• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.447-448
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• 2008

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.157-164
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• 2011

This work is devoted to the technique application of lock-in infrared Thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.3
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• pp.124-131
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• 2007

Aspheric glass lenses was fabricated by glass molding press(GMP), which is a plano-aspheric convox shape and intended for use as an optical design of 3 megapixel and 2.5 magnifications zoom in a camera phone module. Transcription ratio of form accuracy (PV) as well as resolution properties was measured for evaluation the molded lens. Form accuracy (PV) of the mold surface was $0.127\;{\mu}m$ in an aspheric and $0.168\;{\mu}m$ in a plano, in case of the molded lens it shows $0.205\;{\mu}m$ and $0.223\;{\mu}m$, respectively. Resolution of the molded lens was measured as a MTF[Contrast]. The molded lens shows contrast of 32.9% at 80 1p/mm and the value is similar with contrast of 33% obtained simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.862-869
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• 2000

In a switch routing system, buffers are indispensible to prevent signal collision during routing process. For a photonic switching system, optical buffers are also indispensible if the system requires an active routing rather than a simple optical cross-connect(OXC). To cope with WDM technologies in optical comminication systems in these days, photonic switching system also has to deal with WDM signals. Therefore, optical buffers needed in a switching system has to be routed to the same output. For the receiver to recognize these signals separately, parallel WDM signals during rearrangement process. In this paper, we propose a novel all optical WDM output buffer whose structure, hardware, SNR and BER characteristics are improved a lot comparing with those of previously reported ones. From the analysis of the proposed buffer, the new buffer can hold 255 WDM cells keeping BER of 10-9 as long as a contrast ratio(gain on-off ratio) of optical gate(semiconductor optical amplifier) nside the buffer is 30dB.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1567-1572
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• 2004

Although accurate measurement of velocity profiles, multiple velocity vectors, and shear stress in arteries is important, there is still no easy method to obtain such information in vivo. This study shows the utility of combining ultrasound contrast imaging with particle image velocimetry (PIV) for non-invasive measurement of velocity vectors. The steady flow analytical solution and optical PIV measurements (for pulsatile flow) were used for comparison. When compared to the analytical solution, both echo PIV and optical PIV resolved the steady velocity profile well. Error in shear rate as measured by echo PIV (8%) was comparable to the error of optical PIV (6.5%). In pulsatile flow, echo PIV velocity profiles agreed well with optical PIV profiles. Echo PIV followed the general profile of pulsatile shear stress across the artery but underestimated wall shear at certain time points. These studies indicate that echo PIV is a promising technique for the non-invasive measurement of velocity profiles and shear stress.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.26-31
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• 2005

We describe the design and the implementation of video-rate reflection confocal scanning microscopy (CSM) using an acousto-optical deflector (AOD) for the fast horizontal scan and a galvanometer mirror (GM) for the slow vertical scan. Design parameters of the optical system are determined for optimal resolution and contrast. The OSLO simulations show that the performances of CSM are not changed with deflection angle and the wavefront errors of the system are less than 0.012λ. To evaluate the performances of designed CSM, we do a series of tests, measuring lateral and axial resolution, real time image acquisition. Due to a higher axial resolution compared with conventional microscopy, CSM can detect the surface of sub-micrometer features. We detect 138㎚ line shape pattern with a video-rate (30 frm/sec). And 10㎚ axial resolution is archived. The lateral resolution of the topographic images will be further enhanced by differential confocal microscopy (DCM) method and computational algorithms.

• Journal of the Optical Society of Korea
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• v.14 no.2
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• pp.137-141
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• 2010

We report, for the first time to our knowledge, observation of polarization bistability from 1.55-${\mu}m$ wavelength single-mode VCSELs of a conventional cylinder-shape under control of their driving current, and demonstration of all-optical flip-flop (AOFF) operations based on the bistability with optical set and reset pulse injection at a 50 MHz switching frequency. The injection pulse energy was less than 14 fJ. The average on-off contrast ratio of the flip-flopped signals was about 7 dB. These properties of the VCSELs will be potentially useful for future high-speed all-optical signal processing applications.

• Current Optics and Photonics
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• v.8 no.4
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• pp.327-344
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• 2024

Optical phantoms are essential in optical imaging and measurement instruments for performance evaluation, calibration, and quality control. They enable precise measurement of image resolution, accuracy, sensitivity, and contrast, which are crucial for both research and clinical diagnostics. This paper reviews the recent advancements and challenges in phantoms for optical coherence tomography, photoacoustic imaging, digital holographic microscopy, optical diffraction tomography, and oximetry tools. We explore the fundamental principles of each technology, the key factors in phantom development, and the evaluation criteria. Additionally, we discuss the application of phantoms used for enhancing optical-image quality. This investigation includes the development of realistic biological and clinical tissue-mimicking phantoms, emphasizing their role in improving the accuracy and reliability of optical imaging and measurement instruments in biomedical and clinical research.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.8
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• pp.59-65
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• 2004

In this paper, we propose Pseudo-TN IPS mde(Pseudo-Twisted Nematic In-Plane Switching mode) based on IT(In-plane switching Twisted nematic) mode that increase contrast ratio from improving optical characteristics and analyze the characteristics of Pseudo-TN IPS uude. Optical transmittance is 25% higher for the PTN-IPS mode than for the IT mode. Because aperture ratio of the PIN-IPS is increased. And the control of Liquid Crystal for adjusting optical transmittance is more easier than IT mode, because optical transmittance variation is linear with applying voltage. Contrast ratio is 8% lower for the PTN-IPS mode than for the IT mode in the horizontal direction. But, Contrast ratio is 20% higher for the PTN-IPS mode than for the IT mode in the vertical direction. It has also cell gap margin and many benefits of IT mode, this may be used very well in the future LC Cell design.

• The Optical Journal
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• s.98
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• pp.60-66
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• 2005

프로젝터와 프로젝션 TV는 공통적으로 광학엔진내에 신호 처리된 영상 정보를 표시해주는 CRT(Cathode Ray Tube), LCD(Liquid Crystal Device), LCoS(Liquid Crystal on Silicon), 디지털 마이크로 미러 디바이스(Digital Micromirror Device;DMD)등의 디스플레이 소자가 사용된다. 최근 이러한 디스플레이 소자는 소형화·경량화 되어지는 추세에 있으며 무겁고 두꺼운 CRT보다는 LCD를 이용한 프로젝션 시스템들이 속속 출시되고 있다. LCoS 및 DMD를 이용한 시스템들도 출시 또는 개발되고 있는 실정이다. 특히, 현재까지는 LCD가 주류였지만, 고해상도 구현에 유리한 반면, 개발속도가 느린 LCoS에 비해 하이 콘트라스트(High Contrast) 구현에 탁월하고 개발 속도가 빠른 DMD를 이용한 프로젝션 시스템의 개발 및 출시가 주로 진행되고 있다.