A MICROMACHINED TORSIONAL MIRROR FOR TRACK FOLLOWING INMAGNETO-OPTICAL DISK DRIVES

摘要

An electrostatically actuated polysilicon surfacernmicromachined torsional mirror has been used as a fine actuatorrnfor track following in Optically Assisted Winchester (OAIyTM)rnmagneto-optical disk drives. OAWTM technology combines arnWinchester-style voice coil motor (VCM) as a coarse actuator withrnlight delivery via optical fibers and a read/write head containingrnmicrofabricated optical elements, a coil, and a silicon chiprncontaining the micromachined mirror. The mirror achieves arnresonance of at least 3.5 kHz, an angular deflection range of +/- 2rndegrees prior to electrostatic pull-in, and a pull-in voltage less thanrn150 Volts. Novel fabrication techniques allow for an RMSrnroughness of less than 3 nm on the reflecting surface of the mirrorrnand mirror plate radius of curvature of greater than 10 cm over arntemperature range of 5 to 55 C. Servo bandwidth for OAW diskrndrives has been demonstrated at 3-5 kHz while using the mirror forrntrack following at greater than 35 thousand tracks per inch (ktpi).