Two dimensional microscanners with large horizontal-vertical scanning frequency ratio for high-resolution laser projectors

We present two designs of two-dimensional gimbal microscanners with low vertical-scan frequencies of 70 Hz and 330 Hz and a high horizontal scan frequency of 30 kHz. The scanners are fabricated in a 30 μm silicon-on-insulator with backside structures for both mirror and gimbal-frame. The backside structure under the frame increases the frame weight and effectively reduces the resonant frequency of the rotation springs. The slow vertical scan can thus be achieved without reducing the spring width dramatically. A patterned backside structure also reinforces the mirror plate during actuation such that the root-mean-square dynamic deformation of the 1 mm diameter mirror is less than 44 nm (λ/10 for blue) at 10 degrees mechanical scan angle. A microscanner is installed into a prototype laser projector to demonstrate its capability of producing high quality images.