Crosstalk analysis of 1 m to 10 m laser phase-shift range finder

A heterodyne phase-shift laser range finder has been developed for the measurement of distances of 1 m to 10 m. An analysis of the crosstalk between the current source and the photoelectric receiver of this device permits prediction of the accuracy of the setup. For example, when the amplitude of the crosstalk is proportional to the modulation frequency and for a given photoelectric signal-to-induction ratio of 30 at 10 m, the maximum corresponding error is about 5 cm. To determine the magnitude of the crosstalk, we propose a model taking into account that the amplitude and the phase-shift of the induced signal depend on whether the coupling is inductive or capacitive. Crosstalk modeling shows that very slight inductive or capacitive coupling is sufficient to affect distance measurement.