Development of an Imaging Colorimeter for Noncontact Tissue Color Measurement

Abstract

Considerable effort has been made in several medical fields to achieve objective color analysis and characterization of biological tissues. Conventional colorimeters have proved inadequate for this purpose, because they do not provide spatial color information and because the measuring procedure randomly affects the color of the tissue. This paper describes an imaging colorimeter in which the nonimaging optical photodetector of colorimeters is replaced with the charge-coupled device (CCD) sensor of a color video camera, enabling the independent capturing of the color information for any spatial point within the camera's field of view. Combining imaging and colorimetry methods, the acquired image is calibrated and corrected under several ambient light conditions, providing noncontact reproducible color measurements, free of the errors and limitations of conventional colorimeters. Skin color was evaluated individually on three cutaneous areas: forehead (exposed area), chin (semi-exposed area), and armpit (non-exposed area). The colorimeter appears to be a simple and accurate device for objectively measuring skin color. Its features highlight the potential of the imaging colorimeter as a clinical and research tool for the standardization of clinical diagnosis and for the objective evaluation of treatment effectiveness.