• Title, Summary, Keyword: Phase encoding

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Efficient Compression Schemes for Double Random Phase-encoded Data for Image Authentication

  • Gholami, Samaneh;Jaferzadeh, Keyvan;Shin, Seokjoo;Moon, Inkyu
    • Current Optics and Photonics
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    • v.3 no.5
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    • pp.390-400
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    • 2019
  • Encrypted images obtained through double random phase-encoding (DRPE) occupy considerable storage space. We propose efficient compression schemes to reduce the size of the encrypted data. In the proposed schemes, two state-of-art compression methods of JPEG and JP2K are applied to the quantized encrypted phase images obtained by combining the DRPE algorithm with the virtual photon counting imaging technique. We compute the nonlinear cross-correlation between the registered reference images and the compressed input images to verify the performance of the compression of double random phase-encoded images. We show quantitatively through experiments that considerable compression of the encrypted image data can be achieved while security and authentication factors are completely preserved.

Real-Time Compressed Video Acquisition System for Stereo 360 VR (Stereo 360 VR을 위한 실시간 압축 영상 획득 시스템)

  • Choi, Minsu;Paik, Joonki
    • Journal of Broadcast Engineering
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    • v.24 no.6
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    • pp.965-973
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    • 2019
  • In this paper, Stereo 4K@60fps 360 VR real-time video capture system which consists of video stream capture, video encoding and stitching module is been designed. The system captures stereo 4K@60fps 360 VR video by stitching 6 of 2K@60fps stream which are captured through HDMI interface from 6 cameras in real-time. In video capture phase, video is captured from each camera using multi-thread in real-time. In video encoding phase, raw frame memory transmission and parallel encoding are used to reduce the resource usage in data transmission between video capture and video stitching modules. In video stitching phase, Real-time stitching is secured by stitching calibration preprocessing.

Image Encryption and Decryption System using Frequency Phase Encoding and Phase Wrapping Method (주파수 위상 부호화와 위상 랩핑 방법을 이용한 영상 암호화 및 복호화 시스템)

  • Seo, Dong-Hoan;Shin, Chang-Mok;Cho, Kyu-Bo
    • Korean Journal of Optics and Photonics
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    • v.17 no.6
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    • pp.507-513
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    • 2006
  • In this paper, we propose an improved image encryption and fault-tolerance decryption method using phase wrapping and phase encoding in the frequency domain. To generate an encrypted image, an encrypting key which denotes the product of a phase-encoded virtual image, not an original image, and a random phase image is zero-padded and Fourier transformed and its real-valued data is phase-encoded. The decryption process is simply performed by performing the inverse Fourier transform for multiplication of the encrypted key with the decrypting key, made of the proposed phase wrapping method, in the output plane with a spatial filter. This process has the advantages of solving optical alignment and pixel-to-pixel mapping problems. The proposed method using the virtual image, which does not contain any information from the original image, prevents the possibility of counterfeiting from unauthorized people and also can be used as a current spatial light modulator technology by phase encoding of the real-valued data. Computer simulations show the validity of the encryption scheme and the robustness to noise of the encrypted key or the decryption key in the proposed technique.

Cloning and Overexpression of the Cdd Gene Encoding Cytidine Deaminase from Salmonella typhimurium

  • Lee, Sang-Mahn
    • Korean Journal of Environmental Biology
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    • v.21 no.1
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    • pp.56-59
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    • 2003
  • The Salmonella typhimurium cdd gene encoding cytidine deaminase (cyti-dine/2'-deoxycytidine aminohydrolase; EC 3.5.4.5.) was isolated through shotgun clon-ing by complementation of the E. coli odd mutation. By subsequent deletion and sub-cloning from the original 3.7 Kb of EcoRI insert (pSAMI), the precise region of the cdd structural gene is located around the BglII site in the middle part of 1.7 Kb of NruI/PvuI segment. The 1.7 Kb containing odd gene wag subcloned to the pUC18 vector and the nucleotide sequence of the cdd gene was determined. When the putative ribosorne-binding site (Shine-Dalgarno sequence) and initiation codon were predicted to be GAGG at the position 459 and ATG at the position 470, respectively, there was an open reading frame of 885 nucleotides, encoding an 294 amino acid protein. The cdd gene expression in E. coli JF611/pSAMI was amplified about 50 fold compared to that of the wild type. The cdd gene expression was maintained in the stationary phase after rea-ching the peak in the late logarithmic phase.

Performance Analysis of Coding According to the Interpolation filter in Inter layer Intra Prediction of H.264/SVC (H.264/SVC의 계층간 화면내 예측에서 보간법에 따른 부호화 성능 분석)

  • Gil, Dae-Nam;Cheong, Cha-Keon
    • Proceedings of the IEEK Conference
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    • pp.225-227
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    • 2009
  • International standard specification, H.264/SVC improved from H.264/AVC, is set up so as to promote free use of huge multimedia data in various channel environments.;H.264/AVC is a international standard speicification for video compression, adopted and commercialized as standard for DMB broadcasting by JVT of ISO/IEC MPEG and ITU-T VCEG. SVC standard uses 'intra/inter prediction' in AVC as well as 'inter-layer intra prediction', 'inter-layer motion prediction' and 'inter-layer residual prediction' to improve efficiency of encoding. Among prediction technologies, 'inter-layer intra prediction' is to use co-located block of up sampled sublevels as a prediction signal. At this time, application of interpolation is one of the most important factors to determine encoding efficiency. SVC's currently using poly-phase FIR filter of 4-tap and 2-tap respectively to luma components. This paper is written for the purpose of analyzing encoding performance according to the interpolation. For this purpose, we applied poly-phase FIR filter of '2-tap', '4-tap' and '6-tap' respectively to luma components and then measured bit-rate, PNSR and running time of interpolation filter. We're expecting that the analysis results of this paper will be utilized for effective application of interpolation filter. SVC standard uses 'intra/inter prediction' in AVC as well as 'inter-layer intra prediction', 'inter-layer motion prediction' and 'inter-layer residual prediction' to improve efficiency of encoding.

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Avalanche and Bit Independence Properties of Photon-counting Double Random Phase Encoding in Gyrator Domain

  • Lee, Jieun;Sultana, Nishat;Yi, Faliu;Moon, Inkyu
    • Current Optics and Photonics
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    • v.2 no.4
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    • pp.368-377
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    • 2018
  • In this paper, we evaluate cryptographic properties of a double random phase encoding (DRPE) scheme in the discrete Gyrator domain with avalanche and bit independence criterions. DRPE in the discrete Gyrator domain is reported to have higher security than traditional DRPE in the Fourier domain because the rotation angle involved in the Gyrator transform is viewed as additional secret keys. However, our numerical experimental results demonstrate that the DRPE in the discrete Gyrator domain has an excellent bit independence feature but does not possess a good avalanche effect property and hence needs to be improved to satisfy with acceptable avalanche effect that would be robust against statistical-based cryptanalysis. We compare our results with the avalanche and bit independence criterion (BIC) performances of the conventional DRPE scheme, and improve the avalanche effect of DRPE in the discrete Gyrator domain by integrating a photon counting imaging technique. Although the Gyrator transform-based image cryptosystem has been studied, to the best of our knowledge, this is the first report on a cryptographic evaluation of discrete Gyrator transform with avalanche and bit independence criterions.

Measurement of Flow Velocity and Flow Visualization with MR PC Image (MR PC 영상을 이용한 유체 흐름 분석)

  • Kim, S.J.;Lee, D.H.;Min, B.G.
    • Proceedings of the KOSOMBE Conference
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    • v.1997 no.05
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    • pp.127-130
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    • 1997
  • Phase-contrast(PC) methods have been used for quantitative measurements of velocity and volume flow rate. In addition, phase contrast cine magnetic resonance imaging (MRI) combines the flow dependent contrast of PC MRI with the ability of cardiac cine imaging to produce images throughout the cardiac cycle. In this method, the through-plane velocity has been encoded generally. However, the accuracy of the flow data can be reduced by the effect of flow direction, finite slice thickness, resolution, pulsatile flow pattern, and so on. In this study we calculated the error caused by misalignment of tomographic plane and flow directon. To reduce this error and encode the velocity for more complex flow, we suggested 3 directional velocity encoding method.

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Mitigation Techniques of Channel Collisions in the TTFR-Based Asynchronous Spectral Phase-Encoded Optical CDMA System

  • Miyazawa, Takaya;Sasase, Iwao
    • Journal of Communications and Networks
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    • v.11 no.1
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    • pp.1-10
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    • 2009
  • In this paper, we propose a chip-level detection and a spectral-slice scheme for the tunable-transmitter/fixed-receiver (TTFR)-based asynchronous spectral phase-encoded optical codedivision multiple-access (CDMA) system combined with timeencoding. The chip-level detection can enhance the tolerance of multiple access interference (MAI) because the channel collision does not occur as long as there is at least one weighted position without MAI. Moreover, the spectral-slice scheme can reduce the interference probability because the MAI with the different frequency has no adverse effects on the channel collision rate. As a result, these techniques mitigate channel collisions. We analyze the channel collision rate theoretically, and show that the proposed system can achieve a lower channel collision rate in comparison to both conventional systems with and without the time-encoding method.

An Adaptive Steganography of Optical Image using Bit-Planes and Multi-channel Characteristics

  • Kang, Jin-Suk;Jeong, Taik-Yeong T.
    • Journal of the Optical Society of Korea
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    • v.12 no.3
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    • pp.136-146
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    • 2008
  • We proposed an adaptive steganography of an optical image using bit-planes and multichannel characteristics. The experiment's purpose was to compare the most popular methods used in optical steganography and to examine their advantages and disadvantages. In this paper we describe two digital methods: the first uses less significant bits(LSB) to encode hidden data, and in the other all blocks of $n{\times}n$ pixels are coded by using DCT(Digital Cosine Transformation), and two optical methods: double phase encoding and digital hologram watermarking with double binary phase encoding by using IFTA(Iterative Fourier Transform Algorithm) with phase quantization. Therefore, we investigated the complexity on bit plane and data, similarity insert information into bit planes. As a result, the proposed method increased the insertion capacity and improved the optical image quality as compared to fixing threshold and variable length method.

Realization of the multi-phase level CGH according to the multi-channel encoding method using a PAL-SLM (PAL-SLM을 이용한 다채널 부호화 방법에 따른 다위상형 CGH의 광학적 구현)

  • Jung, Jong-Rae;Baek, Woon-Sik;Kim, Jung-Hoi;Kim, Nam
    • Korean Journal of Optics and Photonics
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    • v.15 no.4
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    • pp.299-308
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    • 2004
  • We proposed more efficient encoding methods that can design a multi-channel multi-level phase only computer-generated hologram(CGH) that can reconstruct many objects simultaneously without a conjugate image. We used a fabrication technique for the pixel oriented CGH for designing the pattern of the proposed multi-channel CGH. We investigated the difference of the optical efficiency(η), mean square error(MSE) and signal-to-noise ratio(SNR) of multi-channel CGHs that were designed by three kinds of encoding methods according to the number of quantization phase levels, and we estimated the performance of the pattern of the proposed multi-channel CGH. Generally, as the number of input objects' reference patterns stored in the CGH is increased, the reconstruction quality of the CGH is degraded. But we observed through computer simulation that the diffraction efficiency of the 1-ch CGH is 70%, and those of the 2-ch, 4-ch, 8-ch CGHs are 62%, 62% and 63%. Therefore we found that the diffraction efficiencies of the multi-channel CGHs using the newly proposed encoding method are similar to that of 1-ch CGH. We implemented the CGH optically using a liquid crystal spatial light phase modulator that consisted of a PAL-SLM efficiently coupled with a XGA type LCD by an optical lens and an LD for illuminating the LCD. We discussed the output images that are reconstructed from the PAL-SLM.