PURPOSE: To obtain always specified intensity of diffracted light, by changing the polarization state of the light made incident to a hologram by an electrooptic element and making the same confirm to the grating direction of the hologram changing with the rotation of a hologram rotating body.

CONSTITUTION: Holograms H consisting of linear gratings at equal intervals are concentrically and multisegmentally recorded on a hologram disc 1. The disc 1 is designed to be rotated by a rotating means such as a motor 2. On the other hand, reproduction light L1 is emitted by a laser light source 3 and is made incident through a cylindrical lens 4 and a plane mirror 5 to the holograms H on the disc 1. The scanning light L2 diffracted from the hologram H passes through a plane mirror 6 and an f.θ lens 7 and is imaged through a cylindrical lens 8 on the scanning plane. If the disc 1 is rotated in this state, the light spot on the scanning plane 9 moves in the direction of penetrating the plane of the figure whereby the scanning is accomplished.