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Browsing by Author "Kim, Y. S."

Now showing 1 - 4 of 4
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    Low Complexity Compression and Speed Enhancement for Optical Scanning Holography
    Tsang, P. W. M.; Poon, Ting-Chung; Liu, J. Ping; Kim, T.; Kim, Y. S. (Nature Publishing Group, 2016-10-06)
    In this paper we report a low complexity compression method that is suitable for compact optical scanning holography (OSH) systems with different optical settings. Our proposed method can be divided into 2 major parts. First, an automatic decision maker is applied to select the rows of holographic pixels to be scanned. This process enhances the speed of acquiring a hologram, and also lowers the data rate. Second, each row of down-sampled pixels is converted into a one-bit representation with delta modulation (DM). Existing DM-based hologram compression techniques suffers from the disadvantage that a core parameter, commonly known as the step size, has to be determined in advance. However, the correct value of the step size for compressing each row of hologram is dependent on the dynamic range of the pixels, which could deviate significantly with the object scene, as well as OSH systems with different opical settings. We have overcome this problem by incorporating a dynamic step-size adjustment scheme. The proposed method is applied in the compression of holograms that are acquired with 2 different OSH systems, demonstrating a compression ratio of over two orders of magnitude, while preserving favorable fidelity on the reconstructed images.
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    Solving inverse problems for optical scanning holography using an adaptively iterative shrinkage-thresholding algorithm
    Zhao, F. J.; Qu, X. C.; Zhang, Xin; Poon, Ting-Chung; Kim, Taegeun; Kim, Y. S.; Liang, J. M. (Optical Society of America, 2012-03-01)
    Optical scanning holography (OSH) records a three-dimensional object into a two-dimensional hologram through two-dimensional optical scanning. The recovery of sectional images from the hologram, termed as an inverse problem, has been previously implemented by conventional methods as well as the use of l(2) norm. However, conventional methods require time consuming processing of section by section without eliminating the defocus noise and the l(2) norm method often suffers from the drawback of over-smoothing. Moreover, these methods require the whole hologram data (real and imaginary parts) to eliminate the twin image noise, whose computation complexity and the sophisticated post-processing are far from desirable. To handle these difficulties, an adaptively iterative shrinkage-thresholding (AIST) algorithm, characterized by fast computation and adaptive iteration, is proposed in this paper. Using only a half hologram data, the proposed method obtained satisfied on-axis reconstruction free of twin image noise. The experiments of multi-planar reconstruction and improvement of depth of focus further validate the feasibility and flexibility of our proposed AIST algorithm. (c) 2012 Optical Society of America
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    Speckle-free digital holographic recording of a diffusely reflecting object
    Kim, Y. S.; Kim, Taegeun; Woo, S. S.; Kang, H.; Poon, Ting-Chung; Zhou, Changhe (Optical Society of America, 2013-04-01)
    We demonstrate holographic recording without speckle noise using the digital holographic technique called optical scanning holography (OSH). First, we record a complex hologram of a diffusely reflecting (DR) object using OSH. The incoherent mode of OSH makes it possible to record the complex hologram without speckle noise. Second, we convert the complex hologram to an off-axis real hologram digitally and finally we reconstruct the real hologram using an amplitude-only spatial light modulator (SLM) without twin-image noise and speckle noise. To the best of our knowledge, this is the first time demonstrating digital holographic recording of a DR object without speckle noise. (C)2013 Optical Society of America
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    Three-dimensional display of a horizontal-parallax-only hologram
    Kim, Y. S.; Kim, Taegeun; Poon, Ting-Chung; Kim, J. T. (Optical Society of America, 2011-03-01)
    We propose a three-dimensional (3D) holographic display by converting an optically recorded complex full-parallax (FP) hologram to an off-axis horizontal-parallax-only (HPO) hologram. First, we record the complex FP hologram of an object using optical scanning holography. We then convert the complex FP hologram to an off-axis HPO hologram through fringe-matched Gaussian low-pass filtering and with the introduction of an off-axis reference. Finally, we reconstruct the off-axis HPO hologram optically using an amplitude-only spatial light modulator. Until now, only computer-generated HPO holograms have been displayed optically. To the best of our knowledge, this is the first demonstration of a 3D display of an optically recorded HPO hologram. (C) 2011 Optical Society of America