Light detector and range finder

A range finder comprising:

• a light-emitting element configured to emit pulsed light to a detection target at predetermined time intervals;
• a light detector configured to receive reflected light that is the pulsed light emitted from the light-emitting element, and that is reflected on the detection target;
• and
• a distance operation circuit configured to perform an operation of a distance to the detection target in accordance with a timing at which the pulsed light is emitted by the light-emitting element, and a timing at which the reflected light is received by the light detector,
• wherein the light detector includes
• a single-photon avalanche diode (SPAD) having one end connected to a first node, and configured to receive the reflected light,
• a resistor component having one end connected to the first node,
• a switch element having one end connected to the first node, and
• a control circuit configured to control the switch element to discharge or charge the first node, and
• wherein in response to a change in a potential of the first node from a first potential to a second potential,
• the control circuit turns on the switch element until a second period elapses after a lapse of a first period measured from the change to the second potential, or until the potential of the first node changes back to the first potential during the second period, and
• the control circuit turns off the switch element upon a lapse of the second period without the potential of the first node changing back to the first potential, and the control circuit turns on the switch element again after a lapse of a third period measured from the turning off of the switch element.