Research On Optical Diffraction Tomography With Large-Angle Beam Scanning Based On Elliptical Mirror

Optical diffraction tomography(ODT), as a non-invasive and label-free imgaing technoloy with the cability of superresolution and three-dimensional(3D) imaging, opens new ways for 3D tissue imaging. With the growing computatinal power, the method becomes a feasible and flexible tool in modern imaging. However, in current implementations, there are problems that high resolution and isotropic resolution cannot coexist, spectrum deficiency may affec the accuracy of the reconstruction, which constrains the ODT technology on the further improvement of resolution and accuracy of reconstruction.The subject “research on optical diffraction tomography with large-angle beam scanning based on elliptical mirror” aimed at sovling the presented problems, carries out an exploration research on introducing high numerical aperture(NA) elliptical mirror into the the ODT system to obtain a high and isotropic resolution and to significantly reduce the missing spectrum range to improve the reconstruction accuracy. The main research work is as follows,Firstly, based on the existing high numerical aperture elliptical mirror focusing theory, to meet the requirement of the modeling and analyzing the ODT system based on a high NA elliptical mirror, a more concise model of the elliptical mirror apodization factor has been proposed, and the relationship between the amptitude change and the incident angle of the light beam has been established.Then a principle that segments the reflector into tiny element mirrors and makes them work independently to achieve beam scanning has been proposed, and based on which the elliptical mirror and the ODT system are combined together. The system’s 3D frequency conponent collection ability model and 3D transfer function model have been established under the first order Born approximation. And the cut-off range of the 3D transfer function has been modelled and analyzed. By comparing with the traditional implementations, it has been found that the system’s axial spectral bandwidth has been greatly enhanced, and the missing spectrum part has been obviously reduced, while the improvements on the lateral resolution are related with the used objectives’ NAs, and the promotion improvement effects are more obvious if the NA is smaller.At last, the method of applying the high NA elliptical mirror to the ODT imaaging system has been studied and a concrete implementation scheme has been designed. Then a system has been built as an implementation of the designed scheme to experimentally verify the realization of beam scanning. During the process of building the system, a simple but effective method to accurately locate the focal points of elliptical mirrors has been presented. The experiment results show that the conttrollable beam scanning in Zθand Xθ directions has been achieved, and a 20μmx20μmx20μm-large field of view has been obtained. This conforms the feasibility of the ODT system with large-angle beam scanning using an elliptical mirror based on the element mirror segmentation principle, thus providing an effective solution to the challenge of applying an elliptical mirror to an ODT system.