EP0200438A2
Expired / Lapsed
EP
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Digital reading device for facsimile apparatus
Assignee: Olivetti SpA
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Filing: 1986-04-18
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Granted: —
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Expires: 2006-04-18
Abstract
Abstract The charge coupled device (23) provides serialised signals from a line of a document to an A/D converter (28). In order to compensate for factors such as non-uniformity of lighting, non-uniformity of CCD cell response and variations with time, a reference strip is read before each reading of a document and the corresponding digital values are stored in a RAM (31). Thereafter the stored values and the values read from each line of the document are compared to provide compensated values to a half tone generator (42) which codes the output. In particular, the comparison is effected by means of an ROM (32) addressed in part by the digital value derived from a pixel in the line of the document and in part by the digital value stored in the RAM (31) from the corresponding pixel in the reference strip. The values held in the ROM (32) correspond to the ratio between the addressing values. The ROM (32) may have modules for each of a plurality of different colours selected by a multiplexer (41) in correspondence with the selection of a filter determining the scanning colour. The reference strip is scanned through each filter before the document is scanned to determine the values in the RAM (31).
Inventors
- 👤 Ferdinando Augusti
- 👤 Luigi Bonatto
- 👤 Anna Maria Puglisi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 15:32
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/401
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
176 words
A digital reading device for facsimile apparatus, comprising a light source (14) for illuminating the document to be read, means (17, 19, 21, 22) for directing the image of a line of the document thus illuminated on to a series of reading elements (23) for generating a series of response signals in response. to the points read along the line, an A/D converter (28) operative on the response signals to provide digital signals, and means (42) for coding the intensity of the digital signals according to a half tone scale, characterised by means (31) for storing the signals obtained from the A/D converter (31) in a preliminary reading of a calibrated background (29), and comparison means (32) responsive to the signals obtained from the A/D converter (2R) in the reading of the document and the signals thus stored, the coding means (42) effecting the coding of the intensity of the digital signals in response to the comparison means, whereby variation of the transfer function of the device with time and from pixel to pixel is compensated.
Claim 2
Dependent Claim
176 words
A digital reading device for facsimile apparatus, comprising a light source (14) for illuminating the document to be read, means (17, 19, 21, 22) for directing the image of a line of the document thus illuminated on to a series of reading elements (23) for generating a series of response signals in response. to the points read along the line, an A/D converter (28) operative on the response signals to provide digital signals, and means (42) for coding the intensity of the digital signals according to a half tone scale, characterised by means (31) for storing the signals obtained from the A/D converter (31) in a preliminary reading of a calibrated background (29), and comparison means (32) responsive to the signals obtained from the A/D converter (2R) in the reading of the document and the signals thus stored, the coding means (42) effecting the coding of the intensity of the digital signals in response to the comparison means, whereby variation of the transfer function of the device with time and from pixel to pixel is compensated.
Claim 3
Dependent Claim
66 words
A device according to claim 1, wherein the said directing means comprise at least one mirror (17, 19, 21) and an objective (22) and the reading elements (23) comprise a series of cells of a charge coupled device (CCD), characterised in that the compensation compensates for the combined effects of the light source (14), the mirrors (17, 19, 21), the objective (22) and the CCD (23).
Claim 4
Dependent Claim
86 words
A device according to claim 1 or 2, characterised in that the calibrated background is constituted by a sample strip (29) arranged in a position adjacent to the document to be read, which is read by the reading elements (23) immediately before the reading of the document, the comparison means (32) effecting each time the comparison between the signals obtained by the AID converter (28) in the reading of one line of the document with the signals stored in the reading of the sample strip (29).
Claim 5
Dependent Claim
48 words
A device according to claim 3, characterised in that the storing means (31) comprise a read-write memory and the comparison means (32) comprise a read only memory at each address of which there is stored in advance a value corresponding to the compensated signal corresponding to the comparison.
Claim 6
Dependent Claim
40 words
A device according to claim 4, characterised in that the stored value is proportional to the ratio between the direct reading signal of a pixel and that recorded in the preliminary reading of the corresponding pixel of the sample strip.
Claim 7
Dependent Claim
51 words
A device according to claim 5, characterised in that the read only memory (32) is addressed in part the digital signals of a given pixel and in part by the digital signals stored in the read-write memory (31) in the preliminary reading of the corresponding pixel of the sample strip (29).
Claim 8
Dependent Claim
56 words
A device according to claim 6, characterised in that the value stored in the read only memory is obtained by multiplying a number equal to the number of the desired levels of grey by the ratio between the value of the direct reading and the value of the preliminary reading, expressed by the respective address signals.
Claim 9
Dependent Claim
68 words
R. A device according to any of claims 4 to 7, comprising a plurality of filters (24) for the reading of images in colour, characterised in that the preliminary reading is effected on the sample strip (29) with the same filter (24) with which the document is read, the said coding being effected in successive readings of the document, whereby the compensation is effected for all the colours.
Claim 10
Dependent Claim
46 words
A device according to claim 8, characterised in that the read only memory (32) comprises a series of modules each associated with a filter colour, the modules being addressed in parallel, and the output data being selected (41) on the basis of the chosen filter (24).
Claim 11
Dependent Claim
67 words
A device according to claim 7 and claim R or 9, in which the signals of grey can be used by a variety of graphic appartuses, characterised in that a plurality of read only memories (32) are associated with the different apparatuses and are selectable individually for operation, the values stored in each read only memory being multiplied by a factor corresponding to the associated graphic apparatus.
References Cited (Backward Citations)
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