We report on the design optimization of a reflective antiferroelectric liquid crystal (AFLC) display in the in-plane optical geometry within the framework of the 2 x 2 Jones matrix formalism. For obtaining good achromaticity and high brightness in the reflective configuration, cell parameters of the AFLC layer are optimized in the geometry such that the average optic axis of the AFLC layer lies on the plane parallel to both substrates.