JPS6168753A - Signal reproducing device - Google Patents

Abstract

PURPOSE:To stop a recording medium at an ideal position by detecting the phase coincidence between a periodic signal regarding a tracking error signal of a reproduction head and a recording track and a periodic signal regarding the tracing period of the head, then stopping the traveling of the medium. CONSTITUTION:A magnetic tape 4 is wound around a rotary drum 6 and playback signals are obtained by heads 5a and 5b in normal reproduction or by heads 5a and 5c in still picture reproduction. An AFT signal generating circuit 15 generates a signal showing a tracking error continuously by using the playback signals of the heads 5a and 5b, and a drum PG13 showing the rotary phase of the drum 6 is obtained through a detector 12 and a generator 13. A capstan motor control circuit 8 ad a still reproduction control circuit 17 start operating simultaneously with a still reproduction instruction from a system controller 16. The circuit 17 detects the phase coincidence between periodic signals regarding outputs of the generators 13 and 15 and outputs the detection signal to the circuit 8 to stop the traveling of the tape 4. Thus, the tape 4 is stopped at the ideal position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a signal reproducing device, and more particularly, to medium transport in a device that reproduces recorded signals by periodically tracing tracks formed at a predetermined pitch on a recording medium H with a reproducing head. Stop at W.

(Description of Prior Art) As an example of this type of device, there is a video tape recorder (VTR) for recording and reproducing video signals.Hereinafter, in this specification, tape stop control when reproducing still 1F images in a VTR will be explained.

When playing still images (still playback) on a VTR,
In order to stop the tape, there is a difference in ml between the video track on the tape and the trace locus of the rotary 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 IA relationship between the trace locus of a rotary head and a recording track in a VTR.

In FIG. 1, IA, 2A, and 3A are recording tracks by the first rotary head, IB, 2B, and 3B are recording tracks by the second rotary head, and 4 is a magnetic tape. Track IB, 2B, 3
B have different magnetization directions.

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

FIG. 2 is a diagram showing an envelope waveform of a reproduced video signal when a still city image is reproduced. Figure 2 (a) shows a 30 Hz square wave signal (30PG) synchronized with the rotation of the rotary head.
), and the rising and falling edges of 30PG in the figure indicate the timing at which tracing of the track by the rotary head starts or ends. That is, for example, if the rotating head is 30PC(a), it is 1/6 of the high level (H).
The track will be traced in 0 seconds.

When still image playback (frame still) is performed using the trace trajectory of the LS, the first rotary head tracks the track IA, and the second rotary head tracks the trunk 2A.
11f is generated, and the envelope waveform of the ifF'1 signal is as shown in FIG. 2(b). Now, if the trace trajectory of the head during frame still deviates from the ideal trace trajectory shown in LS, for example, as shown in Fig. 2 (b').
The reproduced envelope waveform becomes as shown in the figure, and the signal degraded portion indicated by an x in the figure appears as horizontal linear noise on the reproduced screen.

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 if rotating head and the head with the same magnetization direction, and the envelope of the playback signal is The waveform is as shown in FIG. 2(C). On the other hand, if the trace trajectories of these heads deviate significantly from the ideal track trajectories shown in the IS, an envelope waveform as shown in FIG. It appears as band-like noise on the top.

In order to make the trace locus of the head match the ideal trace locus as described above, it is necessary to accurately determine the top position at which the tape stops. To determine the tape stop position in a conventional VTR, a control signal (CTL) recorded in the longitudinal direction at the end of the tape is reproduced, and this reproduced CT
I was using L.

However, since CTL is recorded at the end of the tape,
When the video track is curved, it is not possible to stop the tape at the ideal stop position, and CTL
This information is obtained intermittently only when the TL re-main playback head TL is playing back, and cannot accurately determine the tape stop position.

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 does not require a special control signal track on a recording medium.

Extract the recording medium accurately to the ideal stopping position.

It is an object of the present invention to provide a signal reproducing device that can obtain a good reproduced signal.

(Explanation based on examples) An embodiment of the present invention will be described below 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 Figure 3, 4 is a magnetic tape and 5
It is wound around the rotating drum 6 in an angular range of 180° or more. Heads 5a and 5b having different magnetization directions with a phase difference of approximately 180" are attached to the drum 6. Signals picked up from these heads are converted into an a-continuation signal by a head switching circuit (H5W) 9. be done.

The 'a continuation signal obtained in H3W9 is supplied to the video signal processing circuit 14, restored to the original signal form, and output. At this time, in the VTR of this embodiment.

During normal playback, the playback signals obtained from the heads 5a and 5b are used, and during still playback, the playback signals obtained from the heads 5a and 5b are used.
It is assumed that a reproduced signal f1# from C is used.

The ATF signal generation circuit 15 reproduces the heads 5a and 5b (8
Tracking between the head 5a or head 5b and the video track using i! I! A tracking error signal shown in ha is generated. The method is to obtain the signal using a well-known four-frequency (pilot signal) method. The 4-frequency method simply means that during recording, four types of pilot signals with different frequencies are sequentially recorded for each track, and the playback head mainly uses the pilot signals obtained from both adjacent tracks of the track being traced. The signal level comparison output is used as the tracking error signal, and also as the A
The purpose is to send a TF 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 and a speed ill 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 30 Hz tram PG indicating the rotational phase of the drum 6 is obtained via the detector 12 and the generator 313, and the switching timing of H5W9 is controlled by this tram PG.

17 is a still playback control circuit, and when a playback command is issued by the system controller 18;

Using the aforementioned tram 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. Figure 4 shows the still playback control circuit 17 in Figure 3.
It is a figure which shows one specific example.

In FIG. 4, 21 is a terminal to which the ATF signal is supplied;
2 is a terminal to which the drum PG is supplied, 23 is a control output terminal, Vcc is a power supply voltage, R, 1-R9 are resistors, C1,
C2 is a capacitor, D is a diode, Tl and T2 are transistors, 24.25 is a monomulti, 26
is a comparator.

Figure 5 (1) to (vi) are Figure 4 (1) to (, vi
) is a timing chart showing the waveforms of each part, and the operation of each part during still playback will be explained below using these.

First, when a still playback command is issued from the system controller 516, the control by the capstan motor control circuit 8 is changed from the normal playback control mode described above to the control mode as described below. That is, a control signal is supplied to the capstan motor control circuit 8 at the same time as the still reproduction command from the system controller 16, and the capstan motor control circuit 8 drives the capstan 6 at a much lower speed than during normal reproduction. Further, the operation of the still control circuit 17 is started.

:tS4 The ATF signal (1) input from the terminal 21 in the diagram is supplied to the controller 26, and the comparator 2
It is compared with the voltage indicating on-track at 6. This voltage connects the power supply voltage Vcc to the resistor R+.

It is obtained by dividing the pressure at R2. The output signal (V) of this comparator 26 is supplied to a differentiating circuit composed of a capacitor C3, a resistor R8, and a diode D, and is shown in FIG.
g differential output is obtained as shown in vi).

On the other hand, the drum PG (head switching (+i number) (i) supplied to the terminal 22 is supplied to the monomulti 34.

The monomulti 34 is triggered by the rising edge of the drum PG and generates a pulse signal (i) having a pulse width determined by the capacitor C2 and the resistors R3 and R4, and the transistor TI
, through an inverter consisting of a resistor R6 as shown in FIG. 5(iv).
Obtain a pulse signal as shown in . Furthermore, this pulse signal (i
A pulse signal (vi) triggered by V) and having a pulse width determined by the capacitor C2 and the resistor R7 is obtained from the monomulti 25.

The aforementioned differential output (■) is supplied to the base of transistor T2, while the pulse signal (vi) is supplied to the emitter of transistor T2. Therefore, from the collector of transistor T2, when these phases match, the signal shown in Fig. 5 (vi)
Apply the pulse output shown in t.

This pulse output (vi) is supplied to the capstan motor control circuit 8 via the terminal 23, whereby the rotation of the capstan 6 is stopped and the tape 4 is stopped. Assuming that field still is being performed using the heads 5a and 5c, the trace locus of the heads 5a and 5c is the pulse signal (i) output from the monomulti 24 by adjusting the resistance value of R4, which is shown as LS in Fig. 1. In this case, it is sufficient to determine the pulse width of approximately 1/120 seconds.
If vi) is made close to an impulse, the tape will never stop! Since the pulse width of the pulse signal (vi) may occur, the pulse width of the pulse signal (vi) is appropriately determined within the allowable error range.

According to the VTR configured as described above, it is possible to accurately stop the recording medium at a desired stop position +1- without using a CTL, and to obtain a good reproduced still image signal. Also, since the tape speed just before stopping is low, the influence of inertia is small. Also, what if I adjust variable resistor R4? Ti
It is also possible to correct in advance variations in the physical characteristics of capstans (especially capstans). Furthermore, unlike the case where CTL is used, the tape can be stopped at an ideal stop position even if the recording track is curved.

In the above-described embodiment, when performing field still with the heads 5a and 5c, the ATF signal obtained from the reproduced signals of the heads 5a and 5b was used, but the ATF signal obtained from the reproduced signals of the heads 5a and 5c performing reproduction was used. Similar operational functions can be achieved using the ATF signal. It goes without saying that the present invention can be similarly applied to a VTR that performs frame still processing. For example, the pulse width of the output pulse signal (i) of the monomulti 24 may be set to 1/60 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 stop position without providing a special control signal track on the recording medium. I was able to get it.

[Brief explanation of drawings]

FIG. 0!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 picture reproduction, FIG. 3 is a diagram showing a schematic configuration of a VTR as an embodiment of the present invention, and FIG. 4 is a diagram showing a specific still reproduction control circuit. Diagram showing an example. FIG. 5 is a timing chart showing the waveform of the 4N6 section. IA to 3A and IB to 3B are tracks, 4 is a magnetic tape as a recording medium, 5a, 5b, and 5c are playback heads, 12 is a drum rotation phase detector, and 13 is a drum PC.
15 is a generation circuit for an ATF signal as an error signal, 17 is a still playback control circuit, and 24.25 is f!
26 is a comparator for generating the first periodic signal; TI is a monomulti for generating the periodic signal of S2;
, T2 are transistors.

Claims (1)

[Claims] A device for reproducing a recorded signal by periodically tracing tracks formed at a predetermined pitch on a recording medium with a reproducing head, the apparatus generating an error signal continuously indicating a tracking error between the reproducing head and the track. and the means to
means for generating a first periodic signal related to the error signal; means for generating a second periodic signal related to the trace period of the playback head; and means for generating the first periodic signal and the second periodic signal. and means for detecting that the phases of the periodic signals match and stopping the transport of the medium.