Compensation of color shift due to the multiple reflection of illumination in CCD endoscopic color measurement .1. principle and basic experiment

We propose a method to compensate a change of illumination for color measurement of the mucous membrane of human internal organs from CCD endoscopic images, which are captured under the circumstances where the spectral distribution of the illumination on the object changes due to the multiple reflections of the illumination light. In this method, the surface reflectance of the mucous membrane and the spectral distribution of the illumination are represented by a weighted sum of some basis functions given by the statistical analysis of the surface reflectances, and each weighting factor is estimated from endoscopic image data. Through a basic experiment using a CCD endoscope and color charts, the effectiveness of the proposed method is confirmed. (C) 1997 Elsevier Science B.V.