| 摘要 |
An optical beam scanning apparatus and an image forming apparatus having the optical beam scanning apparatus are provided. The optical beam scanning apparatus includes a light source; a pre-deflection optical system; an optical beam deflecting device; a sensor; and a post-deflection optical system. An exit surface of the imaging lens includes a lens-shaped portion for imaging the light flux on a scanned surface of the scanned object, and a totally reflecting surface-shaped portion having a totally reflecting surface for totally reflecting a portion of the light flux from the deflecting surface of the optical beam deflecting device at least two times, and the incident surface of the imaging lens includes a transmission surface-shaped portion having a transmission surface for transmitting the light flux totally reflected by the totally reflecting surface, and the light flux transmitted through the transmission surface is directed to the sensor.
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