Prevention of stray light reflections in a raster output scanner (ROS) using an overfilled polygon design

Claim 1

An optical scanning system which compensates for unwanted stray light reflections in an overfilled polygon design comprising: a pre-polygon optical system having optical components aligned along a first optical axis, said pre-polygon optical system including: a source of high intensity modulated, collimated light beams, and means to focus the collimated beams in one direction; a polygon scanner having X number of light reflecting facets interposed in an optical path between said pre-polygon optical system and a light sensitive medium, said facets being fully illuminated by incident light to produce scanning beams at some scan angle θ which are reflected towards the light sensitive medium while adjacent facets are at least partially illuminated and reflect at least a portion of the light incident normally thereon as a stray light beam in a reverse direction along said optical path, and a post-polygon optical system having optical components aligned along a second optical axis, and including at least an fθ lens to form an image line exposure of beams reflected from said scanning facets onto a light sensitive medium, and wherein said first and second optical axes are aligned with respect to each other at an angle φ' given by the expression: ##EQU4## where Ω=360/X.