Application of pupil spherical aberration in tuning zoom lens design

Fine tuning the performance of a zoom lens, at the final design stage, is still a challenging problem for lens designers. This is mainly due to the difficulties in setting up a reliable criterion as the discriminator. In this paper, following some previous studies on pupil spherical aberration (PSA, denoted as SVI) (Wynne 1952 Proc. Phys. Soc. 65 429–37, Kidger 1996 Proc. SPIE 2774 722–7) where the conditions for invariance of Seidel aberration during conjugate changes were given, a simple method was derived to analyze the steady zone of a zoom lens variator. A previously designed zoom system (Laikin 2006 Lens Design 3rd edn (Boca Raton, FL: CRC Press) pp 393–5) was selected as an example and it was shown how its image quality can be balanced and improved computationally. The potential application of our method was also addressed in the conclusion. (paper)