“…Depending on the requirements and circumstances, imaging can be done using a number of innovative mobile microscope solutions [ 16 ]. Add-on lenses of different kinds including ball-lenses, mobile camera lenses [ 21 , 64 , 65 ], and lens arrays have been used [ 66 , 67 , 68 ], as well as lens-free on-chip imaging devices [ 18 , 32 , 54 , 69 , 70 ]. Sophisticated optical and illumination systems and lens-free on-chip holographic imaging with image reconstruction can achieve high-resolution images, wide field of view, and enhanced contrast comparable to—or even surpassing—the image quality of conventional microscopes [ 16 , 54 , 69 , 71 , 72 , 73 ].…”