In-plane Vibration Measurements Research Articles

High-resolution electronic interferometry for the measurement of in-plane vibration

This study proposes an algorithm based on the standard deviation in the temporal domain to remove influences from background noise and ambient disturbance and enhance the quality of images obtained using interferometric technology. From measurements of the first ten in-plane resonant frequencies and mode shapes of vibrating zirconate titanate (PZT) laminates, we investigated the resonant characteristics in both the U and V directions. The resulting interference fringes were used to quantify the vibration amplitude of PZT plates on a submicron scale. The resonant frequencies obtained using the proposed method are in excellent agreement with those obtained using the finite element method and an impedance analyzer.

Noncontact 2-D In-Plane Speckle Velocimeter

In this paper, the authors present a noncontact 2-D speckle velocimeter, which is realized by means of a compact setup and based on an improved binary correlation algorithm for image processing. Starting from the results obtained in our previous work, where we demonstrated the feasibility of the method for the assessment of the surface velocity for one direction, we have extended the study to a 2-D velocity and displacement sensor by overcoming the previously encountered limits. In addition, the configuration is further simplified by introducing a low-coherence source and a simpler electronic circuit. Sensor performance is compared with that measured using a triangulation laser sensor. The main advantages of the proposed sensor, as compared with those of the traditional velocimeters, are the simplicity of the optical setup, the easily controlled device, and the small dimension of the sensor. The velocity of frame acquisition (15.6 frames/s) is the principal limiting factor of the sensor bandwidth (BW = 3.5 Hz). Such a noncontact optical sensor is suitable for small 2-D in-plane vibration measurements and allows one to overcome the limits of the classical Doppler velocimeters affected by speckle noise in this range of displacement.

２開口法レーザスペックル干渉計による面内振動の実時間測定

This paper describes the real-time measurement of in-plane vibration using a laser speckle interferometer with the double-aperture method. To detect the in-plane vibration in real-time, a new data processing system with an analog electronic circuit for calculating Fourier coefficients is proposed. The phase angle of the frequency component of interference fringes, which corresponds to the in-plane displacement of a target irradiated by a laser, is directly detected. The measurement system composed of the proposed data processing system and the laser speckle interferometer was applied to measure the in-plane vibration of a target excited by a piezoelectric actuator; the vibration displacement of about 5μm was detected with a sampling frequency of 470Hz and within a measuring error of ±0.5μm.

２開口法レーザスペックル干渉計による面内振動の測定

This paper describes measurement of in-plane vibration using a laser speckle interferometer with double-aperture method. A new optical system, which transforms interference fringes in a speckle into a line image on a CCD linear image sensor with an additional cylindrical lens, was proposed. From an experiment to measure static displacement, it was revealed that the cylindrical lens acted to detect fringes two-dimensionally and to average the distribution of optical intensity as same as.scanning measurement and that the measuring accuracy could be improved by decreasing the influence of phase variation in the fringes. The interferometer was applied to measure the flexural vibration of a cantilever as an example, and the vibration displacement could be measured with 1.95kHz of sampling frequency and with 0.5μm of measuring error.

Real-time in-plane vibration measurements by speckle interferometry with the aid of liquid crystal light valve

Real-time measurements of in-plane vibrations by speckle interferometry, which employs a liquid crystal light valve to record speckle patterns, is experimentally studied to be feasible in practice, and preliminary results are also shown.

Optical Heterodyne Measurement of In-Plane Vibrations

A new method of in-plane vibration measurement is possible by using an optical heterodyne technique which detects the frequency shift of light reflected from a point in motion. If a point in a vibrating surface is illuminated with two laser beams whose light frequencies are slightly shifted from each other in the direction symmetrical with respect to the normal of the surface and the intensity at the point is measured with a photomultiplier through an optical system, the output signal of a limiter-discriminator connected to the terminal of the photomultiplier has an amplitude proportional to the frequency-amplitude product of in-plane vibration. By using these principles, a prototype instrument for the measurement of in-plane vibration is constructed and a vibration amplitude of 10 Å at 20 kHz is measured in real time together with its direction.

Optical heterodyne measurement of in-plane vibrations

An optical heterodyne technique which detects the frequency shift of light reflected from a point in motion can be successfully used for in-plane vibration measurements. Principles and results of preliminary experiments are described.