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Proceedings Paper

Measuring the line spacing and density of high-resolution images from capstan and drum output scanners
Author(s): Robert E. MacDonald
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Paper Abstract

Minor defects in line spacing and/or density variations can cause visual artifacts in images generated by output scanners. This paper presents a method to quantify such errors using a measurement station that characterizes both the line spacing and the relative density of lines printed at 1200 to 2400 lines/inch. While other measurement methods exist (e.g., grabbing single frames of data from a micro-densitometer), possibly most restricting is the limited number of lines that can be measured due to the trade-off between field of view and resolution. Moire effects may also be utilized for spacing checks, but the results are not sufficiently quantized. The method being presented does not limit the number of lines that can be measured at one time, therefore large regions can be used to perform spatial frequency analysis. In 1- on/1-off line patterns, variations of only 2-3% in line spacing (approximately equals 40 microinches in 1200 LPI) are perceptible. Very minor variations in density can also cause visual artifacts. Distinguishing between a spacing error and a density error is critical to the troubleshooting process. This measurement system was designed to have a theoretical positional resolution of 0.417 microinches. Repeatability of line space measurements for this type of pattern is typically better than 10 microinches.

Paper Details

Date Published: 27 April 1995
PDF: 9 pages
Proc. SPIE 2413, Color Hard Copy and Graphic Arts IV, (27 April 1995); doi: 10.1117/12.207585
Show Author Affiliations
Robert E. MacDonald, Miles Inc., AGFA Division (United States)

Published in SPIE Proceedings Vol. 2413:
Color Hard Copy and Graphic Arts IV
Jan Bares, Editor(s)

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