To provide a laser beam scanning optical device capable of simultaneously adjusting the converged state of a laser beam in the main scanning direction and the sub-scanning direction.
Laser beams radiated from a laser diode 1 are converged on a photosensitive drum 30 through a focusing lens 3, a polygon mirror 6 and a fθ lens 7 and scanned in the direction of an arrow (b). The focusing lens 3 is composed of a spherical lens 3a having a power in the main/sub directions and a cylindrical lens 3b having a power only in the sub-scanning direction. A beam waist detector 10 is installed on a position equivalent to the surface of the photosensitive body, the focusing lens 3 is moved on the optical axis based on the detected result of the relevant detector 10 and the converged position of the laser beam is adjusted.
KOSAKA JUN
HIRAGUCHI HIROSHI
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