## What is/are Stigmatic Singlet?

Stigmatic Singlet - We present the exact equations to design a stigmatic singlet that meets the Herschel’s condition.^{[1]}We present the exact equations for designing a stigmatic singlet lens that meets Abbe’s sine condition for each ray.

^{[2]}We present a study of the diffraction pattern according to Richards-Wolf for an aplanatic and stigmatic singlet based on an exact analytical equation.

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