ACOUSTIC IMAGING DEVICE for a COATED SUBSTRATE PROVIDING SEPARATED COATING and SUBSTRATE INFORMATION
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
One serious drawback of all acoustic imaging systems known up to now is that they cannot separate the information on a subsurface thin-layer (of a few micron thickness) from the information on the substrate, since long wavepackets and long detection time-gates have been used so far, and depth resolution deeper than 100 microns from the surface is poor (many tens of microns). We show here a new device to detect and identify multiple echoes from thin-layers that are several mm below the surface, and separate information on the substrate and the layer can be obtained; this is possible since high time resolution and subnano- second acoustic single acoustic pulse are used. (Image Omitted) The preferred embodiment is schematically shown in Fig. 1. A sub- nanosecond excitation source (e.g., a 0.