Abstract
The Laser Infrared Reflectometry (LIR) laboratory at NIST includes a facility for the measurement of very low reflectance levels of materials and cavities in the infrared such as those used in high accuracy radiometers and blackbody reference sources. The key elements of the facility are integrating sphere systems, which are used to collect the reflected light from the samples and cavities that are measured. For cavity instruments, the effective emissivity or absorptance can be obtained simply by subtraction of the reflectance from unity. The first sphere system, in operation for the last 5 years, the Complete Hemispherical Infrared Laser-based Reflectometer (CHILR), has been used to examine a large number of blackbody and radiometer cavities. However, it is limited to the measurement of cavities with aperture diameters not exceeding 50 mm. There has been an unmet need for the characterization of larger aperture cavities.
This presentation reports on the status of a new sphere system designed for accurate measurements of cavities with apertures up to 200 mm in diameter. The core of a new setup is a 50 cm integrating sphere with an integrated substitution / port reduction wheel and means for mapping the spatial distribution of reflectance of the object under test. We describe the concept and performance goals of the new capability. We present the first results of its evaluation, including coating properties and throughput evaluation results, which allow estimates of the signal to noise ratio for different laser sources, as well as the minimum discernable reflectance levels of targets. While full implementation of the new capability may require more time and resources, it is available to support the critical needs of the community.
We acknowledge the National Oceanic and Atmospheric Administration (NOAA) Joint Polar Satellite System (JPSS) Program for its support.
New Capability for Evaluating the Emissivity of Large Aperture Infrared Blackbodies
The Laser Infrared Reflectometry (LIR) laboratory at NIST includes a facility for the measurement of very low reflectance levels of materials and cavities in the infrared such as those used in high accuracy radiometers and blackbody reference sources. The key elements of the facility are integrating sphere systems, which are used to collect the reflected light from the samples and cavities that are measured. For cavity instruments, the effective emissivity or absorptance can be obtained simply by subtraction of the reflectance from unity. The first sphere system, in operation for the last 5 years, the Complete Hemispherical Infrared Laser-based Reflectometer (CHILR), has been used to examine a large number of blackbody and radiometer cavities. However, it is limited to the measurement of cavities with aperture diameters not exceeding 50 mm. There has been an unmet need for the characterization of larger aperture cavities.
This presentation reports on the status of a new sphere system designed for accurate measurements of cavities with apertures up to 200 mm in diameter. The core of a new setup is a 50 cm integrating sphere with an integrated substitution / port reduction wheel and means for mapping the spatial distribution of reflectance of the object under test. We describe the concept and performance goals of the new capability. We present the first results of its evaluation, including coating properties and throughput evaluation results, which allow estimates of the signal to noise ratio for different laser sources, as well as the minimum discernable reflectance levels of targets. While full implementation of the new capability may require more time and resources, it is available to support the critical needs of the community.
We acknowledge the National Oceanic and Atmospheric Administration (NOAA) Joint Polar Satellite System (JPSS) Program for its support.