Browse Prior Art Database

Dual Speed Data Compression for Optical Scanners

IP.com Disclosure Number: IPCOM000086120D
Original Publication Date: 1976-Jul-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Gaebelein, GN: AUTHOR [+3]

Abstract

In a scanner using a 2048-element linear photodetector array extending across the entire width of a document to be scanned, it is desirable to compress the scan data into a run-length encoded data stream prior to storing the scanned image. The technique shown allows easy conversion between slower and faster scanning speeds, while limiting the compressor for both speeds to that of the slower scanning rate.

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Dual Speed Data Compression for Optical Scanners

In a scanner using a 2048-element linear photodetector array extending across the entire width of a document to be scanned, it is desirable to compress the scan data into a run-length encoded data stream prior to storing the scanned image. The technique shown allows easy conversion between slower and faster scanning speeds, while limiting the compressor for both speeds to that of the slower scanning rate.

Fig. 1 shows a compression channel for the slower scan, in which 8-bit deserialized scanner data 101 is fed in parallel to both inputs LH, RH of format unit 300. Its paralleled outputs B1, B2 are coupled to the CI input of compression unit 400, whose HI input connects to its own C0 output. Compressed data is taken from output RO of unit 400.

The higher speed version of Fig. 2 uses two identical compression units 400. For this version, the scanner is divided into two halves, whose outputs are 1024 bits apart in the same scan. These data streams 201, 202 are coupled to the LH and RH inputs, respectively, of format unit 300. Format output B1 connects to the CI inputs of both compression units 400, while B2 connects to their HI inputs. (The C0 outputs are unused.) The RO outputs of both units 400 are paralleled to provide compressed data stream 203.

In format unit 300, Fig. 3, Ping-Pong buffers 301 store alternate scan lines from inputs LH, RH under the control of selection logic 302. Input in the slow scan mode is from an 8-bit deserialized scan array output that is fed by the full 2048 bit array. In the higher speed version, the input to each buffer is from two 8-bit deserialized scan array outputs, each fed by one half the array.

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