Quantitative phase-contrast microscopy by angular spectrum digital holography

Techniques of digital holography are improved in order to obtain high-resolution, high-fidelity images of quantitative phase-contrast microscopy. In particular, the angular spectrum method of calculating the holographic optical field is seen to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. Spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. The reconstruction distance does not have a lower limit and the off-axis angle between the object and reference can be lower than the Fresnel requirement and still be able to cleanly separate out the zero-order background. Holographic phase images are largely immune from the coherent noise common in amplitude images. Together with the use of a miniature pulsed laser, the resulting images have 0.5 μm diffraction-limited lateral resolution and the phase profile is accurate to about 30 nm of optical path length. SKOV-3 (ovarian cancer cells) and HUVEC (human umbilical vein endothelial cells) are imaged that display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. The technique clearly exceeds currently available methods in phase-contrast optical microscopy in the level of resolution and detail, and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available.