Achromatic lenses are very common type of viewer lenses, they consist of two or more lense elements,which
have been corrected for chromatic aberration with respect to two selected wavelengths, The elements must
be fixed in relation to one another by either mounting or cement.
Achromatic Lenses are designed to specifically function within the infrared, visible, or ultra-violet wavelength
ranges, and they are not symmetric devices. They must be installed with the correct front-to-back orientation
(thicker element usually faces the eyes). If installed incorrectly, with the lens orientation installed backwards
the result will be extensive distortion and aberration.