| 摘要 |
PURPOSE:To keep unevenness of pitch occuring in the inclination of a rotary mirror small and make scanning light point sufficiently small by using a convex cylindrical lens and a concave cylindrical lens having refracting power only in the direction perpendicular to the scanning direction within the scanning plane. CONSTITUTION:A convex cylindrical lens 36 having refracting power only in the dirction perpendicular to the scanning direction in the scanning plane is disposed in the position close to the scanning plane 35, and further a concave cylindrical lens 31 having refracting power only in the direction perpendicular to the scanning direction within the scanning plane is disposed between a laser light source 30 and a rotary mirror 33, between the rotary mirror 33 and condensing lens 34 or in proximity to the rear of the condensing lens 34. Here, if it is assumed that the rotary mirror 33 incline by DELTAtheta with respect to the X axis as shown in the sign 33', then the luminous flux out from the lens 34 becomes parallel luminous fluxes having an angle of approximately 2DELTAtheta with respect to the X axis. Said luminous fluxes deviate by 2DELTAthetaf2 in the Z direction on the scanning plane 35, but since the cylindrical lens 36 is disposed in proximity to the scanning plane, the quantity of said deviation is small. |
