| 摘要 |
PURPOSE:To facilitate an adjustment operation by providing an aperture plate with a slit which is previously provided with an angle and disposing this aperture plate between a collimator, apart therefrom, and a planoconvex lens for reducing a laser beam in a sub-scanning direction. CONSTITUTION:The aperture plate 13 parted to the planoconvex lens 14 side from the collimator 12 is disposed between the collimator 12 and the planoconvex lens 14. The aperture plate 13 is provided by being regulated in position in a positioning part and is formed with the slit 19 which is previously provided with the angle. The angle corresponds to the incident angle of the laser beam from the mirror provided in the position deviated vertically from a polygon mirror 11 to the polygon mirror 11. The projected image of the laser beam which is projected through the slit 19 then through the planoconvex lens 14 and the mirror 15 onto the reflecting surface of the polygon mirror 11 is, therefore, parallel with the long side of the reflecting surface. The need for adjusting the projected image is eliminated in this way and the execution of only the focus adjustment is merely necessitate for the collimator. |
