Browse Prior Art Database

Pulse-Train-Mode Optical Scanner

IP.com Disclosure Number: IPCOM000047317D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Dickson, LD: AUTHOR

Abstract

This article describes an optical scanner in which the scanning laser would operate in a pulse-train mode. Selection of the proper duty cycle would allow government regulations regarding exposure to be met without timer/accumulator circuitry. The need for item sensors would be eliminated, and ambient light rejection would be improved. Semiconductor lasers can be operated in a pulse-train mode with very narrow pulse widths and very high pulse repetition frequencies. In a bar code scanner, a semiconductor laser could operate in a pulse-train mode continuously. If the pulse train had a 10% duty cycle (10% on, 90% off), current government regulations regarding exposure to laser light at a given point would be met without any requirement for timers/accumulators.

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Pulse-Train-Mode Optical Scanner

This article describes an optical scanner in which the scanning laser would operate in a pulse-train mode. Selection of the proper duty cycle would allow government regulations regarding exposure to be met without timer/accumulator circuitry. The need for item sensors would be eliminated, and ambient light rejection would be improved. Semiconductor lasers can be operated in a pulse- train mode with very narrow pulse widths and very high pulse repetition frequencies. In a bar code scanner, a semiconductor laser could operate in a pulse-train mode continuously. If the pulse train had a 10% duty cycle (10% on, 90% off), current government regulations regarding exposure to laser light at a given point would be met without any requirement for timers/accumulators. Since the laser would operate continuously, there would be no need for item sensors. Finally, the operation of the photo-detector component in the scanner would be synchronized with the operation of the semiconductor laser. That is, the photo-detector would be enabled at the same time as the semiconductor laser. Typical pulse widths could be on the order of 10 nanoseconds. A suitable pulse repetition frequency would be on the order of 10 megahertz. These parameters would assure that at least 10 pulses would occur during the time required for the scanning beam to cross the minimum anticipated module (bar or space) in a label being scanned.

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