Verification of signal from IR sensor - using data marking read by three channel IR sensor operating on different wavelengths

摘要

The identification of markings on data recordings is enhanced by using three separate infrared detector circuits operating at different wavelengths within the range. A modulated infrared sender produces signals for three transmitter fibre optic bundles. Filter stages ensure that the wave lengths cover different regions of the infrared spectrum. After passing across the markings each signals is received, filtered, demodulated and amplified. The amplified output is compared with a reference amplitude. Only when all signal comparactos produce outputs is clearance given to the identification.