The differential absorption lidar (DIAL) at the Institut für Meteorologie und Klimaforschung has been upgraded for precise ozone and aerosol studies in the entire troposphere and the lower stratosphere. Its excellent technical performance offers the opportunity to apply improved data processing. The existing inversion algorithm is extended to derive the optical coefficients from the backscatter profiles for three wavelengths. Correlating the correction terms of the DIAL equation and the ozone concentration yields the wavelength dependence of the backscatter and extinction coefficients of the aerosol. Under some conditions, in particular if homogeneous layers are present, the backscatter-to-extinction ratio and the reference value can also be retrieved. We find the solutions by applying evolutionary strategies. From the optical coefficients obtained in this way the ozone concentration can be calculated with substantially reduced error.