Browse Prior Art Database

Incremental Scanning for Facsimile

IP.com Disclosure Number: IPCOM000076693D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Horlander, FJ: AUTHOR

Abstract

This system reduces transmission time of facsimile by "white space skipping". Various implementations of white space skipping have been devised. Most schemes would be better named line skippers, since white space is skipped only if it extends throughout an entire line. However, schemes exist for skipping white space which extends throughout a part of a line.

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Incremental Scanning for Facsimile

This system reduces transmission time of facsimile by "white space skipping". Various implementations of white space skipping have been devised. Most schemes would be better named line skippers, since white space is skipped only if it extends throughout an entire line. However, schemes exist for skipping white space which extends throughout a part of a line.

Referring to the transmitter diagram, Fig. 1, a precision clock 1 drives a programmer 2 consisting of various logic circuits, gates, and a shift register or other memory device which can be read out in serial fashion. The programmer provides various timing waveforms to a scan generator 3, a stepping motor 4 and an analog gate 5. The remainder of the system consists of a flat-bed document holder 6 driven by the stepping motor and a flying spot scanner 7 with phototube pickup 8. The transmitter works as follows: A waveform generated by the programmer causes scan generator 3 to rapidly scan the document 9 via the flying spot scanner 7. Phototube 8 output is sensed by programmer 2. The document line is broken up into numerous segments which are related to the timing of the programmer. As the segments are scanned, the elements of the memory resister are addressed in sequence; if "black" is detected during any segment, the memory element corresponding to the segment is set to a "1", if no "black" is detected during a segment, the corresponding memory element is set to "0". In this fashion, a code is generated of any length desired which describes the information bearing segments of a line. The length of the code is equal to the number of segments desired, for example, if 32 segments are desired then, an 8 1/2'' page would have 32 segments of 0.266 inch. After the complete code is generated, it is transmitted to the receiver unit, Fig. 2, via the data set 10. At the end of this transmission, programmer 2 sends waveforms to scan generator 3 which causes the same document line to be scanned at a slow rate for black line segments, and much faster for white segments. When scanning black segments, the analog gate is switched to allow the black segment to be transmitted; this may be black-white transitions as sensed from text or grey levels, if it is desired to transmit photographic detail. When the line is completed, the scanner is again retraced, document 9 is stepped to the next line, and the sequence is repeated.

The receiver consists of a precision clock 11 of the same frequency as the transmitter clock, a programmer 12 with serial register 12a, a scan generator 13 to control the flying spot scanner 14 and an analog gate 15. The received data may be imaged on a photoconductor drum 16 or some other photosensitive material for further processing.

Assume that the receiver is synchronized to the transmitter at the beginning of each received line segment code. When a black-white line segment code is received, it is stored in serial register 12a. This code...