According to an aspect, a detection device includes: a substrate; a plurality of photodiodes arranged on the substrate; a light source configured to emit light to an object to be detected; a detection circuit configured to detect first detection signals based on reverse bias currents of the photodiodes when the light source is off, and to detect second detection signals based on the reverse bias currents of the photodiodes when the light source is on; and a memory configured to store first imaging data based on the first detection signals when the light source is off, second imaging data based on the second detection signals when the light source is on, and difference data between the first imaging data and the second imaging data.