Methods for spectral characterization of multispectral cameras

High fidelity color image acquisition requires an accurate characterization of the camera’s spectral sensitivity curves to perform color calibration or spectral estimation. Several methods have been proposed to perform this task; these include characterizations via test charts, narrowband filters and methods utilizing a monochromator. In most publications, RGB cameras are characterized. In this paper, we describe the characterization of the spectral sensitivity curves of a multispectral camera featuring seven optical bandpass filters. We show two different methods for the calibration using a monochromator – either by measuring the grayscale sensor of the camera and the filters separately or by characterizing the multispectral camera as a complete system. A comparison of both methods validates the measurement results. We furthermore develop different reconstruction methods (maximum value method, principal eigenvector method, linear or Wiener estimation). We perform also simulations of the characterization process to evaluate the methods and show the impact of the bandwidth of the monochromator stimuli on the reconstruction.