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Proceedings Paper

Analytical model of skew effect in digital press characterization
Author(s): Mu Qiao; Jan P. Allebach
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Paper Abstract

In this paper we propose an analytical model of the skew effect in digital press characterization. Digital press characterization gives critical information based on which one can predict how a certain layout, images, and text will be rendered by the press on a particular substrate. Modulation Transfer Function (MTF) analysis characterizes the digital press of interest using MTF test patches designed with different spatial frequencies, tone levels, angles, and colors. These patches are printed and then scanned. However, at high spatial frequencies, a small mis-registration in the scanned image can produce large distortion. Skew is a common image misregistration introduced in image analysis processes due to the imperfect alignment between the scan target media and the scanning device. The conventional method of de-skewing by rotating the scanned image is not desirable because of the large amount of data in high resolution scans. We present a strategy for rejecting skewed images based on the skew angle and the error tolerance so that they can be rescanned and also a simple procedure to correct the skew effect based on our analytical model. With our scheme, special marks are designed and printed along with the MTF test target page to aid the calculation of the skew angle. A threshold for the acceptable maximum skew angle is calculated using the properties of the MTF test target page pattern and the error tolerance. An image with skew angle larger than the threshold will be rejected. A look-up table can be generated to compensate for the skew effect on the MTF measurement.

Paper Details

Date Published: 17 February 2006
PDF: 8 pages
Proc. SPIE 6076, Digital Publishing, 60760D (17 February 2006); doi: 10.1117/12.660252
Show Author Affiliations
Mu Qiao, Purdue Univ. (United States)
Jan P. Allebach, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 6076:
Digital Publishing
Jan P. Allebach; Hui Chao, Editor(s)

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