• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.312-315
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• 2000

In this study, we have investigated the holography recording and reconstruction of the polarization state in chalcogenide $A_{s40}Ge_{10}Se_{15}S_{35}4 thin films using a He-Ne laser light(633nm). The thickness of thin films is a 8677${\AA}$ and 9093${\AA}$. A He-Ne laser used to probe and record of the grating. Also the polarization state of object beam modulated with a $\lambda/4$ wave plate. The polarization state of the +lst order diffracted beam generated by readout of the grating with a linearly polarized reference beam. It was the same-handed polarization state as the polarization state of the recording beam. The diffraction efficiency of circularly polarized recording represented higher than other polarization state.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.820-823
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• 2000

In this study, we have investigated the holography recording and reconstruction of the polarization state in chalcogenide $As_{40}$$Ge_{10}$$Se_{15}$$S_{35}$ thin films using a He-Ne laser light(633nm). The thickness of thin films is a 8677${\AA}$ and 9093${\AA}$. A He-Ne laser used to probe and record of the grating. Also the, polarization state of object beam modulated with a $\lambda/4$ wave plate. The polarization state of the +1st order diffracted beam generated by readout of the grating with a linearly polarized reference beam. It was the same-handed polarization state as the polarization state of the recording beam. The diffraction efficiency of circularly polarized recording represented higher than other polarization state.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.246-246
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• 2010

In this paper, we investigated the diffraction grating efficiency on AsSeS and Ag-doped amorphous chalcogenide Ag/AsSeS thin film for used to volume hologram. The Chalcogenide film thickness was 0.5um and Ag thin film was varied from 10nm and 20nm. Diffraction efficiency was obtained from (P:P) polarized Diode Pumped Solid State laser(DPSS, 532.0nm: 200mW) beam on AsSeS and Ag/AsSeS thin films. As a results, diffraction grating was not formed at AsSeS thin film but at Ag-doped AsSeS thin film, diffraction grating was formed well compare with the former.

• Korean Journal of Optics and Photonics
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• v.20 no.2
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• pp.76-80
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• 2009

Finger-print recognition is achieved by comparing an input finger-print image with the stored images in the computer, and finally by determining agreement or disagreement. Encryption and decryption are necessary in the finger-print recognition process. In these process CGH (Computer Generated Hologram) is used, and finger-print images reconstructed from the CGHs are compared. In this paper, two methods of recognition are used, one is to compare the finger-print images of each other reconstructed from their CGHs and the other is to compare the CGHs to each other directly, to analyze the differences of finger-print recognition capability between these two methods. Experimental results show that the capability of finger-print recognition for comparing the CGHs of the two is about 150 times higher than in case of comparing the reconstructed finger-print images. Especially the changes of characteristics according to modulation types of CGH are analyzed.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.227-232
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• 1999

We have been making researches on 3-D displays using computer-generated holograms(CGHs). Our CGHs are binary Fresnel holograms that reconstruct point light sources and are recorded by using high resolution laser printers (image setters). We use an image setter with a resolution of 5080 dots per inch. It is possible to reconstruct CGHs with light-emitting points. As the resolution of the image setter is not so high, it is better to use a spherical wave as a reference beam. We considered the recordable points objects are restricted by the low resolution, and proposed the multiplex type hologram to reduce the number of point objects recorded in the unit area of the CGH. We proposed a method to make computer-generated color hologram which could reconstruct color point light sources, by combining RGB color filters with the stripe CGHs corresponding to each color. We considered two kinds of gradation method on our binary CGHs. In this paper, we propose a multiple reconstruction method for improving the narrow viewing field.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.388-390
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• 1994

We are familiar with the holography in these days. For making holography the coherent sources like LASER are used in many fields. But coherent holography has many problems. Coherent holography needs many instrument for practical use like 3-D TV case. In solving the problem we use the non-coherent source. Nowadays many methods like conoscopic holo graphy using anisotropic crystal, shadow casting and interferometric systems are suggested. In this paper we make the hologram using the triangular interferometric systems. [1],[2],[3],[4]. We explain the afocal and double-afocal system which consists of the triangular interferometric system. The holography made in one point and two point cases is imaged on CCD camera and we handle the image data digitally for the reconstruction efficiently. In reconstructing the hologram the Fraunhofer diffraction theory is used. We adopt the rectangular aperture for the convenience of calculation. In the future we must reconstruct the perfect 3-Dimensional object by optical method. For this, we have many problems like resolution problem. We must solve these problem for perfect reconstruction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.285-291
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• 1986

The plane speaker is inspected by the free vibration theory, the sound pressure, and the holographic interferometry. It is shown that time-average holographic interferometry is useful for the vibration analysis of the plane speaker. The position of supporter dertermined experimentally and theoretically, the value of r/a, is 0.68. Theoretical analysis of the free vibration for the plate agrees pretty well with the experimental results. The plane speaker is distorted vibrationally by the suppoter, but the distortion is not seen in the newly designed speaker.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.142-143
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• 2002

KIST에서는 Pulsed Laser를 사용하여 3차원 image를 재생할 수 있는 Electro-Holographic System을 만들어 CGH이미지를 구현하였다. CGH 이미지를 구현하기 위한 SLM (Spatial Light Modulator)으로 TeO$_2$ 결정의 Shear Mode 에서 동작하는 Bragg type의 다채널 AOSLM(Acousto-optic Spatial Light Modulator)이 사용되었다. 이 Bragg type 다채널 AOSLM에서는 광원이 특정 Bragg 각도로 입사하였을 때 다른 고위 차수는 억압되고 ＋나 -의 첫번째 차수의 회절 빔만이 형성된다. (중략)

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.408-414
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• 2001

The structural characteristics of the stiffened double cylinder was investigated through experiment and analysis. The outside cylinder was excited with piezoelectric actuator and the mode shape of the cylinder with stiffening T frame was obtained by using holographic interferometry. Finite element method was applied for further modal investigation of the stiffened cylinder. The experimental results showed that the mode shape of cylinder was dependent on the exciting frequencies and the T frame showed salient effect of damping at most of the resonent frequencies. In particular frequencies, the T frame worked as a transmitter. FFM showed similar results with the experiments. This paper showed that the laser-based method such as holographic interferometry is well suited for investigation of the whole-field mode shapes and FEM has good performance to estimate the medal characteristics of the mechanical structure.