Scanner Laser Power Measurement Using Special Diagnostic Label
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
This article describes a technique for measuring the output power of a laser in a bar-code scanner to detect power degradation that is normally a precursor to total laser failure. A special diagnostic label with different shades of bars is mounted in the scanner. The special diagnostic label is periodically read. The results are analyzed to provide an indication of laser power level. An amplifier/threshold card in the scanner must be calibrated at the time of manufacture. A simple way to do this is to flood the photo-sensitive element on the amplifier/threshold card with light of a known level from a calibrated light source. A potentiometer could be used to adjust the gain of the amplifier stages on the card to provide a predetermined peak-to-peak voltage at a test point.