Imaging an object buried in the sediment bottom of a deep sea by linearized inversion of synthetic and experimental scattered acoustic wavefields

This paper is concerned with the reconstruction, from measured (synthetic a nd experimental) data, of a 2D penetrable fluid-like cylindrical object of arbitrary cross-section imbedded in a fluid-like (sediment) half-space sepa rated by a plane interface from another fluid halfspace (deep water) wherei n propagates a plane acoustic interrogating wave. The Green theorem is used to provide (1) a domain integral representation (DIR) of the scattered fie ld and (2) a domain integral equation (DIE) for the pressure field in a tes t region containing the object. Both the DIE and DIR are discretized by col location, thereby leading to a linear system of equations for the discretiz ed pressure in the test region and a linear transform for the discretized p ressure outside the test region. This is the means adopted herein for gener ating synthetic scattered field data. The inverse problem is linearized by replacing the (unknown) field in the test region by the (known) field which is established in the water/sediment system in the absence of the object. Using this Born approximation and minimizing the discrepancy between the me asured and model scattered fields gives rise to a linear system of equation s for the (unknown) discretized index-of-refraction contrast function in th e test region. Due to its ill conditioned nature, the linear system is solv ed by a singular value decomposition technique. Images of the index-of-refr action contrast representation of the object obtained by inversion of both simulated and experimentally measured scattered field data are presented an d compared.