A real-time holographic microscope for phase imaging is described. The image-formation process is based on the aberration-correcting capability of phase-conjugate illumination. After it has passed through a phase object, the light from a laser beam is recorded as a reflection hologram within a crystal of barium titanate by the self-pumping process. Such a reflection hologram, when illuminated, returns the phase conjugate of the incident distorted optical field. The object is then displaced slightly, and the phase conjugate of the field produced by the undisplaced object now passes through the displaced object. This produces in the object plane an intensity pattern that is an image of gradients in phase retardation. A microscope (objective and ocular) creates a magnified image of the pattern. A digital processor grabs video frames, subtracting from the gradient image the initial optical field acquired before the shift. The subtractive processing results in a final image free of coherent noise and artifacts. We describe the microscope and its operation and show representative images.
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