Accession Number : ADP006788

Title :   Detection of the Transient Motion of a Scattering Surface by Two-Wave Mixing in a Photorefractive Crystal,

Corporate Author : INDUSTRIAL MATERIALS RESEARCH INST BOUCHERVILLE (QUEBEC)

Personal Author(s) : Ing, R. K. ; Monchalin, J. -P.

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Optical detection of the transient surface motion of objects is an area of far reaching practical importance. Applications Include the vibration monitoring of many engineering structures (power plants, aircrafts, engines of various kinds ... ) and more recently the detection of ultrasound produced by pulse laser excitation. This technique, now in active development in our laboratory and elsewhere, extends ultrasonic inspection of materials to conditions otherwise difficult or impossible (complex geometries, hot products on a production line ... ). Various optical systems have been devised for detecting surface motion have been recently reviewed. We are reporting here the novel use of two wave mixing in a photorefractive crystal for detecting such a motion and in particular ultrasonic displacement produced by pulsed laser excitation. This approach has the merit of being applicable to a rough surface by integrating over many speckles and of having a very broad frequency detection bandwidth. The use of two-wave mixing for coherent homodyne detection of arbitrary wavefronts was previously reported and applied to detection and amplification of an intensity modulated wave.

Descriptors :   *OPTICAL DETECTION, *REFRACTION, AMPLIFICATION, BANDWIDTH, CRYSTALS, DETECTION, DISPLACEMENT, ENGINES, EXCITATION, FREQUENCY, INSPECTION, INTENSITY, LASERS, MIXING, MONITORING, MOTION, PULSED LASERS, PULSES, SIGNALS, STRUCTURES, SURFACES, TRANSIENTS, ULTRASONICS, WAVEFRONTS, PULSED LASERS, BARIUM TITANATES, ULTRASONIC FREQUENCIES, COHERENT OPTICAL RADIATION, BEAM SPLITTING, OPTICAL LENSES, SYMPOSIA.

Subject Categories : Optical Detection and Detectors
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE