Handbook of Biomedical Optics

Confocal Microscopy 527

Fourier optics theory states that the expression for the dif-

fracted light that has propagated from the pupil plane to the

front-focal plane of a lens reduces to the Fourier transform of

the irradiance distribution within the pupil (Goodman 2004).

Taking the Fourier transform of a circ function, which corre-

sponds to a plane wave apodized by a circular pupil, results in

an Airy function that matches the ideal result of Equation 25.5,

where the product of the pixel size and the number of pixels

corresponding to the radius of the Airy disk r

plane

is equivalent

to 0.61/NA in Equation 25.7. As a rst approximation, ...