Phase shift laser range finding is widely used in many fields with its high measurement resolution. Measuring rate and resolution of the whole range finding system is determined by those of phase shift detecting and is influenced by the crosstalk for a given modulation frequency. Based on these

a new magnification of phase shift detecting is proposed which improves the measurement resolution 1/N times without increasing the measuring time. The under sampled technique is adopted to perform multi-frequency modulation in the same system which avoids using the mixer and other accessorial components. These reduce prior art scheme complexities and the influence of crosstalk. Week light with high frequency is incident on the avalanche diode (APD)

the phase of the output signal from APD is delayed over that of the incident light which induces distance measurement error. A new method on suppressing the phase delay is presented by controlling the bias voltage acting on APD. For a modulation frequency of 18.5MHz

a wavelength of 650nm and incident light intensity of 0.5uW

the phase delay of 1.4o can be reduce to less than0.03o .The crosstalk mathematic model is set up. The crosstalk influences on phase shift measurement employing different electrostatic screen are given. The experiment results show that the phase shift measurement resolution is 0.014o and the distance measurement resolution is 0.3mm accordingly when the modulation is 18.5MHz.