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Synchronized Moving Illuminator for Camera-Type Image Scanners

IP.com Disclosure Number: IPCOM000119631D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Giordano, FP: AUTHOR [+2]

Abstract

Disclosed is an improved illuminator scheme designed to provide efficient illumination at reduced lamp power to camera-type scanners in which the scanning operation is accomplished by moving the imager mechanically across the image plane inside the camera. It is applicable to cameras using linear CCDs, TDI-CCDs or other kinds of line imagers.

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Synchronized Moving Illuminator for Camera-Type Image Scanners

      Disclosed is an improved illuminator scheme designed to
provide efficient illumination at reduced lamp power to camera-type
scanners in which the scanning operation is accomplished by moving
the imager mechanically across the image plane inside the camera.  It
is applicable to cameras using linear CCDs, TDI-CCDs or other kinds
of line imagers.

      In a camera-type scanner design, the document and optics are
stationary.  The scanning is done by moving the imager across the
image plane with a sliding platform driven by a precision lead screw
and stepping motor.  In a conventional design, illumination is
provided uniformly over the entire document area, both for reflective
documents and transmissive documents, in a manner similar to that of
a copy camera set-up.  The illumination must be uniform in intensity
over the entire area, especially for high quality images, and usually
requires high lamp power due to the area requirement.

      It is possible to improve the uniformity and reduce the lamp
power of the illumination by placing the illuminator closer to the
documents and moving it synchronously with the movement of the
imager, as shown in Fig. 1.  The speed and the travel distance of the
illuminator assembly is determined (and can be controlled by a host
controller CPU) by (a) the distance between the document and the
camera lens, (b) the speed of the imaging device, (c) the document
...