Browse Prior Art Database

Method to Correct Non-Linear Characteristics of Scanner/Printer in Facsimile or Copier Machines

IP.com Disclosure Number: IPCOM000105854D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Thompson, GR: AUTHOR [+2]

Abstract

A bi-level printer or copying machine shown in Fig. 1 includes a scanner or data acquisition arrangement and and a reproducer. The document to be copies is scanned by the scanner which produces a sequence of digital values corresponding to and representing each of a plurality of image elements of the image carried by the document to be copied. The reproducer then reproduces the sequence of image elements on the copy. In a bi-level printer, different gray levels are produced by different patterns of dots and no dots. Non-linearities arise as a result of changes in the digital value produced by the scanner for a fixed gray level.

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Method to Correct Non-Linear Characteristics of Scanner/Printer in Facsimile or Copier Machines

      A bi-level printer or copying machine shown in Fig. 1 includes
a scanner or data acquisition arrangement and and a reproducer.  The
document to be copies is scanned by the scanner which produces a
sequence of digital values corresponding to and representing each of
a plurality of image elements of the image carried by the document to
be copied.  The reproducer then reproduces the sequence of image
elements on the copy.  In a bi-level printer, different gray levels
are produced by different patterns of dots and no dots.
Non-linearities arise as a result of changes in the digital value
produced by the scanner for a fixed gray level.

      A typical data acquisition arrangement, such as is shown in
Fig. 2, produces an illumination beam of intensity L which is imaged
on a document to be copied.  The reflection is sensed by a a sensor
with a characteristics S (light intensity imaged on the sensor versus
voltage out of the sensor), which is coupled to an A/D converter to
produce a digital value N(i).  As the document to be copied moves
past the data acquisition arrangement, a sequence of digital values
N(i) is produced for each of a number of picture elements on the
document to be copied.  The value N(i) for any given picture element
varies because of changes in illuminating light intensity L,
variations in sensor sensitivity S and changes in the A/D converter
char...