
Polynomial surface
The polynomial surface is a surface whose sag is given by a general polynomial in the transverse coordinates x and y, expressed in the local surface coordinates:

The polynomial coefficients are entered in the parameters section of the surface data editor. The names of the coefficients are, e.g., x0y2 for the coefficient of y2 and x3y1 for the coefficient of x3y. In addition to the coefficients, there are four additional parameters: xMin, xMax, yMin, and yMax. These determine the extent of the rectangular area in the x-y plane on which the polynomial is defined.
In addition to entering the polynomial coefficients one at a time into the parameter list, Polynomial coefficients may be imported en masse using the parameter import mechanism. This requires the coefficients in a block of text, e.g.,
x0y2 1.445e-3 x0y3 -2.3e-5 x2y0 0.0032
Export of polynomial coefficients is also possible by the same mechanism.
The polynomial surface may not yield correct paraxial analysis if the linear terms are not zero. Furthermore, Seidel computations in the presence of polynomial surfaces are not yet defined.