The Improvement of Resolution on the Ultrasonic Inspection Method

Abstract

Several data processing techniques used in petroleum exploration are applied to ultrasonic data to enhance resolution and signal to noise ratio. First, in the case of a medium of low absorption characteristics, the effectiveness of a wavelet processing, a deconvolution filter and a CDP stack is demonstrated. Second, in the case of a medium of high absorption characteristics, an attenuation coefficient is estimated using the spectrum ratio method. Waveforms at an arbitrary depth can be synthesized by the estimated attenuation coefficient and the reflected wave at the reference depth. Wavelet processing, which utilizes the synthesized wavelets at each depth as the new basic wavelet including the absorption characteristics, greatly improves resolution. Finally, the wavelet processing, the migration processing and the synthetic acoustic impedance log are applied to the data from a phantom model which exhibits ultrasound responses similar to those in a human liver. The fluid-filled objects, 10 mm in diameter, are not only resolved, but the polarity and phase information in the reflected waves is also preserved through these processings. Consequently, it is concluded that pin-holes in metals or small size cysts or tumors in a human body are detectable by the enhancement of resolution of ultrasonic diagnosis.