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.

Ultrahigh sensitivity laser Doppler velocimetry with a microchip solid-state laser.

Abstract: Highly sensitive laser Doppler velocimetry featuring the simultaneous measurement of light-scattering objects moving at different velocities and vibration sensing based on Doppler-shifted light-injectioninduced intensity modulation in an externally pumped microchip solid-state laser is demonstrated.

Frequency determination of visible laser light by interferometric comparison with upconverted CO(2) laser radiation.

Abstract: A servocontrolled 1-m plane-parallel Fabry-Perot interferometer has been developed at NPL for the precise intercomparison of laser wavelengths. This instrument has been used to measure the wavelength ratio of a 679-nm radiation and that from a 633-nm iodine-stabilized He–Ne laser, achieving an accuracy of 2.9 parts in 1011. The 679-nm light was derived from a stabilized CO2 laser radiation by upconversion, and the wavelength of this 9.3-μm laser radiation can be calculated from the visible wavelength result. Frequency measurements on the same CO2 laser radiation have already been made in this laboratory, so that the experiment reported here leads to a precise value for the speed of light in vacuum and to the value of 473, 612, 380.5 ± 0.3 MHz for the absolute frequency of the visible radiation from a He–Ne laser stabilized to component d of127I2.

Multi-point vibrometer based on high-speed digital in-line holography

Abstract: This paper describes a digital holographic setup based on in-line holography and a high-speed recording to get a multipoint vibrometer. The use of a high-speed sensor leads to specificities that enable the in-line configuration to be used. The case of transient vibrations is investigated through a full simulation of the holographic process. The simulation shows that the first instants are critical since distortion may occur, resulting in errors in the phase measurement. Experimental results are provided by exciting an aluminum beam with a transient signal. A comparison with the velocity measured by a pointwise vibrometer is provided. Frequency response functions are extracted and the experimental results confirm the ability of the method to provide full-field contactless measurements at the high-speed time scale evolution of the vibration.

Laser operations on a workpiece with uneven surface - where distances between workpiece and laser are measured during intervals between working pulses

Abstract: The method comprises (a) relative motion taking place between the workpiece and the first laser; (b) determining the distance between the first laser and the workpiece by an optical sensor between two laser pulses; (c) comparing the measured distance with a required value; (d) and setting the distance equal to the required value. The appts. includes means for producing horizontal relative motion betwee the workpiece and the first laser, an optical distance measuring sensor, a control system for distance adjustment, and means for phase coupling between the optical sensor and the first laser. Pref. a pulsed second laser and a position-sensitive photodetector are used for distance measurement, with the pulse frequencies of the first and second laser being the same. The lasers are synchronized with a phase shift by means of a lock-in circuit. The second laser is coupled into the beam path of the first laser by means of a mirror. The distance measurement is based on a triangulation procedure, or alternatively a cutting process is utilised. USE/ADVANTAGE - In laser cutting, boring and welding technologies, for example. It enables distances on irregular and steeply curved surfaces to be measured reliably and with a high degree of accuracy.