Accession Number : ADD003854

Title :   Method and Apparatus 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 : 29 Mar 1977

Pagination or Media Count : 6

Abstract : The patent describes 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 scatters 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. In one apparatus, linear scatterers are positoned 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.

Descriptors :   *Patents, *Thermal expansion, *Optical instruments, *Test equipment, Measuring instruments, Light scattering, Adhesives, Helium neon lasers

Subject Categories : Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE