Chuck Knight wrote: > > "Choosing lenses for their optical > qualities" results in a rather short list with CR39 (low index and > thick) or Trivex (high index and thin) becoming the ideal candidates.
Trivex is a pretty low index material as well (1.53 vs 1.50 for CR39). The Abbe number for Trivex isn't nearly as good as that of CR39 (44 vs. 59 respectively). But Trivex is tough enough that it can be safely made with a thinner center thickness than some other lens materials, which makes for a thinner lens overall. High index lens materials tend to have worse Abbe values than low index lens materials, but there's a lot of variation in this regard among materials with similar refractive indices. So from where I stand, it's not absolute Abbe number but a combination of relatively good Abbe number and relatively high refractive index that determines the overall desirability of an optical material. The ability to support a frame from holes drilled in the lens is not an optical characteristic, but it can limit one's choices to materials whose optical characteristics are not a good compromise, e.g. polycarbonate. Chalo -- Check us out at the oft-updated http://glassyeyes.blogspot.com! You received this message because you are subscribed to the Google Groups "GlassyEyes" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/glassyeyes?hl=en
