System, circuit and method providing a dynamic range pixel cell with blooming protection

This invention relates generally to photo-sensitive circuits, and more particularly to photo sensitive circuits used in pixel cells. An extended dynamic range pixel cell providing blooming protection is disclosed herein. By applying a timed varying signal to a shunt transistor in order to shunt exce...

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Bibliographische Detailangaben
Hauptverfasser: Drowley, Clifford I, Ramaswami, Shrinath
Format: Patent
Sprache:eng
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Beschreibung
Zusammenfassung:This invention relates generally to photo-sensitive circuits, and more particularly to photo sensitive circuits used in pixel cells. An extended dynamic range pixel cell providing blooming protection is disclosed herein. By applying a timed varying signal to a shunt transistor in order to shunt excess charge generated by a photosensor in response to high intensity illumination, blooming protection can be provided. In particular configurations, blooming protection is provided not only during an integration period but also during a readout period when the pixel cell is generally most susceptible to blooming problems. The time varying voltage is also used to extend the dynamic range of the pixel cell thereby increasing the pixel cells usefulness in high contrast conditions, such as bright sunlight casting deep shadows, nighttime automotive applications, and the like.