JPH0514977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a signal reproducing device, and more particularly to a medium transfer method in a device that reproduces a recorded signal by periodically tracing a track formed at a predetermined pitch on a recording medium with a reproducing head. Regarding the suspension of

(Description of Prior Art) As an example of this type of device, there is a video tape recorder (VTR) that records and plays back video signals.
In this specification, tape stop control during still image playback in a VTR will be described below.

When playing still images (still playback) on a VTR, the tape is stopped, so there is a difference in slope between the video track on the tape and the trace locus of the rotating head. As a result, points at which the playback signal level drops appear at regular intervals, and these points become noise bars on the playback screen.

FIG. 1 is a diagram showing the relationship between the trace locus of a rotating head and a recording track in a VTR. In FIG. 1, 1A, 2A, 3A are recording tracks by the first rotary head, 1B, 2B, 3B are recording tracks by the second rotary head, and 4 is a magnetic tape. Tracks 1B, 2B, and 3B have different magnetization directions.

In Fig. 1, LS is the ideal trace trajectory when playing still images by tracing the magnetic tape 4 alternately with the first and second rotating heads, and IS
shows an ideal trace locus when a still image is reproduced by tracing the magnetic tape 4 alternately with the first rotary head and a head having the same magnetization direction as the first rotary head.

FIG. 2 is a diagram showing an envelope waveform of a reproduced video signal during still image reproduction. FIG. 2a shows a 30 Hz rectangular wave signal (30PG) synchronized with the rotation of the rotary head, and the rise and fall of 30PG in the figure indicate the timing at which tracing of a track by the rotary head starts or ends.
That is, for example, the first rotary head traces a track during 1/60 seconds when 30PGa is at a high level (H).

When a still image (frame still) is being played back based on the trace trajectory of the LS, the first rotary head is alternately reproducing track 1A and the second rotary head is reproducing track 2A, and the reproduction signal is The envelope waveform is as shown in FIG. 2b.
Now, if the head trace locus during frame still deviates from the ideal trace locus shown in LS, the playback envelope waveform will be as shown in Figure 2b', for example, and the signal degraded portion indicated by X in the figure will be on the playback screen. It appears as horizontal line noise at the top.

On the other hand, when still image playback (field still) is performed using the trace trajectory of the IS, track 3A is repeatedly played back by the first rotating head and a head with the same magnetization direction, and the envelope of the playback signal is The waveform becomes as shown in FIG. 2c.
On the other hand, if the trace trajectories of these heads deviate significantly from the ideal track trajectories shown in IS, an envelope waveform as shown in Figure 2 c' will result, for example.
A signal deterioration portion indicated by X in the figure occurs and appears as band-shaped noise on the playback screen.

In order to match the trace locus of the head with the ideal trace locus as described above, it is necessary to accurately determine the tape stop position. In conventional VTRs, the tape stop position was determined by reproducing a control signal (CTL) recorded in the longitudinal direction at the end of the tape and using the reproduced CTL.

However, since the CTL is recorded at the end of the tape, it is not possible to stop the tape at the ideal stop position when the video rack is bent. Furthermore, the CTL is information that is obtained intermittently only when the CTL reproducing head is reproducing the CTL, and it is not possible to accurately determine the stop position of the tape.

Furthermore, recording such CTL at the end of the tape hinders high-density recording, and in recent years VTRs that do not record CTL have been proposed and implemented.

(Object of the Invention) In view of the above-mentioned drawbacks, the present invention aims to accurately stop a recording medium at an ideal stop position and obtain a good reproduction signal without providing a special control signal track on the recording medium. The purpose of the present invention is to provide a signal reproducing device that can perform the following functions.

(Description by Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 3 is a diagram showing a schematic configuration of a VTR as an embodiment of the present invention. In FIG. 3, reference numeral 4 denotes a magnetic tape, which is wound around the rotating drum 6 in an angular range of 180° or more. The drum 6 has heads 5a and 5 having different magnetization directions with a phase difference of approximately 180°.
b is installed. Further, a head 5c having the same magnetization direction as the head 5a is attached adjacent to the head 5b. The signals picked up from these heads are sent to the head switching circuit (HSW).
It is made into a continuous signal at 9.

The continuous signal obtained by the HSW 9 is supplied to the video signal processing circuit 14, where it is restored to its original signal form and output. At this time, in the VTR of this embodiment, during normal playback, the playback signals obtained from heads 5a and 5b are used, and during still playback, the playback signals obtained from head 5a are used.
a, the reproduced signal obtained from the head 5c is used.

The ATF signal generating circuit 15 uses the reproduction signals of the heads 5a and 5b to generate a tracking error signal that continuously indicates a tracking error between the head 5a or 5b and the video track. The method is to use a well-known four-frequency (pilot signal) method. The 4-frequency method simply means that during recording, four types of pilot signals having different frequencies are sequentially recorded for each track, and then the pilot signal obtained from both adjacent tracks of the track being mainly traced by the playback head is used. The signal level comparison output is used as a tracking error signal, or even as an ATF signal.

The ATF signal obtained by the ATF signal generation circuit 15 is supplied to the capstan motor control circuit 8 and controls the capstan 6 via the capstan motor drive circuit 7. Generally, the capstan motor control circuit 8 has a phase control loop based on this ATF signal,
There is a speed control loop that detects the rotation of the capstan 6 and keeps the rotation speed constant, but a detailed explanation will be omitted here.

On the other hand, a 30Hz drum showing the rotational phase of drum 6
PG is obtained via a detector 12 and a generator 13;
This drum is the switching timing of HSW9.
Controlled by PG. Further, a high frequency pulse signal (drum FG) for detecting the rotational speed of the drum 6 is obtained by a detector 10 and a generator 11.

17 is a still playback control circuit, and when a playback command is issued by the system controller 18,
Using the aforementioned drum PG, ATF signals, etc., the capstan 6 is controlled via the capstan motor control circuit 8 from when a still reproduction command is issued until when still reproduction is actually performed.

The operation of the still playback control circuit 17 will be explained in detail below. FIG. 4 is a diagram showing a specific example of the still playback control circuit 17 in FIG. 3. Fourth
In the figure, 21 is a terminal to which the ATF signal is supplied;
22 is a terminal to which the drum PG is supplied, 30 is a terminal to which the drum FG mentioned above is supplied, and 31 is a terminal to which a control signal instructing still playback is supplied from the system controller 16. Further, 26 is a comparator, 32, 33, 34, and 35 are D type flip-flops (DFF), 36 is an AND gate, and 37 is an output terminal for a capstan driving signal.

FIGS. 5A to 5C are timing charts showing the waveforms of each part of FIGS.

First, a control signal is supplied to the capstan motor control circuit 8 at the same time as a still playback command from the system controller 16, and the capstan motor control circuit 8 performs control during normal playback, that is, speed control.
The phase control using the ATF signal is switched to the control using the capstan drive signal obtained from the still playback control circuit 17.

Next, the operation of generating a capstan driving signal by the still reproduction control circuit 17 will be explained. Fourth
The ATF signal input from terminal 21 in the figure is supplied to comparator 26 and compared with a voltage indicating on-track. This voltage is obtained by dividing the power supply voltage Vcc by resistors R1 and R2. The output of this comparator 26 is the transistor T1,
The signal is supplied to a differentiating circuit consisting of a capacitor C1 and a resistor R5 via an inverting circuit consisting of resistors R3 and R4. The output signal of this inverting circuit is shown in FIG. 5, and the output signal of the differentiating circuit is shown in FIG. 5, respectively. The output signal T of the differentiating circuit is supplied to the CK terminal of the DFF 35.

On the other hand, 30PG input from terminal 22 is DFF3
2. A pulse signal D is supplied to a monomulti including a capacitor C2 and resistors R6 and R7, and has a pulse width to stop the tape at a desired stop position. The pulse width of this pulse signal 2 can be adjusted by variable resistor R6. Then this DFF
DFF33 is triggered by the Q output of 32, and this
The DFF 33 operates as a monomultiply with a capacitor C3 and a resistor R8, and obtains a periodic signal as shown in FIG. 5E as its Q output.

The DFF 35 is triggered by the rising edge of the output of the differentiating circuit described above, and is reset by the Q output of the DFF 33. The output signal of this DFF 35 is supplied to an AND gate 36, which opens the AND gate when a still reproduction command is issued. The other day drum FG
A pulse signal (drive signal) whose frequency is divided by 1/2 by the DFF 34 is supplied to the capstan motor control circuit 8 from a terminal 37 as a capstan drive signal N via an AND gate 36.

Assume now that head 5a and head 5c are performing field still, and the ATF signal is sent to head 5.
It is assumed that the signal is obtained from the reproduced signals of the head 5a and the head 5b. At this time, if the on-track timing (the timing at which an upward pulse is generated on the differential output) during head 5a reproduction matches the midpoint of the high level portion of the 30PG for head switching (shown as τ in Figure 5). As is clear from FIG. 2, the trace loci of heads 5a and 5b are ideal trace loci IS.

In the above-described embodiment, the on-track timing deviates from the ideal timing by the period t2 shown in FIG. However, the period during which the driving pulse signal RO is gated is set to be the period t1, which is longer than the period t3. This means that even if the capstan 6 is actually driven during the period t3 with the drive pulse low, the capstan 6 is not driven. That is, the minimum period t3 required to drive the capstan is added to the period t2 corresponding to the phase difference to obtain the gate period t1. As a result, the on-track timing coincides with τ, and the heads 5a and 5c trace on the ideal trace trajectory IS.

According to the VTR configured as described above, it is possible to accurately stop the recording medium at a desired stop position without using a CTL, and to obtain a good reproduced still image signal. Further, by adjusting the variable resistor R6, variations in the physical characteristics of the device (especially the capstan) can be corrected in advance. Also, unlike when using CTL, the tape can be stopped at an ideal stop position even if the recording track is curved.

In the above embodiment, when field still is performed using the heads 5a and 5c, the head 5
Although the ATF signal obtained from the reproduced signals of the heads 5a and 5b is used, the same operational function can be realized by using the ATF signal obtained from the reproduced signals of the heads 5a and 5c which are performing reproduction. It goes without saying that this method can also be applied to VTRs that perform frame stills. For example, the pulse width of the monomulti output signal 2 including the DFF 32 may be increased by 1/120 seconds.

(Description of Effects) As explained above, according to the present invention, a signal reproducing device is provided which can accurately stop a recording medium at an ideal stopping position without providing a special control signal track on the recording medium. I was able to get it.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the recording track and the trace locus of the head in a VTR, FIG. 2 is a diagram showing the envelope waveform of a reproduction signal during still image reproduction, and FIG.
FIG. 4 is a diagram showing a schematic configuration of a VTR, FIG. 4 is a diagram showing a specific example of a still playback control circuit, and FIG. 5 is a timing chart showing waveforms of various parts in FIG. 1A to 3A and 1B to 3B are tracks, 4 is a magnetic tape as a recording medium, 6 is a capstan as a transport means, 12 is a drum rotation phase detector, 13 is a drum PG generator, and 15 is an ATF as an error signal. A signal generation circuit, 17 is a still reproduction control circuit, 26 is a comparator included in the first periodic signal generation means, 32 and 33 are DFFs included in the second periodic signal generation means, and 35 is a gate pulse generation circuit. The DFF included in the means and 36 are AND gates included in the gate means.

Claims (1)

[Scope of Claims] 1. A device for reproducing a recorded signal by periodically tracing a track formed at a predetermined pitch on a recording medium using a reproducing head, the apparatus comprising: transporting the recording medium in a direction intersecting the track; means for generating an error signal continuously indicative of a tracking error between the playback head and the track; means for generating a first periodic signal associated with the error signal; and means for generating a first periodic signal associated with the error signal; The second trace period related to
means for generating a periodic signal; means for generating a gate pulse having a pulse width corresponding to a phase difference between the first periodic signal and the second periodic signal; means for generating drive pulses for transporting the medium in minute amounts at a cycle shorter than the cycles of the first and second periodic signals; and gate means for gating the drive pulses with the gate pulses. A signal reproducing device comprising: