Method of and arrangement for determining the sharpness of originals for reproduction

US4649422A · kind A · utility

Assignee

• Agfa-Gevaert NV · BE

Inventors

• Wilfried Rauskolb · Munich, DE
• Helmut Treiber · Munich, DE
• Wilhelm Nitsch · Munich, DE

Key dates

• Filing date: Feb 28, 1985
• Grant date: Mar 10, 1987
• Expiry date: Feb 28, 2005

Classification

• Technology area (CPC G): Physics
• CPC primary: G03B27/80
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

An original to be reproduced is scanned line-by-line, and a scanning signal is generated for each linear, scanned region. The scanning signals represent the densities of the respective regions. A portion of each scanning signal is filtered to remove the higher frequencies. The filtered signal is differentiated to yield first density gradients, and the extreme positive and negative values of the first density gradients are determined for each region. Another portion of each scanning signal is differentiated without first removing the higher frequencies thereby yielding second density gradients. The extreme positive and negative values of the second density gradients are likewise determined for each region. A ratio of the extreme positive second density gradient to the extreme positive first density gradient is formed for each region, as is a ratio of the magnitude of the extreme negative second density gradient to the magnitude of the extreme negative first density gradient. A pair of sharpness values is then established for each region by subtracting 1 from the respective ratios. All of the sharpness values are now grouped according to the second density gradients or, alternatively…