Coherent-burst laser ranging: decoupling resolution and unambiguous range

A novel signal encoding and decoding method for laser ranging is proposed and experimentally demonstrated. The coherent-burst method uses a quasi-continuous interrupted burst of modulated laser radiation to achieve high-precision ranging at all distances. Both time of flight and phase shift are determined based on an amplitude-modulation pattern that has electronic coherence with a master oscillator. High-frequency modulation provides high absolute precision, while measured temporal delay from transmission to reception eliminates potential uncertainty from aliasing. The method is demonstrated with low-power diode lasers that can be modulated at frequencies in excess of 250 MHz.