Patent ID: 8614831

Claim:
An actuator comprising: a movable portion which can swing around a swing axis; a connecting portion which extends from the movable portion and is torsionally deformed according to the swing of the movable portion; and a support portion which supports the connecting portion, wherein the movable portion is formed in a cross shape which includes a pair of first protrusions protruding to both sides of the movable portion along a direction perpendicular to the swing axis and a pair of second protrusions protruding to both sides of the movable portion along a direction parallel to the swing axis in plan view in a thickness direction of the movable portion, and when a length of the movable portion in the direction perpendicular to the swing axis is A, a length of the movable portion in the direction parallel to the swing axis is B, a length of the first protrusion in the direction perpendicular to the swing axis is a, and a length of the second protrusion in the direction parallel to the swing axis is b, the following equations (A) and (B) are satisfied 0.8 × { 1 2 ⁢ ( A - 1 3 A 2 + 1 B 2 ) } ≤ a ≤ 2.0 × { 1 2 ⁢ ( A - 1 1 3 ⁢ ⁢ A 2 + 1 B 2 ) } ( A ) 0.8 × { 1 2 ⁢ ( B - 1 1 3 ⁢ ⁢ A 2 + 1 B 2 ) } ≤ b ≤ 2.0 × { 1 2 ⁢ ( B - 1 3 A 2 + 1 B 2 ) } . ( B )