Browse Prior Art Database

Scanner Laser Power Measurement Using Special Diagnostic Label

IP.com Disclosure Number: IPCOM000041375D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Broockman, EC: AUTHOR [+2]

Abstract

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.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 80% of the total text.

Page 1 of 1

Scanner Laser Power Measurement Using Special Diagnostic Label

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. The scanner would include a special diagnostic label mounted inside the scanner at one edge of the scan window. Current scanners include a label which basically consists of a Universal Product Code (UPC)-type bar-coded label in which the characters have known values. The special label would include the UPC-type label but would also include a series of bars of uniform width but differing gray scale values. When the special diagnostic label is scanned with a laser having a suitable output power level, the UPC section of the diagnostic label would be detected along with all of the special bars. If the laser power level were to fall belo...