Image analysis – Applications – Document or print quality inspection
Reexamination Certificate
1998-07-17
2001-04-24
Grant, II, Jerome (Department: 2624)
Image analysis
Applications
Document or print quality inspection
C358S504000
Reexamination Certificate
active
06222934
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The invention relates to a test chart, especially to a test chart printed on a calibration paper readable by an optical scanner for image quality test.
B. Description of the Prior Art
It is known that an optical scanner has to pass strict image quality tests before it can be sold on the market. The tests include horizontal and vertical scaling-up, skew, color consistency, color balance, shading, step transition, peripheral, resolution, and missing line and so on. These tests are usually done by examining an image of a test chart scanned by the optical scanner under quality testing. Since the test chart contains specially designed patterns for testing various features of an optical scanner, so from the images of the test chart, the image quality of the optical scanner can be shown easily.
Conventional test charts are usually not well organized. The data size of the test patterns is usually so large that each pattern on the test chart has to be scanned separately. And each testing is also processed separately. Consequently, the image quality test of an optical scanner consumes lots of testing time and efforts. Moreover, some test charts do not have a few important test items, such as step transition test, image skew test, and center resolution test. Besides, the patterns for identifying peripherals are usually too small to be detected.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a test chart which contains patterns sufficient enough for doing all test items and which is so compact that one pass of scanning is enough to perform all test items, thereby to speed up the testing procedure and save time and efforts.
It is another object of the invention to provide a test chart which can generate an image of small data size to be easily processed by a computer program to determine the image quality of an optical scanner.
Accordingly, the inventive test chart is printed on the front end of a calibration paper which is about A4 size. The test chart is only about the size of 20×5 cm. The test chart includes patterns for testing missing lines, gray levels, resolution, horizontal and vertical scaling up, recognition capability, skew and peripheral. The pattern for testing missing lines is a pattern of slanting line segment having inclination of 45 degrees. The patterns for testing gray levels are blocks of different gray levels grouped at the left side, the right side and at the center of the test chart and arranged in the same order. The patterns for testing resolution are line arts of different resolutions grouped at the left side, the right side and at the center of said test chart and arranged in the same order. The patterns for testing scaling-up are a pair of black blocks symmetrically located at the front end of the two sides of the test chart and a black bar line located at the bottom of the test chart.
REFERENCES:
patent: D. 363031 (1995-10-01), Bruegmann et al.
patent: 4020281 (1977-04-01), Davis
patent: 4575124 (1986-03-01), Morrison
patent: 5953990 (1999-09-01), Chalmers
Grant II Jerome
Mustek Systems Inc.
Pillsbury & Winthrop LLP
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