Does applying an AR coat to a lens material change the Abbe value?
Does applying an AR coat to a lens material change the Abbe value?
Nope! The substrate remains the same and AR does absolutely nothing to lessen the effects of a poor ABBE.
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No. A/R only allows more light to pass through the lens, it does not effect the dispersion of the light by the material. If you think about it, it should actually make the dispersion MORE noticeable, since more light is passing through the lens, and thus being dispersed.....
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Hi edKENdanc, despite multiple (manufacturer) claims to the contrary, that AR coats would cause or even reduce additional color fringing (at least in some cases), it cannot override the basic of Snells law that the total change in "wave vector" or more simply "ray direction" from an incident (i) to a final medium (f) is always given by n_i times sin(angle_i) = n_f times sin(anglef_) or more generally that the "numerical aperture" n times sin(alpha) (n = local refractive index, alpha = "ray" angle to the surface normal) is always retained even in complex multi layer stacks. (You can change the intensity, though, which are the basics of AR coatings or even cause total internal reflection, which would interrupt the ray path (in case |sin(alpha)| would need to be > 1, because n_i/n_f is too high) A physicist would say, this is the law of "conservation of momentum"!Originally Posted by edKENdance
Nope, even if more light passes through (a meager few %), the relation of different colors (what I would call the only reasonable definition of dispersion) remains (almost) the same. Think about it:bbg:!
(ACTUALLY, because no AR is perfect over the whole spectral range and works differently well for varying wavelenghts/colors, there would be a very slight filter effect that modifies the transmitted spectrum, but in any reasonable design this is a weak effect and has nothing to do with any color fringing due to low Abbe - only to be correct - it would cause some overall very weak tint of the respective lens)
As someone once pushed into a 1.67 with Teflon, I can say AR cotes don't affect chromatic abberation. At all.
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Thanks for the advice
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