Patent ID: 8873218

Claim:
An actuator comprising: a substrate; a lower electrode disposed on the substrate; an upper electrode opposed to the lower electrode, a distance between the lower electrode and the upper electrode being variable; a support having one end fixed to the substrate and one other end connected to the upper electrode, the support supporting the upper electrode, the support having a creep resistance higher than a creep resistance of the upper electrode; and a driving unit connected with the lower electrode and the upper electrode and being configured to supply a driving voltage between the lower electrode and the upper electrode, the lower electrode and the upper electrode forming a formed capacitance, a pull-in capacitance being the formed capacitance when a pull-in voltage is applied between the lower electrode and the upper electrode, the formed capacitance being configured to change in accordance with a change of an absolute value of a potential difference between the lower electrode and the upper electrode, a ratio of the formed capacitance to the pull-in capacitance changing in accordance with the change of the absolute value, a change rate of the ratio with the change of the absolute value changing in accordance with the change of the absolute value, the absolute value including a first region and a second region, the first region being not less than the pull-in voltage, the second region being larger than the first region, the change rate in the first region being higher than the change rate in the second region, and the driving voltage being in the second region.