Browse Prior Art Database

Sensing Reading Readiness for Manual Code Reader

IP.com Disclosure Number: IPCOM000077234D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Ett, AH: AUTHOR [+3]

Abstract

This system is applicable to probes or pens used for reading information from bar-code patterns. It consists of a means for detecting the proximity between a probe 2 and a document 4, by the shift in light level of the sensing system when the probe is brought into close proximity, without loss of this activation when code marks are encountered during a slow-reading process. As shown in the block diagram of Fig. 1, the DC level resulting from the directly coupled output of photosensor 6 after amplification 8, is sensed by a threshold circuit 10. A shift in the signal indicates an increase in reflectance and activates a read-enable latch 9.

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Sensing Reading Readiness for Manual Code Reader

This system is applicable to probes or pens used for reading information from bar-code patterns. It consists of a means for detecting the proximity between a probe 2 and a document 4, by the shift in light level of the sensing system when the probe is brought into close proximity, without loss of this activation when code marks are encountered during a slow-reading process. As shown in the block diagram of Fig. 1, the DC level resulting from the directly coupled output of photosensor 6 after amplification 8, is sensed by a threshold circuit 10. A shift in the signal indicates an increase in reflectance and activates a read-enable latch 9. Simultaneously the illumination source 14, which may be either an incandescent lamp or alternatively a light-emitting diode, is brightened by electronically decreasing the series resistance in the lamp supply by lamp current control 12. This in turn provides a larger output bias level shift, so that the decrease in level when crossing the code marks at low speed does not permit the level to fall below the threshold value. This maintains a "lock on" condition of the ready signal, requiring a deliberate probe withdrawal which exceeds the excitation distance from the document by a factor of several times for the ready latch to fall, indicating that the reading operation has been completed.

Waveforms 5 associated with this technique are illustrated in Figs. 2a-2d. In 2a, the probe 2 i...