| 摘要 |
PROBLEM TO BE SOLVED: To perform stable optical scanning without any increase in cost. SOLUTION: The optical scanner includes: a light source 14; a pre-deflector optical system; a polygon mirror 13; and a scanning optical system, wherein the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, a cylindrical lens 17 and a reflecting mirror. The coupling lens 15 is provided with diffraction surfaces respectively having: an effect of correcting shift in imaging position due to a temperature change concerning the direction corresponding to the main scanning direction; and an effect of correcting shift in imaging position due to a wavelength change concerning the direction corresponding to the sub-scanning direction. Thus, while easiness of machining and low cost are secured, optical performance can be improved. Therefore, stable optical scanning is enabled without any increase in cost. COPYRIGHT: (C)2009,JPO&INPIT
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