• Title/Summary/Keyword: digital hologram

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A Frequency Characteristic Analysis of Digital Hologram in Fresnel Transform Domain (Fresnel 변환영역에서 디지털 홀로그램의 주파수 특성분석)

  • Choi, Hyun-Jun;Seo, Young-Ho;Kim, Dong-Wook
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.16 no.7
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    • pp.1505-1511
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    • 2012
  • 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 digital hologram. This paper analyzed the properties of digital hologram using tools of frequency transform, assuming that a generated digital hologram is a 2D image by introducing Fresnel Transform. The analysis results of digital hologram to be proposed in this paper are being expected to be used as the core techniques for an encoding of digital hologram.

Digital Holographic Contents Manipulation using Convert and synthesize of Depth-map (깊이정보의 변환 및 합성 기법을 이용한 디지털 홀로그래픽 콘텐츠 저작)

  • Choi, Hyun-Jun;Seo, Young-Ho;Kim, Dong-Wook
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.4
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    • pp.1010-1019
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    • 2013
  • Recently, research on hologram, which can realize perfect 3-dimensional imaging, becomes more active. But hologram has the defect that it costs a lot in generation. Thus, this paper proposes a method to generate a new digital hologram contents by manipulating the existing digital hologram contents. That is, this paper proposes the method to manipulating the digital hologram contents by manipulating and/or synthesizing the depth information to get a new digital hologram contents. The proposed methods have been experimented with various depth informations and digital hologram contents. For each kind of depth information, it has been manipulated for its position and distance. The result was converted to a digital hologram by the computer-generated hologram method and the resulting hologram was reconstructed.

Fast Generation Methods for Computer-Generated Hologram Using a Modified Recursive Addition Algorithm

  • Choi, Hyun-Jun
    • 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.

Design and Implementation of Digital Hologram Content Using Modified Depth Information

  • Park, Scott;Choi, Hyun-Jun;Kim, Moon-Seok;Kim, Dong-Wook;Seo, Young-Ho
    • Journal of information and communication convergence engineering
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    • v.12 no.2
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    • pp.122-127
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    • 2014
  • This paper proposes a method to manipulate digital hologram contents by manipulating and/or synthesizing the depth information. To synthesize digital holograms themselves in order to create new digital hologram contents. This paper uses both the depth information obtained by converting the disparity information by using a stereo matching method and that obtained by taking pictures with a depth camera. In addition, assuming that digital holograms are created using the computer-generated holography method, we propose a technique for authoring and compositing hologram contents by using either the changes in the three-dimensional positions of objects in the hologram or by combining the objects with other contents by means of changes in the depth information. Further, more than one digital hologram was synthesized to form a hologram. The reconstructed result from the synthesized hologram also contained all the objects in each digital hologram before synthesis at the same positions and distances.

Fast Digital Hologram Generation Using True 3D Object (실물에 대한 디지털 홀로그램 고속 생성)

  • Kang, Hoon-Jong;Lee, Gang-Sung;Lee, Seung-Hyun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.11B
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    • pp.1283-1288
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    • 2009
  • In general, a 3D computer graphic model is being used to generate a digital hologram as theinput information because the 3D information of an object can be extracted from a 3D model, easily. The 3D information of a real scene can be extracted by using a depth camera. The 3D information, point cloud, corresponding to real scene is extracted from a taken image pair, a gray texture and a depth map, by a depth camera. The extracted point cloud is used to generate a digital hologram as input information. The digital hologram is generated by using the coherent holographic stereogram, which is a fast digital hologram generation algorithm based on segmentation. The generated digital hologram using the taken image pair by a depth camera is reconstructed by the Fresnel approximation. By this method, the digital hologram corresponding to a real scene or a real object could be generated by using the fast digital hologram generation algorithm. Furthermore, experimental results are satisfactory.

Analysis of Digital Hologram Rendering Using a Computational Method

  • Choi, Hyun-Jun;Seo, Young-Ho;Jang, Seok-Woo;Kim, Dong-Wook
    • Journal of information and communication convergence engineering
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    • v.10 no.2
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    • pp.205-209
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    • 2012
  • To manufacture a real time digital holographic display system capable of being applied to next-generation television, it is important to rapidly generate a digital hologram. In this paper, we analyze digital hologram rendering based on a computer computation scheme. We analyze previous recursive methods to identify regularity between the depth-map image and the digital hologram.

HI-SPEED COMPUTER-GENERATED HOLOGRAM ALGORITHM

  • Choi, Hyun-Jun;Seo, Young-Ho;Yoo, Ji-Sang;Kim, Dong-Wook
    • 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.

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High-Speed Generation Technique of Digital holographic Contents based on GPGPU (GPGPU기반의 디지털 홀로그램 콘텐츠의 고속 생성 기법)

  • Lee, Yoon Hyuk;Kim, Dong Wook;Seo, Young Ho
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.9 no.1
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    • pp.151-163
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    • 2013
  • Recently the attention on digital hologram that is regarded as to be the final goal of the 3-dimensional video technology has been increased. Digital hologram is calculated by modeling the interference phenomenon between an object wave and a reference wave. The modeling for digital holograms is called by computer generated hologram (CGH) Generally, CGH requires a very large amount of calculation. So if holograms are generated in real time, high-speed method should be needed. In this paper, we analyzed CGH equation, optimized it for mapping general purpose graphic processing unit (GPGPU), and proposed a optimized CGH calculation technique for GPGPU by resource allocation and various experiments which include block size changing, memory selection, and hologram tiling. The implemented results showed that a digital hologram that has $1,024{\times}1,024$ resolution can be generated during approximately 24ms, using 1K point clouds. In the experiment, we used two GTX 580 GPGPU of nVidia Inc.

A Digital Hologram Encryption Method Using Data Scrambling of Frequency Coefficients

  • Choi, Hyun-Jun
    • Journal of information and communication convergence engineering
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    • v.11 no.3
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    • pp.185-189
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    • 2013
  • A digital hologram generated by a computer calculation (computer-generated hologram or capture using charge-coupled device [CCD] camera) is one of the most expensive types of content, and its usage is expanding. Thus, it is highly necessary to protect the ownership of digital holograms. This paper presents an efficient visual security scheme for holographic image reconstruction with a low scrambling cost. Most recent studies on optical security concentrate their focus on security authentication using optical characteristics. However, in this paper, we propose an efficient scrambling method to protect a digital hologram. Therefore, we introduce in this paper several scrambling attempts in both the spatial domain and frequency domain on the basis of the results of analyzing the properties of the coefficients in each domain. To effectively hide the image information, 1/4, 1/256, and 1/16,384 of the original digital hologram needs to be scrambled for the spatial-domain scheme, Fresnel-domain scheme, and discrete cosine transform-domain scheme, respectively. The encryption schemes and the analyses in this paper can be expected to be useful in the research on encryption and other works on digital holograms.

Digital Hologram Watermarking using Quad-tree Fresnelet Transform (Quad-tree Fresnelet 변환을 이용한 디지털 홀로그램 워터마킹)

  • Seo, Young Ho;Koo, Ja Myung;Lee, Yoon Hyuk;Kim, Dong Wook
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.9 no.3
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    • pp.79-89
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    • 2013
  • This paper proposes a watermarking scheme to protect ownership of a digital hologram, an ultra-high value-added content. It performs pre-defined levels of quad-tree Fresnelet transforms. The relationship among the same-positional-blocks is extracted as the digital pre-watermark. For the relationship, we use properties of a digital hologram that a hologram pixel retains all the information of the object and that the same size of partial holograms reconstructs the same size of object but different in their view points. Also we mix a set of private data with the pre-watermark and the result is encrypted by a block cipher algorithm with a private key. Experimental results showed that the proposed scheme is very robust for the various malicious and non-malicious attacks. Also because it extracts the watermarking data instead of inserting, the watermarking process does not harm the original hologram data. So, it is expected to be used effectively for invisible and robust watermark for digital holograms.