[OPTICAL REVIEW Vol. 4, No. 6 (1997) 707-712]
Recovery of Surface Reflectances Using Video Camera Image Signals under Unknown Illuminations
Noriyuki SHIMANO
Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashi-osaka, Osaka, 577 Japan
(Received July 14, 1997; Accepted October 22, 1997)
Estimation of surface spectral reflectance functions and colorimetric values of object colors was carried out for the image data captured by video camera under unknown illuminations. The estimation method is based on the finite-dimensional linear model of illuminants and surfaces using a single reference reflectance with known surface spectral reflectance in a scene. Experimental results showed that recovered surface spectral reflectance functions are the almost same for different illuminations. This method is useful for the colorimetric calibration of the devices, since any set of orthonormal basis vectors to represent illuminations and any set of eigen vectors derived from principal component analysis on the data set of a color chart to express surfaces of different objects can be applied to the estimation. The recovered surface reflectances were evaluated by color differences in CIE L*a*b* color space.
Key words : device independent color reproductions, colorimetric calibration, computational color constancy, colorimetric values, image acquisition, image recovery