Re: Taylor-Merchant stereoscope lenses

[P3D John Bercovitz <bercov@xxxxxxxxxx>]

Jim wrote:
 
> They make spectacle lenses now out of polycarbonates &
> "high-index plastics" that I think have a higher refractive
> index than glass.  The chromatic abberation is pretty horrendous
> though.
 
Steve Owsley asked me about this off list and I looked it up.
Yeah, polycarbonate has about a 5% higher index than crown but I 
bet the Abbe number is the pits (for single lens use) as you say.
Not as good as some acrylics, though a much tougher material.  
Also, it's more expensive than acrylic.  May be tougher to mold, I 
don't know.  Not sure anyone would make a stereoscope lens out of 
it.  Well, with the higher index you could use a little less of it 
- that would save some money.
 
John B


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