Patent US 6,038,331

An apparatus and method for monitoring hand washing wherein a subject's hands are checked after he or she has applied soap or detergent and spread it over the front and back of his or her hands. An optical image of the subject's hands is digitized and compared, pixel by pixel, with a reference feature that distinguishes the soap and a report is generated indicating whether the subject's hands are covered with enough soap or detergent to receive a satisfactory report.