Application of the Displacement Measurement
The application of the displacement measurement takes over the experimental device and the conditions of using the laser diode for the application of the speed measurement. The pseudo-period of the laser emission power defined by
is associated with a quantified displacement worth half a wavelength (qqs 1/10 µm).
In the same way as in the framework of the speed measurement, the displacement direction is obtained by observation of the zig-zag shape of the laser emission power.
It is thus possible to reconstruct the displacement of an object at the resolution of the half wavelength in raising or lowering a counter of the same value at each appearance of a pseudo-period. The following figure presents this reconstruction technique.
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The figure here below shows an experimental real time measurement by this method applied to the measurement of track vibration for a railway :
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