A new technique is proposed for noncontact measurement of bending vibr
ation directly from a rotating component. This notoriously difficult a
nd previously unattained measurement is a further development of laser
Doppler vibrometry. Simultaneously the technique provides an accurate
measure of shaft torsional vibration in situations in which measureme
nts of torsional vibration have shown significant sensitivity to bendi
ng vibration. Experimental results validate the theory developed, and
a conservative estimate of the minimum measurable bending vibration is
made at 20 millidegrees. (C) 1996 Optical Society of America