Abstract
Phase-contrast imaging of living tissues is important for investigating biological structures and functions.
Phase-contrast scanning optical microscopy using hollow-cone illumination, annular aperture, and active
image processing has been proposed and developed for visualizing low-contrast phase objects. This
microscope has such excellent features as separate phase and amplitude imaging, reduced multiscattering
effects, spherical aberration-free imaging, and speckle reduction for coherent lasers. A figureof-
8-mid-range enhancement spatial-frequency filter with sign correction extracted linear phase-contrast
components, and the reconstructed phase spectrum with superimposed spectra with different angles
revealed the phase-contrast structures of the tissue sample. We obtained cross-sectional images along the
axial direction and evaluated the microscope’s imaging features.
