US4734900A
Expired / Lapsed
US
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Restoring and clocking pulse width modulated data
Assignee: International Business Machines Corp
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Filing: 1986-04-25
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Granted: 1988-03-29
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Expires: 2006-04-25
Abstract
Abstract Width restoring to eliminate unintended width variations in pulse width modulated data in combination with a phase lock loop allows pulse width modulated data in high density optical recordings. The width restoration is accomplished by detecting the timing relationship of the leading and trailing edges of pulses relative to expected timing for the leading and trailing edges. Expected time is derived from a phase locked loop or the original write signal. The detected timing is compared to the expected timing and the timing of the leading and trailing edge signals is corrected. Either analog or digital width correction techniques are used. Width restoration may be used while reading data or while writing the data.
Inventors
- 👤 Neil R. Davie
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:19
CPC Classifications
H; H03; H03M; H03M5/00; H03M5/02; H03M5/04; H03M5/06; H03M5/08; H04; H04L; H04L7/00; H04L7/02; H04L7/033; G; G11; G11B; G11B5/00; G11B5/02; G11B5/09
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
183 words
A method for clocking pulse width modulated data wherein data is represented by the timing of leading and trailing edges of pulses, the method comprising the steps of: detecting the leading edges of data pulses; detecting the trailing edges of data pulses; providing signals representative of the detected leading and trailing edges; generating a clock signal in response to the leading and trailing edge signals, said clock signal following the shifts of said edge signals, that occur in the same direction, in order to provide an expected time for the detection of said edges; comparing the timing of the signals representative of said edges with the expected time and generating a width correction signal representative of unintended width variations in the data pulses as manifested by shifts of the leading and trailing edges in opposite directions relative to the expected time provided by said clock signal; and shifting the relative timing between leading and trailing edge signals in response to the width correction signal to restore the width of the data pulses to the expected width between the leading and trailing edge signals.
Claim 2
Independent Claim
183 words
A method for clocking pulse width modulated data wherein data is represented by the timing of leading and trailing edges of pulses, the method comprising the steps of: detecting the leading edges of data pulses; detecting the trailing edges of data pulses; providing signals representative of the detected leading and trailing edges; generating a clock signal in response to the leading and trailing edge signals, said clock signal following the shifts of said edge signals, that occur in the same direction, in order to provide an expected time for the detection of said edges; comparing the timing of the signals representative of said edges with the expected time and generating a width correction signal representative of unintended width variations in the data pulses as manifested by shifts of the leading and trailing edges in opposite directions relative to the expected time provided by said clock signal; and shifting the relative timing between leading and trailing edge signals in response to the width correction signal to restore the width of the data pulses to the expected width between the leading and trailing edge signals.
Claim 3
Dependent Claim
28 words
The method of claim 1 wherein said providing step further comprises the steps of: providing a set of leading edge signals; providing a set of trailing edge signals.
Claim 4
Dependent Claim
55 words
The method of claim 2 wherein said clock generating step further comprises the steps of: detecting the phase difference between the clock signal and the leading and trailing edge signals; speeding up or slowing down the clock signal in response to the phase difference between the clock signal and the leading and trailing edge signals.
Claim 5
Dependent Claim
51 words
The method of claim 3 wherein said comparing step comprises: detecting a first phase difference between the leading edge signals and the clock signal; detecting a second phase difference between the trailing edge signals and the clock signal; combining the first and second phase differences to generate the width correction signal.
Claim 6
Dependent Claim
35 words
The method of claim 4 wherein said shifting step comprises: delaying the trailing edge signals relative to the leading edge signals; adjusting the delay in the previous step in response to the width correction signal.
Claim 7
Dependent Claim
28 words
The method of claim 4 wherein said combining step further comprises the step of: averaging the first and second phase differences over several leading and trailing edge detections.
Claim 8
Dependent Claim
188 words
In optical recording apparatus having a beam generator for generating a radiant energy beam for reading and writing pulse width modulated data on a storage medium, apparatus for correcting width distortions in the optical recorded data, said apparatus comprising: means for detecting the data recorded on the storage medium and generating a read signal indicating the pulse width modulated data recorded on the storage medium; a data signal source for providing a write signal indicative of the pulse width modulated data to be written on the storage medium; means for comparing the same pulse in the read signal and write signals, while the data is being written on the medium, and generating a width correction signal; control means in response to the width correction signal for controlling the width of the pulse in the write signal to provide a width corrected write signal; means for driving said beam generating means in response to the corrected write signal to write the pulse with a width so that the width of the read signal pulse is close to the width of the write signal pulse irrespective of recording phenomenon distortions.
Claim 9
Dependent Claim
188 words
In optical recording apparatus having a beam generator for generating a radiant energy beam for reading and writing pulse width modulated data on a storage medium, apparatus for correcting width distortions in the optical recorded data, said apparatus comprising: means for detecting the data recorded on the storage medium and generating a read signal indicating the pulse width modulated data recorded on the storage medium; a data signal source for providing a write signal indicative of the pulse width modulated data to be written on the storage medium; means for comparing the same pulse in the read signal and write signals, while the data is being written on the medium, and generating a width correction signal; control means in response to the width correction signal for controlling the width of the pulse in the write signal to provide a width corrected write signal; means for driving said beam generating means in response to the corrected write signal to write the pulse with a width so that the width of the read signal pulse is close to the width of the write signal pulse irrespective of recording phenomenon distortions.
Claim 10
Dependent Claim
55 words
The apparatus of claim 7 wherein: said detecting means generates a read signal indicating the leading and trailing edges of the data pulses; said comparing means takes the difference between the read signal and write signal indicating the difference in timing between the leading and trailing edges of the same pulse in the two signals.
Claim 11
Dependent Claim
34 words
The apparatus of claim 7 and in addition: means for averaging the differences in pulse width between the same pulses in the write and read signals in order to generate the width correction signal.
Claim 12
Dependent Claim
38 words
The apparatus of claim 9 wherein: said control means shifts one edge of the pulse being corrected to restore the width of the pulse in the read signal to the width of the pulse in the write signal.
Claim 13
Dependent Claim
26 words
The apparatus of claim 10 wherein said beam generating means is a laser and the dwell time of the laser is controlled by said control means.
Claim 14
Dependent Claim
107 words
Apparatus for restoring pulse width modulated data wherein data is represented by leading and trailing edges of pulses, the circuit comprising: first detection means for detecting the leading edges of data pulses; second detection means for detecting the trailing edges of data pulses; reference means for providing an indication of expected timing for detection of the edges; compare means coupled to the first and second detection means and to the reference means for comparing the detections of the leading and trailing edges with the indication of expected timing; and timing means coupled to the compare means for restoring the leading and trailing edges to their expected timing.
Claim 15
Dependent Claim
107 words
Apparatus for restoring pulse width modulated data wherein data is represented by leading and trailing edges of pulses, the circuit comprising: first detection means for detecting the leading edges of data pulses; second detection means for detecting the trailing edges of data pulses; reference means for providing an indication of expected timing for detection of the edges; compare means coupled to the first and second detection means and to the reference means for comparing the detections of the leading and trailing edges with the indication of expected timing; and timing means coupled to the compare means for restoring the leading and trailing edges to their expected timing.
Claim 16
Dependent Claim
55 words
The apparatus of claim 12 wherein said compare means comprise: means for measuring the time difference between the leading edge pulse transitions and their expected timing; and means for measuring the time difference between the trailing edge pulse transitions and their expected timing; and means for accumulating these differences to provide an edge correction signal.
Claim 17
Dependent Claim
30 words
The apparatus of claim 13 wherein said timing means is responsive to the edge correction signal to shift the timing of the leading or trailing edge relative to each other.
Claim 18
Dependent Claim
32 words
The apparatus of claim 12 and further comprising: writing means coupled to the timing means for writing the data pulses with leading and trailing edge separation controlled by the edge correction signal.
Claim 19
Dependent Claim
21 words
The apparatus of claim 15 wherein said reference means provides the data pulse write signal as the indication of expected timing.
Claim 20
Dependent Claim
40 words
The apparatus of claim 14 wherein said reference means comprises: phase lock clocking means for providing as the expected timing a clock signal that tracks variations in the timing of leading and trailing edge transitions shifting in the same direction.
References Cited (Backward Citations)
US4184179A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-03-29 | 1991-09-28 | 1992-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-29 | 1995-09-28 | 1996-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-29 | 1999-09-28 | 2000-03-29 | $7700.00 | Window Closed / Lapsed |