Four-Color Achromats and Superchromats

Materials suitable for the construction of achromatic lenses corrected for four wavelengths are selected by the use of three graphs which are the three orthographic projections of a three-dimensional graph in P, Q, and V; where V=(nd−1)/(nF−nC), P=(nh−nC)/(nF−nC), and Q=(n1.014−nC)/(nF−nC). One set of three glasses, Schott PKS-1, F-1, and KzFS-4, has been selected, from which a four-color achromat has been designed. Analysis at 12 wavelengths shows this design to have negligible residual chromatic aberration. It is consequently a superchromat in accordance with Herzberger’s prediction.