Abstract
A lighting system is proposed for measuring color images under a variety of illumination. This system is constructed with halogen lamps, color filters, white diffusion filters, dimmers, and a personal computer as a controller. Colored light with continuous spectral power distribution is produced based on the additive color mixture of RGB primary lights. First, we describe the method for producing light with a target color stimulus. The basic procedure is performed in two steps of (1) a XYZ-RGB color coordinate conversion and (2) correction of nonlinearity, A practical procedure is presented for easily producing the colored light with any chromaticity coordinates (x, y) specified within the color gamut. We show a method of improving low luminance of the blue region corresponding to high color temperature. Next, the performance of the proposed lighting system is investigated. The accuracy of the colored light is examined on a color difference, and the performance is compared with that of an incandescent lighting system. The goodness is confirmed on the accuracy and the color gamut. Finally, we describe an application of the lighting system to computer vision. The illuminant-spectral distribution and surface-spectral reflectances are estimated from the image data photographed by a multi-band camera.
