Two-photon dual-comb LiDAR for industrial applications

Common industrial optical metrology techniques are interferometry-based and therefore limited to short-range measurements of displacement, rather than absolute distance. Since such techniques rely on fringe counting to measure larger distances, they are vulnerable to any interruption of the beam during the measurement, which would require the measurement to be terminated and restarted. Our technique, two-photon dual-comb LiDAR (2phDCL) offers an alternative to interferometry which is capable of rapid, absolute distance measurements over long ranges (>1m) and is not inhibited by beam blocking. Our previous demonstrations were performed with compact, eye-safe Er:fibre lasers and achieved distance measurements with tens-of-µm single-shot precisions, and hundreds-of-nm precisions within two seconds of averaging. We have since developed 2phDCL to enable simultaneous ranging to multiple targets and found no degradation in measurement performance. We extended this capability to provide simultaneous distance measurements to three points on a target object, allowing simultaneous acquisition of range and pose. Given the impressive measurement precisions, the ability to perform multiple measurements simultaneously, and the immunity to beam blocking, we believe 2phDCL has the potential to become the optical metrology technique of choice in certain applications. The technique could immediately offer advantages to existing machines in terms of faster calibration, and we anticipate applications in the real-time tracking of moving components to enable in-process verification of machine paths.