Liquid crystal display device

A liquid crystal display device comprising an active matrix substrate on which a plurality of active elements are placed in a matrix, a counter substrate opposed to the active matrix substrate, and a liquid crystal layer interposed between the two substrates, and performing inversion driving in which a polarity of a voltage applied to the liquid crystal layer is inverted for each predetermined period, the liquid crystal display device comprising

• a photodetection part provided on the active matrix substrate for each or at least two of the active elements, and a drive part,
• wherein the photodetection part includes a photodiode that receives light incident through the counter substrate and the liquid crystal layer and outputs an electric signal in accordance with an amount of the received light, and a capacitance that stores charge in accordance with the electric signal, and outputs a photodetective signal whose level changes in accordance with the amount of the stored charge, and
• the drive part outputs, to each photodetection part, a reset signal that resets the charge stored in the capacitance and a reading signal that causes the photodetection part to output the photodetective signal so that, when the polarity is set to be a predetermined one, an output of the photodetective signal from the photodetection part is completed before the inversion of the polarity to the other one is started, and wherein the reset signal and reading signal are output by the drive part during a time period which is (i) after inversion of the polarity occurs, and (ii) prior so video data being output to a corresponding active element for display before another inversion.