P3D Re Fluorite lenses.

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

Tom Hubbin In digest 3383 wrote

>Unless flourite has an index well over 1.60 it is unlikely that flourite
>lenses are much thinner than other contact lenses. The thickness is
>likely to be governed by a minimum thickness that is easy to manufacture
>and not too fragile.

According to "The Microscope" by Conrad Beck the point about fluorite is
that it has a low refractive index and an extremely low dispersion of about
1/95 on the focus. The peculiarity is that it has a larger proportional
dispersion for what he calls the F to G (green to blue ?) rays than many
glasses with higher dispersion ; the figure being 583.      P.J.Homer



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