Process for recording semihalftone images

US4876611A · kind A · utility

Assignee

• E.I. DU PONT DE NEMOURS AND COMPANY · US

Inventors

• Gerhard Fischer · Offenbach, DE
• Helmut Quabeck · Babenhausen, DE

Key dates

• Filing date: Sep 21, 1987
• Grant date: Oct 24, 1989
• Expiry date: Sep 21, 2007

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04N1/4051
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

A process involving scanning an original linewise and determining the tonal value of each scan dot. Multiple scan dots are collected into a scan field. The average tonal value of each scan field is determined by averaging the tonal values of the scan dots of that scan field. The original is reproduced on a recording medium by individual recording dots that can take the tone value "print" or "no-print". Several recording dots correspond to a scan field of the original. The tone value of the scan field can be reproduced almost exactly on the average by printing a specific number of recording dots. The distribution of recording dots to be printed for a scan field is determined by subdivision of the scan field into the smallest subfields. In this process, the scan field is subdivided in at least one subdividing step into these smallest subfields, the average tonal value of each resulting subfield being determined so that the number of recording dots to be printed in all subfields of a scan field correspond to the average tonal value of the scan field.