Image analysis – Color image processing – Image segmentation using color
Reexamination Certificate
2000-06-06
2004-03-02
Patel, Jayanti K. (Department: 2625)
Image analysis
Color image processing
Image segmentation using color
C382S165000, C382S167000, C382S180000, C382S199000, C382S205000, C382S224000, C358S001900, C358S448000, C358S518000
Reexamination Certificate
active
06701009
ABSTRACT:
BACKGROUND
1. Field of the Disclosure
This disclosure relates to methods of image capture, more particularly for methods of accurately separating foreground pixels and background pixels from other pixels for color misregistration correction.
2. Background
Color image capture devices typically operate by capturing primary color component signals such as red, green and blue (RGB) from a set of charge coupled devices (CCDs). The CCDs are normally arranged in the sub-scan direction. The main scan direction, the direction in which the scanning bar moves, will be referred to as the X direction and the sub-scan direction, perpendicular to the main scan direction, will be referred to as Y.
These CCDs capture the image in one pass or in three passes, one for each primary color component. Regardless of the number of passes, however, there is typically some misalignment in the RGB signals. This misalignment between colors is referred to as color misregistration. It is caused by faulty superposition of the three colors. It normally manifests itself as color fringes on the edges of the objects that were scanned, text, graphics or drawings.
Color fringes normally appear as either cyan or magenta fringes on the edges of the scanned objects. Cyan fringes result from misregistration of the red signal, and magenta fringes result from misregistration of the green signal. The human eye does not normally detect misregistration of the blue signal, because of its low bandwidth and low contrast sensitivity.
Most often, color misregistration occurs in the Y direction. Vibration, scanning motion and the mechanical or optical design of the scanner can lead to faulty superposition of the three-color components. Several different approaches have been taken to solve this problem.
For example, some efforts have been directed at correcting the mechanical problems in the scanner by tracking registration marks. One example of these types of techniques is found in U.S. Pat. No. 5,737,003, issued on Apr. 7, 1998. In this patent, a laser scanner used to form latent images on the photoconductive belt is used to detect the position of the edge of the belt. The belt is then controlled to reduce the deviation of the belt from its path. It also includes a method for controlling the laser, and therefore the formation of the image, based upon the position of the belt.
Another of these mechanical registration techniques is found in U.S. Pat. No. 5,774,156, issued Jun. 30, 1998. The system uses several stations, one for each color of toner. The latent image formed by the individual scanners at the stations includes a registration area. The registration area is then aligned prior to the application of the toner. The registration area is then recharged to avoid having the registration marks attract any toner. This is repeated at each station to ensure proper positioning of the image before the latent image for the next color is formed.
U.S. Pat. No. 5,760,815, issued Jun. 2, 1998, shows another method. In this patent, a fiber optic detection means is used to detect registration signals produced by a retroreflector. The light from the retroreflector is analyzed and used to adjust the registration of the belt.
Other methods have focused on optical means to correct the misregistration. An example of these types of techniques can be found in U.S. Pat. No. 4,583,116, issued Apr. 15, 1986. In this patent, the color signals are manipulated to convert them into color separation signals for cyan, magenta, yellow and black. The edges of each of the colors is then detected and manipulated to switch lighter areas with darker areas, or vice versa, to avoid streaks and other imperfections.
In order to process the edges properly in these techniques, a determination must be made between pixels that belong in the foreground and those that belong in the background. Several techniques are used to detect color misregistration problems including foreground/background separation at the data level. Examples of these are found in U.S. Pat. Nos. 5,500,746 and 5,907,414. In U.S. Pat. No. 5,500,746, issued Mar. 19, 1996, the signals are manipulated to ensure that the dots formed are in line both in the X and Y directions for each color. The dots are resampled and repositioned as determined by line correction devices.
In U.S. Pat. No. 5,907,414, issued May 25, 1999, one of the more powerful prior art methods is shown. An image sensor used to scanning a manuscript generates signals and these signals are examined. If the examination of the signals determines that the pixel exists at an edge of a letter image, it is identified as such. These identified pixels are then adjusted in their brightness to ensure a smooth edge that was disrupted by vibration of the image sensor.
However, most of these techniques are too expensive or are too inaccurate to meet current expectations for quality. The digital color imaging market has become very competitive. Peripheral image capture and printing devices such as copiers, scanners, digital cameras, fax machines and printers continue to fall in price. Expectations of their quality continue to rise. Therefore, a method is needed that improves pixel separation into foreground and background at low cost but with high accuracy.
SUMMARY
One aspect of the invention is a method for separating foreground and background image pixels from other pixels. The method determines if a current pixel is an edge pixel, and then selects a window of pixels surrounding the current pixel if it is on an edge. This window is then analyzed to produce a classification of a gradient field within the window, and defines foreground and background image pixel values depending upon the classification. Once foreground and background pixel positions are defined, the process interpolates the value for the current pixel. The accurate designation of foreground and background pixels eliminates or mitigates any color misregistration error in the pixel value.
REFERENCES:
patent: 4583116 (1986-04-01), Hennig et al.
patent: 5500746 (1996-03-01), Aida
patent: 5583659 (1996-12-01), Lee et al.
patent: 5737003 (1998-04-01), Moe et al.
patent: 5760815 (1998-06-01), Genovese
patent: 5774156 (1998-06-01), Guerin
patent: 5825938 (1998-10-01), De Lange
patent: 5852673 (1998-12-01), Young
patent: 5907414 (1999-05-01), Hiratsuka
patent: 5986771 (1999-11-01), Henderson et al.
patent: 6128046 (2000-10-01), Totsuka et al.
patent: 6337925 (2002-01-01), Cohen et al.
patent: 6429875 (2002-08-01), Pettigrew et al.
patent: 6453069 (2002-09-01), Matsugu et al.
patent: 6556313 (2003-04-01), Chang et al.
patent: 6571012 (2003-05-01), Pettigrew
Machine Translation of JP 08191392 A, Jul. 23, 1996.
Chang William Ho
Makoto Otsu
Marger & Johnson & McCollom, P.C.
Patel Jayanti K.
Sharp Laboratories of America Inc.
Sukhaphadhana Christopher
LandOfFree
Method of separated color foreground and background pixel... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of separated color foreground and background pixel..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of separated color foreground and background pixel... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3259423