• Journal of information and communication convergence engineering
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• v.11 no.4
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• pp.282-287
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• 2013

A real-time digital holographic display is the core technology for the next-generation 3DTV. Holographic display requires a considerably large amount of calculation. If generating a large number of digital holograms is intended, the amount of calculation and the time required increase exponentially. This is a significant obstacle in a real-time hologram service. This paper proposes an algorithm that increases the speed of generating a Fresnel hologram by using a recursive addition operation covering the entire coordinate array of a digital hologram. The 3D object designed to calculate the digital hologram uses a depth-map image produced by computer graphics. The proposed algorithm is a technique that performs the computer-generated holography (CGH) operation with only recursive addition of all of the hologram's coordinates by analyzing the regularity between the 3D object and the digital hologram coordinates. The experimental results show that the proposed algorithm increases the operation speed by 70% over the technique using the conventional CGH equation and by more than 30% over the previously proposed recursive technique.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.297-300
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• 1999

중요한 정보 암호화하여 복수 회원에게 분산시킨 후 회원의 합의에 의하여 해독이 가능하게 하는 thresholding scheme은 visual cryptography에 의하여 시각적인 표현이 가능하게 되었다. 그러나 visual cryptography는 표현의 한계로 응용범위가 극히 제한되었다. 이 논문에서는 visual cryptography의 응용범위를 수학에서 광학으로 확장하기 위하여 binary computer generated hologram을 encryption하는 방법을 제시하고 security 특성을 분석한다.

• Current Optics and Photonics
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• v.5 no.4
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• pp.409-420
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• 2021

We propose a method to synthesize a color non-hogel-based computer-generated-hologram (CGH) from light field data of a three-dimensional scene with a hologram pixel pitch shared for all color channels. The non-hogel-based CGH technique generates a continuous wavefront with arbitrary carrier wave from given light field data by interpreting the ray angle in the light field to the spatial frequency of the plane wavefront. The relation between ray angle and spatial frequency is, however, dependent on the wavelength, which leads to different spatial frequency sampling grid in the light field data, resulting in color aberrations in the hologram reconstruction. The proposed method sets a hologram pixel pitch common to all color channels such that the smallest blue diffraction angle covers the field of view of the light field. Then a spatial frequency sampling grid common to all color channels is established by interpolating the light field with the spatial frequency range of the blue wavelength and the sampling interval of the red wavelength. The common hologram pixel pitch and light field spatial frequency sampling grid ensure the synthesis of a color hologram without any color aberrations in the hologram reconstructions, or any loss of information contained in the light field. The proposed method is successfully verified using color light field data of various test or natural 3D scenes.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.5
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• pp.548-554
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• 2009

We propose an automatic inspection system for hologram with multiple patterns. The system hardware consists of illuminations, camera, and vision processor. Multiple illuminations using LEDs are arranged in different directions to acquire each image of patterns. The system software consists of pre-processing, pattern generation, and pattern matching. The acquired images of input hologram are compared with their reference patterns by developed matching algorithm. To compensate for the positioning error of input hologram, reference patterns of hologram for different position should be generated in on-line. We apply a frequency transformation based CGH(computer-generated hologram) method to generate reference images. For the fast pattern matching, we also apply the matching method in the frequency domain. Experimental results for hologram of Korean currency are then presented to verify the usefulness of proposed system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.1
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• pp.129-139
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• 2013

In this paper, we proposed a new hardware architecture for calculating digital holograms at high speed, and verified it with field programmable gate array (FPGA). First, we rearranged memory scheduling and algorithm of computer generated hologram (CGH), and then introduced pipeline technique into CGH process. Finally we proposed a high-performance CGH processor. The hardware was implemented for the target of FPGA, which calculates a unit region of holograms, and it was verified using a hardware environment of NI Inc. and a FPGA of Xilinx Inc. It can generate a hologram of $16{\times}16$ size, and it takes about 4 sec for generating a hologram of a $1,024{\times}1,024$ size, using 6K point sources.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.242-245
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• 2009

This paper proposes an algorithm that increases the speed of generating a Fresnel hologram using a recursive addition operation covering the whole coordinate array of a digital hologram. The 3D object designed to calculate the digital hologram used the depth-map image produced by computer graphics (CG). The proposed algorithm is a technique that performs CGH (computer generated hologram) operation with only the recursive addition from the hologram's whole coordinates by analyzing the regularity between the 3D object and the digital hologram coordinates. The experimental results showed that the proposed algorithm increased operation speed by 30% over the technique using the conventional CGH equation.

• Journal of Broadcast Engineering
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• v.25 no.6
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• pp.836-844
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• 2020

A very large number of pixels is required to generate a computer generated hologram (CGH) with a large-size and wide viewing angle equivalent to that of an analog hologram, which incurs a very large amount of computation. For this reason, a high-performance computing device and long computation time were required to generate high-definition CGH. To solve these problems, in this paper, we propose a technique for generating high-definition CGH by arraying the pre-calculated low-definition CGH and multiplying the appropriately-shifted concave lens function. Using the proposed technique, 0.1 Gigapixel CGH recorded by the point cloud method can be used to calculate 2.5 Gigapixels CGH at a very high speed, and the recorded hologram image was successfully reconstructed through the experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1053-1059
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• 2005

The computer generated hologram (CGH) designs and produces digital information for generating 3-D (3-Dimension) image using computer and software instead of optically-sensed hologram of light interference, and it can synthesis a virtual object which is physically not in existence. Since digital hologram includes an amount of data as can be seen at the process of digitization, it is necessary that the data representing digital hologram is reduced for storing, transmission, and processing. As the efforts that are to handle hologram with a type of digital information have been increased, various methods to compress digital hologram called by fringe pattern are groped. Suitable proposal is encoding of hologram. In this paper, we analyzed the properties of CGH using tools of frequency transform, assuming that a generated CGH is a 2D image by introducing DWT that is known as the better tool than DCT for frequency transform. The compression and reconstruction result which was extracted from the wavelet-based codecs illustrates that it has better properties for reconstruction at the maximum 2 times higher compression rate than the Previous researches of Yoshikawa[2] and Thomas[3].

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.3
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• pp.110-116
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• 2008

In this paper, we proposed an improvement technique of image encryption using binary phase computer generated hologram(BPCGH) and multi exclusive-OR(XOR) operations. For the encryption process, a BPCGH that reconstructs the original image is designed, using an iterative algorithm, and the resulting hologram is regarded as the image to be encrypted. The BPCGH is encrypted through the exclusive-OR operation with the random generated phase key image. Then the encrypted image is divided into several slide images using XOR operations. So, the performance of encryption for the image is improved. For the decryption process, we cascade the encrypted slide images and phase key image and interfere with reference wave. Then decrypted hologram image is transformed into phase information. Finally, the original image is recovered by an inverse Fourier transformation of the phase information. If the slide images are changed, we can get various decrypted BPCGH images. In the proposed security system, without a random generated key image, the original image can not be recovered. And we recover another hologram pattern according to the slide images, so it can be used in the differentiated authorization system.

• Journal of Broadcast Engineering
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• v.24 no.3
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• pp.452-462
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• 2019

A digital hologram, which is one of the next generation visual systems, can be generated and displayed in various formats, and a digital hologram is created in accordance with the characteristics of the system for display. Diffraction efficiency can be used as a measure of the characteristics of digital holograms generaged under various conditions in various display environments. In this paper, diffraction efficiency for computer-generated hologram (CGH) under various conditions was measured. This paper discusses the generation conditions that should be considered in hologram display. We compared each condition by measuring the intensity of the first order diffraction pattern of the fringe generated under the Fresnel condition for the phase hologram. Through this paper, we showed the tend about characteristics of the diffraction efficiency according to object point, reconstruction distance, laser and SLM.