Determining blur size with optical aberrations present
- From: Russ <mcelhane@xxxxxxxxxx>
- Date: Tue, 27 May 2008 10:42:40 -0700 (PDT)
I need to determine the "blur size" for an optical system with fairly
large aberrations. I have an optical system design that produces a
magnified image of the end of a multimode laser-emitting fiber. This
design has a lot of spherical aberration which is going to blur the
image and I need to determine what diameter this blur is for various
focus settings. I have only have a very, very old version of ZEEMAX
and it gives the RMS and geometric spot diameter for one point in the
field. What I need is a design program (which my company can't
afford) that gives the RMS and geometric spot diameter for the entire
image field. Since I don't have that, what is the best way to use the
info I have to determine the RMS spot diameter of the entire image?
The conservative approach is to take the geometric radius of the image
(as defined by diffraction-limited optics) and add the radial RMS of
the spot defined by a spot diagram at a single point at edge of the
field. The blur diameter of the aberrated image would be twice the
combined radii.
However, I think that this may be too conservative. Alternatively, I
could RSS the geometric radius of the image with the radial RMS of the
blur (from a single point in the field). However, I'm not sure that
this a correct approach either, since the geometric image is a top-hat
function and the aberration-induced blur is more gaussian like. - It
would be like RSSing apples and oranges.
Other than writing a program to convolute the aberrated image of the
point source with a top-hat function, is there any other guidance or
"rule-of-thumb" that someone out there can provide?
Thanks
.
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