Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1993-01-19
1995-09-12
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
341 13, 25023116, G01D 534
Patent
active
054499003
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a laser detector, for example, a torquemeter or device for measuring the torque transmitted through rotating shaft systems or a shaft encoder or device which provides an indication of angular position.
BACKGROUND OF THE INVENTION
In engineering installations power is frequently transmitted from a source, such as an internal combustion engine, a gas turbine or an electric motor, to a receiver, such as a compressor, dynamo, propellor or wheel, through a gearbox by means of torque applied to a rotating shaft. The transmission of torque is therefore of primary importance in the research and development of more efficient and reliable transmission systems. Design engineers are concerned to provide a steady transmission of torque through transmission systems so as to minimize gear wear, bearing and coupling failure, shaft fatigue failure and other associated torsional vibration and noise problems. Modern power transmission systems, furthermore, often involve the use of flexible couplings, the lifetimes of which are severely restricted if high levels of fluctuating torque are present.
To date, progress in these fields has been hindered by the lack of an instrument capable of providing immediate, accurate measurements of time-resolved torque through a driven system.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention there is provided a laser detector comprising means for generating a beam of laser light and directing it onto the surface of a rotary shaft; detector means associated with the beam for detecting the intensity of light backscattered by the surface and providing an output signal related to the detected intensity; signal-processing means associated with the beam including memory means for storing a reference waveform, the signal-processing means being operable to provide an output signal indicative of the phase of the detected intensity output signal relative to the reference waveform; and, hence, an indication of the angular position of the shaft relative to a reference position.
In a further aspect the invention provides a laser torquemeter comprising at least two such laser detectors, the beams of laser light generated by the detectors being directed onto the surface of the rotary shaft at locations spaced longitudinally along the shaft from one another; the torquemeter further comprising comparator means for comparing the output signals from the signal-processing means of the respective detectors to provide an indication of torque transmitted through the shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
A shaft encoder and one form of laser torquemeter in accordance with the invention will now be described in detail, by way of example, with reference to the drawings, in which: with the invention; and
FIG. 2 is a schematic illustration of a torquemeter in accordance with the invention.
DETAILED DESCRIPTION
The shaft encoder 10 shown in FIG. 1 utilizes the formation of a `speckle pattern` to measure the angular position of a rotating shaft 12.
A speckle pattern is formed when a laser beam is incident on an optically rough surface. Constructive and destructive interference of de-phased but still coherent component wavelets results in a chaotic distribution of high and low intensities in the backscattered light. This distribution is referred to as a speckle pattern. The amplitude of each speckle in the pattern may be considered to be constant across its extent and neighboring speckles will be uncorrelated.
When the rough surface moves, the speckles forming the pattern will tend to move with the surface until a sufficient change in the population of scatterers at the surface occurs and the speckles `boil`. Thus, if the surface rotates, as in the case of the surface of the shaft 12, the speckle pattern observed in any plane will repeat exactly with each rotation as the illuminated population of scatterers at the surface repeats with each revolution.
If the speckle pattern is sampled using a suitable photodetector, a periodi
REFERENCES:
patent: 3584959 (1971-06-01), Del Carlo et al.
patent: 3935447 (1976-01-01), Black et al.
patent: 4908510 (1990-03-01), Huggins et al.
patent: 5006703 (1991-04-01), Shikunami et al.
Applied Optics, vol. 28, No. 20, Oct. 15, 1989, Yamaguchi et al, "Laser speckle rotary encoder", pp. 4401-4406.
Derwent Abstract of Patent No. SE,A,8 402 159, Oct. 19, 1985, Bijlenga et al, (1 page).
Derwent Abstract of Patent No. SU,A,1 506 359, Sep. 7, 1989, Kholin, (1 page).
Applied Optics, vol. 26, No. 19, Oct. 1, 1987, Ami et al, "Optical method of measuring angular displacement using a diffraction pattern", pp. 4310-4312.
Patent Abstracts of Japan, vol. 014, No. 422, Publication No. 02 165 007, Jun. 26, 1990, p. 1104.
Allen Stephone B.
University of Southampton
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