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We compare the filtered backpropagation algorithm with the filtered backprojection algorithm for reconstructing the complex refractive-index distribution of semitransparent, cylindrical objects. Before reconstruction, the recorded scattered light is propagated back to the reconstruction area by inverse diffraction. Our comparison is based on computer-simulated data, and experimental optical data obtained from fibers with step-index, graded-index, and uniform-index distributions. The results show that both the filtered backpropagation algorithm and the filtered backprojection algorithm can produce accurate reconstructions of the complex refractive-index distribution as long as the weak-scattering approximation is valid. The good agreement between the results obtained from these two reconstruction algorithms indicates that the errors introduced by the assumption of straight-line propagation inside the object are negligible compared with those introduced by the weak-scattering approximation.

Summary Optical diffraction tomography (ODT) is used to reconstruct the complex refractive index distribution in cross‐sections of semi‐transparent, birefringent fibres. The selected fibres were polymer and animal fibres of either circular or non‐circular cross‐section with average thicknesses in the range 8–110 μm. This choice of samples was made to illustrate the imaging capabilities of ODT, and also to demonstrate some potential applications of the technique. The images representing the reconstructed refractive index distributions have a spatial resolution of about 2 μm, and show noticeable image contrast for refractive index variations of about 0·001. The ODT reconstructions compare well with refractive index information provided with the samples, and with scanning electron micrographs of cross‐sections of the same fibre samples. From these results it appears that ODT can be used to reconstruct the complex refractive index distribution in cross‐sections of semi‐transparent, birefringent fibres.

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Optical diffraction tomography (ODT) is applied to reconstruct the cross-sectional, complex refractive index distribution of cylindrical objects. Experimental reconstructions showing noticeable image contrast for refractive index variations of about 0.001, and having a spatial resolution of about 2 pm, are obtained for objects with cross-sectional diameters of about 100 pm. The results demonstrate that ODT can be used for quantitative imaging 0L semitransparent fibers.