To form an optical sensor capable of outputting with a binary value on a substrate such as a display panel.
This optical sensor has a photodiode 112 reversely biased so that a current corresponding to a light receiving quantity flows, and an inverter circuit 114 for logically inverting a voltage level of an anode of the photodiode 112. Before detection of the light receiving quantity, the anode of the photodiode 112 and a node P which is an input terminal of the inverter circuit 114 are initialized to a threshold voltage Vth of the inverter circuit 114, and after completion of initialization, the node P is lowered as much as a prescribed voltage, and after lowering, a period until a logic signal by the inverter circuit 114(116) is logically inverted is outputted as a value corresponding to the light receiving quantity.
Fujitsuna Hideyoshi
Osamu Suzawa