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End Of Document Discriminator

IP.com Disclosure Number: IPCOM000094376D
Original Publication Date: 1966-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Roberts, DC: AUTHOR [+2]

Abstract

In optical character readers which operate on documents, an end-of-document black bar is often printed at the bottom of the documents being scanned. The purpose of the bar is to tell the optical character reader when it may eject the document from the read station. A problem arises when a line of characters is printed immediately adjacent the end-of-document bar. When this last line of characters is being scanned, the line centering circuits in the reader often cause the scanner to center on the end-of-document bar. This prevents recognition of the last line of characters. The discriminator shown solves the problem by inhibiting the line-centering circuits from dragging the scanner away from the characters and into the end-of-document bar.

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End Of Document Discriminator

In optical character readers which operate on documents, an end-of- document black bar is often printed at the bottom of the documents being scanned. The purpose of the bar is to tell the optical character reader when it may eject the document from the read station. A problem arises when a line of characters is printed immediately adjacent the end-of-document bar. When this last line of characters is being scanned, the line centering circuits in the reader often cause the scanner to center on the end-of-document bar. This prevents recognition of the last line of characters. The discriminator shown solves the problem by inhibiting the line-centering circuits from dragging the scanner away from the characters and into the end-of-document bar.

To understand the operation of this discriminator, it is first necessary to understand the scan pattern of the optical scanner. The scanner makes multiple scans transverse to the line of characters. Each of these transverse scans is divided into thirty-nine parts defined thirty-nine equally spaced time intervals. The numerals between one and thirty-nine in the drawing identify these time intervals. A single recognition scan requires thirty-two time intervals. Then for seven time intervals the scanner flies back across the line and moves a few mils down the length of the line in preparation for the next recognition scan through the line.

In operation, the discriminator via And 50 looks for six consecutive black bits at the initial part of a scan. This is accomplished by And 50 passing the indication that six consecutive black bits have arrived prior to the six, seven or eight time of the scan. The output from And 50 sets latch 52. The 1 outputs from latch 52 are counted by counter 54. At time 20 in the scan, latch 52 is reset in preparation for the next scan.

Counter 54 counts fifteen consecutive detections by And 50. If this occurs, the scanner has intercepted the end-of-document bar in fifteen consecutive scans. If during one of the fifteen scans, And 50 does not detect the six consecutive black bits, latch 52 remains reset. Its zero output is then passed by And gate 56 at time 9 resets counter 54 via Or 58. Counter 54 can also be held reset via Or 58 if the scanner is in a search mode.

To prevent...