Tomographic diffractive microscopy of transparent samples

We report a tomographic diffractive microscope, which permits imaging non-labelled transparent or semi-transparent samples. Based on a combination of microholography with a tomographic illumination, our set-up creates 3-D images of the index of refraction distribution within the sample. One acquires successively interferograms, rotating the illumination (the specimen being static) and using phase-shifting holography. Within the first Born approximation, each interferogram is interpreted as a subset of the Fourier transform of the specimen index of refraction distribution. The reconstruction is therefore similar to synthetic aperture imaging: one recombines the information in the Fourier space, and a final Fourier transform gives a 3-D image of the specimen. First recalling the theoretical foundations, we then describe our experiment, and show initial results obtained on biological samples. PACS. 42.30.Wb Image reconstruction; tomography – 42.30.Kq Fourier optics – 42.40.Kw Holographic interferometry; other holographic techniques