• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.539-540
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• 2009

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.401-411
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• 2006

We propose an optical encryption/decryption technique for a security system based on 2-step phase-shifting digital holography. Phase-shilling digital holography is used for recording phase and amplitude information on a CCD device. 2-step phase-shifting is implemented by moving the PZT mirror with phase step of 0 or ${\pi}/2$. The binary data and the key are expressed with random code and random phase patterns. The digital hologram is a Fourier transform hologram and is recorded on CCD with 256 gray level quantization. We remove the DC term of the digital hologram fur data reconstruction, which is essential to reconstruct the original binary input data/image. The error evaluation fer the decrypted binary data is analyzed. One of errors is a quantization error in detecting the hologram intensity on CCD, and the other is generated from decrypting the data with the incorrect key. The technique using 2-step phase-shifting holography is more efficient than a 4-step method because 2-step phase-shifting holography system uses less data than the 4-step method for data storage or transmission. The simulation shows that the proposed technique gives good results fur the optical encryption of binary information.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.244-251
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• 2011

We propose a new 2-step phase-shifting digital holographic optical encryption technique and analyze tolerance error for this cipher system. 2-step phase-shifting digital holograms are acquired by moving the PZT mirror with phase step of 0 or ${\pi}$/2 in the reference beam path of the Mach-Zehnder type interferometer. Digital hologram with the encrypted information is Fourier transform hologram and is recorded on CCD camera with 256 gray-level quantized intensities. The decryption performance of binary bit data and image data is analyzed by considering error factors. One of the most important errors is quantization error in detecting the digital hologram intensity on CCD. The more the number of quantization error pixels and the variation of gray-level increase, the more the number of error bits increases for decryption. Computer experiments show the results to be carried out encryption and decryption with the proposed method and the graph to analyze the tolerance of the quantization error in the system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.226-230
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• 2001

Electronic Speckle Pattern Interferometry (ESPI) has been recently developed and widely used because it has advantage to be able to measure surface deformations of engineering components and materials in industrial areas with non-contact. The spekle patterns to be formed with interference phenomena of scattering phenomena measure the out-of-plane deformations, together with the use of digital image equipment to process the informations included in the speckle patterns and the display consequent interferogram on a computer monitor. In this study, the experimental results of a canti-levered plate using ESPI were compared with those obtained from the simple beam theory. The ESPI results of the canti-levered plate analyzed by 4-step phase shifting method are close to the theoretical expectation. Also, out-0of-plane displacements of a spot welded canti-levered plate were measured by ESPI with 4-step phase shifting technique. The phase map of the spot welded canti-levered plate is quite different from that of the canti-levered plate without spot welding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2313-2318
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• 2000

The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. This is time consuming and requires skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting method for the stress analysis of a curved beam plate. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at 0˚, 45˚, 90˚ and 135˚. Experimental results are compared with those of ANSYS and calculated by the simple beam theory. Good agreement among the results can be observed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1534-1541
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• 2003

A new window-based, user-friendly fringe analysis system is developed, especially for analyzing noisy interferograms. The system integrates three major techniques, that is fringe tracking, Phase shifting, and Fourier transform, into a single shell by employing a unified procedure. Since the system is made in a modular fashion and all processing modules can be shared for any technique, a user can select necessary modules and easily edit the applying order of them based on the user's analysis strategy, which should be changed depending on the noise level of the image. The system provides a high-level GUI and a variety of image handling tools and therefore users can easily access the system and produce the optimal results without giving up in the middle of a process even for severely noise-contaminated interferometric images.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.78-83
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• 1999

This study discusses a non-contact optical technique, electronic speckle pattern interformetry(ESPI), that is well suited for in-plane and out-of-plane deformation measurement. However, the existing ESPI methods that are based on dual-exposure, real-time and time-average method have difficulties for accurate measurement of structure, due to irregular intensity and shake of phase. Therefore, phase shifting method has been proposed in order to solve this problem. About the method, the path of reference light in interferometry is shifted and added to least square fitting method to make the improvement in distinction and precision. This proposed method is applied to measure in -plane displacement that is compared with the previous method. Also, Used as specimen AS4/PE따 [30/=30/90]s was analyzed by ESPI based on real-time to determine the characteristics of vibration under no-load and tension. These results are quantitatively compared with those of FEM analysis inmode shapes.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.149-154
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• 2001

This study discusses a non-contact optical technique, electronic speckle pattern interferometry(ESPI), that is well suited for a deformation measurement of structure. Phase shifting method and unwrapping method have used to make deformation quantitative widely. In this paper, a previous numerical formula for phase shifting method is reconstructed in addition to least square fitting method to improve sensitivity and phase unwrapping based on vertical-horizontal scanning method is applied to analyze in-plane and out-of-plane deformation quantitatively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.93-96
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• 2000

This study discusses a non-contact optical technique, phase shifting electronic speckle pattern interferometry, that is well suited for a deformation measurement. However, the phase shifting method has difficulties for determinating a deformation quantitatively beacuse of the characteristics of arctan function. In order to solve this problem, phase unwrapping methods has been studied during the last few years. In this study, using phase unwrapping based on line by line scanning phase shifted fringe patterns are studied to determinate a deformation quantitatively. Also least square fitting method is applied to reduce noise and improve image resolution.

• Journal of KIISE:Software and Applications
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• v.37 no.6
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• pp.417-429
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• 2010

Reversible watermarking inserts watermark into digital media in such a way that visual transparency is preserved and then enables to restore the original media from the marked one without any loss of media quality. This watermarking can be applied to quality-sensitive imaging such as medical imaging, military imaging, remote-sensing imaging, and precious artwork, where the original media should be preserved during image processing and analysis. In this paper, a reversible image watermarking technique that embeds message bits by modifying the differential histogram of adjacent pixels is presented. In order to satisfy both high embedding capacity and visual quality, the proposed technique exploits the fact that adjacent pixels in the image have highly spatial correlation. Also, we prevent overflow/underflow problem and salt-and-pepper artifacts by employing a predicted error compensation scheme. Through experiments using various test images, we prove that the presented technique provides perfect reversibility and high embedding capacity, while maintaining the induced-distortion low.