Edge Thickness

OpticStudio defines the edge thickness of a surface as:

Where Z _i is the sag of the surface, Z _i+1 is the sag of the next surface, and T _i is the axial thickness of the surface. The sag values are computed at the +y clear semi-diameter or semi-diameter of their respective surfaces; Note that edge thickness is computed for the +y radial aperture, which may be inadequate if the surface is not rotationally symmetric, or if surface apertures have been placed upon either of the surfaces.

Edge thickness solves use a slightly different definition of edge thickness. For edge thickness solves only, the sag of the i+1 surface is computed at the clear semi-diameter or semi-diameter of surface i. This method avoids a possible infinite loop in the calculation, since changing the thickness of surface i may alter the clear semi-diameter or semi-diameter of surface i+1, if the latter clear semi-diameter or semi-diameter is in "automatic" mode and the value is based upon ray tracing.

See "Thickness: Edge Thickness" and "Entering Semi-Diameter Data" for more information.