Abstract: A microprocessor controlled currency note validator includes a transport for propelling an inserted note longitudinally past an optical scanning station. Infrared and visible color reflectance readings and opacity readings are taken along several longitudinally extending tracks on the note. The microprocessor normalizes the reflectance readings to accommodate for variations in soiling and compares the normalized reflectance readings and the opacity readings against stored acceptance band data, correcting for pattern registration variations if necessary. The length of the note is also checked and a validation signal is provided if the note passes the optical tests and the length test. During the idle cycle, the microprocessor automatically adjusts the optical circuitry to compensate for component drift and dirt buildup. The microprocessor also provides a visual display of any detected malfunctions.