Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1998-09-03
2001-06-26
Grant, II, Jerome (Department: 2624)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C382S299000, C382S295000
Reexamination Certificate
active
06252998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scanning module resolution adjustment method, and more particularly, to a resolution adjustment method for adjusting resolutions of a scanning module in two perpendicular directions.
2. Description of the Prior Art
Resolution of a scanning module is commonly adjusted by modifying the position of the lens in the scanning module. To find the correct position of the lens for generating an optimal resolution, image signals generated by scanning a calibration picture using the scanning module are used.
The resolution of a scanning module has a horizontal directional component and a vertical directional component. Optimal resolutions as well as the optimal positioning of the lens to obtain the best resolution in the two directions are different due to aberrations of the lens. Therefore, the lens has to be positioned at a position that allows both of the horizontal and vertical resolutions to approach the optimal state.
The calibration picture used to calibrate the scanning module comprises a group of parallel vertical lines or slanted lines. The vertical lines generate images used to adjust the vertical resolution but not the horizontal resolution. Therefore, the vertical lines are appropriate only for calibrating a lens with identical horizontal and vertical resolutions. Slanted lines, on the other hand, generate images comprising both the vertical and horizontal resolutions. However, if the slanted lines incline more horizontally than vertically, the horizontal component will predominate and use of the generated image alone cannot separately calibrate the vertical and horizontal resolutions. Therefore, it may be very difficult to find the ideal position of the lens. This in turn lowers the yield.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a resolution adjustment method for adjusting the resolutions of a scanning module both in the horizontal and vertical directions to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a resolution adjustment method for adjusting the resolution of a scanning module installed in a scanner for scanning a document, the scanning module comprising:
a case with a line-shaped opening on the top for receiving light from the document;
a sensor installed in the case having a plurality of linearly arranged sensing units for converting the light from the document through the line-shaped opening of the case into correspondent image signals;
a lens installed in the case for converging the light from the document onto the sensor; and
a mirror module installed in the case for passing the light from the document to the sensor; the resolution adjustment method comprising the following steps:
(1) providing a calibration picture to the scanning module to generate a calibration image which comprises two groups of parallel lines of two different directions for calibrating the resolutions of the sensor in the two different directions;
(2) measuring the magnitude of the image signals generated by the sensor in scanning the two groups of parallel lines and adjusting the scanning module until the magnitude of the image signals corresponding to the two groups of parallel lines are roughly equal.
It is an advantage of the present invention that the vertical and horizontal resolutions of the scanning module can be adjusted separately and easily by using the two groups of parallel lines so as to make the two resolutions almost equal while increasing the yield.
REFERENCES:
patent: 6044180 (2000-03-01), Brandestini et al.
Grant II Jerome
Hsu Winston
Mustek System Inc.
Worku Negussie
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