Abstract
In previous works, an optical technique for extraction and separation of remote static vibrations has been demonstrated. In this paper, we will describe an approach in which RF speckle movement is used to extract remote vibrations of a static target. The use of conventional radar Doppler methods is not suitable for detecting vibrations of static targets. In addition, the speckle method has an important advantage, in that it is able to detect vibrations at far greater distances than what is normally detected in classical optical methods. The experiment described in this paper was done using a motorized vehicle, which engine was turned on and off. The results showed that the system was able to distinguish between the different engine states, and in addition, was able to determine the vibration frequency of the engine. The first step towards real time detection of human vital signs using RF speckle patterns is presented.
Highlights
The use of optical sensing technology to extract vibration sources has been successfully demonstrated in previous works
We found out that was it possible to detect the movement of the vehicle, but it was possible to determine its vibration frequency
We have demonstrated the ability to extract and separate remote vibrations by using RF speckles
Summary
The use of optical sensing technology to extract vibration sources has been successfully demonstrated in previous works. An optical system was designed and demonstrated for the detection of sounds by projecting a laser beam on a vibrating target and observing the movement of the secondary speckle patterns that are created by the interferences from the target’s roughness [1]. One may track the changes in the light phase that are being scattered from the target surface. This speckle-pattern interferometry was used for measuring displacements and analyzing vibration frequencies, as well as characteristics of the object deformations. The deformations are due to changes in loading, temperature, etc This procedure produces a speckle pattern that corresponds to the object’s local surface changes between two exposures. From the correlation between the speckle patterns, both the magnitude and the direction of the object’s local surface displacement are able to be determined
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