A Leading Trend-Setter in Anti-Reflective Lens Technology: Katharine Blodgett
If you have ever purchased a pair of glasses, you were probably offered the option for an anti-reflective – also known as AR or anti-glare – coating on your lenses during the consultation process. But you may not have known – and still may not know – the purpose of an AR coating. An AR coating is applied to a lens to reduce reflection, which in turn improves visibility and contrast. Such coatings are also applied to other glass surfaces – like store windows, showcases, clock faces, car dashboards and camera lenses – so you can see directly through them. Although this clear or “invisible” glass technology is widely popular today, it is not new. In fact, it’s been around for nearly 80 years. Carl Zeiss patented the technique for the production of AR coatings on lenses, which forms the basis of standard procedures used today, in 1936. The first AR coatings were a German military secret used in confidential operations until the early 1940s.
In 1938, physicist Katharine Blodgett – the first female scientist hired by General Electric – patented the first AR coating for glass. Blodgett worked with Nobel Prize-winning research chemist Irving Langmuir, who created a technique for creating single-molecule thin films on the surface of water. Together, Blodgett and Langmuir explored using the technique on lipids, polymers and proteins, creating monomolecular coatings designed to cover surfaces of water, metal and glass. These special coatings were oily and could be deposited in layers only a few nanometers thick. Blodgett then discovered that by repeatedly dipping a metal plate into water covered by a layer of oil, she was able to stack oil layers onto the plate with molecular precision. After applying 44 monomolecular layers to a piece of glass, the glass allowed for the transmission of more than 99 percent of natural light, creating what became known as "invisible" glass. The visible light reflected by the layers of film eliminated the reflections created by the glass. This was the one of the earliest iterations of the AR coating.
The first versions of “invisible” glass were not consumer friendly or conducive to mass production, as the oily, soapy film that eliminated the glare moving through the lens surface could easily be wiped away. That is not the case today. Modern AR coatings are applied by a method called vacuum deposition technology. Lenses are first cleaned and buffed so that no scratches, imperfections or dust remain. They are then heated to remove moisture and gas that may remain on the surface. Once the lenses are secured in a vacuum-sealed machine, beams of electrons are focused onto a small crucible that contains a series of metal oxides in separate compartments. When the coating materials are bombarded by electrons, they vaporize within the coating chamber and adhere to the surfaces of the lenses, creating a uniform, microscopically thin optical layer on the lens. This coating is imperceptibly thin and extremely durable, making lenses more water and scratch resistant, and smudge proof.
AR coating technology continues to evolve, making lenses less visible in their frames and more comfortable for the glasses wearer. Here is a comparison of glasses with and without anti-reflective lenses. The next time you visit your eye care provider and select your new glasses, consider anti-glare lenses and notice the improvement in your vision! For more information about lens treatments, visit http://www.thevisioncouncil.org/content/lens-treatments/adults.