PURPOSE: To correct a focus shift caused by a temperature variation, while using a plastic lens for a second image forming optical system, and simultaneously, to simplify the constitution of a collimator lens. ;CONSTITUTION: The device is constituted of a first image forming optical system 2 for forming an image linearly on the reflecting surface of a deflecting device with respect to light from a light source, the deflecting device 6, and a second image forming optical system 7 for converging a light beam deflected by the deflecting device onto the surface to be scanned, a second image forming optical system has an anamorphic plastic lens, and a first image forming optical system 2 is constituted of a glass spherical lens 3 of positive power, a non-spherical plastic lens 4 of negative power, and a glass cylindrical lens 5. Accordingly, simultaneously with a temperature compensation, the number of lens pieces of collimator lenses is decreased to half (constituted of two pieces of the glass spherical lens and the plastic non-spherical lens), and a high resolution light beam scanning optical device using the plastic lens of an extremely simple constitution as the whole device can be realized.;COPYRIGHT: (C)1993,JPO&Japio
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