Image sensor with double charge transfer for large dynamic range and method of reading

A method for reading charges deriving from pixels of an image capture matrix, in which the pixels of one and the same row are addressed simultaneously for each to establish, on a respective column conductor linked to a read circuit, a potential representing the charges generated by the lighting of this pixel, and in which a pixel comprises at least one photodiode, a charge storage node, and a row selection transistor for linking the storage node to the column conductor or isolating it from this conductor, the integration of charges in the photodiode and the reading of the charges being done according to the following sequence of operations:

• integration of charges in the photodiode during a first integration period,
• first transfer of the thus integrated charges from the photodiode to the storage node at the end of the first integration period,
• integration of charges in the photodiode during a second integration period different from the first,
• establishment of a connection between the storage node and the column conductor,
• first sampling, in a capacitor of the read circuit, of a first potential present at this moment on the column conductor and resulting from the first charge transfer,
• second charge transfer from the photodiode into the storage node, and, subsequently, an analog-digital conversion of the sampled potential in the capacitor,
• wherein a second conditional sampling is performed, in the same capacitor, of a second potential level present on the column conductor and resulting from the second charge transfer, an actuation of the second sampling being conditioned by the level of the first or the second potential present on the column conductor, an information on the actuation of the second sampling being transmitted to determine a multiplying factor to be applied to the result of the analog-digital conversion.