This type of holographic surface describes the interference pattern of two point sources, i.e. two spherical waves, which includes plane wavefronts as the limiting case.
The phase distribution can be shown for all user specified symmetric and asymmetric phase functions including the 2p phase steps.
A diffractive lens is mathematically equivalent to a thin refractive lens, provided the index of refraction goes to infinity. For practical cases a very high refractive index (n = 10000) is used. This model is commonly known as the "Sweatt" model.
Shown to the left is a F-q scan lens, which illustrates the use of the sweatt model for a diffractive lens.
|Diffractive Germanium Doublet.
A color corrected F/1.0 system for the 8-12mm wavelength range. The first surface is aspheric while the second surface bears a CGH, described by a symmetric phase function.