• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.555-568
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• 2013

Atmospheric optical thickness during nighttime was estimated in this study using analysis on the images of the moon taken from commercial digital camera. Basically the Langely Regression method was applied to the observations of the moon for the cloudless and optically stable sky conditions. The spectral response functions for the red(R), green(G), and blue(B) channels were employed to derive effective wavelength centers of each channel for the observations of the moon, and the correspondent Rayleigh optical thickness were also calculated. Aerosol optical thickness (AOT) was calculated by subtracting Rayleigh optical thickness from the atmospheric optical thickness derived from the Langley regression method. As there are only handful of nighttime AOT observations, the AOT from the moon observations was compared with the AOT from sun-photometers and the MODIS satellite sensor, which was taken several hours before the moon observations of this study. As a result, the values of AOT from moon observations agree with those from sun-photometers and MODIS within 0.1 for the R, G, B channels of the digital camera. On the other hand, ${\AA}$ngstr$\ddot{o}$m Exponent seems to be subject to larger errors due to its sensitiveness to the spectral errors of AOT. Nevertheless, the results of this study indicate that the method reported in this study is promising as it can provide nighttime AOT relatively easily with a low cost instrument like digital camera. More observations and analyses are warranted to attain improved nighttime AOT observations in the future.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.198-199
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• 2002

진공 증착장비에서 다층박막으로 구성된 광학필터를 증착할 경우, 증착되는 동안 설계된 최종 광학필터의 성능을 구현하기 위해서는 실시간으로 각각의 층들에 대한 굴절률(n)과 물리적 두께(d)를 제어하거나 또는 광학적 두께(nd)를 제어해야 한다. 광학적 두께를 제어하는 대표적인 예로 광모니터링 방법이 있는데, 증착되는 기판에 직접 빛을 입사시켜 기판에서 반사된 빛이나 투과된 빛의 세기를 측정하여 증착과정을 제어하는 방법이다. (중략)

• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.607-615
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• 2017

The aerosol optical thickness data retrieved by Moderate Resolution Imaging Spectrometer (MODIS) of Terra & Aqua and Meteorological Imager (MI) of Communication Ocean and Meteorological Satellite (COMS) are analyzed and compared with the measurement data of Aerosol Robotic Network (AERONET) in Northeast Asia. As the result, the aerosol optical thickness retrieved by MODIS and MI were well agreed at ocean region but quite different at cloud edge and barren surface. The reason was that MODIS aerosol optical thickness was retrieved using the visible and infrared channels but MI was retrieved with the visible channel only. Consequentially, the thin cloud be misinterpreted as aerosol by MI and the difference between MODIS and MI aerosol optical thicknesses could be occurred with Normal Distribution Vegetation Index (NDVI) and land surface property. Therefore, the accuracies of clear/cloud region and surface reflectivity are required in order to improve the aerosol optical thickness algorithm by MI.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.245-256
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• 1995

Rugate filters of inhomogeneous refractive index were designed using the Fourier transform and the effect of reflectance, stop bandwidth, optical thickness, and Q function on the rugate filter was investigated. An iterative correction process using a merit function was employed to fit an initial design to the target spectrum. Three Q functions derived by Sossi, Bovard, and Fabricius, respectively, were compared in terms of the number of iteration, merit function, and optimum optical thickness. The result shows that after a number of iterations the Q functions by Bovard and Fabricius produce high rejection rugate filters closer to the target spectrum than the Sossi's Q function and the optimal optical thickness is determined by the stop-band width of the rugate filter. ilter.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.26-30
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• 1997

A wide dynamic range heterodyne interferometer scheme using intermode beat between a stabilized, dual frequency He-Ne laser beam has been applied for a measurement of optical thickness of an optical medium. Resolution of the optical thickness measurement is about $\pm$ 1.74 ${\mu}{\textrm}{m}$. Using this technique, we are able to determine the optical thickness of an organic dye film. We also obtain a map of the optical thickness variations over a surface of the film

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.326-326
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• 2013

본 연구에서는 회전 원통형 마그네트론 스퍼터링 시스템(Cylindrical Magnetron Sputtering)을 이용하여 성막한 Sn-doped $In_2O_3$ (ITO) 투명전극의 두께 변화에 따른 전기적, 광학적, 구조적 특성을 연구하였다. 회전 원통형 마그네트론 스퍼터링 시스템을 이용한 ITO 투명전극은 박막의 두께가 50~1,000 nm의 두께로 증가함에 따라 비저항 값은 일정하게 유지되나 면저항 값이 $37.8{\Omega}$/square로부터 $1.5{\Omega}$/square로 점차적으로 감소됨을 확인할 수 있었다. 또한 ITO 박막의 두께 증가가 50 nm에서 1,000 nm로 증가함에 따라 400~800nm 파장 범위에서 71~83％의 높은 광투과도를 나타내었다. 두께 변화에 따른 광학적 특성 변화를 설명하기 위해 Spectroscopic ellipsometry 분석을 실시하였으며 이를 기반으로 박막 두께와 투과도의 상관관계를 설명하였다. 한편, 원통형 마그네트론 스퍼터로 성장시킨 ITO 박막은 두께가 50~200 nm의 범위에서는 (222) 방향으로 우월 성장하였으나, 200-1000 nm 두께 범위에서는 우월 성장방향이 (400)과 (622)로 바뀜을 X-ray diffraction (XRD) 분석을 통하여 확인하였다. 이를 통해 박막의 두께변화에 따른 전기적/광학적 특성의 변화는 박막의 구조와 매우 밀접한 상관관계가 있음을 알 수 있었다.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.90-93
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• 1991

일곤 레이저의 두 파장(488 nm, 514.5 nm)을 사용하여 은 박막과 은 박막 위에 덧증착한 ZnS 박막의 유일한 광학 상수와 두께를 Kretschmann 구조의 표면 플라즈몬 공명을 이용하여 결정하였다.

• Korean Journal of Optics and Photonics
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• v.2 no.2
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• pp.59-66
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• 1991

Resonance angle and optimum thinckness of various thin metal films for surface plasmon resonance were calculated using an admittance diagram and optical constants and thickness of thin Ag films and Al films were determined by fitting the measured reflectance of surface plasmon resonance. Two wavelengths of an Ar ion laser were employed to select the unique optical constants which have the same thickness at two wavelengths. Also, when these films were exposed to the air, the shift of surface plasmon resonance was measured and the optical constants of modified thin films were determined.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.286-287
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• 2003

최근 음성, 화상 및 동영상 등의 대용량 정보전송 요구에 따라 광 통신용 광학 박막의 필요성이 점차 증대되고 있으며, 특히 광통신에서 주로 사용되는 두 파장영역(1300nm／1500nm)을 분리하는 1300nm／1500nm 경계 필터는 WDM 양방향 광통신 시스템 등에 많이 응용 되고 있다. 광통신용 광학 박막은 보통 그 증착 두께가 일반 광학 박막에 비해 매우 두꺼우므로 증착 시 두께 조절의 어려움이 있을 수 있으며, 오랜 시간 증착 하는 동안 증착조건의 변화에 의해 증착물질의 광학상수의 변화 등 여러 가지 문제점들을 가질 수 있다. (중략)

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.1-10
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• 1992

A simple formula of the envelope method, which uses two envelopes fitted to the transmittance at quarter- and half-wave optical thicknesses, is derived to determine the optical constants (refractive index and extinction coefficient) and the thickness of weakly absorbing thin films. We applied the envelope method to ZnS and SiOx films deposited in a vacuum chamber and determined the optical constants at different deposition conditions. For SiOx films, the decrease in refractive index is consistent with the increase in stoichiometry as the backfilled oxygen pressure increases.