Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Reexamination Certificate
2001-01-22
2004-06-01
Coles, Edward (Department: 2622)
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
C358S488000, C358S449000, C382S169000, C382S274000
Reexamination Certificate
active
06744536
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to automatic background detection of a scanned document. More particularly, this invention relates to a system and method wherein edge detection parameters corresponding to the color of a backing ski are automatically selected when a backing ski having a first color is to be replaced with a ski of a different color.
In the reproduction of copies of an original document from video image data created, for example, by electronic input scanning from an original document, it is often desirable to provide functions dependent upon determining the exterior edges of the document. Such features include, for example, automatic magnification, automatic two-up copying, deletion of background image data which falls outside the detected exterior edges of the document to avoid storing a document requiring more space than necessary, automatic location of the document in a scanning system, electronic registration and deskewing of the electronic image, etc. In other words, to provide these features, the exterior edges of the document must somehow be detected by the scanning system.
In addition to the features identified above, the identification of the exterior edges of the document is necessary when scanning a document fed with a constant velocity transport (CVT) device, especially in a center-registered document feeding system. Typically, an edge detection operation is used to determine the arrival of individual input documents as well as to determine the side edges of the document fed into the CVT device so as to set the start/stop coordinates in the fast scan direction and thereby identify the image area for capture and processing. That is, the scanner uses the edge detection operation to determine the presence, exact location, and size of a document being imaged in a CVT device.
As should be appreciated, to provide an edge detection operation the exterior edges of the document must somehow be detected by the scanning system. Conventionally, to achieve the detection of the exterior edges of the original document, digital scanners use a backing (e.g., a platen cover or, in a CVT, a baffle or ski) that is readily distinguishable from the original document. That is, edge detection typically relies on the ability of the digital scanner and/or the image processing system to sense a difference, such as the difference in reflectance between the input document's background and the surrounding backing, e.g., the platen cover, backing plate, baffle, ski, etc. To enable such detection, the document is preferably passed between the scanner and a black (or other dark color) backing. However, backings with a yellow color, a whiter than white color, a backing which fluoresces, and various other alternatives have also been employed.
Although various alternatives have been utilized, it is most desirable to utilize a dark backing when scanning an original document so as to eliminate show through when scanning a double-sided or watermarked document (especially for thin or partially translucent originals). Utilizing a light absorbing backing (e.g., black or dark color) eliminates show through when scanning the document and enables the scanning system or other downstream image processing system to automatically locate the exterior edges of the original document.
However, an undesirable consequence of using a light absorbing backing is that any defect in the original document; such as holes, cuts, rips, dog-ears, etc. or other characteristic properties of the original; such as pre-punched holes, etc.; appear as dark objects (also referred to as a scanning artifact) when they are displayed electronically or rendered and printed on a recording medium, whether they are printed immediately, faxed or subsequently or remotely printed. In the following description, the defects in the original and the characteristic properties of the original will be generally referred to as defects and the corresponding areas in the output document will be referred to as artifacts. However, this notation does not imply that the physical properties of the original are actual defects, just properties that create artifacts in the scanning process which are undesirable.
Various solutions have been proposed to enable accurate edge detection while minimizing show through and removing the scanning artifacts corresponding to holes or similar defects in the scanned image. By having the backing area dark, any area (group of pixels) having a low reflectance value can be considered a potential backing area and thus subject to elimination from the rendered image. However, relying solely on the reflectance value when automatically electronically removing such areas of the scanned-in image is not acceptable since that could also remove actual image data, such as large block printed letter titles, bars, or graphics. Additionally, selectively manually electronically “painting” over such areas would be too time consuming in most cases, even if available. Given the likelihood of producing many false detections, is desirable to have a second criteria to measure in order to provide proper distinction between backing and the actual image on the document.
Various digital image processing systems for recognizing, and eliminating by image processing, artifacts corresponding to defects in the originals by identifying a finely patterned image on the backing surface have been proposed. Examples of such solutions can be found in U.S. Pat. No. 5,384,621 entitled “Document Detection Apparatus” and U.S. Pat. Nos. 5,959,290; 6,078,051 and 6,122,393 directed to an Image Input Device and Method for Providing Scanning Artifact Detection. Generally, these solutions detect the pattern of a backing by recognizing its electronic signature when it images through a hole in the document sheet and replacing the data with values corresponding to the document background on the assumption that actual text data would not have such a pattern. However, customers that do not normally ever image apertured original documents may not want such a feature implemented, and have no need to even risk any image loss.
Another solution to the above problem is described in U.S. Pat. No. 5,748,344 to Rees. Rees discloses the use of two sets of color sensitive sensors (photosites), each set being sensitive to a different color of light and a backing having a predetermined color. The predetermined color of the backing is selected such that it appears nearly black to one set of sensors and appears nearly white to a different set of sensors. For example, the system might include a backing that is a saturated yellow with a set of sensors that is sensitive to blue being used for edge detection and a set of sensors that is sensitive to green being used for image capture. Such a solution can be used with color scanners wherein a single channel (blue) is used for edge detection and registration with all three sensors (red, green, blue) being used for image capture.
The use of backing having a predetermined color provides an easy way to identify document edges and eliminate dark objects corresponding to document defects from the output document in a black and white scanner. However, this solution also has some disadvantages. For example, in many instances the background of the input document may not necessarily be white, such as when scanning a document printed on colored paper or capturing a pictorial or photographic image. In the case of a non-white document background, it becomes difficult to distinguish the document from the backing. Additionally, the use of a colored backing can adversely impact image quality.
Another proposed solution to reduce the reproduction of document defects as dark objects in the output is disclosed commonly assigned U.S. Pat. No. 6,166,394 entitled “Dual Background Document Scanner to Eliminate Hole Printouts” to Robert F. Rubscha. Disclosed therein is a dual mode imaging backing system that includes a substantially dark light absorbing backing surface area and a substantially light reflective backing surf
Baniak Jeffrey L.
Buchar Wayne A.
Harney William M.
Herloski Robert P.
Huedepohl Ralph H.
Coles Edward
Eipert William
Gibbs Heather D
Xerox Corporation
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