A Fresnel lens collimates a light modulated by an image signal and outputs a collimated light. A diffusion member diffuses the collimated light and outputs a diffused light. A driver continually moves the Fresnel lens or the diffusion member on a predetermined trajectory within a plane parallel with a screen. A spring member couples the Fresnel lens or the diffusion member with a casing, including a first deformation plane flexible in a first direction within the plane, and a second deformation plane flexible in a second direction substantially perpendicular to the first direction within the plane, while it is not flexible in a direction perpendicular to the plane.