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광섬유 연결 반도체레이저 여기 세라믹 Nd:YAG 레이저에서 열렌즈 효과의 보상
김덕래,김영식,김병태,Kim, Duck-Lae,Kim, Yeong-Sik,Kim, Byung-Tai 한국광학회 2007 한국광학회지 Vol.18 No.3
광섬유 연결 반도체레이저 여기 세라믹 Nd:YAG 레이저의 열렌즈를 보상하기 위한 공진기를 구성하였다. 초점거리 30 mm, 유효직경 22 mm인 보상렌즈를 레이저 매질의 단면으로부터 25 mm 떨어진 곳에 위치시켜 열렌즈 효과를 보상하였다. 보상렌즈가 없는 경우 레이저 출력은 열렌즈 효과에 의해 여기파워 6 W 이상에서 급격히 감소하기 시작하였으며, 12 W에 이르러서는 레이저가 거의 발진되지 않았다. 열렌즈 효과가 보상되었을 경우 레이저 출력은 선형적으로 증가하였으며, 여기파워 12 W에서 $M^{2}$값은 2.4로 좋은 빔질을 나타내었다. A fiber-coupled laser-diode pumped ceramic Nd:YAG laser for compensating the thermal tensing effect was developed. The thermal tensing effect was compensated using a convex lens, which was 25 mm away from the laser rod, with a focal length of 30 mm and an effective clear aperture of 22 mm. Without a compensator, the laser output power decreased suddenly above a pump power of 6 W. Using a compensator, the laser output power increased linearly according to the pump power. The beam propagation factor $M^{2}$ was 2.4 under a pump power of 12 W.
Common Optical System for the Fusion of Three-dimensional Images and Infrared Images
김덕래,정 보 희,공현배,옥창민,이 승 태 한국광학회 2019 Current Optics and Photonics Vol.3 No.1
We describe a common optical system that merges a LADAR system, which generates a point cloud, and a more traditional imaging system operating in the LWIR, which generates image data. The optimum diameter of the entrance pupil was determined by analysis of detection ranges of the LADAR sensor, and the result was applied to design a common optical system using LADAR sensors and LWIR sensors; the performance of these sensors was then evaluated. The minimum detectable signal of the 128 × 128-pixel LADAR detector was calculated as 20.5 nW. The detection range of the LADAR optical system was calculated to be 1,000 m, and according to the results, the optimum diameter of the entrance pupil was determined to be 15.7 cm. The modulation transfer function (MTF) in relation to the diffraction limit of the designed common optical system was analyzed and, according to the results, the MTF of the LADAR optical system was 98.8% at the spatial frequency of 5 cycles per millimeter, while that of the LWIR optical system was 92.4% at the spatial frequency of 29 cycles per millimeter. The detection, recognition, and identification distances of the LWIR optical system were determined to be 5.12, 2.82, and 1.96 km, respectively.
김덕래,김태연,정전은 고려대학교 의과대학 1991 고려대 의대 잡지 Vol.28 No.1
The mechanism of tendon healing has been a controversial issue. Although there seems to be a dipolarizing opinion regarding the tendon heating, it is well known to us that the tendon has both intrinsic and extrinsic healing capacity which has been proved in vivo and in vitro studies. Tendon adhesion is a common sequella after tendon repair, particularly after the long period of immobilization. This can be explained by one wound concept or extrinsic tendon healing. If we can modify the natural healing process of the tendon by augmenting the intrinsic capacity, we can reduce the period of immobilization to allow early motion for better gliding. In this study, we used the electrical stimulation technique, which has been known to have good growth stimulatory effect on the living cells, to investigate its effect on tendon healing in organic culture for 6 weeks. Total 64 flexor tendons were harvested from 8 rabbit paws and they were cultured in separate petri-dishes : 32 tendons were used for the control group and the rest 32 were used for the electric stimulation group. Tendons through which a continuous 7 μAmp current was passed at the repair site were compared with the non stimulated controls. In reference to the histologic study with Hematoxylin & Eosin stain and van Gieson stain, the following results were obtained. 1. There was found no necrosis in the specimens of the control as well as the elctrical stimulation group during 6 weeks' culture period. 2. Starting from 1 week, there was prominent increase of fibroblastic proliferation and collagen production in electrical stimulation group and these active repair processes persisted up to 6 weeks. Accordingly, I conclude that the intrinsic tendon healing capacity can be enhanced by the electrical stimulation in vitro.