Display device

A display device comprising an optical sensor on an active matrix substrate, wherein the optical sensor includes:

• a photodetecting element for receiving incident light;
• a reset signal line for supplying a reset signal to the optical sensor;
• a readout signal line for supplying a readout signal to the optical sensor;
• and
• a sensor switching element for reading out a photoelectric current output from the photo detecting element, according to the readout signal, during a period from the supply of the reset signal to the supply of the readout signal, wherein
• the display device further comprises:
• a light shielding film provided on a back side of the photo detecting element;
• and
• a driving circuit for switching a potential of the light shielding film between a high level potential and a low level potential;
• the driving circuit causes the light shielding film to have the high level potential during a period that at least partially overlaps a period while the reset signal is supplied to the reset signal line;
• the photodetecting element is a diode having a PIN structure;
• and
• the following is satisfied:
• VRST—L+Vth—p≦VLS—L≦VC+Vth—n
• where VLS—L represents the low level potential of the light shielding film, VRST—L represents a low level potential of the reset signal, VC represents a potential in an n-layer of the photodiode, Vth—p represents a threshold voltage of an assumed p-channel MOS transistor where a p-layer of the photodiode is a source-drain region and the light shielding film is a gate electrode, and Vth—n represents a threshold value of an assumed n-channel MOS transistor where the n-layer of the photo diode is a source-drain region and the light shielding film is a gate electrode.