Patent ID: 6765677
Filing Date: 2004-07-20
Classification: G01B,G01L

Abstract:
A method for performing measurements of residual stresses in an investigation area of an object by use of optical holographic interferometry technique, in which a device used to perform the measurement includes:a coherent light source and a registering medium arranged in a environment at a distance from the object which is to be investigated; a first single-mode light guidance cable that transmits the coherent light from the light source to the investigation area of the object that is to be investigated in such a manner that it illuminates the investigation area; a second single-mode light guidance cable that transmits the coherent object light, which scatters off the investigation area of the object which is to be investigated from the investigation area to the registering medium in such a manner that it illuminates the registering medium; and a stress relief device that induces a release of the residual stresses at the object in situ while the formation, registration and development of the holographic image and formation of the interferogram of the investigation area of the object are performed in said environment, the method comprising: registering and developing a hologram of the investigation area of the object on a registering medium; subjecting a small region of the investigation area of the object to a release of the residual stress; forming an interferogram of the investigation area of the object by simultaneously illuminating the registering medium containing the developed holographic image of the investigation area of the object in the initial state and the investigation area of the object containing the region of released residual stresses with the reference and object beams, respectively, wherein the interferogram is formed as a result of interference between the two light waves which corresponds to the light waves scattered off the investigation area of the object before and after release of the residual stresses, and transmitting the coherent light between the object, light source, and holographic camera in single-mode light guidance cables, wherein the endpoints of the single-mode light guidance cables are securely attached in a fixed distance of the investigation area of the object and the recording medium thereby protecting the formation of the holographic image and interferogram of the investigation area from mutual relative displacements of the object, holographic camera and the light source.