How do you measure the Numerical Aperture (NA) from the experimental PSF ?
It is more like estimating... <br>
Just look at the angle of the blur-cone fanning out from the bead along the optical axis (Z). The largest angle is the aperture, whose half (α) you need to use in the Numerical Aperture definition. Usually it can be easily seen in XZ slicing mode. A 1.3 NA oil lens should show α = 60 degrees with the optical axis, making the total cone angle 120 degrees. Often it is less!!! <br>
It is a sure way to spot optical or calibration problems. The shortcoming of this method is that you can't discriminate directly between errors in the sampling calibration or the effective NA. However, if there is much asymmetry than there is much Spherical Aberration for sure (see Mismatch Distorts Psf). Assuming the lens is good, this must be caused by a Refractive Index Mismatch. In turn that will lead to a reduction in effective NA. So in these cases a refractive index mismatch is at least one of the factors causing the problem.
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Keywords: NA numerical aperture experimental psf blur cone<br>
Categories: Faq Deconvolution, Faq Microscopy, Huygens Faq, Imported Faqs<br>
Platforms: Irix Linux Mac<br>
Related products: Hu Ess Hu Pro<br>
