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In a distribution, full width at half maximum (FWHM) is the difference between the two values of the independent variable at which the dependent variable is equal to half of its maximum value. In other words, it is the width of a spectrum curve measured between those points on the y -axis which are half the maximum amplitude.
Plot of the centered Voigt profile for four cases. Each case has a full width at half-maximum of very nearly 3.6. The black and red profiles are the limiting cases of the Gaussian (γ =0) and the Lorentzian (σ =0) profiles respectively.
The half maximum of the central Airy disk (where () / = /) occurs at = …; the 1/e 2 point (where () / = /) occurs at = …, and the maximum of the first ring occurs at = …. The intensity I 0 {\displaystyle I_{0}} at the center of the diffraction pattern is related to the total power P 0 {\displaystyle P_{0}} incident on the aperture by [ 12 ]
In confocal laser-scanned microscopes, the full-width half-maximum (FWHM) of the point spread function is often used to avoid the difficulty of measuring the Airy disc. [1] This, combined with the rastered illumination pattern, results in better resolution, but it is still proportional to the Rayleigh-based formula given above.
In the peak width definition, the value of ΔM is the width of the peak measured at a specified fraction of the peak height, for example 0.5%, 5%, 10% or 50%. The latter is called the full width at half maximum (FWHM).
The diameter of the seeing disk is the full width at half maximum of its optical intensity. An exposure time of several tens of milliseconds can be considered long in this context. The Fried parameter describes the size of an imaginary telescope aperture for which the diffraction limited angular resolution is equal to the resolution limited by ...
In fiber-optic communication applications, the usual method of specifying spectral width is the full width at half maximum (FWHM). This is the same convention used in bandwidth, defined as the frequency range where power drops by less than half (at most −3 dB). The FWHM method may be difficult to apply when the spectrum has a complex shape.
The width of the beam is defined as the distance between the points of the measured curve that are 10% and 90% (or 20% and 80%) of the maximum value. If the baseline value is small or subtracted out, the knife-edge beam width always corresponds to 60%, in the case of 20/80, or 80%, in the case of 10/90, of the total beam power no matter what ...