Re: ATM Anti reflection coatings and TDE (not related)

[Michael Lindner <mikel@att.net>]

"Ashish, Balaya (IE10)" wrote:
> 
> 1) How do anti-reflection coatings improve light transmission?
> I can't understand how reducing the reflection can
> improve the TRANSMISSION

Well, the light has to go somewhere, it can't just disappear. If it's no
longer being reflected, it gets transmitted.

> 2) TDE : How does it degrade the image?

For a perfect scope, each point on the focal plane is EXACTLY the same
distance from all parts of the incoming waveform, and the parts of the
wave from all parts of the mirror come together in the same phase and
reinforce each other. Any deviations in the height of the mirror
surface, and some parts are destructively interfering. Again, the light
doesn't disappear, it just appears where the wave does constructively
interfere (i.e. outside the airy disk).

--
Mike Lindner