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 paper, a noncontact laser ultrasonic wavefield imaging technique was proposed to automatically detect and visualize hidden delamination and debonding in composite structures, which can visualize damage with high spatial resolution without any baseline data.
171 citations
Patent•
05 Mar 1996
TL;DR: In this article, the primary laser signals can then be recombined to produce a laser output having a power level greater than the predetermined power level of the primary signal, which can be controllably modulated such that the resulting laser output has a predetermined phase profile and relatively high beam qualities.
Abstract: The fiber optic laser system and associated lasing method amplifies and divides a primary laser signal into a plurality of secondary laser signals. The fiber optic laser system includes a distribution means, such as a distribution module, for dividing a primary laser signal, generated by a master oscillator into a number of secondary laser signals. The distribution module can include amplification means, such as an optical fiber amplifier, for amplifying the primary laser signal and a signal power splitter for dividing the amplified primary laser signal into a number of secondary laser signals. The secondary laser signals can then be further amplified, such as by a power amplification module including another optical fiber amplifier. The secondary laser signals can be recombined to produce a laser output having a power level greater than the predetermined power level of the primary laser signal. During the process of combining the secondary laser signals, the secondary laser signals can be collimated and the relative phases of the secondary laser signals can be controllably modulated such that the resulting laser output has a predetermined phase profile and relatively high beam qualities.
166 citations
TL;DR: In this article, the hydrogen storage capacity of a small amount of carbon nanotubes (CNTs) mounted on an ultrathin resonator by a manipulator is measured from the resonant frequency change.
Abstract: Ultrathin single-crystalline silicon cantilevers with a thickness of 170 nm as a resonating sensor are applied to mass sensing. The hydrogen storage capacity of a small amount of carbon nanotubes (CNTs), which were mounted on an ultrathin resonator by a manipulator, is measured from the resonant frequency change. The resonator is annealed in ultrahigh vacuum to clean the surface and increase the quality factor, and exposed to oxygen gas to oxidize the surface for long-term stability. The resonator can be electrostatically actuated, and the vibration is measured by a laser Doppler vibrometer in ultrahigh vacuum. The mass of the CNTs is determined by the difference of resonant frequencies before and after mounting the CNTs, and the hydrogen storage capacity is determined from the frequency change after exposure to high-pressure hydrogen as well. The obtained hydrogen storage capacitance is 1.6%–6.0%. The available mass resolution and the achieved stability of the resonance of the 170-nm-thick resonator are below 10−18 g and 5 Hz/days, respectively.
158 citations
TL;DR: In this article, a He-Ne gas laser was used as a simple infrared interferometer for measuring electron densities in an argon plasma produced by a pulsed high-current gas discharge.
Abstract: A He-Ne gas laser is used as a simple infrared interferometer for measuring electron densities. The optical cavity of the laser corresponds to the reference arm of conventional interferometers. Interference occurs if the radiation from the laser is reflected back into the laser by an external mirror. The system was used to measure the electron density in an argon plasma produced by a pulsed high-current gas discharge. (C.E.S.)
157 citations
TL;DR: In this paper, the authors presented an automated crack visualization technique using ultrasonic wavefield images obtained by a complete noncontact laser scanning system by integrating and synchronizing a Q-switched Nd:YAG laser for ultrasonic generation, a laser Doppler vibrometer and galvanometers for scanning.
Abstract: This paper presents an automated crack visualization technique using ultrasonic wavefield images obtained by a complete noncontact laser scanning system. First, the complete noncontact laser scanning system is built by integrating and synchronizing a Q-switched Nd:YAG laser for ultrasonic generation, a laser Doppler vibrometer for ultrasonic measurement and galvanometers for scanning. Then, four different laser scanning schemes are compared to find the most effective and practical ultrasonic scanning strategy for the presented application. Second, a novel image processing technique is developed to isolate and visualize crack-induced standing wave energy from the constructed ultrasonic propagation images. Finally, the effectiveness of the proposed laser ultrasonic scanning system and imaging processing technique is experimentally verified using ultrasonic scanning images obtained from an aluminum plate. The test results confirmed that a hidden notch invisible from the scanned surface was successfully detected and visualized, while no false positive alarm was triggered for an intact specimen.
155 citations