The first man-made A/R coating was developed by the Carl Zeiss company in Germany. Its original use was coated optics for artillery, and to this day many of the improvements in A/R technology can be attributed to military research.
Uncoated Lenses /
Coated Lenses
Differences in index
of refraction of transparent materials cause part of
the spectrum of light rays to bounce back instead of
passing through. This is a reflection. For example,
CR-39, which has an index of refraction of 1.498, will
allow 92% of the visible spectrum to pass through. If
there are two layers of transparent material, then a
portion of the reflected rays from the bottom material
are reflected back and forth until virtually all pass
through the material. The few that do not pass through
result in a residual color, usually in the blue, green,
or gold visible range. The perfect A/R coating would
allow 100% of light through, and would render the
material invisible. Theoretically this is possible, but
the process parameters are so unforgiving that it
probably is not feasible for ophthalmic purposes. But
they are quite close. While a raw CR-39 lens allows 92%
transmission, this lens with an A/R coating achieves
99.3%.