Multi-Element Objectives Overview

Some focusing applications may require a higher
degree of aberration correction than can be achieved
in single lenses such as Best Forms. Whether correction
over larger apertures, several wavelengths or a
wider field is needed, it may be necessary to use multi-element
lens objective.

Aberration Correction

A Best Form lens singlet is corrected for minimal spherical aberration. However, other aberrations will become prevalent in such a lens as field angles, aperture size, numerical aperture or wavelength bandwidth is increased. Coma and astigmatism are the two most important. Both are dependent on field angle. Using a combination of differing optical materials, judicious guessing and computer controlled lens design software; many lens objectives can be made relatively aberration free. Depending on the F/# and degree of achromaticity, most on -axis focusing applications can be satisfied with objectives having three lenses or less.

		Focusing Objective Theory For your convenience we offer a detailed explanation on how beam expanders work in our white paper on Beam Expander Theory. Click here to read.