The invention relates to an optical scanner, an actuator, an image display device and a head-mounted display. In a universal joint structure containing a movable part, wiring break connected with a strain detection element can be restricted via the optical scanner and the actuator; actions of the strain detection element winding a first shaft can be applied; and the image display devcie and the head-mounted display comprises the optical scanner and possesses excellent reliability. The optical scanner includes a movable portion that is provided with a light reflection portion and is swingable around a first axis; a frame body portion that is swingable around a second axis; a first shaft portion that connects the movable portion and the frame body portion; a fixed portion; a second shaft portion (14a, 14b) that connects the frame body portion and the fixed portion; a strain detection element (51) that is disposed in the second shaft portion (14a) to detect deformation of the second shaft portion; a first signal processing portion to which a detection signal of the strain detection element is input and that outputs a signal based on bending deformation of the second shaft portion; and a second signal processing portion to which a detection signal of the strain detection element is input and that outputs a signal based on torsional deformation of the second shaft portion (14a).
Optical Scanner, Actuator, Image Display Device, And Head-mounted Display