Optical transmission integrated imaging 3D display device with large depth of field

Abstract

The present invention proposes an optical transmission integrated imaging 3D display device with a large depth of field, which includes a projector I, a projector II and a double-focal length holographic optical element. The double-focal length holographic optical element is prepared by two holographic exposures, and the two holographic exposures respectively record focal lengths of f 1 and f 2 In the integrated imaging 3D display process with a large depth of field, the dual-focal-length holographic optical element reproduces a focal length of f under the illumination of searchlight I projected by projector I and searchlight II projected by projector II. 1 and f 2 A spherical wave array is used to simultaneously generate a central depth plane I and a central depth plane II, and the information of the micro-image array I and the micro-image array II are modulated respectively. At the same time, a 3D image I is reconstructed near the central depth plane I and a 3D image II is reconstructed near the central depth plane II, thereby increasing the depth of field.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated imaging 3D display, and in particular relates to an optical transmission type integrated imaging 3D display device with a large depth of field. Background Art

[0002] Integrated imaging 3D display technology is a true 3D display technology. Based on the principle of light reversibility, it uses a lens array to densely sample the light field information of a 3D scene, and then optically reconstructs the sampled light field information to restore a 3D image in space that is consistent with the depth and color of the original 3D scene. Therefore, integrated imaging 3D display technology can provide viewers with full-color, quasi-continuous parallax, and stereoscopic viewing 3D images without the need for coherent light sources and auxiliary viewing equipment.

[0003] A holographic optical element is an optical element prepared using the principle of holographic imaging, and is essentially a volume holographic grating. Compared to optical coupling devices such as semi-transparent and semi-reflective mirrors, free-form prisms, and optical waveguides, holographic optical elements can not only replace one or more components in the optical system, reduce the volume of the system, reduce the redundancy of the system, and be easy to integrate, depending on the difference in the wavefront of the recorded signal wave, but also have the dual functions of imaging and optical perspective, and are therefore widely used in optical transmission-type augmented reality 3D displays. However, the wavefront of the lens array recorded by traditional holographic optical elements has only one focal length, corresponding to a central depth plane, which greatly limits the depth of field of the reconstructed 3D image. Summary of the invention

[0004] The present invention provides an optical transmission integrated imaging 3D display device with a large depth of field, the device comprising a projector I, a projector II and a dual-focal length holographic optical element, as shown in the attached Figure 1 As shown. The dual-focal length holographic optical element is prepared by two holographic exposures and has the function of a lens array with two focal lengths. The projector I projects a searchlight I containing a micro-image array I onto the dual-focal length holographic optical element. The searchlight I satisfies the Bragg condition I. The dual-focal length holographic optical element presents a focal length of f 1 The function of the lens array is realized, and the information of the micro-image array I in the searchlight I is modulated to reconstruct a 3D image I near the central depth plane I. The projector II projects the searchlight II containing the micro-image array II onto the dual-focal length holographic optical element. The searchlight II satisfies the Bragg condition II. The dual-focal length holographic optical element presents a focal length of f 2The function of the lens array is realized, and the information of the micro-image array II in the searchlight II is modulated to reconstruct a 3D image II near the central depth plane II. When the projector I and the projector II respectively project the searchlight I and the searchlight II onto the dual-focal length holographic optical element at the same time, two different 3D images are reconstructed near the two central depth planes. Ambient light that does not meet the Bragg conditions I and II will directly pass through the dual-focal length holographic optical element, realizing an optical transmission-type integrated imaging 3D display with a large depth of field.

[0005] The dual-focal-length holographic optical element is a reflective volume holographic grating, which is prepared through two holographic exposure processes.

[0006] The first holographic exposure device of the dual-focal-length holographic optical element is as shown in the attached Figure 2 As shown, it includes a mask plate, a lens array I, a lens array II and a holographic material, and the optical interval between the lens array I and the lens array II is g 1 The structure of the mask is as shown in the attached Figure 3 As shown, the light-transmitting units and the light-blocking units are arranged in a matrix, the width of the light-transmitting units is w, the center spacing between adjacent light-transmitting units is equal to the pitch p of the lens array, and the width of the transmitted light beam is controlled by changing the size of the light-transmitting units.

[0007] The second holographic exposure device of the dual-focal-length holographic optical element is as shown in the attached Figure 4 As shown, it includes lens array I, lens array II and holographic material, and the optical interval between lens array I and lens array II is g 2 .

[0008] In the double holographic exposure device, the focal length of lens array I is f a , the focal length of lens array II is f b The pitch of lens array I and lens array II is the same, both are p, the thickness is d, the refractive index is n, the holographic material is coated on a transparent glass substrate, the holographic material is closely attached to lens array II, and the mask plate is closely attached to lens array I.

[0009] The first exposure process of the dual-focal length holographic optical element is as shown in the attached Figure 5 As shown. Signal wave I is a beam of parallel light. Figure 4 The reference wave I is a divergent spherical wave with the same wavelength and polarization state as the signal wave I. The signal wave I and the reference wave I are located on both sides of the holographic material. The reference wave I is incident at an angle θ r1The first holographic exposure records the focal length of the double-focal length holographic optical element. 1 The optical modulation function of the lens array group, whose focal length is f 1 It can be expressed as,

[0010]

[0011] The width of the light-transmitting unit of the mask is w,

[0012]

[0013] The second exposure process of the dual-focal length holographic optical element is as shown in the attached Figure 6 As shown. Signal wave II is a beam of parallel light, which is incident vertically on the holographic material after passing through lens array I and lens array II. Reference wave II is a divergent spherical wave with the same wavelength and polarization state as signal wave II. Signal wave II and reference wave II are located on both sides of the holographic material. Reference wave II is incident at an angle θ r2 The second holographic exposure of the dual-focal length holographic optical element is completed. The second holographic exposure records the focal length f. 2 The optical modulation function of the lens array group, whose focal length is f 2 It can be expressed as,

[0014]

[0015] Preferably, there needs to be a certain angle difference between the incident angles of the reference wave I of the first exposure and the reference wave II of the second exposure, and the difference between the incident angles of the reference wave I and the reference wave II needs to be greater than the half-angle bandwidth Δθ of the dual-focal length holographic optical element to avoid crosstalk between the two groups of reproduced lights that satisfy the Bragg conditions I and II.

[0016] The optical transmission integrated imaging 3D display process with large depth of field is as follows. Figure 7 Schematic diagram of reconstruction of 3D image I. The searchlight I projected by the projector I contains information of the micro-image array I, and the wavelength and incident angle of the searchlight I are the same as those of the reference wave I, satisfying the Bragg condition I of the dual-focal length holographic optical element. At this time, the reconstructed light of the dual-focal length holographic optical element is a focal length of f 1 spherical wave array, at f 1 The central depth plane I is generated at the position of the focal length f 1 The optical modulation function of the lens array group modulates the information of the micro-image array I in the searchlight I and reconstructs a 3D image I near the central depth plane I. Figure 8 Schematic diagram of reconstruction of 3D image II. The searchlight II projected by the projector II contains the information of the micro-image array II, and the wavelength and incident angle of the searchlight II are the same as those of the reference wave II, satisfying the Bragg condition II of the dual-focal length holographic optical element. At this time, the reconstructed light of the dual-focal length holographic optical element is a focal length of f 2 spherical wave array, at f 2 The central depth plane II is generated at the focal length f 2 The optical modulation function of the lens array group is used to modulate the information of the micro-image array II in the searchlight II, and reconstruct the 3D image II near the central depth plane II. When the projector I and the projector II respectively project the searchlight I that satisfies the Bragg condition I and the searchlight II that satisfies the Bragg condition II onto the dual-focal length holographic optical element, the dual-focal length holographic optical element will simultaneously reproduce the spherical wave arrays of two focal lengths, and simultaneously generate the central depth plane I and the central depth plane II, and respectively modulate the information of the micro-image array I and the micro-image array II, and simultaneously reconstruct the 3D image I near the central depth plane I and the 3D image II near the central depth plane II, thereby increasing the depth of field.

[0017] The external ambient light does not satisfy Bragg conditions I and II, so the ambient light will directly pass through the dual-focal length holographic optical element to achieve optical transmission display.

[0018] The optical transmission integrated imaging 3D display device with a large depth of field can simultaneously realize the functions of lens arrays with two focal lengths, modulate the searchlight I projected by projector I and the searchlight II projected by projector II respectively, and simultaneously reconstruct different 3D images near the central depth plane I and the central depth plane II, thereby effectively improving the depth of field of the optical transmission integrated imaging 3D display system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attached Figure 1 Schematic diagram of the optical transmission integrated imaging 3D display structure with large depth of field.

[0020] Attached Figure 2 Schematic diagram of the first holographic exposure device of the dual-focal length holographic optical element.

[0021] Attached Figure 3 Schematic diagram of the mask plate.

[0022] Attached Figure 4 Schematic diagram of the second holographic exposure device of the double-focal-length holographic optical element.

[0023] Attached Figure 5 Schematic diagram of the optical path of the first holographic exposure process of a dual-focal-length holographic optical element.

[0024] Attached Figure 6 Schematic diagram of the optical path of the second holographic exposure process of the dual-focal-length holographic optical element.

[0025] Attached Figure 7 Schematic diagram of reconstruction of 3D image I.

[0026] Attached Figure 8 Schematic diagram of reconstruction of 3D image II.

[0027] The diagrams in the above drawings are marked as follows: 1 projector I, 2 projector II, 3 searchlight I, 4 searchlight II, 5 dual-focus holographic optical element, 6 3D image 1, 7 3D image II, 8 viewer, 900 mask, 901 mask light blocking unit, 902 mask light transmitting unit, 10 lens array I, 11 lens array II, 12 holographic material, 13 signal light I, 14 reference light I, 15 signal light II, 16 reference light II, 17 reconstructed light I, 18 reconstructed light II, 19 reverse extension line of reconstructed light II. It should be understood that the above drawings are only schematic and not drawn to scale. DETAILED DESCRIPTION

[0028] A typical embodiment of the optical transmission integrated imaging 3D display device with a large depth of field of the present invention is described in detail below, and the present invention is further described in detail. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Persons skilled in the art in this field may make some non-essential improvements and adjustments to the present invention based on the above content of the present invention, which still fall within the scope of protection of the present invention.

[0029] The present invention proposes an optical transmission integrated imaging 3D display device with a large depth of field, the device comprising a projector I1, a projector II2 and a dual-focal length holographic optical element 5, as shown in the attached Figure 1 As shown. The dual-focal length holographic optical element 5 is prepared by two holographic exposures and has the function of a lens array with two focal lengths. The projector Ⅰ1 projects the searchlight Ⅰ3 containing the micro-image array Ⅰ onto the dual-focal length holographic optical element 5. The searchlight Ⅰ3 satisfies the Bragg condition Ⅰ. The dual-focal length holographic optical element 5 presents a focal length of f 1 The function of the lens array is realized, and the information of the micro-image array I in the searchlight I3 is modulated to reconstruct a 3D image I6 near the central depth plane I. The projector II2 projects the searchlight II4 containing the micro-image array II onto the dual-focal length holographic optical element 5. The searchlight II4 satisfies the Bragg condition II. The dual-focal length holographic optical element 5 presents a focal length of f 2The function of the lens array is realized, and the information of the micro-image array II in the searchlight II4 is modulated to reconstruct a 3D image II7 near the central depth plane II. When the projector I1 and the projector II2 respectively project the searchlight I3 and the searchlight II4 onto the dual-focal length holographic optical element 5 at the same time, two different 3D images are reconstructed near the two central depth planes. Ambient light that does not meet the Bragg conditions I and II will directly pass through the dual-focal length holographic optical element 5, realizing an optical transmission-type integrated imaging 3D display with a large depth of field.

[0030] The dual-focal-length holographic optical element 5 is a reflective volume holographic grating, which is prepared through two holographic exposure processes.

[0031] The first holographic exposure device of the dual-focal-length holographic optical element 5 is as shown in the attached Figure 2 As shown in FIG. 1 , the mask plate 900 includes a lens array Ⅰ10, a lens array Ⅱ11 and a holographic material 12. The optical spacing between the lens array Ⅰ10 and the lens array Ⅱ11 is 2.32 mm. The structure of the mask plate 900 is shown in FIG. Figure 3 As shown, the light-transmitting units 901 and the light-blocking units 902 are arranged in a matrix, the width of the light-transmitting units 901 is 1.09 mm, the center spacing between adjacent light-transmitting units is equal to the pitch of the lens array 1.27 mm, and the width of the transmitted light beam can be controlled by changing the size of the light-transmitting units 901.

[0032] The second holographic exposure device of the dual-focal-length holographic optical element 5 is as shown in the attached Figure 4 As shown, it includes lens array I10, lens array II11 and holographic material 12, and the optical interval between lens array I10 and lens array II11 is 1.74 mm.

[0033] In the double holographic exposure device, the focal length of lens array I10 is 2 mm, the focal length of lens array II11 is 2 mm, the pitch of lens array I and lens array II is the same, which is 1.27 mm, the thickness is 3 mm, and the refractive index is 1.49. The holographic material 12 is coated on a transparent glass substrate and fits tightly with lens array II11, and the mask plate 900 fits tightly with lens array I10.

[0034] The first exposure process of the dual-focal-length holographic optical element 5 is shown in the attached figure. Figure 5 As shown. The signal wave I13 is a beam of parallel light. Figure 4The reference wave I14 is a divergent spherical wave having the same wavelength and polarization state as the signal wave I13. The signal wave I13 and the reference wave I14 are located on both sides of the holographic material. The reference wave I14 is incident on the holographic material 12 at an incident angle of 45° and interferes with the signal wave I13, recording interference fringes on the holographic material 12, completing the first holographic exposure of the dual-focal length holographic optical element 5. The first recording is the focal length f 1 The optical modulation function of the lens array group, whose focal length f 1 It can be expressed as,

[0035]

[0036] The width of the light-transmitting unit of the mask is,

[0037]

[0038] The second exposure process of the dual-focal-length holographic optical element 5 is shown in FIG. Figure 6 As shown. The signal wave II15 is a beam of parallel light, which is incident vertically on the holographic material 12 after passing through the lens array I10 and the lens array II11. The reference wave II16 is a divergent spherical wave, which has the same wavelength and polarization state as the signal wave II15. The signal wave II15 and the reference wave II16 are located on both sides of the holographic material 12. The reference wave II16 is incident on the holographic material 12 at an incident angle of -45°, and interferes with the signal wave II15, recording interference fringes on the holographic material 12, completing the second holographic exposure of the dual-focal length holographic optical element 5. The second recording is the focal length of f 2 The optical modulation function of the lens array group, whose focal length is f 2 It can be expressed as,

[0039]

[0040] Preferably, there needs to be a certain angle difference between the incident angles of reference wave I of the first exposure and reference wave II of the second exposure, and the difference between the incident angles of reference wave I and reference wave II needs to be greater than 10°, the half-angle bandwidth of the dual-focal length holographic optical element, to avoid crosstalk between the two groups of reproduced lights satisfying Bragg conditions I and Bragg conditions II.

[0041] The large depth of field optical transmission integrated imaging 3D display process is as follows. Figure 7Schematic diagram of reconstruction of 3D image Ⅰ6. The searchlight Ⅰ3 projected by projector Ⅰ1 contains the information of micro-image array Ⅰ, and the wavelength and incident angle of the searchlight Ⅰ3 are the same as those of reference wave Ⅰ14, with a wavelength of 532nm and an incident angle of 45°, satisfying the Bragg condition Ⅰ of the dual-focal length holographic optical element 5. At this time, the reproduced light Ⅰ17 of the dual-focal length holographic optical element 5 is a spherical wave array with a focal length of 14.0mm, and a central depth plane Ⅰ is generated at 14.0mm, thereby realizing the optical modulation function of the lens array group with a focal length of 14.0mm, modulating the information of micro-image array Ⅰ in the searchlight Ⅰ3, and reconstructing a 3D image Ⅰ6 near the central depth plane Ⅰ. Similarly, the attached Figure 8 The figure is a schematic diagram of the reconstruction of the 3D image Ⅱ7. The searchlight Ⅱ4 projected by the projector Ⅱ2 contains the information of the micro-image array Ⅱ, and the wavelength and the incident angle of the searchlight Ⅱ4 are the same as the wavelength and the incident angle of the reference wave Ⅱ16, with a wavelength of 532nm and an incident angle of -45°, which meets the Bragg condition Ⅱ of the dual-focal length holographic optical element 5. At this time, the reproduced light Ⅱ18 of the dual-focal length holographic optical element 5 is a spherical wave array with a focal length of -14.2mm, and a central depth plane Ⅱ is generated at -14.2mm, thereby realizing the optical modulation function of the lens array group with a focal length of -14.2mm, modulating the information of the micro-image array Ⅱ in the searchlight Ⅱ4, and reconstructing the 3D image Ⅱ7 near the central depth plane Ⅱ. As shown in the attached figure Figure 1 As shown, when the projector Ⅰ1 and the projector Ⅱ2 respectively project the searchlight Ⅰ3 satisfying the Bragg condition Ⅰ and the searchlight Ⅱ4 satisfying the Bragg condition Ⅱ onto the dual-focal length holographic optical element 5, the dual-focal length holographic optical element 5 will simultaneously reproduce the spherical wave arrays of two focal lengths, and simultaneously generate the central depth plane Ⅰ and the central depth plane Ⅱ, and respectively modulate the information of the micro-image array Ⅰ and the micro-image array Ⅱ, and simultaneously reconstruct the 3D image Ⅰ6 near the central depth plane Ⅰ and the 3D image Ⅱ7 near the central depth plane Ⅱ, so as to increase the depth of field.

[0042] The external ambient light does not satisfy Bragg conditions I and II, so the ambient light will directly pass through the dual-focal length holographic optical element to achieve optical transmission display.

[0043] The optical transmission integrated imaging 3D display device with a large depth of field can simultaneously realize the functions of lens arrays with two focal lengths, modulate the searchlight I projected by projector I and the searchlight II projected by projector II respectively, and simultaneously reconstruct different 3D images near the central depth plane I and the central depth plane II, thereby effectively improving the depth of field of the optical transmission integrated imaging 3D display system.

Claims

1. An optical transmission integrated imaging 3D display device with a large depth of field, characterized in that: The device comprises a projector I, a projector II and a double-focal-length holographic optical element; the double-focal-length holographic optical element is a reflective volume holographic grating, has the function of a lens array of two focal lengths, and is prepared through two holographic exposure processes: the first holographic exposure device of the double-focal-length holographic optical element comprises a mask plate, a lens array I, a lens array II and a holographic material, the optical interval between the lens array I and the lens array II is g1, the mask plate is arranged in a matrix by light-transmitting units and light-blocking units, the width of the light-transmitting units is w, the center distance between adjacent light-transmitting units is equal to the pitch p of the lens array, and the width of the transmitted light beam is controlled by changing the size of the light-transmitting units; the second holographic exposure device of the double-focal-length holographic optical element comprises a lens array I, a lens array II and a holographic material, the optical interval between the lens array I and the lens array II is g2; in the two holographic exposure devices, the focal length of the lens array I is f a , the focal length of lens array II is f b , the pitch of lens array I and lens array II are the same, both are p, the thickness is d, the refractive index is n, the holographic material is coated on the transparent glass substrate, the holographic material is closely attached to lens array II, and the mask plate is closely attached to lens array I; The projector I projects searchlight I containing micro-image array I onto the dual-focal-length holographic optical element, the searchlight I satisfies Bragg condition I, the dual-focal-length holographic optical element exhibits the function of a lens array with a focal length of f1, and modulates the information of micro-image array I in the searchlight I, and reconstructs a 3D image I near the central depth plane I; The projector II projects searchlight II containing micro-image array II onto the dual-focal length holographic optical element, the searchlight II meets Bragg condition II, the dual-focal length holographic optical element exhibits the function of a lens array with a focal length of f2, and modulates the information of micro-image array II in the searchlight II, and reconstructs a 3D image II near the central depth plane II; when the projectors I and II respectively project the searchlight I and searchlight II onto the dual-focal length holographic optical element at the same time, two different 3D images are reconstructed near two central depth planes; the incident angles of the reference wave I of the first holographic exposure and the reference wave II of the second holographic exposure need to have a certain angle difference, and the difference in the incident angles of the reference wave I and the reference wave II needs to be greater than the half-angle bandwidth Δθ of the dual-focal length holographic optical element to avoid crosstalk between the two groups of reproduced lights that meet Bragg conditions I and Bragg conditions II, and the ambient light that does not meet Bragg conditions I and Bragg conditions II will directly pass through the dual-focal length holographic optical element, thereby realizing an optical transmission-type integrated imaging 3D display with a large depth of field.

2. The optical transmission integrated imaging 3D display device with large depth of field according to claim 1, characterized in that: In the first holographic exposure process of the dual-focal length holographic optical element, the signal wave I is a beam of parallel light, which passes through the light transmission unit of the mask plate, passes through the lens array I and the lens array II, and is vertically incident on the holographic material. The reference wave I is a divergent spherical wave, which has the same wavelength and polarization state as the signal wave I. The signal wave I and the reference wave I are respectively located on both sides of the holographic material, and the reference wave I is incident at an angle θ. r1 The first holographic exposure of the dual-focal length holographic optical element is completed. The first holographic exposure records the optical modulation function of the lens array group with a focal length of f1. The focal length f1 can be expressed as The width of the light-transmitting unit of the mask is In the second holographic exposure process of the dual-focal length holographic optical element, the signal wave II is a beam of parallel light, which is vertically incident on the holographic material after passing through the lens array I and the lens array II. The reference wave II is a beam of divergent spherical waves, which has the same wavelength and polarization state as the signal wave II. The signal wave II and the reference wave II are located on both sides of the holographic material respectively. The reference wave II is incident at an angle θ r2 It is incident on the holographic material and interferes with the signal wave II, recording interference fringes on the holographic material, completing the second holographic exposure of the dual-focal-length holographic optical element. The second holographic exposure records the optical modulation function of the lens array group with a focal length of f2, and its focal length f2 can be expressed as 3. The optical transmission integrated imaging 3D display device with large depth of field according to claim 1, characterized in that: In the optical transmission integrated imaging 3D display process with a large depth of field, the searchlight I projected by the projector I contains information of the micro-image array I, and the wavelength and the incident angle of the searchlight I are the same as the wavelength and the incident angle of the reference wave I, satisfying the Bragg condition I of the dual-focal length holographic optical element. At this time, the reproduced light of the dual-focal length holographic optical element is a spherical wave array with a focal length of f1, and a central depth plane I is generated at f1, thereby realizing the optical modulation function of the lens array group with a focal length of f1, modulating the information of the micro-image array I in the searchlight I, and reproducing the 3D image I near the central depth plane I; The searchlight II projected by the projector II contains information of the micro-image array II, and the wavelength and the incident angle of the searchlight II are the same as the wavelength and the incident angle of the reference wave II, satisfying the Bragg condition II of the dual-focal length holographic optical element. At this time, the reproduced light of the dual-focal length holographic optical element is a spherical wave array with a focal length of f2, and a central depth plane II is generated at f2, thereby realizing the optical modulation function of the lens array group with a focal length of f2, modulating the information of the micro-image array II in the searchlight II, and reproducing a 3D image II near the central depth plane II; When the projector I and the projector II respectively project the searchlight I satisfying the Bragg condition I and the searchlight II satisfying the Bragg condition II onto the dual-focal length holographic optical element at the same time, the dual-focal length holographic optical element will simultaneously reproduce spherical wave arrays of two focal lengths, and simultaneously generate the central depth plane I and the central depth plane II, and respectively modulate the information of the micro-image array I and the micro-image array II, and simultaneously reproduce the 3D image I near the central depth plane I and reproduce the 3D image II near the central depth plane II, thereby increasing the depth of field.

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