The usefulness of a concentric lens in convergent space, with the centers of curvature of the surfaces coincident with the focus of the axial bundle, seems to have been generally overlooked. In this position the lens has no effect on the Gaussian optics, nor on any of the primary aberrations with the exception of the tangential field curvature. The sagittal field curvature is unaffected. The author has first used this device to effect an improvement in the performance of the Petzval projection lens. Another example is described.
SEYMOUR ROSIN, "Concentric Lens," J. Opt. Soc. Am. 49, 862-862 (1959)