viewpoint and redirect it into the human eye.

[0046] The first and second input coupling elements are reflective or transmissive polarization volume holographic gratings, which diffract left-handed circularly polarized light images and right-handed circularly polarized light images at first and second diffraction angles, respectively. The first and second diffraction angles must be identical to ensure the same viewpoint spacing. The first and second input coupling elements may be located on the same side or on opposite sides of the waveguide surface. If located on the same side, the first and second input coupling elements are arranged side by side, closely adjacent to each other, or spaced apart. If located on opposite sides, the first and second input coupling elements overlap in the waveguide thickness direction.

[0047] The waveguide may be a single-layer planar waveguide or a single-layer curved waveguide. If it is a curved waveguide, the curvature of the outer side surface and the curvature of the inner side surface of the curved waveguide may be different.

[0048] In this embodiment, the waveguide system can be a retinal projection display system. The circularly polarized light image beam is coupled into the waveguide at a specific diffraction angle and a specific position through the input coupling region for total reflection. Finally, in the output coupling region, the first and second types of circularly polarized light image beams are converged into a viewpoint at the human eye through the first output coupling element and the second output coupling element, and are directly projected onto the human eye retina for imaging without being affected by the human eye's focusing.

[0049] The positions and sizes of the first input coupling element, the second input coupling element, the first output coupling element, and the second output coupling element are strictly arranged on the surface of the waveguide according to the designed viewpoint spacing and field of view angle. Assuming the waveguide thickness is d, the center spacing between the first output coupling elements is D1, and the center spacing between the second output coupling elements is D2, then the formula is: The first diffraction angle θ1 and the second diffraction angle θ2 can be calculated, and then the positions of the first input coupling element and the second input coupling element can be deduced based on the first diffraction angle θ1, the second diffraction angle θ2 and the total internal reflection of the waveguide. The size of the first input coupling element does not exceed 2D1, and the size of the second input coupling element does not exceed 2D2. The grating tilt angle and grating period inside the grating are derived from the required designed diffraction angle and operating wavelength.

[0050] Example 1

[0051] Figure 1 A waveguide system illustrating a method for controlling viewpoint spacing in near-eye displays capable of expanding the field of view includes: a slab waveguide 100, a left-handed reflective polarizer holographic grating 101, a right-handed reflective polarizer holographic grating 102, a left-handed reflective polarizer liquid crystal lens 104 and its array, and a right-handed reflective polarizer liquid crystal lens 103 and its array. Specifically, the left-handed reflective polarizer holographic grating 101 and the right-handed reflective polarizer holographic grating 102 are positioned in close contact with the upper surface of the same side of the waveguide surface, and are arranged side by side or spaced apart. The left-handed reflective polarizer liquid crystal lens 104 and its array are positioned in close contact with the upper surface of the other side of the waveguide surface, and the right-handed reflective polarizer liquid crystal lens 103 and its array are positioned in close contact with the upper surface of the left-handed reflective polarizer liquid crystal lens 104 and its array.

[0052] Specifically, the left-handed parallel beam 201 and the right-handed parallel beam 204 provide two identical collimated images of left-handed circularly polarized light and right-handed circularly polarized light, respectively. A display such as a DLP, LCoS, or LCD, or a laser scanning system can be used to generate the images. The collimation system forms the left-handed parallel beam 201 and the right-handed parallel beam 204 into wide beams of a single wavelength and varying angles. These beams then propagate forward through the waveguide into the input coupling region. The first and second input coupling elements, namely, the left-handed reflective polarization holographic grating 101 and the right-handed reflective polarization holographic grating 102, are positioned to correspond to the left-handed parallel beam 201 and the right-handed parallel beam 204, respectively. The left-handed reflective polarization holographic grating 101 and the right-handed reflective polarization holographic grating 102 diffract the left-handed parallel light beam 201 and the right-handed parallel light beam 204 into the interior of the slab waveguide 100 at a first diffraction angle θ1 and a second diffraction angle θ2 to form a left-handed totally reflected light beam 202 and a right-handed totally reflected light beam 205. The light beams satisfy the total reflection condition and continue to propagate forward along the output coupling region to the first output coupling element and the second output coupling element, namely the left-handed reflective polarization liquid crystal lens 104 and the right-handed reflective polarization liquid crystal lens 103. The left-handed totally reflected light beam 202 and the right-handed totally reflected light beam 205 are diffracted into left-handed convergent light 203 and right-handed convergent light 206 in the left-handed reflective polarization liquid crystal lens 104 and the right-handed reflective polarization liquid crystal lens 103, respectively, to form a first type of viewpoint 301 and a second type of viewpoint 302. The human eye 105 observes images at the first type of viewpoint 301 and the second type of viewpoint 302. The left-handed totally reflected light beam 202 and the right-handed totally reflected light beam 205 will be partially diffracted when reaching the left-handed reflective polarization liquid crystal lens 104 and the right-handed reflective polarization liquid crystal lens 103. The left-handed totally reflected light beam 202 and the right-handed totally reflected light beam 205 that have not been partially diffracted will continue to propagate in the slab waveguide 100 and reach the next left-handed reflective polarization liquid crystal lens 104 and the right-handed reflective polarization liquid crystal lens 103 and then be partially diffracted to achieve exit pupil expansion. When the diffraction efficiency of each left-handed reflective polarization liquid crystal lens 104 and the right-handed reflective polarization liquid crystal lens 103 is well designed, the uniformity of the exit pupil can be improved.

[0053] like Figure 1 As shown, the optical path distribution of different circularly polarized light images needs to correspond one to one according to the position distribution of the input coupling elements, namely the left-handed reflective polarization holographic grating 101 and the right-handed reflective polarization holographic grating 102, and the first output coupling element and the second output coupling element, namely the left-handed reflective polarization liquid crystal lens 104 and the right-handed reflective polarization liquid crystal lens 103. Figure 2 、 3As shown, for the left-handed circularly polarized light path, the left-handed reflective polarizer holographic grating 101 and the left-handed reflective polarizer liquid crystal lens 104 match and respond to the left-handed parallel light beam 201. The left-handed reflective polarizer holographic grating 101 couples the left-handed parallel light beam 201 into the slab waveguide 100 at a first diffraction angle θ1 to form left-handed total reflection light 202. When the left-handed total reflection light 201 passes through the first left-handed reflective polarizer liquid crystal lens 104, it is partially coupled out of the slab waveguide 100 and diffracted into left-handed converging light 203 to form a first type of viewpoint 301. The field of view of this viewpoint is determined by the f-value (F#) of the first output coupling element, i.e., the left-handed reflective polarizer liquid crystal lens 104. For the right-handed circularly polarized light path, the right-handed reflective polarization holographic grating 102 and the right-handed reflective polarization liquid crystal lens 103 match and respond to the right-handed parallel light beam 204. The right-handed reflective polarization holographic grating 102 couples the right-handed parallel light beam 204 into the slab waveguide 100 at a second diffraction angle θ2 to form right-handed total reflection light 205. When the right-handed total reflection light 205 passes through the first right-handed reflective polarization liquid crystal lens 103, it is partially coupled out of the slab waveguide 100 and diffracted into right-handed converging light 206, forming a second type of viewpoint 302. The field of view of this viewpoint is determined by the f-value (F#) of the second output coupling element, namely the right-handed reflective polarization liquid crystal lens 103.

[0054] The input coupling element takes the left-handed polarization volume holographic grating as an example. Figure 4 The specific working mode of the reflective polarizer holographic grating provided in this embodiment is shown. The linearly polarized light beam 1 passes through the left-handed reflective polarizer holographic grating 101, causing the left-handed circularly polarized light beam 3 to undergo Bragg diffraction, while the right-handed circularly polarized light beam 2 passes directly. Figure 5 The specific working mode of the transmission polarizer holographic grating provided in this embodiment is shown. The right-handed circularly polarized light beam 2 is directly transmitted through the left-handed transmission polarizer holographic grating 106, and the left-handed circularly polarized light beam undergoes Bragg diffraction after passing through the left-handed transmission polarizer holographic grating 106 and its handedness is changed to the right-handed circularly polarized light beam 2.

[0055] The method for controlling the viewpoint distance of near-eye display for expanding the field of view in this embodiment is as follows: Figure 6As shown, the viewpoint spacing is primarily controlled by replicating and arranging the output coupling elements of the waveguide system. Multiple copies of the left-handed reflective polarization liquid crystal lens 104 are arranged side by side in close proximity to form an array. This can be used to multiplex out first-type circularly polarized light that matches the left-handed reflective polarization liquid crystal lens 104, diffracting it into left-handed converging light 203, thereby forming multiple first-type viewpoints 301. Multiple copies of the right-handed reflective polarization liquid crystal lens 103 are placed in close proximity or at intervals above the left-handed reflective polarization liquid crystal lens 104 array to form an array. This can be used to multiplex out second-type circularly polarized light that matches the right-handed reflective polarization liquid crystal lens 103, diffracting it into right-handed converging light 206, thereby replicating multiple second-type viewpoints 302. The spacing D3 between adjacent first-type viewpoints 301 is equal to the center-to-center spacing D1 between adjacent left-handed reflective polarization liquid crystal lenses 104. The spacing D4 between adjacent second-type viewpoints 302 is equal to the center-to-center spacing D2 between adjacent right-handed reflective polarization liquid crystal lenses 103. The first viewpoint 301 and the second viewpoint 302 are arranged in a manner consistent with the distance between the pupils of the human eye, and the distance between them is between 2 mm and 8 mm, or even larger. Therefore, the center distance D1 between adjacent left-handed reflective polarization liquid crystal lenses 104 and the center distance D2 between adjacent right-handed reflective polarization liquid crystal lenses 103 can be more than twice the distance between the pupils of the human eye. Since the field of view of the present invention is directly determined by the coupler lens and the f-value (F#) of the right-handed reflective polarization liquid crystal lens 103 and the left-handed reflective polarization liquid crystal lens 104 is the same, the field of view of the first viewpoint and the second viewpoint is guaranteed to be the same, satisfying the formula: A large field of view can be obtained while the spatial distance between viewpoints can be reduced to the size of the human pupil.

[0056] Example 2

[0057] like Figure 7-9 As shown, this embodiment includes several planar waveguide systems in addition to embodiment 1. The rest of the configuration in this embodiment is the same as that in embodiment 1, except for the input coupling element in the input coupling region and the output coupling element in the output coupling region.

[0058] like Figure 7 As shown, the difference between this waveguide system and Example 1 is that the input coupling elements of the input coupling region are a left-handed reflective polarizer holographic grating 101 and a left-handed transmissive polarizer holographic grating 106, which are respectively attached to the upper and lower surfaces of the waveguide surface. In order to form the first type of viewpoint 301 and the second type of viewpoint 302, the first type of circularly polarized light and the second type of circularly polarized light need to be formed after passing through the waveguide system.

[0059] Depend on Figure 4 、 5The working mode of the polarization holographic grating can be understood as follows: the left-handed parallel light beam 201 propagates forward to the input coupling region, first passing through the left-handed transmissive polarization holographic grating 106, where it diffracts 50% into a right-handed total reflection light beam 205. The remaining 50% of the left-handed parallel light beam 201 undergoes zero-order transmission through the waveguide and reaches the left-handed reflective polarization holographic grating 101, where it is diffracted into a left-handed total reflection light beam 202. The diffraction efficiency of the left-handed parallel light beam 201 can be adjusted by controlling the thickness of the left-handed reflective polarization holographic grating 101 and the left-handed transmissive polarization holographic grating 106. The waveguide system also forms two circularly polarized light paths to implement the present invention's method for controlling viewpoint spacing in near-eye displays with an expanded field of view.

[0060] like Figure 8 As shown, this waveguide system differs from Example 1 in that the input coupling elements in the input coupling region are a left-handed transmissive polarization holographic grating 106 and a right-handed transmissive polarization holographic grating 107, and the output coupling elements in the output coupling region are a right-handed transmissive polarization liquid crystal lens 108 and a left-handed transmissive polarization liquid crystal lens 109. The left-handed transmissive polarization holographic grating 106 and the right-handed transmissive polarization liquid crystal grating 107 are attached to the lower surface of the waveguide and are closely aligned with each other, corresponding to the left-handed parallel light beam 201 and the right-handed parallel light beam 204, respectively. The right-handed transmissive polarization liquid crystal lens 108 and its array are attached to the lower surface of the waveguide, while the left-handed transmissive polarization liquid crystal lens 109 and its array are closely aligned with the lower surface of the right-handed transmissive polarization liquid crystal lens 108 and its array, overlapping in the waveguide thickness direction. This waveguide system also forms two circularly polarized light paths to implement the present invention's method for controlling viewpoint spacing for near-eye display with expanded field of view.

[0061] like Figure 9 As shown, this waveguide system differs from Example 1 in that the output coupling elements in the output coupling region are a right-handed transmissive polarized liquid crystal lens 108 and a left-handed transmissive polarized liquid crystal lens 109. The left-handed transmissive polarized liquid crystal lens 109 and its array are attached to the lower surface of the waveguide, while the right-handed transmissive polarized liquid crystal lens 108 and its array are closely attached to the lower surface of the left-handed transmissive polarized liquid crystal lens 109 and its array, overlapping in the waveguide thickness direction. This waveguide system also forms two circularly polarized light paths to implement the present invention's method for controlling viewpoint spacing for near-eye display with an expanded field of view.

[0062] Example 3

[0063] like Figure 10As shown, the rest of the configuration in this embodiment is the same as that in embodiment 1. The difference from embodiment 1 is that the waveguide is a curved waveguide 110, and the input coupling elements in the input coupling region, namely the left-handed reflective polarizer holographic grating 101 and the right-handed reflective polarizer holographic grating 102, and the output coupling elements in the output coupling region, namely the left-handed reflective polarizer liquid crystal lens 104 and the right-handed reflective polarizer liquid crystal lens 103, all have a certain degree of flexibility. Compared with a flat waveguide, this waveguide system is more in line with the public's social standards and can achieve a larger FOV.

[0064] Optionally, the input coupling element of the input coupling region of the waveguide system of this embodiment can be Figure 7 The left-handed reflective polarization holographic grating 101 and the left-handed transmissive polarization holographic grating 106 in the embodiment may also be Figure 8 The output coupling element of the output coupling region of the waveguide system of this embodiment can also be Figure 8 The right-handed transmissive polarizing liquid crystal lens 108 and the left-handed transmissive polarizing liquid crystal lens 109 are combined according to the two required circularly polarized light paths.

[0065] The relationship between the first type of viewpoint formed by the convergence of the first type of circularly polarized light and the second type of viewpoint formed by the convergence of the second type of circularly polarized light and the eye 105 is as follows: Figure 11 As shown, the first type of viewpoint array and the second type of viewpoint array formed by the waveguide system are no longer spaced apart in a straight line, but are spaced apart by a certain arc, the arc of which is determined by the curvature of the upper and lower surfaces of the waveguide. When the eye 105 is looking forward, that is, the direction of the third principal ray 8 is the same as the direction of the eye 105, the image passing through the waveguide system is in the center of the visual field; when the eye 105 is looking in other directions, that is, the first principal ray 6, the second principal ray 7, the fourth principal ray 9, the fifth principal ray 10 or other principal rays can be in the same direction as the eye 105, the image passing through the waveguide system can still be kept in the center of the visual field. The effect of the waveguide system matching the direction of the principal ray entering the human eye with the direction of the glasses is more consistent with a good viewing experience and also forms two circularly polarized light paths to realize the near-eye display viewpoint spacing control method with expanded field of view of the present invention.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for controlling the viewpoint distance of near-eye display capable of expanding the field of view, characterized in that: The viewpoint spacing is controlled by an array of output coupling elements of the waveguide system. A plurality of identical first output coupling elements are provided and arranged closely side by side on the waveguide surface to form an array, for multiple coupling out first-type circularly polarized light that matches and responds to the first output coupling elements, thereby achieving multiple first-type viewpoints. A plurality of identical second output coupling elements are provided and arranged closely side by side or at intervals above the first output coupling elements to form an array, for multiple coupling out second-type circularly polarized light that matches and responds to the second output coupling elements, thereby achieving multiple second-type viewpoints. The first-type viewpoints formed by the array of first output coupling elements and the second-type viewpoints formed by the array of second output coupling elements are arranged at intervals consistent with the interpupillary distance of the human eye. The diameters of the first and second output coupling elements can be twice the spatial spacing of the viewpoints, thereby effectively expanding the field of view while ensuring that the spatial spacing of the viewpoints matches the interpupillary distance of the human eye. The field of view angle is no longer limited by the outcoupled light propagation angle, but is limited by the output coupling element, and the field of view angle FOV is only determined by the F# of the output coupling element, or by the entrance pupil diameter D and the focal length f, satisfying the formula As a result, the field of view can exceed the upper limit of traditional waveguides; The waveguide system includes an input coupling region, a waveguide, and an output coupling region; the input coupling region includes at least a first input coupling element and a second input coupling element with polarization characteristics, or is composed of an array of the first and second input coupling elements; the first input coupling element is used to couple an imaging beam of a first type of circularly polarized light into the waveguide at a first diffraction angle to form total reflected light; the second input coupling element is used to couple an imaging beam of a second type of circularly polarized light into the waveguide at a second diffraction angle to form total reflected light; the waveguide surface is provided with an input coupling region and an output coupling region, for propagating the total reflected light diffracted from the input coupling region to the output coupling region; the output coupling region includes at least a first output coupling element and an array thereof, and a second output coupling element and an array thereof, with polarization characteristics; the array of the first output coupling element matches the first input coupling element and responds to the same first type of circularly polarized light, and is used to converge the first type of circularly polarized light to form a first type of viewpoint and redirect it into the human eye; The second output coupling element matches the second input coupling element and responds to the same second type of circularly polarized light, and is used to converge the second type of circularly polarized light to form a second type of viewpoint and redirect it into the human eye; The positions and sizes of the first input coupling element, the second input coupling element, the first output coupling element, and the second output coupling element are strictly arranged on the surface of the waveguide according to the designed viewpoint spacing and field of view angle. Assuming the waveguide thickness is d, the center spacing between the first output coupling elements is D1, and the center spacing between the second output coupling elements is D2, then the formula is: The first diffraction angle θ1 and the second diffraction angle θ2 are calculated, and then the positions of the first input coupling element and the second input coupling element are deduced based on the first diffraction angle θ1, the second diffraction angle θ2 and the total internal reflection of the waveguide. The size of the first input coupling element does not exceed 2D1, and the size of the second input coupling element does not exceed 2D2. The grating tilt angle and grating period inside the grating are both derived from the desired designed diffraction angle and operating wavelength.

2. The method for controlling the viewpoint distance of near-eye display capable of expanding the field of view according to claim 1, characterized in that: The first output coupling element and the second output coupling element are focusing diffraction elements with polarization characteristics manufactured using chiral liquid crystal polarization holography. The first output coupling element converges a first type of circularly polarized light image with the same chirality as the first output coupling element at the human eye to form a first type of viewpoint, and the second output coupling element converges a second type of circularly polarized light image with the same chirality as the second output coupling element at the human eye to form a second type of viewpoint. The F#, i.e., f-value, of the first output coupling element and the second output coupling element are the same to ensure that the field of view angles of the first type of viewpoint and the second type of viewpoint are the same.

3. The method for controlling the viewpoint distance of near-eye display capable of expanding the field of view according to claim 1, characterized in that: The first type of viewpoint is formed by the first type of circularly polarized convergent light, and the second type of viewpoint is formed by the second type of circularly polarized convergent light; the viewpoints are arranged in a cross-arrangement by the first and second types of viewpoints diffracted by the first and second output coupling element arrays, respectively; the spacing between the viewpoints formed by the first output coupling element array is twice the diameter of the human eye pupil, and the spacing between the viewpoints formed by the second output coupling element array is twice the diameter of the human eye pupil; then, the spacing between the cross-arranged viewpoints conforms to the distance of the human eye pupil diameter, and the spacing between the centers of the first and second output coupling elements also conforms to the distance of the human eye pupil diameter.

4. The method for controlling the viewpoint distance of near-eye display capable of expanding the field of view according to claim 1, wherein: The first input coupling element and the second input coupling element are reflective or transmissive polarization volume holographic gratings, which diffract left-handed circularly polarized light images and right-handed circularly polarized light images at first and second diffraction angles, respectively, and the first and second diffraction angles are the same to ensure the same viewpoint spacing; The first input coupling element and the second input coupling element are on the same side or on different sides of the waveguide surface. If they are on the same side, the first input coupling element and the second input coupling element are arranged side by side, close to each other or spaced apart. If on opposite sides, the positions of the first input coupling element and the second offset input coupling element overlap in the waveguide thickness direction.

5. The method for controlling the viewpoint distance of near-eye display capable of expanding the field of view according to claim 1, characterized in that: The waveguide is a single-layer planar waveguide or a single-layer curved waveguide.

6. The method for controlling the viewpoint distance of near-eye display capable of expanding the field of view according to claim 1, characterized in that: The waveguide system can be a retinal projection display system. The circularly polarized light image beam is coupled into the waveguide at a set diffraction angle and a set position through the input coupling region for total reflection. Finally, in the output coupling region, the first and second types of circularly polarized light image beams are converged into a viewpoint at the human eye through the first output coupling element and the second output coupling element, and are directly projected onto the human eye retina for imaging without being affected by the human eye's focusing.

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