LASER SCANNING OPTICAL DEVICE

摘要

PURPOSE: To make it possible to easily and inexpensively correct the plane tilt of a rotary polygonal mirror with high accuracy by having hologram patterns having a function to diffract and condense a laser beam onto a recording medium on the surface of window glass disposed at a case member. CONSTITUTION: The window glass 12 is arranged in order to expose a photoreceptor 10 in a housing 13 in which a semiconductor laser 1, the rotary polygonal mirror 3, an fθlens system 11 and a turn back mirror 9 are incorporated. The hologram patterns 15 to diffract the laser beam are added on the inner side face of the window glass 12 so as to have a power in a scanning direction and to condense the beam onto the photoreceptor 10. The surface of the window glass 12 having the lens function by the fθlens system 11 and the hologram patterns is so arranged as to put the deflection point on the reflection surface of the rotary polygonal mirror 5 and the image point of the photoreceptor 10 into a conjugate relation with respect to the sub-scanning direction.