Browsing by Author "Lam, Edmund Y."

Now showing 1 - 5 of 5
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    Depth resolution enhancement in double-detection optical scanning holography
    Ou, H. Y.; Poon, Ting-Chung; Wong, K. K. Y.; Lam, Edmund Y. (Optical Society of America, 2013-05-01)
    We propose an optical scanning holography system with enhanced axial resolution using two detections at different depths. By scanning the object twice, we can obtain two different sets of Fresnel zone plates to sample the same object, which in turn provides more information for the sectional image reconstruction process. We develop the computation algorithm that makes use of such information, solving a constrained optimization problem using the conjugate gradient method. Simulation results show that this method can achieve a depth resolution up to 1 mu m. (C) 2013 Optical Society of America
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    Depth resolution enhancement in optical scanning holography with a dual-wavelength laser source
    Ke, J.; Poon, Ting-Chung; Lam, Edmund Y. (Optical Society of America, 2011-12-01)
    In this paper, we use two point sources to analyze the depth resolution of an optical scanning holography (OSH) system with a single-wavelength source. A dual-wavelength source is then employed to improve it, where this dual-wavelength OSH (DW-OSH) system is modeled with a linear system of equations. Object sectioning in DW-OSH is obtained with the Fourier domain conjugate gradient method. Simulation results show that, with the two source wavelengths at 543 nm and 633 nm, a depth resolution at 2.5 mu m can be achieved. Furthermore, an OSH system emulator is provided to demonstrate the performance of DW-OSH compared with a conventional OSH system. (C) 2011 Optical Society of America
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    Multiple-image encryption by compressive holography
    Di, Hong; Zheng, Kangfeng; Zhang, Xin; Lam, Edmund Y.; Kim, Taegeun; Kim, You Seok; Poon, Ting-Chung; Zhou, C. H. (Optical Society of America, 2012-03-01)
    We present multiple-image encryption (MIE) based on compressive holography. In the encryption, a holographic technique is employed to record multiple images simultaneously to form a hologram. The two-dimensional Fourier data of the hologram are then compressed by nonuniform sampling, which gives rise to compressive encryption. Decryption of individual images is cast into a minimization problem. The minimization retains the sparsity of recovered images in the wavelet basis. Meanwhile, total variation regularization is used to preserve edges in the reconstruction. Experiments have been conducted using holograms acquired by optical scanning holography as an example. Computer simulations of multiple images are subsequently demonstrated to illustrate the feasibility of the MIE scheme. (C) 2012 Optical Society of America
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    Reconstruction Of Sectional Images in Holography Using Inverse Imaging
    Zhang, X.; Lam, Edmund Y.; Poon, Ting-Chung (Optical Society of America, 2008-01-01)
    This paper discusses the reconstruction of sectional images from a hologram generated by optical scanning holography. We present a mathematical model for the holographic image capture, which facilitates the use of inverse imaging techniques to recover individual sections. This framework is much more flexible than existing work, in the sense that it can handle objects with multiple sections, and possibly corrupted with white Gaussian noise. Simulation results show that the algorithm is capable of recovering a prescribed section while suppressing the other ones as defocus noise. The proposed algorithm is applicable to on-axis holograms acquired by conventional holography as well as phase-shifting holography. (C) 2008 Optical Society of America
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    Three-Dimensional Microscopy And Sectional Image Reconstruction Using Optical Scanning Holography
    Lam, Edmund Y.; Zhang, Xin; Vo, Huy; Poon, Ting-Chung; Indebetouw, Guy J. (Optical Society of America, 2009-08-01)
    Fast acquisition and high axial resolution are two primary requirements for three-dimensional microscopy. However, they are sometimes conflicting: imaging modalities such as confocal imaging can deliver superior resolution at the expense of sequential acquisition at different axial planes, which is a time-consuming process. Optical scanning holography (OSH) promises to deliver a good trade-off between these two goals. With just a single scan, we can capture the entire three-dimensional volume in a digital hologram; the data can then be processed to obtain the individual sections. An accurate modeling of the imaging system is key to devising an appropriate image reconstruction algorithm, especially for real data where random noise and other imaging imperfections must be taken into account. In this paper we demonstrate sectional image reconstruction by applying an inverse imaging sectioning technique to experimental OSH data of biological specimens and visualizing the sections using the OSA Interactive Science Publishing software. (C) 2009 Optical Society of America