Here, an optical fibre with 3D printed doublet Fresnel lenses is inserted into a water droplet to image the beam profile by an inverse microscope.
A white light laser passed through the objective is used to align the fibre with respect to the objective and causes the blue colour of the lenses in the refracted image on the surface of the droplet.
[Asa Asadollahbaik, 4th Physics Institute, University of Stuttgart.]
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