Optical system design of fully symmetrical Fourier transform lens

The design requirements of the Fourier transform optical system required for synthetic aperture radar(SAR) are analyzed and the specific optical parameters are determined. The design of the Fourier lens adopts a fully symmetrical structure to avoid simultaneous optimization of the forward and reverse directions of the optical path and can complete the correction of the conjugate positional aberrations of the two pairs of object images. A Fourier lens composed of four spherical mirrors was designed and reached the diffraction limit. To verify that the optical lens can realize the Fourier transform, a 4f optical system was built in the laboratory using the lens. First, the 4f system built by the optical element was demonstrated to be able to process the signal by demodulating a one-dimensional linear frequency modulation(LFM) signal. Then, the echo signal of the SAR point target is demodulated, Fourier transform is realized by the lens, and the imaging of SAR single point target signal is completed, which plays a role in the practical application of the fully symmetrical Fourier optical lens.