The scanning laser vibrometer or scanning

laser Doppler vibrometer A laser Doppler vibrometer (LDV) is a scientific instrument that is used to make non-contact vibration measurements of a surface. The laser beam from the LDV is directed at the surface of interest, and the vibration amplitude and frequency are extr ...

, was first developed by the British loudspeaker company, Celestion, around 1979, further developed in the 1980s,Stoffregen, B., Felske, A., “Scanning Laser Doppler Analysis System,” SAE Paper No. 850327, 1985. and commercially introduced by Ometron, Ltd around 1986. It is an instrument for rapid non-contact measurement and imaging of vibration. Fields where they are applied include automotive,

medical Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...

aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astr ...

, micro system and

information technology Information technology (IT) is the use of computers to create, process, store, retrieve, and exchange all kinds of data . and information. IT forms part of information and communications technology (ICT). An information technology system (I ...

as well as for quality and production control. The optimization of

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, suc ...

and acoustic behavior are important goals of product development in all of these fields because they are often among the key characteristics that determine a product's success in the market. They are also in widespread use throughout many universities conducting basic and applied research in areas that include

structural dynamics Structural dynamics is a type of structural analysis which covers the behavior of a structure subjected to dynamic (actions having high acceleration) loading. Dynamic loads include people, wind, waves, traffic, earthquakes, and blasts. Any structu ...

modal analysis Modal analysis is the study of the dynamic properties of systems in the frequency domain. Examples would include measuring the vibration of a car's body when it is attached to a shaker, or the noise pattern in a room when excited by a loudspeak ...

, acoustic optimization and

non-destructive evaluation Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), n ...

. The operating principle is based on the

Doppler effect The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who d ...

, which occurs when light is back-scattered from a vibrating surface. Both velocity and displacement can be determined by analyzing the optical signals in different ways. A scanning laser vibrometer integrates computer-controlled X,Y scanning mirrors and a video camera inside an optical head. The laser is scanned point-by-point over the test object's surface to provide a large number of very high spatial resolution measurements. This sequentially measured vibration data can be used to calculate and visualize animated deflection shapes in the relevant frequency bands from

frequency domain In physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency, rather than time. Put simply, a time-domain graph shows how a si ...

analysis. Alternatively, data can be acquired in the

time domain Time domain refers to the analysis of mathematical functions, physical signals or time series of economic or environmental data, with respect to time. In the time domain, the signal or function's value is known for all real numbers, for the cas ...

to, for example, generate animations showing

wave propagation Wave propagation is any of the ways in which waves travel. Single wave propagation can be calculated by 2nd order wave equation (standing wavefield) or 1st order one-way wave equation. With respect to the direction of the oscillation relative to ...

across structures. In contrast to contact measuring methods, the test object is unaffected by the vibration measuring process. Vibrometry covers a huge range of applications such as the study of

microstructures Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as metals, polymers ...

moving only a few pm at frequencies up to 2.5 GHz, all the way up to the intense dynamics occurring in

Formula 1 Formula One (also known as Formula 1 or F1) is the highest class of international racing for open-wheel single-seater formula racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The World Drivers' Championship, ...

engines with vibration velocities approaching 30 m/s. A 3D scanning vibrometer combines three optical sensors that accurately detect dynamic movement from different directions in space in order to completely determine the 3D vectors of motion. The software allows each individual x-, y- or z-direction component to be displayed independently, or combined into a single representation. Data can be exported for

finite element The finite element method (FEM) is a popular method for numerically solving differential equations arising in engineering and mathematical modeling. Typical problem areas of interest include the traditional fields of structural analysis, heat ...

model validation In statistics, model validation is the task of evaluating whether a chosen statistical model is appropriate or not. Oftentimes in statistical inference, inferences from models that appear to fit their data may be flukes, resulting in a misunderstan ...

at nodes previously imported from the model for scan grid definition.

References

{{reflist
Einsatz der Scanning-Laservibrometrie zur Messung von Schallschnelleverteilungen an Maschinen und Aggregaten
(PDF; 70 kB) von E. Winkler, H. Steger, 8. Forum Akustische Qualitätssicherung

External links

The measurement principle of laser doppler vibrometers and typically used laser sources

Introduction to laser Doppler vibrometry and physical principles

Video of the basic principles of laser Doppler vibrometry
Metrology Measuring instruments Laser applications