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-f ocus processing'. The method reduces the transducer blurring effect an d improves the resolution of ultrasonic C-scan images by simultaneousl y performing 3-D (2-D spatial and temporal) deconvolution using the MP SF (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 defocu sed state of a focused transducer. In order to compare the proposed te chnique with other deconvolution methods, results from numerical simul ations and experiments are presented. The results of numerical simulat ions of C-scan imaging with post-focus processing and 2-D Wiener decon volution are reported. Experiments were conducted using post-focus pro cessing and three known image resolution improving methods including a xial-Wiener deconvolution, 2-D Wiener deconvolution and pseudo 3-D Wie ner deconvolution. Results show the MPSF is a crucial blurring factor affecting the image resolution of C-scan images, and the post-focus pr ocessing method is more effective and generally applicable than the ot hers. Copyright (C) 1996 Elsevier Science Ltd.