Lens system for deflected light beam

摘要

A lens system for use in a light beam scanner for deflecting a monochromatic or quasi-monochromatic light beam, the lens system being disposed between a deflection point about which the light beam is deflected and a surface to be scanned in the light beam scanner. The lens system comprises an f theta lens and a corrective lens. The f theta lens comprises two positive-meniscus lenses with their concave surfaces directed toward the deflection point, the f theta lens having an effective deflection angle of at least 50 degrees. The corrective lens cooperates with the f theta lens in constituting a surface irregularity correcting optical system and is disposed between the f theta lens and the surface to be scanned. The corrective lens comprises a toroidal lens capable of correcting surface irregularity and curvature of field.