Copperplate printing detection method and device therefor
US4594514A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 31, 1983 |
| Grant date | Jun 10, 1986 |
| Priority date | — |
| Expiry date | Jan 31, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG07D7/12
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A method is provided for observing, preferably through the medium of an optoelectronic pick-up, the carrier to be checked which is illuminated by a light beam having an angle of incidence of at least 45.degree. through a rotary disc comprising alternately transparent and opaque sectors spaced from one another by a distance at least substantially equal to the distance measured between the lines of the copperplated printing formed on the carrier. The carrier image is formed in the plane of a detector by means of an optical system. If the carrier has a copperplate printing formed thereon, a moire effect is observed. If the pick-up extends over several transparent sectors of the disc this moire effect is converted electrically into a very pronounced periodic variation of the current delivered by the pick-up, at the sector passage frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.