| 摘要 |
A laser beam emitted from a laser light source is shaped into a substantially parallel beam in the main scanning direction, and is condensed in the vicinity of a deflecting surface of a deflector in the sub scanning direction by a light source optical system. The laser beam deflected by the deflector is projected onto a photosensitive body of an image forming apparatus by a scanning optical system. The light source optical system is constituted by one optical element made of resin. The optical element has a reflecting surface having no symmetry axis of rotation, and two transmitting surfaces. The laser beam incident on the incident side transmitting surface is reflected at the reflecting surface, and exits from the exit side transmitting surface. As described above, by providing the reflecting surface with a beam shaping function, the performance change caused when there is a temperature change can be reduced more than when a refracting surface is provided with the beam shaping function. The transmitting surfaces may be provided with a diffracting function.
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