Dual-Laser vibrometry: Elimination or extraction of pseudo vibration

This paper investigates the principal idea of a method using two identical laser vibrometers to eliminate pseudovibrations, occurring as structured noise in laser-vibrometer measurements of angular velocity of a rotating object. Thetwo vibrometers monitor the same surface path on the rotating object, but are separated by a well specified angle. Thus,they are aligned in such a way that they observe the same speckle patterns, but with a relatively time lag given by theangular separation of the vibrometers and the angular velocity of the object. However, any physical variations in angularvelocity of the object occur simultaneously at the two vibrometers. Knowing the angular separation between thevibrometers, simple trigonometry canbe used to eliminate the pseudo vibrations. These vibrometers are based oncameras, therefore the experiments demonstrate the principle of the method only, and no real time measurements areobtained here.