P3D Re Apochromatics more info please

[Peter Homer <P.J.Homer@xxxxxxxxxxxxx>]

>
>Doc T quoted :
>
>"apochromatic
>  lenses are made of crystalline fluorite or other unusual types
>  of glasses, have stronger elements (higher curvature)"
>
>Could you explain what this type of glass does better than other types

"According to my Microscopes and Microscopic" life by Peter Healey
achromatic miroscope objectives consist of four lenses including two
compound doublets made up of a plano-concave and biconvex lens each.
Apochromatic lenses incorporate Fluorite (Calcium Fluoride) and correct for
two rather than three colours .
They consist of five lenses including one doublet as with the Achromats and
two triplets consisting of a biconcave lens and two plano convex each.
" Under the Microscope " Alan Curry,Robin F. Grayson Geoffrey R.Hosey  .
Decsribes objectives called smi-apochromatic or fluorite containing some
elements made of fluorite as superior to Achromats but inferior to Apochromats.
"The Microscope " by Wredden also describes fluorites as semi-apochromats
and a compromise between expensive apochromats and cheaper achromats.
                             P.J.Homer




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End of PHOTO-3D Digest 3375
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