Noninvasive Surface Inspection Via Speckle Correlation

Many medical products and devices require a means of nondestructive noninvasive, high resolution interrogation of surface features in order to insure standards of quality and safety. This proposal describes techniques for nondestructive, non contacted sensing and evaluation of very small (fractions to tens of microns) lateral surface features. Laser speckle backscattered from a laser illuminated surface may be courier transformed and autocorrelated or cross correlated to detect anomalous surface features; feature dimensions may be determined by analyzing the characteristic Fourier spectrum intensity and distribution. Two configurations are suggested for demonstrating this technique based on photorefractive optical signal processing techniques and second order scattering or speckle statistics.