Minimum variance ultrasonic imaging applied to an in situ sparse guided wave array.
Ultrasonic guided wave imaging with a sparse, or spatially distributed, array can detect and localize damage over large areas. Conventional delay-and-sum images from such an array typically have a relatively high noise floor, however, and contain artifacts that often cannot be discriminated from damage. Considered here is minimum variance distortionless response (MVDR) imaging, which is a variation of delay-and-sum imaging whereby weighting coefficients are adaptively computed at each pixel location. Utilization of MVDR significantly improves image quality compared with delay-and-sum imaging, and additional improvements are obtained from incorporation of a priori scattering information in the MVDR method, use of phase information, and instantaneous windowing. Simulated data from a through-hole scatterer are used to illustrate performance improvements, and a performance metric is proposed that allows for quantitative comparisons of images from a known scatterer. Experimental results from a through-hole scatterer are also provided that illustrate imaging efficacy.
Hall
James
J
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
Michaels
Jennifer E
JE
D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D014159:Transducers; D014463:Ultrasonography / Q000379:methods*