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Bathymetric LiDAR Green Channel Derived Reflectance: An Experiment from the Dongsha 2010 Mission
(2016-08-01)
Lin, Wei-Tsun
;
Shih, Peter Tian-Yuan
;
Chen, Jie-Chung
;
Liao, Chun-Jie
;
土木工程學系
Bathymetric LiDAR utilizes a green laser capable of penetrating water and surveying seafloor topography. The intensity of the echo identified as the seafloor carries information about the substrate type. However, besides the reflectance characteristics of the substrate, there are also other influencing factors, including those from the LiDAR system and the environment. The data collected in the 2010 Dongsha atoll bathymetric LiDAR mission is processed and analyzed in this study. The corrections for environmental factors, mainly contributed from the water column that is presented as the inherent optical parameters of water are retrieved from the recorded green laser waveform. Those from the system, such as deviations between the signal receptors or between laser beam angles to each interface, are eliminated with data from IMU (Inertial Measurement Unit), scanner controlling mechanisms, etc. The resulting reflectance from each flight line is compared in the overlap area. The reflectance of the west side strip is subtracted from that of the east side strip. The reflectance is scaled between zero and one. While the mean of the differences is -0.0037, the standard deviation is 0.0436 for the flight line with a flight height of 400 m. The mean and standard deviation are -0.0058 and 0.0272, respectively, with flight height of 300 m. When interpolating the reflectance from the 300 m flight altitude dataset into a surface after subtracting the point measurement from the 400 m flight altitude, the mean and standard deviations are -0.0215 and 0.0382, respectively. This indicates that the consistency among flight lines of the same flight altitude is higher than those from different flight altitudes. A WorldView-2 (WV-2) image is compared with the LiDAR reflectance, and after atmospheric correction, the green band reflectance from WV-2 showed high similarities between the two image types. However, in the deep water region the one derived from LiDAR has much more information content.
Bathymetric LiDAR Green Channel Derived Reflectance: An Experiment from the Dongsha 2010 Mission
(2016-08)
Lin, Wei-Tsun
;
Shih, Peter Tian-Yuan
;
Chen, Jie-Chung
;
Liao, Chun-Jie
;
土木工程學系
Bathymetric LiDAR utilizes a green laser capable of penetrating water and surveying seafloor topography. The intensity of the echo identified as the seafloor carries information about the substrate type. However, besides the reflectance characteristics of the substrate, there are also other influencing factors, including those from the LiDAR system and the environment. The data collected in the 2010 Dongsha atoll bathymetric LiDAR mission is processed and analyzed in this study. The corrections for environmental factors, mainly contributed from the water column that is presented as the inherent optical parameters of water are retrieved from the recorded green laser waveform. Those from the system, such as deviations between the signal receptors or between laser beam angles to each interface, are eliminated with data from IMU (Inertial Measurement Unit), scanner controlling mechanisms, etc. The resulting reflectance from each flight line is compared in the overlap area. The reflectance of the west side strip is subtracted from that of the east side strip. The reflectance is scaled between zero and one. While the mean of the differences is -0.0037, the standard deviation is 0.0436 for the flight line with a flight height of 400 m. The mean and standard deviation are -0.0058 and 0.0272, respectively, with flight height of 300 m. When interpolating the reflectance from the 300 m flight altitude dataset into a surface after subtracting the point measurement from the 400 m flight altitude, the mean and standard deviations are -0.0215 and 0.0382, respectively. This indicates that the consistency among flight lines of the same flight altitude is higher than those from different flight altitudes. A WorldView-2 (WV-2) image is compared with the LiDAR reflectance, and after atmospheric correction, the green band reflectance from WV-2 showed high similarities between the two image types. However, in the deep water region the one derived from LiDAR has much more information content.
Comprehensive Study on Reflectance of Si3N4 Subwavelength Structures for Silicon Solar Cell Applications Using 3D Finite Element Analysis
(2011)
Lu, Zheng-Liang
;
Li, Yiming
;
電機學院
;
電子工程學系及電子研究所
;
College of Electrical and Computer Engineering
In this work, a full 3D finite element analysis for the silicon nitride (Si3N4) subwavelength structure (SWS) deposited on the antireflection coating (ARC) of a-Si thin film solar cell is conducted. We investigate the reflectance property of cylinder-, right circular cone-, and square pyramid shape of Si3N4 SWS with various heights and incident angles. The results show that the pyramid shape of SWS possesses the best reflectance property in the optical region from 400 am to 1000 rim. Comparison with the RCWA work is also reported.
Investigation of omnidirectional reflection band in ZnTe/ZnSe distributed Bragg reflector
(2015-11-15)
Huang, Ying-Shin
;
Hu, Sheng-Yao
;
Lee, Yueh-Chien
;
Chang, Chung-Cheng
;
Tiong, Kwong-Kau
We report the characteristics of reflectance spectra of the 15- and 20-period ZnTe/ZnSe distributed Bragg reflector grown on GaAs (001) substrates by molecular beam epitaxy. The reflectance spectra measured at various incident angles and polarizations were investigated by the theoretical curves simulated using transfer matrix method. The wavelength variation of the refractive indices described by Sellmeier equation and random thickness model were also considered for the interpretation of the experimentally observed curves. An omnidirectional reflection range defined from the edge of incident-angle-dependent reflection band with TE and TM polarizations is about 15 nm, and is consistent with the observed experimental curves. The results showed that the selected ZnTe and ZnSe materials are suitable for constructing multilayer structures having omnidirectional reflection band. (C) 2015 Elsevier B.V. All rights reserved.
Estimation of spectral radiance on a tristimulus color sensor system illuminated under two light sources
(2015-01-01)
Mang, Ou-Yang
;
Hsieh, Yao-Fang
;
Lee, Cheng-Chung
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
The tristimulus color sensor system, a trichromatic camera, is developed to estimate the spectral radiance of objects. However, since the spectral sensitivity of the system does not match the Commission International de l\'Eclairage (CIE) 1931 color matching function, it yields inaccurate colorimetric and spectral information. This work proposes methods using two light sources for estimating accurate spectral radiance and verifies that the accuracy achieved using these two illuminant methods exceeds that achieved using single illuminant methods. The two illuminant methods successfully reduce the mean color difference in CIELAB from 31.24 to 0.8 and provide a spectral accuracy of 0.0103. Furthermore, a tristimulus color sensor system is developed to verify the performance of these methods. (C) 2015 Elsevier GmbH. All rights reserved.
Fabrication and Configuration Development of Silicon Nitride Sub-Wavelength Structures for Solar Cell Application
(2010-09-01)
Sahoo, Kartika Chandra
;
Chang, Edward Yi
;
Li, Yiming
;
Lin, Men-Ku
;
Huang, Jin-Hua
To replace the double layer antireflection coating and improve the efficiency of solar cell, a self assembled nickel nano particle mask followed by inductively coupled plasma (ICP) ion etching method is proposed to form the sub-wavelength structures (SWS) on silicon nitride (Si(3)N(4)) antireflection coating layers instead of semiconductor layer. The size and density of nickel nano particles can be controlled by the initial thickness of nickel film that is annealed to form the nano-particles on the Si(3)N(4) film deposited on the silicon substrate. ICP etching time is responsible for controlling the height of the fabricated Si(3)N(4) SWS on silicon substrate, which is seen from our experiment. It is found that the lowest average reflectivity of 3.12% for wavelength ranging from 350 to 1000 nm is achieved when the diameter and height of the SWS are 120-180 nm and 150-160 nm, respectively. A low reflectance below 1% is observed over the wavelength from 590 to 680 nm for the fabricated Si(3)N(4) SWS on silicon subs. The efficiency of Si(3)N(4) SWS could be improved by 1.31%, compared with the single layer anti-reflection (SLAR) coatings of Si(3)N(4), using PC1D program. The results of this study may benefit the fabrication of solar cells.
Reflectance of Sub-Wavelength Structure on Silicon Nitride for Solar Cell Application
(2009)
Sahoo, Kartika Chandra
;
Li, Yiming
;
Chang, Edward Yi
;
Lin, Men-Ku
;
Huang, Jin-Hua
In this study, reflection properties of sub-wavelength structures (SWS) on silicon nitride (Si(3)N(4)) antireflective coatings are investigated. Numerical calculation of SWS reflection based on a rigorous coupled-wave approach is conducted and compared with the measurement of fabricated samples. We compare the results of single- and double-layer-antireflection (SLAR and DLAR) coatings with SWS on Si(3)N(4), taking into account average residual reflectivity over a range of wavelengths, where the solar efficiency is further estimated. A low average residual reflectivity of 9.56% could be obtained for a Si(3)N(4) SWS height and non-etched layer of 140 nm and 60 nm respectively, which will be less than 80 nm Si(3)N(4) SLAR (similar to 15%) and almost the same as that of a DLAR with 60 nm Si(3)N(4) and 70 nm magnesium fluoride (similar to 10%).
Design and Fabrication of Sub-Wavelength Structure on Silicon Nitride for Solar Cells
(2009)
Sahoo, Kartika Chandra
;
Li, Yiming
;
Lin, Men-Ku
;
Chang, Edward Yi
;
Huang, Jin-Hua
In this study, we explore the spectral reflectivity of pyramid-shaped silicon nitride (Si3N4) sub-wavelength structures (SWS). First, a multilayer rigorous coupled-wave approach is advanced to investigate the reflection properties of Si3N4 SWS. We first optimize Si3N4 SWS structure for the best effective reflectance properties. The results of our study show that a lowest effective reflectivity of 1.77% can be obtained for the examined Si3N4 SWS with the height of etched part of Si3N4 and the thickness of non-etched layer of 150 nm and 70 nm. Then, we develop a simple and scalable approach for fabricating SWS on silicon nitride by means of self-assembled nickel nano particle masks and inductively coupled plasma ion etching. Silicon nitride SWS surfaces with diameter of 120 nm - 180 nm and a height of 150 nm - 160 nm were obtained for lowest average reflectivity for wavelength range from 190 nm to 1000 nm. A low reflectivity below 1% was observed over wavelength from 600 to 800 nm. The measured reflectivity is closely matched with the simulated results. Using the measured reflectivity data, the solar cell characteristics has further been compared for single layer antireflection coatings and SWS structures and a 1.31% improvement in efficiency was observed.

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