Architectures and Processing for Improving the Sensitivity of Laser-Based Ultrasonic Phased Arrays

The advantages of contact phased array detection of ultrasound have been successfully demonstrated and used in commercial applications for many years. If one phases the individual detector elements the receiver has the potential for electronic beam steering and can produce higher spatial resolution. Furthermore, pixelized imaging can be used to ]produce C-scans, and substantially reduce the time required for inspection. While the use of phased-array detection has been proposed [1], until recently it has not been cost effective to apply the power of discrete element array processing to laser-based ultrasound receivers [2]. As an alternative, several groups have investigated the notion of synthetic array processing [3,4] by raster scanning a single detector element. In this paper we present an architecture for laser-based ultrasound receiver arrays that can be realized cost effectively using photo induced-emf detectors [5–7]. Our simulations of the array performance indicate that there are conditions that provide both high temporal resolution (when operating with a short-pulse laser pinger source) and simultaneous high spatial resolution.