Error introduced by analog to digital conversion of a set of laser pulses can be reduced by shifting the clock reference time associated with the firing of the laser pulse. A timing offset module shifts the timing reference of each laser pulse. Digital codes generated by the ADC from the received signals are realigned and summed eliminating systematic error introduced by clock driven operations of the ADC. A comparison of the total ADC output of detected laser pulses over a select number of clock intervals enables a return signal to be distinguishable over the systematic error.