Fig. 8
a Optical microscope images for the fabricated 3 × 3 microlens array spacing 8 μm apart when d = 8 μm and the measured optical patterns (A–A) under (a1) the single wavelength of λ = 532 nm and (a2) the broadband illumination. Identical foci from individual microlenses are observed. b Experimental results (B–B) for the 3 × 3 microlens array spacing 4 μm under (b1) the single wavelength of λ = 532 nm and (b2) the broadband illumination. The coupling effect between two adjacent microlenses, as denoted by the regions C, D, and E, can be observed