Browse Prior Art Database

Laser Shut-Down Circuit for Holographic Scanner

IP.com Disclosure Number: IPCOM000051627D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Cato, RT: AUTHOR [+3]

Abstract

This article describes a control circuit for monitoring the speed of a rotating holographic disc in an optical scanner and for providing failsafe shutdown of the scanner laser even under processor failure conditions.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 56% of the total text.

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Laser Shut-Down Circuit for Holographic Scanner

This article describes a control circuit for monitoring the speed of a rotating holographic disc in an optical scanner and for providing failsafe shutdown of the scanner laser even under processor failure conditions.

The hologram-carrying disc 10 may be glass or a similar lightt-transmitting material. Light from a light-emitting diode (LED)/sensor unit 12 is directed toward the surface of disc 10 at an angle greater than the critical angle and is normally reflected to the sensor section of unit 12. The disc 10 is provided with a light-absorbing or-diffusing spot 14 which interrupts the light beam once per disc revolution. The interval between the interrupts is inversely proportional to the disc speed during that time interval. The output of LED/sensor unit 12 is amplified before being applied to a squaring circuit 16 which digitizes the signal by comparing it to a given threshold level. The output of squaring circuit 16 is applied to the set input of a disc rotation latch 18, to a processor 20 and to a holdover single-shot 22. The digitized signal applied directly to processor 20 serves as a gating or synchronizing signal which is used to establish whether the scanner is reading a diagnostic label secured to the scanner frame or a "live" label, for example, a UPC label on a grocery item being scanned.

Latch 18 is sampled at fixed intervals and is then reset by processor 20. The latch 18 will be set prior to each sam...