A self-sensing thermal actuator incorporating micromirror for tracking mechanism of optical drive

In this paper, a novel self-sensing thermal actuator incorporating micromirror is proposed as a fine positioning actuator for precise-tracking mechanism of high-density optical drive. Due to the bimorph effect, a bi-layer cantilever consisting of two materials with different thermal expansion can provide force or displacement With change in temperature. In the proposed thermal actuator, an integrated micromirror suspended by the four identical thermal bi-layer cantilevers is vertically driven to move up-wards by driving voltage. In the meanwhile, the mirror position can be detected by an embedded high-sensitivity piezoresistive sensor. The process flow of the self-sensing thermal actuator incorporating micromirror is presented with the prototypes. The experimental results show that the micromirror can be driven zip to an equivalent 1.14 mu m displacement in tracking, direction by the driving voltage of 3 V. The device also has a measured resonant frequency of 7kHz and displacement sensitivity of 0.04ppm/angstrom to support high bandwidth servo feedback control in optical drive.