Patent ID: 7755809

Claim:
A laser scanning optical system having a semiconductor laser, a collimator lens that converts a plurality of light beams emitted from the semiconductor laser into parallel light, and an aperture that defines a diameter of a spot of the light beam on an image carrier, and the system scanning the light beams emitted from the collimator lens and exposing simultaneously a plurality of lines on the image carrier, wherein the laser scanning optical system has a converting device that converts an aspect ratio of a profile of the light beam exited from the semiconductor laser, wherein the converting device converts the plurality of light beams, and wherein when it is assumed that a main scanning direction is a beam scanning direction in the laser scanning optical system and a sub-scanning direction is a direction perpendicular to the main scanning direction, Am < 1 ( cos 2 ⁢ θ ′ m ⁢ ⊥ 2 + sin 2 ⁢ θ ′ m ⁢  2 ) [ Equation ⁢ ⁢ 1 ] As < 1 ( sin 2 ⁢ θ ′ m ⁢ ⊥ 2 + cos 2 ⁢ θ ′ m ⁢  2 ) [ Equation ⁢ ⁢ 2 ] L = ⁢  × β × fB fA × cos ⁢ ⁢ θ ′ [ Equation ⁢ ⁢ 3 ] m ⊥ = 2 × fA × tan ⁡ ( ⊥ α ⊥ 2 ) , and [ Equation ⁢ ⁢ 4 ] m ⁢  = 2 × fA × tan (  ⁢ α  2 ) [ Equation ⁢ ⁢ 5 ] hold, where Am is a width of the aperture in the main scanning direction; As is a width of the aperture in the sub-scanning direction; m⊥ is a diameter of an elliptic light beam in a long axis direction; m∥ is a diameter of the elliptic light beam in a short axis direction; fA is a focal length of the collimator lens; fB is a focal length of a back focus lens; α⊥ is a divergence angle in a direction perpendicular to lining of semiconductor laser emitting points; α∥ is a divergence angle in a direction parallel to the lining of the semiconductor laser emitting points; β is a disposition interval of the semiconductor laser emitting points; θ′ is a rotation angle formed by the lining direction of the semiconductor laser emitting points and a main scanning plane; Δ⊥ is a conversion coefficient of the converting device corresponding to the direction perpendicular to the lining of the semiconductor laser emitting points; Δ∥ is a conversion coefficient of the converting device corresponding to the direction parallel to the lining of the semiconductor laser emitting points; and L is a line pitch of an exposing light beam in the sub-scanning direction.