To arranged two projection parts by a drive means, etc., while limiting within a narrow angle.

The fixed surface of a variable apex angle prism 21 is supported by an outer frame 22, and the movable surface of the variable apex angle 21 is constituted so as to be driven by a swing actuator 23A being a first drive means and the swing actuator 23B being a second drive means. The swing actuator 23A forms a prism apex angle by making an A-A axis tilted by nearly 45° from a horizontal direction a rocking axis. Further, the swing actuator 23B forms the prism apex angle by similarly tilting the movable surface of the variable apex angle prism 21 by making a B-B axis orthogonally intersecting with the A-A axis the rocking axis.