Noise gratings formed during the multiple exposure schedule in photorefractive media

We consider the noise gratings formed while writing angularly multiplexed holograms in photofractive media using a multiple exposure schedule. During the recording process of the pth exposure, the writing beams generate new gratings while erasing the previously stored gratings. In addition, diffraction occurs due to the readout of the previously stored gratings. In addition, diffraction occurs due to the readout of the previously stored gratings, even if they are Bragg-mismatched for the writing beams. The additional diffracted beams will interact with the writing beams and form noise gratings. We calculate the amplitude of noise gratings and discuss their effects on the signal-to-noise ratio.