Diffraction (was: IR HAZARDS

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On  1 Feb 99 at 21:15, George L Smyth wrote:

> David Lee wrote:
> > 
> > Perhaps I don't interperate this excerpt from the IR FAQ correctly?
> > 
> > >From http://www2.ari.net/glsmyth/articles/ir_faq.htm
> > --------------------------
> > Another note: don't stop down too far! Diffraction is twice as bad
> > with long IR waves as it is with visible light! Stopping down to
> > minimum aperture is a NO NO!
> 
> Your interpretation is correct - I don't believe that the FAQ is, however.  As
> the waves are longer, diffraction should be lessened.

Nope, it gets worse, linear to wavelength, 800nm is twice as bad as 
400nm. Whether it exceeds other optical errors (some of which 
increase with smaller aperture, but some also decrease) is a quite 
fuzzy area of optical engineering, but the rule that diffraction 
increases with wavelength is hard science.

Guenter Spitzing, are you reading this?
 
 

--                 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]
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