DYNAMIC REFERENCE FOR AN IMAGE QUALITY CONTROL SYSTEM

DYNAMIC REFERENCE FOR AN IMAGE QUALITY CONTROL SYSTEM A system for checking copy quality variables within the image area of an electrophotographic machine. During a test cycle, quality is checked by producing sample test areas within the photoconductor image area ordinarily used for producing copies. Reflectance measurements are made on the sample test areas and compared to a dynamically floating reference achieved by a reflectance measurement from a cleaned portion of the photoconductor within the image area. The testing circuit is balanced so that the same reflectance voltage should be generated whether the single reflectivity-sensing device is viewing a sample test area or a cleaned reference area. The system checks for quality variables such as toner concentration, image voltage and an abnormally low reflectance photoconductor and provides a partial check on its own fault-free condition during periods when it is not in use.