Improving Cellphone Microscopy Imaging with Contact Ball Lenses

It is shown that the resolution of cellphone-based microscopy can be improved with the use of millimeter-scale ball lenses with index n=1.85 placed in contact with fluorescent (FL) objects represented by dye-doped microspheres. Using the virtual imaging through such ball lenses, the resolution improvement from ~35 µm to ~2 µm is achieved over a field-of-view of about 0.1 × 0.1 mm2. Further improvement of resolution and field-of-view can be expected with optimization of parameters of the contact ball lenses that can lead to wide applications of the proposed technology in mobile biomedical imaging.