Apparatus for synchronously scanning a flat platen with a rotating mirror

A system for scanning a flat object surface with a rotating mirror at a constant scan velocity V.sub.o including:

• a flat object surface,
• a rotatable mirror disposed relative to said object surface to scan the same,
• a mirror drive operatively connected to said mirror to impart a variable angular scan velocity w to said mirror according to the following relationship:
• w = (V.sub.o Cos.sup.2 .theta./Y)
• wherein:
• w = Angular velocity of mirror
• V.sub.o = Velocity of scan along object surface (constant)
• .theta. = Angle at any instant between principal ray and normal to object plane
• Y = Normal distance from object surface to mirror axis (constant)
• said mirror drive including a pivoted mirror drive arm operatively connected to said rotatable mirror, a linear drive means acting at a constant moment arm R from the pivot axis of said drive arm and operatively connected to said drive arm and slidable relative thereto so that said moment arm R is constant during movement of said drive means, said drive means being movable at a constant linear velocity V.sub.d and driving said mirror drive arm at an angular velocity 2w according to the following relationship:
• 2w = (V.sub.d Cos.sup.2 2.phi./R)
• wherein:
• 2w = angular velocity of mirror drive arm
• V.sub.d = linear velocity of drive means (constant)
• 2.phi. = angle at any instant between mirror drive arm and its position at center of scan
• R = moment arm - drive means to mirror axis (constant)
• and reduction means operatively connecting said mirror drive arm to said mirror by which the angular displacement of said mirror is half that of said drive arm.