Spectral image processing by a multi-channel camera
Knowledge of such spectral functions as the surface-spectral reflectances of objects in a scene and the illuminant spectral-power distribution is crucial for realizing color constancy, accurate color reproduction, and rendering realistic images. The usual camera system with three channels of RGB has difficulty in estimating the spectral functions because illuminants and surface reflectances in natural scenes are spectrally high-dimensional. A multi-channel camera with more spectral channels than three provides an effective imaging device to estimate the complicated surface and illuminant functions. The present paper proposes a camera system and algorithms for solving this estimation problem from the spectral imaging data. First we present a new multichannel camera system with six spectral channels, which is improved in the dynamic range and image resolution. Then we describe practical algorithms for recovering both the surface spectral reflectances and the illuminant spectrum with accuracy.