Image quality improvement in optical diffraction tomography by multiple numerical propagations and separated reconstructions

The image quality of optical diffraction tomography is likely to decline due to some key factors, including limited depth of focus, the rotational error and localized RI discontinuities. This paper describes reconstruction methods to circumvent these three factors for improved image quality. The limited depth of focus and the rotational error are addressed simultaneously with a method based on multiple numerical propagations. The localized RI discontinuities are addressed with a method based on separated tomographic reconstructions. Experimental results are demonstrated to verify the described methods. A four-core optical fiber and a large-mode photonic crystal fiber is measured and processed by the method based on multiple numerical propagations with improved image quality. The depth of field is significantly extended. Samples with different typical RI discontinuities, two kinds of fusion spliced optical fibers, are measured and reconstructed. While reconstructions by existing methods are heavily disturbed, the 3D maps obtained with the described method are free from spreading disturbance and show important structures as well as the positions and estimated shapes of the discontinuities. The described methods are of practical significance and will find important applications in 3D imaging of various objects.