Methods and apparatus for discriminating between the front and back surfaces of films
US4645351A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 23, 1984 |
| Grant date | Feb 24, 1987 |
| Priority date | — |
| Expiry date | May 23, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03D15/00
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method and apparatus for discriminating a surface of a developed film focuses a picture pattern on a film disposed at a reference position. One or two sensors are then located at focused positions of the picture pattern of the film when the front surface of the film is at the reference position and when the back surface of the film is at the reference position, respectively. The two resultant sensor outputs are then band-pass filtered to extract the portions of the outputs within a predetermined frequency range. The resultant outputs are then rectified and integrated and then compared by a comparator whose outputs is a first value when the front surface of the film is at the reference position and is a second different value when the back surface of the film is at a reference position.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.