US4140903A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Precision speed control for optical scanners
Assignee: Xerox Corp
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Filing: 1977-01-03
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Granted: 1979-02-20
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Expires: 1997-01-03
Abstract
Abstract A motor speed control system for reducing instantaneous speed variations as a result of hunting in hysteresis synchronous motors utilized to drive optical scanners by controlling the drive voltage applied to the motor windings. A laser beam is reflected from the facets of the optical scanner and scans a surface along a scan line, a signal being generated at the start of each scan line. The start of scan signal is amplified and compared in a phase detector with a reference frequency corresponding to the desired optical scanner speed. The phase detector generates a voltage signal representing the phase difference between the start of scan signal and the reference frequency due to variations in the motor speed. This signal is then modulated. The resultant signal modulates the amplitude of both of the signals utilized to drive the motor field windings, the motor torque being adjusted in response to this drive signal charge whereby the hunting in the motor is effectively damped out.
Inventors
- 👤 Robert D. Clark
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 20:44
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/04; H04N1/047; H04N1/053; G; G02; G02B; G02B26/00; G02B26/08; G02B26/10; G02B26/12; G02B26/121; G02B27/00; G02B27/0025; G02B27/0031; H04N1/113; H04N1/1135; H04N1/12; H04N2201/00; H04N2201/024; H04N2201/02406; H04N2201/02439; H04N2201/04; H04N2201/047; H04N2201/04701; H04N2201/0471; H04N2201/04732; H04N2201/04744; H04N2201/04753; H04N2201/04755; H04N2201/04794
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
115 words
In an apparatus having a motor driven rotating polygon for scanning a beam of radiation across a medium in successive scans, a motor speed control system comprising: scan signal means for generating a start of scan signal; speed signal means for generating a signal representing the desired scan speed; error means for generating a signal representing the difference between said scan signal and said speed signal; drive signal means for dividing said error signal into first and second drive signals, whose magnitudes are proportional to said error signal, said signals being 90° out of phase with each other; and means for coupling said first and second drive signals to the field windings of said motor.
Claim 2
Dependent Claim
115 words
In an apparatus having a motor driven rotating polygon for scanning a beam of radiation across a medium in successive scans, a motor speed control system comprising: scan signal means for generating a start of scan signal; speed signal means for generating a signal representing the desired scan speed; error means for generating a signal representing the difference between said scan signal and said speed signal; drive signal means for dividing said error signal into first and second drive signals, whose magnitudes are proportional to said error signal, said signals being 90° out of phase with each other; and means for coupling said first and second drive signals to the field windings of said motor.
Claim 3
Dependent Claim
27 words
The system of claim 1 wherein said scan signal means comprises a photodetector positioned to receive said radiation at the beginning of each scan across said medium.
Claim 4
Dependent Claim
17 words
The system of claim 2 wherein said photodetector is positioned under a transparent portion of said medium.
Claim 5
Dependent Claim
41 words
The system of claim 1 wherein said speed signal means comprises a voltage controlled oscillator which generates a signal representing said desired scan speed, said signal being proportional to the magnitude of a voltage applied to the input of said oscillator.
Claim 6
Dependent Claim
44 words
The system of claim 4 wherein said error means comprises a phase detector which receives said scan signal and said speed signal, and generates an error signal which is fed to the input of said voltage controlled oscillator and to said drive signal means.
Claim 7
Dependent Claim
55 words
The system of claim 1 wherein said drive signal means comprises: means for applying an offset voltage to said error signal; and means for dividing said offset error signal into first and second drive signals, whose magnitudes are proportional to said offset error signal, said drive signals being 90° out of phase with each other.
Claim 8
Dependent Claim
13 words
The system of claim 1 wherein said motor is a hysteresis synchronous motor.
Claim 9
Dependent Claim
183 words
For use in an apparatus having a motor driven rotating polygon for scanning a beam of radiation across a medium in successive scans, a motor speed control system for reducing speed variations in a hysteresis synchronous motor having first and second field windings comprising: a phase detector having first and second inputs and an error signal output; means connected to said first input for generating a signal representing the start of each scan; a voltage controlled oscillator in circuit with said output and said second input of said phase detector, said oscillator generating a signal representing the desired scan speed, said signal being proportional to an error signal generated by said phase detector, said error signal being proportional to the phase difference between said scan signal and said oscillator output; drive signal means responsive to said error signal for generating first and second drive signals whose magnitudes are proportional to said error signal, said drive signals being 90° out of phase with each other; and means for applying to said first and second drive signals to said first and second field windings, respectively.
Claim 10
Dependent Claim
183 words
For use in an apparatus having a motor driven rotating polygon for scanning a beam of radiation across a medium in successive scans, a motor speed control system for reducing speed variations in a hysteresis synchronous motor having first and second field windings comprising: a phase detector having first and second inputs and an error signal output; means connected to said first input for generating a signal representing the start of each scan; a voltage controlled oscillator in circuit with said output and said second input of said phase detector, said oscillator generating a signal representing the desired scan speed, said signal being proportional to an error signal generated by said phase detector, said error signal being proportional to the phase difference between said scan signal and said oscillator output; drive signal means responsive to said error signal for generating first and second drive signals whose magnitudes are proportional to said error signal, said drive signals being 90° out of phase with each other; and means for applying to said first and second drive signals to said first and second field windings, respectively.
Claim 11
Dependent Claim
54 words
The system of claim 8 wherein said drive signal means comprises: means for applying an offset voltage to said error signal; and means for dividing said offset error signal into first and second drive signals whose magnitudes are proportional to said offset error signal, said signals being 90° out of phase with each other.
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) | 1982-02-19 | 1982-08-21 | 1983-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-02-19 | 1986-08-21 | 1987-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-02-19 | 1990-08-21 | 1991-02-20 | $7700.00 | Window Closed / Lapsed |