Real time imaging of acoustic wave devices

Abstract

An acoustic wave imaging system comprises a prism for mounting to the back surface of a piezoelectric substrate of an acoustic wave device. The piezoelectric substrate comprises a front surface on which metallic interdigitated input and output transducers mount for generating acoustic waves on or below the front surface. An electric signal source connects to the input transducer while a load connects to the output transducer. The device may also include spaced metallic reflectors. A large laser beam propagates through an entrance face of the prism, passes through the back surface of the piezoelectric crystal and internally reflects off the front surface of the piezoelectric crystal. The laser beam diffracts into a number of components due to the creation of periodic surface corrugations and or periodic refractive index perturbations beneath the surface, which are caused by the acoustic waves. The beam components exit the prism and are focused by a lens onto its image plane. A spatial filter located at the focal plane of the lens blocks unwanted or undiffracted beam components while passing a diffracted component onto the image plane where it is detected by a charge coupled array device for real-time display, using a frame grabber and a computer to generate the display.