Noise suppression for double-phase hologram by complementary averaging

Spatial light modulators (SLMs) are the most common used digital elements for electro-holographic display, which allow presenting the computer-generated holograms (CGHs) without photosensitive medium and interference for recording. Most of the available SLMs can only modulate either amplitude or phase, which leaves complex amplitude modulation as a challenging problem to be solved. Since the method of generating holograms based on the decomposition of a complex value into two phase values was proposed in 1970, the encoding for a complex field is realized. The double-phase holograms (DPHs) can synthesize the two phase values in to a single hologram after sampling. DPHs are thus able to recover the complex object field approximately but sacrifice the accuracy and intensity of high spatial frequency components. To reconstruct the complete and accurate complex field, a high quality complex modulating method is proposed. The proposed method utilizes the interference of two phase-only wave-fronts modulated by two SLMs respectively. The prospective complex field is formed after the coherent superposition and sufficient long-distance diffractive propagation. The complex modulation and reconstruction based on phase interference is equivalent to the capacity of the amplitude and phase information for the complex object wave-front. This method is also free of speckle noise brought out by random phase encoding and the twin images reconstructed by the amplitude only holograms.