Glenn Holliday wrote:

Rolo wrote:

Stephen Paul wrote:

The Fresnel rings

Is this Fresnel pattern the same thing as a diffraction ring pattern?
If yes, when and why did the terminology change, or is this a news
group dialectical preference not shared at major universities?

A Fresnel lens is different than a diffraction grating, and
has a different purpose.

What lens and grating? Nobody said anything about lenses and gratings?
Theatrical lighting? Hmmmmmm. I think you did not read
the words I printed out to ask a question. Maybe you need fresnel
Lens?



The lens is not made with one curvature
across the surface of the lens, but is made in concentric rings,
each ring with a slightly different curvature. The purpose is
to get a better focus with a light source that is not a point.
In theatrical lighting, the effect is to get a more uniform
illumination of the area lit by a light that has a Fresnel lens.

--
Glenn Holliday