The use of a strong positive lens made from a low dispersion glass like crown glass coupled with a weaker high dispersion glass like flint glass can correct the chromatic aberration for two colors, e.g., red and blue.
Such doublets are often cemented together (called achromat doublets) and may be used in compound lenses such as the orthoscopic doublet.
Such doublets are often cemented together (called achromat doublets) and may be used in compound lenses such as the orthoscopic doublet.