Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Reexamination Certificate
1998-11-30
2001-09-11
Grant, II, Jerome (Department: 2722)
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
C382S275000, C382S274000
Reexamination Certificate
active
06288798
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention is directed to apparatus and methods that compensate for show-through of images from a back side of a translucent image bearing substrate when scanning the images.
2. Description of Related Art
When a user wishes to reproduce an image on an image bearing substrate or obtain an electronic version of the image on the image bearing substrate, the image bearing substrate on which the image is formed is passed within a detection field of an optical sensor. The passing of the image bearing substrate within the detection field of the optical sensor is termed “scanning” the image bearing substrate. The optical sensor detects light reflected from the surface of the image bearing substrate and obtains data representing the reflected light. The data obtained is an electronic representation of the images formed on the image bearing substrate, because the colors and shadings of the images on the image bearing substrate reflect different amounts and wavelengths of light.
When a double-sided translucent image bearing substrate, having images on both sides of the image bearing substrate, is scanned, the electronic representation generated by scanning one side of the image bearing substrate will contain information from both sides of the image bearing substrate due to light passing through the image bearing substrate. The high contrast image information of the scanned side, or front, of the image bearing substrate will be combined with the low contrast image information from the back side of the image bearing substrate. This low contrast image information from the back side of the image bearing substrate is called “show-through” image information.
One way in which show-through image information is reduced is to place a black backing on the back side of the image bearing substrate during scanning. The light that passes through the image bearing substrate is absorbed by the black backing. Although there is a significant reduction of the show-through image information, there is a small residual low contrast image of the back side remaining in the scanned image due to light scattering off the back side of the image bearing substrate.
Additionally, this method is undesirable because with a black backing any perforations in the image bearing substrate and regions beyond the edges of the image bearing substrate appear as black regions in the scanned image.
SUMMARY OF THE INVENTION
This invention provides apparatus and methods that compensate for show-through of images from a backside of a translucent image bearing substrate when reproducing the images.
Image reflectance data for a front side and back side of an image bearing substrate is obtained from an optical sensor that senses light reflected from an image bearing substrate. The image reflectance data is stored in a memory and is used to determine scanned density data and approximate absorbency data for the front side and the back side of the image bearing substrate.
In accordance with an imaging model proposed here, show-through compensated density data for the front side image is obtained by subtracting a low pass filtered version of the back side absorbency data from the scanned density data for the front side. Likewise, show-through compensated density data for the back side image is obtained by subtracting a low pass filtered version of the front side absorbency data from the scanned density data for the back side. A point spread function for the low pass filter is estimated either statically or adaptively in accordance with standard linear prediction theory. The show-through compensated density data for the two sides may be transformed back to show-through compensated reflectance data for each side.
The adjusted image data may then be stored in memory for later use when reproducing the image. In this manner, a reproduced image with no show-through may be obtained.
REFERENCES:
patent: 5646744 (1997-07-01), Knox
patent: 5832137 (1998-11-01), Knox
Simon Haykin, “Adaptive Filter Theory—Second Edition”, 1991, pp. vii-xii, 1-3, 16-17, 19, 157-161, 164-168, 273-279, 302-304.
Grant II Jerome
Oliff & Berridg,e PLC
Worku Negussie
Xerox Corporation
LandOfFree
Show-through compensation apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Show-through compensation apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Show-through compensation apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454526