Illumination and light gate utilization methods and apparatus
US4420772A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 20, 1981 |
| Grant date | Dec 13, 1983 |
| Priority date | — |
| Expiry date | Jul 20, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02F1/0555
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Methods and apparatus for reading information from a record with the aid of a plurality of electrically controlled light gates illuminate the light gates with light of a first intensity above zero light intensity and precondition the light gates to subsequent opening in response to electric control signals by electrically biasing the light gates to an initially open condition wherein the gates pass light from the illumination at an intensity above zero light intensity and below a second intensity lower than the first intensity. These methods and apparatus also subject the record to a first illumination by said light of an intensity above zero light intensity and below the second intensity as passed by the preconditioned gates in the initially open condition, subject the record to a second illumination by further opening the preconditioned light gates in response to electric control signals to pass light at at least the second light intensity and scan the record with the passed light at at least the second intensity, and read information from the record only in response to the second illumination as among the first and second illuminations.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.