The present invention relates to a phase mask for holographic data storage, and to a method and an apparatus for reading from and/or writing to holographic storage media using such a phase mask.According to the invention, the phase mask has a plurality of phase cells, whose size is equal to an integer multiple of the size of the pixels of a spatial light modulator of the apparatus. The phase cells have a phase variation on sub-cell scale, which is inverse for essentially half the number of phase cells.