• Journal of Conservation Science
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• v.3 no.1 s.3
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• pp.3-12
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• 1994

As a result of the great attention to the historical and cultural heritage, the achievements of the natural sciences are finding their way into museums. The necessity of preserving the treasures of the artistic and cultural heritage has brought into being a new alliance, an alliance between science and culture. The most sciences of cultural properties pertain mainly to improvement of the methods of identifications, preservation and restoration of historical monuments. Recently a new physical method has appeared that, in a sense, possesses universal capabilities. That method is holography, which successfully combines unique features making it possible not only to create three-dimesional optical replicas of real three -dimensional objects practically indistinguishable from the original but also to study them. We shall deal in this papper with its scientific principle and application for displaying, as well as on other potential applications.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.22-28
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• 2015

We propose a new method for improving the phase contrast of a multiphase digital holographic microscope using a spatial light modulator (SLM). Using the SLM as the annulus, our method improves the light contrast of the object edge to achieve higher accuracy. We demonstrate a digital holographic microscopy technique that provides a 30% improvement in the phase contrast compared to conventional microscopy, which utilizes a mechanical annulus. The phase-contrast improvement allows the 3D reconstructed hologram to be determined more precisely.

• Journal of ILASS-Korea
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• v.15 no.2
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• pp.53-60
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• 2010

This study presents development of digital particle holographic system and its application to spray field to measure three-dimensional velocities and sizes of spray droplets. A double exposure hologram recording system with synchronization system for time control was established and digital holograms can be recorded in a short time interval. To process recorded holograms, the correlation coefficient method was used for focal plane determination of particles. To remove noises and improve the quality of holograms and reconstructed images, the Wiener filter was adopted. The two-threshold and image segmentation methods were used in binary image transformation. For particle pairing, the match probability method was adopted. The developed system was applied to spray field and three-dimensional velocities and sizes of spray droplets were measured. The measurement results of digital holographic system were compared with those made by laser instruments, PDPA(Phase Doppler Particle Analyzer), which proved the feasibility of in-line digital particle holographic system as a good measurement tool for spray droplets.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.451-462
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• 2003

At the paper the method of 3D holographic moving image reconstruction is discused. The main idea of this method is based on the substitution of optically created static hologram by equal diffraction array created by acoustical (AO) field which formed by bulk sound waves. Such sound field can be considered as dynamic optical hologram, which is electrically controlled. At the certain moment of time when the whole hologram already formed, the reference optical beam illuminates it, and due to acoustooptical interaction the original optical image is reconstructed. As the acoustically created dynamic optical hologram is electronically controlled, it can be used for moving 3-dimentional scene reconstruction in real time. The architecture of holographic display for moving scene reconstruction is presented at this paper. The calculated variant of such display laboratory model is. given and discussed. The mathematical simulation of step by step images recording and reconstruction is given. The pictures of calculated reconstructed images are presented. The prospects, application areas, shortcomings and main problems are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1197-1202
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• 2001

Near-field acoustic holography is a powerful tool to visualize sound sources. This method requires pressure measurement at many points for a good hologram. Thus one has to measure carefully so that errors due to the uncertainty of position, sensor mismatch, and so on are reduced. A method to solve this problem is to use a well-designed measurement system. This paper introduces a sound visualization system at center for noise and vibration control (NOVIC), KAIST, and addresses the advantages in terms of the error reduction. The system consists of array microphones, array jigs, a system to control the position and the velocity of the jigs, a data acquisition system, and a monitoring system. This paper also shows some sound visualization results when the system is applied to a speaker and a computer. The results verifies that the sound visualization system is useful for identifying sound sources.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.2
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• pp.65-71
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• 1992

In most absorption machines, absorption enhancement has been achieved by adding small amount of surfactant additive, which introduced the surface tension difference between absorbent and surfactant droplets in the vapor absorption. The aim of this study is to understand a basic mechanism of Marangoni convection and its effectiveness in the vapor absorption enhancement. In this study, nonflowing aqueous solution of LiBr 60 mass% was exposed to saturated water vapor under the condition that two dropwises surfactant were fixed on the absorbent surface. Our experiments achieved to visualize the enhanced heat and mass transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also, Marangoni convection behavior was obtained by using tracer method.

• Journal of Welding and Joining
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• v.17 no.1
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• pp.71-76
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• 1999

The real-time holographic interferometer with digital high-speed camera is applied to the experimental study of laser induced plasma/plume in pulsed Nd:YAG laser welding. A pulsed Nd:YAG laser with 1.2 kW average power is applied to generate laser induced plume. The recording speed of the high-speed camera is 3,000 f/s. The high speed photographs of weld plume without another visualization method, are compared with the visualization photographs with holographic interferometer. The radiation intensity from the laser induced plume is recorded by the high speed photographs, which fluctuated during laser radiation and disappeared after laser end. The density distribution of the plume is recorded by the holographic visualization method. The experimental results show the process of generation of the laser induced plasma/plume, and give the feasibility of quantitative measurement of laser induced plume in laser welding.

• Journal of Information Display
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• v.4 no.3
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• pp.29-34
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• 2003

At the paper the method of 3D holographic moving image reconstruction is discused. The main idea of this method is based on the substitution of optically created static hologram by equal diffraction array created by acoustical (AO) field which formed by bulk sound waves. Such sound field can be considered as dynamic optical hologram, which is electrically controlled. At the certain moment of time when the whole hologram already formed, the reference optical beam illuminates it, and due to acoustooptical interaction the original optical image is reconstructed. As the acoustically created dynamic optical hologram is electronically controlled, it can be used for moving 3-dimentional scene reconstruction in real time. The architecture of holographic display for moving scene reconstruction is presented at this paper. The calculated variant of such display laboratory model is given and discussed. The mathematical simulation of step by step images recording and reconstruction is given. The pictures of calculated reconstructed images are presented. The prospects, application areas, shortcomings and main problems are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.411-418
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• 1992

본 연구에서는 인장하중을 받는 균열이 없는 박판 시험편과 45˚경사균열시험 편의 고유진동수 측정을 위하여 레이저 홀로그래피법을 이용하여 진동모드 측정을 하 여 그 결과를 비교분석하는 실험방법을 택하였으며, 균열이 없는 박판에 대해서만 무 차원하중의 증가에 따른 고유 진동수의 변화관계를 실험치와 Ritz Method에 의한 유한 요소 해석치와 비교하였다.

• Current Optics and Photonics
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• v.5 no.2
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• pp.155-163
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• 2021

We propose a novel optical encryption scheme for cipher-feedback-block (CFB) mode, capable of encrypting two-dimensional (2D) page data with the use of two-step phase-shifting digital interferometry utilizing orthogonal polarization, in which the CFB algorithm is modified into an optical method to enhance security. The encryption is performed in the Fourier domain to record interferograms on charge-coupled devices (CCD)s with 256 quantized gray levels. A page of plaintext is encrypted into digital interferograms of ciphertexts, which are transmitted over a digital information network and then can be decrypted by digital computation according to the given CFB algorithm. The encryption key used in the decryption procedure and the plaintext are reconstructed by dual phase-shifting interferometry, providing high security in the cryptosystem. Also, each plaintext is sequentially encrypted using different encryption keys. The random-phase mask attached to the plaintext provides resistance against possible attacks. The feasibility and reliability of the proposed CFB method are verified and analyzed with numerical simulations.