Optical Non Destructive Testing Methods Using Continuous Wave, Pulsed or Diode Type Lasers

Optical Non-Destructive Evaluation (NDE) laser based methods include among others, Holographic Interferometry, its subsequent development into Electronic Speckle Pattern Interferometry ( ESPI ), and another speckle technique known as Shearography. These laser based methods are very attractive in that they provide full field view non-contacting means of determining material conditions, in engineering components, that may contribute or result in catastrophic failures. The major basic limitation of the above mentioned methods is experimental stability in that excessive motion or deformation of the object under test would cause wipe-out of information. This paper reviews the above three laser based optical NDE methods, namely holographic interferometry, electronic speckle pattern interferometry and shearography, used by the authors in the past, as tools able to measure deflections and their derivatives, as well as the detection and quantification of defects. Examples of Holographic Interferometry, ESPI and Shearography are included, together with recent results of the authors' research and development into the production of portable and relative inexpensive ESPI and Shearography equipment.