Electrostatic linear micro actuator with vibrating motion (application to the focusing mechanism of a miniature CCD camera)

Abstract

A newly developed linear electrostatic micro actuator mechanism employing a vibrating motion is described. Features of this mechanism are that anti-friction bearings are not required, the influence of friction is reduced significantly, and a large stroke is achieved. The moving part (Slider) of this actuator is sandwiched between fixed electrodes (Stator), is alternately attached and detached to these fixed electrodes, and actuates linearly on a macroscopic level. Several difficulties have been identified regarding actuators operated by attachmen/ detachment. The interactive forces, including the accumulation of charge caused by contact between each slider and stator, create one of the most difficult 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 employed. 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 micromachining process and the fundamental feasibility of this vibrating motion mechanism has been confirmed by experiments. This motion mechanism is applied 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 slider (with the micro lens). The size of the prototype focusing mechanism is 3.6 x 4.6 x 8.0 mm and this achieves a 2 mm range of movement. The minimum driving voltage is 60 V and maximum velocity is 1.0 mm/s.