Reconstructing unknown wavefronts by use of diffraction-intensity pattern subtraction.

We propose an easy method for unknown wavefront reconstruction by a typical Fourier transform system based on an amplitude-only spatial light modulator (SLM). The Fourier transform of the diffraction intensity pattern on the backfocal plane is the autocorrelation of the wavefront-transmitted SLM. Two intensity patterns were recorded when we set the transmittance of one corner pixel on the SLM as 0 and 1, separately, under the condition that the transmittances of the other pixels equal 1. The complex amplitude of the wavefront-transmitted SLM can be extracted from the Fourier transform of the diffraction intensity pattern subtraction without complicated calculations. The simulation results certifying our theories are also given. Our method provides us with an easy way for detecting the wavefront with high speed and high quality in real time without the reference wave.