Automatic gain control for photosensing devices
US4097731A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 2, 1977 |
| Grant date | Jun 27, 1978 |
| Priority date | — |
| Expiry date | Jun 2, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K2207/1018
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A beam-of-light (BOL) sensor having means for regulating the intensity of the sensor light source to compensate for extraneous factors in the operating environment, e.g. dust accumulation, that may affect consistent sensor operation. The BOL sensor includes a photosensor whose output signal is compared against a reference signal to determine if the light source intensity is of the proper level. The comparison signal is transformed into a digital pulse that adjusts the stored count of a counter upward or downward in accordance with the comparison of the photosensor signal and reference signal. The adjusted count is converted to analog form and fed back to drive the light source. A trailing edge detector enables the counter to count up or down when an object is in the sensing station defined by the light source and photosensor. A hole filter is provided to filter out small, spurious apertures in a sensed object that would otherwise yield a double detection signal and cause an improper adjustment of the stored count.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.