Label detector

摘要

A media detector detects the presence of a printed label in a printer which is designed to pause after printing each label, and resume printing only after the printed label has been removed. The detector uses reflected light from an LED, which strikes the print media and is reflected onto a light sensor. The ambiguity caused by ambient light striking the light sensor is avoided by using a two-step detection process. The output from the light detector is read both with the LED on and with the LED off. The status of the light sensor under both conditions is repeatedly analyzed until it is unambiguously determined that the printed label has been removed and the printer can therefore resume printing.