光學設計軟件zemax源碼：
This DLL models an nular aspheric
surface as described in:
"Annular surfaces in annular field systems"
By Jose M. Sasian
Opt. eng. 36 (12) P 3401-3401 December 1997
This surface is essentially an odd aspheric surface with an offset in the aspheric terms.
The sag is given by:
Z = (c*r*r) / (1+(1-((1+k)*c*c*r*r))^ 1/2 ) + a*(r-q)^2 + b*(r-q)^3 + c*(r-q)^4 + ...
Note the terms a, b, c, ... have units of length to the -1, -2, -3, ... power.
