Hand held phase-shifting diffraction moire interferometer

A method of determining in-plane deformation of an object on the basis of diffraction of rays by a diffraction grating replicated onto the surface of said object, the steps comprising:

• providing from a source a beam of coherent light;
• coupling said beam to a polarization maintaining, single mode optical fiber;
• transmitting said beam of coherent light through said single mode optical fiber to a remote hand held unit;
• collimating within said hand held unit the transmitted coherent beam of light;
• aligning said collimated beam of light with the diffraction grating by positioning said hand held unit over the diffraction grating;
• reflecting the collimated beam off a first mirror so that a first portion of the collimated beam is directed toward the diffraction grating at an oblique incident angle and a second portion of the collimated beam is directed toward a second mirror within said hand held unit;
• reflecting said second portion of the collimated beam off the second mirror so that the second collimated beam is directed toward the diffraction grating at an oblique incident angle that is equal to but opposite said first collimated beam incident angle;
• imaging, identifying and recording interference patterns created by diffraction of said beams as a result of deviation in said diffraction grating.

A hand held interferometer system for performing the method of diffraction moire, comprising:

• a case;
• means for creating a beam of coherent light, said means contained within the case, coupling means for coupling said beam of coherent light to a polarization maintaining, single mode optical fiber within an optical fiber, said coupling means contained within the case;
• a remote hand held unit tethered to said case by said optical fiber;
• optical means within said remote hand held unit for directing and aligning said coherent beam through separate paths at a diffraction grating replicated onto the surface of a test specimen, said separate coherent beam paths having opposite but equal incident angles to the test specimen;
• observation means for viewing and measuring interference patterns created by the diffraction of said beams by said diffraction grating;
• and
• recording means for permanently registering said measured interference pattern data.