Actuator with plurality of torsion bars having varying spring constant

An actuator comprising:

• a support part which supports a movable part;
• and
• a plurality of torsion bars each of which connects the movable part and the support part such that the movable part is capable of swinging around a rotational axis which is along a long direction, wherein,
• the plurality of torsion bars are arranged along a short direction of the torsion bars in a liner symmetric manner with respect to the rotational axis,
• the farther each torsion bar is from the rotational axis, the smaller a spring constant of each torsion bar is,
• at least one of the plurality of torsion bars includes a bending part and connecting parts,
• the bending part includes:
• a first part, a second part, and a third part, each of the first part and the second part extends along the short direction, the third part extends along the long direction and connects the first and second parts,
• one of the connecting parts connects the bending part and the movable part and the other one of the connecting parts connects the bending part and the support part, and
• each of the connecting parts extends in parallel with the rotational axis.