Patent ID: 6999018
Filing Date: 2006-02-14
Classification: H03M,H04N

Abstract:
1. An analog-digital conversion device in particular for an image sensor that comprises a pixel matrix photosensitive cell, having a plurality of pixels, to pick up at least one image to be digitised, the device comprising at least one N-bit first converter and at least one M-bit second converter connected to the first converter, the first and second converters being used to convert a voltage or current level of a voltage or current pixel signal to N+M bits, the voltage or current level to be converted depending on a level of light captured by each pixel in a particular voltage or current dynamic range of the sensor, the first converter comprising comparison means for comparing the voltage or current level of the pixel with one or more voltage or current thresholds delimiting successive voltage or current ranges within the dynamic range in order to supply an N-bit binary word whose value relates to a voltage or current range in which the voltage or current level of the pixel is situated, the successive voltage or current ranges within the dynamic range being used to define an illumination of a pixel, ranging from a weakly illuminated pixel to a strongly illuminated pixel, wherein the second converter comprises conversion adaptation means that are configured for the voltage or current range that has been determined between a minimum voltage or current and a maximum voltage or current of said voltage or current range as a function of the value of the N-bit binary word supplied by the first converter, the conversion adaptation means being configured to convert the voltage or current pixel signal to a number of bits less than M for a voltage or current range that has been determined corresponding to a strongly-illuminated pixel or equal to M for a voltage or current range that has been determined corresponding to a pixel that is weakly illuminated.