Diffractive multifocal lenses are usually discussed in terms of geometric zone
profiles imparted a surface of a refractive lens. Consequently, the zeroth order diffractive
power is usually called the "refractive power" of the diffractive lens. By contrast, we
focuss on the refractive power or refractive power profile of the zones of a diffractive
lens and calculate the path length error of any of the zones in a given defocus position on
the lens axis. From this the phase angle of the resulting amplitudes can be calculated.
Analytical expressions for the positions of the diffractive powers as a function of (average)
zone powers are derived as well as analytical expressions for the intensities in such
positions. Also, general restrictions on usable zone power profiles are derived.