In rotating machinery variations of modal parameters with rotation speed may be extremely important in particular if very light and undamped structures are taken into account, like helicopters rotors or windmills.
The relation between natural frequencies and rotation speed is expressed in the form of Campbell diagrams. However it could be required to know also the deviation operational or modal shapes.
In several cases it is not possible to fully control the rotating speed of the machine and only coast-down tests can be performed. Such kind of tests is often fast due to the reduced inertia of rotors: for this reason it appears very promising in terms of efficiency. However the coast-down control is very difficult, it causing an unsteady condition of vibration, and it produces large amount of information that .
The need to obtain ODS requires the measurement in a large number of points and therefore a very efficient approach in the measurement must be developed.

A non-contact technique that allows to measure ODS and natural frequencies excited in rotating conditions is needed. The continuous scanning technique is the best candidate it being a full-field method able to fast measure the complete surface of the rotor.
In fact if TLDV already demonstrated the capability to measure vibration during run-up or coast down in a single point, the scanning of a complete grid of points on the rotor is very time consuming.
The coupling of Tracking capability with the continuous scanning approach will be investigated on the present paper.
The comparison of different algorithms of CSLDV will be performed and an exhaustive analysis of performances will be shown.