Used for converging or focusing of light, as well as for collimating point sources. Cost-effective alternative to a positive best-form lens when used at infinite conjugate ratio, with collimated light incident upon the convex side. Reduced spherical aberration and near-zero coma when used off-axis.
Used for 1:1 imaging, beam expanders, and beam relay applications. Good positive lens for virtual imaging of real objects and for positive conjugate image ratios from approximately 0.2 to 5 (depending on wavelength). Can also be used for focusing applications at lower f-number. It performs like a bestform singlet lens when used at unit conjugate ratio.
Used to expand light or to increase focal lengths in optical systems, or to balance aberrations from other lenses within a system. Negative focal length diverges collimated incident light. Spherical aberration, and coma are reduced when used at infinite conjugate ratio with collimated light incident upon the concave side.