Patent ID: 7903311

Claim:
An optical beam scanning apparatus comprising: a light source configured to emit one or plural luminous fluxes; a pre-deflection optical system configured to shape the luminous fluxes emitted from the light source to image the luminous fluxes as a line image in a direction corresponding to a main scanning direction; a light deflecting device configured to separate the luminous fluxes imaged by the pre-deflection optical system in a sub-scanning direction for each of color components using plural deflection surfaces having different angles with respect to a rotation center axis and scan the luminous fluxes against a scanning object in the main scanning direction; a post-deflection optical system, having one or plural first optical elements configured to act on the luminous fluxes for all color components, configured to image the luminous fluxes deflected by the light deflecting device on the scanning object; and a first sensor configured to detect a part of the luminous fluxes deflected by at least one deflection surface having a predetermined angle with respect to the rotation center axis.