Holographic display can reconstruct the optical wave field of three-dimensional (3D) scenes. Computer- generated hologram (CGH) can simulate the optical transmission process from the 3D object to the hologram plane and avoid complicated experiments. Wavefront recording plane (WRP) is a fast algorithm for CGH, which is placed between the 3D object and the CGH. However, the computational amount is increased when the depth range of the 3D object is expanded. In this paper, we propose a fast calculation algorithm for real-time interactive CGH using a novel Fresnel zone plate (FZP) extension method and ray tracing. In the first step, ray tracing is used to get the amplitude value and the depth value of each object point. The maximum resolution of each FZP is determined according to the distance from the object point to the WRP. In the second step, a preset square portion of each FZP is used to calculate the complex amplitude of the WRP. Then diffraction calculation is performed from the WRP to the hologram plane for calculating CGH, and the computational domain of each FZP is gradually extended as the number of frames increases. The above calculation is repeated when interacting. The computational complexity is effectively reduced because the resolution of each FZP is increased until the maximum resolution is reached, instead of directly calculating each FZP with the maximum resolution. Experiments demonstrate the proposed method can generate CGH in real-time. The resolution of the hologram is 1024x024 and the CGH generation rate is 45.81 frames per second when interacting.
In this paper, a large-size and high-resolution image plane hologram printing method based on spatial light modulator is proposed. The digital content reconstructed by spatial light modulator is recorded on the photopolymer to generate white light visible image plane hologram. It not only breaks the limitations of traditional holography and computer-generated holography, but also has advantage in large-size and high-resolution compared with other printing methods. In the reconstruction process, the large-size reconstruction with different colors is obtained by white light clearly when moving the viewing angle. The method uses 2K hologram to reconstruct 8K object, and the size of image plane hologram can reach 8cm×10cm. Experiments show that the proposed method can generate a large-size and high-resolution image plane hologram of non-existent objects in the real world.
Due to the overlarge pixel pitch of the current available spatial light modulator (SLM), the separated angle of two reconstructed images is too small to realize dual-view holographic 3D display. At the same time, the reconstruction resolution is limited by the resolution of the SLM. In this paper, we propose a high-resolution dual-view display method based on holographic optical element (HOE) printed by computer-generated hologram (CGH). A synthetic phase only hologram of two different 3D objects is calculated by the layer-based angular spectrum diffraction method, and the digital grating is introduced to adjust the position of the reconstructed image. A HOE printed by CGH is used as the light guide plate to redirect the two reconstructed 3D images into the two separated viewing zones simultaneously. Optical experiments demonstrate that the proposed system can realize the function of high-resolution dual-view holographic 3D display
Reflection and refraction images are treated as the texture of the object in computer graphics, which brings wrong depth information when focusing on the object in holographic display. In this paper, a method of ray tracing rendering with complete depth information for computer-generated hologram(CGH) is proposed. Correct depths of reflection and refraction images are calculated, and layer-based method is used to generate CGH. In experiment result, our method truthfully reconstructs the complete depth information of complex scene. Reflection or refraction images and its corresponding media surfaces can be focused on correct depth. All layer data is computed in a single ray tracing procedure, and the generation speed of 1024×1024 CGH for 3D scene divided into 10 layers is 100fps.
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