Accession Number : ADD004408

Title :   Method for Determining Changes in Spacing between Two Positions of Interest.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE AIR FORCE WASHINGTON D C

Personal Author(s) : Sharpe,William N , Jr ; Hollenberg,Glenn W

Report Date : 27 Sep 1977

Pagination or Media Count : 6

Abstract : The method of determining the change in the spacing between two positions on a single object or a position on each of two objects, by affixing two linear scatterers at the two positions; illuminating the scatterers with coherent monochromatic light from a source such as a He-Ne laser and obtaining an indication of the relative movement from changes in the interference pattern is described. In one apparatus, linear scatterers are positioned on opposite sides of an adhesive in a lap joint. The scatterers are illuminated with light from a He-Ne laser to produce an interference pattern on a screen. Movement of a preselected fringe on the screen will provide an indication of strain in the adhesive lap joint. In another apparatus, fibers are attached to the ends of a standard bar specimen and a test bar specimen which are placed in a furnace. The fibers are then illuminated with light from a helium neon laser to produce an interference pattern. A slit in a mask is positioned at a predetermined angle with respect to the zero order fringe. A photodetector is placed behind the mask. The output of the photodetector is displayed on a strip chart recorder together with a temperature signal. (Author)

Descriptors :   *Patents, *Displacement, *Measurement, *Strain(Mechanics), Joints, Monochromatic light, Coherent radiation, Light scattering, Helium neon lasers, Photodetectors

Subject Categories : Test Facilities, Equipment and Methods
      Optics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE