In-situ pathlength calibration of integrating spheres used in measurement of absorbance
In-situ pathlength calibration of integrating spheres used in measurement of absorbance
复制标题
用于吸光度测量的积分球的原位光程校准
DOI：
10.1117/12.2306655
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
D. Masiyano
中科院分区：
文献类型：
--
作者：
N. Davis;S. Staines;J. Hodgkinson;S. Bergin;D. Francis;R. Tatam;D. Masiyano
When used as samples cells for optical absorbance measurements, integrating spheres offer increased pathlengths compared to single pass cells combined with tolerance to misalignment. This makes them attractive during alignment of optical instruments and in challenging environments subject to vibration. However, integrating spheres can suffer problems when used in sensitive and / or accurate absorbance measurement. We present our work to date to address these issues in high resolution laser spectroscopy. Firstly, optical interference effects include both random laser speckle and structured interference fringes created by optical feedback to the laser. Secondly, the sphere’s optical pathlength is a combination of multiple paths that take an exponential pathlength distribution. At low values of absorbance, the measured signal is linear with concentration, but at higher absorbances signals follow a nonlinear but predictable function of absorbance. Thirdly, our most recent work concerns calibration of the optical pathlength, which is a sensitive function of its internal reflectivity. In-situ calibration is needed if the sphere is to be used in dirty environments or with condensing samples. Measurements from multiple independent sources and / or detectors are combined to provide compensation from fouling of the sphere walls and windows. Results are presented for an integrating sphere used in the measurement of methane. The emission from a tunable DFB laser at 1651nm was tuned across the gas absorption line to measure its concentration. Reduced sphere reflectivity was simulated by applying small areas of black tape on the inner surface. Finally, we give an example of one application where our results are being put into practice: use of an integrating sphere with a tunable laser at 3.3μm to measure atmospheric methane, installed on a two seater light aircraft.
基于气体单元的积分腔：用于路径长度变化的多光束补偿方案。
影响因子：
3.8
作者：
Bergin S
通讯作者：
Bergin S