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US5210409A
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Apparatus and method for sensing the relative position of two members employing a variable wavelength source and wavelength dependant scanner
Assignee: BAE Systems Electronics Ltd
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Filing: 1992-05-06
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Granted: 1993-05-11
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Expires: 2012-05-06
Abstract
Abstract The relative position (M) of two members (33, 34) is sensed by scanning (S) an optical beam (25) over an encoded pattern (20) carried by one of the members, and by using a read head (21) secured to the other member to receive an optical signal transmitted from the encoded pattern (20). This optical signal is received by an optical position sensor to discriminate from the frequency of the signal, the position of the read head (21) relative to the encoded pattern (20). As the relative position is detected from the frequency of the signal rather than its intensity, components can be replaced without recalibration. The optical beam (25) is scanned by using a light source of variable wavelength which is passed through a device, such as a diffraction grating or a gradient index lens, for deflecting the beam (25) dependent on its wavelength.
Inventors
- 👤 Duncan P. Rowe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 21:19
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
114 words
Position sensing apparatus, for sensing the relative position of two members, including an encoded pattern carried by one of said members, means for producing an optical beam of varying wavelength, scanning means for deflecting said beam dependent on its wavelength to scan over said encoded pattern, said encoded pattern being arranged to transmit part of said beam as an optical signal, a readhead secured to said other member to receive said optical signal and an optical position sensor to receive said optical signal from said readhead and to discriminate, from the frequency of said optical signal, the position of said readhead relative to said encoded pattern and consequently the relative position of said members.
Claim 2
Dependent Claim
114 words
Position sensing apparatus, for sensing the relative position of two members, including an encoded pattern carried by one of said members, means for producing an optical beam of varying wavelength, scanning means for deflecting said beam dependent on its wavelength to scan over said encoded pattern, said encoded pattern being arranged to transmit part of said beam as an optical signal, a readhead secured to said other member to receive said optical signal and an optical position sensor to receive said optical signal from said readhead and to discriminate, from the frequency of said optical signal, the position of said readhead relative to said encoded pattern and consequently the relative position of said members.
Claim 3
Dependent Claim
15 words
Position sensing apparatus as in claim 1, in which said readhead incorporates said scanning means.
Claim 4
Dependent Claim
24 words
Position sensing apparatus as in claim 1, in which said scanning means includes a diffraction grating for deflecting the beam dependent on its wavelength.
Claim 5
Dependent Claim
18 words
Position sensing apparatus as in claim 3, in which said diffraction grating is arranged in the Littrow configuration.
Claim 6
Dependent Claim
19 words
Position sensing apparatus as in claim 3, in which said diffraction grating is combined with a gradient index lens.
Claim 7
Dependent Claim
30 words
Position sensing apparatus as in claim 1, in which said means for producing the optical beam of varying wavelength includes a wideband light source governed by a variable wavelength filter.
Claim 8
Dependent Claim
19 words
Position sensing apparatus as in claim 6, in which said variable wavelength filter is a multiple beam interference device.
Claim 9
Dependent Claim
19 words
Position sensing apparatus as in claim 7, in which said multiple beam interference device is a Fabry Perot etalon.
Claim 10
Dependent Claim
17 words
Position sensing apparatus as in claim 8, in which said etalon is arranged to be piezoelectrically driven.
Claim 11
Dependent Claim
23 words
Position sensing apparatus as in claim 8, in which said etalon is a solid state device including a variable refractive index liquid crystal.
Claim 12
Dependent Claim
18 words
Position sensing apparatus as in claim 6, in which said variable wavelength filter is a rotatable diffraction grating.
Claim 13
Dependent Claim
17 words
Position sensing apparatus as in claim 6, in which said variable wavelength filter is an interference filter.
Claim 14
Dependent Claim
20 words
Position sensing apparatus as in claim 1, in which said scanning means is arranged to move said optical beam sinusoidally.
Claim 15
Dependent Claim
45 words
Position sensing apparatus, as in claim in which said encoded pattern varies in regular increments in the direction or sense of movement between said two members, and said scanning means is arranged to scan said optical beam transversely to such direction or sense of movement.
Claim 16
Dependent Claim
27 words
Position sensing apparatus as in claim 14, in which successive increments of said encoded pattern are arranged to transmit optical signals of different frequency to said readhead.
Claim 17
Dependent Claim
33 words
Position sensing apparatus as in claim 15, in which said encoded pattern includes an increment which is arranged to transmit a unique light signal to said readhead to serve as a reference point.
Claim 18
Dependent Claim
89 words
Position sensing apparatus as in claim 1, including a second encoded pattern to be carried by the said one member, means for producing a second optical beam of varying wavelength, a second scanning means for deflecting said second beam dependent on its wavelength to scan over said second encoded pattern, and a second readhead to be secured to the said other member, the said two encoded patterns being different to assist said optical position sensor to discriminate more finely the position of said readhead relative to said encoded patterns.
Claim 19
Independent Claim
77 words
A method of sensing the relative position of two members, including providing an optical beam of variable wavelength, refracting the beam dependent on its wavelength to scan, from a fixed position relative to one of said members, over an encoded pattern carried by the other of said members to produce an optical signal, and detecting the portion of said encoded pattern over which the optical beam has been scanned by sensing the frequency of the optical signal.
Claim 20
Independent Claim
77 words
A method of sensing the relative position of two members, including providing an optical beam of variable wavelength, refracting the beam dependent on its wavelength to scan, from a fixed position relative to one of said members, over an encoded pattern carried by the other of said members to produce an optical signal, and detecting the portion of said encoded pattern over which the optical beam has been scanned by sensing the frequency of the optical signal.
Claim 21
Dependent Claim
26 words
A method as in claim 18, additionally including passing a wideband light source through a variable wavelength filter to produce said optical beam of variable wavelength.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1996-05-10 | 1996-11-09 | 1997-05-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-05-10 | 2000-11-09 | 2001-05-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-05-10 | 2004-11-09 | 2005-05-11 | $7700.00 | Window Closed / Lapsed |