Irregular

The irregular surface is a Standard surface shape (plane, spherical, or conic) that has additional aspheric deviations in terms of decenter, tilt, spherical aberration, astigmatism, and coma. This surface type is primarily used by the tolerancing algorithm to model irregularities in a standard shape surface. The surface sag is given by:

where

and r_max is the maximum radial aperture of the lens, defined by the clear semi-diameter or semi-diameter value for the surface. The coefficients Z_s, Z_a, and Z_c represent the amount of spherical aberration, astigmatism, and coma, respectively, in lens units at the maximum radial aperture. The astigmatism and coma are oriented along a line that makes an angle θ in degrees with respect to the y axis.

The x and y coordinates of the previous equations are in a decentered and tilted coordinate system defined by the decenter x, decenter y, tilt about x, and tilt about y values. The decenters are in lens units, and the tilt is in degrees. The tilt and decenter values work exactly like the coordinate break surface defined in this section, however, the tilts and decenters are undone after the ray is traced to the surface. Ray tracing is done according to this algorithm:

The surface is decentered, tilted about x, then about y.

The ray is traced to the surface.

The surface is untilted about y, untilted about x, then undecentered.

The irregular surface uses the first seven parameters to define the decenter, tilt, and Z coefficients, and the eighth parameter to define the angle. All the coefficients are measured in lens units, except the tilt angles which are in degrees.

PARAMETER DEFINITIONS FOR IRREGULAR SURFACES

Parameter #	Definition
1	Decenter X
2	Decenter Y
3	Tilt About X
4	Tilt About Y
5	Zs
6	Za
7	Zc
8	θ

Next:

• Jones Matrix (sequential surfaces, lens data editor)