Petzval Lenses

This is a continuation from the previous tutorial - double-Gauss lenses.

In 1839, Petzval designed a new type of lens that comprises a front objective with an achromatic, airspaced doublet as the rear elements.

The Petzval lens has found great application in projectors and as a portrait lens. Both spherical aberration and coma can be well-corrected, but the lens configuration causes the Petzval sum to be undercorrected, which results in the field of view being limited by the astigmatism.

The Petzval field curves inward and may be corrected by including a field flattener lens in close proximity to the image plane.

A typical example of a Petzval lens is shown in Fig. 26.

The next tutorial introduces telephoto lenses.