Resolution improvement of ultrasonic C-scan images by deconvolution using the monostatic point-reflector spreading function (MPSF) of the transducer

This paper describes a digital signal processing method called 'post-focus processing'. The method reduces the transducer blurring effect and improves the resolution of ultrasonic C-scan images by simultaneously performing 3-D (2-D spatial and temporal) deconvolution using the MPSF (monostatic point-reflector spreading function) of the transducer. This method was applied under different imaging conditions, including the near-field and far-field of non-focused transducers and the defocused state of a focused transducer. In order to compare the proposed technique with other deconvolution methods, results from numerical simulations and experiments are presented. The results of numerical simulations of C-scan imaging with post-focus processing and 2-D Wiener deconvolution are reported. Experiments were conducted using post-focus processing and three known image resolution improving methods including axial-Wiener deconvolution, 2-D Wiener deconvolution and pseudo 3-D Wiener deconvolution. Results show the MPSF is a crucial blurring factor affecting the image resolution of C-scan images, and the post-focus processing method is more effective and generally applicable than the others. Copyright (C) 1996 Elsevier Science Ltd.