Browse Prior Art Database

Adaptive Calibration of the Scanning/Imaging Systems

IP.com Disclosure Number: IPCOM000117295D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 87K

Publishing Venue

IBM

Related People

Eagle, BC: AUTHOR [+3]

Abstract

The proposed calibration method provides for ability to define the white and black references, mathematically. Thus, a scanner can be customized, via software, to use any off-white and off-black levels as representing the white and black saturation limits, respectively.

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Adaptive Calibration of the Scanning/Imaging Systems

      The proposed calibration method provides for ability to define
the white and black references, mathematically.  Thus, a scanner can
be customized, via software, to use any off-white and off-black
levels as representing the white and black saturation limits,
respectively.

      It is customary to calibrate a scanner using white and black
reference documents, defining the scanner range.  Whether this is
carried out for each pixel of the CCD or segment or a combination
thereof, depends on the technical complexity of the system.  Such a
process compensates for non uniformities of illumination systems,
imaging system, CCD and associated processing.

      Fig. A illustrates, schematically, the implementation of such
system.  The first cell, left of the dotted lines, allows for offset
and gain settings, and therefore conditions the video to be in a
desired range.  The cell on the right sets the black and white
reference for each individual pixel.

      These white and black references are set based on a white and
black target.  As shown in Fig. B, the white and black reference
targets, shown as design white and design black respectively, are not
necessarily total white and total black targets.  Thus a suitable
white and black target can be used to define the white and black
limits of the scanner operation.

      Use of a suitable level of white and black level presents one
difficulty.  Each time one needs to alter the references, e.g., due
to customizaion of scanner to an application, a new set of
calibration targets must be generated.

      This disclosure is aimed toward defining a mathematical process
which allows one to alter the white and black reference without the
need of the altering the corresponding targets.

     ...