Scanning Laser Acoustic Microscope Using Surface Acoustic Waves and Digital Image Processing

The operation of a scanning laser acoustic microscope which utilizes surface acoustic waves (currently at 100 MHz) is described. The microscope has the capability to digitize both the acoustic information and optical image and store them to disk for subsequent image processing. The image processing algorithms which take the acoustic displacement at the surface of the sample as input and invert th". wave equation to produce an acoustic image of either the wave number or velocity versus position is described. Test features (phantoms) composed of thin metal film structures of varying lateral dimensions and thickness have been fabricated on YZ lithium niobate SAW delay lines. These test samples have been used in the microscope and acoustic images of the "known" features have been acquired by the system.