conic of surface

Standard


The most commonly used optical surface is a spherical surface. The sphere is centered on the current optical
axis, with the vertex located at the current axis position. ZEMAX treats planes as a special case of the sphere (a
sphere with infinite radius of curvature) and conics as a special case as well. The "sag" or z-coordinate of the
standard surface is given by


where is the curvature (the reciprocal of the radius), is the radial coordinate in lens units and is the conic
constant. The conic constant is less than -1 for hyperbolas, -1 for parabolas, between -1 and 0 for ellipses, 0 for
spheres, and greater than 0 for oblate ellipsoids. For more information on conic constants, see “REFERENCES
ON LENS DESIGN” on page 15. The standard surface does not use any of the parameter values.