Optical system for mechanically scanning with a rotating polyhedral reflector

Claim 1

An optical system comprising a first mirror provided with an aperture in the center thereof and having a concave reflecting surface, said mirror being a body and said aperture being an opening passing through said body, a second mirror having a flat reflecting surface for reflecting a ray bundle reflected on said first mirror toward said aperture, a first lens disposed at said aperture to convert the reflected ray bundle from said second mirror into parallel light, said first and second mirrors cooperating to form an image at a focal point between said second mirror and said first lens, said first lens having a focal point at the first said focal point and producing a ray bundle of parallel light, a polyhedral element disposed in the path of said parallel light for rotation about an axis of rotation thereof and having a plurality of reflecting surfaces, and a second lens for focusing rays reflected from the reflecting surfaces of said polyhedral element to form an image, said second mirror being adapted for reciprocal angular motion about an axis of rotation perpendicular to the axis of rotation of said polyhedral element, means for causing the reciprocal angular motion of said second mirror, and means for causing rotational motion of said polyhedral element, said mirrors and lens being so dimensioned and arranged that the parallel light has a substantially smaller cross-section than said ray bundle.