Resolution enhancement algorithm utilizing multiple reflections for image reconstruction in the conduit

Abstract

In the acoustical endscopy, due to the physical limitations, the transducer array is composed of a small number of elements and each interspacing is larger than the acoustical wave length that is called a sparse array system. In such case, the volumetric image reconstruction process becomes ill-posed caused by the interference of the reverberation in the tube. Consequently, the reconstructed image is interfered by widely spread strong spurious lobes. This paper proposes a novel volumetric image reconstruction algorithm for a 3D sparse aperture acoustical holography, which visualizes the forward-looking image in the conduit tube. The proposed algorithm utilizes prior knowledge about both field, object, and observed signal as (1) the support of the object is limited within the conduit, and (2) the multiple reflected wave field scattered by the object is statistically independent of the reverberation in the tube. The proposed sparse array acoustical imaging system utilizes, therefore, the multiple reflected wavefronts in order to enhance the resolution. By experiments, it is proven that the proposed algorithm has the following improvements: (1) Targets can be identified when multiple reflections exist in the tubes. (2) Artifacts caused by the spurious lobes can be reduced.