Showing papers on "Laser Doppler vibrometer published in 1969"
42 citations
31 citations
26 citations
TL;DR: In this paper, a non-contacting optical velocity sensing method for extended moving surfaces is described. But the method is based on an optical heterodyne measurement of the difference between two Doppler shifts which are produced in the light scattered through two different angles by the moving surface.
Abstract: Observed signal characteristics and measurement accuracy are described for a recently developed noncontacting optical velocity sensing method as applied to extended moving surfaces. This method is based on an optical heterodyne measurement of the difference between two Doppler shifts which are produced in the light scattered through two different angles by the moving surface. It provides convenient measurements of velocity components tangent to extended surfaces that are optically rough. Absolute accuracies to at least 0.1%, and relative accuracies to 0.04% are reported.
24 citations
Patent•
22 Apr 1969
TL;DR: In this article, the authors described a laser Doppler velicometer for measuring mean velocity and turbulence of fluid flow and used it to measure the mean velocity of fluid flows.
Abstract: Describing laser Doppler velicometer for measuring mean velocity and turbulence of fluid flow
19 citations
Patent•
18 Aug 1969
TL;DR: In this article, two beat frequencies due to doppler measurement of the velocity component of a moving object are produced and the difference in their frequencies compared to determine the direction of object movement along the path of a velocity component.
Abstract: Two beat frequencies due to doppler measurement of the velocity component of a moving object are produced and the difference in their frequencies compared to determine the direction of object movement along the path of the velocity component. One beat frequency is provided by producing first and second radiant energy energy fields whose frequency difference is a function of the sign of the velocity component. The other beat frequency is provided by periodically shifting the phase of one of the radiant energy fields variably with respect to time. The radiant energy fields are produced by a laser device and the phase shift is effected by applying a sawtooth charging voltage to a Pockels cell interposed in the path of one of the laser beams.
15 citations
TL;DR: In this paper, the frequency of one axial mode of a three-mode He/Ne laser can be tuned independently from the other modes if a third mirror is added to the usual two laser mirrors.
Abstract: The frequency of one axial mode of a three-mode He/Ne laser can be tuned independently from the other modes if a third mirror is added to the usual two laser mirrors. Provided the adjustment is correct, the frequency shift is proportional to a change of the optical path length between the third mirror and the neighboring laser mirror. By observing the beat frequency of the laser, measurements of optical path variations down to 10-5A are possible.
14 citations
TL;DR: In this paper, the use of a low-power gas laser as a radiation source for an optical Doppler radar is described, where the laser beam is focused on to a moving target and the light bach-scattered from the target is photo-mixed with a reference signal to give the doppler difference frequency.
8 citations
TL;DR: The low-frequency homodyne spectrum of the argon laser is known to contain a noise spectrum due to mode interactions, thus limiting the laser's use for low frequency Doppler shift measurements as mentioned in this paper.
Abstract: The low-frequency homodyne spectrum of the argon laser is known to contain a noise spectrum due to mode interactions, thus limiting the laser's use for low frequency Doppler shift measurements Results are presented here for lasers of different constructions which show that under appropriate running conditions this noise spectrum may be suppressed An anemometer based on the argon laser operating under optimum conditions has been developed, and results are presented of the heterodyne spectra from a fluid in both laminar and turbulent flow and the homodyne spectra of fluids in turbulent flow
7 citations
01 Dec 1969
TL;DR: The theory of special relativity predicts a transverse Doppler effect of a laser beam retro-reflected from an artificial satellite in such a two-way system as discussed by the authors, which is found to be four times as large as the same effect in one-way systems.
Abstract: The theory of special relativity predicts a transverse Doppler effect of a laser beam retro-reflected from an artificial satellite In such a two-way system the transverse Doppler effect is found to be four times as large as the same effect in a one-way system
4 citations
01 Dec 1969
TL;DR: In this article, a passive interferometer is proposed and shown to have significant advantages over the local oscillator-heterodyne type of coherent detection or a two-beam differential Doppler technique.
Abstract: All previously reported laser Doppler velocity measuring devices employ either the local oscillator-heterodyne type of coherent detection or a two-beam differential Doppler technique. A third method employing a passive interferometer is proposed and shown to have significant advantages.
01 Jan 1969