Patent ID: 7009648

Claim:
A method for operating a CMOS image sensor including a matrix of pixels arranged in a plurality of lines and columns, each of said pixels including a photosensor element accumulating charge carriers in proportion to the illumination thereof, at least a MOS transistor and storage means able to be coupled to said photosensor element by means of the MOS transistor at a determined instant in order to generate a sampled signal representative of said charge carriers accumulated by said photosensor, said storage means being intended to assure storage for the purpose of reading said sampled signal, wherein, said method includes: a first phase or initialisation phase, during which said photosensor element and said storage means are initialised at a determined initialisation voltage; a second phase or exposure phase during which said photosensor element is released from said initialisation voltage and generates charge carriers in proportion to its illumination, said photosensor element and said storage means being uncoupled from each other by means of the MOS transistor; a third phase or sampling phase during which said sampled signal which is generated and stored on said storage means by coupling said photosensor element to said storage means by means of the MOS transistor; and a fourth phase or reading phase, during which said sampled signal which is stored on said storage means is read, said photosensor element and said storage means being uncoupled from each other by means of the MOS transistor, and wherein during said fourth phase, said photosensor element is held at a voltage such that any charge carrier generated by said photosensor element is drained and thus does not disturb said sampled signal stored on said storage means, and wherein: during said first phase, said photosensor element and said storage means are uncoupled from each other by means of the MOS transistor; during said third phase said storage means, in a first stage, is released from said initialisation voltage, then, in a second stage, is briefly coupled to said photosensor element, thus allowing said sampled signal to be generated and stored in said storage means, and during said fourth phase said photosensor element, in a first stage, is again initialised at said determined initialisation voltage, then, in a second stage, said sampled signal which is stored on said storage means is read.