Optical proximity sensor and corresponding method of operation

A method of operating an optical proximity sensor, the method comprising:

• applying, to a solid-state photo-electric converter of the optical proximity sensor, a bias signal modulated between a first value and a second value, the second value different from the first value, both the first value and the second value being higher than a breakdown voltage of the solid-state photo-electric converter, wherein a modulated optical signal is emitted by the solid-state photo-electric converter towards a target object in response to the bias signal being applied to the solid-state photo-electric converter;
• receiving an electrical output signal from the solid-state photo-electric converter, the electrical output signal being a function of a received modulated optical signal that is received at the solid-state photo-electric converter as a result of reflection of the modulated optical signal emitted towards the target object;
• performing a phase comparison of the modulated bias signal applied to the solid-state photo-electric converter against the electrical output signal received from the solid-state photo-electric converter;
• producing a phase shift signal based on the phase comparison, the phase shift signal being a function of a phase shift between the modulated optical signal emitted towards the target object and the received modulated optical signal that is received at the solid-state photo-electric converter;
• and
• computing a distance between the optical proximity sensor and the target object as a function of the phase shift signal.

A proximity sensor, comprising:

• a substrate;
• an optical sensor on the substrate, the optical sensor configured to emit a modulated optical signal towards a target object in response to a bias signal being applied to the optical sensor, and detect a reflected modulated optical signal that is received by the optical sensor as a result of the modulated optical signal being reflected off of the target object;
• a driver circuit on the substrate, the driver circuit configured to apply the bias signal to the optical sensor, the bias signal alternating between a first value and a second value different from the first value, both the first value and the second value being higher than a breakdown voltage of the optical sensor;
• and
• a control circuit configured to calculate a phase shift between the modulated optical signal and the reflected modulated optical signal, and determine a distance between the proximity sensor and the target object based on the phase shift.