Influence of imperfections of an optical system on the probability of holographic memory failure

The output signals from a memory corresponding to the binary digits 1 and 0 may be distorted not only by the presence of noise due to the granularity of a photographic film, but also because of the data distribution in the vicinity of a certain bit due to imperfections of the optical data processing. Calculations are made of the distortion of data because of imperfections of the optical system, such as the diffraction due to the limited size of a hologram, damage to a hologram, aberrations of the objectives, inaccurate setting of a hologram, and shift of the reconstructed image on a sensor (detector) array. The situation with the least favorable signals at the output of a memory device is identified. An allowance is made for the granularity of a photographic film in the case of such least favorable signals and the upper limit of the probability of memory failure is determined. Calculations indicate that this upper limit is influenced decisively by the damage to a hologram and by a shift of the reconstructed image in the sensor array plane, whereas reduction in the hologram size (i.e., an increase in the recorded data density) has little influence.