Re: Köhler illumination question...

Einen schönen guten Morgen!



Excellent point! This could explain some new designs that are recently sold.
One example is the fly-eye optics design by Nikon (see Eclipse 80i), which
are used to ensure even illumination.



I just looked at the Leitz Ortholux lens in the illuminator, and although it
looks like a "frosted" lens at first sight, it is possible that also Leitz
created the mat surface using a similar process (?). How big are these
bowl-like concave hollows in the lens-surface?



Nette Grüsse aus Kalifornien,



Gregor



....
> reading your qestions to Andy Resnick and earlier contributions in
> this thread, it seems to me, the term "frosted" does not take into
> account properly, that the first lens-surface of some Zeiss
> lamp-collectors ist not ground. Its mat surface is achieved by
> hydrofluoric acid, which leaves thousands of little bowl-like concave
> hollows in the lens-surface. They are of different diameters, but all
> of the same focus-width - tiny concave lenses on the surface of a
> concave lens.
>
> The result is, that light-rays are not being scattered in all
> directions, as would be the result of a simple ground glass, but the
> light beams entering the first collector lens, are just "widened" and
> defocussed, changing the image of the lamp filament into a homogeneous
> image, mixed together out of thousands of little lenses. This design
> does not fully destroy the definition of the field diaphragm.
>
> Frosted in that special way the lighting force is reduced about
> 20-40%; that is not much, compared with reduction of 60-80% through a
> normal ground glass.
>
....


.

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