In order to establish traceability for vibration and shock measurements, hierarchies of measurement standards have been established and are operated at National Metrology Institutes (NMIs) as well as in accredited and non-accredited calibration laboratories. NMIs make use of laser interferometry, to realize and disseminate the unit and the associated scale of the physical quantity of acceleration. To meet the increasing demands, improved and new standard methods for vibration and shock calibration have been specified and implemented. At the PTB, primary vibration calibration of vibration transducers (accelerometers) by laser interferometry has been extended to the frequency range 0.4 Hz to 20 kHz. This enabled one of the calibration laboratories in Germany, within the framework of the Deutscher Kalibrierdienst (DKD), to be accredited for accelerometer calibration (comparison method) in the wide frequency range of 0.4 Hz to 20 kHz, too. In addition to the magnitude of the complex sensitivity of accelerometers, phases shift calibrations by laser interferometry have been extended to 10 kHz and confirmed by a bi-lateral comparison. Progress in interferometric primary shock calibration (peak acceleration from 50 m/s² to 100 km/s²) has made it possible to perform accelerometer linearity tests of low uncertainty better than 1%. High-accuracy calibrations of laser vibrometers have been achieved at frequencies up to 20 kHz. A novel high-frequency vibration exciter proved to be the basis for extending the calibration capabilities for laser interferometers towards higher frequencies (current target at PTB: 60 kHz). The advances achieved are described and demonstrated by experimental results.

A new interferometric system for dynamic force calibration was developed and investigated. The uncertainty of the system was analyzed by a direct comparison with the acceleration standard measuring devices of the PTB. The comparison includes acceleration measurements using laser vibrometer as well as the calibration of an accelerometer. The results of the comparisons have shown a good accordance of the new interferometric system used in dynamic force measurement with the acceleration standard measurement devices.

This paper outlines the current progress of measurement standards for vibration at the National Metrology Institute of Japan (NMIJ) since 2000. Up to 2000, two accelerometer calibration systems of national standards have established at the NMIJ. These two systems are for the low frequency range (1 Hz to 200 Hz) and for the middle frequency range (20 Hz to 5 kHz). They have been used for national calibration services and their uncertainties have been published on the Appendix C of the CIPM-MRA as the calibration and measurement capabilities (CMCs). Currently, other two systems are under development to extend calibration frequency range. One of the systems is for the very low frequency range (0.1 Hz to 80 Hz). And the other one is for the high frequency range (5 kHz to 10 kHz). The NMIJ is planning to establish these two systems until 2006, and to start the calibration services for 0.1 Hz to 10 kHz together with all 4 systems. Two systems under development are described. Technical features, uncertainty sources of the systems, and the future plan are reported.

This paper describes the study of the characteristics of the four-reflection interferometer components, the interferometer realization and the experimental results concerning the vibration measurement by the Minimum-point method and the Sine approximation method. The theoretical study of the beam intensity losses in all the optical components was performed. The comparison between this interferometer and the two-reflection interferometer used in IMGC, by applying the Minimum-point method, has shown comparable results about the sensitivity of the same vibration transducer in the range up to 10 kHz, a higher short term stability and the extension of the frequency range up to 20 kHz with the four reflection interferometer. The basic configuration of the four reflection interferometer was modified in order to get two output quadrature signals, which allow the determination of the amplitude and phase of the displacement by the Sine approximation method. This solution (interferometer and Sine approximation method) makes possible a further extension of the frequency limit to 30 kHz, displacement measurements of the order of nanometers, with a standard uncertainty of 50 pm and the application of a complete and automatic calibration procedure.

Photorefractive crystals offer many advantages over other classical holographic recording media. They allow fast in-situ processable holographic recording as well as indefinite reusability. Moreover high signal-to-noise ratio can be reached as well as high resolutions. We present the results obtained by pulsed holographic interferometry obtained with photorefractive crystals. First experiments showing the potentiality of photorefractive crystals for such applications will be reviewed. Some limitations were pointed out and led us to consider new developments under the frame of an European-funded project. The PHIFE European project (Pulsed Holographic Interferometer for the analysis of Fast Events) aims at developing a full field measurement system at a high repetition rate, based on a double-pulse YAG Q-switch laser. This device will be used for the analysis of vibrations and for aerodynamic studies. Different crystals are considered which are adapted to the fundamental line of the YAG (AsGa or CdTe crystals) or after frequency doubling at 532 nm (Bi₁₂SiO₂₀). Different crystal configurations and recording geometries are compared. Also different innovative phase quantification techniques are studied and take into account some special properties of the PRCs. We present the results obtained so far in the first development phases of the project.

Since the early 1990's, holography has been used worldwide to study the vibration of mechanical parts at the design stage. The so-called <<time average>> technique on holographic plates was able to give accurate information on the vibration modes of structures. TV-Holography has simplified the data capture, and also has the ability to easily produce amplitude and phase maps. This optical method is a powerful tool for vibration analysis but it needs to be used carefully to gain the full benefit of the data recorded. Then several types of analysis of these data may bring to the mechanical designer key information for the future life of the designed mechanical part. In this paper, we present a complete vibration analysis of a turbocharger turbine wheel, including the two main following points: the holographic recording method and the data post-processing that is done by the vibration experts. Concerning the data recording we will emphasize the experimental conditions that lead to data that are useful for the mechanical engineer: wheel preparation, wheel boundary conditions, method of excitation, geometrical conditions, tests complementary to the holographic recording. Experimental results are reported, showing the effect of the experimental conditions on the eigenfrequencies, eigemodes and damping factor. Concerning High Cycle Fatigue (HCF) on turbine blades of turbochargers, Holography is of gret help in two instances, predictive behavior at design stage and field failures analysis. For the first task, Holography confirms/refines the 3 or 4 first modes predicted by FEA models, it gives the high order modes not predictable by models (especially coupled inducer/backdisc modes) and also the damping factors that are not accurately predicted. Those data are then fed into an "Harmonic Analysis" which allows the prediction of a forced response and, subsequently, an answer about robustness with respect to HCF. For the second task, Holography provides accurate nodal lines which can be easily correlated with location of field cracks or fractures. A Campbell diagram can be used to identify the order of the aero excitation responsible for the failure. Corrective actions to the product design or recommendations for speed limit can then be taken accordingly.

Electronic speckle pattern shearing interferometry (ESPSI) is superior to Electronic speckle pattern interferometry (ESPI) when strain distribution, arising from object deformation or vibration, need to be measured. This is because shearography provides data directly related to the spatial derivatives of the displacement. Further development of ESPSI systems could be beneficial for wider application to the measurement of mechanical characteristics of vibrating objects. Two electronic speckle pattern shearing interferometers (ESPSI) suitable for vibration measurements are presented. In both ESPSI systems photopolymer holographic gratings are used to shear the images and to control the size of the shear. The holographic gratings are recorded using an acrylamide-based photopolymer material. Since the polymerization process occurs during recording, the holograms are produced without any development or processing. The ESPSI systems with photopolymer holographic gratings are simple and compact. Introducing photopolymer holographic gratings in ESPSI gives the advantage of using high aperture optical elements at relatively low cost. It is demonstrated that both ESPSI system can be used for vibration measurements. The results obtained are promising for future applications of the systems for modal analysis.

Full field optical measurement techniques have already entered into various fields of industrial applications covering static as well as dynamic phenomena. The electronic speckle pattern interferometry (ESPI) allows the non contact, sensitive and three dimensional measurement of displacements in the sub micron range of objects with dimensions from mm² to m². For dynamic and transient phenomena, the use of pulsed laser have already been reported for various applications and successfully proven for the determination of the structural response of different components. In this paper we would like to present recent developments in the field of pulsed ESPI applications where emphasis is put onto the full field measurement result. The use of a completely computer controlled system allows easy access to mode shape characterization, deformation measurements and the characterization of transient events like shock wave propagation. Recent developments of the 3D-PulseESPI technique led to a very compact and complete system with improved characteristics regarding robustness and operation. The integrated design of the illumination laser and sensors for image acquisition allows easy aiming and adjustments with respect to the object of inspection. The laser is completely computer controlled which is advantageously used in a completely automatic brake squeal inspection system, which captures the squealing signal, automatically fires the laser and provides the complete deformation map of the component under test. Examples of recent applications in the field of dynamic structure response, with an emphasis in the field of automotive applications are given.

Recently there has been an increasing interest in the application of shearography for modal analysis of vibrating objects. New interferometric systems, which are simple and flexible are of interest for engineering and industrial applications. An electronic speckle pattern shearing interferometer (ESPSI) with a very simple shearing device is used for study of vibrations. The shearing device consists of two partially reflective glass plates. The reflection coefficients of the coatings are 0.3 and 0.7 respectively. The distance between the two glass plates controls the size of the shear. The versatility of this simple shearing interferometer is shown. It is demonstrated that the ESPSI system can be used for vibration measurements and phase-shifting implemented for fringe analysis. The results obtained are promising for future applications of the system for modal analysis.

Fluid holography enables effective analysis of high speed flow problems, high frequency vibrations of micro-scale components and fluids in dosing and contacting units, high speed processes taking place in biological and chemical microsystems. The investigation of the high frequency vibrations of the fluid is an important problem in the design of various devices. Though the production stage of the interferograms is technically not extremely complicated, the interpretation of the produced fringes faces a number of mathematical and numerical problems. That is related with the complex geometry of the phase-shifting media. Under such circumstances the density can change along the line of sight, and the density is no longer proportional to phase. Therefore, development of hybrid numerical-experimental fluid holographic methods is important both for the interpretation of experimental results and for the analysis of systems in the virtual environments by generating realistic interferograms. In this paper the method of holographic interferometry is used for the analysis of the two-dimensional fluid problem. FEM analysis techniques are based on the approximation of nodal displacements (not the volumetric strains) via the shape functions. Conventional FEM would require unacceptably dense meshing for producing sufficiently smooth images. Therefore the technique for smoothing of the generated images representing the distribution of the volumetric strains and calculated from the displacement distribution is developed. The smoothing technique is based on conjugate approximation used for the calculation of nodal values of stresses and enables to obtain the images of better quality on a coarse mesh by using the displacement formulation for the calculation of the eigenmodes.

For specific materials, it is necessary to know the dispersion curve associated with the flexural waves, particularly in the case of anisotropic composite materials whose parameters are not known a priori. The method described here is based on energy concepts. It uses the vibration velocity measured by scanning laser Doppler vibrometer. The Spatial Fourier Transform (SFT) of vibration velocity field is used to compute the spatial derivatives of velocity which are then used to obtain energy quantities. The dispersion curve and the loss factor are computed from these quantities. It is shown that the use of these energy quantities leads to results independent to the analysis resolution in the wavenumber space, countrary to the direct extraction obtained by looking for the maximum values in the phase spectrum. The pre-processing allows one to eliminate the disturbances brought by the mechanical excitation zones and plate edges. Furthermore, the mechanical parameters for plane structures such as dynamic stiffness and loss factor, are estimated by this technique. This method can be extended to orthotropic and anisotropic structures. Experimental results are presented.

Scanning Laser Doppler Vibrometers (SLDV) are widely used in product development. Power tools as for example percussion drilling machines are known to be noisy and vibrating. It is state of the art to reduce the noise and vibration by finding the sources therefrom with LDV. Although these data give important information about the vibrational behavior, for a deeper understanding three dimensional vibration data is required. Therefore, for the first time measurements on power tools have been performed using a novel 3D SLDV, which simultaneously measures three components of the vibration vectors using three vibrometers. Power tools are observed under operating conditions close to reality, operated by a human. As the device under test performs movements in all directions, the three laser beams do not perfectly intersect. It is shown, that the introduced error can be neglected for low frequencies. Results are presented for a percussion drilling machine and a random orbit sander.

The perspective of employment to diagnose quality of functioning of rotor system and discovery of developmenting defects of vibrationing signals, which registrate in the work of rotor system is important for properties of strengthening vibrotransducers, for simplicity of fastening of nonconact lasering speed and for inductive measuring transducers of improvement. It is examine the diagnostic system in this work, in which apply a few contact and noncontact transducers (frame of rotor vibroacceleration, inductive measuring transducers of improvements, laser measuring transducer of speeds and measuring transducers of phase). It is investigate the rotor system in which can be assemble hydrodynamic bearings and bearings of rolling of different construction. The object of research in the base of diagnostic measuring is to ascertain characteristics of inside sources, which cannot get in method of direct measuring. The quality of ability to work of this system belongs from type of using transducers and from apportunitys of analyses of getting signals. Orbits of rotor center, spectrums, densitys and others statistic characteristics are given using computering system of diagnosing of rotor systems according to which we can decide about technical state of rotor system.

Eccentric type dis-balance type vibration excitation systems are analyzed in the paper. It is assumed that the dis-balance has an additional degree of freedom. It is shown that resonance vibrations in such systems can occur in the regime of self-resonance which is understood as a mode of motion when the driving shaft's angular frequency is high, but the generated vibration frequency is relatively low. Experimental investigations of the effect of self-resonance enabled to define the zones of existence of such motion modes. Such principle of vibration excitation can be successfully exploited in different areas of engineering as it eliminated the necessity of complex and expensive vibration control and stabilization equipment.

We presented the next step of our research connected with development of the vibrometry/velocimetry based on fiber into free space radiation and heterodyne detection of scattered light. Some experimental configurations utilizing erbium doped fiber amplifier (EDFA) are presented. We propose two solutions of optical interface between the fiber system and an object.

The optical fiber birefringence is modified by application of stress over the fiber. This characteristic is used in load cell development, using the polarimetric technique. A test sample is developed embedding the optical fiber in epoxy resin. This resin presents a high elastic module and permits a good transference of the stress acting on the resin to the optical fiber. The sensor consists of a polarized Ga-As laser coupled to a single-mode optical fiber of medium birefringence. A germanium device detects the signal variation imposed by the stress application. The output of this device (intensity of light as a function of load) is a quadratic sinusoidal curve. The theoretical stress acting on the fiber as a function of load was calculated by finite element method and by elasticity solutions of compose materials. Measurement of increase in load that corresponds to a period of the quadratic sinusoidal curve was used to compare phase change analysis based in birefringence theory with mechanical methods to calculate the relation between the applied stress and the stress acting on the optical fiber.

Reliable operation of underground mine shafts is strongly conditioned by the proper position of the shaft frame and the installations inside the shaft tube in relation to the vertical direction. For operational reasons and safety, they are subject to periodical control and emergency control in the case when the permissible values of the operational parameters are likely to be exceeded. These can be, for instance, the values of tilt of the shaft frame or of the irregularity of the bars which guide the conveyance (i.e. cage or skip) in the shaft. One of the reasons of such a situation to occur can be the movement of the ground in the closer or farther proximity of the shaft, as a consequence of the effects of mining, hydro-geological changes in the ground, etc.

If a laser Doppler vibrometer (LDV) probe beam is normally incident on a resonating metal strip with a mirror-finish, the retro-reflected beam has corresponding dynamic deflections. These lateral beam offsets are proportional to the dynamic surface tilt and can be measured along with the LDV velocity using a separating beam-splitter and a two-dimensional position sensitive detector (PSD). On a thin unbound strip resonating with 'pure mode' deformation, these derivative motions, velocity and tilt, are completely complementary. On a thin unbound plate resonating with 'hybrid mode' deformation, velocity and now two orthogonal tilts are nearly complementary. Maximal tilt has zero velocity, and maximum deformation or velocity has zero tilt. Intermediate values range in complementary fashion except near 'cross-nodes' zones. Here both motion types drop to zero at these cross-node locations. Both velocity and tilt signals are compared simultaneously using a special test fixture. This fixture consists of a stainless steel strip supported on its edges in the center, which can be excited by small speakers at the ends. Two comparison/calibration approaches are demonstrated with a pure 3-0 mode. Significant modal details are also demonstrated by analyzing multiple modes from pulsed excitation, and mapping a 3-1 mode-shape using the combined sensing approaches.

Laser techniques for vibration measurement, due to their non-contact nature, represents an interesting alternative investigational tool to be tested in biomedical and clinic fields. A particular application could be as evaluation method in design and quality control of artificial organs. Aim of this study is to investigate the application of laser vibrometry to the study of mechanical heart valves in-vitro, with an ad hoc set-up. A heterodyne laser Doppler vibrometry system, which allows the measurement of both vibrational velocity and displacement was used. Three different approaches have been carried out, in order to stress the limits of the laser vibrometry technique for testing heart valve prostheses. Critical points and difficulties to build up experimental studies in this field were clearly pointed out. In the present study only one laser head was used, the aim of the authors being to test the feasibility of a simplified approach on mechanical cardiac valves. Starting from that analysis a comparison could be made to assess the capability to discriminate between normal and malfunctioning devices. The advantage of the proposed test bench is that it could provide a non-contact, non-destructive analysis of the valve under the same working conditions as those upon implantation. The proposed method could furnish a typical "fingerprint" characterizing each valve behavior in repeatable experimental conditions.

The thickness of the tympanic membrane has to be known for the formulation of mathematical ear models. Using a commercial confocal laser scanning microscope we have found that the tympanic membrane has parts thinner than 10 micron. In this study we were forced to excise the tympanic membranes and due the restricted working distance of the microscope objective, we had to flatten the tympanic membrane onto a glass plate. Although we were able to measure thickness in fresh samples, thickness could still have been altered by the preparation procedure. S. Khanna developed over the years a powerful heterodyne interferometer with confocal pinholes in the illumination and observation arms. Thanks to its sectioning capabilities it can measure vibrations of structures embedded within other tissue without the need to expose the structure. While using this equipment in measuring vibrations in the middle ear, the idea grew that the interferometer could also be used to measure thickness, by tracking the carrier level of the interferometer while the laser focus is driven through the membrane. The method looks full of promises as measurements on animals with the tympanic membrane still in its original niche are possible without a prior preparation of the membrane.

In the field of otolaryngology a precise contactless treatment of the bones in the middle ear is eligible. For this reason lasers are investgiated for the use in this field. The main risk during laser surgery in the middle ear (e.g. stapedotomy) is the damage of hair cells in the inner ear due to heat diffusion or high pressure fluctuations. While the temperature problem has been resolved by shortening the pulse durations; the transfer of a recoil momentum due to the ablation process rises as another problem. To measure this momentum, special spring plates were designed as vibration disks for the mounting of the tissue. The probes were exposed to amplified Ti:Sapphire laser pulses with a pulse length of 45 fs and a power density up to 5,6•10¹³ W/cm². The beam of a laser Doppler vibrometer was focused on backside of the plate to monitor its motion. The results were compared to a damage threshold of hair cells in the inner ear calculated by a literature value for the Sound Pressure Level (SPL)-Threshold. The results lead to SPL values below the critical value of 160 dB. Measurements with higher time resolution and high speed photography are used to approve these results.

In this paper a measurement method for the analysis of the structural behavior of heart valves is presented by the use of the thermoelasticity and laser Doppler vibrometry. A special experimental test bench has been realized with the purpose to fix the body of the valve and to excite the parts of remarkable importance from the structural point of view by means of a shaker. The vibrational measurements have been adopted as boundary condition for the FEM simulations and the relative maps in terms of stress have subsequently been validate through the employment of the thermoelasticity.

Vehicle interior acoustics became an important design criterion. Both legal restrictions and the growing demand for comfort, force car manufacturers to optimize the vibro-acoustic behavior of their products. The main source of noise is, of course, the engine, but sometimes some ill-designed cover or other shell structure inside the car resonates and makes unpredicted noise. To avoid this, we must learn the genesis mechanism of such vibrations, having as subject complex 3D shells. The swift development of computer technologies opens the possibility to numerically predict and optimize the vibrations and noises.

The paper describes how with one identical method the surface of a vibrating structure as well as the emitted acoustic sound field in air as well as the internal mechanical stress σ(t) in the vibrating structure can be investigated and visualized. This unique capability opens new possibilities for improving and optimizing the development of effective long-term stable sound transducers with optimized emission characteristics. Furthermore, the method can be used for investigating the internal stress of models of dynamically stressed mechanical structures. The simultaneous visualization of vibrating surfaces, internal stress σ(t) and emitted sound contributes to a better understanding of the behavior of complex dynamically excited structures.

In this work a procedure for the aero-acoustic characterization of air jets was presented. The ability of a laser vibrometer to assess the changes in the optical path induced by local fluctuation of air refraction index was used to calculate the pressure oscillations produced by turbulence. The signal from the laser must be treated in order to extract the required information. From the pseudo velocity, which represents the integral of the refraction index distribution along the laser beam, it is possible to calculate, by a tomographic algorithm, the volumetric distribution of the refraction index at each frequency, and then the pressure oscillation. Each pressure voxel represents a sound source, i.e. monopole, that gives contribution to the Sound Pressure Level in each point of the surrounding. The uncertainty of the procedure was also evaluated.

Ultrasonic pulse propagation along locating antenna and ultrasonic wave radiation efficiency depend on material and shape of antenna. Some errors and mistakes can be made during designing and manufacturing of the main element of ultrasonic location meter. These errors can be detected by testing antenna after production. No additional optical elements can be attached to the usually curved fragile and optically rough sound wave radiating surface. Semiconductor laser short distance home made interferometer was used for pulse propagation investigation. Distance along radius between measurement points was chosen taking into account shift pulse wavelength on the surface. There was a possibility to adjust amplitude during the optimization process and to measure real amplitudes of completed antenna in working conditions. It was found that the pulse amplitude and velocity was decreasing with distance from the center. This result was in accordance with theoretical prediction. Pulse energy is distributed on wider surface and therefore pulse amplitude is decreasing. The edge of antenna is less rigid because of it's shape and velocity of pulse should be smaller than it is near to the center. The shift pulse average velocity should be 1.5 times as high as velocity of ultrasound in surrounding medium. Comparison of velocity of shift pulse propagation on the surface of ultrasonic antenna and velocity of acoustic wave in environment material allowed optimizing thickness and parabolic shape of antennas's body.

The acoustic emission of an ensemble of growing germs of a new phase in elastic medium, the scattering of hypersonic wave by an indicated ensemble and the transition processes initiated by an acoustic pulse were investigated. Two characteristic stages of germ formation-initial and late (stage of coalescention) were considered. The analysis of acoustic emission showed, that the ensemble of growing germs generates acoustic waves which frequencies ω_E are simple connected with the size R of heterogeneities (germs), and the intensity of each spectral component is determined by their concentration n(R). If we direct a laser beam on the sample, the radiation will be dispersed on the hypersonic waves, and the scattering angle will be simple connected the frequency of an acoustic wave and therefore with the sizes of a germ R.

Near-field Acoustic Holography (NAH) is one of the most promising and interesting tool for the investigation of vibro-acoustic problems. This hybrid tool is based on array microphones pressure cross-spectra acquisitions from which the acoustic field on the 3D space can be calculated. The reconstruction procedure involves numerical computations where the effect of many uncertainty sources can be propagated. One of these is the temperature factor: if the vibrating object is undergoing a high temperature gradient, the wavelength of sound propagation will change within the surrounding space. The conventional instruments applying NAH do not take into account this effect since they are based on the hypothesis of constant sound speed along the reconstruction path. In order to appreciate the influence of noteworthy temperature gradients on NAH calculations, an algorithm has been developed for taking into consideration the fluctuation of the sound wavelength. Hence, the results accuracy have been checked by comparing them to the surface velocity measured in the vibrating source by means of Scanning Laser Doppler Vibrometry (SLDV). This research work has been performed within the European Growth Project "ACES" (Optimal Acoustic Equivalent Source Descriptors for Automotive Noise Problems) GRD1-1999-11202.

Measurement of vibration "operating deflection shapes" (ODSs) on cylindrical or conical surfaces is difficult with optical techniques, because of the restricted angle of view. Point measurement transducers such as accelerometers, on the other hand, can provide extensive coverage, but with poor spatial resolution. This paper proposes two techniques using a continuous-scan LDV which can be used to give full area coverage on such components. In the first technique, the structure is mounted on a stand which is oscillated, typically, at 0.3 Hz, over ±180°, to provide a scan in the circumferential direction, with a straight line scan parallel to the axis of rotation. Analysis is identical to that for a rectangular scan, and gives the ODS as a 2D polynomial series. The second technique uses a fixed-point LDV with a continuously-rotating 45° mirror to provide a circumferential scan, the mirror being simultaneously translated, sinusoidally, along the axis to give a scan on the inside of the structure. Analysis is the same as that for a spiral, circular scan on a vibrating disc, and gives the ODS as a Fourier series in the circumferential direction and a polynomial in the axial direction.

The use of Laser Vibrometers incorporating some form of manipulation of the laser beam orientation, typically using two orthogonally aligned mirrors, has become increasingly popular in recent years with considerable attention being given to the operation of such scanning Laser Vibrometers in continuous scanning mode. Here the laser beam orientation is a continuous function of time, making it possible, for example, to track a single point on a moving target such as a rotating bladed disc. A recently derived comprehensive velocity sensitivity model has been developed to incorporate time-dependent beam orientation enabling confident and detailed analysis of data obtained in such measurements. The model predicts the measured velocity for arbitrary mirror scan angles and arbitrary target motion and is shown to be especially valuable in revealing the sources of additional components that occur in continuous scanning and tracking measurements on rotors. The development of the comprehensive velocity sensitivity model and of sophisticated measurement hardware and software has resulted in proposal of the exciting new Synchronized-Scanning Laser Vibrometry technique. Introduced for the first time in this paper, the measurement involves the probe laser beam tracking the rotating structure and simultaneously scanning the region of interest to provide modal data under operating conditions, i.e. during rotation. Such a measurement is inconceivable by any other means and the system that has been created has the potential to provide data of fundamental importance in the design and development of a wide range of devices from hard disk drives to gas turbines.

A fast, low power CMOS sensor for optical tracking is presented. The tracking function is carried out by pointing at the target with a collimated light beam and estimating the position of the back-reflected beam portion impinging on the device. An example of optical tracking sensor is represented by a Position Sensitive Detector (PSD). This work presents a novel architecture of a 2D pixel array for single spot detection and tracking, based on image outline extraction. The prototype device, designed in standard 0.8 μm CMOS technology, consists of an array of 20x20 pixels with a pitch of 70.25 μm and a fill factor of 12%. The photosensitive detector is provided with analogue processing circuitry and digital blocks which allow to extract the spot centroid. Two different multiple threshold working modes are adopted in order to improve the sensor accuracy and frame rate. The light spot position can be estimated in 120 μsec with an accuracy of 0.9 μm, when the sensor is operated with the first mode. The second mode is adopted to improve the frame rate. The chip exhibits a worst case power cosumption of 15 mW @ 5 V and a frame rate up to 3000 frames/s.

This paper begins with a review of the fundamental mechanism by which speckle noise is generated in Laser Vibrometry before describing a new numerical simulation of speckle behavior for prediction of noise level in a real measurement. The simulation data provides real insight into the phase and amplitude modulation of the Doppler signal as a result of speckle changes. The paper also includes experimental data looking at the influence of speckle noise in measurements on rotors with a selection of surface treatments and in scanning and tracking configurations.

Laser Doppler Vibrometry is a well established experimental technique for non-contact measurements of vibrations. With the measurement object fixed in space, 1D or 3D vibration information of single points or of complex measurement grids can be obtained widely independent of the properties of the object. Under operating condition, however, numerous objects, especially car components, are either rotating or moving in space. Therefore a flexible tracking system has been developed for measuring a whole grid of measurement points on arbitrarily moving structures with a focus on rotating objects. The well established software of a commercial Scanning Laser Doppler Vibrometer (SLDV) with all its features like definition of the measurement grid, data acquisition, analysis or data presentation is used to scan the grid on the object in a well-defined starting position. The movement of the actual measurement point is continuously calculated by a separate tracking controller. During a preliminary teaching phase, the tracking algorithm calculates the traces of selected measurement points depending on a position signal of the object. In the measurement phase, the tracking controller obtains the coordinates of the actual measurement point as defined in the starting position from the scanning vibrometer. The trace of this measurement point is calculated from approximate trajectories of the teaching phase and the actual position of the measurement point is then continuously calculated according to the object position. Applications of the system for the measurement of the deflection shape of different rotating fans are presented.

Recently, a mobile coordinate measurement machine consisting of three CCD cameras was expanded with dynamic measurement capabilities. The system is able to track three LEDs in three directions with a maximum sampling frequency of about 1000 Hz. This offers the possibility to use the measurements for dynamic system identification. To this aim, a vibrating structure is equipped with multiple lightweight infrared LEDs and excited by dynamic excitation sources. Transfer functions between force and displacements are estimated from which the modal parameters of the structure can be identified. The benefits of using the camera displacement measurement system is that information down to 0 Hz can be obtained, that mounting LEDs is much easier than installing traditional displacement transducers (LVDTs) and that the coordinates of the measurement points are also available from the measurements. In this paper a dynamic testing study is performed using a scale model of an airplane. Both LEDs and accelerometers are mounted on the structure allowing a comparison between displacement and acceleration transfer function modal analysis results. The main conclusion is that it is possible to successfully identify the modal parameters of the airplane scale model from the displacement measurements in the complete frequency range of the excitation.

In this paper, the authors present a procedure to damping identification of the plate clamped in an extremity and free in the other using measurements of non contact sensors. The procedure is based on computational simulations results of mathematical models obtained through the Finite Element Method (FEM) and experimental procedures based on modal analysis. The experimental data are obtained of two ways: the first using a measurement laser system (Laser Velocity-Transducer Set) and a hammer of impact for excitement of the system of which is obtained frequency response function of the system, while the second using proximity sensors instead of laser, the validation of the numeric models is done through confrontations of computational results and measurements experimental data. The estimation of the system damping matrix is calculated through of the modal matrix of the system. Comparative results of the efficiency of the way of measurement in the estimated of the system damping matrix are presented.

This technique for extracting acceleration-like signals from a laser Doppler vibrometer (LDV) depends on comparing the responses of structures to specific impulsive inputs. What is compared here is the derivative-like response of a sufficiently short pulse to that of a step input. This is derivative-like because the pulse itself consists of an abrupt up-thrust followed shortly by an identical, but inverted down-thrust. The short pulse response emulates the negative numerator of the derivative definition in analog fashion. Certain structures excited by long pulses with equal widely-spaced rising and falling step inputs, respond such that the up and down- thrusts responses are exact inverted copies of each other regardless of the structural modes excited. Adjusting this pulse-width to be much smaller than the period of the highest frequency response component forms this derivative responses. Three validation tests are discussed. A consistency check shows the LDV pulse response is close to that of the finite difference scan of the LDV step response. The next test compares LDV pulse responses relative to differing input pulse-widths. The last test correlates the step input response of a mounted accelerometer on a test fixture to that of the pulse input response of an LDV focused on top. This technique should be helpful in comparing the LDV-to-accelerometer responses in mechanical setups where this derivative character of impulse inputs is valid. Since this comparison encompasses multiple excited modes, one can check or validate device calibrations at these different frequencies. It may be useful in some tests as an analog means of simulating acceleration using the velocity output of a no-mass-load LDV.

A novel signal processing approach is developed in the present study for accurate evaluation of the output frequency responses of nonlinear systems to sinusoidal inputs. Simulation study is conducted, which verifies the effectiveness of the proposed approach. The approach is also applied to analyze the experimental data from dynamic testing of rheological properties of a polymer material. The result shows that the approach has a considerable potential to be used in a wide range of engineering applications.

Examination of advantages and disadvantages of some not commonly used time-frequency representations of vibration signals has been the aim of the paper. The study has been mainly devoted to Wigner-Ville decomposition as well as instantaneous amplitude and frequency. These representations have been examined from the pattern recognition point of view. The Wigner-Ville decomposition was compared with short time Fourier transform taking into account its classification power. In the case of instantaneous amplitude and frequency representation a new method of feature extraction followed by classification using optimal neural classifier has been proposed. Results have been illustrated using a data set of signals measured by a laser vibrometer. They proved that the method proposed in the paper could be used for very fast classification based on vibration signals measured in transient state.

With the development of optical measurement techniques it was possible to obtain vast amounts of data. In vibrometry applications in particular where FRF-matrices with tens of thousands of rows and an equal number of rows are stored, data reduction has become a point of interest. It has long been known that it is possible to reduce (approximate) the measurement data (e.g. mode shapes) by means of a Fourier decomposition. One of the most common techniques for evaluating optical measurement data is by means of a Fourier analysis. It is well known that for periodic and band-limited sequences the Discrete Fourier Transform (DFT) returns the true Fourier coefficients when exactly 1 period (or a multiple) is processed. Leakage will occur when less than 1 period is considered. This gives rise to non-negligible errors, which can be resolved by using a Regressive Discrete Fourier Transform (RDFT), introduced in this article. The measured signal is represented by a model using sines and cosines. The coefficients of those sines and cosines are then estimated on a global scale by means of a frequency domain system identification technique. By making use of the regressive technique proposed in this paper, it is possible to reduce the data in comparison to the classical Fourier decomposition even further by a sizeable factor. In this article the introduced method will be applied in particular to the reduction of data for (1D) laser vibrometer measurements performed on a composite (IPC) beam, as well as on an aluminum plate (2D). The proposed technique will also be validated on both 1D and 2D simulations of varying complexity.

This paper presents special non-linear methods for phase detection for vibration measurements based on laser signals and on test-functions. First are presented mathematical aspects of high-intensity optical pulses (such as the pulse generated by the photonic echo phenomenon), being shown that the only mathematical possibility of simulating such pulses is represented by the use of test-functions (well-known from the mathematical theory of distributions). Then are studied test functions from the generating possibilities point of view, being shown that systems described by differential equations can generate only some functions similar to test-functions, called "practical test-functions." The advantages of using them in filtering and sampling procedures is also presented, and further are studied differential equations of first and second order able to generate such functions. Finally are presented possibilities of using systems described by such differential equations for processing the signal generated by photodetectors when laser signals are received, and filtering possibilities in case of detectors placed in a vibrational environment are shown. Due to the existence of non-linear equations, the output of such filtering systems is very sensitive at the phase of an input alternating component, being recommended to use them for phase detection.

A large-scale survey (~700 m²) of frescos and wall paintings was undertaken in the U.S. Capitol Building in Washington, D.C. to identify regions that may need structural repair due to detachment, delamination, or other defects. The survey encompassed eight pre-selected spaces including: Brumidi's first work at the Capitol building in the House Appropriations Committee room; the Parliamentarian's office; the House Speaker's office; the Senate Reception room; the President's Room; and three areas of the Brumidi Corridors. Roughly 60% of the area surveyed was domed or vaulted ceilings, the rest being walls. Approximately 250 scans were done ranging in size from 1 to 4 m². The typical mesh density was 400 scan points per square meter. A common approach for post-processing time series called Proper Orthogonal Decomposition, or POD, was adapted to frequency-domain data in order to extract the essential features of the structure. We present a POD analysis for one of these panels, pinpointing regions that have experienced severe substructural degradation.

In this paper, we investigate the feasibility of both detecting and localizing inclusions in structures given a knowledge of dynamic surface displacements. Provided with such displacement information, the equations of motion are utilized to estimate local material parameters through inversion, as well as to indicate the locations of inclusions using a novel generalized force mapping technique. Using a finite element code, numerical simulations were carried out for the determination of the normal surface displacements for both steel and mortar rectangular plates subject to monochromatic point actuation. The data is generated for both homogeneous plates and inhomogeneous plates within which a small rectangular inclusion of differing material parameters is present, and three algorithms are applied to the calculated displacement data. The first two are local inversion techniques which provide a spatial map of the elastic modulus normalized by density, while the third technique utilizes the inhomogeneous form of the equations of motion to obtain an induced force distribution caused by the inclusion. It will be demonstrated that the algorithms can both detect and locate inclusions in structures even when the materail parameter difference of the inclusions and the background medium is relatively low.

In recent years, a great effort has been done to improve damage detection techniques in structures by using vibration measurements. This paper presents a case where a non-contact measurement system, a Scanning Laser Doppler Vibrometer, has been used to detect delaminations in a composite material plate. The diagnostic technique is the evolution of a methodology previously approached by the authors. An in-house made software has been produced for data acquisition and vibrometer control. The maps of the detected defects are presented, thus allowing the assessment of the performances of this methodology to detect damages. This analysis permitted to outline the main points to be improved in the future investigations.

Currently, the scanning laser Doppler vibrometer (SLDV) has become a standard laboratory tool for high spatial resolution vibration measurements. Though the quality of the measurement result is very high in well-controlled experiments, there are still some limitations on the application in harsh industrial environments. Firstly, the user interaction of available SLDV systems is too high, requiring trained personnel. But more important, laser drop-out can cause outliers in the measurements when non-treated (and often dark) surfaces are measured. These limitations prevent the real breakthrough of the SLDV in industry, notwithstanding the fact that a high potential exists for the use of the SLDV for quality control. In this article, a procedure will be developed to make the SLDV measurement process fully automatic and more robust. Firstly, an automatic laser calibration and component recognition method -- that is based on newly developed image processing algorithms -- is described. Secondly, a robust singular value decomposition (SVD) is introduced to eliminate laser drop-out from the measurements. The merits of the proposed methodology (measurement automation and robustification) for quality control purposes will be validated on SLDV measurements of a mask of a picture tube.

As it is well known an important application of holographic non-destructive testing (HNDT) is found in the investigation of structural condition of artworks, especially in defect localization, as well as in detection of deformation responses and stress concentration. The detection is realized through the generation of visual interference fringe patterns of low frequencies and the analysis is performed through a qualitative or quantitative assessment of their distribution. In this paper the aim is primarily towards the establishment of the experimental parameters dominating the fringe pattern formation process and their significance on the results obtained along with their inherent limitations in the interpretation procedure. Relevant experimental results obtained using the basic principle of double-exposure holographic interferometry from specifically constructed defects in samples are presented in support of the above goal. It should be underlined that there are fringe pattern similarities in relation to experimental parameters. Finally it is suggested that the most specific the investigating conditions are, the most precise defect characterization is achieved leading to accurate metrology on the artwork.

ESPI and 3D pulsed Digital Holography have been applied to detect inhomogeneities inside a metal cylinder. A shaker was employed to produce a mechanical wave that propagates through the inner structure of the cylinder in such a way that it generates vibrational resonant modes on the cylinder surface. An out of plane ESPI optical sensitive configuration was used to detect vibrational resonant modes. A 3D multi-pulse digital holography system was used to obtain quantitative deformation data of the dynamically moving cylinder. The local decrease in structural stiffness inside the cylinder due to an inhomogeneity produces an asymmetry in the resonant mode shape. Results show that the inhomogeneity produces an asymmetry in its vibrational resonant modes. The method may be reliably used to study and compare data from inside homogeneous and inhomogeneous solid materials.

Accurate phase response information for vibration measurements is becoming more important for a vast range of applications. The use of laser interferometry to perform phase calibration of accelerometers is examined, specifically through the implementation of the sine-approximation method as described in ISO 16063-11. Phase calibration of the components of a measurement setup is discussed, considering the effects and influence that each component has on the phase calibration of accelerometers. The accuracy obtainable for phase calibration of accelerometers is evaluated by means of comparison measurements between two National Metrology Institutes. In conclusion, the uncertainty contributors as presented inthe ISO 16063-11 with respect to phase calibration are reported on.

Two methods based upon the digitized modulation phase of a single channel laser interference photo signal are derived to compute the displacement amplitude of an accelerometer. One is an analytical method that can easily calculate the displacement amplitude of an accelerometer from digitized modulation phase by simple algebraic equations as long as these modulation phases are in the same 2π argument and the signal is noise free. The other method is using least squares to curve fit the digitized modulation phases of a laser interference signal with noise. The advantages of these methods are that, without changing any experimental setup, one can use the existing primary calibration laser interferometer system that follows the ISO 16063-11 and the phase mismatch and amplitude mismatch of a two-beam laser system can be avoided. From frequency range 2 Hz to 10000 Hz and displacement amplitude range 0.02 μm to 10000 μm, the computer simulated results show that the relative errors of curve fitted displacement amplitude and starting time phase angle are insensitive to different noise levels and the relative error of starting time phase angle is much smaller than that of displacement amplitude.

Bessel function methods are used on high-frequency vibration calibration. In this paper, a general principle, devices, methods and uncertainty evaluations will be introduced. There are four methods based on Bessel function, which include J₀ minimum-point method, J₁ minimum-point method, J₁ ratio method and J₁/J₂ ratio method. About this calibration system, the frequency range is 2 ~ 50) kHz and the displacement range is (0.002~0.2) μm. At the same time, two important things will be described, one is a frequency-adjustable piezoelectricity vibrator which is good for high-frequency vibration calibration on account of almost no equilibrium excursion, and the other is double-holes method used in evaluating the linearity of laser interferometer which is important for calibration.

The random and bias errors of Doppler spectral shift measurements, correlation measurements and zero crossing techniques are discussed. It is shown that spectral shift measurement technique has advantage over other techniques in low signal-to-noise ratio region, whereas zero crossing technique based on analysis of probability density ensures lower random and bias errors at high enough SNR. The correlation technique has relatively low random error but shows considerable bias error in the region of low and moderate SNR when information about Doppler frequency is obtained from first zero of correlation function.

In 2001 SPEKTRA designed and installed the first calibration system for primary calibration by laser interferometry based on Part 11 of the new ISO standard ISO 16063. The investigations and measurements presented at the AIVELA Conference in 2002 focused on the conformity to ISO standard and the basic function of calibrating single ended and back-to-back reference standard sensors. After two systems have been running for 3 years both at the SPEKTRA calibration laboratory and at the laboratory of our reference customer, investigations focus more and more on the measurement uncertainty of the entire calibration procedure.

Laser-Doppler Vibrometry has been proven to be an accurate method to measure vibration amplitudes with a known error budget. Therefore, vibrometer technique is used to realize primary standards in vibration-amplitude measurements at national metrology institutes (e.g. Physikalisch Technische Bundesanstalt PTB in Germany). However, additional error sources emerge for vibrometer measurements at microscopic structures. This paper discusses two error sources that can be neglected for usual macroscopic testing but can become important for microscopic measurements.

The tools of the optical measurement of deformation are increasingly used to characterize the mechanical as well as thermal properties of MEMS or microcomponents. Both, the residual stress state and thermally induced deformation can be analyzed by applying of laser Doppler vibrometry or by several variants of laser based optical methods usually using photoelectric detection. In the paper the application of techniques for the dynamic movement and vibrations measurement of microelements and thin silicon membranes is reported. Using the laser Doppler vibrometry is discussed to evaluate the stress state of membrane-like microbridges, to obtain frequency characteristic and impact response of microcantilever and to measure the resonances of thin silicon membranes. Based on observation of time-averaged light intensity pattern at focal plane, newly developed method of autocollimation is demonstrated with the possibility to visualize the vibration mode shapes of membranes. Beside this, also the experience with laser deflection detecting by position sensitive detector technique is described.

The aim of this research is to evaluate the effect of the interaction between the Laser Doppler Vibrometer and the sample in the microscale. In particular the attention will be focused in the numerical and experimental evaluation of the heating effect due to the laser beam power. The consequent temperature variation will be related to the measurement results in terms of resonance frequencies and vibrational modes determination.

In many structural vibration control applications, strain sensors play a key role in the design and implementation of the vibration controller. Different types of sensors are commercially available, among which is the poled polyvinylidene difluoride (PVDF), an attractive sensor for large bandwidths and low costs. Despite such attractive features, PVDF-based sensors have limited use due to their low efficiency (mechanical energy to electrical energy conversion factor). To remedy this, nanocrystals and nanostructures have been recently cited as candidate materials that can be engineered to exhibit enhanced or entirely new properties for use in different applications. Particularly, carbon nanotubes (CNTs) have raised considerable interest in the scientific community due to their size and wide range of outstanding material properties. Given the moduli and strength values of CNTs, they are ideal filler materials for high performance (polymer) composite materials with unbeatable modulus-to-weight and strength-to-weight ratios -- the attributes that are essential for structural vibration control of a wide variety of industrial equipment and systems. Along this line of reasoning, this paper undertakes the development and implementation of a novel sensor paradigm based on proper fusion of CNTs with PVDF materials.

Based on Patent application DE 198 22 125.8-52, we present a technical description of a new temporal and spatial high resolution anemometer for gas and liquid flows. The measurement principle is based on the technique of an atomic force microscope where microstructured cantilevers are used to detect extreme samll forces. We show the sensor as a small compact unit and present first measurements and characterizations.

A miniaturized system based on digital holographic inteferometry has been developed and used for the measurement of dynamical deformations, where measurements need to be performed at "hidden" surfaces or inside more or less closed objects. A Q-switched pulsed laser is used. Two digital holograms of the test object, corresponding to the two laser pulses, are captured at separate video frames of the CCD-camera, transferred in a frame grabber and further processed in a PC. If during the interval between the two laser pulses (usually in the range of 5 - 600 μs) the object undergoes a vibration, a fringe pattern will result from the difference between the two holograms. This fringe pattern has the information needed to quantitatively evaluate the vibration.

One of the most interesting and useful applications of shearographic interferometry is the detection, visualization and measurement of the mechanical vibration of opaque objects. Until now the time-average shearography is a qualitative interferometric method for determining the oscillating loadings. The detected gradient of the deformation can be determined by changing the shearing distance. The fringes of the moving object are often faded and become clearer by filtering with FFT and against an uniform background intensity. The fringes formed in time-average shearography of sinusoidal motions have an irradiance described by the Bessel function J₀². Quantitative interpretation of the shearogram requires a more precise analysis. Such a technique for extending or decreasing the sensitivity of vibration measurements and for determining the relative phase of vibration across the object surface is the stroboscopic illumination. Stroboscopic shearographic interferometry is a technique which compensates the deficiencies of time-average shearography at the expense of some increase in experimental complexity. However more complex is the recording of stroboscopic shearograms by using two pulses from a double-pulse laser.

The objective of this paper is the description of the Projected Pattern Correlation method for measuring surface velocities and to present results of a feasibility study. Similar to the Moire technique the local surface velocities of a large area are determined simultaneously, which replace a time consuming point wise scanning as it is necessary in e.g. Laser Doppler Vibrometry. Furthermore, the dynamics of non-periodic processes can be resolved temporally and spatially. In difference to the Moire or grid projection techniques the evaluation step is fast (real-time measurements are possible) more robust and provides a high spatial resolution. The measurement precision is assessed using a simple test arrangement. Vibration measurements are performed on a satellite model structure and a honeycomb sandwich plate.

Recently special attention has been given to the problem of the holographic registration of images and information with the purpose of a solution of various scientific and technical problems. It is well known that carbazol containing polymers, for example, poli-N-carbazolylalcoxymethacrylate (poli-CAM), co-polymers CAM, polyepoxypropilcarbazol (PEPC), have been recommended very well as organic photoconductors, especially in the field of the creation of mediums for information registration, including holograms. The photochemical method of image recording of carbazole-containing polymers films attribute to famous methods of image recording. Our research is aimed at finding of a new photopolymer compositions sensitive in the visible and infrared spectra. We have studied a photopolymer materials, which are doped by amorphous semiconductors. We have used As₂S₃, S, Se, GeSe as additives of the amorphous semiconductor, and PEPC, PVA, BMA as main polymers. These photopolymer films have been prepared by pouring from solutions. The photopolymer films have been applied both on transparent (polyethylenethereftalat) films and rigid substrates of optical glass. The samples have been obtained with the thickness in the range of 2 μm to 30 μm. The contents of different amorphous semiconductors have beem maintained within the limit of 5 - 40 wt.% of the photopolymer. The variation of the concentration of each component and the transmission spectra have been studied for all the photopolymer films. The experimental measurements of its transmission spectra are evaluated in conjunction with its application for optical holographic recording in visible and infrared ranges. The optical transmission spectra have been measured in optical region from 0.8 μm to 3.0 μm by spectrum-photometer SPECORD 61 NIR and in region from 0.4 μm to 0.8 μm by spectrum-photometer SPECORD UV VIS.

This paper describes the application of twin-pulsed 3D digital holography to the measurement of the dynamic deformation of a disc while it rotates. Object rotation produces interferometric fringes that are related to deformations for instance, stress due to the centrifugal forces, out-to plane vibrations, and the object angular displacement. Furthermore an unbalanced disc that rotates may present a characteristic vibration amplitude pattern at a specific frequency. An optical arrangement that illuminates, with a twin pulsed laser, from three different positions the object was used to recover the x, y and z displacement components in a rotating object. The technique is able to distinguish the disc rotation from the displacement along the x-y plane and the out-of-plane z displacement. Two laser pulses are fired in order to take two digital holgrams with a time separation of 20 μs. This is done for each of the three object illumination positions. Triads of twin-pulsed digital holograms taken at different times during object rotation are processed independently, and their optical phase maps retrieved by the conventional Fourier transform method together with the combination of data from the three illumination positions. The phase term related to the deformation is found experimentally where the intrinsic sensitivity vector is related to the rotation via the vector cross product, forming parallel fringes. To recover the rotation and deformation data the unwrapped phase maps were used as 'tilt' phase planes an all three sensitivity vectors in order to recover the in-plane, and out-to plane displacements. An interpolation algorithm was developed to correlate the time depending phase maps, leading to obtain object vibration frequency data. Experimental results are presented, showing in particular that the rotating object has an unbalancing due to the detected vibration frequency.

A problem on the interaction between coherent radiation and a dynamic medium under deformation is studied on the basis of a model of a three-dimensional diffuser. An expression has been obtained for the function of mutual coherence of the intensity of scattered radiation at two spatial-temporal points of free space and the region of the image of a thin object. Some mechanic-optic effects associated with changes, displacements and interferences of speckle fields resulting from the theory are considered. Results of experiments conducted to verify the theory are given, and new coherent-optic methods of measurement and testing are substantiated. Particularly, consideration is given to speckle displacement along the Z-axis in the deformation of a body in the X- and Y-directions, a method for studying rotary motions of surface areas, a method for revealing pre-fracture regions, a method for determining strains and nondestructive testing based on a new approach to the registration of interference fringe patterns.

Two examples of operation of extended laser-based measuring networks to control the effects of mining-induced microseismicity on building structures are presented in the paper. The networks functioning in various urban development conditions are constructed with the use of laser vibration sensors, accelerometers and deformation measuring gauges. The necessary details on sensors construction, laboratory tests on their metrological characteristics and structure of the entire system are given. Remote data transmission and purpose-designed computer software for long-term and momentary events enable to prepare rapidly necessary information about the current condition of the controlled buildings, and take necessary preventative actions in case of need. Discussed is the experience from operation of two such networks in two locations in Poland, in copper ore- and coal mining areas.

The research results of autodyne signal formed under reflection of semiconductor laser radiation from vibrating reflector have been presented. The influence of feedback coefficient and distance to vibrating object on an autodyne signal form has been shown. The method of reverse problem solution in autodyne interferometry of nonharmonical vibrations has been described. The suggested method allows us to restore the amplitude and form of mechanical vibrations for autodyne system developed for interference system separated from the light source. A method of amplitude determination of mechanical vibrations from the spectrum of autodyne signal of semiconductor laser is described. The relation between the vibration amplitude of an object and the frequency of spectral component with the maximum amplitude in the spectrum of the autodyne signal has been obtained. The least-squares method was used to obtain the approximation coefficient. Measurements of vibration of micron amplitude of piezoelectric plate were carried out with the help of a semiconductor laser autodyne system. A method for the quantitative monitoring of nanometer vibrations based on the autodyne detection effect in a semiconductor laser has been developed. It is shown that the semiconductor laser autodyne can be used for measuring vibration amplitudes in the range from one nanometer to 10 μm in the frequency band from a few hertz to several hundred megahertz. With the aid of a lock-in amplifier, the lower threshold of measured vibration amplitudes has been reduced to angstrom.

In this paper we analyzed and calculated the temperature distributions and deformation fields in the cross section of optical fiber under periodical photo thermal excitation applied to one side of cylindrical surface. This calculations were made to optimize the exposure and to minimize energy, needed for realization of this class of sensors. The main difference from other papers is the non-symmetrical heating for initiating vibrations.

A laser microvibrations transducer based on diffraction of a laser beam on a system of two diffraction gratings is described. The transducer has an experimental threshold of detection of 0.3A°, a dynamic range of about 10 μm. It contains no expensive elements (simple glass stepped gratings) and it is easy to implement and align. Furthermore it is self-calibrating. It can be successfully used for nuclear explosion monitoring and can be useful tool in industrial machinery, transport equipment vibration testing and control and seismic monitoring.

We report the use of photo-electromotive-force effect in a speckled pattern of light onto a photorefractive Bi₁₂TiO₂₀ crystal to measure the amplitude of transverse vibrations. Our theoretical model shows that, for vibrations much faster than the photorefractive response time, the photo-emf signal exhibits a maximum at a characteristic vibration amplitude value that may be used to calibrate the photo-emf sensor.

A signal processing method for identifying the input/output behavior of accelerometers is proposed. The method includes data preprocessing applied to interferometrically measured displacement signals and to electrical responses of the accelerometer. The identification procedure itself uses a prediction error approach based on a second order transfer function model. The transfer function of the accelerometer parameterized by gain factor, damping constant and resonant frequency is fitted to the input/output signals utilizing a nonlinear optimization procedure. The method was tested by application to calibration measurement of high shock intensities. The model shows a good performance in describing the output data of the accelerometer. The parameter estimates are characterized by small measurement uncertainties. Hence, the method can be recommended for application in the calibration of accelerometers with high shock intensities. Furthermore, the dynamic model identified describes the accelerometer's input/output behavior for both stationary and transient accelerations allowing accurate measurements of mechanical vibrations and shocks.

A heterodyne laser interferometer and a PXI bus instrument make a primary acceleration calibration system. The modified heterodyne laser interferometer has a frequency stabilized laser and a high frequency accuracy Bragg cell. The system is capable of vibration (both sinusoidal and random) and shock calibration. This paper introduces the principle of the system. An accelerometer is calibrated by this system using different exciting signals include sinusoidal, random and half-sin. It shows the system is flexible in primary vibration and shock calibration and high accuracy will be attainable.

Electrodynamic vibration exciters are widely used for different purposes. One of their important applications is usage as a vibration generating chain in absolute calibrations of vibration pick-ups. Main requirements for the vibration-generating devices are described in relevant ISO standard. These requirements are the total harmonic distortion of the acceleration, transverse, bending and rocking motion, hum and noise level, and the acceleration amplitude stability. The bending, rocking and transverse accelerations are the properties that belonging entirely to the vibration exciter. Contribution of these effects to the overall calibration uncertainty is not as small as to be assumed negligible. Investigation of the motional behavior of some of the commercial electrodynamic exciters by self-mixing interferometry has been carried out at Turkish National Metrology Institute (UME). Interferometer in configuration of the external cavity diodes laser (ECDL) constructed at UME was used for the characterization of the exciters' surface displacement in the medium frequency range.

In contrast to the fact that a huge class of industrial force and torque measurement applications are of dynamic type, the standard calibration methods for the facilitated transducers are still of static type. The presented paper gives an introduction to recent developments at the Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, towards new dynamic calibration methods for force and torque. In addition to the already established sinusoidal force calibration, two new facilities have been developed over the last three years which are concerned with the generation of impact forces and periodic torque respectively. For the primary dynamic force and torque calibration facilities the preferred way to provide traceability is the measurement of the motion of an accelerated mass or mass distribution. The means of measurement for primary calibration therefore are laser-Doppler-interferometers (LDI), which are utilized in very special ways.

Homodyne and heterodyne laser interferometers can be used for dynamic force calibration and for acceleration measurement with sinusoidal and with shock excitation. The characterisics of both types of interferometers in acceleration measurement are compared in this paper. The data acquisition system comprises a four channels ADC card and a digital multimeter to sample the interferometer and force transducer or acccelerometer signals synchronously. The nonlinearity effects of homodyne and heterodyne interferometers in acceleration measurement are analyzed. A transducer is calibrated using both interferometers and good accordance is demonstrated.