Scientific Characterization of Light and Light Sources

2010 ◽  
pp. 257-282
Keyword(s):  
Light Sources

scholarly journals Assessing the Stability of Surface Lights for use in Retrievals of Nocturnal Atmospheric Parameters

2019 ◽  
Author(s):  
Jeremy E. Solbrig ◽  
Steven D. Miller ◽  
Jianglong Zhang ◽  
Lewis Grasso ◽  
Anton Kliewer
Keyword(s):  
Near Infrared ◽  
Correlation Coefficients ◽  
Visible Spectrum ◽  
Light Sources ◽  
Infrared Observations ◽  
Spatially Resolved ◽  
Relative Standard ◽  
Geometric Variables ◽  
The Stability

Abstract. Detection and characterization of aerosols is inherently limited at night due to a lack of sensitivity—information typically provided by visible spectrum observations. The VIIRS Day/Night Band (DNB) onboard the Suomi-NPP satellite is a first-of-its-kind calibrated sensor capable of collecting visible/near-infrared observations during both day and night. Multiple studies have suggested that anthropogenic light emissions such as those from cities and gas flares may be useable as light sources for retrieval of atmospheric properties including cloud and aerosol optical depth. However, their use in this capacity requires proper characterization of their intrinsic variation, which represents a source of retrieval uncertainty. In this study we use 18 months of cloud-cleared VIIRS data collected over five selected geographic domains to assess the stability of anthropogenic light emissions and their response to varied satellite and lunar geometries. Timeseries are developed for each location in each domain for DNB radiance, four infrared channels, and satellite and lunar geometric variables, and spatially-resolved correlation coefficients are computed between DNB radiance and each of the other variables. This analysis finds that while many emissive light sources are too unstable to be used reliably for atmospheric retrievals, some sources exhibit a sufficient stability (relative standard deviation

scholarly journals Source–Detector Spectral Pairing-Related Inaccuracies in Pulse Oximetry: Evaluation of the Wavelength Shift

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3302
Author(s):  
Olivier Tsiakaka ◽  
Benoit Gosselin ◽  
Sylvain Feruglio
Keyword(s):  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Optical Characterization ◽  
Absolute Error ◽  
Wavelength Shift ◽  
Light Sources ◽  
Performance Requirements ◽  
Processing Power ◽  
Key Features

Pulse oximetry enables oxygen saturation estimation ( S p O 2) non-invasively in real time with few components and modest processing power. With the advent of affordable development kits dedicated to the monitoring of biosignals, capabilities once reserved to hospitals and high-end research laboratories are becoming accessible for rapid prototyping. While one may think that medical-grade equipment differs greatly in quality, surprisingly, we found that the performance requirements are not widely different from available consumer-grade components, especially regarding the photodetection module in pulse oximetry. This study investigates how the use of candidate light sources and photodetectors for the development of a custom S p O 2 monitoring system can lead to inaccuracies when using the standard computational model for oxygen saturation without calibration. Following the optical characterization of selected light sources, we compare the extracted parameters to the key features in their respective datasheet. We then quantify the wavelength shift caused by spectral pairing of light sources in association with photodetectors. Finally, using the widely used approximation, we report the resulting absolute error in S p O 2 estimation and show that it can lead up to 8% of the critical 90–100% saturation window.

scholarly journals Characterization of the Uniformity of High-Flux CdZnTe Material

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2747 ◽  
Author(s):  
Matthew Charles Veale ◽  
Paul Booker ◽  
Simon Cross ◽  
Matthew David Hart ◽  
Lydia Jowitt ◽  
...  
Keyword(s):  
Flip Chip ◽  
Temporal Stability ◽  
Light Sources ◽  
High Flux ◽  
X Ray Imaging ◽  
Science Community ◽  
Cdznte Detectors ◽  
Photon Science ◽  
Synchrotron Light Sources

Since the late 2000s, the availability of high-quality cadmium zinc telluride (CdZnTe) has greatly increased. The excellent spectroscopic performance of this material has enabled the development of detectors with volumes exceeding 1 cm3 for use in the detection of nuclear materials. CdZnTe is also of great interest to the photon science community for applications in X-ray imaging cameras at synchrotron light sources and free electron lasers. Historically, spatial variations in the crystal properties and temporal instabilities under high-intensity irradiation has limited the use of CdZnTe detectors in these applications. Recently, Redlen Technologies have developed high-flux-capable CdZnTe material (HF-CdZnTe), which promises improved spatial and temporal stability. In this paper, the results of the characterization of 10 HF-CdZnTe detectors with dimensions of 20.35 mm × 20.45 mm × 2.00 mm are presented. Each sensor has 80 × 80 pixels on a 250-μm pitch and were flip-chip-bonded to the STFC HEXITEC ASIC. These devices show excellent spectroscopic performance at room temperature, with an average Full Width at Half Maximum (FWHM) of 0.83 keV measured at 59.54 keV. The effect of tellurium inclusions in these devices was found to be negligible; however, some detectors did show significant concentrations of scratches and dislocation walls. An investigation of the detector stability over 12 h of continuous operation showed negligible changes in performance.

scholarly journals Reduced Graphene Oxide–P25 Nanocomposites as Efficient Photocatalysts for Degradation of Bisphenol A in Water

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 607 ◽  
Author(s):  
Fei Yu ◽  
Xueting Bai ◽  
Changfu Yang ◽  
Lijie Xu ◽  
Jie Ma
Keyword(s):  
Graphene Oxide ◽  
Bisphenol A ◽  
Reduced Graphene Oxide ◽  
Catalytic Effect ◽  
Light Sources ◽  
Solution Ph ◽  
Sunlight Irradiation ◽  
Practical Applications ◽  
Reduced Graphene

Reduced graphene oxide–titanium dioxide photocatalyst (rGO–TiO2) was successfully synthesized by the hydrothermal method. The rGO–TiO2 was used as photocatalyst for the degradation of bisphenol A (BPA), which is a typical endocrine disruptor of the environment. Characterization of photocatalysts and photocatalytic experiments under different conditions were performed for studying the structure and properties of photocatalysts. The characterization results showed that part of the anatase type TiO2 was converted into rutile type TiO2 after hydrothermal treatment and 1% rGO–P25 had the largest specific surface area (52.174 m2/g). Photocatalytic experiments indicated that 1% rGO–P25 had the best catalytic effect, and the most suitable concentration was 0.5 g/L. When the solution pH was 5.98, the catalyst was the most active. Under visible light, the three photocatalytic mechanisms were ranked as follows: O2•− > •OH > h+. 1% rGO–P25 also had strong photocatalytic activity in the photocatalytic degradation of BPA under sunlight irradiation. 1% rGO–P25 with 0.5 g/L may be a very promising photocatalyst with a variety of light sources, especially under sunlight for practical applications.

Characterization of Wavelength-Tunable Quantum Dot External Cavity Laser for 1.3-$\mu$m-Waveband Coherent Light Sources

2012 ◽  
Vol 51 (2) ◽  
pp. 02BG08 ◽  
Author(s):  
Naokatsu Yamamoto ◽  
Kouichi Akahane ◽  
Tetsuya Kawanishi ◽  
Hideyuki Sotobayashi ◽  
Yuki Yoshioka ◽  
...  
Keyword(s):  
Quantum Dot ◽  
External Cavity ◽  
Light Sources ◽  
Coherent Light ◽  
External Cavity Laser ◽  
Wavelength Tunable ◽  
Cavity Laser

scholarly journals Design and performance of a three-wavelength LED-based total scatter and backscatter integrating nephelometer

2010 ◽  
Vol 3 (6) ◽  
pp. 4835-4864 ◽  
Author(s):  
T. Müller ◽  
M. Laborde ◽  
G. Kassell ◽  
A. Wiedensohler
Keyword(s):  
Signal To Noise Ratio ◽  
Ambient Air ◽  
Light Sources ◽  
Light Emitting ◽  
Sensitivity Functions ◽  
A Value ◽  
Commercial Instrument ◽  
And Performance ◽  
Comparison Measurements

Abstract. Integrating nephelometers are instruments that directly measure a value close to the light scattering coefficient of airborne particles. Different models of nephelometers have been used for decades for monitoring and research applications. Now, a series of nephelometers (Ecotech models M9003, Aurora 1000 and Aurora 3000) with newly designed light sources based on light emitting diodes are available. This article reports on the design of these integrating nephelometers and a comparison of the Aurora 3000 to another commercial instrument (TSI model 3563) that uses an incandescent lamp. Both instruments are three-wavelength, total and backscatter integrating nephelometers. We present a characterization of the new light source design of the Aurora 3000 and provide parameterizations for its angular sensitivity functions. These parameterizations facilitate to correct for measurement artefacts using Mie-theory. Comparison measurements against the TSI 3563 with laboratory generated white particles and ambient air are shown and discussed. Both instruments agree well within the calibration uncertainties and detection limit for total scattering with differences less than 5%. Differences for backscattering are higher by up to 11%. Highest differences were found for the longest wavelengths, where the signal to noise ratio is lowest. Differences at the blue and green wavelengths are less than 4% and 3%, respectively, for both total and backscattering.

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