Improvement to holographic digital data storage system with partially coherent light

摘要

In holographic memory the coherent interference recording is necessary. However, for a good image quality with speckle reduction in the imaging system, partial coherence or incoherence of the light source is desired. In this paper, the influence of coherence properties of the object and reference beams on the characteristics of the images stored and retrieved is discussed. During the recording process, using a vibrating uniform band-limited diffuser, a proper partial coherence is maintained and image detail down to the diffraction limit of the imaging system is preserved. In the readout process, serial pages near the Bragg condition are retrieved for the average processing. These methods are very effective to reduce the speckle noise and to achieve a low raw bit error rate. The coherence length required for holography is also discussed when we choose a compact low-cost laser source.