• Journal of the Optical Society of Korea
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• 제7권3호
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• pp.150-155
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• 2003

Femtosecond laser ablation mechanism was systematically investigated on sodalime glass in ambient conditions. The ablation crater diameter was measured for varying numbers of laser pulses as for varying well as the laser fluence. The analysis of the results with a one dimensional spatial Gaussian fluence distribution reveals that the inherent ablation mechanism has been altered from a multi-photon process to a single photon excitation due to defect sites that have been accumulated by successive laser pulses. Furthermore, the transition between the two regimes was found to be a function of both the laser fluence and the number of laser shots.

• 한국정밀공학회지
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• 제17권6호
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• pp.7-16
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• 2000

정밀공학에서 측정은 필수적인 의미를 갖는다. 측정할 수 없는 제품 치수는 체계적인 가공이 불가능하며, 이는 설사 가공자의 특수한 기능에 의해 가공이 되더라도 체계적인 양산방식에 의한 생산이 될 수 없음을 의미한다. 이러한 중요성을 갖는 측정기술은 가공기술의 발랄과 더불어 꾸준한 진보를 이루어 왔다.(중략)

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.64-65
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• 2009

• Current Optics and Photonics
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• 제7권4호
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• pp.419-427
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• 2023

The structural design of an optical-telescope assembly (OTA) for satellite laser ranging (SLR) is conducted in two steps. First, the results of a parametric study of the major design variables (e.g. dimension and shape) of the OTA part are explained, and the detailed structural design of the OTA is derived, considering the design requirements. Among the structural-shape concepts of various OTAs, the Serrurier truss concept is selected in this study, and the collimation of the telescope according to the design variables is extensively discussed. After generating finite-element models for different structural shapes, self-gravity analyses are performed. To minimize the deflection and tilt of the mirror and frame for the OTA under the limited design requirements, a parametric study is conducted according to design variables such as the shapes of the upper and lower struts and the spider vane. The structural features found in the parametric study are described. Finally, the OTA structure is designed in detail to maintain the optical alignment by balancing the gravity deflections of the upper and lower trusses using the optimal combination of the parameters. Additionally, thermal analysis of the optical telescope design is evaluated.

• 센서학회지
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• 제10권3호
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• pp.163-172
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• 2001

넓은 지역에 걸친 침입자의 침투를 감시하기 위하여 수십 km의 광섬유 길이 전체를 감지부로 사용할 수 있는 광섬유 BOTDA (Brillouin Optical Time Domain Analysis) 센서를 개발하였다. 광섬유 BOTDA 센서는 한 개의 레이저 다이오드와 두 개의 광전 변조기(electro-optic modulator)를 사용하여 간단하게 구성하였다. 침입자에 의한 광섬유의 변형률 변화를 탐지하는 실험을 수행하기 위하여 광학테이블 위에 광섬유에 변형률을 인가하기 위한 실험장치를 설치하여 실험을 수행하였다. 이 실험으로부터 시간간격 1.5 초동안 광섬유 약 4.81 km의 길이를 거리분해능 3 m로 침입자를 탐지할 수 있음을 확인하였다.

• Current Optics and Photonics
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• 제3권6호
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• pp.577-582
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• 2019

We report on a continuous-wave (cw) optical parametric oscillator (OPO) optimized for mid-infrared emission above 5.0 ㎛. The OPO is based on a magnesium-oxide-doped periodically poled LiNbO₃(MgO:PPLN) crystal with a fan-out grating design. A linear two-mirror cavity resonating both at the pump and signal wavelengths is stabilized to the pump laser by using the modified Pound-Drever-Hall (PDH) method. The idler wavelength is continuously tunable from 4.7 ㎛ up to 5.3 ㎛ by varying the poling period of the fan-out grating crystal. Pumped by a diode-pumped solid state (DPSS) laser with a power of 1.1 W at 1064 nm, the maximum idler output power is measured to be 5.3 mW at 4.8 ㎛. The output power above 5.0 ㎛ is reduced to the hundreds of ㎼ level due to increased absorption in the crystal, but is stable and strong enough to be measured with a conventional detector.

• 대한기계학회논문집 C: 기술과 교육
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• 제5권1호
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• pp.53-61
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• 2017

광기술은 차세대 산업 분야에서 기계, 전자와의 융합을 통한 첨단 산업의 핵심요소이다. 또한 광기술은 현재 신성장동력인 IT, 디스플레이, 자동차, 의료, 반도체 등 국내 기간산업 제품의 품질 및 기능을 향상시켜 고부가 가치를 창출할 수 있는 기초 원천 핵심 기술 및 응용 기술로 활용되고 있으며, 향후 첨단 산업 분야에서 광기술 활용도는 더욱 더 높아질 것으로 예상되고 있다. 본 논문에서는 오늘날 산업 분야에서 중요도가 점차 높아지고 있는 광기술의 발전 동향을 21 세기 기계 산업과 관련하여 설명한다. 특히 다양한 광기술 분야 중에서 보다 기계산업과 관련성이 높은 반도체 조명, 광계측, 산업용 레이저 및 레이저 가공 기술을 중심으로 발전 동향을 살펴본다.

• 광학과기술
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• 제7권2호
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• pp.13-20
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• 2003

• 한국정밀공학회지
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• 제28권3호
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• pp.323-329
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• 2011

Certified reference materials (CRMs) have been used to calibrate surface profilers for reliable measurements. In this paper, we present a newly designed step height CRM which has a step height pattern with two different widths and various special patterns for checking radial magnification, distortion of optical viewing systems, etc. Especially, it could be useful for multi-probe inspection instruments in the manufacturing lines. The fabrication was done by conventional optical lithography and dry etching process with optimized conditions. To verify the step height values, a white-light scanning interferometer was used with objective lenses having magnification of $10{\times}$ and $100{\times}$. CRMs with nominal step heights of $0.5\;{\mu}m$, $1\;{\mu}m$, $3\;{\mu}m$, $5\;{\mu}m$, $7\;{\mu}m$, and $10\;{\mu}m$ were fabricated and the uniformity of these CRMs was evaluated to be less than 3 nm ($1{\sigma}$).

• Journal of the Optical Society of Korea
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• 제16권2호
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• pp.145-150
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• 2012

We present a display-based visual stimulator for psychophysical and electrophysiological visual sensitivity measurements. The stimulator offers various psychophysical visual stimuli and transfers the signals from external devices along with the stimulation signals to an electrophysiological recorder. As an experimental demonstration, we perform a visual sensitivity experiment in the mesopic vision range by using the display-based stimulator. The intensity of the steady-state visual evoked potential is observed to correlate with the luminance of the flickering visual stimulation. For the psychophysically determined detection thresholds, we determine the mesopic luminance, showing agreement with the perceived brightness within the uncertainty of the luminance measurement.