Image sensor with electron multiplication and grouped readout of pixels

A matrix image sensor comprising at least two rows of pixels and comprising means for reading the pixels either individually or after the charges originating from a group of four adjacent pixels belonging to two adjacent rows and two adjacent columns have been grouped together, comprising, for the group of four pixels:

• for each pixel, a photodiode and a primary transfer gate allowing the charge generated by light in the photodiode to be transferred to the exterior of the photodiode;
• two electron multiplication gates, the first multiplication gate being adjacent to the transfer gates of the two pixels of a first column and the second gate being adjacent to the primary transfer gates of the two other pixels of the group, belonging to the second column, and means for applying to the two multiplication gates an alternation of potentials in phase opposition;
• first means for reading charge, comprising a first charge storage region and a first secondary transfer gate interposed between the first electron multiplication gate and the first charge storage region;
• second means for reading charge, comprising a second charge storage region and a second secondary transfer gate interposed between the second electron multiplication gate and the second charge storage region;
• and means for controlling the potentials applied to the transfer gates and to the multiplication gates, in order to execute a simple read mode and a grouped read mode, in which,
• in the simple read mode charges are transferred from the photodiodes of the two pixels of the first row to the first multiplication gate and to the second multiplication gate, respectively, then these charges are transferred from the multiplication gates to the first and second charge storage regions, respectively, and the charges present in these two regions are read by the first and second charge reading means, these operations then being repeated for the two pixels of the second row;
• and
• in the grouped read mode charges are transferred from the two pixels of the first column to the first multiplication gate and the charges of the two pixels of the second column are transferred to the second multiplication gate and, subsequently, the charges present under the multiplication gates are transferred to one of the storage regions, and the charge present in this region is read.