Dynamic magnetic information storage or retrieval – Record copying
Reexamination Certificate
1999-09-20
2001-01-09
Faber, Alan T. (Department: 2753)
Dynamic magnetic information storage or retrieval
Record copying
C360S031000, C369S084000, C386S349000
Reexamination Certificate
active
06172827
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for recording a signal so as to facilitate effective dropout compensation, and more particularly, to a signal recording device suitable to compensate during playback for a dropout which is generated when a signal is copied in a high-speed dubber of a dual tape deck.
2. The Background Art
Dropout indicates a phenomenon in which noise is generated on a screen by a temporary decrease in the level of, or temporary omission of a playback signal resulting from a partial damage to a recording medium, such as a scratch on a magnetic tape.
A dual tape deck, high-speed dubber, having first and second decks, copies a signal reproduced from a tape of the first deck to a tape of the second deck. When the signal is reproduced in the first deck at a speed N times higher than normal, it is also recorded at a speed N times higher than normal in the second deck. Thus, a high speed dubber can be realized in which dubbing can be performed even at an N-multiple speed. In such a high speed dubber, a luminance signal and a color signal are separately recorded when a signal output from the first deck is recorded to the second deck. A luminance-component FM signal is directly recorded, while only a frequency component of the color signal passed by a low pass filter is recorded.
FIG. 1
is a schematic view of a dropout compensator (DOC) in a general reproducing system. The DOC is comprised of a dropout detector
10
, a switching circuit
16
, a switch driver
12
, and a delay
14
for delaying a signal for one horizontal scanning period.
FIGS. 2A through 2E
illustrate the waveforms of signals used to explain the operation of the device of FIG.
1
.
FIG. 2A
illustrates the waveform of an input signal including a dropout. The dropout detector
10
detects a dropout period and generates a gate pulse during the same period as shown in FIG.
2
B. The gate pulse shown in
FIG. 2B
is completely synchronized to coincide with the dropout period of the input signal (see FIG.
2
A). The switch driver
12
, driven by the gate pulse (see FIG.
2
B),activates the switching circuit
16
during the gate pulse period. That is, the switching point of the switching circuit
16
is changed from
16
b
to
16
a
during the period the gate pulse is high.
The one horizontal scanning period delay
14
outputs a signal from a previous scan line which has been delayed for one horizontal scanning period (see FIG.
20
). Thus, by switching the switching circuit
16
the dropout is compensated to match the signal present before the one horizontal scanning period (see FIG.
2
D). The input signal of
FIG. 2A
is mixed with the compensation signal of
FIG. 2D
to form a signal free of dropout inducing noise, as shown in FIG.
2
E.
FIG. 3
is a block diagram of a conventional signal recording device. The conventional recording device has an input amplifier
200
for amplifying a small signal picked up by a head, a limiter
210
for limiting the signal output from the input amplifier
200
to be within a predetermined amplitude range, and a recording amplifier
220
for amplifying the signal output from the limiter
210
.
The operation of the conventional recording device will now be described. A playback signal picked up by the head is amplified in the input amplifier
200
, and limited to be within a predetermined amplitude range in the limiter
210
. The output signal from the limiter
210
is amplified in the recording amplifier
220
. Here, noise components during the dropout period are also amplified in the recording amplifier
220
and recorded on a recording medium.
FIGS. 4A through 4C
are a series of waveforms explaining the operation of the signal recording device shown in FIG.
3
.
FIG. 4A
is the waveform of a signal output from the input amplifier
200
, showing a dropout signal amplified along with a normal playback signal.
FIG. 4B
is a signal waveform obtained by limiting the amplitude of the amplified signal to a predetermined level in the limiter
210
. From
FIG. 4B
, it can be seen that limiting the amplitude of the normal playback signal makes it difficult to differentiate the normal playback signal from the dropout signal.
FIG. 4C
is a signal waveform recorded as described above and input to a reproducing device. This waveform shows that the dropout period cannot be identified in the input signal. That is, when the input signal is reproduced, the reproducing device treats the dropout signal in the same manner as that for the normal signal without identifying the dropout period. This results in noise appearing on a screen due to a signal recorded during the dropout period.
As described above, in case that a signal is recorded using the conventional recording device, a reproducing device performs a signal reproduction without identifying an original dropout period in the input signal during playback, thereby generating noise due to a signal reproduced during the dropout period.
SUMMARY OF THE INVENTION
To circumvent the above problems, an object of the present invention is to provide a signal recording device which mutes a dropout portion of a signal during recording so as to enable effective compensation for the original dropout during playback.
To achieve the above object, there is provided a device for recording a signal so as to facilitate effective dropout compensation. The device includes a means for inputting a signal to be recorded on a recording medium; means for detecting a dropout portion of a signal output from said signal inputting means and generating a pulse signal corresponding to said detected dropout portion; means for muting the signal output from said signal inputting means during said pulse signal period; and means for recording on a recording medium, a signal output from said signal muting means during said pulse signal period and a signal output from said signal inputting means during other times.
REFERENCES:
patent: 4811122 (1989-03-01), Kido et al.
patent: 5057934 (1991-10-01), Yun
patent: 5103349 (1992-04-01), Sochor
patent: 5194963 (1993-03-01), Dunlap et al.
patent: 5469306 (1995-11-01), Hara
patent: 5761370 (1998-06-01), Kim
Faber Alan T.
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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