Composition of Various Glass lenses

**Aarlan** · 07-01-2005, 04:45 PM

I left my textbooks in my other office.

Does anyone have a link for the list of the %chemical component of the various glass lenses (Crown, PGX, HiLite, etc). Also in one of my Chem textbooks the author discussed the properties of glass, borosilicate and the like, and one of the uses he stated was use in CONTACT LENSES!?!?!?! Didn't we stop using glass for CTLenses in the 1930's or 40's?

AA

**QDO1** · 09-26-2005, 03:44 PM

not sure, but does anyone else get itchy hands when hand edging PBX oR PGX?, must be something in it, wear latex gloves now

**chip anderson** · 09-26-2005, 04:36 PM

Aarlan: I am pretty sure contact lenses were glass until 1948.

Somewhere at home I have a book that states composition of lenses, what they filter and appearently a lens to allow every visible wave length.

It even has index of opaque materials like gold, which I never comprehended.

If I find it, I will tell you what it is.

Chip

**Darryl Meister** · 09-27-2005, 01:31 PM

Historically, crown glass was made from roughly 70% quartz sand (for silica), 12% lime, 15% soda, and small quantities of potassium, arsenic, antimony, and borax. High-index glasses contain significant quantities of metal oxides, such as lead (for flint glass), barium, titanium, and lanthanum. Corning's photochromic glasses include silver halide crystals (silver and halogen ions).

It even has index of opaque materials like gold, which I never comprehended.

Yes, as odd as it seems, many opaque materials can have a "complex" index of refraction, which is related to the dielectric constant of the material. This is probably useful for thin film calculations when these materials are used for AR coatings and such, though one of the coating engineers -- like Coda -- might have a better explanation.

**chip anderson** · 09-27-2005, 03:35 PM

Thanks Darryl.:cheers:

**coda** · 09-27-2005, 05:40 PM

Originally Posted by Darryl Meister

Yes, as odd as it seems, many opaque materials can have a "complex" index of refraction, which is related to the dielectric constant of the material. This is probably useful for thin film calculations when these materials are used for AR coatings and such, though one of the coating engineers -- like Coda -- might have a better explanation.

Darryl, with you there I don't know why Zeiss-Sola employs any engineers at all.

Gold has some very interesting optical properties and as a result is occasionally used in complex thin film coatings, particularly absorbing mirrors. Absorbing mirrors are an easy way to make sunglasses without tinting the bulk lens material. It's possible to make a coating that has a very low back surface reflection, moderate to high front surface reflection and high absorbtion; deposit it on glass and you get a nice pair of sunnies!

Gold, when added in very small, well disbursed amounts to glass can also result in some 'interesting' optical properties though nothing that the ophthalmic industry is likely to be interested in.