Film positioning system using dual perforation sensors
US5565912A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 16, 1994 |
| Grant date | Oct 15, 1996 |
| Priority date | — |
| Expiry date | Feb 16, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B27/6285
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method and apparatus for controlling the positioning of a filmstrip in a film scanning gate using signal states derived from a pair of spaced film sprocket holes or perforation ("perf") sensors on either side of the film scanning gate in conjunction with line scan counts and filmstrip drive, stepper motor half-step counts. The filmstrip is advanced by the stepper motor in a pre-scan operation through the film scanning gate for line scanning the image frames at a low resolution and advanced in the reverse direction back into the film scanning gate for high resolution scanning in a main-scan operation. A line scan array of line scan counts and half-step counts as well as first and second perf arrays of half-step counts and perf sensor states are generated in the pre-scan operation. Image frame borders are located in the pre-scan operation as border line scan counts and correlated in the line scan array to the half step counts to go to in the main-scan. During main-scan, the filmstrip image frames are positioned in the scanning gate by reverse drive of the stepper motor in a coarse and fine alignment process employing the half step counts to go to and the state transitions in the fi…
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