Patent US3743969A successfully refreshed from Google Patents.
US3743969A
Expired / Lapsed
US
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Modulation servo control for frequency modulated ring laser gyro
Assignee: Boeing North American Inc
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Filing: 1969-11-12
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Granted: 1973-07-03
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Expires: 1989-11-12
Abstract
Abstract A ring laser gyro has a pair of counter-rotating beams, the difference frequency between the beams being indicative of the rotational rate to which the instrument is subjected. The beams are frequency modulated to minimize frequency-locking therebetween. A servo control is provided to maintain the modulation index of the frequency modulation to an optimum value for minimal frequency-locking between the beams.
Inventors
- 👤 T Hutchings
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:52
CPC Classifications
G; G01; G01C; G01C19/00; G01C19/58; G01C19/64; G01C19/66; G01C19/68; H; H01; H01S; H01S3/00; H01S3/10
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
127 words
A method for automatically maintaining the modulation index of the frequency modulation of the counter-rotating laser beams of a laser gyro at a predetermined optimum value comprising the steps of: heterodyning said beams together to generate a beat difference frequency signal; deriving an error signal from said difference frequency signal in accordance with the departure of said modulation index from said optimum value; and controlling the modulation index of said counter-rotating beams with said error signal so as to minimize said error signal by changing the frequency of said beams or by changing the modulation amplitude of said beams in accordance with the equation m B/F, where m is the modulation amplitude, B is the depth of modulation and F is the frequency of the modulating signal.
Claim 2
Independent Claim
127 words
A method for automatically maintaining the modulation index of the frequency modulation of the counter-rotating laser beams of a laser gyro at a predetermined optimum value comprising the steps of: heterodyning said beams together to generate a beat difference frequency signal; deriving an error signal from said difference frequency signal in accordance with the departure of said modulation index from said optimum value; and controlling the modulation index of said counter-rotating beams with said error signal so as to minimize said error signal by changing the frequency of said beams or by changing the modulation amplitude of said beams in accordance with the equation m B/F, where m is the modulation amplitude, B is the depth of modulation and F is the frequency of the modulating signal.
Claim 3
Dependent Claim
62 words
The method of claim 1 wherein said error signal is derived by using a dither signal to periodically vary the modulation index of said frequency modulation, demodulating said dither signal from the difference frequency signal, comparing said demodulated dither signal with the dither signal used to vary the modulation index and generating said error signal as a function of the relationship therebetween.
Claim 4
Dependent Claim
143 words
In a ring laser gyro including a pair of counter-rotating laser beams and means for frequency modulating said beams with a modulation signal having a modulation index of a predetermined optimum value, means for maintaining said index at said optimum valve, comprising: means for generating a beat difference frequency signal between said beams; means for detecting a preselected harmonic distortion component in said difference frequency signal and generating an error signal in accordance therewith; and servo means responsive to said error signal for controlling the modulation index of said counterrotating beams so as to minimize the distortion component, and for changing the modulation amplitude of said beams in accordance with the equation m B/F, where m is the modulation amplitude, B is the depth of modulation and F is the frequency of the modulating signal, or for changing the frequency of said beams.
Claim 5
Dependent Claim
143 words
In a ring laser gyro including a pair of counter-rotating laser beams and means for frequency modulating said beams with a modulation signal having a modulation index of a predetermined optimum value, means for maintaining said index at said optimum valve, comprising: means for generating a beat difference frequency signal between said beams; means for detecting a preselected harmonic distortion component in said difference frequency signal and generating an error signal in accordance therewith; and servo means responsive to said error signal for controlling the modulation index of said counterrotating beams so as to minimize the distortion component, and for changing the modulation amplitude of said beams in accordance with the equation m B/F, where m is the modulation amplitude, B is the depth of modulation and F is the frequency of the modulating signal, or for changing the frequency of said beams.
Claim 6
Independent Claim
122 words
A method for automatically maintaining the modulation index of the frequency modulation of the counter-rotating laser beams of a laser gyroscope at a predetermined optimum value comprising the steps of: heterodyning said beams together to generate a beat difference frequency signal; and deriving an error signal from said difference frequency signal by detecting the second harmonic of said difference frequency signal by synchronizing a sine wave oscillator with said difference frequency signal, doubling the frequency of said oscillator output and synchronously detecting the second harmonic component of said difference frequency signal by using the double frequency signal as a reference, said error signal being used to adjust the modulation index so as to minimize said second harmonic of said difference frequency signal.
Claim 7
Independent Claim
122 words
A method for automatically maintaining the modulation index of the frequency modulation of the counter-rotating laser beams of a laser gyroscope at a predetermined optimum value comprising the steps of: heterodyning said beams together to generate a beat difference frequency signal; and deriving an error signal from said difference frequency signal by detecting the second harmonic of said difference frequency signal by synchronizing a sine wave oscillator with said difference frequency signal, doubling the frequency of said oscillator output and synchronously detecting the second harmonic component of said difference frequency signal by using the double frequency signal as a reference, said error signal being used to adjust the modulation index so as to minimize said second harmonic of said difference frequency signal.
Claim 8
Dependent Claim
152 words
In a ring laser gyroscope including a pair of laser beams and means for frequency modulating said beams with a modulation signal having a modulation index of a predetermined optimum value, means for maintaining said index at said optimum value comprising: means for generating a beat difference frequency signal between said beams; means for detecting the second harmonic of said difference frequency signal and generating an error signal comprising synchronized oscillator means for generating a sine wave at the difference frequency in response to the difference frequency signal, frequency doubler means for doubling the frequency of the output of said synchronized oscillator means and synchronous detector means for receiving the output of said doubler means and the beat difference signal and generating an error signal in accordance with the phase relationship therebetween; and servo means responsive to said error signal for controlling the modulation index so as to minimize the distortion component.
Claim 9
Dependent Claim
152 words
In a ring laser gyroscope including a pair of laser beams and means for frequency modulating said beams with a modulation signal having a modulation index of a predetermined optimum value, means for maintaining said index at said optimum value comprising: means for generating a beat difference frequency signal between said beams; means for detecting the second harmonic of said difference frequency signal and generating an error signal comprising synchronized oscillator means for generating a sine wave at the difference frequency in response to the difference frequency signal, frequency doubler means for doubling the frequency of the output of said synchronized oscillator means and synchronous detector means for receiving the output of said doubler means and the beat difference signal and generating an error signal in accordance with the phase relationship therebetween; and servo means responsive to said error signal for controlling the modulation index so as to minimize the distortion component.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-02 | 1977-01-01 | 1977-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-02 | 1981-01-01 | 1981-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-02 | 1985-01-01 | 1985-07-03 | $7700.00 | Window Closed / Lapsed |