Speckle noise reduction by random phase shifters.
Experimental results are given that show that a random phase shifter (RPS) is effective in reducing speckle noise caused by optical defects in coherent imaging systems, including holographic imaging systems. Here the RPS is composed of many tiny transparent blocks, each of which gives a definite phase shift such as O or pi to the transmitting light; and the distribution of the phase shift is two-dimensionally random. The optical defects are scattering centers such as scratches or dust on lenses or on the hologram medium in the case of holographic imaging systems.
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Matsumura