• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.18-21
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• 2011

디지털 홀로그램은 일반적으로 computer generated hologram(CGH)기법에 의해서 생성된다. 하지만 원리적으로 CGH 기법은 많은 연산량과 복잡도를 요구하고 있기 때문에 실시간으로 디지털 홀로그램을 생성하는 것은 매우 어렵다. 본 논문에서는 CGH 고속연산을 위해 graphics processing unit(GPU)의 병렬처리구조인 CUDA를 사용하였고, 추가적으로 다중 GPU 연산처리를 위해 OpenMP를 사용하였다. 더 나아가 이를 최적화하기 위해서 상수화, 벡터화, 루프풀기 등의 기법들을 제안한다. 결과적으로, 본 논문에서 제안된 기법을 통해서 기존 CPU에서의 CGH 연산속도에 비해 약 8,300배 정도의 속도를 개선할 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.435-436
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• 2018

In this paper, diffraction efficiency for computer-generated hologram (CGH) generated under various conditions was measured. This paper discusses the generation conditions that should be considered in hologram reconstruction. We compared each condition by measuring the intensity of the 1st order diffraction pattern of the fringe generated under the Fresnel condition for the phase and complex hologram.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.578-582
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• 2009

Computer-Generated Hologram (CGH) is generally made by Fourier Transform. CGH is made by an optical reconstruction. Computer-Generated Pseudo Hologram (CGPH) is made up Complex Hadamard Transform instead of CGH which is made by the Fourier Transform. CGPH differs from CGH in point of view the possibility of optical reconstruction. There is an advantage that it cannot be optical reconstruction, in other word, physical leakage of the confidential information is impossible. In this paper, a binary image was converted in Complex Hadamard Transform, and CGPH was made. Improvement of the reconstructed image from CGPH is done by error diffusion method and iterative method. The result that the reconstructed image is improved is shown.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.525-531
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• 2006

Synthesized 3-D CGH of a general three dimensional object is obtained by using a new 3-D coordinates transformation technique. A CCD camera is used to record several projected images of the 3-D object from different viewing angles. The recorded data are numerically calculated and processed to yield two-dimensional complex functions, which are then encoded fer the final synthesized 3-D CGH.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.2
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• pp.257-263
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• 1986

A laser scanner utilizing a computer-generated hologram(CGH) as beam deflector is reported. The CGH optical element has been used mainly for under-filled scanning. Here, a CGH optical element for overfilled scanning is proposed. It can achieve, under the same limitation of fabrication accuracy, better resolution and longer scan length than those for under-filled scanning. Measured scanning characteristics of the laser scanner show the scan length of 40 cm and the beam diameter of 100\ulcorner, where the designed minimum distance between the lines of CGH is 8\ulcorner.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.109-110
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• 2006

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.305-312
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• 2005

In this thesis, Lohmann's algorithm and FFT (fast Fourier transform) are used to synthesize binary-phase holograms. FFT computing is carried out for the calculation of complex wavefronts of $128{\times}128$ sampling points of an object that is numerically specified. Then using the Lohmann's algorithm, the amplitude and the phase of complex wavefronts are encoded in binary holograms on each sampling points. PC (personal computer) and laser printer are used to plot binary-phase holograms and CGH (computer generated holograms) films are obtained from this plot by photographic reduction. Holographic images of numerically specified objects are reconstructed from the He-Ne laser and the inverse Fourier optics system. We estimate the quality of holographic images according to the sampling number, application of random phase, amplitude clipping and bleaching the CGH film. We derive optimized conditions to reconstruct better holographic images and to reduce the speckle noise. FFT and Lohmann's algorithm are implemented with MS Visual BASIC 6.0 for the programming of binary-phase hologram.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.133-142
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• 2012

In this paper, we propose and implement a high-speed algorithm for CGH that is to calculate digital hologram by modeling the interference phenomenon for tow lights. This algorithm changes the computation equations into a parallel-computable ones and implements it with a structure consisting of two kinds of cells (initial calculation cell, and update calculation cell). The parallel computation algorithm is to get the rest hologram pixels concurrently after calculation the first hologram column. Here, the initial calculation cells compute the first column of the hologram and the update calculation cells compute the rest of the hologram. The two kinds of cells performs a pipeline operation to complete the operations of the two cells at the same time. A CGH calculator to compute the hole hologram for a light source is structured by arranging the two kinds of cells. Results from simulation showed that the maximum operation frequency is about 215MHz. So, experiments are performed by setting this frequency and the same environments as the method showing the best performance. As the results, the proposed one could complete the computation of 81.75 CGH frames per second, while the previous method computes 62.9 CGH frames per second.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.713-720
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• 2012

Recently, holography has received much attention as the next generation visual technology. Hologram is obtained by the optical capturing, but in recent years it is mainly produced by the method using computer. This method is named by computer generated hologram (CGH). Since CGH requires huge computational amount, if it is implemented by S/W it can't work in real time. Therefore it should use FPGA or GPU for real time operation. If it is implemented in the type of H/W, it can't obtain the same quality as S/W due to the bit limitation of the internal system. In this paper, we analyze the bit width for minimizing the degradation of the hologram and reducing more hardware resources and propose guidelines for H/W implementation of CGH. To do this, we performs fixed-points simulations according to main internal variables and arithmetics, analyze the numerical and visual results, and present the optimal bit width according to application fields.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2091-2098
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• 2010

This paper proposes a hologram data compression scheme that uses the existing image/video compression techniques, in which the existing techniques are modified appropriately to fit to the characteristics of hologram. In this paper we use CGH as the hologram data. The proposed scheme uses the generation characteristics of a CGH to consist of a pre-processing, spatial segmentation of a CGH, frequency-transformation with 2D-DCT (2-dimensional discrete cosine transform), and motion estimation and residual image generation in the frequency-domain. It uses H.264/AVC, the lossless compressor BinHex, and a linear quantizer that we have made. From the experiments the proposed scheme showed the image quality of about 25.4 dB at the compression ratio of 10:1 and about 16.5dB at 90:1 compression ratio.