Angle compensation of the reference beam in a retrieving process of the holographic data storage system

Holographic data storage system is one of a strong candidate of the next generation high capacity data storage system with a high storage density and a fast data transfer rate. The holographic data storage system uses two beams in a recording process and only a reference beam is used for retrieving stored data. With the angle multiplexing when the angle of the reference beam is deviated from its correct point, the diffraction efficiency of the corresponding data page is reduced and SNR is decreased. Therefore it is necessary to compensate the angle of the reference beam to reconstruct a good data page. To compensate the angle error, the angle of the reference beam is changed precisely within a specific range and stopped at the angle with the highest diffraction efficiency. By this method, in a retrieving process if there is a difference between the real angle of the reference beam and its correct angle, the error can be compensated and the best data page can be obtained.