The half-intensity width (HIW) (or more precisely the Full-width at half-maximum (FWHM)) of a curved function is the distance between the points where the intensity is half of the maximum one.


The HIW of a Point Spread Function is a good estimation of the device Spatial Resolution.

There is a FWHM Estimator available in the PSF distiller option from Huygens version 4.5 onwards. If the PSF distiller is part of your Huygens Professional license, you can also use the FWHM Estimator from the Analysis menu.