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  • Rotational Sensor Exploits Polarization

Photonics.com
May 2014
ERLANGEN, Germany, May 29, 2014 — A rotational angle sensor that measures light polarization aims to be less finicky than its optical and magnetic counterparts.

Magnetic sensors are durable but not as precise as optical sensors. Optical sensors, meanwhile, must be precisely mounted relative the object being measured.


A polarization sensor, right, measures the angle of rotation of a shaft with integrated polarizing film. Courtesy of the Fraunhofer Institute for Integrated Circuits.


A polarization sensor developed at the Fraunhofer Institute for Integrated Circuits is not quite as accurate as an optical sensor, but is more flexible in terms of positioning.

It involves attaching a polarizing film to a test object such as a drive shaft and shining a beam of light on it. The light’s polarization vector rotates with the object, and this movement is registered by wire lattices in a CMOS chip situated within the light beam.

“In order to obtain a definite measurement of the angular position of a shaft, we need at least three grids that are each structured in different directions,” said group manager Dr. Norbert Weber. “Depending on the measuring task we can also add further grids, thus adapting the chip to suit the specific requirements of customers while increasing measurement accuracy.”

The sensor will be displayed at the Sensor + Test 2014 trade fair June 3 through 5 in Nuremberg. For more information, visit www.fraunhofer.de.


GLOSSARY
polarization
With respect to light radiation, the restriction of the vibrations of the magnetic or electric field vector to a single plane. In a beam of electromagnetic radiation, the polarization direction is the direction of the electric field vector (with no distinction between positive and negative as the field oscillates back and forth). The polarization vector is always in the plane at right angles to the beam direction. Near some given stationary point in space the polarization direction in the beam...
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