From: Sandy King (sanking@clemson.edu)
Date: 07/11/02-03:31:55 PM Z
Richard Knoppow wrote:
>
> There is a trade off between image brightness and uniformity of
>illumination for ground glass. The finer it is the more even the
>illumination but the dimmer the overall image. Coarse GG willbe bright in
>the center but have a serious hot spot in line with the lens.
Curious, I find just the opposite to be true. In my experience very
fine GG gives a brighter image but also a bright central spot,
whereas coarse GG gives a dimmer image but brightness is more uniform
across the entire area of the glass.
A fresnel will definitely even the illumination out to the corners,
but at the price of being able to focus on fine detail.
Sandy King
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