Large-viewing-angle holographic Maxwell display method based on spherical crown diffraction

Abstract

The invention provides a large-view-angle holographic Maxwell display method based on spherical crown diffraction in order to solve the problem that the immersion sense is insufficient due to the fact that a traditional Maxwell display view angle is limited. According to the method, holographic Maxwell display and spherical crown diffraction are combined, a spherical crown diffraction relation among an object spherical crown surface, a holographic spherical crown surface and a pupil spherical crown surface is established, the depth of field and the image quality are controlled in a filtering mode, and therefore large-view-angle holographic Maxwell display with flexible control parameters is achieved. The method can theoretically cover a complete visual angle range required by human eyes, does not need a complex light path, can flexibly control performance parameters such as depth of field and image quality, and has a great application prospect.

Description

Technical Field

[0001] The present invention relates to the field of holographic display, and in particular to a method for generating and reproducing a hologram. Background Art

[0002] As an effective solution to the convergence-adaptation conflict of near-eye displays, Maxwell displays have demonstrated their unique advantages in many aspects, such as being able to provide clear images within a certain depth of field without being affected by the focus of the eye. In recent years, the emergence of holographic Maxwell displays has solved the shortcomings of traditional Maxwell displays and met the requirements of flexible control parameters, aberration-free design, and extended eye boxes. Nevertheless, due to limitations such as the pixel size of planar spatial light modulators and the inability to achieve seamless stitching, holographic Maxwell displays cannot cover the viewing angle range required by the human eye, and the lack of immersion needs to be solved urgently. Curved holography is an effective way to overcome these constraints. Spherical holography can achieve omnidirectional reconstruction of the light field, theoretically providing a larger viewing angle, which is of great significance to the improvement of immersion. Summary of the invention

[0003] The technical problem to be solved by the present invention is to break through the problem of insufficient immersion caused by the limited viewing angle of traditional Maxwell display, and provide a large viewing angle holographic Maxwell display method based on spherical crown diffraction. The following technical measures are adopted to solve the above technical problems. The large viewing angle holographic Maxwell display method based on spherical crown diffraction is carried out in the following steps: A hologram calculation generation method for a large viewing angle holographic Maxwell display based on spherical crown diffraction, the specific steps are as follows: Step 1, the object light wave U located at the outer spherical crown with a radius R s , after the spherical crown diffraction process from outside to inside, we get e The diffraction field distribution U of the equivalent pupil sphere crown e ; Step 2, obtain the diffraction field U e The filtering process is to set the diffraction field larger than the required filter aperture to zero, where the size of the filter aperture will determine the depth of field and reconstruction quality of the holographic display; Step 3, the filtered diffraction field, after the spherical cap diffraction process from the inside to the outside, reaches the radius r h Holographic spherical crown surface, denoted as U h ; Finally, through the hologram encoding algorithm, the complex amplitude distribution of the diffraction field on the holographic spherical crown surface is encoded into a hologram that can be loaded and modulated by the spatial light modulator; the mathematical process of the calculation generation method is expressed as: Holo=Encode{IOP_SCD{Filter[OIP_SCD(U s , R, r e ), φ f , θ f ], r e , rh}}, where OIP_SCD() represents the diffraction process from the outer spherical cap to the inner spherical cap, Filter[(), φ f , θ f ] represents the filtering process on the pupil spherical crown surface, IOP_SCD{} represents the diffraction propagation process from the inner spherical crown to the outer spherical crown; Encode{} represents the hologram encoding process; The specific reproduction method of the large-viewing-angle holographic Maxwell display based on spherical crown diffraction is as follows: firstly, the computational hologram Holo is loaded onto a spatial light modulator, and then by observing at the position of the pupil spherical crown surface, the human eye can see a clear holographic reconstructed image behind the spherical crown surface of the original object.

[0004] This method combines holographic Maxwell display with spherical crown diffraction and uses filtering to control depth of field and image quality, thereby realizing holographic Maxwell display with flexible control parameters at a large viewing angle. Theoretically, this method can cover the complete viewing angle range required by the human eye, does not require a complex optical path, and has flexible control over performance parameters such as depth of field and image quality, and has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Attached Figure 1 It is the diffraction model of the holographic display method of the present invention.

[0006] Attached Figure 2 The holographic surface diffraction field distribution and the corresponding holographic reconstructed image generated when the horizontal field of view and the vertical field of view are selected as -π / 3~π / 3 and -π / 6~π / 6 respectively; (a1)(a2) original image, (b1)(b2) holographic surface diffraction field distribution, (c1)(c2) reconstructed image.

[0007] Attached Figure 3 Schematic diagram of the reconstruction method of the present invention.

[0008] Note: The above drawings are only schematic and not drawn to scale. DETAILED DESCRIPTION

[0009] A typical embodiment of the large viewing angle holographic Maxwell display method based on spherical cap diffraction 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 protection scope of the present invention. Personnel 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 protection scope of the present invention.

[0010] The specific implementation of the method of the present invention is as follows: Large viewing angle holographic Maxwell display method based on spherical cap diffraction, such as Figure 1As shown, there are several steps as follows: A hologram calculation generation method for a large viewing angle holographic Maxwell display based on spherical crown diffraction, the specific steps are as follows: Step 1, the object light wave U located at the outer spherical crown with a radius R s , after the spherical crown diffraction process from outside to inside, we get e The diffraction field distribution U of the equivalent pupil sphere crown e ; Step 2, obtain the diffraction field U e The filtering process is to set the diffraction field larger than the required filter aperture to zero, where the size of the filter aperture will determine the depth of field and reconstruction quality of the holographic display; Step 3, the filtered diffraction field, after the spherical cap diffraction process from the inside to the outside, reaches the radius r h Holographic spherical crown surface, denoted as U h ; Finally, through the hologram encoding algorithm, the complex amplitude distribution of the diffraction field on the holographic spherical crown surface is encoded into a hologram that can be loaded and modulated by the spatial light modulator; the mathematical process of the calculation generation method is expressed as: Holo=Encode{IOP_SCD{Filter[OIP_SCD(U s , R, r e ), φ f , θ f ], r e , r h}}, where OIP_SCD() represents the diffraction process from the outer spherical cap to the inner spherical cap, Filter[(), φ f , θ f ] represents the filtering process on the pupil spherical crown surface, IOP_SCD{} represents the diffraction propagation process from the inner spherical crown to the outer spherical crown; Encode{} represents the hologram encoding process; The specific reproduction method of the large-viewing-angle holographic Maxwell display based on spherical crown diffraction is as follows: firstly, the computational hologram Holo is loaded onto a spatial light modulator, and then by observing at the position of the pupil spherical crown surface, the human eye can see a clear holographic reconstructed image behind the spherical crown surface of the original object.

[0011] In the example of the present invention, in the hologram generation process of the large viewing angle holographic Maxwell display method based on spherical crown diffraction, when calculating the diffraction field distribution from the object spherical crown surface to the pupil spherical crown surface, the function of the diffraction process is OIP_SCD(U s , R,r e ), specifically expressed as OIP_SCD(U s , R, r e )=∬ s {U s×[exp(ikd) / d]×cosα}dS, where i is the imaginary unit, k=2π / λ, d is the diffraction distance, λ is the wavelength, and cosα is the tilt factor; the specific calculation formula for the diffraction distance d is: d={R 2 +r e 2 -2Rr e ×(sinθ e sinθ s +cosθ e cosθ s cos(φ e -φ s )]} 1 / 2 , where θ s and θ e are the meridian angle variables of the object spherical crown surface and the pupil spherical crown surface, φ s and φ e They are the sagittal direction angle variables of the object spherical crown surface and the pupil spherical crown surface respectively.

[0012] In the example of the present invention, in the hologram generation process of the large viewing angle holographic Maxwell display method based on spherical crown diffraction, when the diffraction field of the pupil spherical crown surface is filtered, the function of the process is U1=Filter[OIP_SCD(U s , R,r e ), φ f , θ f ],φ f and θ f It determines the size of the filter aperture and sets the diffraction field to zero at positions beyond the corresponding aperture range, which will affect the depth of field and imaging quality of the final imaging.

[0013] In the example of the present invention, in the hologram generation process of the large viewing angle holographic Maxwell display method based on spherical crown diffraction, when calculating the diffraction field distribution from the pupil spherical crown surface to the holographic spherical crown surface, the function of the diffraction process is IOP_SCD{U1, r e ,r h}, specifically OIP_SCD(U1, R, r e )=∬ s {U1×[exp(-ikl) / (-l)]×cosβ}dS, where cosβ is the tilt factor and l is the diffraction distance. Because it is reverse diffraction, the sign is reversed. The specific calculation formula for the diffraction distance l is: l={r e 2 +r h 2 -2r e r h ×(sinθ e sinθh +cosθ e cosθ h cos(φ e -φ h )]} 1 / 2 , where θ e and θ h are the meridian angle variables of the pupil spherical crown and the holographic spherical crown, φ e and φ h They are the sagittal direction angle variables of the pupil spherical crown and the holographic spherical crown respectively.

[0014] In the example of the present invention, the encoding process function of the holographic spherical crown diffraction field is Encode(), specifically a phase function.

[0015] The content of the present invention is further explained below in conjunction with embodiments and drawings: During the hologram calculation and generation process, the radius of the object spherical crown is 450 mm, and the radius of the holographic spherical crown and the pupil spherical crown are 300 mm and 5 mm respectively. The reconstruction depth is 1.25 m, and the wavelength λ is 12 μm. The horizontal field of view and the vertical field of view are selected as -π / 3~π / 3 and -π / 6~π / 6 respectively. The target image resolution of 2048×1024 is selected to meet the Nyquist sampling criterion. The reconstruction results of the method of the present invention at a depth of 1.25 m are as follows Figure 2 As shown in the figure, (a1)(a2) is the original image, (b1)(b2) is the diffraction field distribution of the holographic surface, and (c1)(c2) is the reconstructed image. From the results, the method of the present invention successfully realizes the large-viewing angle holographic Maxwell display based on spherical crown diffraction. In addition, the schematic diagram of the hologram reconstruction method is shown in Figure 3 As shown, by observing at the position of the pupil spherical crown surface, the human eye can see a clear holographic reconstructed image located behind the spherical crown surface of the original object.

[0016] Therefore, the method of the present invention breaks through the problem of insufficient immersion caused by the limited viewing angle of traditional Maxwell display, and realizes a large-viewing angle holographic Maxwell display based on spherical crown diffraction, which has great application prospects.

Claims

1. Large viewing angle holographic Maxwell display method based on spherical cap diffraction, Features Proceed as follows: (i) A hologram computational generation method for a large-viewing-angle holographic Maxwell display based on spherical crown diffraction, the specific steps are as follows: Step 1, the object light wave U located at the outer spherical crown with a radius R s , after the spherical crown diffraction process from outside to inside, we get e The diffraction field distribution U of the equivalent pupil sphere crown e ; Step 2, obtain the diffraction field U e The filtering process is to set the diffraction field larger than the required filter aperture to zero, where the size of the filter aperture will determine the depth of field and reconstruction quality of the holographic display; Step 3, the filtered diffraction field, after the spherical cap diffraction process from the inside to the outside, reaches the radius r h Holographic spherical crown surface, denoted as U h ; Finally, through the hologram encoding algorithm, the complex amplitude distribution of the diffraction field on the holographic spherical crown surface is encoded into a hologram that can be loaded and modulated by the spatial light modulator; the mathematical process of the calculation generation method is expressed as: Holo=Encode{IOP_SCD{Filter[OIP_SCD(U s , R, r e ), φ f , θ f ], r h }}, where OIP_SCD() represents the diffraction process from the outer spherical cap to the inner spherical cap, Filter[(), φ f , θ f ] represents the filtering process on the pupil spherical crown surface, IOP_SCD{} represents the diffraction propagation process from the inner spherical crown to the outer spherical crown; Encode{} represents the hologram encoding process; (ii) The specific reproduction method of the large-viewing-angle holographic Maxwell display based on spherical crown diffraction is as follows: first, the computational hologram Holo is loaded onto a spatial light modulator, and then by observing at the position of the pupil spherical crown surface, the human eye can see a clear holographic reconstructed image located behind the spherical crown surface of the original object.

Images