Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-08-28
2002-02-19
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06349011
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording reproducing apparatus, and more particularly, relates to a tracking system which performs automatic tracking by dividing one track into a plurality of minute blocks, and an automatic tracking method.
2. Discussion of Related Art
A video cassette recorder (VCR) is an apparatus recording video signals on magnetic tape, and has a deck part connected to an electrical part. The standard of the tape and the standard of the recorded signals are strictly provided for compatibility between different VCRs. Especially, the standard of the track linearity is used for the compatibility of VCRs. The width of track for high density recording becomes gradually narrow and determining the optimum tracking point is very important. Thus, as a tape is inserted into a deck, the VCR performs automatic tracking. The user may select either manual or autocontrol, as desired. The autocontrol uses the envelope of a regenerative signal. That is, according to the automatic tracking, the optimum tracking point is automatically determined and maintained as the tape is inserted into the VCR.
The overall flowchart of the automatic tracking is shown in FIG.
1
.
As the tape is input to the VCR (Step
101
), it goes to a regenerating state (Step
102
), and offsetting of the VCR head is performed (Step
103
). The output RF signal is filtrated to digitalize the envelope signal (Step
104
. The tracking is controlled with a digital value converted in the Step
104
, thus finding a tracking value (Step
105
). If the tracking value obtained in the Step
105
is not a proper value, it goes to the Step
103
and performs the above procedure. If the proper tracking value is obtained in the Step
105
(Step
106
), the track offsetting stops and the tracking value obtained in the Step
105
is maintained.
FIG. 2
is a block diagram of the automatic tracking system using such an envelope. A signal processing part
27
produces a synchronous signal (or Vref) by using input data and applies it to a servo part (
26
), and servo part
26
rotates a drum and a capstan motor. The data applied to signal processing part
27
is converted to be suitable for tape recording, and is provided to the head through a recording amplifier
23
thereby being recorded on the track of the tape. The drum servo of servo part
26
controls a drum motor so that the drum motor's rotating phase is synchronized to the normally-recorded video signal's phase in the recording mode. A capstan servo controls the capstan motor to the number of the capstan motor's rotation, thereby maintaining the traveling speed of the tape constantly, and recording the signal on the tape by exact pitch. A control signal is recorded on the control track, and the location of the control signal is indicative of that of the recorded signal during reproduction. That is, since there is the standard of a distance between the location of the control signal and the video track, the rotating head traces the track on the basis of the control signal like when recording, and reproduces the recorded signal. One control signal is recorded with respect to two video tracks. Two video heads are attached to a rotating head drum, and two video heads are physically offset from each other (
12
) in opposite directions (azimuth scanning). A single control is made with respect to one rotating motion of the rotating drum so that a video track recorded by a channel-
1
head is traced by the channel-
1
head.
Accordingly, servo part
26
rotates the drum and the capstan motor in response to the synchronous signal (or Vref) during reproduction, and a signal produced from the head is amplified by amplifier
23
and is produced to signal processing part
27
. Signal processing part
27
receives the amplified signal and restores the same to data, thus producing it to a monitor. The drum servo of servo part
26
controls the number of rotations of the drum motor constantly during reproduction to obtain a regenerative signal without time shaft variation. The capstan servo controls the capstan motor so that the video head exactly traces the track, thus obtaining a regenerative signal of a maximum level. Envelope detecting part
24
detects an envelope signal from the RF signal produced by amplifier
23
, and tracking control part
25
digitalizes the envelope signal detected by envelope detecting part
24
to obtain tracking data, and transmits the data to servo part
26
.
FIG. 3
is a detailed block diagram of tracking control part
25
of
FIG. 2
, and an analog/digital (A/D) converter
31
converts the envelope signal Env into a digital signal according to an A/D sampling clock, as shown in
FIG. 4
b
. A summing part
32
sums the envelope signal, digitalized by A/D converter
31
, in the unit of a head switching pulse H/SW, as shown in
FIG. 4
a
. The sum area of summing part
32
indicates a single tracking section, a half period of the head switching pulse, as shown in
FIG. 4
c
. Therefore, summing part
32
adds one to several A/D values to one track.
Storing part
33
stores the summed data in an address produced from a tracking controller
35
, e.g. an address corresponding to a track offset value. Whenever tracking controller
35
changes a tracking value, e.g. an offset value, the value added by summing part
32
is stored in storing part
33
. Storing part
33
stores sum data for each track, as shown in FIG.
5
. The horizontal axis of
FIG. 5
corresponds to values obtained by offsetting the head when reproducing the track, made during recording.
FIG. 6
depicts a tracking offsetting method, and A and B and C correspond to zero and left in offsetting. Track center detecting part
34
obtains a center of the track by the use of data for each track stored in storing part
33
. The center of the track may be obtained either by finding the form of a peak curve and obtaining its maximum value, or by obtaining a middle of a value more than a fixed value. Track center detecting part
34
obtains a track center value by the use of one of the above methods, and produces the track center data to tracking controller
35
. Tracking controller
35
produces the tracking data to servo part
26
, thus performing tracking.
As described above, according to the conventional automatic tracking method, the overall values A/D converted by tracks are summed to process it as one data, and the center of the track is obtained with an average of the overall values. There is no problem of finding the center of the overall signals of the track, and this method cannot cope with deterioration of the linearity of the track or a change in the track. As shown in
FIG. 7
a
, the trace of the recording track in set A has a linearity problem in an upward direction, due to mechanical problems, worn-out tapes, etc., and the trace of the track in set B has a linearity problem in a downward direction, as shown in
FIG. 7
b
. In this occasion, according to the conventional art, the trace of the head exactly overlaps the recording track, as shown in
FIG. 7
c
. However, there are linearity problems as shown in
FIGS. 7
a
and
7
b
, and an output of the head is depicted in
FIG. 7
d
. If the dotted line of
FIG. 7
d
is a restorable minimum signal level, the data cannot be restored under that level.
Since the narrower the width of the track is, the more the problem becomes serious, recording is made by shuffling data for correcting errors during recording digital data, and when a predetermined part of the track is not restored due to the difference of signal levels, the overall screen is broken.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an automatic tracking system and an automatic tracking method that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an automatic tracking system and an automatic tracking method whereby a track is processed as one block to find a one-
Habermehl James L
Hudspeth David
LG Electronics Inc.
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