Development of a non-contact precision measurement technique using optical frequency combs

We develop a new method for high-resolution, contactless distance measurement based on self-frequency beats of optical frequency combs. We use two optical frequency comb lasers with Rb-stabilized repetition frequencies for accurate distance measurement. The repetition frequencies of the optical frequency combs differ, allowing down-conversion of gigahertz to several megahertz self-beats without an RF frequency oscillator. A high-resolution, high-sensitivity lock-in amplifier measures the phases of the megahertz frequency signals. The method is applied to distance measurement for objects with rough surfaces separated by several meters.