US4672618A
Expired / Lapsed
US
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Laser stabilization servo system
Assignee: Beckman Coulter Inc
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Filing: 1986-07-09
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Granted: 1987-06-09
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Expires: 2006-07-09
Abstract
Abstract A method and means for stabilizing the difference in frequencies between the frequency components of a two frequency laser beam influenced by Zeeman effect frequency splitting, accurately determines the frequency separation independently of the individual frequencies or intensities of either of the frequency components. Frequency stabilization is accomplished by mechanical and thermal adjustments to the lasing chamber length of the laser by a closed loop servo control referencing the frequency difference between laser beam components and a reference signal having a frequency equal to the desired frequency difference.
Inventors
- 👤 Geert Wijntjes
- 👤 Michael Hercher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:28
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/13; H01S3/139; H01S3/1396
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
252 words
A closed loop feedback control for a laser having an excited lasing material contained within an adjustable length chamber producing a laser beam, and influenced by a magnetic field to obtain two component modes of differing frequency in said laser beam, said feedback control controls the frequency difference between said component modes comprising: a first means for heterodyne mixing said component modes to obtain an electrical signal characterized by a beat frequency generated by mixing the frequencies of said component modes and representing the difference in frequency between the component modes; a second means for producing a reference signal having a frequency characteristic of a desired beat frequency signal; a third means, receiving said electrical signal from said first means and said reference signal from said second means, for comparing the phase between said electrical signal and said reference signal to determine a difference in Phase, and producing an error signal responsive to the difference in phase between said signals with respect to time; and control means responsive to said error signal for changing the length of said laser chamber to obtain a controlled frequency difference between said component modes in said laser beam, which component modes produce when heterodyned by said first means an electrical a beat signal having a frequency which is locked in phase with the frequency of said reference signal to determine said frequency difference between component modes; whereby said beat signal becomes phase locked to said reference signal to determine said frequency difference between the component modes.
Claim 2
Dependent Claim
252 words
A closed loop feedback control for a laser having an excited lasing material contained within an adjustable length chamber producing a laser beam, and influenced by a magnetic field to obtain two component modes of differing frequency in said laser beam, said feedback control controls the frequency difference between said component modes comprising: a first means for heterodyne mixing said component modes to obtain an electrical signal characterized by a beat frequency generated by mixing the frequencies of said component modes and representing the difference in frequency between the component modes; a second means for producing a reference signal having a frequency characteristic of a desired beat frequency signal; a third means, receiving said electrical signal from said first means and said reference signal from said second means, for comparing the phase between said electrical signal and said reference signal to determine a difference in Phase, and producing an error signal responsive to the difference in phase between said signals with respect to time; and control means responsive to said error signal for changing the length of said laser chamber to obtain a controlled frequency difference between said component modes in said laser beam, which component modes produce when heterodyned by said first means an electrical a beat signal having a frequency which is locked in phase with the frequency of said reference signal to determine said frequency difference between component modes; whereby said beat signal becomes phase locked to said reference signal to determine said frequency difference between the component modes.
Claim 3
Dependent Claim
65 words
The feedback control of claim 1 wherein said first means comprises a polarizer for receiving said laser beam and interfering common linearly polarized components of said component modes, to produce a heterodyned light beam having a beat frequency representing the difference in frequency between said component modes, and a photodetector for receiving said heterodyned beam to generate an electrical signal representing said heterodyned light beam.
Claim 4
Dependent Claim
38 words
The feedback control of claim 1 wherein said third means comprises a phase detector and an integrator, which generate an error signal proportional to the integral of differences in phase between said beat signal and said reference signal.
Claim 5
Dependent Claim
72 words
The feedback control of claim 1 wherein said control means responsive to said error signal comprises: a first means for adjusting length of said chamber which quickly changes chamber length over a limited distal range; and a second means for adjusting chamber length over a wide distal range; said first and second means cooperating to adjust said chamber length and maintain said first means in a median portion of its distal range.
Claim 6
Dependent Claim
64 words
The feedback control of claim 1 wherein said control means responsive to said error signal comprises a piezoelectric transducer responsive to said error signal, an operational amplifier responsive to said error signal for producing an output current signal, and a thermally expandable element responsive to said current signal, which change the length of said laser chamber in response to changes in said error signal.
Claim 7
Dependent Claim
240 words
A closed loop servo control system for tuning the length of a leasing chamber to control the difference in frequency between two component modes of a Zeeman split laser beam comprising: a reference clock producing a constant frequency reference signal; means for generating a hetrodyne beat signal, having a beat pulse frequency equalling the difference in frequency of said component modes; a phase detector receiving said reference signal and said beat signal, said detector producing an output signal having a voltage proportional to the phase difference between said reference and said beat signals; an integrator receiving said phase detector output signal, for summing said output signals of said phase detector and producing a signed error signal proportional to the integrated phase difference of said reference and beat signals, the sign of said error signal indicating a lead or lag in phase of said beat signal relative to said reference signal; a first means for changing said laser chamber length, said means responsive to said error signal voltage within a limited range for fast micro adjustments to said length of said lasing chamber; reference voltage source producing a reference voltage signal equal to the voltage required by said first means to obtain a medium position in said limited movement range; an operational amplifier receiving said error signal and said reference voltage signal, said amplifier producing a current signal responsive to a difference in said error signal and said reference voltage signal;
Claim 8
Dependent Claim
240 words
A closed loop servo control system for tuning the length of a leasing chamber to control the difference in frequency between two component modes of a Zeeman split laser beam comprising: a reference clock producing a constant frequency reference signal; means for generating a hetrodyne beat signal, having a beat pulse frequency equalling the difference in frequency of said component modes; a phase detector receiving said reference signal and said beat signal, said detector producing an output signal having a voltage proportional to the phase difference between said reference and said beat signals; an integrator receiving said phase detector output signal, for summing said output signals of said phase detector and producing a signed error signal proportional to the integrated phase difference of said reference and beat signals, the sign of said error signal indicating a lead or lag in phase of said beat signal relative to said reference signal; a first means for changing said laser chamber length, said means responsive to said error signal voltage within a limited range for fast micro adjustments to said length of said lasing chamber; reference voltage source producing a reference voltage signal equal to the voltage required by said first means to obtain a medium position in said limited movement range; an operational amplifier receiving said error signal and said reference voltage signal, said amplifier producing a current signal responsive to a difference in said error signal and said reference voltage signal;
Claim 9
Dependent Claim
26 words
a second means for controlling said lasing chamber length, said means responsive to said current signal for macro adjustments to said length of said lasing chamber.
Claim 10
Dependent Claim
26 words
a second means for controlling said lasing chamber length, said means responsive to said current signal for macro adjustments to said length of said lasing chamber.
Claim 11
Dependent Claim
116 words
A servo control system for tuning a magnetically influenced split laser to generate component modes of a laser beam having a constant difference in frequency comprising: clock means for generating a reference clock signal; means for heterodyning said component modes of said laser beam to obtain a beat signal; sensor means for comparing the phase relationship of said reference signal and said beat signal, and generating an error signal; tuning means for controlling the frequency difference of said component modes of said laser output beam in response to said error signal; and control means for synchronizing the phase of said beat signal with said reference signal to determine the difference in frequency between said component modes.
Claim 12
Dependent Claim
116 words
A servo control system for tuning a magnetically influenced split laser to generate component modes of a laser beam having a constant difference in frequency comprising: clock means for generating a reference clock signal; means for heterodyning said component modes of said laser beam to obtain a beat signal; sensor means for comparing the phase relationship of said reference signal and said beat signal, and generating an error signal; tuning means for controlling the frequency difference of said component modes of said laser output beam in response to said error signal; and control means for synchronizing the phase of said beat signal with said reference signal to determine the difference in frequency between said component modes.
Claim 13
Independent Claim
149 words
A method of stabilizing the difference in frequencies of the component modes of a laser beam generated in an adjustable lasing chamber influenced by a magnetic field to obtain Zeeman splitting, comprising, heterodyne mixing the component modes of said beam to obtain an electromagnetic heterodyne wave having a beat frequency equal to said difference in component mode frequencies; generating an electrical signal having a beat frequency equivalent to the beat frequency of said heterodyned wave; comparing the phase between said electrical signal and a reference signal having a selected frequency characteristic of the desired beat frequency, to determine a difference in phase; adjusting said lasing chamber length in response to the difference in phase between the heterodyned signal and the reference signal, to bring the signals into phase; maintaining said heterodyned signal and said reference signal locked in phase by instantaneous adjustment in the length of said lasing chamber.
Claim 14
Independent Claim
149 words
A method of stabilizing the difference in frequencies of the component modes of a laser beam generated in an adjustable lasing chamber influenced by a magnetic field to obtain Zeeman splitting, comprising, heterodyne mixing the component modes of said beam to obtain an electromagnetic heterodyne wave having a beat frequency equal to said difference in component mode frequencies; generating an electrical signal having a beat frequency equivalent to the beat frequency of said heterodyned wave; comparing the phase between said electrical signal and a reference signal having a selected frequency characteristic of the desired beat frequency, to determine a difference in phase; adjusting said lasing chamber length in response to the difference in phase between the heterodyned signal and the reference signal, to bring the signals into phase; maintaining said heterodyned signal and said reference signal locked in phase by instantaneous adjustment in the length of said lasing chamber.
Claim 15
Dependent Claim
113 words
A phase lock servo control loop for controlling the difference in frequency between component modes of a Zeeman split laser beam comprising: means for generating a heterodyne signal having a beat frequency equal to the difference in component mode frequencies; a reference clock for generating a constant frequency signal, said frequency equalling the desired frequency of the beat in said heterodyned signal; a phase comparator for comparing the phase of said heterodyne signal and said reference signal, and generating a phase difference signal proportional to the phase difference in said signals; an integrator for summing incremental changes in said phase difference signal, and generating an error signal proportional to the summation of changes;
Claim 16
Dependent Claim
113 words
A phase lock servo control loop for controlling the difference in frequency between component modes of a Zeeman split laser beam comprising: means for generating a heterodyne signal having a beat frequency equal to the difference in component mode frequencies; a reference clock for generating a constant frequency signal, said frequency equalling the desired frequency of the beat in said heterodyned signal; a phase comparator for comparing the phase of said heterodyne signal and said reference signal, and generating a phase difference signal proportional to the phase difference in said signals; an integrator for summing incremental changes in said phase difference signal, and generating an error signal proportional to the summation of changes;
Claim 17
Dependent Claim
17 words
means for controlling the difference in frequency between the two component modes responsive to said error signal.
Claim 18
Dependent Claim
17 words
means for controlling the difference in frequency between the two component modes responsive to said error signal.
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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) | 1990-06-08 | 1990-12-08 | 1991-06-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-08 | 1994-12-08 | 1995-06-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-08 | 1998-12-08 | 1999-06-09 | $7700.00 | Window Closed / Lapsed |