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. 2010 May 5;18(10):10510–10523. doi: 10.1364/OE.18.010510

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©2010 Optical Society of America

This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License, which permits download and redistribution, provided that the original work is properly cited. This license restricts the article from being modified or used commercially.

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Fig. 4 — (Top Row) shows raw lensfree fluorescent images of different pairs of 10 µm diameter particles imaged using the set-up of Fig. 1. As the particles get closer to each other, their signatures in the raw lensfree image become indistinguishable to the bare eye. The inset images in the top row (bottom right corner of each image) illustrate transmission microscope images of the same particles from which the center-to-center distance (g) in each case is calculated only for comparison purposes. (Middle Row) illustrates the results of the compressive decoding process for each lensfree image of the top row. g_CS refers to the center-to-center distance of the resolved fluorescent particles in each image, where CS denotes “compressive sampling”. Even for g = 10µm case (far right column), we can clearly resolve the fluorescent particles from each other with g_CS = 9µm. The pixel size in the decoded image is 3µm, whereas the raw lensfree image has been sampled with a pixel size of W = 9µm at the detector array, i.e., N = 9M. The reason that the reconstructed points for g_CS = 9µm case do not touch each other (unlike the microscope image shown in the inset) is that the incoherent point-spread function of the system has been estimated using 10µm diameter fluorescent particles. Refer to Figs. 5, 6 for imaging of 2µm diameter fluorescent particles. The computation times of these decoded images vary between 0.1 min to 0.5 min on an Intel Centrino Duo Core, 1GHz PC. (Bottom Row) illustrates the deconvolution results of the Lucy-Richardson algorithm for the same set of lensfree images shown in the top row. g_LR refers to the center-to-center distance of the resolved fluorescent particles in each image, where LR denotes “Lucy-Richardson”. The number of iterations [19] in these deconvolution results ranged between 200 and 400, matching with the overall computation time of the CS results for each image. These results indicate that the LR algorithm can resolve particles with g~18 µm, whereas the CS decoder can clearly resolve particles with g~10 µm.