Patent ID: 7605963

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 shapes 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 configured to image the luminous fluxes deflected by the light deflecting device on the scanning object; a first sensor configured to detect a part of the luminous fluxes deflected by the light deflecting device; one or plural first optical elements configured to be provided in the post-deflection optical system and act on the luminous fluxes deflected by all the deflection surfaces of the light deflecting device; and a second optical element having positive power in the sub-scanning direction configured to be provided in an optical path between any one of first optical elements and the first sensor and act on the luminous fluxes deflected by all the deflection surfaces of the light deflecting device.