15 October 2012 Research on reconstruction of spatial density distribution using optical interferometry and tomography
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Proceedings Volume 8420, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical System Technologies for Manufacturing and Testing; 84200H (2012) https://doi.org/10.1117/12.976053
Event: 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies (AOMATT 2012), 2012, Xiamen, China
Abstract
In this article, an interference digital testing method for measuring spatial density distribution of transmissive objects is presented. This method applies a radial shearing interferometer to test the density field from 8 projections in the same plane. By taking advantage of the regularized phase-tracking technique (RPT), the single interferogram will be demodulated to two-dimensional phase distribution of the corresponding projection beam. Then the phase data on one given cross-section of every projection is selected to form 8 curves, which describe one-dimensional phase variation on the given cross-section from each projection. Regarding these curves as computer tomography projection data, the refractive index distribution of the given cross-section can be reconstructed utilizing the algebraic reconstruction technique (ART). Thus, a three-dimensional distribution of refractive index can be obtained by applying the method above to different cross-sections in order. Finally, we are capable of calculating the spatial density distribution with the relation between density and refractive index of the substance tested. In addition, the density field testing for hypersonic flow field is investigated as an example in this article. Considering the fact that the target model in the optical window center of a wind tunnel will inevitably block some testing beams, which will lead to the sharp decline in accuracy of the testing results, a modified algebraic reconstruction technique which improves accuracy by introducing biharmonic spline interpolation is presented. In simulation, an error less than 3% in non-block situation is reached while an error less than 8% in small-area-block situation is also obtained.
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Tong Ling, Dong Liu, Chao Tian, Lei Sun, Yongying Yang, "Research on reconstruction of spatial density distribution using optical interferometry and tomography", Proc. SPIE 8420, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical System Technologies for Manufacturing and Testing, 84200H (15 October 2012); doi: 10.1117/12.976053; https://doi.org/10.1117/12.976053
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