US3912858A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for the detection of signal drop-outs
Assignee: Philips North America LLC
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Filing: 1974-04-29
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Granted: 1975-10-14
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Expires: 1994-04-29
Abstract
Abstract A device for detecting small signal drop-outs in a video signal. The difference of the demodulated luminance signals of two consecutive lines is determined continually. By means of a signalling circuit the presence of a wavefore is detected which is specific for the occurrence of a signal drop-out, which signalling circuit then supplies an activating pulse for a compensation device. The device is of special importance for reading a disk-shaped record carrier in which the video signal is stored in optically coded form in a trackwise pattern of blocks and areas of variable length, because the relevant signal dropouts are likely to occur in this case.
Inventors
- 👤 George Churchill Kenney
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 05:26
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/79; H04N9/87; H04N9/88
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
294 words
A device for detecting signal dropouts in a video signal, which signal comprises a carrier which is frequency-modulated with the luminance information signal, in particular a video signal which is read from a disk-shaped record carrier on which information is stored in optically coded form in a trackwise pattern of blocks and areas of variable length, characterized in that the device includes a first delay line with a delay of one line time connected to receive said read video signal, a first demodulator circuit receiving said video signal for demodulating the luminance information signal contained in the modulated carrier, a second demodulator connected to an output of said first delay line for demodulating the luminance information signal, a substractor circuit for subtracting said demodulated luminance signal and the demodulated luminance information signal which is delayed by one line time with the aid of the first delay line from each other, a signalling circuit to which the output signal of the subtractor circuit is applied and which supplies a signalling pulse at its output if the signal applied to its input within a certain constant time interval passes through a full period of an at least approximately sinusoidal signal, an inhibiting circuit which establishes the connection between the output of the signalling circuit and the output terminal of the device, and a hold circuit whose input is connected to said output terminal and which after the appearance of a signalling pulse at said output terminal supplies a hold pulse with a delay of one line time and a duration substantially equal to that of the signalling pulse, which hold pulse is fed to a control input of the inhibiting circuit, so that during said hold pulse no furthe signalling pulse can reach the output terminal.
Claim 2
Independent Claim
294 words
A device for detecting signal dropouts in a video signal, which signal comprises a carrier which is frequency-modulated with the luminance information signal, in particular a video signal which is read from a disk-shaped record carrier on which information is stored in optically coded form in a trackwise pattern of blocks and areas of variable length, characterized in that the device includes a first delay line with a delay of one line time connected to receive said read video signal, a first demodulator circuit receiving said video signal for demodulating the luminance information signal contained in the modulated carrier, a second demodulator connected to an output of said first delay line for demodulating the luminance information signal, a substractor circuit for subtracting said demodulated luminance signal and the demodulated luminance information signal which is delayed by one line time with the aid of the first delay line from each other, a signalling circuit to which the output signal of the subtractor circuit is applied and which supplies a signalling pulse at its output if the signal applied to its input within a certain constant time interval passes through a full period of an at least approximately sinusoidal signal, an inhibiting circuit which establishes the connection between the output of the signalling circuit and the output terminal of the device, and a hold circuit whose input is connected to said output terminal and which after the appearance of a signalling pulse at said output terminal supplies a hold pulse with a delay of one line time and a duration substantially equal to that of the signalling pulse, which hold pulse is fed to a control input of the inhibiting circuit, so that during said hold pulse no furthe signalling pulse can reach the output terminal.
Claim 3
Dependent Claim
23 words
A device as claimed in claim 1, wherein the hold circuit includes a second delay line with a delay of one line time.
Claim 4
Dependent Claim
33 words
A device as claimed in claim 1, wherein the output terminal is connected to a control terminal of a signal drop-out compensation device, which receives the chrominance information of a colour television signal.
Claim 5
Dependent Claim
30 words
A device as claimed in claim 1, wherein the first delay line also forms part of a signal drop-out compensation device for the luminance signal contained in the video signal.
Claim 6
Dependent Claim
19 words
An apparatus for reading a record carrier provided with a signal drop-out detection device as claimed in claim 1.
Claim 7
Dependent Claim
52 words
A device as claimed in claim 1, wherein the signalling circuit includes a correlation circuit, in which the applied signal is continuously compared with a waveform which is stored in a memory, and a signalling pulse is supplied if the applied signal within a certain tolerance corresponds to said stored signal waveform.
Claim 8
Dependent Claim
23 words
A device as claimed in claim 6, wherein the hold circuit includes a second delay line with a delay of one line time.
Claim 9
Dependent Claim
129 words
A device as claimed in claim 1, wherein the signalling circuit includes a first threshold-value detector with a preset positive threshold value, to which the output signal of the subtractor circuit is applied and whose output is connected to a first monostable multivibrator, a second threshold-value detector with a preset negative threshold value, to which the output signal of the subtractor circuit is applied and whose output is connected to a sEcond monostable multivibrator, and a logic circuit with a first input which is connected to the output of the first monostable multivibrator and a second input which is connected to the output of the second monostable multivibrator, which logic circuit supplies a signalling pulse at its output if simultaneously a pulse appears at each of its two inputs.
Claim 10
Dependent Claim
23 words
A device as claimed in claim 8, wherein the hold circuit includes a second delay line with a delay of one line time.
Claim 11
Dependent Claim
28 words
A device as claimed in claim 8, wherein the inhibiting circuit forms part of the logic circuit and the control input constitutes an input of said logic circuit.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-13 | 1979-04-14 | 1979-10-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-13 | 1983-04-14 | 1983-10-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-13 | 1987-04-14 | 1987-10-14 | $7700.00 | Window Closed / Lapsed |