Cascaded laser scanning towards high-resolution LiDAR

Abstract

We present and demonstrate a cascaded laser scan architecture to achieve a three-fold gain in scan angle. We cascaded multiple piezoelectric MEMS scanners using a high numerical aperture relay lens pair in between scanners, which are located at optical conjugate planes. The cascaded scan architecture comprising 3 scanners is simulated using ray-tracing software. Finally, we conduct experiments using the folded architecture, where the incoming laser beam bounces off the first scan mirror (twice) and the second scan mirror, having nearly identical resonant frequencies of 27.59 kHz, yielding a total optical scan angle of 90 degrees. The observed scan angle exceeds the angle achieved by any single MEMS scanner. One can exploit the use of the back surface of the mirrors, as well as higher numerical aperture lenses to improve the achievable total optical scan to more than double, up to 210 degrees. With further development, the proposed architecture can be integrated into LiDAR systems to achieve high number of resolvable spots on the target, with unprecedented speed and form factor, far beyond what can be achieved with rotating motor or polygon mirror-based architectures.