Color Fourier ptychographic microscopy based on symmetrical illumination and wavelength multiplexing

Abstract

Fourier ptychographic microscopy (FPM), by using a LED array as its light source and each LED being lit up sequentially, can recover a high resolution (HR) and large field of view image from a sequence of low resolution (LR) images. It is difficult to obtain a perfect high resolution color image by a monochrome camera because of non-overlapping focal planes of different color channels resulting from the residual chromatic aberration of the microscopic objective. In this paper, a kind of method, based on symmetrical LED illumination and wavelength multiplexing, is applied in a FPM system to collect LR images and recover HR color images. Compared with single LED illumination, symmetrical illumination has higher defocus tolerance. It is proven by simulated and experimental results that higher-quality HR color images can be obtained based on wavelength multiplexing and symmetrical illumination by a monochrome camera when defocus or chromatic aberration exist. It is demonstrated that symmetrical illumination is helpful in chromatic aberration correction in color FPM imaging.