| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical scanner furnished with a diffraction lens which gives the effect of a diffraction face to all luminous fluxes and to provide an image forming apparatus. SOLUTION: The optical scanner includes: an incident optical system including a light source which emits luminous fluxes, a coupling lens which couples the luminous fluxes to a following optical system, an aperture which forms the luminous fluxes emitted from the coupling lens, an optical deflection means which deflects the luminous fluxes into the main scanning direction, and a single linear image forming lens which guides the luminous fluxes emitted from the coupling lens system to the optical deflection means and condenses the luminous fluxes onto an optical deflection face as long linear images extending in the main scanning direction; and a scanning lens system which focuses the luminous fluxes deflected with the optical deflection means onto a face to be scanned, wherein the shape of the back cut of the diffraction face of the linear image forming lens is composed of a nested ellipsoids, the ellipsoids of the group have a common center, all ellipsoids are closed, the outermost ellipsoid of the group of ellipsoids includes a rectangle expressed by formula 1 (main scanning direction: Ltanθm + Ay, subscanning direction: Ltanθs + Az). COPYRIGHT: (C)2010,JPO&INPIT
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