Coprime frequency modulation on light field for correlation imaging

Correlation imaging experiments correlate the outputs from two photodetectors. The image can be obtained by calculating the correlation function between results of two detectors. To reconstruct image of the object, many frames of different speckles are required. Therefore, the speed of correlation imaging is strongly limited by the speed of modulation of the light field. Usually, we use Spatial Light Modulator (SLM) to load different random phase at different positions of a plane-wave light field. The refresh rate of the speckle fields is thus limited by the surface refresh rate of SLM. However, the response speed of each pixel when we control it independently is far greater than the refresh rate of the whole surface. Based on this fact, we propose to modulate each pixel independently with different sinusoidal signals, in order to improve the refresh rate of speckle field. To generate randomly fluctuations, the frequencies of different modulation signals are selected to be coprime. At the same time, we can know in advance the intensity distribution of the speckle field in every frame, since we know the phase of each pixel when every pulse light modulated by the SLM.