Detection device

A detection device comprising:

• a base member having a first principal surface;
• a detection area provided to the first principal surface;
• a sensor including a plurality of photodiodes that are arranged in the detection area and arranged in a first direction parallel to the first principal surface and a second direction parallel to the first principal surface and intersecting the first direction;
• a plurality of gate lines that extend in the first direction and are coupled to the photodiodes;
• a plurality of signal lines that extend in the second direction and are coupled to the photodiodes;
• and
• a light emission device configured to emit light through gaps between the photodiodes in a direction in which the first principal surface faces, wherein
• the light emission device includes a plurality of light sources,
• a lit area in which the light emission device is lit up is a portion of the detection area overlapping the light sources when viewed in a third direction intersecting the first direction and the second direction,
• a portion of the detection area not overlapping the lit area is an unlit area in which the light emission device is not lit up, and
• photodiodes that overlap the unlit area when viewed in the third direction are selected from among the photodiodes, and amounts of light received by the selected photodiodes are read.