JPS60150257A - Automatic tracking device - Google Patents

Abstract

PURPOSE:To attain automatically the interchangeability of tracking control among different devices even for a VTR having no capstan servo loop, by controlling a drive motor for rotary magnetic head according to four pilot signals. CONSTITUTION:The pilot signals are sampled by an LPF19 for the signals reproduced by rotary magnetic heads A and B. Then these reproduced signals are applied with balanced modulation through a balanced modulator 21. The signals having frequency components 3fH and fH are obtained by a fact whether the scan of the head A or B is delayed or advanced. A voltage comparator 26 compares the levels of signals of fH and 3fH with each other, and the phase difference output is added with the output signal of a loop filter 33 for automatic frequency control by an adder 28, then supplied to a cylinder motor 13 as a control signal. The automatic phase control is applied to the magnetic head driving motor 13 so that the phase difference output goes to a reference level. While both heads A and B receive the tracking control so as to scan accurately their own video tracks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a tracking device for a video tape recorder (hereinafter referred to as a VTR), and more particularly to a tracking device suitable for a VTR that does not have a camouflage stancer de Luso.

[Technical Background of the Invention] In recent years, in VTRs, four (4) and pilot signals of different frequencies are superimposed on a video signal and recorded onto a magnetic tape by a rotating magnetic head (4), and during playback, the rotating magnetic head A played by? A device has been developed that controls the tiger and king phases of a rotating magnetic head by controlling the rotational phase of a capstan motor based on a pilot signal.

According to such a device, a control track for tracking control is provided for the magnetic tape independently of the video track, which is necessary for adjusting the tracking phase between different devices, which is required in the conventional pVYR. The tracking phase can be automatically set to a predetermined state even between different devices.

[Background technology issues]

However, in the case of the tracking device having the above configuration, there is a problem that it cannot be applied to VTRs in which the capstancer does not have a loop, such as simple VTRs, small W VTRs, and low-cost VTRs.

[Purpose of the invention]

This invention was made to deal with the above situation, and even in VTRs that do not wait for the capstan servo loop,
It is an object of the present invention to provide an automatic tracking device that can automatically achieve tracking control compatibility between different devices without using adjustment means such as a lumen.

[Summary of the invention]

This invention is configured to control the tracking phase of the rotating magnetic head by controlling the rotational phase of a motor that rotationally drives the rotating magnetic head based on the reproduced pilot signal. .

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

First, using FIG.
Explain the turn. In the illustrated magnetic tape J, there is no conventional control track.

Tape 1 has video tracks 2 l' 3 , 4 , 5
.

6.7. ... are formed in order. Track 2.
4.6 was recorded by one of the two rotating magnetic heads (hereinafter referred to as head A).Ql Track 3
, 5.7 were recorded by the other head (hereinafter referred to as head B). In these tracks, pilot signals for controlling the tracking phases of heads A and H are recorded superimposed on the video signal. There are four types of pilot signals, each with a different frequency.

These four-level pilot signals having different frequencies are sequentially recorded on different video tracks in a predetermined order. That is, if the frequencies of the four pilot signals are respectively ft t f2 + fs + f4, each video track 2 to 2 has a frequency f1 + ft w, for example.
Four pilot signals of fs + f4 + f1 tf2 are recorded. Note that arrow A indicates the tape running direction, and arrow opening indicates the running direction of the rotating magnetic head.

During reproduction, for example, the rotating magnetic head B scans the track 5 as shown in the figure. At this time, the head B reproduces the i4 Ilot signal and video signal of frequency 14 recorded on track 5, and also reproduces the 79 Ilot signal of frequency f3 and fl from tracks 4 and 6 on both sides, respectively.

This means that the frequency of the pilot signal is set to a low value,
This is to avoid being affected by the crosstalk removal effect due to azimuth loss.

Similarly, in head A, the pilot signals of the tracks on both sides are reproduced together with the pilot signal of its own track.

Next, the configuration and operation of the portion that controls the tracking phases of heads A and B based on the no-chip signal reproduced from the magnetic tape 1 will be explained using FIG. In the figure, I is a guide cylinder around which a magnetic tape 1 (see FIG. 1) is wound, and 12 is a rotating cylinder on which rotating magnetic heads A and B are provided. J3 is a cylinder motor that rotationally drives the heads A and B by rotationally driving the rotary cylinder 5-12.

The signals reproduced from the rotating magnetic heads A and B are sent to the reproduction preamplifier 15 via the rotating transformers 14m and J4b, respectively.
The head switching pulse P8 is input to the terminal J6, and is further input to the switch SWl, which is opened and closed by the head switching pulse P8 inputted to the terminal J6. The outputs of the amplifiers 15h and 15b are alternately taken out from the switch SW□, and these outputs are input to an AGC (automatic gain control) amplifier 17, where the amplitude thereof is adjusted. The output signal of this amplifier 17 is passed through a low-pass filter (
LPF) 79 K is supplied, and the quilot signal is extracted. This pilot signal output is supplied to the AGC detection circuit 2o. Furthermore, this pilot signal output is sent to a balanced modulator (BM) to which a plurality of converted pilot signals having the same frequency and the same order as the pilot signals supplied to heads A and B during recording are inputted to the terminal 211.
2J and balanced modulation is performed.

6- At this time, as shown in the table, - Mother pilot signal P (fs)
If the frequencies of P(f4) to P(f4) are determined (as well as the converted pilot signal, respectively), J? with a frequency equal to the pilot signal frequency), this 8M2)
From this, signals with frequency components of 3 fH and fH are obtained.

For example, when head B is scanning track 5 as shown in FIG. 7 of the frequencies fs and fl, respectively.
4. Regenerate the pilot signal P(fl)tP(ft). At this time, as a conversion pilot signal, a conversion pilot signal having the same frequency as the pilot signal P (f4) is supplied from the terminal 211 to 8M2J (this is done because the servo is applied). Therefore, 8M21
The above frequency components are synthesized, and in this case, a signal of the frequency component 1f4-fl1 corresponding to the advance of the tape and a signal of the frequency component 1f4-fsl corresponding to the delay of the tape are obtained.

Note that the frequency component corresponding to the scanning of track 5 is zero (Cf4fa=o). 3fH and fH from 8M21
The level of the signal having the frequency component is proportional to whether the scanning of head A or B is shifted to the left or right (where fH is the horizontal synchronization frequency).

That is, depending on whether the scanning of head A or B is leading or advancing, the level of one of the signals having frequency components of 3fH and fH will be higher than the other. As you can see from the table, the famous station wave number components corresponding to delays (or advances) in heads A and B are reversed.
This can be done by switching the head switching pulse P and the switch SW2 as described later.

The output of 8M2 J is a band pass filter (BPF) to extract frequency components of fH and 3 fH, respectively.
22 and 23. Signals having frequency components of fH and 3fH extracted by the BPFs 22 and 23 are level-detected by level detectors 24 and 25, respectively, and input to the switch SW.

As mentioned above, this switch SW is used for switching the heads A and B because the frequency components corresponding to the lead and lag are reversed. In other words, when playing with head A, the frequency component corresponding to the advance is fH (the delay is the same 3 fH\When playing with head B, it is 3 fH (the delay is fH) from,
This switch SW is set to a when head A is playing.
The output of the BPF 22 for fH is connected to the child terminal of the voltage comparator 26, and the BPF for fH, ? , 9 are switched to be input to one terminal of the voltage comparator 26, so that when the head B is performing reproduction, the output is just the opposite. The voltage comparator 26 compares the levels of the frequency 9-component signals of fH and 3fH, and outputs the difference.

This phase difference output is supplied to the fixed terminal P of the switch sw3 via the loop filter 27. The movable contact piece m of the switch SW3 is connected to the fixed terminal P during reproduction, and guides the output signal of the loop filter 27 to the child terminal of the adder 28.

On the other hand, during recording, it is connected to the fixed terminal R, and the reference voltage vr
Play with. □ Adder 28 adds the output signal of loop filter 27 and the output signal of loop filter 33 for AFC (automatic frequency control), which will be described later, and supplies the result to motor drive circuit 29. The motor drive circuit 29 amplifies the input signal and supplies it to the cylinder motor J3 as a motor control signal.

According to the above, the APC (automatic phase control) of the cylinder motor 3 that rotationally drives the rotary magnetic heads A and B is applied so that the phase difference output becomes the reference level, so that the heads A and B have their own Tracking is controlled to accurately scan the video track. That is, the tracking phases of heads A and H are controlled so that the two signal levels having frequency components of fH and 3 fH are the same or have a constant voltage difference.

Note that 30 and 3 are the magnet and head of a frequency generator that detects the rotational frequency of the rotating cylinder 120, respectively. The rotation frequency detected by this frequency generator is compared with a reference signal Sr having a frequency of 30 Hz by a comparator 32, and a difference in frequency between the two is detected. This detection output is passed through the loop filter 33. resistance 34
As described above, the signal is supplied to the adder 28 via the adder 28, and AFC is applied to the cylinder motor J3.

In addition, in the figure, 35 is a feedback resistor.

As described in detail above, this embodiment uses the cylinder motor 3 based on the pilot signal reproduced from the magnetic tape J.
The configuration is such that the tracking phases of the rotary magnetic heads A and H are controlled by controlling the 0 rotation phase by 1IilI.

Therefore, even if the capstancer is used in a VTR without a loop, it will automatically adjust the tracking phase to a predetermined value without providing adjustment means to ensure compatibility between different +lA units such as tiger and king polymers. Can be set to phase.

Incidentally, in recent years, in VTRs, systems have been developed in which a rotary cylinder and a cap stan are rotationally driven by a single motor. In such a system, Cap Stanchy 4? When a loop is not provided, constant-speed driving of the cap stan is generally achieved by sandwiching the cap stan shaft with a magnetizing brake. Therefore, the present invention is also applicable to a VTR in which a rotary cylinder and a capstan are rotationally driven by one motor.

In addition, this invention has its roots in the capstancer
Of course, it may be applied to TR.

〔Effect of the invention〕

As described above, according to the present invention, even in VTRs that do not have a canister sensor, compatibility of tracking control between different devices can be automatically achieved without providing adjustment means such as tracking volume. An automatic tracking device can be provided that can achieve this.

[Brief explanation of drawings]

FIG. 1 is a diagram showing magnetic tape recording and recording in an embodiment of an automatic tracking device according to the present invention, and FIG. 2 is a circuit diagram showing a circuit configuration of the embodiment. 1... Magnetic tape, A, B... Rotating magnetic head, 1
2...Rotating cylinder, 3...Cylinder motor, 1
4 a + J 4 b”・Rotating transformer, 15 a
, 15b... regenerative preamplifier, swl, sw,
, sw3...Sui, Te, 17...AGC amplifier, J8...Equalizer amplifier, 19 ・LPF, 2
J ・=・B M, 2'δ-AGc detection circuit, 22.2
3... BPF knee 24, 25... Level detector, 26... Voltage comparator, 27... Loop filter,
28... Adder, 29... Motor drive circuit. 13- Figure 1-11 Kaya

Claims (1)

[Scope of Claim] A magnetic tape in which a PYW signal for controlling the tracking phase of a rotating magnetic head is recorded together with a video signal by the rotating magnetic head. a motor that rotationally drives the rotating magnetic head; Phase control for controlling the tracking phase of the rotary magnetic head by controlling the rotational phase of the motor based on the pilot signal reproduced together with the video signal from the magnetic tape by the rotary magnetic head. An automatic tracking device comprising means.