How to compute the Nyquist rate for an image?
See Nyquist Rate and Nyquist Calculator.
The following formulas can be used to compute the Nquist rate:
Widefield microscope: <br>
Nyquist_lateral = lambda / ( 4 n sin(alpha)) <br>
Nyquist_axial = lambda / ( 4 n (1 - cos(alpha)))
with lambda the wavelength, n the refractive index of the <br>
medium (1.515 for immersion oil). Alpha is the half-aperture angle obtained with:
alpha = arcsin(NA/n) with NA the Numerical aperture.
Many calculators use the 'sin^-1' or 'asin' symbol for the arcsin function.
Assuming the excitation and emission wavelength are equal a confocal microscope *doubles* the bandwidth so *halves* the Nyquist sampling density.
Both Huygens Pro and Essential take the exact wavelength into account when computing the Nyquist rate. In case of multi photon excitation they also take the number of excitation photons into account. Both will color the background of X, Y, Z sampling density entry fields orange (moderate undersampling) or red (serious undersampling) when detecting undersampling.
In Huygens Pro you can look up the Nyquist rate for a particular image by selecting it and Edit->Nyquist rate.
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Keywords: Nyquist bandwidth<br>
Categories: Faq Deconvolution, Faq Microscopy, Huygens Faq, Imported Faqs<br>
Platforms: Irix Linux Windows Mac AIX<br>
Related products: Hu Ess Hu Pro Hu Script<br>
