Plastics for LED optics

[MacGyverS2000]

This question might be better proposed on an optics forum, but this was the closest I could find on Eng-Tips...

Looking for suggestions on inexpensive materials to mold some small optics for LEDs. The LEDs in question are typically surface mount with a wide viewing angle (light dispersion) in the 120+ degree range. I would like to mount a small lens over the top that would decrease the viewing angle and focus the beam (either a circle or oval). The final angle doesn't have to be exact, but repeatable to within a handful of degrees... I figure such a small item will have little shrinkage (and therefore angle change). Prototypes and very small production runs will be made using rubber molds. Optical clarity of the material should be roughly on scale with that for your typical LED.

I'm also wondering what glues exist that would match the two lenses up, optically speaking. I know optical glues exist that minimize the index of refraction changes between items such as glass-air-glass boundaries, I just don't know what they're called. Brand names would be appreciated.

Thanks!


Dan - Owner

http://www.Hi-TecDesigns.com

 

[patprimmer]

Poly Methyl Methacrylate (PMMA or acrylic) is generally considered to be the material of choice for lenses due to it's extreme clarity (in good quality pure grades) high refractive index (allows for thinner lenses) and good scratch resistance. It can be obtained in injection moulding and casting grades.

Trade names include Oraglass, Plexiglas, Perspex, Shinkolite and many others I cannot recall off the top of my head. A google search will find them for you.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Demon3]

You can read a huge amount about LEDs at

http://www.ledmuseum.org

perhaps there's something there to help you.

 

[MacGyverS2000]

Thanks, pat, that points me in the right direction. I'll try to find something in a pourable format for use in rubber molds. A sizeable mold (1 foot square) would easily make 200+ lenses, so I could always have a fresh batch on hand within a few hours.


Demon, that site has been around for years... although it has a lot of great historical info on it, I'm usually well beyond any technical info it contains.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Demon3]

Yes, I know the site has been around for years, it lists technical details of many LEDs so I thought there was a chance that he might have something on what the optical part is made of although he does normally focus on the light aspects instead.