Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-05-27
2001-03-06
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C399S380000, C250S227110
Reexamination Certificate
active
06198088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to methods and apparatus for detecting size, location and/or orientation of a document on a platen of a copier or a scanner. More particularly, this invention relates to methods and apparatus for detecting size, location, shape and/or orientation of a document using a two-dimensional array of light sources provided on a platen cover assembly.
2. Description of Related Art
In a digital copier or a document scanner, it is desirable to accurately locate the edges of a document that has been placed on the platen of the copier or scanner. Using the detected edge information, image processing is performed to automatically deskew a copy of the document, properly register the copy on the copy paper, resize the copy to fit the selected paper size, and/or the like. One technique for locating the document edges is to use either a black or a specularly reflective platen cover. A prescan is performed with the copier's or scanner's existing document illuminator and sensor. During this prescan, the area surrounding the document appears darker than the body of the document, thereby permitting identification of the document's edges.
SUMMARY OF THE INVENTION
However, the black cover reduces the overall contrast of the image formed from the document reflection, and also causes features such as punched holes in the document to be copied as black features. The specularly reflective cover produces less contrast reduction, but still causes document holes to be reproduced as black images.
This invention provides methods and apparatus for detecting a document on a platen using a platen cover assembly with a two-dimensional array of light sources. The two-dimensional array of light sources may extend over the full area of a platen cover assembly or just a portion of this assembly. Furthermore, the two-dimensional array of light sources may be aperiodic or include multiple smaller two-dimensional arrays.
In one aspect, the methods and apparatus of this invention provide a platen cover assembly that includes a light source array having a plurality of light sources arranged in a two-dimensional array, and a translucent white material covering at least a side of the light source array that faces a platen.
The light source array preferably includes a fiber optic mat that has at least one optical fiber arranged to form a plurality of optical fiber bends, each of the plurality of light sources corresponding to a respective one of the optical fiber bends. At least one light source introduces light into the at least one optical fiber.
In another aspect, the methods and apparatus of this invention provide a digital image processor that includes a platen, a platen cover assembly with a two-dimensional light source array, a document illuminator, a sensor, and a controller. The controller causes the sensor to sense light from exposed light sources of the light source array during an off state of the document illuminator, and causes the sensor to pick up an image of a document placed on the platen during an on state of the document illuminator.
In yet another aspect, the methods and apparatus of this invention provide a method for detecting a document on a platen of a digital image processor that includes a platen cover with a two-dimensional light source array and a document illuminator. The method includes placing a document on the platen, with the platen cover covering the document and the platen, performing a prescan of the platen to sense light from exposed light sources of the light source array during an off state of the document illuminator, and generating a document map based upon the light sensed during the prescan.
Since the edges of the document may be located using the thus-generated document map, scanning of the document may be performed using a platen cover assembly that reflects white light. Therefore, document features such as punched holes are not reproduced as black features.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of various exemplary embodiments.
REFERENCES:
patent: 4557581 (1985-12-01), Woolley et al.
patent: 4630127 (1986-12-01), Fuwa
patent: 5119212 (1992-06-01), Mori et al.
patent: 5790211 (1998-08-01), Seachman et al.
Allen Stephone B.
Oliff & Berridg,e PLC
Xerox Corporation
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