Browse Prior Art Database

Dual Path Item Sensor and Control Circuit

IP.com Disclosure Number: IPCOM000051628D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Cato, RT: AUTHOR [+2]

Abstract

The drawing shows a dual-path item sensor for a supermarket-type scann and a control circuit for operating that sensor in a self-adjusting, pulsed mode.

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Dual Path Item Sensor and Control Circuit

The drawing shows a dual-path item sensor for a supermarket-type scann and a control circuit for operating that sensor in a self-adjusting, pulsed mode.

The item sensor includes a light source 10, such as a light-emitting diode, and a light detector 12, such as a phototransistor. Both source 10 and detector 12 are located on the same side of a checkout stand surface 14. The source 10 and detector 12, in combination with a pair of mirrors 20 and 22, form an item sensor which provides a signal indicating that an item to be scanned is approaching a scanner window 16 in a direction indicated by arrow 18. This signal is used to release a laser shutter so that a scan pattern is generated above the surface 14 in the vicinity of scanner window 16. In the arrangement shown, there are two beam paths 24 and 26. Interruption of either of these paths will result in the generation of an item present signal.

The output of the light detector 12 may be applied to an AC coupled amplifier 28, the output of which is applied both to a threshold circuit 30 and to a feedback amplifier 32. The signal produced by amplifier 28 is compared to a fixed threshold value in the threshold circuit 30 to produce an item-indicating signal only where the signal level is shifted by more than a predetermined amount. Any signal generated in threshold circuit 30 is passed to an output shaper circuit 34 which generates an output signal for delivery to a scanner controlling processor.

The output of feedback amplifier 32 is applied to a driver circuit 36 which drives the light source 10 in a pulsed mode at a rate determined by a clock generator 38. By operating the light source...