A novel dual-screen projection system using a balance-type micromirror with a piezoelectric actuator

This study presents an innovative dual-screen projection system (DSPS) based on a balance-type dual micromirror structure. This design solves the problem of existing micro-projectors only being able to display a single small picture. The proposed balance-type dual micromirror structure was fabricated using a signal-mask LIGA-like technology with piezoelectric actuation to form a DSPS. The DSPS consists of dual micromirrors as a fast axis, an eccentric structure as a slow axis, and slender piezoelectric actuators. A Y-shaped beam connects two micromirrors to achieve a balance-type dual micromirror structure in which the synchronous scanning of both micromirrors form motion behaviors that approximate to a balance. Experimental results show that the driving frequencies of the slow axis and the fast axis are 3.75 kHz and 11.7 kHz, respectively. The mechanical deflection angles of the slow axis and the fast axis are capable of achieving 2° and 9.6°, respectively, with an applied voltage of 30 V pp . The device can simultaneously display DSPS scanning pictures in a Lissajous scanning manner as dual square patterns, dual heart patterns, a pair of rectangular patterns, and a pair of elliptical patterns. The proposed device achieves the simultaneous display of two patterns with a projection resolution of 320 × 240. Therefore, this DSPS is applicable in scenarios that require dual identical projection screens, such as head-up and head-mounted displays, and when two identical images are needed for both the left and right eyes.