• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.263-267
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• 2006

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene (PVDF-TrFE). The large difference of coefficient of thermal expansion (CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a significant deflection with relatively small temperature rise. Compared to the most conventional micro actuators based on MEMS (micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. Additionally, we can achieve response time of 14.6 ms, resonance frequency of 12 Hz, and reliability ability of $10^5$ cycles. The proposed actuator can find applications where a large vertical displacement is needed while maintaining compact overall device size, such as a micro zooming lens, micro mirror, micro valve and optical application.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.691-693
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• 2005

The prototype of the radiometric calibration algorithm, including the correction of scan mirror's angle, has been developed for the stationary meteorological sensor, firstly in Korea. We use this system on GOES-12 to evaluate two coefficients, slope and intercept. The evaluated coefficients show good agreement with the NESDIS's results for the five-case data. The calculated coefficients have been applied to the conversion from the measured counts to the radiance and the converting methods according to the scanning are investigated to enhance the radiometric accuracy.

• 한국기계가공학회지
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• 제2권3호
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• pp.56-61
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• 2003

This paper described about on-machine profile measurement of aspheric surfaces using contact probing technique in ultra precision machine. A contact probe has been designed as a sensing device to obtain measuring resolutions in nanometer regime using a circle leaf spring mechanism and a capacitive-type sensor. The contact probe which is installed on the z-axis is In touch with the aspheric objects which is fixed on the spindle of the diamond turning machine(DTM) during the measuring procedure. The x, z-axis motions of the machine are monitored by a set of two orthogonal plane mirror type laser interferometers. As a results, the developed contact probe on-machine measurement system showed 10 nanometers repeatability with a ${\pm}2{\sigma}$ and uncertainty of 200 nmPv.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.90-93
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• 2003

This paper described about the ultra-precision profile measurement of aspheric surfaces using contact probing technique. A contact probe has been designed as a sensing device to obtain measuring resolutions in nanometer regime utilizing a circle leaf spring mechanism and a capacitive-type sensor. The, contact probe is attached on the z-axis during measurement while aspheric object are supported on the diamond turning machine(DTM). The machine xz-axis motions are monitored by a set of two orthogonal plane mirror type laser interferometers. Experimental results show that the contact probing technique developed of on-machine measurement system in this investigation is capable of providing a repeatability of 10 nanometers with a $\pm$20 uncertainty of 200nmPv.

• 대한기계학회논문집
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• 제18권10호
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• pp.2779-2786
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• 1994

This study presents an experimental investigation of the effect of the wake on mass transfer about a circular cylinder in crossflow. The flat-plate wake was generated by merging two mirror images of turbulent boundary layers that were well developed along the both sides of flat plate with a sharp trailing edge. The velocity field was measured by a hot-wire system and the mass transfer rate by a naphthalene sublimation method. The mixing and developing stages of the wake were addressed to identify flow conditions. The mass transfer effects of different developing stages of the wake was discussed in detail. It is noted that a local maximum appears not at the front stagnation point but at a point a little downstream when the cylinder is located in the nearwake region and much more elevated mass transfer rate is obtained compared to effect of free-stream turbulence.

• Journal of the Optical Society of Korea
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• 제15권2호
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• pp.111-117
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• 2011

Full-range spectral domain optical coherence tomography (SD-OCT) with a 1-${\mu}m$ band light source is shown here. The phase of the reference beam is continuously stepped while the probing beam scans the sample laterally (B-scan). The two dimensional spectral interferogram obtained is processed by a Fourier transform method to obtain a complex spectrum leading to a full-range OCT image. A detailed mathematical explanation of the complex conjugate resolving method utilized is provided. The system's measurement speed was 7.96 kHz, the measured axial resolution was $9.6{\mu}m$ in air and the maximum sensitivity 99.4 dB. To demonstrate the effect of mirror image elimination, In vivo human eye pathology was measured.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.146-151
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• 2009

A Gaussian beam of single mode fiber laser was changed into a ring-shaped pattern after it was transmitted through the hollow optical fiber. The ring-shaped beam was focused on a plane by an f-. lens and it was scanned by a Galvano-mirror. The spatial profile of laser energy incident on a plane had two peaks at both sides of the scanned linear track. The profile was compared with the result obtained when the Gaussian beam was dithered transversely by an acousto-optic modulator. It is found that hollow optical fiber beam shaper can replace acousto-optic beam dithering device which is employed in a laser induced thermal printing system.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.263-269
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• 2012

In this paper, we propose a new dual optical encryption method for binary data and secret key based on 2-step phase-shifting digital holography for a cryptographic system. Schematically, the proposed optical setup contains two Mach-Zehnder type interferometers. The inner interferometer is used for encrypting the secret key with the common key, while the outer interferometer is used for encrypting the binary data with the same secret key. 2-step phase-shifting digital holograms, which result in the encrypted data, 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. The digital hologram with the encrypted information is a Fourier transform hologram and is recorded on CCD with 256 gray level quantized intensities. Computer experiments show the results to be encryption and decryption carried out with the proposed method. The decryption of binary secret key image and data image is performed successfully.

• 한국진공학회지
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• 제4권S2호
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• pp.156-162
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• 1995

For a stimulating neural electrode, the charge density should be as large as possible to provide adequate stimulation of the nervous system while allowing for miniaturization of the electrode. Since iridium oxide is able to produce high charge densities while preventing undesirable reactions due to charge storage, it has become a promising material for neural prostheses. Successful production of stable Ir and Ir oxide films on various substrates now limits the use of this material. Ir was deposited on two differently prepared surface of (mirror finish, passivation) surgical Ti-6AI-4V with several methods. Ion beam mixing of sputter deposited Ir films on passivated Ti-6AI-4V produced stable and good adherent Ir films. It was found that the increase in charge density of pure Ir on continuous cyclingis due to the accumulation of the oxide phase ( associated with a large surface area) in which the valence state of iridium changes and the double-layer capacitance increases. This study also showed that the double layer capacitance is equally or even more responsible for the high charge density of anodically formed Ir oxide.

• 대한전자공학회논문지SD
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• 제45권8호
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• pp.17-23
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• 2008

본 연구에서는 InP 물질의 능동과 수동 광도파로를 포함하는 신개념의 직사각형 링 레이저를 제작하여 그 특성을 측정하고 분석하였다. 직사각형 링 레이저의 구성은 작은 광 손실을 갖는 네 개의 전반사 미러와 세 개의 수동 광도파로로 구성된 방향성 결합기로 되어 있다. 제작된 두 개의 서로 다른 직사각형 링 공진기의 능동 영역의 길이는 250과 $350{\mu}m$이고, 전체 공진기 길이는 각각 580과 $780{\mu}m$이다. 측정된 링 레이저의 문턱 전류는 상온에서 연속 전류를 인가했을 때 38 mA를 얻을 수 있었다. 이때 20 dB 이상의 인접모드 억압비를 갖는 단일 모드 발진 특성을 확인하였다.