The enhancement of the ultrasonic images by a special signal processing for side drilled holes of the NPPs S/G material and multi-layers inner-gaps

In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. In this experiment, there are two kinds of specimens, one is a reference block having 1/4T, 1/2T, 3/4T each side drilled holes as main run piping material of the steam generator in NPPs and the another is a part of a hemisphere type specimen having about 1-2 mm distance gap. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using special signal processing; a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously. Further more we have studied the reconstruction method of the amplitude and phase images and the enhancement method of the defect images' contrast