http://confocal-microscopy-list.275.s1.nabble.com/Nyquist-sampling-advice-for-a-short-talk-tp7591495p7591500.html
resolution. If you consider the classic example of discerning two separate
points, you have a pair of Gaussian curves sitting next to each other. As
they approach, a valley forms between the curves. The 'floor' of this
valley rises as the two curves begin to merge. Your ability to tell the two
between the two Gaussians. If your image is over exposed, or has low
that valley and thus the two peaks start to appear as a single peak. Many
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> Well, the question was specifically about Nyquist, and, I gather, as an
> introduction of some sorts, not for advanced physics students.
>
> What I always stress when explaining sampling, is to first differentiate
> between the Abbe criterion, explained as the *physics-based theoretical
> limit* on resolution, and how we *detect *that resolution. You don't even
> need to explain Abbe very well, and the causes and the parts of the
> equation, as long as they understand that there exists something called the
> "Abbe criterion" that refers to the "best possible
> resolution physics allows".
> Then, I get into how to detect, or in sciencese, *sample*, what is
> allowable by physics.
>
> I have some slides (I think I got them originally from the
> wonderful lecture series by Paul Robinson from Purdue) showing the idea of
> sampling that Nyquist originated. (e.g. signal, sample, and if not enough
> sample, the recreated signal will be lacking thus "undersampled" etc).
>
> Once they understand the concept of sampling in general, it's now easy to
> show why pixel size in imaging is sampling and is important to determine
> the "Nyquist". (Pixel size for lateral and "slice number" for axial). For
> this I use a self-customized (I doubled the disk) version of the Zeiss
> "projected size of airy disk on ccd array" graphic showing an airy disk on
> four same size FoVs but with different pixel sizes. I show that when
> undersampled, even though the center of the disks of the two points of
> light are more than say 300nm from each other (so physics is not the
> limiting factor), you won't be able to detect it.
>
> I think that explaining the concept in this manner gives a very good
> intuitive understanding.
>
> I actually think it's very appropriate to mention point scanning systems,
> because only thus can you determine your pixel size. With
> camera-based systems, the max sampling is what it is - limited by the
> physical size of the chip pixels - you can't oversample even if you wanted
> to (though you can undersample by binning, of course.)
>
> Avi
> --
> Avi Jacob, Ph.D.
> The Kanbar Light Microscopy Unit
> The Goodman Faculty of Life Sciences
> Bar-Ilan University, Ramat-Gan 5290002, Israel
>
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