Re: [ATM] Sling study

[Dale Eason <atmpob@yahoo.com>]

Trefoil has a magnitude and a direction.  You can see
that the rotation is not the same in most all the
trefoil images.

For a description of how Zernike Polynomials are used
to represent astig and trefoil see

http://wyant.optics.arizona.edu/zernikes/zernikes.htm

Astigmatism and trefoil each are made up of two
Zernike terms, one for X and one for Y.  The magnitude
of those two terms determine the angle of the
astigmatism and trefoil.  Try out different values in
the above simulation and see what happens.

In some reports you will see astigmatism and trefoil
as value and angle.  In my report I just listed the
value and displayed the contour map where you can see
the orientation.

One of the key points I was trying to make by
splitting the astig and trefoil images was to show how
some lateral support methods are more prone to one
type of distortion than others.  In particular the two
point support at 90 degrees does not create any
astigmatism but does create trefoil.  For my
particular test case the magnitude of the trefoil was
much less than the magnitude of the astig of the sling
and single point support. 


Dale Eason
--- Alexis Cousein <al@sgi.com> wrote:

> Arjan te Marvelde wrote:
> > Dale,
> > 
> > Why is it that the general deformation is the same
> for two pegs, one peg or
> > a sling? 
> 
> It's not. If you look closely, he's split off the
> trefoil and astigmatic
> components into different pictures. Obviously, if
> you're looking at
> the trefoil pictures, they all look like trefoil
> deformation...
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 



 
____________________________________________________________________________________
Do you Yahoo!?
Everyone is raving about the all-new Yahoo! Mail beta.
http://new.mail.yahoo.com
_______________________________________________
ATM mailing list http://www.atmlist.net/