troubleshooting tips
Debunking Optical Myths: Part II
by Karlen McLean, ABOC, NCLC
Debunking optical myths can help keep your work on the right track, so here are more myths—busted.
AR DURABILITY
Myth: Vigorously cleaning antireflective lenses can rub the coating off over time.
BUSTED: Although this may be true of basic AR coatings of years ago, the latest and greatest generations of AR stacks, and the processes used for these stacks, now have very good resistance to wear.
Many AR top coatings have gained a better position by being hydrophobic/oleophobic with added durability factors that harden the final product during the application process. Bayer ratio figures (a durability test for lenses) have gone up from using these advanced final layers.
In addition, some newer ARs such as iCoat's Stainless are created with an ion-assisted vacuum deposition process that creates highly impacted AR layers that make them more durable and less susceptible to wear.
Thus, cleaning today's premium AR lenses has a less negative impact on the AR coating. Some recent test results, with thousands of rub cycles back and forth, indicate that today's AR coatings are far superior in cleanability and longevity. With proper lens care and avoidance of unusual abuse, the life of AR lenses can increase multifold.
—Tom Pfeiffer, national sales manager, iCoat Company
POLARIZED SEPARATION
Myth: Polarized lenses lose their effectiveness over time and can delaminate.
BUSTED: It is true that polarized lenses of old delaminated, and, if subjected to a lot of heat, there could be some minor loss in polarization efficiency.
Those days no longer exist with premium polarized lenses. Many new and breakthrough advances in technology have overcome all of the issues associated with delamination and polarization efficiency.
In construction of the NuPolar lens, for example, the polarizing film that's used is very thermally stable and even when subjecting it to temperatures in excess of 212 degrees F (100 degrees C), the film retains all of its polarizing efficiency.
The methods used to encapsulate the polarizing film within the lens are much improved so that delamination does not occur.
—Dr. J. Sidhu, Younger Optics EB
| Mirror Matters |
|---|
| MYTH: Mirror lenses are mostly for good looks; there are no real optical benefits to mirror coatings on spectacle lenses. BUSTED: It's well-known that mirror coatings provide cosmetic appearance benefits for both men and women. The true benefits of mirrors, however, are experienced when the mirror coating is applied in combination with a polarized lens and a backside AR coating. Adding mirrors to a polarized lens eliminates glare and even blinding glare, and provides 100 percent UV blockage, visual clarity, and true color enhancement. Adding backside AR provides protection from backside glare, eliminating annoying glare from being reflected back into the eye. Selecting a high quality mirror coating is important. For the durability of the product, a mirror with a premium integrated scratch coating, and, for ease of cleaning, a super hydrophobic topcoat, such as Essilor's Crizal Sun Mirrors with Scotchgard Protector, is required. —Bill Markham, technical market manager, Essilor of America |
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