PROBLEM TO BE SOLVED: To provide a structure in which pull-in does not occur when a drive voltage is increased to increase a movable amount in an actuator including a comb-teeth electrode and a variable shape mirror using the actuator.SOLUTION: An electrostatic comb-teeth actuator 101 includes: a fixed comb-teeth electrode 108 that extends from a support member 105 an elastic member 104 that connects a movable member 103 with the support member and a movable comb-teeth electrode 106 that extends substantially parallel to the fixed comb-teeth electrode from the movable member, and engages with the fixed comb-teeth electrode at an interval. A gap (A) between the movable comb-teeth electrode located inside and the fixed comb-teeth electrode is smaller than a gap (B) between the outermost movable comb-teeth electrode and the support member facing the outermost movable comb-teeth electrode, and a predetermined relational expression represented by using a width w, a thickness t and the like of the outermost movable comb-teeth electrode is satisfied.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2016,JPO&INPIT【課題】櫛歯電極を含むアクチュエータやそれを用いる可変形状ミラーにおいて、可動量を大きくするために駆動電圧を大きくするときにもプルインが起こらない構造を提供する。【解決手段】静電櫛歯アクチュエータ101は、支持部材105から延出する固定櫛歯電極108と、可動部材103と支持部材とを繋ぐ弾性部材104と、可動部材から固定櫛歯電極と略平行に延出しこれと間隙を隔てて噛み合う可動櫛歯電極106を有する。内側に位置する可動櫛歯電極と固定櫛歯電極とのギャップ(A)は最外の可動櫛歯電極と対向する支持部材とのギャップ(B)より小さく、最外の可動櫛歯電極の幅wや厚さtなどを用いて表される所定の関係式が満たされる。【選択図】図1
