Reading appts. for data on compact discs or bar codes - uses semi-conductor laser with light emitted via face with anti-reflecting properties that also receives reflected light

摘要

The reader has a semi-conductor laser (6) with an anti- reflecting layer (8) on one face. The laser is supplied (10) with a constant current at a high enough level to ensure the laser emits the light through the face with the anti-reflecting layer. The laser light is focussed by an optical element, placed facing the anti-reflecting layer, onto the support carrying the data. The support is displaced relative to the laser. The light reflected from the data support is focussed back onto the anti-reflecting surface. The potential across the laser varies with incident light, and is measured (14) to detect variations on the surface that are processed to extract the data. ADVANTAGE - Simplified laser reader giving stronger variation in potential than other detectors.