The first record of A/R research was done by an Englishman, Taylor, in the late 1600's. He noticed that very old lenses allowed more light to pass through them than new lenses. We now know that this phenomenon was caused by oxidation of the surface of the glass lens over many years. This oxidation resulted in a layer, which acted as a simple A/R coating. Unfortunately for Mr. Taylor, he never discovered the reason for his observation nor was he able to duplicate it in the lab.
The Carl Zeiss Company in Germany developed the first man-made A/R coating. 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. Today’s coatings offer superior light transmittance, clean ability, and durability through the use of advanced chemical design and manufacturing.
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%. This increase in transmittance directly benefits
visual acuity with clearer, sharper
images.