Interferometric torque and power sensor
AssigneeCreo Inc.
InventorDaniel Gelbart
Life of this patent
Estimating the term…
Abstract
An interferometric optical torque sensor senses the torque transmitted by a rotating shaft without requiring physical contact with the shaft. A diffraction grating is provided on the shaft with its grating lines parallel to the longitudinal dimension of the shaft. A laser beam is split in two and reflected from two axially-separated points of the grating. As the shaft twists, the phase of the light in the diffracted orders of the light reflected from the grating changes. By superimposing the diffracted beams an interference pattern is created. The motion of the interference fringes in this pattern is proportional to the twist, therefore the torque, in the shaft. The power transmitted by the shaft may be computed from the torque and shaft speed.
Claims19
A method for measuring a torque in a shaft, the method comprising:
- providing a diffraction grating on said shaft, wherein when said shaft is twisted by said torque, a relative displacement is produced between areas of said grating that are spaced apart from one another along a longitudinal dimension of the shaft;
- illuminating a plurality of said spaced apart areas of said grating and creating an optical interference pattern by overlapping light diffracted from each of said spaced apart areas;
- and,
- determining said torque from said interference pattern using at least one light detector.
A method for determining a twist of a shaft, the method comprising:
- directing a first incident coherent radiation beam at a first region on a surface of the shaft, the first incident radiation beam producing a first diffracted output beam;
- directing a second incident coherent radiation beam at a second region on the surface of the shaft wherein the second region is spaced apart from the first region along a longitudinal dimension of the shaft, the second incident radiation beam producing a second diffracted output beam;
- generating an interference pattern in a region of space by overlapping the first and second diffracted output beams;
- and,
- measuring an optical intensity of at least a portion of the interference pattern and based on the measured optical intensity determining a value indicative of the twist of the shaft.
An apparatus for determining the twist of a shaft, the apparatus comprising:
- at least one radiation source;
- an optical system configured to receive radiation from the at least one radiation source and to direct a first incident radiation beam at a first region of the shaft and a second incident radiation beam at a second region of the shaft, the second region spaced apart from the first region along a longitudinal dimension of the shaft;
- one or more diffraction gratings on the shaft, the diffraction gratings positioned to produce a first diffracted beam in response to the first incident radiation beam and to produce a second diffracted beam in response to the second incident radiation beam wherein the first and second diffracted beams overlap with one another to create an optical interference pattern;
- and,
- at least one radiation detector, positioned to measure an optical intensity of at least a portion of the interference pattern.
Dependencies are inferred from the claim text.