EP0248277A2
Expired / Lapsed
EP
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Two-frequency laser rotation sensor system
Assignee: Optra Inc
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Filing: 1987-05-20
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Granted: —
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Expires: 2007-05-20
Abstract
Abstract Disclosed is a rotation sensing system which utilizes a two-frequency laser to provide two laser beams (16a,16b) to illuminate a lateral surface (14) of a rotatable body (12). A beam splitter (20) divides the two-frequency laser into two beams, and the system detects the modulation frequency of the scattered light when the shaft (12) is rotating. This detected modulation frequency is compared to the frequency difference between the two beams (16a,16b). The phase difference between the detected modulation frequency and the difference frequency represents units of displacement of the rotatable body (12).
Inventors
- 👤 Geert Wyntjes
- 👤 Michael Hercher
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 19:20
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
76 words
A rotational displacement sensor system comprising: means for providing two laser beams (16a,16b) of different frequencies superposed on a lateral surface of a rotatable member, said two laser beams being separated from each other and being incident at an angle ϑ at a point(P)on said lateral surface; means for detecting the modulation frequency of light scattered by said lateral surface; means for processing said detected modulation frequency to determine the rotational displacement of said rotatable member.
Claim 2
Dependent Claim
76 words
A rotational displacement sensor system comprising: means for providing two laser beams (16a,16b) of different frequencies superposed on a lateral surface of a rotatable member, said two laser beams being separated from each other and being incident at an angle ϑ at a point(P)on said lateral surface; means for detecting the modulation frequency of light scattered by said lateral surface; means for processing said detected modulation frequency to determine the rotational displacement of said rotatable member.
Claim 3
Dependent Claim
18 words
The rotational displacement sensor system of claim 1 wherein said rotating member is a rotatable cylindrical shaft (12).
Claim 4
Dependent Claim
109 words
The rotational displacement sensor system of claim 1 wherein said means for providing two laser beams comprises: a two-frequency laser, the two frequencies of said laser differing by an amount on the order of 200 to 2000 KHz; means (20) for polarizing and splitting a laser beam from said two-frequency laser, one beam (16a) of said split laser beam being directed through a focusing lens (24) to a point P on said lateral surface, and another beam (16b) of said split beam being directed towards an adjustable mirror (26) before being directed by said adjustable mirror through said focusing lens (24) to the point P on said lateral surface.
Claim 5
Dependent Claim
23 words
The rotational displacement sensor system of claim 3 wherein said two-frequency laser provides two beams (16a,16b) differing in frequency by precisely 250 KHz.
Claim 6
Dependent Claim
50 words
The rotational displacement sensor system of claim 1 wherein said means for detecting the modulation frequency of light scattered by said lateral surface comprises a detector (28) lens and a PIN-diode which (30) receives light passed through the detector lens (28) and provides a signal representing the detected modulation frequency.
Claim 7
Dependent Claim
73 words
The rotational displacement sensor system of claim 1 wherein said means for detecting the modulation frequency of light scattered by said lateral surface comprises: means for detecting the modulation frequency of light scattered by said lateral surface when said rotatable member is stationary so as to verify the frequency difference F D between the two laser beams (16a,16b); means for detecting the modulation frequency F when said rotatable member is set in motion.
Claim 8
Dependent Claim
55 words
The rotational displacement sensor system of claim 1 wherein the modulation frequency shift F = F D ± (2v sin ϑ)/w where w is the wavelength of the laser, v is the velocity component in the plane of the surface, and ϑ is the angle of incidence of the laser relative to the lateral surface.
Claim 9
Dependent Claim
82 words
The rotational displacement sensor system of claim 6 wherein said means for processing said detected modulation frequency comprises means for detecting the phase difference between the laser difference frequency and said detected modulation frequency when said rotatable member is in motion, one full cycle of said phase difference representing one unit of distance d where d = w/2ϑ, where w is the wavelength of the laser and ϑ is the angle of incidence of the laser beam relative to said lateral surface.
Claim 10
Dependent Claim
39 words
The rotational displacement sensor system of claim 1 further comprising means for determining the angular velocity of the rotating member utilizing a measurement of rotational displacement and the displacement of the point of measurement from the axis of rotation.
Claim 11
Dependent Claim
93 words
A rotational displacement sensor system comprising: a cylindrical grating (14) replicated on a lateral surface of a rotatable member (12); means for providing two laser beams (16a,16b) of different frequencies superposed on said cylindrical grating (14), said two laser beams (16a,16b) being separated from each other and being incident at an angle ϑ at a point P on said cylindrical grating (14); means for detecting the modulation frequency of light scattered by said cylindrical grating (14); means for processing said detected modulation frequency to determine the rotational displacement of the rotatable member (12);
Claim 12
Dependent Claim
93 words
A rotational displacement sensor system comprising: a cylindrical grating (14) replicated on a lateral surface of a rotatable member (12); means for providing two laser beams (16a,16b) of different frequencies superposed on said cylindrical grating (14), said two laser beams (16a,16b) being separated from each other and being incident at an angle ϑ at a point P on said cylindrical grating (14); means for detecting the modulation frequency of light scattered by said cylindrical grating (14); means for processing said detected modulation frequency to determine the rotational displacement of the rotatable member (12);
Claim 13
Dependent Claim
18 words
The rotational displacement sensor system of claim 10 wherein said rotatable member is a rotating cylindrical shaft (12);
Claim 14
Dependent Claim
110 words
The rotational displacement sensor system of claim 10 wherein said means for providing two laser beams comprises: a two-frequency laser, the two frequencies of said laser differing by an amount on the order of 200 to 2000 KHz; means for polarizing and splitting a laser beam from said two-frequency laser, one beam (16a) of said split laser beam being directed through a focusing lens (24) to the point P on said cylindrical grating (14) and another beam (16b) of said split beam being directed towards an adjustable mirror (26) before being directed by said adjustable mirror(26) through said focusing lens (24) to the point P on said cylindrical grating (14).
Claim 15
Dependent Claim
22 words
The rotational displacement sensor system of claim 12 wherein said two-frequency laser provides two beams differing in frequency by precisely 250 KHz.
Claim 16
Dependent Claim
50 words
The rotational displacement sensor system of claim 10 wherein said means for detecting the modulation frequency of light scattered by said cylindrical grating (14) comprises a detector lens (28) and a PIN-diode (30) which receives light passed through the detector lens and provides a signal representing the detected modulation frequency.
Claim 17
Independent Claim
88 words
A method of determining the rotational displacement of a rotatable body, said method comprising the steps of: providing a cylindrical grating replicated on a lateral surface of the rotatable body; superposing two laser beams of different frequencies on said cylindrical grating, said two beams emanating from different locations and being incident at an angle ϑ at a point P on said cylindrical grating; detecting the modulation frequency of light scattered by said cylindrical grating; processing said detected modulation frequency to determine the rotational displacement of the rotatable body.
Claim 18
Independent Claim
88 words
A method of determining the rotational displacement of a rotatable body, said method comprising the steps of: providing a cylindrical grating replicated on a lateral surface of the rotatable body; superposing two laser beams of different frequencies on said cylindrical grating, said two beams emanating from different locations and being incident at an angle ϑ at a point P on said cylindrical grating; detecting the modulation frequency of light scattered by said cylindrical grating; processing said detected modulation frequency to determine the rotational displacement of the rotatable body.
Claim 19
Dependent Claim
109 words
The method of determining the rotational displacement of a rotatable body of claim 15 wherein said step of superposing two laser beams of different frequencies comprises: providing a two-frequency laser having two frequencies which differ by an amount on the order of 200 to 2000 KHz; polarizing and splitting a laser beam produced by said two-frequency laser, one beam of said split laser beam being directed through a focusing lens to the point P on said cylindrical grating and another beam of said split beam being directed towards an adjustable mirror before directed by said adjustable mirror through said focusing lens to the point P on said cylindrical grating.
Claim 20
Dependent Claim
70 words
The method of determining the rotational displacement of a rotatable body of claim 15 wherein said step of detecting the modulation frequency comprises the steps of: detecting the modulation frequency of light scattered by said cylindrical grating when said rotatable body is stationary so as to verify the frequency difference F D between the two laser beams; detecting the modulation frequency F when said rotatable body is set in motion.
Claim 21
Dependent Claim
61 words
The method of determining the rotational displacement of a rotating body of claim 17 wherein the modulation frequency shift F equals F D ± (2v sinϑ)/w where w is the wavelength of the laser, v is the velocity component in the plane of the surface, and ϑ is the angle of incidence of the laser beam relative to the cylindrical grating.
Claim 22
Dependent Claim
89 words
The method of determining the rotational displacement of a rotatable body of claim 17 wherein said step of processing said detected modulation frequency comprises the steps of: detecting the phase difference between the laser difference frequency and said detected modulation frequency when said rotating body is in motion, one full cycle of said phase difference representing one unit of distance d where d = w/2sinϑ, where w is the wavelength of the laser and ϑ is the angle of incidence of the laser beam relative to the cylindrical grating.
Claim 23
Dependent Claim
47 words
The method of determining the rotational displacement of a rotating body of claim 15 further comprising the step of utilizing a measurement of rotational displacement and the displacement of the point of measurement from the axis of rotation to determine the angular velocity of the rotating body.
References Cited (Backward Citations)
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