Spherical crown holographic display method based on occlusion utilization

Abstract

The present invention proposes a spherical crown holographic display method based on occlusion utilization. The method is based on an occlusion utilization method for a spherical diffraction model, which can utilize the information of the occlusion surface and improve the optical utilization rate of the diffraction model in the actual optical path system. The method includes three parts: occlusion utilization for a spherical diffraction model, a spherical crown diffraction model based on occlusion utilization, and a spherical crown holographic display based on occlusion utilization. The method not only retains the characteristics of a 360° viewing angle in the horizontal direction, but also improves the angle in the vertical direction, and has a higher optical utilization efficiency. In addition, by using a variety of traditional encoding methods to reconstruct images, it is proved that the method is applicable to a variety of encoding methods. Finally, by reconstructing images at different distances, it is verified that the method can achieve three-dimensional display.

Description

Technical Field

[0001] The invention relates to a holographic display technology, in particular to a method for generating a spherical hologram. Background Art

[0002] As the most ideal true three-dimensional display technology, holographic display has always received great attention. Spherical holograms have been widely studied because of their wide display viewing angle range. When studying the generation and reconstruction of spherical holograms, in order to avoid aliasing in the reconstructed image and affect the viewing quality, an occlusion culling method is usually used. This method is to eliminate aliasing by culling the occluded surface of the holographic surface of the spherical diffraction model relative to the display surface when generating a spherical hologram. However, the diffraction model based on the occlusion culling method has a low optical utilization rate in the actual optical path system, which will affect the quality of the reconstructed image and the viewing effect during display. Summary of the invention

[0003] In view of the problem that the optical utilization rate of the diffraction model based on the above-mentioned occlusion culling method is low in the actual optical path system, the present invention proposes a spherical crown holographic display method based on occlusion utilization. The proposed method is based on a method of occlusion utilization for a spherical diffraction model, which can utilize the information of the occlusion surface, and can improve the optical utilization rate of the diffraction model in the actual optical path system while solving the aliasing problem. The method includes three parts: occlusion utilization for a spherical diffraction model, a spherical crown diffraction model based on occlusion utilization, and a spherical crown holographic display based on occlusion utilization.

[0004] The occlusion utilization method for the spherical diffraction model is specifically divided into three steps: ① adopting two diffraction models of the sphere propagating from the inside to the outside and from the outside to the inside, ② defining the occlusion utilization model and proposing a light path selection function for the spherical diffraction model, ③ obtaining the diffraction calculation formula of the occlusion utilization method; the spherical crown diffraction model based on occlusion utilization is specifically divided into three steps: ① obtaining the spherical crown diffraction model, ② proposing a light path selection function for the spherical crown diffraction model, ③ obtaining the diffraction calculation formula of the spherical crown diffraction model based on occlusion utilization; the spherical crown holographic display based on occlusion utilization is specifically divided into two steps: ① generating the diffraction field of the spherical crown, ② encoding, reconstruction and display.

[0005] The two diffraction models using a spherical surface that propagates from the inside to the outside and from the outside to the inside refer to spherical diffraction models, including two diffraction models that propagate from the inside to the outside and from the outside to the inside. The point spread function during diffraction propagation is exp(jkd)cosα / jkd, wherein d is the diffraction distance, k is the wave number, and j is the imaginary unit. The tilt factor cosα of the spherical diffraction model that propagates from the inside to the outside is (RcosΔφcosΔθ-r) / d, and the tilt factor cosα of the spherical diffraction model that propagates from the outside to the inside is (R-rcosΔφcosΔθ) / d, wherein R is the outer sphere radius, r is the inner sphere radius, Δφ represents the vertical change angle, and Δθ represents the horizontal change angle.

[0006] The optical path selection function for the spherical diffraction model is to define the occlusion utilization model and propose an optical path selection function to restrict the point spread function of the spherical diffraction model. When d≥(R 2 +r 2 ) 1 / 2 When d<(R 2 +r 2 ) 1 / 2 When , the light is eliminated and the value of the light path selection function is 0.

[0007] The occlusion utilization method refers to using the proposed optical path selection function to restrict the point spread function of the spherical diffraction model, and obtaining a diffraction calculation formula for occlusion utilization of the spherical diffraction model.

[0008] The spherical cap diffraction model is a spherical cap diffraction model obtained by limiting the vertical angle of the spherical surface diffraction model, and the maximum value of the vertical angle φ is denoted as φ m .

[0009] The optical path selection function for the spherical crown diffraction model refers to a optical path selection function for the spherical crown diffraction model. When d≥(R 2 +r 2 +2Rrcos(φ+φ m )) 1 / 2 When d<(R 2 +r 2 +2Rrcos(φ+φ m )) 1 / 2 When , the optical path selection function is 0.

[0010] The diffraction calculation formula of the spherical crown diffraction model based on occlusion utilization refers to using the proposed optical path selection function to limit the propagation of light in the spherical crown diffraction model, that is: multiplying the proposed optical path selection function with the point spread function of the spherical crown diffraction model to obtain the diffraction calculation formula of the spherical crown diffraction model based on occlusion utilization.

[0011] The generating of the diffraction field of the spherical cap refers to generating the diffraction field of the spherical cap by using a diffraction calculation formula of a spherical cap diffraction model based on occlusion utilization.

[0012] The encoding, reconstruction and display refer to encoding the obtained diffraction field to generate a spherical crown hologram, loading the obtained hologram onto a spatial light modulator in an actual optical path, and realizing reconstruction and display of the spherical crown hologram.

[0013] The advantages of this method are: the proposed spherical crown holographic display method is a method based on occlusion utilization, which can reuse the information of the previously removed occlusion surface and improve the optical utilization rate of the diffraction model in the actual optical path system. Compared with the spherical diffraction model, the spherical crown diffraction model not only retains the characteristics of 360° viewing angle in the horizontal direction, but also improves the vertical angle and has greater spatial flexibility. At the same time, this method is also applicable to a variety of traditional encoding methods. Finally, the introduced point spread function allows the reconstructed image to be reconstructed at different positions to achieve three-dimensional display. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 It is a schematic diagram of the shielding utilization of the spherical diffraction model of the present invention.

[0015] Attached Figure 2 It is a schematic diagram of the spherical cap diffraction model based on occlusion utilization of the present invention.

[0016] Attached Figure 3 The results of encoding and reconstruction by various conventional encoding methods of the present invention are shown in Figure 3(a) as the original image, Figure 3(b) and Figure 3(c) are the images encoded and reconstructed using the amplitude truncation method without adding random phase and adding random phase, respectively, Figure 3(d) is the image encoded and reconstructed using the time division multiplexing method with adding random phase, and Figure 3(e) and Figure 3(f) are the images encoded and reconstructed using the dual phase method with adding random phase and without adding random phase, respectively.

[0017] Attached Figure 4 Figure 2. Diffraction fields generated for different distances and reconstructed optical results for the present invention. DETAILED DESCRIPTION

[0018] A typical embodiment of a spherical crown holographic display method based on occlusion utilization of the present invention is described in detail below, and the method is further described in detail. It is necessary to point out here that the following embodiments are only used to further illustrate the method and cannot be understood as limiting the protection scope of the method. Personnel skilled in the art in the field can make some non-essential improvements and adjustments to the method based on the above content of the method, which still fall within the protection scope of the present invention.

[0019] The present invention proposes a spherical crown holographic display method based on occlusion utilization, which includes three parts: occlusion utilization for a spherical surface diffraction model, a spherical crown diffraction model based on occlusion utilization, and a spherical crown holographic display based on occlusion utilization.

[0020] The occlusion utilization method for the spherical diffraction model is specifically divided into three steps: ① adopting two diffraction models of the sphere propagating from the inside to the outside and from the outside to the inside, ② defining the occlusion utilization model and proposing a light path selection function for the spherical diffraction model, ③ obtaining the diffraction calculation formula of the occlusion utilization method; the spherical crown diffraction model based on occlusion utilization is specifically divided into three steps: ① obtaining the spherical crown diffraction model, ② proposing a light path selection function for the spherical crown diffraction model, ③ obtaining the diffraction calculation formula of the spherical crown diffraction model based on occlusion utilization; the spherical crown holographic display based on occlusion utilization is specifically divided into two steps: ① generating the diffraction field of the spherical crown, ② encoding, reconstruction and display.

[0021] The two diffraction models of spherical surface propagation from inside to outside and from outside to inside refer to the spherical surface diffraction model, including two diffraction models of propagation from inside to outside and from outside to inside. The diffraction calculation formula U d =U o *h, where * represents convolution, U d and U o are the diffraction field and object field respectively, h is the point spread function exp(jkd)cosα / jkd during diffraction propagation, where d is the diffraction distance, k is the wave number, j is the imaginary unit, the tilt factor cosα of the spherical diffraction model propagating from the inside to the outside is (RcosΔφcosΔθ-r) / d, and the tilt factor cosα of the spherical diffraction model propagating from the outside to the inside is (R-rcosΔφcosΔθ) / d, where R is the outer sphere radius, r is the inner sphere radius, Δφ represents the vertical change angle, and Δθ represents the horizontal change angle.

[0022] The optical path selection function for the spherical diffraction model is to define the occlusion utilization model and propose an optical path selection function. number The point spread function of the spherical diffraction model is restricted when d≥(R 2 +r 2 ) 1 / 2When d<(R 2 +r 2 ) 1 / 2 When , the light is eliminated and the value of the light path selection function is 0.

[0023] The occlusion utilization method refers to using the proposed optical path selection function to restrict the point spread function of the spherical diffraction model, and obtaining a diffraction calculation formula for occlusion utilization of the spherical diffraction model.

[0024] The spherical cap diffraction model is a spherical cap diffraction model obtained by limiting the vertical angle of the spherical surface diffraction model, and the maximum value of the vertical angle φ is denoted as φ m .

[0025] The optical path selection function for the spherical crown diffraction model refers to a optical path selection function for the spherical crown diffraction model. When d≥(R 2 +r 2 +2Rrcos(φ+φ m )) 1 / 2 When d<(R 2 +r 2 +2Rrcos(φ+φ m )) 1 / 2 When , the optical path selection function is 0.

[0026] The diffraction calculation formula of the spherical cap diffraction model based on occlusion utilization refers to limiting the light propagation in the spherical cap diffraction model by using the proposed light path selection function, that is, multiplying the proposed light path selection function by the point spread function of the spherical cap diffraction model to obtain the diffraction calculation formula U of the spherical cap diffraction model based on occlusion utilization. d =∫U o * θ h”dφ, where * θ represents the convolution in the horizontal direction, ∫dφ represents the one-dimensional integral in the vertical direction, and h” is the point spread function of the spherical cap diffraction model.

[0027] The diffraction field of the spherical cap refers to the diffraction field of the spherical cap generated by using a diffraction calculation formula of a spherical cap diffraction model based on occlusion utilization.

[0028] The encoding, reconstruction and display mentioned above refer to using various encoding methods such as amplitude truncation method, time division multiplexing method, dual phase method, etc. to encode the obtained diffraction field to generate a hologram, and load the obtained hologram onto the spatial light modulator in the actual optical path to realize the reconstruction and display of the spherical crown hologram.

[0029] In the example of the present invention, a 3072*512 grayscale image is used, the wavelength λ is 250 μm, and the inner spherical cap radius r and the outer spherical cap radius R are 5 cm and 50 cm respectively. Figure 3 The encoding and reconstruction result diagram of various conventional encoding methods of the present invention is encoded and reconstructed using conventional encoding methods such as amplitude truncation method, time division multiplexing method and dual phase method. Figure 3 The results show that the invention is applicable to a variety of traditional encoding methods. Figure 4 The diffraction fields and reconstructed optical results generated for different distances of the present invention. The outer spherical cap radius R is 15cm, 30cm, and 45cm respectively. The results show that the method can reconstruct images at different distances and realize three-dimensional display.

Claims

1. A spherical crown holographic display method based on occlusion utilization, characterized in that The method comprises three parts: occlusion utilization of spherical diffraction model, spherical cap diffraction model based on occlusion utilization, and spherical cap holographic display based on occlusion utilization; the occlusion utilization method for spherical diffraction model is specifically described as follows: step 1, spherical diffraction model, including two diffraction models propagating from inside to outside and from outside to inside, and its point spread function during diffraction propagation is exp(jkd)cosα / jkd, wherein d is the diffraction distance, k is the wave number, j is the imaginary unit, and the spherical cap propagating from inside to outside ... The tilt factor cosα of the surface diffraction model is (RcosΔφcosΔθ-r) / d, and the tilt factor cosα of the spherical diffraction model propagating from outside to inside is (R-rcosΔφcosΔθ) / d, where R is the radius of the outer sphere, r is the radius of the inner sphere, Δφ represents the vertical change angle, and Δθ represents the horizontal change angle; Step 2, facing the spherical diffraction model, define the occlusion utilization model, and propose an optical path selection function to restrict the point spread function of the spherical diffraction model. When d≥(R 2 +r 2 ) 1 / 2 When d<(R 2 +r 2 ) 1 / 2 When , the light is eliminated and the value of the light path selection function is 0; step three, the proposed light path selection function is used to limit the point spread function of the spherical diffraction model to obtain the diffraction calculation formula for the occlusion utilization of the spherical diffraction model; the spherical crown diffraction model based on occlusion utilization is specifically described as: step one, the vertical angle of the spherical diffraction model is restricted to obtain the spherical crown diffraction model, and the maximum value of its vertical angle φ is recorded as φ m ; Step 2, propose a light path selection function for the spherical crown diffraction model. When d≥(R 2 +r 2 +2Rrcos(φ+φ m )) 1 / 2 When d<(R 2 +r 2 +2Rrcos(φ+φ m )) 1 / 2 When , the optical path selection function is 0; step three, using the proposed optical path selection function to restrict the propagation of light in the spherical crown diffraction model, that is: multiplying the proposed optical path selection function with the point spread function of the spherical crown diffraction model to obtain the diffraction calculation formula of the spherical crown diffraction model based on occlusion utilization; the spherical crown holographic display based on occlusion utilization is specifically described as: step one, using the diffraction calculation formula of the spherical crown diffraction model based on occlusion utilization to generate the diffraction field of the spherical crown; step two, encoding the obtained diffraction field to generate a spherical crown hologram, and loading the obtained hologram onto the spatial light modulator in the actual optical path to realize the reconstruction and display of the spherical crown hologram.

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