Development of a scanning head for laser Doppler vibrometry (LDV) using dual optical wedges

Research data for this paper is available on request from Steve Rothberg (s.j.rothberg@lboro.ac.uk).A new laser Doppler vibrometry scanning head is proposed based on a pair of rotating optical wedges. A comprehensive mathematical model is developed and used to demonstrate how the wedges can be configured to scan point-by-point, in a line, in a circle, and in a combination of the two such that a straight line scan could be performed on a structure during rotation. Inevitable misalignments are incorporated into the model and considered quantitatively for the circular tracking application. Certain advantages are apparent over systems based on dual mirrors and a Dove prism in terms of lower apparent velocities at low rotation orders. A scanning head design for the circular tracking application is presented, together with experimental data showing good agreement between predicted and measured apparent velocities caused by misalignments