Browse Prior Art Database

Camera for Scanning the Grey Level of Both Sides of a Document

IP.com Disclosure Number: IPCOM000112350D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Bruegmann, W: AUTHOR [+3]

Abstract

This article describes a low-cost, front and rear scanning line Change Coupled Device (CCD) camera with colour drop-out. The camera adjusts the brightness of the light source using a dark background and takes the age of the light source into account when calibrating itself.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 56% of the total text.

Camera for Scanning the Grey Level of Both Sides of a Document

      This article describes a low-cost, front and rear scanning line
Change Coupled Device (CCD) camera with colour drop-out.  The camera
adjusts the brightness of the light source using a dark background
and takes the age of the light source into account when calibrating
itself.

      Light rays coming from sources positioned on either side of a
document being scanned as shown in Fig. 1 mutually influence
themselves despite the use of special backgrounds and covers.
Therefore one generally uses only reflections of second or higher
order to charge the elements of the CCD camera.  This minimises the
effects of shadows on the surface of the document which arise because
of creases or unevenness on the document surface.

      The light source in the disclosed device uses an array of LED
(Light Emitting Diode) Cells.  By choosing only cells of a particular
colour from the array, it is possible to create a light source which
is optimally adapted to the document which is to be scanned and to
the uses to which the scanned image of the document is to be put.
Suppose the scanned image is to be used for archiving purposes or the
text on the document has to be read, then experiments have shown that
a green light source on one side of the document and a red light
source on the other side of the document produce optimal images.
Because of the different sensitivities of the CCD camera at different
wavelengths...