Accession Number : ADD012140

Title :   Laser Vibrometer.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Rudd,Michael J

Report Date : 26 Nov 1985

Pagination or Media Count : 6

Abstract : This patent discloses optical interferometric apparatus for detecting and measuring discontinuities in structural materials from ultrasonic stress waves at their surfaces. The apparatus includes an acousto-optic (a/o) modulator which shifts a portion of a laser beam in frequency, producing a modulated light beam of light. This modulated light beam is deflected and passes through an adjustable lens to the surface being measured. The light scattered by the surface is focused by the lens on an end mirror of the laser which produced the original beam, and is divergingly reflected therefrom. The reflected, scattered light is heterodyned with the unshifted portion of the laser beam in a photodiode to produce a phase modulated signal at the acoustic frequency of the a/o modulator. Surface displacement can be measured

Descriptors :   *PATENTS, *OPTICAL INTERFEROMETERS, *STRUCTURAL ANALYSIS, *LASER APPLICATIONS, *ACOUSTOOPTICS, FREQUENCY SHIFT, HETERODYNING, PHOTODIODES, DISPLACEMENT, PHASE SHIFT, LASER BEAMS, MIRRORS, DEFLECTION, INTERFEROMETRY, STRESS WAVES

Subject Categories : Structural Engineering and Building Technology
      Test Facilities, Equipment and Methods
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE