The invention relates to an active matrix of thin-film transistors or TFTs for an optical sensor, comprising a matrix of transistors formed on a substrate comprising a gate, a drain and a source, a set of rows and a set of columns that are connected to the gates and to an electrode of the transistor, respectively, pixel electrodes and, according to the invention, a set of capacitive electrodes lying at the same level as the electrodes of the transistors so as to form, with the pixel electrodes, storage capacitors.