Carrier modulation ranging using SPAD

The invention relates to carrier modulation ranging using SPAD. An optical ranging system includes: a first phase-locked loop (PLL) configured to generate a first frequency signal and a second frequency signal; a second PLL configured to generate a third frequency signal based on a control signal, the control signal being formed using the first frequency signal; a light source coupled to the second PLL, in which an intensity of a light signal emitted by the light source is configured to be modulated according to a third frequency signal; a first single photon avalanche diode (SPAD) configured to receive the reflected optical signal; a time-to-digital converter (TDC) coupled to the first SPAD, where the TDC is configured to generate digital samples by sampling an output signal of the first SPAD under control of a second frequency signal; a reference signal generator configured to generate a reference signal; and a mixer configured to mix the reference signal and the digital samples from the TDC. 本公开涉及使用SPAD进行载