• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.53-58
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• 1999

Even I the Electronic Speckle Pattern Interferometry(ESPI) method that measure the strain of object within wavelength of light is less visibility than Holographic Interferometry(HI) method, the merits of application, convenience and time-save have made the method practical in industry. However, the existing ESPI methods that are based on dual-exposure, real-time and time-average method have difficulties for accurate measurement, due to irregular intensity and shake of phase. Recently, in order to solve this problem, phase shifting method have been proposed. In this method, the path of reference light in interference is shifted to make improvement in distinction and precision. But this method includes too many noise, caused by the problem of relationship between object and phase. Therefore, a method to reduce noise muse be introduced. In this paper, least square fitting method is proposed. As results, the phase-map is influenced by precise phase shifting and current of notes and speckle pattern obtained by phase shifting method is improved on the existing method driven from time-average method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.586-586
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• 2012

The vuv spectrometer for ITER main plasma measurement is designed as a five-channel spectral system. To develop and verify the design, a two-channel prototype system was fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. For test of the prototype system, a hollow cathode lamp is used as a light source. The system is composed of a collimating mirror to collect the light from source to slit, and two holographic diffraction gratings with toroidal geometry to diffract and also to collimate the light from the common slit to detectors. The overall system performance was verified by comparing the measured spectral resolutions with the calculated spectral resolutions. And we also have developed liquid jet target system. This study is about a neutron generator, which is designed to overcome many of the limitations of traditional beam-target neutron generators by utilizing a liquid target. One of the most critical aspects of the beam-target neutron generator is the target integrity under the beam exposure. A liquid target can be a good solution to overcome damage to the target such as target erosion and depletion of hydrogen isotopes in the active layer, especially for the ones operating at high neutron fluxes and maintained relatively thin with no need for water cooling. In this study, liquid target containing hydrogen has been developed and tested.

• Journal of Information Display
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• v.11 no.2
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• pp.76-83
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• 2010

This paper presents the multi-user autostereoscopic 3D display system constructed and operated by the authors using the time-multiplexing approach. This prototype has three main advantages over the previous versions developed by the authors: its hardware was simplified as only one optical array is used to create viewing regions in space, a lenticular multiplexing screen is not necessary as images can be produced sequentially on a fast 120Hz LCD with full resolution, and the holographic projector was replaced with a high-frame-rate digital micromirror device (DMD) projector. The whole system in this prototype consists of four major parts: a 120Hz high-frame-rate DMD projector, a 49-element optical array, a 120Hz screen assembly, and a multi-user head tracker. The display images for the left/right eyes are produced alternatively on a 120Hz direct-view LCD and are synchronized with the output of the projector, which acts as a backlight of the LCD. The novel steering optics controlled by the multiuser head tracker system directs the projector output to regions referred to as exit pupils, which are located in the viewers’eyes. The display can be developed in the "hang-on-the-wall"form.

• Korean Journal of Optics and Photonics
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• v.9 no.6
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• pp.385-389
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• 1998

In this paper, we propose an optical correlator system using volume holograms for database of matched filters. Optical correlator has high speed and parallel processing characteristics of optics. Matched filters are recorded into a volume hologram that can store data with high density, transfer them with high speed, and select a randomly chosen data element. The multiple reference images of database are prerecorded in a photorefractive crystal in the form of Fourier transform images, simply by passing the image displayed in a spatial light modulator through a Fourier transform lens. The angular multiplexing method for multiple holograms of database can be achieved by rotating the crystal by use of a step motor. Experimental results show that the proposed system can be used for the fingerprint recognition.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.131-138
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• 2011

We fabricated distributed feedback InGaAsP/InP laser diodes for optical fiber communication module and characterized the lasing properties in continuous wave operation. The active layer of 7-period InGaAsP(1.127 eV)/InGaAsP(0.954 eV) multi-quantum well structure was grown by the metal-organic chemical vapor deposition. The grating for waveguide was also fabricated by the implementation of the Mach-Zehender holographic method of two laser beams interference of He- Cd laser and the fabricated laser diode has the dimension of the laser length of $400{\mu}m$ and the ridge width of $1.2{\mu}m$. The laser diode shows the threshold current of 3.59 mA, the threshold voltage of 1.059 V. For the room-temperature operation with the current of 13.54 mA and the voltage of 1.12 V, the peak wavelength is about 1309.70 nm and optical power is 13.254 mW.

• Korean Journal of Agricultural Science
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• v.35 no.1
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• pp.33-40
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• 2008

The structural characteristics that influence on the fungicidal activities of N-phenylbenzenesulfonamide (1~24) and N-phenyltheinylsulfonamide (25~30) derivatives against Dampping-off (Pythium ultimum) were discussed quantitatively using the models of molecular holographic quantitative structure-activity relationships (HQSAR). From the based on these findings, the statistical results of the optimized HQSAR F-3 model showed better predictablity ($r^2_{cv.}$ or $q^2=0.581$) and correlation coefficient ($r^2_{ncv.}=0.963$). And, from the analytical results of the atomic contribution maps on the fungicidal activities, the most active compound is $R_1=2-fluoro-4-chloro$ substituent (4) and the most inactive one is $R_1=4-methoxy$ substituent (20). It was found that the 2-fluoro-4-chlorophenyl group as a $R_1$-group was an important structure and a characteristic factor not only for herbicidal activity but also for fungicidal activity.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.1
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• pp.151-163
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• 2013

Recently the attention on digital hologram that is regarded as to be the final goal of the 3-dimensional video technology has been increased. Digital hologram is calculated by modeling the interference phenomenon between an object wave and a reference wave. The modeling for digital holograms is called by computer generated hologram (CGH) Generally, CGH requires a very large amount of calculation. So if holograms are generated in real time, high-speed method should be needed. In this paper, we analyzed CGH equation, optimized it for mapping general purpose graphic processing unit (GPGPU), and proposed a optimized CGH calculation technique for GPGPU by resource allocation and various experiments which include block size changing, memory selection, and hologram tiling. The implemented results showed that a digital hologram that has $1,024{\times}1,024$ resolution can be generated during approximately 24ms, using 1K point clouds. In the experiment, we used two GTX 580 GPGPU of nVidia Inc.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.189-195
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• 2006

Bragg detuning effect if, one of the serious problems if the photopolymer is used for the recording material of holography memories. And the critical reasons of that are known as the bulk refractive index change and shrinkage of recording material. However, the trials for analyzing the effect are mainly on the K-sphere and biased on the transmission hologram. So, we approached Bragg detuning effect numerically and applied the method to the transmission holograms and the reflection holograms all together. We simulated it with MATLAB. As a result, the bulk refractive index change causes+Bragg detuning effect on the transmission holograms and the reflection holograms. But the shrinkage leads to+Bragg detuning effect on the transmission hologram and-Bragg detuning effect on the reflective hologram. Compared to experimental result, the bulk refractive index change(${\fallingdotseq}4{\times}10^{-4}$) and the ratio of shrinkage to the thickness of the material(${\fallingdotseq}1.67{\times}10^{-3}$) could be matched with Bragg detuning effect on the transmission hologram and the reflection hologram.

• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.23-27
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• 2007

Blu-ray disc 이후의 차세대 고밀도 광 기록 기술로 주목받는 홀로그래픽 데이터 스토리지 시스템을 설계, 제작하고 기록 재생 test 를 수행하였다. 시스템은 각도 다중화법을 채택하였고, 파장 405nm, NA 0.55 신호광 Fourier 변환 렌즈로 미디어에 defocus 하여 기록하였다. 1 page 용량은 raw bit 로 0.74Mbit 이고, SLM 과 CCD 의 over-sampling 비율은 1:1.5 가 되도록 구성하였다. 얻어진 raw 이미지는 위치 및 distortion 보상등의 신호처리 후, 70page 다중화 조건에서 bER $1{\times}10-2$ 수준으로 재생해 낼 수 있었다. 온도 변화에 의한 신호 열화를 보상하기 위해 External Cavity Tunable Blue LD 를 개발하여 온도 변화 $10^{\circ}C$까지 보상 가능함을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.48-56
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• 2000

Effects of the correlated random fluctuation in each grating half-period have been studied by an effective index transfer matrix method in quarter wavelength shifted DFB lasers. As the correlation coefficient changes from 0 to -1, single mode stability and wavelength accuracy are less degraded by the reduced error in the grating period. This fact shows that holographic grating fabrication is better than electron-beam lithography in discrete device fabrication provided that the magnitude of the random fluctuation is the same.