Browsing by Author "Qin, Wenlong"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Fast 3D Analytical Affine Transformation for Polygon-Based Computer-Generated Holograms
    Fan, Houxin; Zhang, Bing; Zhang, Yaping; Wang, Fan; Qin, Wenlong; Fu, Qingyang; Poon, Ting-Chung (MDPI, 2022-07-07)
    We present a fast 3D analytical affine transformation (F3DAAT) method to obtain polygon-based computer-generated holograms (CGHs). CGHs consisting of tens of thousands of triangles from 3D objects are obtained by this method. We have attempted a revised method based on previous 3D affine transformation methods. In order to improve computational efficiency, we have derived and analyzed our proposed affine transformation matrix. We show that we have further increased the computational efficiency compared with previous affine methods. We also have added flat shading to improve the reconstructed image quality. A 3D object from a 3D camera is reconstructed holographically by numerical and optical experiments.
  • Thumbnail Image
    Isotropic Two-Dimensional Differentiation Based on Dual Dynamic Volume Holograms
    Wang, Pin; Fan, Houxin; Zhang, Yaping; Yao, Yongwei; Zhang, Bing; Qin, Wenlong; Poon, Ting-Chung (MDPI, 2023-07-17)
    We study the use of two dynamic thick holograms to realize isotropic two-dimensional (2D) differentiation under Bragg diffraction. Acousto-optic modulators (AOMs) are used as dynamic volume holograms. Using a single volume hologram, we can accomplish a first-order derivative operation, corresponding to selective edge extraction of an image. Since the AOM is a 1D spatial light modulator, filtering of the image only occurs along the direction of the sound propagation. To achieve 2D image processing, two AOMs are used within a Mach–Zehnder interferometer (MZI). By aligning one AOM along the x-direction on the upper arm of the interferometer and another AOM along the y-direction on the lower arm, we accomplish the sum of two first-derivative operations, leading to isotropic edge extraction. We have performed both computer simulations and optical experiments to verify the proposed idea. The system provides additional operations in optical computing using AOMs as dynamic holograms.