A NEW SPECKLE NOISE SUPPRESSION TECHNIQUE USING CROSS-CORRELATION OF ARRAY SUB-APERTURES IN ULTRASONIC NDE OF COARSE GRAIN MATERIALS

摘要

In ultrasonic NDE, materials with coarse grains are difficult to inspect because a significant portion of energy will be reflected by the grains which cause speckle noise when imaging. Coarse grain materials are widely used in industry therefore a suitable inspection technique must be developed. This paper presents Spatially Averaged Sub-Array Correlation Imaging (SASACI), an advanced method that reduces speckle noise. SASACI was validated through comparison with the Total Focusing Method. A mean noise reduction of over 20dB SNR was observed when inspecting a highly scattering nickel alloy at 5MHz with a 128 element array.