A new method for the synthesis of broad band semitransparent dielectric reflectors with high reflectance based on the use of two materials was developed. Its main feature is that the starting design consists of a number of quarter-wave stacks with the same even number of layers and that the wavelengths for these stacks are quarter-waves are spaced uniformly on a logarithmic scale. After the first optimization the stacks are split into smaller identical fragments and a second optimization, in a different spectral region, takes place. The reflectors obtained in this way have very flat characteristics in a broad spectral region. The calculations were performed for the combination Sb 2O 3/MgF 2.