Presented is a high-resolution AR micro display based on Laser Beam Scanning (LBS) applying a two-dimensional resonantly operated vacuum packaged MEMS mirror with large mirror diameter, high scan frequencies, high Q-factor and large field-of-view (FoV). The image is projected to the retina using a diffractive waveguide leading to a comfortably large eyebox. Advanced control algorithms and image processing methods are implemented to accurately drive, sense and control the biaxial resonant MEMS mirror as well as to optimize image projection quality. Due to a sufficiently large mirror diameter this micro display does not need any beam expansion optics between MEMS mirror and waveguide enabling an ultra-compact projection unit. Resonant operation of the MEMS mirror in both axes and exploiting the significant advantage of a hermetic vacuum package effectively reduces energy loss by damping and thus minimizes drive voltage and power consumption. The display setup demonstrates the successful realization of a small form factor high resolution micro projector that meets important requirements for enabling fashionable AR smartglasses.
The wish for higher-level advanced driver assistance systems requires infrared based ranging systems like LiDAR provided that it offers high speed, wide field-of-view, small size and especially low cost. The only way to combine these attributes is the use of cost-efficient and mass-producible MEMS scanners suitable for automotive applications. In this work we present a wide-angle LiDAR demonstrator for short range applications based on a single resonantly operated MEMS, a single laser and single light detector. The MEMS mirror is capable of tilting ± 45° mechanically and thus enabling a large field-of-view of up to 180°. The incorporated mirror plate has an elliptical shape of 2 mm x 4 mm in size and the overall volume of the MEMS device is less than 0.7 cm3. Low-power microcontroller based closed-loop electronics is used to keep the very high Q device within its resonance frequency range at all times enabling high scan rates of more than 3000 scans per second and accurate position detection better than 0.1°. Both automotive suitability and high energy efficiency is achieved by hermetic wafer-level sealing under vacuum as well as internal piezoelectric drive and sense structures. The demonstrated wide-angle scanning LiDAR further consists of a 905 nm eye-safe pulse laser source operating at up to 200 kHz with an optical peak output power of 30 W as well as a one-dimensional SPAD based detector with 2x192 channels. Together this leads to high density and high resolution point clouds using just a single laser, detector and MEMS scanner.
Presented here is the world’s first resonant 1D MEMS mirror achieving mechanical scanning angles exceeding ±45° and thus providing a field of view of up to 180°. The MEMS scanner features a 2 mm x 4 mm ellipsoid mirror plate and oscillates at a scan frequency of about 1.5 kHz. Integrated sensors and closed-loop control allow for an accurate position detection below 0.1°. To achieve the scan angles as well as to guarantee long lifetime and reliability, the MEMS mirror is hermetically sealed on wafer level by a dedicated glass cover and operated in vacuum.
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