US3670168A
Expired / Lapsed
US
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Light direction sensor
Assignee: National Aeronautics and Space Administration
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Filing: 1970-10-01
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Granted: 1972-06-13
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Expires: 1990-10-01
Abstract
Abstract A light direction sensor is disclosed for providing third axis control of spacecraft. The light direction sensor comprises a direction-sensitive modulator positioned before a set of telescopic light gathering optics which, in turn, is followed by a detector. The direction-sensitive modulator comprises birefringent crystal means cut at suitable angles so that the retardation suffered by the light beam would be dependent upon the direction from which the light beam is incident upon the crystal means. The crystal means is coupled with an electro-optic phase modulator which adds a sinusoidal retardation to the light beam. The crystal means and modulator are positioned between crossed polarizers to convert the beam retardation to intensity varying at a certain frequency. The transmitted intensity is then collected by the telescopic optics and led to the detector.
Inventors
- 👤 Alan R Johnston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 20:37
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/03; G02F1/0327; B; B64; B64G; B64G1/00; B64G1/22; B64G1/24; B64G1/36; B64G1/361; G01; G01S; G01S3/00; G01S3/78; G01S3/782
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
150 words
In an electrical optical direction sensor for providing a measure of the angle between a source of light and a nominal axis of the sensor, the combination which comprises: polarizing means for linearly polarizing a light signal; a directional wave plate having an optical axis at an angle to the nominal axis, the directional wave plate being arranged to develop a pair of orthogonally related signals and retarding one of said signals with respect to the other as a function of the angle between the source and the nominal axis; an electro-optical modulator having an optical axis aligned with the nominAl axis for phase modulating the light signal from the wave plate; an analyzer for converting the phase modulated signal into an amplitude modulated light signal; and means for detecting and demodulating the light signal from the analyzer to provide an output signal which is a measure of said angle.
Claim 2
Dependent Claim
150 words
In an electrical optical direction sensor for providing a measure of the angle between a source of light and a nominal axis of the sensor, the combination which comprises: polarizing means for linearly polarizing a light signal; a directional wave plate having an optical axis at an angle to the nominal axis, the directional wave plate being arranged to develop a pair of orthogonally related signals and retarding one of said signals with respect to the other as a function of the angle between the source and the nominal axis; an electro-optical modulator having an optical axis aligned with the nominAl axis for phase modulating the light signal from the wave plate; an analyzer for converting the phase modulated signal into an amplitude modulated light signal; and means for detecting and demodulating the light signal from the analyzer to provide an output signal which is a measure of said angle.
Claim 3
Dependent Claim
36 words
The combination as defined in claim 1 including a compensator positioned between the directional wave plate and the modulator for compensating for the retardation by the directional wave plate of light coincident with the nominal axis.
Claim 4
Dependent Claim
39 words
The combination as defined in claim 1 wherein the directional wave plate is a plate of birefringent crystal with the plate being cut so that its optical axis is at an angle of approximately 45* to the nominal axis.
Claim 5
Dependent Claim
35 words
The combination as defined by claim 3 wherein the electro-optical modulator is a plate of birefringent crystal cut with its optical axis perpendicular to the plane of the plate and aligned with the nominal axis.
Claim 6
Dependent Claim
57 words
The combination as defined in claim 4 including a compensator plate of a birefringent crystal positioned between the wave plate and the modulator, the compensator plate having a thickness to provide a retardation of the light signals passing therethrough which is equal to the retardation of the directional wave plate for a predetermined direction of light propagation.
Claim 7
Dependent Claim
29 words
The combination as defined in claim 1 wherein the polarizing means and the analyzer comprise sheets of light polarizing material oriented at ninety degrees with respect to each other.
Claim 8
Dependent Claim
17 words
The combination as defined in claim 6 wherein the electro-optical modulator sinusoidally modulates said one light signal.
Claim 9
Dependent Claim
55 words
The combination as defined in claim 7 wherein the means for detecting and demodulating the light signal from the analyzer includes: telescope means including a field stop for collecting said amplitude modulated light signal; detector means for providing an electrical signal representative of the modulated light signal; and demodulator means for demodulating said electrical signal.
Claim 10
Dependent Claim
152 words
In an optical direction sensor for providing a measure of the angle between a source of light and a nominal axis of the sensor, the combination which comprises: polarization means positioned on the nominal axis for linearly polarizing light from the source; a directional wave plate positioned on the nominal axis for receiving light transmitted through the polarizing means and retarding at least a portion of said light as a function of the angle between the source and the nominal axis, the directioanl wave plate having an optical axis disposed at an angle to the nominal axis; an electro-optical modulator positioned on the nominal axis and having an optical axis aligned with the nominal axis for phase modulating the retarded light signal from the directional wave plate; and means for detecting and demodulating the light signal from the electro-optical modulator to provide an output signal which is a measure of said signal.
Claim 11
Dependent Claim
152 words
In an optical direction sensor for providing a measure of the angle between a source of light and a nominal axis of the sensor, the combination which comprises: polarization means positioned on the nominal axis for linearly polarizing light from the source; a directional wave plate positioned on the nominal axis for receiving light transmitted through the polarizing means and retarding at least a portion of said light as a function of the angle between the source and the nominal axis, the directioanl wave plate having an optical axis disposed at an angle to the nominal axis; an electro-optical modulator positioned on the nominal axis and having an optical axis aligned with the nominal axis for phase modulating the retarded light signal from the directional wave plate; and means for detecting and demodulating the light signal from the electro-optical modulator to provide an output signal which is a measure of said signal.
Claim 12
Dependent Claim
62 words
The combination as defined in claim 9 wherein the last named means includes an analyzer and a detector positioned in that order to receive light from the modulator, the analyzer comprising a polarizing means for converting the phase modulated signal into an amplitude or intensity modulated light signal, the detector including means for detecting and demodulating the light signal from the analyzer.
Claim 13
Dependent Claim
39 words
The combination as defined in claim 10 wherein the directional wave plate is a plate of birefringent crystal with the plate being cut so that its optical axis is at an angle of approximately 45* with the nominal axis.
Claim 14
Dependent Claim
35 words
The combination as defined in claim 11 wherein the electro-optical modulator is a plate of birefringent crystal cut with its optical axis perpendicular to the plane of the plate and aligned with the nominal axis.
Claim 15
Dependent Claim
44 words
The combination as defined in claim 12 including a compensator plate of a birefringent crystal positioned between the wavE plate and the modulator to compensate for the retardation of light signals passing through the directional wave plate which are parallel to the nominal axis.
Claim 16
Dependent Claim
26 words
The combination as defined in claim 13 wherein the polarizing means and the analyzer comprises light polarizing members oriented at 90* with respect to each other.
Claim 17
Dependent Claim
16 words
The combination as defined in claim 12 wherein the modulator sinusoidally modulates the retarded light signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-13 | 1975-12-13 | 1976-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-13 | 1979-12-13 | 1980-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-13 | 1983-12-13 | 1984-06-13 | $7700.00 | Window Closed / Lapsed |