US3733129A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Laser distance detector
Assignee: Raytheon Co
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Filing: 1971-02-01
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Granted: 1973-05-15
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Expires: 1991-02-01
Abstract
Abstract A system utilizing a laser for accurately measuring range from a first position to a second position by providing a laser cavity having a reflective mirror at the first position and a target as the reflective mirror at the second position, and by detecting the occurrence of an induced optical mode locking condition in the laser cavity. The system phase modulates the energy in the cavity at a swept modulation frequency with the amplitude of the intermode beats or differences being detected to determine the effective length of the cavity. At phase modulation frequencies near c/2l (c is the velocity of light in the medium and is the length of the cavity) mode locking occurs in such phase relations that the beat signal appears to be a pure FM signal with a relatively small amplitude and at phase modulation frequencies at c/2l a different type of mode locking produces a large amplitude signal, either of which conditions may be utilized to provide a scaled value of l or range.
Inventors
- 👤 W Bridges
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 00:23
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/106; H01S3/107; G; G01; G01S; G01S17/00; G01S17/02; G01S17/06; G01S17/08; G01S17/32; G01S17/34
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
101 words
A ranger for measuring range to an object comprising a laser having an amplifying element and a reflective element positioned to provide a reflective path to said object, said reflective element and said object forming a cavity capable of supporting modes with a plurality of axial mode indices, modulating means for phase modulating the energy in said cavity, detecting means responsive to selected beat notes developed in said cavity for providing a signal representative of mode locking in said cavity, and means responsive to said detecting means and said modulating means for indicating range from said reflective element to said object.
Claim 2
Dependent Claim
101 words
A ranger for measuring range to an object comprising a laser having an amplifying element and a reflective element positioned to provide a reflective path to said object, said reflective element and said object forming a cavity capable of supporting modes with a plurality of axial mode indices, modulating means for phase modulating the energy in said cavity, detecting means responsive to selected beat notes developed in said cavity for providing a signal representative of mode locking in said cavity, and means responsive to said detecting means and said modulating means for indicating range from said reflective element to said object.
Claim 3
Dependent Claim
77 words
The combination of claim 1 in which said modulating means is capable of phase modulating the energy at a frequency c/2l to provide a mode locking condition where c is the velocity of light in the cavity and l is the range from said reflective element to said object, and in which said means is responsive to said detecting means and responds to the signal from said detecting means falling in amplitude at said mode locking condition.
Claim 4
Dependent Claim
63 words
The combination of claim 1 in which the modulating means provides phase modulation over a selected frequency range and said means responsive to said detecting means is coupled to said modulating means and includes threshold detecting means and scale conversion means for responding to the modulating frequencies at the condition of mode locking in said cavity to develop a signal representative of range.
Claim 5
Independent Claim
146 words
A system for measuring range from a first position to a target surface, said system comprising a reflective element at said first position pointed to define a laser cavity with the target surface, said cavity being capable of supporting a plurality of modes each with a different axial mode index, an amplifying medium for providing multimode operation, a phase modulator positioned to modulate the signals in said cavity, swept oscillator means coupled to said phase modulator for modulating the phase of the signals in said cavity at a frequency that is a function of range, detecting means responsive to beat signals developed in said cavity to provide a detected signal representative of the beat signal amplitude, and means responsive to said detecting means for determining a mode locking condition and scaling the modulating frequency of said swept oscillator means to provide a signal representative of range.
Claim 6
Independent Claim
146 words
A system for measuring range from a first position to a target surface, said system comprising a reflective element at said first position pointed to define a laser cavity with the target surface, said cavity being capable of supporting a plurality of modes each with a different axial mode index, an amplifying medium for providing multimode operation, a phase modulator positioned to modulate the signals in said cavity, swept oscillator means coupled to said phase modulator for modulating the phase of the signals in said cavity at a frequency that is a function of range, detecting means responsive to beat signals developed in said cavity to provide a detected signal representative of the beat signal amplitude, and means responsive to said detecting means for determining a mode locking condition and scaling the modulating frequency of said swept oscillator means to provide a signal representative of range.
Claim 7
Dependent Claim
17 words
The combination of claim 4 further including telescope means in said cavity for increasing the cavity Gain.
Claim 8
Independent Claim
120 words
A system for measuring range to an object comprising a laser amplifying element and a reflective element having a reflective surface positioned for forming in a single path a laser cavity with said object, said cavity supporting a plurality of axial modes, first means coupled to said cavity for phase modulating the energy in said cavity at a frequency range including c/2l where c is the velocity of light and l is the length of said cavity, and second means for detecting beat note signals in said cavity and sensing cavity mode locking at the modulating frequency c/2l, and coupled to said first means for providing a signal representative of the cavity length l representative of range to the target.
Claim 9
Independent Claim
120 words
A system for measuring range to an object comprising a laser amplifying element and a reflective element having a reflective surface positioned for forming in a single path a laser cavity with said object, said cavity supporting a plurality of axial modes, first means coupled to said cavity for phase modulating the energy in said cavity at a frequency range including c/2l where c is the velocity of light and l is the length of said cavity, and second means for detecting beat note signals in said cavity and sensing cavity mode locking at the modulating frequency c/2l, and coupled to said first means for providing a signal representative of the cavity length l representative of range to the target.
Claim 10
Dependent Claim
38 words
The combination of claim 6 in which said second means includes a threshold detector for detecting a rise in amplitude of said beat note signals as a condition for providing the signal representative of the cavity length l.
Claim 11
Independent Claim
177 words
A system for measuring range to an object comprising a reflective element positioned with a path to said object for forming a laser cavity with said object, an amplifying element positioned in said cavity, said cavity supporting a plurality of modes each with a different axial mode index, modulating means for phase modulating the energy in said cavity, a swept oscillator coupled to said modulating means for providing a phase modulation over a frequency excursion including a mode locking frequency, photomultiplier means responsive to the difference signals in said cavity, tracking means coupled to said photomultiplier for passing the difference signals in a frequency range at said mode locking frequency, envelope detecting means coupled to said tracking means for developing a signal representative of the amplitude of the difference signals passed by said tracking means, threshold detecting means coupled to said envelope detecting means for providing a signal representative of said mode locking condition, and output means coupled to said threshold detecting means and said swept oscillator for providing a signal representative of range to said object.
Claim 12
Independent Claim
177 words
A system for measuring range to an object comprising a reflective element positioned with a path to said object for forming a laser cavity with said object, an amplifying element positioned in said cavity, said cavity supporting a plurality of modes each with a different axial mode index, modulating means for phase modulating the energy in said cavity, a swept oscillator coupled to said modulating means for providing a phase modulation over a frequency excursion including a mode locking frequency, photomultiplier means responsive to the difference signals in said cavity, tracking means coupled to said photomultiplier for passing the difference signals in a frequency range at said mode locking frequency, envelope detecting means coupled to said tracking means for developing a signal representative of the amplitude of the difference signals passed by said tracking means, threshold detecting means coupled to said envelope detecting means for providing a signal representative of said mode locking condition, and output means coupled to said threshold detecting means and said swept oscillator for providing a signal representative of range to said object.
Claim 13
Dependent Claim
12 words
The combination of claim 8 further including telescope means in said cavity.
Claim 14
Dependent Claim
28 words
The combination of claim 8 in which said threshold detecting means responds to the signal from said envelope detecting means falling in amplitude over a predetermined time interval.
Claim 15
Dependent Claim
25 words
The combination of claim 10 with said output means including a bias correction means for correcting change as a function of said predetermined time interval.
Claim 16
Dependent Claim
26 words
The combination of claim 8 in which said threshold detecting means senses a substantial rise in amplitude of the signal developed by said envelope detecting means.
Claim 17
Dependent Claim
28 words
The combination of claim 8 in which range selection means are coupled to said swept oscillator for selecting different phase modulation frequency excursions representative of different range intervals.
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) | 1976-05-14 | 1976-11-13 | 1977-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-14 | 1980-11-13 | 1981-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-14 | 1984-11-13 | 1985-05-15 | $7700.00 | Window Closed / Lapsed |