Wavefront modulation with spatial light modulator for Fourier ptychographic microscopy

Abstract

Fourier ptychographic microscopy (FPM) is a recently developed computational imaging technology, which can bypass the limitation of optical-spatial-bandwidth product to achieve imaging with both high resolution and wide field-of-view. Original FPM setup is limited to image thin samples with angle-varied illuminations. A diffuser scanning FPM method, which scans a diffuser with unknown profile between the object and objective lens to modulate the complex exit wavefront of the object, is implemented to address this 3D refocusing problem. However, since the profile of the diffuser is unknown, the number of images required for method to converge is large. A mechanical translation stage is also required, which may introduce the systematic error of the position. In this paper, we propose a new FPM method with wavefront modulation imposed by spatial light modulator (SLM). The SLM is placed between the object and the objective lens to produce specific pattern profile, which is used to modulate the complex exit wavefront of the object. Fourier ptychographic phase retrieval process is employed to recovery the complex exit wavefront of the object. With the use of SLM, it is unnecessary to employ 2D motorized translation stage to move the imposed pattern profile so that the error of translation stage is eliminated. Moreover, since the imposed pattern profile is known, the number of images required for the algorithm to converge is reduced. Simulation and experiment are performed to validate the effectiveness of our proposed method. Compared with the method, which utilizes unknown diffuser, our method can achieve a more accurate reconstruction result with a faster data acquisition and higher convergence speed.