From: "Martti Koskimo" 
To: 
Reply-To: "Martti Koskimo" 


In most cases the system is limited by diffraction if all rays are inside
the airy disk.

If most of the 'rays' fall on the edge and not in the middle of the
diffraction ring the system can be worse than 1/4 Wave limit. If most of
the rays are in the center of the disk, some rays can be outside the ring
and still the system is probably Diffraction limited.

In Optical Design optimization if only rays are used we get a system were
the rays concentrate to the smallest possible spot.

If Wave front aberrations are used the spot diagram concentrates at the
middle but some rays typically have much wider separation. Wave front
optimized spots look 'uglier' but the system is still 'better'.

Ray optics by no means lose validity if ray aberrations are small. The
smaller the 'spot diagram' the better the system, diffraction limited or
not diffraction limited.

In those cases when we are not sure if spot diagram is good enough
presentation of the system it is not difficult to calculate from mirrors
test data the wave front aberration and other wave front based criteria for
optical goodness. Most of us calculate the wave front aberration by
default.



Martti Koskimo




----- Original Message -----
From: "scottythefiddler" 
To: "Mark Holm" ; 
Sent: Thursday, April 10, 2003 4:46 PM Subject: Re: ATM How Good Does a
Diagonal Need to Be?


>
> Question:  If a mirror is figured  with sufficient accuracy that geometric
> optics would predict all light would be reflected to fall within the
radius
> of the airy disk,  would the optical quality of the mirror be limited only
> by diffraction.  (Omitting atmospheric effects, collimation effects,
thermal
> effects, etc.)
>
> Thanks,
> Scott Donaldson
>
> ----- Original Message -----
> From: "Mark Holm" 
> To: 
> Sent: Wednesday, April 09, 2003 10:50 PM
> Subject: Re: ATM How Good Does a Diagonal Need to Be?
>
>
> >
> > >
> > > I thought at this level it was about phase interference, not angles.
> > > (I.e wave nature of light, not particle.)
> > >
> > >
> >
> >
> > Since I have been reading Feynman on quantum electrodynamics, I'll chip
in
> a bit
> > here.  According to QED: what matters is travel time; light is particles
> not
> > waves; and what you get out of the travel time calculation is a
> probability
> > function.  The only thing you can calculate is the probability that a
> photon
> > will get from point A to point B.
>
>
>
>

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