  Optical diffraction tomography (ODT) is an interferometric microscopy
technique capable of measuring 3-D refractive index (RI) distribution of
transparent samples. Multiple 2-D holograms of a sample illuminated with
various angles are measured, from which 3-D RI map of the sample is
reconstructed via the diffraction theory. ODT has been proved as a powerful
tool for the study of biological cells, due to its non-invasiveness, label-free
and quantitative imaging capability. Recently, our group has demonstrated that
a digital micromirror device (DMD) can be exploited for fast and precise
control of illumination beams for ODT. In this work, we systematically study
the precision and stability of the ODT system equipped with a DMD and present
measurements of 3-D and 4-D RI maps of various types of live cells including
human red blood cells, white blood cells, hepatocytes, and HeLa cells.
Furthermore, we also demonstrate the effective visualization of 3-D RI maps of
live cells utilizing the measured information about the values and gradient of
RI tomograms.
