Chapter 22Scanner/f-θ, Laser Disk, and Collimator Lenses
22.1 Monochromatic Systems
In a system that is truly monochromatic, the designer is no longer constrained by the need to achromatize the lens system. Thus high-index flint glasses can be used in positive elements and low-index crown glasses can be used in negative elements. This is obviously beneficial as regards the Petzval curvature and obviates any need to use the expensive lanthanum glasses for the high-index elements. The resulting lens is, of course, a hyperchromat and is suitable only for use with very monochromatic light sources.
22.2 Scanner Lenses
The scanner lens operates with an oscillating mirror that scans the point image across the field. To minimize the size of the scanning ...