Cylindrical Grating Rotation Sensor

摘要

The invention comprises a Rotation sensor with
- a light source (10),
- a light detector (9),
- an internal part (1) having a first lateral surface (4) which is globally cylindrical and convex,
- an external part (7) having a second lateral surface (6) which is globally cylindrical and concave, said first and second lateral surfaces both having a same central axis defining a rotation axis (A) for a relative rotation between said internal part and said external part the angle of which this rotation sensor can measure,
- at least a first grating (3; 31,32; 103) arranged at said first lateral surface with its grating lines parallel to said rotation axis, and
- at least a second grating (5; 51,52; 105) arranged at said second lateral surface with its grating lines parallel to said rotation axis; the internal and external parts being arranged so that said first grating and said second grating are facing each other, one of said first and second gratings diffracting light in transmission and the other one diffracting light in reflexion, this rotation sensor being arranged so that the light provided by said light source is first incident on the grating diffracting it in transmission where this light is diffracted into first and second diffraction orders (first diffraction event), then this light diffracted into said first and second diffraction orders is incident on the other grating diffracting said light in reflexion respectively into third and fourth diffraction orders (second diffraction event) and finally the light diffracted back into said third and fourth diffraction orders is incident on said grating diffracting it in transmission where these third and fourth diffraction orders are respectively diffracted again and recombined so as to form a recombined light (third diffraction event), the periods of said first and second gratings as well as the diffraction orders in said first, second and third diffraction events being selected so that two light rays originating from a same first point (D) in said first diffraction event and respectively propagating along first and second directions and then, after said second diffraction event, respectively along third and fourth directions are substantially incident on a same second point of the grating intervening in said third diffraction event where they recombine together in a common fifth direction and interfere, said rotation sensor being further arranged so that the recombined light propagating along said common fifth direction after said third diffraction event is finally at least partially incident on said light detector, the intensity variation of this recombined light being used to determine a relative angular rotation between said internal part and said external part.