Topic
Laser Doppler vibrometer
About: Laser Doppler vibrometer is a research topic. Over the lifetime, 6319 publications have been published within this topic receiving 76068 citations.
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TL;DR: In this article, a commercial laser vibrometer, designed for vibration/modal analysis, can be used for crack detection in metallic structures, which involves a simple fatigue test in order to initiate and grow a crack.
Abstract: Guided ultrasonic waves have shown great potential for structural health monitoring. Various types of transducer can be used for actuating and sensing of these waves. This includes non-contact approaches such as optical/laser techniques. Classical laser methods usually involve high energy interferometers. The paper demonstrates that a commercial laser vibrometer, designed for vibration/modal analysis, can be used for crack detection in metallic structures. The study involves a simple fatigue test in order to initiate and grow a crack. Lamb waves generated by one bonded piezoceramic transducer were sensed using a multi-point scanning laser vibrometer. The results demonstrate the potential of laser vibrometry for simple, rapid and robust detection of fatigue cracks in metallic structures.
220 citations
TL;DR: A review of recent experimental and theoretical results concerning laser diode self-mixing velocimetry is presented, showing that this technique can be deployed to measure velocity and vibration of solid targets with an extremely simple optical setup.
Abstract: A review of recent experimental and theoretical results concerning laser diode self-mixing velocimetry is presented, showing that this technique can be deployed to measure velocity and vibration of solid targets with an extremely simple optical setup. This technique reduces optical alignment problems and achieves results comparable to those obtained by the conventional laser Doppler velocimetry (LDV) approach. It is demonstrated that the self-mixing signal can be processed to recover the target velocity and vibration by applying the same analysis method used for LDV. An optimal signal processing method is then proposed to recover the target velocity with good accuracy, also in the presence of relevant speckle disturbance. Application to the measurement of sub-micron vibrations is also demonstrated, using a self-mixing vibrometer instrument capable of 5-nm accuracy. As an example, the characterization of response and hysteresis of piezoceramic transducers (PZTs) is carried out. These results illustrate the effectiveness of the self-mixing technique in the field of laser velocimetry, opening the way to new applications where compactness and low cost of the measuring apparatus are essential.
207 citations
TL;DR: In this article, the problem of obtaining single-frequency output from a long laser is considered, and two methods are investigated experimentally, one using an external filter to select one of a number of oscillating modes, and the second one suppressing internally the unwanted resonances so that the laser oscillation can only take place at a single frequency.
Abstract: The problem of obtaining single-frequency output from a long laser is considered, and two methods are investigated experimentally. The first method consists of using an external filter to select one of a number of oscillating modes. The second method consists of suppressing internally the unwanted resonances so that the laser oscillation can only take place at a single frequency. It is shown that with the second method one can in many cases obtain greater power, and experiments are reported in which single-frequency output power of 15 mW was obtained from a 6328 A He-Ne laser, A simple feedback circuit is described for stabilizing the frequency of the laser oscillation.
199 citations
TL;DR: The design and performance of a simple, multifunction 1.55-mum continuous-wave and frequency-modulated cw coherent laser radar system with an output power of 1 W is presented and aerosol measurements indicate the potential to use single-particle detection for wind measurements with enhanced sensitivity.
Abstract: The design and performance of a simple, multifunction 1.55-mum continuous-wave (cw) and frequency-modulated cw coherent laser radar system with an output power of 1 W is presented. The system is based on a semiconductor laser source plus an erbium-doped fiber amplifier, a polarization-independent fiber-optic circulator used as the transmit-receive switch, and digital signal processing. The system is shown to be able to perform wind-speed measurements even in clear atmospheric conditions when the visibility exceeds 40 km. The aerosol measurements indicate the potential to use single-particle detection for wind measurements with enhanced sensitivity. The system can perform range and line-of-sight velocity measurements of hard targets at ranges of the order of several kilometers with a range accuracy of a few meters and a velocity accuracy of 0.1 m/s by use of triangular-wave frequency modulation with compensation of the frequency-modulation response of the semiconductor laser. The system also demonstrates a capability for vibration sensing.
187 citations
TL;DR: In this article, a 3 mm ×3 mm ×0.003 ǫmm piezoelectric membrane acoustic device, which works as a microphone and a microspeaker, is presented.
Abstract: This paper reports on a 3 mm ×3 mm ×0.003 mm piezoelectric membrane acoustic device, which works as a microphone and a microspeaker. It has a 0.5 μm thick zinc oxide (ZnO) piezoelectric thin film on a 1.5 μm thick low-stress silicon nitride membrane, made of LPCVD. The maximum deflection in the center of membrane, using laser Doppler vibrometer (LDV), is 1 μm at 7.3 kHz with input drive 15 V0-P (zero-peak). The output sound pressure level (SPL) of microspeaker is 76.3 dB SPL at 7.3 kHz, and 83.1 dB SPL at 13.3 kHz with input drive 15 V0-P. The distance between the reference microphone and piezoelectric microspeaker is 1 cm. The sensitivity of the microphone is 0.51 mV/Pa at 7.3 kHz with noise level of 18 dB SPL.
184 citations