If the eye is an infinite distance from the source, plane waves enter the pupil.
Now, I want to change the volume but keep a constant number of plane waves for this new calculation.
This means keeping the energy cutoff constant and not the number of plane waves.
So a solution on the edge can be written as a linear combination of plane waves.
Light in the very center of the transform pattern corresponds to a perfect, wide plane wave.
Observe that the first term equals the real form of the plane wave just discussed.
This represents a plane wave traveling in the z direction.
In the case of the single-moded plane wave, is a uniform distribution.
If this is done at the focal point of the "mirror" plane waves will be reflected back.
A sinusoidal plane wave is one special solution of these equations.