| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical scanner in which the returning light from a diffraction face is attenuated, diffracted light of unnecessary order or scattered light is effectively eliminated, to provide an optical write-in apparatus, and to provide an image forming apparatus in which a high quality picture is formed by using the optical write-in apparatus. SOLUTION: The optical scanner is composed of: a pre-deflector side optical system for shaping a plurality of luminous fluxes emitted from a light source part 1 and introducing the luminous fluxes to an optical deflector 5; and a scanning lens system 6 which guides and focuses the plurality of luminous fluxes deflected with the deflector 5 on a single face to be scanned 8. The pre-deflector side optical system has a linear image forming lens 4 made of resin and having the function to condense the luminous fluxes in a subscanning direction, the linear image forming lens 4 has a diffraction face, and the diffraction face is provided on the second face of the linear image forming lens 4. The face shape of the diffraction face of the linear image forming lens 4 is set so that the power of the diffraction part and the power of the refraction part are canceled. COPYRIGHT: (C)2008,JPO&INPIT
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