An imaging colorimeter for noncontact skin color measurement

There has been a considerable effort made in several medical fields in the objective color analysis and characterization of biological tissues. Conventional colorimeters have proved inadequate for this purpose, since they do not provide spatial color information and because the measuring procedure randomly affects the color of the tissue. In this paper an imaging colorimeter is presented where the non imaging optical photodetector of the instrument is replaced with a charge-coupled device (CCD) sensor of a color video camera, enabling the independent capture of color information for any spatial point within its field of view. Combining imaging and colorimetry, the acquired image is calibrated and corrected under several ambient light conditions, providing non contact reproducible color measurements free of the errors and limitations present in conventional colorimeters. The technique has been used in hospital clinics for a wide variety of patients. These features highlight the potential of the imaging colorimeters as clinical and research tools for the standardization of clinical diagnosis and the objective evaluation of treatment efficacy.