Digital holographic microscopy with dual-wavelength phase unwrapping.

We apply the techniques of digital holography to obtain microscopic three-dimensional images of biological cells. The optical system is capable of microscopic holography with diffraction-limited resolution by projecting a magnified image of a microscopic hologram plane onto a CCD plane. Two-wavelength phase-imaging digital holography is applied to produce unwrapped phase images of biological cells. The method of three-wavelength phase imaging is proposed to extend the axial range and reduce the effect of phase noise. These results demonstrate the effectiveness of digital holography in high-resolution biological microscopy.