Longitudinal aberrations caused by optical filters and their compensation in multispectral imaging
Multispectral cameras enable high-fidelity color image acquisition by separation of the electromagnetic spectrum with optical bandpass filters mounted on a filter wheel between optics and imaging sensor. A multispectral image is acquired by capturing one grayscale image per wheel position and combining the images afterwards. Since the optical filters differ in their thicknesses and refraction indices, both transversal (geometric distortions) and longitudinal aberrations (blurring) occur. We present a physical model for the longitudinal aberrations and describe the resulting distortion effects. This knowledge serves as a basis for our compensation algorithm, which performs a shift-variant deconvolution of the image, significantly improving the image quality. We furthermore describe a practicable calibration procedure for our algorithm.