A laser Doppler Vibrometer (LDV) is a non-contact vibration velocity (or displacement) transducer which uses the Doppler shift of back scattered laser light (He-Ne, of wavelength of 633 nm) from a moving surface.
Vibration frequencies from DC to MHz can be measured. Due to the non-contact nature the measurement doesn’t affect the test object. Therefore, the LDV offer special benefits where the test object is remote, light, small, hot or rotating.
The LDV is a point measuring instrument and for obtaining field measurements a sequence of single point measurements is needed. Our Polytec PSV 300 LDV system is equipped with a camera and a scanning system (composed by two small servo controlled mirrors) and offers the possibility of surface are measurements and can be applied to experimental modal analysis where the resonance frequencies and the corresponding mode shapes can be measured and visualized.
By using a special arrangement, refractive index variations in air can be measured and visualized. Since the years 2003-2007, the scanning LDV has also been used as a equipment for measurement and visualization of 2D sound fields.