This award provides funds to determine the feasibility of constructing an electro-optical microscope that has the capability of yielding high quality, quantitative images of three-dimensional semitransparent objects without the need of physically slicing the specimen prior to imaging. The microscope generates a reconstruction of the three-dimensional complex index of refraction of an object by digitally processing multiple Gabor holograms of the structure using the filtered back-propagation algorithm of diffraction tomography. The Phase I program has as its principal goal the determination of the practicality of the underlying microscopic principle in relation to the sensitivity of the reconstruction procedure to noise and other error sources and the determination of the imaging performance of such a microscope under less than ideal operating conditions. A prototype breadboard design of the system will be completed during the Phase I program.