ELECTROSTATIC LINEAR MICRO ACTUATOR WITH VIBRATING MOTION (APPLICATION TO THE FOCUSING MECHANISM OF A MINIATURE CCD CAMERA)

A newly developed linear electrostatic micro actuator mechanism employ ing a vibrating motion is described. Features of this mechanism are th at anti-friction bearings are not required, the influence of friction is reduced significantly, and a large stroke is achieved. The moving p art (Slider) of this actuator is sandwiched between fixed electrodes ( Stator), is alternately attached and detached to these fixed electrode s, and actuates linearly on a macroscopic level. Several difficulties have been identified regarding actuators operated by attachmen/detachm ent. The interactive forces, including the accumulation of charge caus ed by contact between each slider and stator, create one of the most d ifficult problems. Our developed actuator incorporates micro stoppers, which prevent the accumulation of charge and other interactive forces on the surface of the slider or the stator. A voltage supply pattern such that the positive and negative charge appear alternately, is empl oyed. The first prototype, casing size is 8 x 8 x 1.2 mm and range of movement is 2.0 mm, has been fabricated by a bulk silicon micromachini ng process and the fundamental feasibility of this vibrating motion me chanism has been confirmed by experiments. This motion mechanism is ap plied to a focusing mechanism of a miniature CCD camera. A micro lens is fitted inside the slider and the focus is adjusted by moving the sl ider (with the micro lens). The size of the prototype focusing mechani sm is 3.6 x 4.6 x 8.0 mm and this achieves a 2 mm range of movement. T he minimum driving voltage is 60 V and maximum velocity is 1.0 mm/s.