A method for uniformizing a Fourier spectrum is presented for optical holographic storage. The input pattern is modulated by an optimized phase mask, which can be designed by using amplitude-phase retrieval algorithms. The spectral amplitude distribution in the aperture of the recording medium is uniformized by the diffraction effect of the phase mask. Simulation results show that the uniformity is greatly improved. (C) 1998 Published by Elsevier Science B.V. All rights reserved.