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Fourier ptychography microscopy (FPM) is a computational imaging technique that enables high resolution and large FOV simultaneously. For FPM, multiplexed LED illumination can significantly improve the efficiency of image data acquisition at the cost of deteriorated quality in the reconstructed images. In this study, we aim to evaluate the imaging quality of multiplexed FPM with different illumination configurations. For this purpose, a prototype FPM microscope was developed, which was equipped with a 4×/0.1 NA objective lens. This prototype was used to test 1 LED conventional, 2 LED multiplexed, and 4 LED multiplexed FPM illumination configurations on a standard USAF 1951 resolution target and a cytology sample. Modulation transfer function (MTF) curves were generated from the reconstructed images to quantitatively compare the performance of different LED combinations. The results demonstrated that the resolution target image reconstructed using 1 LED illumination raw images can resolve up to 912.3 lp/mm, but it decreased to 812.7 lp/mm and 724.1 lp/mm when 2 LED and 4 LED illumination were adopted, respectively. The corresponding MTF curves indicate decreased contrast on most spatial frequencies when comparing reconstructed results between multiplexed (2/4 LED) and conventional illumination configurations. Accordingly, the quality of reconstructed clinical cytology sample images decreases as the number of LEDs per image increases. However, all of them have satisfactory quality for most clinical applications. This preliminary study provides useful information to facilitate the development of multiplexed illumination FPM imaging systems in the future.
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