Patent ID: 8587780

Claim:
A device for measuring a twist of a rotating shaft, the device comprising: a laser beam generator which emits a laser beam; first and second polarizing filters secured to the shaft and spaced apart from each other; and a laser radiation receiver, said laser beam generator being installed so that said laser beam emitted by the laser beam generator passes through the first and second filters, and said laser radiation receiver being installed to receive said beam after said beam has passed through both of the first and second filters, wherein a reflection system is installed in a vicinity of the second filter to reflect the beam that has passed through the first and second filters and return the beam parallel to itself towards said receiver through the first and second filters, said beam passing through the first and second filters being substantially parallel to an axis of rotation of said shaft, wherein said reflection system comprises a 45° frustoconical mirror, wherein one of the filters comprises a ring in which polarizing zones and non-polarizing zones alternate so as to obtain a periodic succession of polarizations representative of a measurement value and of a reference value, respectively, and wherein the twist of the rotating shaft is measured based on a ratio between the measurement value and the reference value.