Spectral characterization of black materials for use as background in spectrometric laboratories

ABSTRACT

This paper describes a study aimed at the assessment of low-reflectance equipment in a laboratory using spectral measurements. The use of reflectance spectrometers is common for the detection of soils, minerals, vegetation, and manmade materials, but comparability remains questionable. It is well-known that several factors can have profound effects on measured reflectance spectra. In this paper, we present a low-reflectance material that eliminates the impact of light effects from sample backgrounds or the equipment and walls of dark chambers. For laboratory spectral measurements, two different setups (changes in geometry) of the experimental design with ASD FieldSpec Pro were performed. Overall, 23 visible black materials were measured. Statistical analysis revealed that only three materials were useful for the investigated topic. These materials (foam rubber, cellulose fleece, and thermal coating) exhibit low reflection, below 10%, are flat and featureless in the spectral curve and have low spectral variation by rotation. In contrast, 20 other materials showed either low reflectance in visible light, a high spectral variation by rotation or in the second setup, high specular radiation. The results indicated that in certain cases, laboratory reflectance measurements made by a non-qualified background material were not truly reproducible or suitable for a spectral library. This experiment demonstrates a problem in laboratory scenarios involving remote sensing working groups, helps to place our measurements in context, and forms the basis for comparison with other studies.

KEYWORDS:

• Background
• low-reflectance materials
• metadata standards
• spectrometric laboratory

Acknowledgments

The authors thank Michael Denk for assistance with the spectrometer technique and laboratory measurements that were part of this study.