Photodetection device and distance measurement system

A distance measurement system comprising:

• a lighting device that emits irradiation light;
• and
• a photodetection device that receives reflected light obtained when the irradiation light is reflected by a subject, wherein
• the photodetection device includes:
• a light reception unit that includes a pixel array unit including a plurality of light reception elements aligned in a matrix;
• a control signal generation unit that generates a control signal;
• a control unit that is electrically connected with the light reception unit via a control line and controls the light reception unit based on the control signal;
• a processing unit that is electrically connected with the light reception unit via a signal line and processes an output signal from the light reception unit;
• and
• a failure determination unit that detects a failure, and
• the failure determination unit detects a failure of the control line from the output signal from the light reception unit controlled based on a failure detection control signal having a predetermined pattern.