Gradient 7
This surface has the same shape as the Standard surface, with media whose index of refraction is described by
Where
The coordinates x, y, and z are the usual coordinates measured with respect to the vertex tangent plane, and R is the radius of the isoindex contours measured at the vertex. The isoindex contours are spherical shells centered about the point z = R. The starting index, n0 , is measured at the vertex of the surface, not at the center of the isoindex contours. There are five parameters required: the maximum step size, Δt , the base index, n0 , R, α, and β . Note that α and β have units.
The isoindex contour radius R may be specified independently from the front or rear radius of curvature of the lens. However, if R is set to be zero, then OpticStudio assumes the isoindex radius and the front radius of curvature are equal.
The maximum step size Δt determines the trade-off between ray tracing speed and accuracy. For details see "Discussion on maximum step size for GRIN surfaces". Also see "Restrictions on surfaces following GRIN surfaces".
PARAMETER DEFINITIONS FOR GRADIENT 7 SURFACES
| Parameter # | Definition |
| 1 | Δt |
| 2 | n0 |
| 3 | R |
| 4 | α |
| 5 | β |
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