System integration of hybrid assembled large aperture Micro Scanner Array for fast scanning LiDAR sensors

We present the design and system integration of a hybrid MEMS scanning mirror (MSM) array developed for real-time three-dimensional imaging with a panoramic optical field of view (FOV) of 360  deg  ×  60  deg (horizontal  ×  vertical). The pulsed time-of-flight light detection and ranging (LiDAR) system targets a distance measurement range of 100 m with a video-like frame rate of 10 Hz. The fast vertical scan axis is realized by a synchronous scanning MSM array with large receiver aperture. It increases the scanning rate to 3200 Hz, which is four times faster in comparison with state-of-the-art fast macroscopic polygon scanning systems used in current LiDAR systems. A hybrid assembly of frequency selected scanner elements was chosen instead of a monolithic MEMS array to guaranty high yield of MEMS fabrication and a synchronous operation of all resonant MEMS elements at 1600 Hz with large FOV of 60 deg. The hybrid MSM array consists of a separate emitting mirror for laser scanning of the target and 22 reception elements resulting in a large reception aperture of Deff  =  23  mm. All MSM are driven in parametric resonance to enable a fully synchronized operation of all individual MEMS scanner elements. Therefore, piezoresistive position sensors are integrated inside the MEMS chip, used for position feedback of the driving control. We focus on the MEMS system integration including the microassembly of multiple MEMS scanning elements using micromechanical self-alignment. We present technical details to meet the narrow tolerance budgets for (i) microassembly and (ii) synchronous driving of multiple MEMS scanner elements.