Abstract:The multi-intensity phase retrieval methods obtain different coded diffraction patterns by changing the physical parameters in the optical imaging system, which can achieve the best convergence of phase and high-precision reconstruction without additional prior knowledge. However, the existing multi-intensity phase retrieval methods often need to constantly change the physical structure of the imaging system and accurately move or adjust the spatial position of some optical elements in the process of obtaining different measurements. The repeated alignment and calibration significantly increase the workload, resulting in more complex imaging structure. To solve the above problems, a real-time acquisition method of Fresnel field coded diffraction pattern based on high-speed phase modulation was proposed in this paper. In the method, two pure phase spatial light modulators: electrically tunable lens (ETL) and pure phase silicon-based liquid crystal (PLCoS) were mainly used to perform the fast dynamic phase modulation. The phase was transmitted to the recording plane through free space, and the intensity information was obtained by the detector without using a lens or changing the physical structure of the imaging system. The WF algorithm was used to simultaneously reconstruct the amplitude and phase of the light field from multiple coded diffraction patterns. In the paper, the effectiveness and robustness of the proposed method were verified by the contrast experiments of farfield (FF) and Fresnel field (FrF) under different iteration times, different mask numbers, different noise levels and different algorithms. Compared with the traditional multi-intensity phase retrieval methods, the proposed imaging system is more compact and simple. It avoids the workload of repeated alignment and calibration, and has important application potentials. Especially, the electrically tunable lens (ETL) modulation scheme can be applied to high-speed recording of high-resolution scenes.