Characterization of Integrating Sphere Homogeneity with an Uncalibrated Imaging Spectrometer

Abstract

The radiometric calibration of imaging spectrometers is usually performed using integrating spheres as light sources. Their homogeneities are usually defined for the entrance aperture. As airborne hyperspectral sensors are focused on infinity, the calibration of such sensors is done in a way which is not well defined. In this paper, a method is shown which allows the characterization of integrating spheres with a radiometrically uncalibrated hyperspectral sensor. The sphere is characterized in the same way as it is used for the calibration of hyperspectral sensors. This allows the determination of the relative uncertainty of radiometric measurements due to inhomogeneities. Also, the relative radiometric response of the sensor can be derived at the same time. The method is demonstrated exemplarily with a HySpex VNIR-1600, an airborne imaging spectrometer system from Norsk Elektro Optikks A/S (NEO).