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Laser vibrometer speckle-noise cancellation

T H Wilmshurst and N A Halliwell

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When a rotating scattering disc is used to frequency-shift the reference beam of a laser vibrometer, the noise floor is determined by speckle noise. The speckle noise is cancelled by recording it in the absence of target vibration and then subtracting the recorded signal Vr from that obtained when measuring the vibration. Vr is the average for 256 disc rotations, to reduce the aperiodic amplifier noise that is also recorded. Reduction factors obtained were waveform, -12 dB and spectrum, 0-12.8 kHz, 16 Hz resolution, -14 dB; 0-200 Hz, 0.25 Hz resolution, -30 dB.


PACS

42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

46.70.Lk Other structures

46.80.+j Measurement methods and techniques in continuum mechanics of solids

07.10.-h Mechanical instruments and equipment

Subjects

Instrumentation and measurement

Optics, quantum optics and lasers

Condensed matter: structural, mechanical & thermal

Dates

Issue 4 (April 1993)



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