Polytec OFV-512 User Manual

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In Polytec’s vibrometers, the velocity and displacement measurement is car-
ried out using a modified Mach-Zehnder interferometer.
2)9 The optical configuration in the sensor head OFV-511 is shown schematically
in figure C.2.
The light source is a helium neon laser which provides a linear polarized
beam. The polarizing beam splitter BS1 splits the beam into the object beam
and the reference beam.
The object beam passes through the polarizing beam splitter BS2 and is
focused into the fiber with an input coupler. The beam is then emitted from the
end of the fiber, passes through a
λ /4 plate and is focused using the fiber
head or the mini sensor on the object and scattered back from there. The
polarizing beam splitter BS2 then functions as an optical directional coupler
together with the λ /4 plate, and deflects the object beam to the beam splitter
BS3. As both arms of the "internal" interferometer are symmetrical, the optical
path difference vanishes within the interferometer. The resulting path differ-
ence is equal to twice the distance between the beam splitter BS2 and the
object.
The Bragg cell in the reference arm generates the additional frequency offset
to determine the sign of the velocity.
The resulting interference signal of the object beam and reference beam is
converted into an electrical signal in the photo detector and subsequently
decoded in the controller.
Figure C.2: Optical configuration of the interferometer in the sensor head OFV-511
BS 1
Object
Prism
Bragg C ell
BS 3
BS 2Laser
Detector
C oupler
Fiber H ead
or
M ini S ensor
R eference
Beam
Object Beam
F iber
λ/4

Polytec OFV-512 Specifications

General

Brand	Polytec
Model	OFV-512
Category	Measuring Instruments
Language	English