Almost every machine requires rotating parts for proper functioning: To improve the design regarding fatigue, life time, reliability, sound radiation, wear and tear and tolerances, as well as the measurement of temperature or flow distribution, continuous measurements of rotating components are necessary. Often, such measurements are very difficult to perform, sometimes it is not feasible at all.

A possible solution is offered by the ROTOSCAN system from Steinbichler Optotechnik. ROTOSCAN creates a standing image of rotating objects with the help of a prism rotating with angular velocity.

By compensating the rotating movement with ROTOSCAN, continuous vibration and deformation measurements with, e.g., a laser velocimeter or a holographic interferometer can be executed for any rotating part such as brake discs, fans, flywheels, clutch disks, marine screw propellers, generators and turbines.

Additional applications are in the field of flow diagnostics as well as in the measurement of temperature distributions with the help of an IR-camera. The simple continuous observation of rotating parts is, of course, possible as well.

Measurement Examples and Optical Set-Up

For the measurement of the out-of-plane vibration distribution of rotating components, ROTOSCAN can be integrated into a holographic interferometer. The illumination of the test object is done in coincidence to the oberservation by a beam splitter. The light reflected by the object is recorded in a holographic interferogram after the turning movements are compensated by ROTOSCAN. The evaluation of the interferogram can be done conventionally or computer-based.

ROTOSCAN is excellently suited for the measurement on test parts like turbines, fans, disc brakes, fly wheels, clutches, propellers, tires, etc.

A simple experimental set-up with a fan is shown in the figure below. The synchronisation of propeller and prism is done either manually or by an encoder or (almost) any pulsed signal. A stationary view is seen after reflection at the roof-edged prism and beam deviation by a beam splitter in front of the prism.

The advantage of the ROTOSCAN system is that the whole object can be observed continuously and not only for a short time at the same point of rotation angle as it is the case with stroboscopic viewing.