Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1998-08-31
2001-02-13
Mehta, Bhavesh (Department: 2721)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C382S293000, C382S305000, C382S289000
Reexamination Certificate
active
06188801
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to a method and apparatus for image calibration for an optical scanner, and especially to a method and apparatus which can automatically calibrate a skew image caused by the oblique displacement of the image sensor in an optical scanner.
B. Description of the Prior Art
The optical mechanism for a scanner uses an adjustment jig to tune the horizontal level, right and left positions, and focus for an image. The optical mechanism also includes a calibration paper for a charged couple device to read, thereby to calibrate scanned images. However, the optical mechanism is subjected to damages caused by improper use or handling in shipment. Consequently, the optical mechanism will shift and generate skew images as shown in FIG.
1
. Refer to
FIG. 1
, the skew image indicated by coordinates of As(i,j) is in contrast to a normal coordinates indicated by coordinates of A(i,j). The front edge of the skew image can be detected by gray levels. For instance, in
FIG. 1
, the skew black line indicates the front edge of the skew image.
When the optical mechanism of a scanner is damaged, the image quality cannot be improved simply by fine-tuning. Moreover, there are various possible reasons for scanner to generate skew images. It would be very difficult to find a universal method for solving the occurrence of skew images for every scanner. Even if the scanner is sent back to customer service for repair, there is no guarantee that the occurrence of skew images will never happen again.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an intelligent optical scanner incorporated with an automatic calibration apparatus, which can automatically calibrate a skew image while being read into the image sensor, thereby to efficiently eliminate the occurrence of skew images.
It is another object of the present invention to provide a method and apparatus that can automatically calibrate a skew image caused by the oblique displacement of the optical mechanism, thereby to improve the image quality of a scanner and save the cost and efforts on maintenance.
These and other objects of the invention, which will become more apparent as the invention is described more fully below, are obtained by providing a method and apparatus for automatic image calibration. A memory is divided into several blocks in advance for storing calibrated pixels in sequence. Then, each pixel is checked row by row. The obliquity ratio of each pixel will be computed based on two referential blocks on the two sides of the calibration paper. The obliquity ratio will then divided by the length of a pixel. If the residue of the division is larger than half the length of the pixel, it indicates that that pixel is the beginning of next block. Following this rule, we can divide each row into several blocks. The skew pixels will be calibrated according to a first calibration procedure and a second calibration procedure. The calibrated pixels will be stored in the memory blocks in sequence according to their block numbers. After all the pixels of the same row have been calibrated, the calibrated pixels will be read from the memory blocks in sequence. The calibrated procedure repeats until each row of the image has been calibrated.
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Chen Bill
Tsai Jenn-Tsair
Lowe Hauptman & Gilman & Berner LLP
Mehta Bhavesh
Patel Kanji
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