• Title, Summary, Keyword: Phase wrapping

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Practical Encryption and Decryption System using Iterative Phase Wrapping Method (반복적인 위상 랩핑 방법을 이용한 실질적인 암호화 및 복호화 시스템)

  • Seo, Dong-Hoan;Lee, Sung-Geun;Kim, Yoon-Sik
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.6
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    • pp.955-963
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    • 2008
  • In this paper, we propose an improved practical encryption and fault-tolerance decryption method using a non-negative value key and random function obtained with a white noise by using iterative phase wrapping method. A phase wrapping operating key, which is generated by the product of arbitrary random phase images and an original phase image. is zero-padded and Fourier transformed. Fourier operating key is then obtained by taking the real-valued data from this Fourier transformed image. Also the random phase wrapping operating key is made from these arbitrary random phase images and the same iterative phase wrapping method. We obtain a Fourier random operating key through the same method in the encryption process. For practical transmission of encryption and decryption keys via Internet, these keys should be intensity maps with non-negative values. The encryption key and the decryption key to meet this requirement are generated by the addition of the absolute of its minimum value to each of Fourier keys, respectively. The decryption based on 2-f setup with spatial filter is simply performed by the inverse Fourier transform of the multiplication between the encryption key and the decryption key and also can be used as a current spatial light modulator technology by phase encoding of the non-negative values. Computer simulations show the validity of the encryption method and the robust decryption system in the proposed technique.

Optical security system using multi-phase separation and phase-wrapping method (다중 위상 분할과 위상 랩핑 방법을 이용한 광 암호화 시스템)

  • Shin Chang Mok;Kim Soo Joong;Seo Dong Hoan
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.42 no.6
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    • pp.31-38
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    • 2005
  • In this paper, we proposed an optical security system based on a gray-image exclusive-OR encryption using multi-phase separation and phase-wrapping method. For encryption, a gray image is sliced into binary images, which have the same pixel value, and these images are encrypted by modified XOR rules with binary random images. The XORed images and the binary images respectively combined and converted into full phase images, called an encrypted image and a key image. For decryption, when the encrypted image and key image are used as inputs on optical elements, Practically due to limited controllability of phase range in optical elements, the original gray image cannot be efficiently reconstructed by these optical elements. Therefore, by decreasing the phase ranges of the encrypted image and key image using a phase-wrapping method and separating these images into low-level phase images using multi-phase separation, the gray image can be reconstructed by optical elements which have limited control range. The decrytion process is simply implemented by interfering a multiplication result of encrypted image and key image with reference light. The validity of proposed scheme is verified and the effects, which are caused by phase limitation in decryption process, is analyzed by using computer simulations.

Efficient Optical Watermark Using Multiple Phase Wrapping and Real-Valued Functions (다중위상래핑과 실수값 함수를 이용한 효율적인 광 워터마킹)

  • Cho, Kyu-Bo;Seo, Dong-Hoan;Lee, Seung-Hee;Hong, Jae-Keun
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.46 no.3
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    • pp.10-19
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    • 2009
  • In this paper, an efficient optical watermark method using multiple phase wrapping and real-valued decoding key is proposed. In the embedding process, two zero-padded original images placed in two quadrants on input plane are multiplied with two statistically independent random phase patterns and are Fourier transformed, respectively. Two encoded images are obtained by taking the real-valued data from these Fourier transformed images. And then two phase-encoded patterns, used as a hidden image and a decoding key, are generated by the use of multiple phase wrapping from each of the encoded images. A transmitted image is made from the linear superposition of the weighted hidden images and a cover image. In reconstruction process, the mirror reconstructed images can be obtained at all quadrants by the inverse-Fourier transform of the product of the transmitted image and the decoding key. Computer simulation and optical experiment are demonstrated in order to confirm the proposed method.

New Analysis Approach to the Characteristics of Excimer Laser Annealed Polycrystalline Si Thin Film by use of the Angle wrapping (엑시며 레이저에 의해 형성된 다결정 실리콘 박막의 Angle wrapping에 의한 깊이에 따른 특성변화)

  • Lee, Chang-U;Go, Seok-Jung
    • Korean Journal of Materials Research
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    • v.8 no.10
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    • pp.884-889
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    • 1998
  • Amorphous silicon films of large area have been crystallized by a line shape excimer laser beam of one dimensional scanning with a gaussian profile in the scanning direction. In order to characterize the crystalline phase transition of thickness variables in excimer laser annealing(ELA), angle wrapping method was used. And also to characterize the residual stresses of crystalline phase transition in the case of angle wrapped-crystalline silicon on corning 7059 glass, polarized raman spectroscopies were measured at various laser energy density and substrate temperature. The residual stress varies from $9.0{\times}10^9$ to $9.9{\times}10^9$, and from $9.9{\times}10^9$ to $1.2{\times}10^10$dyne/${cm}^2$ of the substrate temperature at room temperature and varies from $8.1{\times}10^9$ to $9.0{\times}10^9$, and from $9.0{\times}10^9$ to $9.9{\times}10^9$dyne/${cm}^2$ of the substrate temperature at $400^{\circ}C$ as a function of direction from surface to substrate. According to the direction from the surface in liquid phase to the interface and from the interface to near the substrate in solid phase of recrystallized Si thin film, respectively. Thus, the stress is increased from(Liquid phase to solid phase) with phase transition.

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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.

Optical Image Hiding Technique using Real-Valued Decoding Key (실수값 복원키를 이용한 광 영상 은닉 기술)

  • Cho, Kyu-Bo;Seo, Dong-Hoan;Choi, Eun-chang
    • IEMEK Journal of Embedded Systems and Applications
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    • v.6 no.3
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    • pp.168-173
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    • 2011
  • In this paper, an optical image hiding technique using real-valued decoding key is proposed. In the embedding process, a each zero-padded original image placed in a quadrants on an input plane is multiplied by a statistically independent random phase pattern and is Fourier transformed. An encoded image is obtained by taking the real-valued data from the Fourier transformed image. And then a phase-encoded pattern, used as a hidden image and a decoding key, is generated by the use of multiple phase wrapping from the encoded images. A transmitted image is made from the linear superposition of the weighted hidden images and a cover image. In reconstruction process, the mirror reconstructed images can be obtained at two quadrants by the inverse-Fourier transform of the product of the transmitted image and the decoding key. Computer simulation and optical experiment are demonstrated in order to confirm the proposed technique.

A Study on Sample Frequency Channel Selection of Near-Field Receiving Measurement for the Active Phased Array Antenna for Mono-Pulse Accuracy (모노펄스 정확도를 위한 능동배열위상레이다의 근접전계 수신시험 표본 주파수 채널 선택에 대한 연구)

  • Kwon, Yong-Wook;Yoon, Jae-Bok;Yoo, Woo-Sung;Jang, Heon-Soon;Kim, Do-Yeol
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.4
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    • pp.318-327
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    • 2017
  • It is essential for the near-field receiving measurement to make beam pattern and check the performance of a active phased array antenna system. Also, we could obtain compensation value for mono-pulse function through the near-field receive test, however, if the radar has many frequency channel, the test would take long time and hard effort. So it is needed that frequency channels are selected for measurement and calculates the values for other frequency channels to improve efficiency in development and manufacture. In this case, the phase variations in sum and del channels would be checked. The phase measurement includes un-linear characteristic because of wrapping effect. Generally, radars have similar path length in sum and del channel, but if a radar has a electrical length gap between sum and del channel, errors could occur by phase's wrapping effect. In this paper, the interpolation method's error caused by electrical length gap is checked and the effective method for frequency channel selection to avoid wrapping effect is introduced.

A field trial of helically wrapping fiber optic cable onto existing 154KV Phase conductor. (전력선을 이용한 광케이블 현장 실증 시험)

  • Shin, Keon-Hak;Lee, Won-Bin;Cho, Hong-Keun
    • Proceedings of the KIEE Conference
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    • pp.143-146
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    • 1987
  • Fiber optics provide a solution to the problems at interference, capacity and reliability in communication. Approximately 20 kilometera of a six-fiber, multimode, longwave($1.3{\mu}m$), graded index silica glass fiber optic cable was helically wrapped around a phase conductor at a Korea Electric Power Corporation(KEPCO) 154KV transmission line. This paper presents an economic comparison of several fiber optic cable installation alternative and discusses the characteristics at the helically wrapped fiber cable, as well as the entire installation, including high voltage phase-to-ground (PTG) end termination, and splicing. The fiber link was installed for the field trial and practical use with overhead composite optical fiber cable which installation performed a few years earlier some other location and is intended to accommodate not only telephone but also supervisory Control and Data Acquisition(SCADA), protective relaying, and telemetry functions.

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Magnetic field Inhomogeneity measurement algorithm using magnetic resonance (자기 공명 영상을 이용한 불균일 자계 측정 알고리즘)

  • Kim, H.J.;Kim, C.Y.;Han, S.Y.;Yoon, J.H.;Ahn, C.B.
    • Proceedings of the KIEE Conference
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    • pp.2809-2811
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    • 1999
  • In this paper, we develope an algorithm to calculate field inhomogeneity in MR imaging using a dual fast spin echo pulse sequence. Because phase modulation time can be easily modified with this pulse sequence, high resolution image can be obtained and acquisition time can be reduced compared to gradient echo technique. In the case of phase wrapping in field map, phase corrected using image processing technique. We assume the field pattern to be second order polynomial and apply Pseudo-Inverse equation to calculate second order polynomial coefficients. These coefficients can be used for the shimming of the magnetic field.

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Performance Comparison of Taylor Series Approximation and CORDIC Algorithm for an Open-Loop Polar Transmitter (Open-Loop Polar Transmitter에 적용 가능한 테일러 급수 근사식과 CORDIC 기법 성능 비교 및 평가)

  • Kim, Sun-Ho;Im, Sung-Bin
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.9
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    • pp.1-8
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    • 2010
  • A digital phase wrapping modulation (DPM) open-loop polar transmitter can be efficiently applied to a wideband orthogonal frequency division multiplexing (OFDM) communication system by converting in-phase and quadrature signals to envelope and phase signals and then employing the signal mapping process. This mapping process is very similar to quantization in a general communication system, and when taking into account the error that appears during mapping process, one can replace the coordinates rotation digital computer (CORDIC) algorithm in the coordinate conversion part with the Taylor series approximation method. In this paper, we investigate the application of the Taylor series approximation to the cartesian to polar coordinate conversion part of a DPM polar transmitter for wideband OFDM systems. The conventional approach relies on the CORDIC algorithm. To achieve efficient application, we perform computer simulation to measure mean square error (MSE) of the both approaches and find the minimum approximation order for the Taylor series approximation compatible to allowable error of the CORDIC algorithm in terms of hardware design. Furthermore, comparing the processing speeds of the both approaches in the implementation with FPGA reveals that the Taylor series approximation with lower order improves the processing speed in the coordinate conversion part.