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Re: [ATM] Lens Wedge
Hi John and Bob,
Yes, lateral chromatic aberration is the problem, but I'd like to
quantify it. How much is 'too much' to achieve 90% Strehl Ratio (at all
wavelengths), say? Or what is the lateral chromatic aberration due to
wedge as a percentage of lateral spherical aberration?
Smith (Modern Optical Engineering) mentions the difficulty in achieving
close thickness tolerances, and mentions ± .004 inches as a reasonable
tolerance (absolute value given only - no dependence on d or fl.)
Nothing in Kingslake. But I found a mention in Walker (Optical
Engineering Fundamentals), which gives an Edge Thickness Tolerance (ETD)
of .025 mm in a 50mm (400 mm EFL) lens. I would assume that's scalable
up for larger lenses. But he doesn't give any analytical proof.
I also queried Roger Ceragioli, but he wasn't aware of any calculated
tolerances, either (he recommends .001 inch tolerance).
If nothing is out there in the literature, I guess I'll have to sharpen
my pencil! Still waiting for suggestions, though.
James
John Sherman wrote:
>
> I haven't seen an answer to your question, and I don't have it. But, I think the answer is the third problem, chromatic aberration. A lens with wedge is called a prism. I suppose if you're making an achromat, a bit of wedge in one lens can be compensated to some extent by wedge in the other lens.
>
> Have fun,
>
> John
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