• Journal of Biosystems Engineering
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• 제37권6호
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• pp.411-419
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• 2012

Purpose: Nondestructive evaluation of seed viability is a highly demanded technique in the seed industry. In this study, hyperspectral imaging system was used for discrimination of viable and non-viable radish seeds. Method: The spectral data with the range from 400 to 1000 nm measured by hyperspectral reflectance imaging system were used. A calibration and a test models were developed by partial least square discrimination analysis (PLS-DA) for classification of viable and non-viable radish seeds. Either each data set of visible (400~750 nm) and NIR (750~1000 nm) spectra and the spectra of the combined spectral ranges were used for developing models. Results: The discrimination accuracy of calibration was 84% for visible range and 76.3% for NIR range. The discrimination accuracy of test was 84.2% for visible range and 75.8% for NIR range. The discrimination accuracies of calibration and test with full range were 92.2% and 92.5%, respectively. The resultant images based on the optimal PLS-DA model showed high performance for the discrimination of the nonviable seeds from the viable seeds with the accuracy of 95%. Conclusions: The results showed that hyperspectral reflectance imaging has good potential for discriminating nonviable radish seeds from massive amounts of viable seeds.

• 한국해양공학회지
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• 제25권2호
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• pp.1-6
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• 2011

Vibration-based Structural Health Monitoring (SHM) systems use field measurements of operational signals, which are distorted by noise from many sources. Reducing this noise allows a more accurate assessment of the original "clean" signal and improves analysis results. The implementation of a noise reduction methodology for the Modal Distribution Method (MDM) is reported here. The spectral subtraction method is a popular broadband noise reduction technique used in speech signal processing. Its basic principle is to subtract the magnitude of the noise from the total noisy signal in the frequency domain. The underlying assumption of the method is that noise is additive and uncorrelated with the signal. In speech signal processing, noise can be measured when there is no signal. In the MDM, however, the magnitude of the noise profile can be estimated only from the magnitude of the Power Spectral Density (PSD) at higher frequencies than the frequency range of the true signal associated with structural vibrations under the additional assumption of white noise. The implementation of the spectral subtraction method to MDM may decrease the energy of the individual mode. In this work, a modification of the spectral subtraction method is introduced that enables the conservation of the energies of individual modes. The main difference is that any (negative) bars with a height below zero after subtraction are set to the absolute value of their height. Both noise reduction methods are implemented in the MDM, and an application example is presented that demonstrates its effectiveness when used with a signal corrupted by noise.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.601-603
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• 2004

Multi-Spectral Camera(MSC) is a payload on the KOMPSAT -2 satellite to perform the earth remote sensing. The instrument images the earth using a push-broom motion with a swath width of 15 km and a ground sample distance (GSD) of 1 m over the entire field of view (FOV) at altitude 685 Km. The instrument is designed to have an on-orbit operation duty cycle of $20\%$ over the mission lifetime of 3 years with the functions of programmable gain! offset and onboard image data compression/storage. MSC instrument has one(1) channel for panchromatic Imaging and four(4) channel for multi-spectral Imaging covering the spectral range from 450nm to 900nm using TDI CCD Focal Plane Array (FPA). In this paper, the configuration, the interface of MSC hardware and the MSC operation concept are described. And the method of the MSC calibration are described and the design of MSC calibration operation to measure the change of MSC after Launch & Early Operation(LEOP) and normal mission operations are discussed and analyzed.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.216-221
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• 2011

A diffraction grating is a highly symmetric optical element with a physical structure that is invariant under translational spatial movements. The translational symmetry is reflected in the fields that are diffracted from the grating. Here, we introduce a plane-parallel mirror pair onto the grating, which translates the fields through double reflections, and we describe a method of exploiting the symmetry to enhance the spectral resolution of a diffraction grating beyond the limit that is set by the number of grooves. The mirror pair creates another virtual grating beside the original one, effectively doubling the number of grooves. Addition of more mirror pairs can further increase the effective number of grooves despite the increased complexity and difficulty of experimental implementation. We experimentally demonstrate the spectral linewidth reduction by a factor of four in a neon fluorescence spectrum. Even though the geometrical restriction on the mirror deployment limits our method to a certain range of the whole spectrum, as a practical application example, a bulky spectrometer that is nearly empty inside can be made compact without sacrificing the resolution.

• 천문학회지
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• 제38권4호
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• pp.445-462
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• 2005

In a companion paper, we have presented so-called Spatio-Spectral Maximum Entropy Method (SSMEM) particularly designed for Fourier-Transform imaging over a wide spectral range. The SSMEM allows simultaneous acquisition of both spectral and spatial information and we consider it most suitable for imaging spectroscopy of solar microwave emission. In this paper, we run the SSMEM for a realistic model of solar microwave radiation and a model array resembling the Owens Valley Solar Array in order to identify and resolve possible issues in the application of the SSMEM to solar microwave imaging spectroscopy. We mainly concern ourselves with issues as to how the frequency dependent noise in the data and frequency-dependent variations of source size and background flux will affect the result of imaging spectroscopy under the SSMEM. We also test the capability of the SSMEM against other conventional techniques, CLEAN and MEM.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.382-386
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• 1998

The objectives of this study are to reveal relationship between tree physiology and spectral reflectance on effects of artificial acid rain and to obtain basic data on optimal wave length for forest of LRC sensor on KOMPSAT-2. Three pH levels of artificial acid rain - control, pH4.5 and pH3.0 - were applied to Pinus and Quercus species. Three types of the acid rain were spraied at the amount of 500m1 in every two days. Spectral reflectance data was collected once in a month by using GER 1500 (350~2500nm) or Ll 1800(300~1100nm) Spectroradiometer. The data was measured three times in a pH level. The results of this study are as follows; in April, the spectral reflectance of Pinus species was high in order at the level of pH3.0, control and pH4.5; in May, control, pH3.0 and pH4.5; in June, control, pH4.5 and pH3.0. That of Quercus species was high in the order of control, pH4.5 and pH3.0 in May; in June, control, pH3.0 and pH4.5, especially, within infrared wave length range, control, pH4.5 and ph3.0.

• Design & Manufacturing
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• 제9권2호
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• pp.20-24
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• 2015

Recently, the light guide plate (LGP), a component of the BLU, becomes thinner and larger than ever. In industrial field, specialized injection molding technique is applied to mold the ultra-thin LGP such as a ultra-high speed injection molding. Usually very high melt temperature is used for low viscosity. High injection speed and melt temperature lead to yellowing of LGP. In the present paper a series of injection molding experiment was performed under various injection molding conditions. Yellow index, CIE xy, spectral transmittance of sample were measured using the UV-Visible spectrophotometer. Systematic decrease of spectral transmittance in UV-B range was found as the melt temperature was higher. Yellow index and CIE xy were became higher near the gate location in LGP. From the result of analysis of variance, the main factor to affect for yellow index was mold temperature and that for spectral transmittance(at 315 nm) was melt temperature.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.825-827
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• 2003

Multi-Spectral Camera(MSC) is a payload on the KOMPSAT-2 satellite to perform the earth remote sensing. The instrument images the earth using a push-broom motion with a swath width of 15 km and a ground sample distance (GSD) of 1 m over the entire field of view (FOV) at altitude 685 Km. The instrument is designed to have an on-orbit operation duty cycle of 20% over the mission lifetime of 3 years with the functions of programmable gain/ offset and on-board image data compression/storage. The MSC instrument has one(1) channel for panchromatic imaging and four(4) channel for multi-spectral imaging covering the spectral range from 450nm to 900nm using TDI CCD Focal Plane Array (FPA). In this paper, the architecture and function of MSC hardware including electrical interface and the operation concept which have been established based on the mission requirements are described. And the design and the preparation of MSC system operation are analyzed and discussed.

• Current Optics and Photonics
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• 제6권3호
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• pp.282-287
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• 2022

Narrowing the spectral linewidth and improving the wavelength stability of high-power laser diodes (HPLDs) are both in high demand for rapidly maturing industrial laser applications. In this study, we investigate the spectral behavior of a commercial HPLD bar module composed of 19 laser diodes (LDs) in a single-layered bar with a built-in volume Bragg grating (VBG) and an additional cascaded VBG. Optical loss due to the extra cascaded VBG is kept below 5% when the optical output is 5 W or more. The full width at half maximum of the Fabry-Perot peak from the cascaded VBG is reduced to about 12.4% and 29.1% at the edge (1^st LD) and center (10^th LD) of the HPLD bar module respectively, compared to using only a built-in VBG at an optical power of 10 W or more. In addition, fine wavelength tuning is achieved by temperature control of the extra VBG, and the obtained wavelength-tuning range amounts to about 10.6 pm/K.

• 대한원격탐사학회지
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• 제22권2호
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• pp.111-121
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• 2006

분광각(Spectral Angle)을 이용한 분류는 같은 종류의 지표 대상물의 분광 특성이 대기 및 지형적인 영향으로 인해 원점을 기준으로 유사한 분광각을 가지며, 선형적인 분포 모양을 가진다는 가정에 기초한 분류 방식이다. 최근 분광각을 이용한 무감독 분류에 대한 연구가 활발히 이루어지고 있으나, 하이퍼스펙트럴 데이터의 특성을 반영한 효과적인 무감독 분류에 대한 연구는 미진한 상태이다 본 연구는 하이퍼스펙트럴 영상 분류에 있어서 기존 무감독 분광각 분류(USAC, Unsupervised Spectral Angle Classification) 연구에서 나타난 문제점들을 보완한 반복최적화 무감독 분광각 분류(ISOUSAC, Iterative Self-Organizing USAC) 기법을 제안하고 있다. 이를 위해, 무감독 분광각 분류에 적합한 각 분할(Angle Range Division) 기법을 적용하여 군집 초기 중심을 설정하였고, 군집 중심 계산에 있어서 각 중심을 이용하였다. 뿐만 아니라 병합(Merge)과 분할(Split)를 통한 유동적인 군집 분석을 수행하였다. 결과를 통해, 제안된 알고리즘이 기존의 기법보다 수행 시간뿐 아니라 시각적, 정량적인 면에서 우수한 결과를 도출하였으며, 분광각을 이용한 군집 유효성 지수(Validity Index)를 제안함으로써 기존의 무감독 분광각 분류와 정량적 비교를 수행하였다.