Analog-to-digital conversion in image sensors using a differential comparison
US8134623B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 11, 2009 |
| Grant date | Mar 13, 2012 |
| Priority date | — |
| Expiry date | Dec 19, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N25/78
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An image sensor has a per-column ADC arrangement including first and second capacitors for correlated double sampling, and a comparator circuit. The capacitors are continuously connected to, respectively, the analog pixel signal and a ramp signal without use of a hold operation. The comparator circuit comprises a differential amplifier having one input connected to the junction of the two capacitors and another input connected to a reference signal. The reference signal is preferably sampled and held from a reference voltage. The use of a differential amplifier as first stage of the comparator addresses problems arising from ground voltage bounce when a large pixel array images a scene with low contrast.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.