Fourier ptychography transmission color imaging in the far-field based on wavelength multiplexing

In the far-field imaging scenario, the most significant factor restricting the imaging resolution is the finite size of the aperture, which determines the diffraction limit of the system. Fourier ptychography (FP) technique provides both a wide field of view and high resolution (HR) for imaging. Still, the efficiency is limited by the time-consuming process of images acquisition. Combined with information multiplexing technique, the imaging efficiency of muti-wavelength FP is effectively improved. However, since the same dataset of intensity measurement is used to recover the HR image at each wavelength, color reproduction problems will occur in the reconstructed image. In this paper, three additional images, captured in the R/G/B channels separately, are used as a reference to perform color calibration during the reconstruction process. What's more, in the subsequent reconstruction process, we use the simulated annealing algorithm and adaptive step-size strategy to correct aberrations. By updating the spectrum function and pupil function of the current sub-aperture, the HR spectrum information of the measured target is obtained. Our approach is verified by simulations where the amplitude RMSE values of R/G/B channels are less than 0.071, 0.076, and 0.064 respectively. The resolution of objects is improved approximately fivefold, which is consistent with the theoretical reconstruction multiple.