Photodetector and portable electronic equipment

A photodetector, comprising:

• a light-emitting element;
• a first light-receiving unit that has a plurality of avalanche photodiodes as a first light-receiving element that detects, in Geiger mode, photons of pulse light emitted by the light-emitting element;
• a second light-receiving unit that has a plurality of avalanche photodiodes as a second light-receiving element that detects, in Geiger mode, photons of reflected light where the pulse light has been reflected by a detection object;
• a time difference measuring unit that measures a time difference between a puke signal output from the first light-receiving element of the first light-receiving unit and a pulse signal output from the second light-receiving element of the second light-receiving unit;
• an ambient-light-incident light-receiving-element determining unit that determines the second light-receiving element on which ambient light is incident, based on pulse signals output from second light-receiving elements of the second light-receiving unit when the light-emitting element is not emitting light;
• and
• an operation stopping unit that stops operation of the second light-receiving elements for which determination is made that ambient light is incident.