| Chronology | Current Month | Current Thread | Current Date |
| [Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
Lenses are essentially smoothly-joined arrays of microscopic prisms. It..
is possible to combine two lenses, one of them "upside-down" (one concave
and the other convex), so that the composite focal length is less than
that of just one lens, but the frequency-dispersion effects are
minimized. The result is the "color corrected" lens.
William Beaty