A Search for Apochromatic Lens Systems.
AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS
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One hundred and sixteen separate crown glass types were examined in pairs with numerical models so that apochromatic corrections could be evaluated. In this study all lenses were corrected for the C and F lines, leaving the third wavelength as a parameter of the search for good color correction. A number of glass pairs yielding good apochromatic corrections over the C, F, and lambda wavelength range are tabulated. By the addition of a third type of crown glass to one of the discovered aprochromatic doublets, satisfactory color correction may be obtained over an even wider wavelength range. This method of the extension of an apochromatic pair of lenses into an apochromatic triplet system is accomplished with a very low power third element, and this low power element may be used to correct spherical aberration. One such triplet is evaluated in some detail. Author