  Herein is presented an optical diffraction tomography (ODT) technique for
measuring 3-D refractive index (RI) maps of optical plastic lenses. A
Mach-Zehnder interferometer was used to measure multiple complex optical fields
of a plastic lens immersed in RI matching oil, at various rotational
orientations. From this, ODT was used to reconstruct a 3-D RI distribution of
the plastic lens with unprecedented RI sensitivity (dn = 4.21 x 10^-5) and high
resolution (12.8 um). As a demonstration, 3-D RI distributions of a
2-mm-diameter borosilicate sphere and a 5-mm-diameter plastic lens
