Photodetection device, semiconductor photodetection element, and method for driving semiconductor photodetection element

A photodetection device comprising:

• a light projecting unit that is arranged to project light toward a detection target region, the light having a cross-sectional shape whose longitudinal direction corresponds to a first direction;
• a light receiving unit that includes a semiconductor substrate including a plurality of cells arrayed two-dimensionally in M rows and N columns (M and N are integers equal to or greater than 2) and that is arranged to receive reflected light of the light projected by the light projecting unit;
• and
• a controller that is connected to the light receiving unit,
• wherein each of the plurality of cells includes at least one avalanche photodiode arranged to operate in a Geiger mode,
• the plurality of cells includes N first cell groups each of which includes M cells aligned in a column direction,
• the light projecting unit is arranged to scan the light along a second direction intersecting the first direction such that the reflected light is incident on each first cell group or each plurality of first cell groups,
• the controller is arranged to apply one of a first voltage and a second voltage to each first cell group or each plurality of first cell groups, the first voltage being greater than a breakdown voltage of the avalanche photodiode, the second voltage being less than the breakdown voltage, and
• the controller is also arranged to:
• start the application of the first voltage before a starting time at which the projection of the light toward a corresponding light projection position when applying the first voltage to each first cell group or each plurality of first cell groups in accordance with the incidence of the reflected light, and
• read signals from cells included in the first cell group or the plurality of first cell groups to which the first voltage has been applied.