Photosensor and ambient light sensor with constant bias voltage
US8138463B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 4, 2007 |
| Grant date | Mar 20, 2012 |
| Priority date | — |
| Expiry date | Jan 14, 2029 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G2360/144
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method of operating a photosensor comprising: applying a bias voltage to a photosensor (12) comprising n (n>1) photo-sensitive elements (8) connected in series, and determining the photocurrent in the photosensor (12) at a time when the applied bias voltage across the photosensor maintains the photosensor at or close to the point at which it has the greatest signal-to-noise ratio. This may conveniently be done by determining the current in the photosensor at a time when the applied bias voltage across the photosensor is equal or approximately equal to n×Vbi, where Vbi is the bias voltage about which the current in a single one of the photo-sensitive elements (8), in the dark, changes sign. In an embodiment in which the photo-sensitive elements (8) are photodiodes, the bias voltage Vbi is the “built-in” voltage of the photodiodes. The photocurrent generated when n series-connected photodiodes are illuminated is approximately equal to the photocurrent generated when one photodiode is illuminated. However, the leakage current (i.e., the dark current) for the n series-connected photodiodes is significantly lower than the leakage current for one photodiode. The signal-to-noise-ratio i…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.