Vibration measurement instrument using laser Doppler holography

Historically the Rover test technology group has researched and developed optical based measurement techniques. Optical methods offer several advantages over classical techniques: the measurement is made in a noncontacting manner and therefore the mass and stiffness of the structure are not changed, very good measurement resolution is possible by utilising laser light, while field data can be acquired instantaneously using holographic or photographic techniques. In particular TV holography has been found to give real time, whole field measurements of the vibration and deformation of structures. However, the technology is complex and sufficiently unknown to structural engineers such that a significant barrier exists in transferring this technology to them. Therefore a series of projects have been undertaken to `de-skill´ the technology, thus enabling its transfer. The authors describe the problems in transferring holographic technology and the technological developments undertaken which address this issue