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Laser scanning optical system and image forming apparatus

  • US 7,755,809 B2
  • Filed: 11/27/2006
  • Issued: 07/13/2010
  • Est. Priority Date: 12/26/2005
  • Status: Active Grant
First Claim
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1. 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, whereinthe 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, whereinthe converting device converts the plurality of light beams, and whereinwhen 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, whereAm 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.

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