Alternate Odd

There are two solutions to the ray-surface intercept equations used in tracing a ray to the next optical surface, if that surface is of the form of the standard or even aspheric surface types. OpticStudio selects the correct solution in the vast majority of cases. However, in certain systems, so-called "strange" rays are actually intended to intersect the next surface at the other, "alternate" solution. Strange rays are most likely to occur after a grazing incidence reflection in which the ray is still traveling in the same direction (the Z component of the ray vector does not change sign). The alternate odd surface model is identical to the odd asphere surface model, except the alternate solution is used. OpticStudio may not be able to correctly compute the optical path difference when the alternate odd surface is being used.

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• Atmospheric