Due to Dr. Who Anniversary Special related internet blackouts I give it 24 hours before anyone actually sees this post.
I realised this week while window shopping that I had no idea how sunglasses are made, the sum total of my knowledge is that you grind the glass until it's i the right shape to focus light properly. I didn't know how the frames are made, how polarisation or tinting is made or how bifocal or multifocals mix their lens shapes.
So this is my summary, the polarisation film is made by spraying a layer of molecules which naturally align parallel to each other which cuts glare from light which is not aligned with the direction of these molecules. Usually glare is aligned horizontal to the ground, reflecting from objects like ocean waves and car windows slanted toward the cool shades wearing individual which is why the molecules are usually aligned vertically on sunglasses. The level of polarisation is affected by how misaligned the light is, so tilting your head may block more or less glare. The only reference to what kind of molecule was in a 1941 patent which described it as an "polyvinyl alcohol [solution] containing oriented molecules of polyvinylene" (Rogers, 1941) but I haven't found anything more recent, or anything suggesting optical manufacturers have updated their methodologies.
As for glass tinting all I could find was that most optical glass is made by immersing the glass in a chemical bath and the tint soaks in to a much greater depth (150 microns) than the thickness of a sprayed coating as was initially tested (5 microns thick).The only chemical I could find which was used for tinting was a combination of layers of titantium oxide and nickel hydroxide, although I couldn't find if these chemicals were in widespread use in this application.
The frames themselves were made by a couple of different processes, differing on the material and style. Wire frames are bent into shape with a collection of different machines which twist through certain angles to make different shape lens frames and bridges which are brazed together. Plastic is injection moulded with a die (metal pieces which act like moulds) which is cut to produce a specific style.
Multifocals and progressive lenses (lenses whose power varies around the lens) are made by using a standard front side of the lens and then the back is ground to different shapes for each patient.
Word of the day/week/whatever: hypoallergenic, as in doesn't cause allergic reactions.
Live fast and die old, please. Or never, you know. Depending on how legitimate these claims are. TED talks are crazy.
1941 Patent: http://www.google.com/patents/US2263249
Berkeley article on new tinting options (new for 1998): http://www.lbl.gov/Science-Articles/Archive/cheap-photochromics.html
No comments:
Post a Comment