Abstract: An optical sensing device includes an optical transmitter, coupled to transmit outgoing modulated radiation from a coherent radiation source at a predefined wavelength toward a target. A splitter splits off a fraction of the outgoing modulated radiation. An optical element is disposed in a path of the outgoing modulated radiation following the splitter. A mixer mixes the fraction of the outgoing modulated radiation with incoming radiation, including the modulated radiation that has been reflected from the target via the optical element. An optical delay line conveys the fraction of the outgoing modulated radiation from the splitter to the mixer over a first optical length that is within one wave, at the predefined wavelength, of a second optical length from the splitter to the mixer of a portion of the modulated radiation that is scattered from the optical element into the mixer. A photodetector receives the mixed radiation from the mixer.