Polytec PSV 300, Руководство по оборудованию

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In Polytec’s vibrometers In Polytec’s vibrometers, the , the velocity and displacement measurement is velocity and displacement measurement is
carried out using a modified Mach-Zehnder interferometer. The optical carried out using a modified Mach-Zehnder interferometer. The optical
configuration in the scanning head is
configuration in the scanning head is shown schematically in shown schematically in fi fi gu gu re re B. B. 1 1 ..
The light source is The light source is a helium neon laser, which provides a linear a helium neon laser, which provides a linear polarized polarized
beam. The polarizing beam splitter BS1 splits the beam into beam. The polarizing beam splitter BS1 splits the beam into the object beam the object beam
and the reference beam. and the reference beam.
The object beam passes through the polarizing beam splitter BS2 as well as a The object beam passes through the polarizing beam splitter BS2 as well as a
λ λ
/4-p /4-plate late, is , is then then focu focussed ssed by t by the l he lens ens on t on the o he objec bject an t and sca d scatter ttered b ed back f ack from rom
there. The polarizing beam splitter BS2 then functions as an there. The polarizing beam splitter BS2 then functions as an optical optical
directional coupler together with the directional coupler together with the
λ λ
/4-p /4-plate late, and defl , and deflects the o ects the objec bject beam to t beam to
the beam splitter BS the beam splitter BS3. As both arms of the 3. As both arms of the ’internal' interf ’internal' interferometer are erometer are
symmetric symmetrical, the optical path difference between the object beam al, the optical path difference between the object beam and the and the
reference beam vanishes within the reference beam vanishes within the interferomet interferometer. The resulting path er. The resulting path
difference is equal to twice the distance between the beam splitter BS2 and difference is equal to twice the distance between the beam splitter BS2 and
the object. the object.
The Bragg cell in The Bragg cell in the reference arm of the the reference arm of the interferometer generates the interferometer generates the
additional frequency offset to determine the sign of the velocity. additional frequency offset to determine the sign of the velocity.
The resulting interference signal of the object beam The resulting interference signal of the object beam and reference beam is and reference beam is
converted into an electrical signal in the converted into an electrical signal in the photo detector and subsequently photo detector and subsequently
decoded in the controller. decoded in the controller.
Figure B.1: Optical configuration in the scanning head Figure B.1: Optical configuration in the scanning head
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