Column readout multiplexer for CMOS image sensors with multiple readout and fixed pattern noise cancellation
US5965871A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 5, 1997 |
| Grant date | Oct 12, 1999 |
| Priority date | — |
| Expiry date | Nov 5, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N25/78
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An active pixel sensing structure includes an array of pixel unit cells each of which an adapted to alternate between a light sensing mode wherein the cell outputs an image signal and a reset mode wherein the cell outputs a reset signal. The image signal is proportional to light incident on the cell, and the reset signal is proportional to a predefined reference potential. An improved readout circuit according to the present invention includes a first sample and hold component for receiving and storing the image signal, and second sample and hold component for receiving and storing the reset signal. A signal amplifier is provided for each sample and hold component. A switching circuit is operable between a first mode and a second mode. In the second mode, the first and second sample and hold components are operatively decoupled from the corresponding signal amplifiers while input terminals of the signal amplifiers are connected to a source of predetermined reference potential. With the switching circuit in the second mode, fixed pattern noise (FPN) attributable to the amplifiers is determined. With the switching means in the first mode, a voltage, D2, is determined across outputs o…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.