A method of measuring the distance to an object by radiating a periodic amplitude-modulated optical signal to the object and detecting the phase difference between the radiated optical signal and a reflected optical signal from the object includes: generating a first photo-detection control signal to control the periodic amplitude-modulation of the radiated optical signal; generating a mask signal activated at least during a shuttering duration for resetting the voltage level at a sensing node; and generating a second photo-detection control signal based on Boolean combination of the first photo-detection signal and the mask signal such that the second photo-detection signal is deactivated or masked at least during the shuttering duration.