Scan lens and an optical scanner system incorporating two deflectors

A scanner configured to provide a two-dimensional scan of a radiation beam moving along a path, comprising:

• (1) a first deflector for deflecting the beam through a first scan direction at a first angular velocity;
• (2) a second deflector for deflecting the beam through a second scan direction at a second angular velocity, said second scan direction being substantially orthogonal to said first scan direction;
• and
• (3) a lens, said lens comprising three groups of lens elements in order:
• a negative group with a front-most lens element concave to the front,
• a first positive group of lens elements having at least two positive power lens elements and no negative lens elements, the front most lens element of said first positive group having its strongest surface facing the rear, and
• a second positive group of lens elements, said second positive group having stronger optical power than said first positive group, said second positive group including at least one positive meniscus lens component which is concave to the rear, wherein ##EQU5## where efl is the focal length of said lens, efl.sub.1 is the focal length of said first negative lens group, efl.sub.2 is the focal length of said first positive lens group and efl.sub.3 is the focal length of said second positive lens group, said lens being located downstream in the path of the beam from said deflectors for focusing the beam to a spots said scan lens having appropriate distortion characteristics to ensure that a linear velocity of the spot is proportional to said first and second angular velocities.