PURPOSE: To reduce the size and cost of a device on the whole so as to be controlled with an optical system composed of only one lens for shaping luminous flux section by using such a lens for satisfying a specified condition.

CONSTITUTION: The light incidence surface of a glass-molded aspherical lens 1 is toric surface (surface of 90° rotational symmetry having different curvatures for two orthogonal directions) which has larger curvature in a direction (V direction) where the radiation angle of LD (semiconductor laser) light is large than in a direction (H direction) where the radiation angle is small. Then diverged V-directional LD light is converged on the light projection surface of the lens 1 to the same diameter with H-directional luminous flux. Assuming that the convex curved surface on the side of the LD 2 is positive, the curvature of the light incidence surface is represented as RIN1>RIN2. Here, RIN1 and RIN2 are the curvature values of the light incidence surface of the lens 1 in the V direction and H direction. Denoting the curvature values of the light projection surfaces of the lens 1 in the V and H directions, ROUT1>ROUT2.