| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical scanner having a compact apparatus configuration in which variations in the curvature of image face on a face to be scanned, the subscanning magnification and optical scanning velocity in main scanning direction are reduced, further the shift of focusing in the subscanning direction on the face to be scanned due to the variations in the oscillation wavelength of a luminous flux and in environment is small. SOLUTION: An imaging optical device 40, which is arranged between a polygon mirror 30 and the surface of a photoreceptor drum 1, focuses scanned light on the surface of the photoreceptor drum 1 and keeps the scanning velocity approximately constant, includes: a first scanning light lens 41 having a positive power in the main scanning direction and a negative power in the subscanning direction; and a second scanning light lens 42 which is arranged on the closer side to the photoreceptor drum 1 than the first scanning light lens and has a negative power in the main scanning direction and a positive power in the subscanning direction. Further, a diffraction optical element 24 is provided on the surface of a cylindrical lens 23 located on the path of a light beam between the light source 10 and the polygon mirror 30. COPYRIGHT: (C)2009,JPO&INPIT
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