As far as I know "varies the frequency of the transmitted light and measures the freq and phase delay" is the standard way of measuring ToF in case of lasers. Y

As far as I know "varies the frequency of the transmitted light and measures the freq and phase delay" is the standard way of measuring ToF in case of lasers. You modulate the laser diode by a signal of a wide range of frequencies and you subtract returned signal (after cleanup). The observation is done on a spectrum. Low frequencies give you wide range but low precision and high frequencies higher precision but lower range but you can use them enhance precision of the former.