• Korean Journal of Optics and Photonics
• /
• v.24 no.2
• /
• pp.71-76
• /
• 2013

Using fluorescence correlation spectroscopy, we analyzed the change of effective focal volume of a confocal system with light intensity. The fluorescence correlation spectroscopy system was home-built in accordance with the He-Ne laser with a wavelength of 632.8 nm, and two kinds of samples (AlexaFluor657 and Quantum dot655) suitable for the wavelength of the laser beam were used. For each sample, we analyzed and compared the correlation functions obtained while changing the intensity of the light source in a range of 1~50 ${\mu}W$. The result shows that the radius of the focal area increases linearly through the increase of particle number and diffusion time in response to an intensity change in weak light below 10 ${\mu}W$. In the higher intensity region (>10~15 ${\mu}W$), the increasing rate of particle number and diffusion time keep increasing but at a much slower rate. Through this result, it was also found that the radius increasing rate of the focal area was reduced however, the radius still increased slightly.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.229.2-229.2
• /
• 2012

지금까지 해외의 여러 달 궤도선에서 달의 영상을 다양한 방법으로 관측한 것에서 알 수 있듯이 영상 관측은 달 탐사에서 중요한 부분이다. 특히 그 중에서 입체 영사기(Stereo Imager)는 달의 3차원적 영상을 관측하여 달 표면의 구조를 파악할 수 있고 분광 카메라(Hyperspectral Camera)는 달 표면을 이루고 있는 물질을 분광 정보를 통해서 알아낼 수 있다. 본 연구에서는 우리나라가 2020년경 독자적인 달 궤도선을 계획하고 있는 것에 발맞추어 이 두 관측 장비를 설계해 보았다. 본 연구에서 설계한 탑재체는 하나의 광학계를 이용해 가시광 영역에서 동시에 입체 영상과 분광 영상을 얻을 수 있는 장치이며, 달 표면에서의 궤도선의 속도와 저장 가능한 정보의 양을 고려하여 100 km의 고도에서 속도를 1.6 km/s로 가정할 때 interline CCD가 17.5 m의 공간 분해능을 갖기 위해 92 frame/s 이상의 frame rate로 관측을 수행할 수 있게 하였다. 특히 분광 카메라는 wedge filter를 사용하여 광학계의 부담을 줄였으며 검출기로는 interline CCD를 사용하여 channel 수를 조절할 수 있도록 하였다. 또한 달 표면을 구성하는 입자의 크기에 대한 정보를 얻을 수 있는 편광판도 설치 하였다. 시험 모델의 문제점을 분석하여 새롭게 개선된 탑재체를 설계하여 개발하였다. 렌즈를 수정해 vignetting과 왜곡 현상을 보정하였고 전체 무게를 1.5 kg으로 줄여서 시험 모델보다 30% 이상 줄일 수 있었다. 파장 분해능은 20nm로 시험모델보다 더 개선된 분해능을 얻을 수 있었다. 출력 효율의 증대를 위해 power board의 수정을 수행하였다.

• Korean Journal of Optics and Photonics
• /
• v.22 no.6
• /
• pp.283-290
• /
• 2011

A Raman LIDAR system has been designed and constructed for quantitative measurement of water vapor mixing ratio. The comparison with commercial microwave radiometer and global navigation satellite system(GNSS) was performed for the precipitable water vapor(PWV) profile and total PWV. The result shows that the total GNSS-PWV and LIDAR-PWV have good correlation with each other. But, there is small difference between the two methods because of maximum measurement height in LIDAR and the GNSS method. There are some significant differences between Raman and MWR when the water vapor concentration changes quickly near the boundary layer or at the edge of a cloud. Finally we have decided that MWR cannot detect spatial changes but LIDAR can measure spatial changes.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.6 no.1
• /
• pp.89-98
• /
• 2002

Optical current sensor and optical voltage sensor modules were designed and fabricated to improve measurement error and insulation in automatic power distributor By using Faraday effect, optical current sensor with an $\alpha$-iron core was designed and fabricated to minimize current induction of the other phase and was optimized to maintain linearity. Optical voltage sensor was fabricated owing to the pockets effect and adopted spatial electric field type because of small room in an automatic power distributor. To connect a distributor with an external terminal for signal processing, optical multi connector was designed, fabricated and tested for coupling loss and gas leakage. The linearity of optical current sensor for applied current maintains variation of smaller than 2.5% for applied current range from 20A to 700A. The linearity of optical voltage sensor was smaller than 1% for appling voltage from 6.6kV to 19.8kV. Since the measured characteristics are good, these devices can be considered as being applicable in practice.

• Korean Journal of Optics and Photonics
• /
• v.16 no.4
• /
• pp.334-339
• /
• 2005

We studied the spatial filtering characteristics of a multi-phase hologram optical low-pass filter(HOLF). Using the Monte-Carlo based hologram generation program, we designed holograms whose diffraction patterns are circular shaped 21 beams and calculated the diffraction efficiencies and MTFs. 4-phase HOLF have the same diffraction efficiency as that of 2-phase HOLF. The MTF graphs of the two are also nearly alike. But 8-phase HOLF shows higher efficiency than those previously discussed and has larger MTF values in the low frequency region. 16-phase HOLF has just a little better characteristics than 8-phase. Considering the errors which can arise in the process of making holograms, 8-phase HOLF fits the goal of improving the resolution of spatial filter. We also fabricated 8-phase HOLF and .measured MTF The experimental results agree well with the theoretical expectations.

• Korean Journal of Optics and Photonics
• /
• v.1 no.2
• /
• pp.210-216
• /
• 1990

This study was performed to obtain fundamental data on temperature increases in the dental tissues irradiated by IO.opm laser radiation. For this purpose a experimental facility was established. which was composed of a CO2 laser. a shutter unit and a temperature sensing device. The temperature changes in the pulp chamber of extracted molars. during and after the laser irradiation. were measured as function of laser power. the time of irradration and the thickness of the sample. An empirical formula for the maximum temperature increases, $\DeltaT_m$ was derived from the measured data as follows; $\DeltaT_m=\alphaP\Delta\tauexp(-\betad)$$ where P. $\Delta\tau$ and d are the laser power(W). irradiation time{sec) and the thickness(mm) between pulp chamber and occlusal surface. respectively. Also a theoretical calculation model based on simplified assumptions were established and the results from the calculation were compared with the measured temperature data. A fairly good agreement was obtained.obtained.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.08a
• /
• pp.102-103
• /
• 2000

화학레이저는 화학연료의 반응에서 생성되는 막대한 화학에너지를 이용하여 레이저를 발생시키며, 반응하는 화학연료의 양에 따라 수천 kW의 고출력을 낼 수 있는 가장 강력한 레이저이다. 화학레이저인 Chemical Oxygen-Iodine Laser(COIL)는 염소기체(Cl$_2$)를 염기성 과산화수소수 용액과 반응시켜 고에너지의 여기산소(O$_2$($^1$$\Delta$))를 생성시키고 여기산소가 다시 요오드 원자와 반응하면서 1.3 $mu extrm{m}$ 파장의 레이저를 발생시킨다.(1)-(2) 이와같은 COIL 레이저는 발진효율이 높고 포화 강도가 높아 수십 kW 급의 고출력이 용이하게 이루어 질 수 있으며 광섬유 전송시 광손실이 가장 적어 레이저 빔의 원격 전송에 의한 재료가공에 적합한 레이저이다. 가공용레이저로 많이 사용하는 $CO_2$ 레이저에 비해 발진 파장이 짧으므로 재료의 광흡수율이 높아 일반 산업분야의 용접/절단에서 기존의 $CO_2$ 레이저를 대체할 것으로 기대되는 상용성이 큰 레이저이다.(3)-(4) 또한 COIL은 우수한 집속 특성을 유지하면서도 고출력의 개발이 가능하다. 이미 외국에서는 비록 단시간 동안 동작하지만 수백 kW급이 실현되었으며 수천 kW 급 고출력 항공기탑재형 COIL 이 수백 km의 거리에서 미사일을 요격하기위해 지금 개발중에 있다.(5) 일반 산업용 광섬유에 의해 쉽게 전송되는 파장인 1.315 $\mu\textrm{m}$ 인 수십 kW 급 COIL 은 조선 등의 중공업산업용 및 원자력 제염/해체분야에서 다용도 기술로서 광범위하게 사용될 것이다. COIL은 다양한 재료와 다양한 두께의 구조물 절단, 표면처리 그리고 용접에도 이용될 수 있다. COIL의 산업화는 빠르게 발전하고 있으며 산업용으로써 장시간 연속사용이 가능한 20-30 kW급 시설이 곧 개발될 것으로 기대된다. 따라서 개발될 고출력 화학레이저가 앞으로 원자력시설의 해체시 작업자의 안전성 향상에 크게 기여할 수 있게 되었다.(6) 여기서는 화학레이저인 COIL 장치와 기본적인 원리, 그리고 염소유량에 따른 출력특성등을 살펴보기로 하겠다. (중략)

• Journal of the Korean Vacuum Society
• /
• v.20 no.3
• /
• pp.176-181
• /
• 2011

$Y_{1-x}BO_3:Ce_x^{3+}$ ceramic phosphors were synthesized with changing the concentration of $Ce^{3+}$ ion by using a solid-state reaction method. The crystal structure, surface morphology, and optical properties of the blue phosphors were investigated by using X-ray diffractometer (XRD), scanning electron microscopy, and photoluminescence and photoluminescence excitation spectrophotometry, respectively. The XRD results showed that the main peak of the phosphor powders occurs at (401)와 ($31\bar{2}$) planes. As for the optical properties, the excitation spectrum occurred at 243 nm and the value of blue emission intensity peaking at 469 nm reached the maximum when the concentration of $Ce^{3+}$ ion was 0.10 mol.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.447-454
• /
• 2006

We obtained analytic solutions of boundary conditions to the stable region of Z-fold $Cr^{4+}$ : YAG laser cavity when the conditions are with and without thermal tensing effect. Also we investigated the influence of the thermal tensing effect on the stability of cavity, beam waist, and astigmatic compensation using aberration transformation matrices. The thermal tensing effect almost has no influence on the stable region of the cavity when the crystal is located in the middle of two concave mirrors and when the distances from the concave mirror to the reflecting mirror and the output coupler are the same. The beam waist, however, is affected more in a tangential plane than in a sagittal plane, and so it is difficult to have astigmatic compensation when the thermal tensing effect exists. This result means that the thermal tensing effect should be considered even for the Kerr-lens mode-locking.

• Korean Journal of Optics and Photonics
• /
• v.25 no.2
• /
• pp.102-107
• /
• 2014

In this paper the spectra of correlated color temperature (CCT) tunable white light-emitting diode (LED) luminaires, consisting of commercial red, green, blue, and amber LED chips, were optimized to increase color rendering index (CRI), and a special CRI of R9 for deep red color was obtained. To improve the design's accuracy, measured LED spectra were used instead of mathematically modeled ones. Real CCT tunable LED luminaires with CRIs of 87-90 and R9s of 34-93 were fabricated and demonstrated at CCTs of 3000-6000 K.