1 September 2009 Development of an infrared optical scattering instrument from 1 μm to 5 μm
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Abstract
The wavelength coverage of the IR optical scattering instrument developed at the National Institute of Standards and Technology has been extended to cover the continuous range from 1 μm to 5 μm. Besides the previously available diode lasers at wavelengths of 785 nm, 1.32 μm, and 1.55 μm as well as a line tunable CO2 lasers from 9.2 μm to 11.2 μm, a PPLN OPO tunable laser is used to generate the desired IR source radiation from 1 μm to 5 μm. We present a brief description of the existing BRDF instrument, as well as the steps required to couple the tunable IR source into the BRDF system, such as improvement of beam profile, polarization control, and sample alignment. The associated results of BRDF measurements for typical specular and diffuse samples are also shown. For specular samples, the BRDF collection aperture size is varied to both 1) resolve the specular component and 2) obtain sufficient signal for the low level diffuse component. The input beam is characterized directly by a pyroelectric sensor array camera in comparison to the BRDF results. The dynamic range of detection, sample alignment, and the averaging of multiple spots for the specular sample measurement are discussed. For diffuse samples, the approach employed for speckle suppression is a combination of translation and rotation averaging. The directional-hemispherical reflectance (DHR) is calculated by integration of the BRDF data, which is found to have good agreement with the DHR results from FTIR integrating sphere measurements.
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Jinan Zeng, Leonard Hanssen, "Development of an infrared optical scattering instrument from 1 μm to 5 μm", Proc. SPIE 7453, Infrared Spaceborne Remote Sensing and Instrumentation XVII, 74530Q (1 September 2009); doi: 10.1117/12.829580; https://doi.org/10.1117/12.829580
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