• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.500-509
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• 2016

Integrating spheres play a central role in the radiometric calibration of remote sensors. With the development of the wide field of view (FOV) remote sensors, aperture diameters of remote sensors are becoming larger and larger. To satisfy the radiometric calibration requirements of full FOV and full aperture, an 8000mm diameter large aperture integrating sphere uniform source with a variable exit port was designed and manufactured. This integrating sphere will be used for pre-launch test and radiometric calibration of remote satellites. In this paper, optical theories were used to design the output spectral radiance. The LightTools software based on ray-tracing simulation method was used to determine the best combination and distribution of inner light sources. A spectral experiment was made to verify the spectral radiance design. To reduce the influence of longtime power-on, a new characteristic measurement method was developed to obtain the radiation characteristic of the integrating sphere, which could greatly improve the measuring efficiency. This method could also be applied to measure other large aperture uniform sources. The obtained results indicate that the spatial uniformity is 98.35%, and the angular uniformity at center position is 98.78%.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.198-199
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• 2000

다목적 실용위성 (KOMPSAT) 1호기에 탑재되는 해양관측카메라 Ocean Scanning Multi-spectral Imager (OSMI)는 해양 결상계의 노화에 따른 성능 변화 감지 및 보정을 위해 태양광 보정을 궤도운영 중 수행한다. 태양광 보정의 구조 및 광학적 특성을 분석하고 OSMI 주요 관측파장대역별로 태양광 보정계의 출력신호량을 예측하였다. 이 분석은 OSMI 센서보정 계획 및 영상 품질 이해에 유용할 것이다. (중략)

• 대한기계학회논문집B
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• 제27권6호
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• pp.789-795
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• 2003

It is studied that the measuring method of the spectral emissivity by using hemispherical mirror with an inclined observation hole. The in-service calibration method of mirror reflectivity is also dealed with. It is possible to apply this method on measuring emissivity of conductor or non-conductor.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1133-1133
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• 2001

Fruit sweetness, as indexed by total soluble solids (TSS), and fruit acidity are key factors in the description of the fruit eating quality. Our group has been using short wave NIR spectroscopy (SW-NIR; 700-1100 nm) in combination with chemometric methods (PLS and MLR) for the non-invasive determination of the fruit eating quality (1,2). In order to further improve calibration performance, we have investigated SW-NIR spectra of sucrose and D-glucose. In previous reports on the band assignment for these sugars in the 1100-2500 nm spectral region (3-7), it has been established that change in concentration, temperature and physical state of sugars reflects on the shape and position of the spectral bands in the whole NIR region(5-7). The effect of change in concentration and temperature of individual sugar solutions and sugar spiked Juice samples was analysed using combined spectroscopic (derivative, difference, 2D spectroscopy) and linear regression chemometric (PLS, MLR) techniques. The results have been compared with the spectral data of a range of fruit types, varying in TSS content and temperature. In the 800-950 nm spectral region, the B-coefficients for apples, peaches and nectarines resemble those generated in a calibration of pure sucrose in water (Fig. 1). As expected, these fruits exhibit better calibration and prediction results than those in which the B-coefficients were poorly related to those for sugar.(Figure omitted).

• Journal of Astronomy and Space Sciences
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• 제17권2호
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• pp.295-308
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• 2000

OSMI(Ocean Scanning Multi-Spectral Imager) raw image data(Level 0) were acquired and radiometrically corrected. We have applied two methods, using solar & dark calibration data from OSMI sensor and comparing with the SeaWiFS data, to the radiometric correction of OSMI raw image data. First, we could get the values of the gain and the offset for each pixel and each band from comparing the solar & dark calibration data with the solar input radiance values, calculated from the transmittance, BRDF (Bidirectional Reflectance Distribution Function) and the solar incidence angle($\beta$, $\theta$) of OSMI sensor. Applying this calibration data to OSMI raw image data, we got the two odd results, the lower value of the radiometric corrected image data than the expected value, and the Venetian Blind Effect in the radiometric corrected image data. Second, we could get the reasonable results from comparing OSMI raw image data with the SeaWiFS data, and get a new problem of OSMI sensor.

• Current Optics and Photonics
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• 제4권4호
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• pp.345-352
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• 2020

We describe a calibration method to improve the accuracy of interferometric snapshot spectroscopic ellipsometry employing a dual-spectrometer sensor scheme. Conventional spectral wavelength calibration of a spectrometer has been performed by using a calibration lamp having multiple peaks at specific wavelength. This paper shows that such a conventional spectrometer calibration method is inappropriate for the proposed interferometric snapshot spectroscopic ellipsometry to obtain highly accurate ellipsometric phase information. And also, systematic error analysis of interferometric snapshot spectroscopic ellipsometry is conducted experimentally.

• Near Infrared Analysis
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• 제1권1호
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• pp.1-7
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• 2000

A convenient algorithm for optimizing wavelength selection in multiple linear regression (MLR) has been developed. MOP (MLP Optimization Program) has been developed to test all possible MLR calibration models in a given spectral range and finally find an optimal MLR model with external validation capability. MOP generates all calibration models from all possible combinations of wavelength, and simultaneously calculates SEC (Standard Error of Calibration) and SEV (Standard Error of Validation) by predicting samples in a validation data set. Finally, with determined SEC and SEV, it calculates another parameter called SAD (Sum of SEC, SEV, and Absolute Difference between SEC and SEV: sum(SEC+SEV+Abs(SEC-SEV)). SAD is an useful parameter to find an optimal calibration model without over-fitting by simultaneously evaluating SEC, SEV, and difference of error between calibration and validation. The calibration model corresponding to the smallest SAD value is chosen as an optimum because the errors in both calibration and validation are minimal as well as similar in scale. To evaluate the capability of MOP, the determination of benzene content in unleaded gasoline has been examined. MOP successfully found the optimal calibration model and showed the better calibration and independent prediction performance compared to conventional MLR calibration.

• Journal of Astronomy and Space Sciences
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• 제21권4호
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• pp.391-398
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• 2004

2003년 9월 27일 과학기술위성 1호가 성공적으로 발사된 이래, 주탑재체인 원자외선분광기(Far-ultraviolet Imaging Spectrograph, FIMS)는 초기 운용 모드를 거쳐 현재까지 정상 관측을 수행하고 있다. FIMS는 전천관측을 통해 우리은하의 뜨거운 가스의 분포를 측정하고 있으며, 초신성 잔해 및 성간운의 수소 방출선, 그리고 지구 대기의 대기광 등에 대한 관측을 수행하고 있다. FIMS의 광학계 및 검출기는 지상에서 특성 평가 및 보정을 마쳤지만, 우주 발사 과정의 진동에 의한 효과, 우주 환경에의 노출 등에 의한 효과로 인해 궤도상 보정이 필수적이다. 한편, 지구 대기에는 수소 및 질소 분자 등이 태양빛을 받아 강한 방출선들을 내는데 이들은 파장 보정의 좋은 기준선들이 된다. 이 논문에서 우리는 FIMS로 대기광 방출선들을 관측하였고, 관측된 방출선을 검출기의 위치에 따라 모델 스펙트럼과 비교하여 그 차이를 구하였으며, 이것을 보정시킴으로써 FIMS의 장파장에서의 분해능 및 정확도를 향상시키는데 기여하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.616-619
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• 2005

CALNAL team of Korea Aerospace Research Institute(KARI) performed field campaigns for absolute radiometric calibration of 1m satellite image on Daejeon and the cal/val site of Goheung. The satellite image have spatial resolution of 1m in panchromatic spectral band of 450-900nm. The performed cal/val method is the reflectance-based of vicarious calibration methods. We collected ground-based and meteology data such as temperature, surface pressure and reflectance of targets, and radiosonde data used only to test in Goheung. Data collected on each field served as input to radiative transfer codes to generate a top-of-atmosphere(TOA) radiance estimate. Derived TOA is compared with DN of overpass satellite to calculate calibration coefficient of gain and offset.

• Journal of Radiation Protection and Research
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• 제26권3호
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• pp.243-248
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• 2001

Neutron reference fields of Korea Atomic Energy Research Institute (KAERI) for calibrating neutron measuring devices to be used in radiation workplace monitoring consist of two kinds of neutron spectra, the direct and the scattered neutron fields, which are produced by using radionuclide neutron sources, 252Cf and 241AmBe sources. Necessary parameters for calibration such as the anisotropy factor of each neutron source and the room-scattered fraction of some neutron surveymeters in the KAERI calibration facility were determined by calculation or measurement. Spectral measurement of scattered neutron fields were performed at each reference calibration point using a Bonner Multi-sphere Spectrometer (BMS) and the dosimetric quantities for calibration also estimated from the neutron energy spectra which were unfolded using the BUNKI code.