US5815250A
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US
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Doublet pulse coherent laser radar for precision range and velocity measurements
Assignee: Lockheed Martin Coherent Technologies Inc
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Filing: 1997-05-27
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Granted: 1998-09-29
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Expires: 2017-05-27
Abstract
Abstract In a laser radar (lidar) system, a Doublet Pulse is generated by injection-seeded aborted cavity dumping of a solid-state laser. The doublet pulse provides coherent Doppler lidar systems a substantial time bandwidth product (TB) with a very modest processing requirement. The waveform format comprises a pair of pulselets, each of duration τ, separated by T seconds. The range resolution is governed by the pulselet duration τ, while the velocity precision is governed by one over the pulselet separation, T. Ambiguities in the velocity measurement arise as a result of the periodic structure of the waveform and occur every λ/2T m/sec, where λ is the operating wavelength. These ambiguities are removed by conventional de-aliasing algorithms as well as through the generation and processing of higher order pulse waveforms.
Inventors
- 👤 J. Alex Thomson
- 👤 Stephen M. Hannon
- 👤 Sammy W. Henderson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 05:08
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/10084; H01S3/10092; G; G01; G01S; G01S17/00; G01S17/02; G01S17/06; G01S17/08; G01S17/10; G01S17/50; G01S7/00; G01S7/48; G01S7/483; G01S7/484; G01S7/497; H01S3/11; H01S3/1103; H01S3/14; H01S3/16; H01S3/1601; H01S3/1603; H01S3/1616
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
151 words
A system for determining a range and velocity of a distant object, the system comprising: a laser for creating a doublet pulse waveform of coherent light, wherein the doublet pulse waveform comprises two pulses; at least one optical element connected to the laser for directing the double pulse waveform toward the distant object and for receiving a reflected doublet pulse waveform returned from the distant object; a detector circuit connected to the optical element for detecting the reflected doublet pulse waveform; a time delay measuring circuit connected to the detector circuit for measuring a time delay between the doublet pulse waveform and the reflected doublet pulse waveform wherein the time delay defines the range of the distant object; a phase measuring circuit for measuring a phase difference between first and second pulses in the reflected doublet pulse waveform, and for determining the velocity of the distant object from the phase difference.
Claim 2
Independent Claim
151 words
A system for determining a range and velocity of a distant object, the system comprising: a laser for creating a doublet pulse waveform of coherent light, wherein the doublet pulse waveform comprises two pulses; at least one optical element connected to the laser for directing the double pulse waveform toward the distant object and for receiving a reflected doublet pulse waveform returned from the distant object; a detector circuit connected to the optical element for detecting the reflected doublet pulse waveform; a time delay measuring circuit connected to the detector circuit for measuring a time delay between the doublet pulse waveform and the reflected doublet pulse waveform wherein the time delay defines the range of the distant object; a phase measuring circuit for measuring a phase difference between first and second pulses in the reflected doublet pulse waveform, and for determining the velocity of the distant object from the phase difference.
Claim 3
Dependent Claim
73 words
The system of claim 1 wherein the laser further comprises: an acousto-optic modulator for q-switching the laser; and an electro-optic modulator for detecting power within the laser and for dumping a cavity within the laser to produce a first pulse of the doublet pulse waveform upon reaching a predetermined power level, and for dumping the cavity a second time after a predetermined delay to produce the second pulse of the doublet pulse waveform.
Claim 4
Dependent Claim
30 words
The system of claim 1 wherein the laser further comprises: an acousto-optic modulator for q-switching the laser twice to create the first and second pulses of the doublet pulse waveform.
Claim 5
Dependent Claim
16 words
The system of claim 1 further comprising a second laser connected to injection seed the laser.
Claim 6
Dependent Claim
17 words
The system of claim 1 wherein the laser further comprises means for creating more than two pulses.
Claim 7
Dependent Claim
18 words
The system of claim 5 wherein the means for creating the more than two pulses comprises repetitive q-switching.
Claim 8
Dependent Claim
200 words
The system of claim 5 wherein the phase measuring circuit further comprises: means for determining a plurality of phase differences, one difference between a monitor signal of each of the more than two pulses created, and a return signal corresponding to each of the more than two pulses created; means for accumulating a plurality of phase errors between a phase difference of a first of the more that two pulses created, and a phase difference of each of the more that two pulses created after the first of the more than two pulses created, wherein each phase difference is modified by a time difference between the transmission of the pulse and one of a set of predicted velocities, to create a plurality of phase error values, one phase error value for each combination of a phase difference of one of the more that two pulses and one of the set of predicted velocities; means for accumulating the phase error values for each one of the set of predicted velocities to create accumulated phase error values; and means for selecting the velocity as the predicted velocity of the accumulated phase error value that is a minimum of the phase error values.
Claim 9
Dependent Claim
87 words
The system of claim 7 wherein the means for determining a plurality of phase differences further comprises means for determining the phase difference between a monitor signal of each pulselet after the first of the more than two pulselets created, and a return signal corresponding to each pulselet after the first of the more than two pulselets created, by altering the phase difference by the time difference between the pulselet being altered and the first pulselet and further altering the phase difference by a hypothesized target velocity.
Claim 10
Dependent Claim
35 words
The system of claim 1 wherein the laser further comprises means for creating a second of the two pulses having a polarization state orthogonal to a polarization state of a first of the two pulses.
Claim 11
Dependent Claim
132 words
The system of claim 9 wherein the means for creating the second of the two pulses having a polarization state orthogonal to a polarization state of a first of the two pulses comprises: a first polarizer that splits a pulse created by the laser into first and second pulses and directs the first pulse into a first optical path and directs the second into a second optical path; an optical delay line that delays the first pulse in the first optical path a predetermined amount of time; a second polarizer that combines the first pulse from the first optical path with the second pulse from the second optical path at a location beyond the optical delay line to create the double pulse waveform wherein the first and second pulselets have orthogonal polarization.
Claim 12
Dependent Claim
63 words
the system of claim 1 wherein the phase measuring circuit further comprises: a transmit correlation circuit for creating a transmit phase map of the transmitted pulses; a receive correlation circuit for creating a receive phase map of the received pulses; and a filter circuit for creating a conjugate product of the transmit phase map and the receive phase map to determine the velocity.
Claim 13
Independent Claim
207 words
A system for determining a range and velocity of a distant object, the system comprising: a laser for creating a doublet pulse waveform of coherent light, wherein the doublet pulse waveform comprises two pulses; at least one optical element connected to the laser for directing the double pulse waveform toward the distant object and for receiving a reflected doublet pulse waveform returned from the distant object; a detector circuit connected to the optical element for detecting the reflected doublet pulse waveform; a time delay measuring circuit connected to the detector circuit for measuring a time delay between the doublet pulse waveform and the reflected doublet pulse waveform wherein the time delay defines the range of the distant object; a phase measuring circuit for measuring a phase difference between first and second pulses in the reflected doublet pulse waveform, and for determining the velocity of the distant object from the phase difference, the phase measuring circuit comprising a transmit correlation circuit for creating a transmit phase map of the transmitted pulses, a receive correlation circuit for creating a receive phase map of the received pulses, and a filter circuit for creating a conjugate product of the transmit phase map and the receive phase map to determine the velocity.
Claim 14
Independent Claim
207 words
A system for determining a range and velocity of a distant object, the system comprising: a laser for creating a doublet pulse waveform of coherent light, wherein the doublet pulse waveform comprises two pulses; at least one optical element connected to the laser for directing the double pulse waveform toward the distant object and for receiving a reflected doublet pulse waveform returned from the distant object; a detector circuit connected to the optical element for detecting the reflected doublet pulse waveform; a time delay measuring circuit connected to the detector circuit for measuring a time delay between the doublet pulse waveform and the reflected doublet pulse waveform wherein the time delay defines the range of the distant object; a phase measuring circuit for measuring a phase difference between first and second pulses in the reflected doublet pulse waveform, and for determining the velocity of the distant object from the phase difference, the phase measuring circuit comprising a transmit correlation circuit for creating a transmit phase map of the transmitted pulses, a receive correlation circuit for creating a receive phase map of the received pulses, and a filter circuit for creating a conjugate product of the transmit phase map and the receive phase map to determine the velocity.
Claim 15
Dependent Claim
73 words
The system of claim 12 wherein the laser further comprises: an acousto-optic modulator for q-switching the laser; and an electro-optic modulator for detecting power within the laser and for dumping a cavity within the laser to produce a first pulse of the doublet pulse waveform upon reaching a predetermined power level, and for dumping the cavity a second time after a predetermined delay to produce the second pulse of the doublet pulse waveform.
Claim 16
Dependent Claim
30 words
The system of claim 12 wherein the laser further comprises: an acousto-optic modulator for q-switching the laser twice to create the first and second pulses of the doublet pulse waveform.
Claim 17
Dependent Claim
16 words
The system of claim 12 further comprising a second laser connected to injection seed the laser.
Claim 18
Dependent Claim
17 words
The system of claim 12 wherein the laser further comprises means for creating more than two pulses.
Claim 19
Dependent Claim
19 words
The system of claim 16 wherein the means for creating the more than two pulses comprises repetitive q-switching means.
Claim 20
Dependent Claim
200 words
The system of claim 16 wherein the phase measuring circuit further comprises: means for determining a plurality of phase differences, one difference between a monitor signal of each of the more than two pulses created, and a return signal corresponding to each of the more than two pulses created; means for accumulating a plurality of phase errors between a phase difference of a first of the more that two pulses created, and a phase difference of each of the more that two pulses created after the first of the more than two pulses created, wherein each phase difference is modified by a time difference between the transmission of the pulse and one of a set of predicted velocities, to create a plurality of phase error values, one phase error value for each combination of a phase difference of one of the more that two pulses and one of the set of predicted velocities; means for accumulating the phase error values for each one of the set of predicted velocities to create accumulated phase error values; and means for selecting the velocity as the predicted velocity of the accumulated phase error value that is a minimum of the phase error values.
Claim 21
Dependent Claim
87 words
The system of claim 18 wherein the means for determining a plurality of phase differences further comprises means for determining the phase difference between a monitor signal of each pulselet after the first of the more than two pulselets created, and a return signal corresponding to each pulselet after the first of the more than two pulselets created, by altering the phase difference by the time difference between the pulselet being altered and the first pulselet and further altering the phase difference by a hypothesized target velocity.
Claim 22
Dependent Claim
35 words
The system of claim 12 wherein the laser further comprises means for creating a second of the two pulses having a polarization state orthogonal to a polarization state of a first of the two pulses.
Claim 23
Dependent Claim
132 words
The system of claim 20 wherein the means for creating the second of the two pulses having a polarization state orthogonal to a polarization state of a first of the two pulses comprises: a first polarizer that splits a pulse created by the laser to create first and second pulses directs the first pulse into a first optical path and directs the second into a second optical path; an optical delay line that delays the first pulse in the first optical path a predetermined amount of time; a second polarizer that combines the first pulse from the first optical path with the second pulse from the second optical path at a location beyond the optical delay line to create the double pulse waveform wherein the first and second pulselets have orthogonal polarization.
Claim 24
Independent Claim
119 words
A method for determining a range and velocity of a distant object, the method comprising the steps of: (a) creating a doublet pulse waveform of coherent light, wherein the doublet pulse waveform comprises two pulses; (b) directing the double pulse waveform toward the distant object; (c) receiving a reflected doublet pulse waveform returned from the distant object; (d) detecting the reflected doublet pulse waveform; (e) measuring a time delay between the doublet pulse waveform and the reflected doublet pulse waveform wherein the time delay defines the range of the distant object; (f) measuring a phase difference between first and second pulses in the reflected doublet pulse waveform, and determining the velocity of the distant object from the phase difference.
Claim 25
Independent Claim
119 words
A method for determining a range and velocity of a distant object, the method comprising the steps of: (a) creating a doublet pulse waveform of coherent light, wherein the doublet pulse waveform comprises two pulses; (b) directing the double pulse waveform toward the distant object; (c) receiving a reflected doublet pulse waveform returned from the distant object; (d) detecting the reflected doublet pulse waveform; (e) measuring a time delay between the doublet pulse waveform and the reflected doublet pulse waveform wherein the time delay defines the range of the distant object; (f) measuring a phase difference between first and second pulses in the reflected doublet pulse waveform, and determining the velocity of the distant object from the phase difference.
Claim 26
Dependent Claim
71 words
The method of claim 22 wherein step (a) further comprises the steps of: (a1) q-switching the laser; and (a2) detecting a power level within the laser; (a3) dumping a cavity within the laser to produce a first pulse of the doublet pulse waveform upon reaching a predetermined power level; and (a4) dumping the cavity a second time after a predetermined delay to produce the second pulse of the doublet pulse waveform.
Claim 27
Dependent Claim
30 words
The method of claim 22 wherein step (a) further comprises the step of: (a1) q-switching the laser twice to create the first and second pulses of the doublet pulse waveform.
Claim 28
Dependent Claim
22 words
The method of claim 22 wherein step (a) further comprises the step of: (a1) injection seeding to create the doublet pulse waveform.
Claim 29
Dependent Claim
19 words
The method of claim 22 wherein step (a) further comprises the step of: (a1) creating more than two pulses.
Claim 30
Dependent Claim
23 words
The method of claim 26 wherein step (a1) further comprises the step of: (a1A) creating the more than two pulses by repetitive q-switching.
Claim 31
Dependent Claim
197 words
The method of claim 26 wherein step (a1) further comprises the steps of: (a1A) determining a plurality of phase differences, one difference between a monitor signal of each of the more than two pulses created, and a return signal corresponding to each of the more than two pulses created; (a1B) accumulating a plurality of phase errors between a phase difference of a first of the more that two pulses created, and a phase difference of each of the more that two pulses created after the first of the more than two pulses created, wherein each phase difference is modified by a time difference between the transmission of the pulse and one of a set of predicted velocities, to create a plurality of phase error values, one phase error value for each combination of a phase difference of one of the more that two pulses and one of the set of predicted velocities; (a1C) accumulating the phase error values for each one of the set of predicted velocities to create accumulated phase error values; and (a1D) selecting the velocity as the predicted velocity of the accumulated phase error value that is a minimum of the phase error values.
Claim 32
Dependent Claim
83 words
The method of claim 28 wherein the step (a1a) further comprises the steps of: (a1A1) determining the phase difference between a monitor signal of each pulselet after the first of the more than two pulselets created, and a return signal corresponding to each pulselet after the first of the more than two pulselets created, by altering the phase difference by the time difference between the pulselet being altered and the first pulselet and further altering the phase difference by a hypothesized target velocity.
Claim 33
Dependent Claim
37 words
The method of claim 22 wherein step (a) further comprises the step of: (a1) creating a second of the two pulses with a polarization state orthogonal to a polarization state of a first of the two pulses.
Claim 34
Dependent Claim
96 words
The method of claim 30 wherein step (a1) comprises the steps of: (a1A) splitting a pulse created by the laser into first and second pulses and directing the first into a first optical path and directing the second pulse into a second optical path; (a1B) delaying the first pulse in the first optical path a predetermined amount of time; (a1C) combining the first pulse in the first optical path with the second pulse in the second optical path after the delaying to create the double pulse waveform wherein the first and second pulselet have orthogonal polarization.
Claim 35
Dependent Claim
53 words
The method of claim 22 wherein step (f) further comprises the steps of: (f1) creating a transmit phase map of the transmitted pulses; (f2) creating a receive phase map of the received pulses; and (f3) creating a conjugate product of the transmit phase map and the receive phase map to determine the velocity.
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) | 2001-09-28 | 2002-03-30 | 2002-09-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-09-28 | 2006-03-30 | 2006-09-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-09-28 | 2010-03-30 | 2010-09-29 | $7700.00 | Window Closed / Lapsed |