Synchronized microscanner array for large aperture receiver optics of LIDAR systems

Abstract

Traditional laser scanners for 3D distance measurement involve expensive, heavy, (potentially) slow rotating mirrors for light deflection of the scanning TOF (time of flight) distance measurement, not suitable for compact, robust and highly portable LIDAR system. On the other hand MEMS scanners are limited to small apertures not suitable for a precise TOF measurement. To overcome this problem Fraunhofer IPMS presents a large aperture 1D-MEMS scanner array especially designed for LIDAR applications. It is composed of 2 x 7 silicon mirror elements each having an identical design with comparatively large aperture of 2.51 x 9.51mm² and ±30° optical scan range. All mirrors are driven electrostatically resonant with identical frequency close to design frequency of 250 Hz. By driving control all single scanner elements are synchronized to identical phase and amplitude in respect to a master scanner. This results in a large effective scanner aperture of 334 mm² for the receiver optics and a filling factor of 80 %. To guarantee the synchronized operation the paper discusses in detail the scanner design to enable a sufficiently large frequency bandwidth of all scanner elements to the compensate frequency tolerances caused by fabrication and packaging. In comparison to LIDAR systems with conventional scanner components, the large aperture 1D-MEMS scanner array enables 3D-LIDAR systems to become significantly smaller, more robust and (potentially) less expensive, also higher scan rates can be realized without additional efforts (e.g. no air bearings are needed)

B7.4 - Application Specific Micro Scanning Mirrors

“…9). The receiver optics use a synchronized 2 x 7 array of 14 identical scanner elements, each with 2.51 x 9.51 mm² per single mirror element, resulting in a total aperture of 334 mm² and filling factor of 80 % [13]. The mirrors' oscillations are synchronized to the sending master mirror in frequency and phase by driving control using hybrid integrated optical sensors for position feedback of each scanner element.…”

Electromagnetically actuated biaxial scanning micromirror fabricated with silicon on glass wafer

“…variety of MEMS devices. A MEMS scanning mirror using electrostatic actuation mechanism has been developed for adaptive raster scanning applied to the 3D ToF (Time of Flight) laser camera (Sandner et al 2010;Sandner et al 2014). In spite of the small power consumption and fast response time, the electrostatic actuation mechanism is limited to relatively small displacement and high actuation voltage.…”

A New Two-Axis Optical Scanner Actuated by Piezoelectric Bimorphs

“…Sandner and others developed a MEMS scanner array with large aperture to improve the traditional laser scanning measure system (Sandner et al 2010). But the array design greatly increased the complexity of control and operation.…”