Subsurface defect detection in ceramics using an optical gated scatter reflectometer

We demonstrate the use of optical gating techniques for determining the size and location of defects in advanced ceramic materials, The subsurface region in various silicon nitride ceramic materials is probed. using an optical gated reflectometer based on a low-coherence fiber interferometer. Experimental results indicate that the size and distribution of small subsurface defects can be determined with depth and lateral resolutions of 10 and 7 mu m, respectively.