
248 OPTICS FOR ENGINEERS
We now have three expressions that use the Fourier transform of the eld, Equation 8.49,
giving the result in terms of the eld in the Fraunhofer zone, Equation 8.52 giving it in terms
of angular distribution of the eld and Equation 8.50 giving the result in terms of spatial fre-
quencies. These three expressions all contain the same information. Thus, a numerical aperture
of NA blocks the plane waves that contribute to higher spatial frequencies. The relationships
among distances, x
1
, y
1
, in the aperture, spatial frequencies, f
x
, f
y
, and direction cosines, u, v,
are shown in Table 8.1. For example, if a camera has discrete ...