28 January 2008 Characterization of mottle and low-frequency print defects
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In this paper, we propose new techniques for detecting and quantifying print defects. In our previous work, we introduced a scanner-based print quality system to characterize directional print defects, such as banding, jitter, and streaking. We extend our previous print quality work two ways. First, we introduce techniques for detecting 2-D isotropic, mottled print defects such as grain and mottle. Wavelet pre-filtering is used to limit the defect's size or frequency range. Then we analyze the L* variation in the wavelet-processed images. The methods used to quantify grain and mottle are similar to ISO/IEC 13660 techniques. The second part of this paper provides techniques for detecting and quantifying low frequency directional defects, which we call left-to-right and top-to-bottom L* variation. Since these defects extend less than two cycles across the page, and probably less than a complete cycle, we fit a 4th-degree polynomial to the defect profile. To measure the strength of the defect, we use variational analysis of the fitted polynomial. Experimental results on 10 printers and 100 print samples showed an average correlation for isotropic defects of 0.85 between the proposed measures and experts' visual evaluation, and 0.97 for low frequency defects.
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Ahmed H. Eid, Brian E. Cooper, and Edward E. Rippetoe "Characterization of mottle and low-frequency print defects", Proc. SPIE 6808, Image Quality and System Performance V, 680809 (28 January 2008); doi: 10.1117/12.766785; https://doi.org/10.1117/12.766785

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