JPS59218654A - Rotary head type magnetic video recording and reproducing device - Google Patents

Abstract

PURPOSE:To ensure satisfactory tracking operation even with use of an interchangeable tape by using the control signal of an automatic saturation control (ACC) circuit for color signal of a video signal processing circuit to control the gain of a pilot reproduction signal. CONSTITUTION:An input terminal 32 to which the control voltage of an ACC circuit, i.e., the output of an ACC wave detecting circuit is supplied is connected to an automatic gain control (AGC) circuit 19. The gain of the output of an LPF9 is controlled by the circuit 19 with the control circuit of the ACC circuit. A signal component having a frequency component most approximate to the pilot signal frequency is used as the frequency of a record signal on a magnetic tape. Therefore, the effect of variance of the frequency characteristic of an electromagnetic conversion system such as a core loss, etc. can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating head type magnetic recording image reproducing apparatus (hereinafter referred to as a rotating head type VTR) for recording and reproducing color video signals.
'j'o), and particularly relates to a rotary head type VTR configured to record and reproduce a pilot signal superimposed on a video signal and to detect a tracking error using the reproduced pilot signal.

First, the pilot signal system will be explained below.

FIG. 1 is a block diagram showing one embodiment of a pilot signal system. In the figure, a head switching pulse is input to an input terminal (1). Using this head switching pulse, the cyclic frequency generator (2) generates signals of four frequencies for each field by cycling them at a period of four fields. These four frequencies are, for example, N T
S C (1ational Television)
FOAC-378FH (FH;
f, −fose (frequency of horizontal periodic signal)
158fl-fose/5Op et al-fose/
36, f, -fose /4. The output of this frequency generator (2) is input to the input terminal (3) and is superimposed on the modulated video signal, and this superimposed signal is sent to the recording amplifier (4), switch (5) and rotary transformer (6). is applied to the magnetic head (7) to record on the magnetic tape.

FIG. 2 shows the pattern recorded on the magnetic tape TP as described above. The video signal tracks are lined up in the longitudinal direction of the tape TPO in fill order, and a pilot signal is recorded in a superimposed manner on the video signal tracks. Fi, F2. F3 and F,
are the 'IP's mentioned above respectively? This indicates that pilot signals of frequencies f8 and f4 are recorded.

During signal reproduction, the magnetic head MH
is tracking the track Fl, in addition to the frequency of f, the signal reproduced by the magnetic head MH includes the pilot signal of the adjacent track (in the case of Fig. 2) due to the side read effect, etc. contains pilot signals of f4 and fρ frequencies) at the same time. The magnitude of the pilot signal components of both adjacent tracks included in the signal reproduced by the magnetic head MH is
varies depending on the amount of positional deviation from the track center. For example, if the magnetic head MH is in the F2 direction (to the right)
If the position is shifted to f.

The magnitude of the pilot signal component at the frequency increases. Therefore, by detecting the magnitude of the pilot signal components of both adjacent tracks, it is possible to detect the amount of positional deviation of the magnetic head MH from the track center.

In Fig. 1, when reproducing a signal, a signal is reproduced from the magnetic tape by a magnetic head (7), passes through a rotary transformer (6), a switch (5), and is amplified by a reproducing amplifier (8). Ru. The output of the regenerative amplifier (8) is passed through a low-pass filter (hereinafter abbreviated as LPF) (9) to remove the video signal component and extract the pilot signal component. The frequency is set f for each field according to the pilot signal component extracted by L P F (91) and the head switching pulse.

A cyclic frequency generator (2
) is input to the mixer (10). The output of this mixer 00) is passed through the first band pass filter (hereinafter referred to as BP
)01) and the second B P F (12
), a difference frequency signal component between the signal W of the output of the cyclic frequency generator (2) and the frequency of the pilot signal component of the output of L P F (9) is obtained.

By the way, in the case of an NTSC video signal, fOse
”::5.95MHz, so fl t ft
l et al. and f4 are f,=l O2KHz,
f,=l 19KHz.

et: 165 KHz, f, : 14 (l KHz. This makes ft-ft=ra-f4':?16.5 KHz
, f, -f, zchi-f, the frequency becomes 46.5 KHz. However, the passband of the first BPFQU is 16.5.
In the vicinity of KHz, the passband of the second BPF (12) is set to 4
Suppose that it is selected near 6.5 KHz (7). When the magnetic head MH is tracking the track of FI as shown in FIG. A signal having an amplitude proportional to the magnitude of the pilot signal (frequency ta>component) of the F4 track is obtained from the second BPF'□.
The outputs of P F (11) and the 20th BPF (2) are envelope-detected by the first detector αJ and the second detector αa, and the outputs of the first and second detectors (1
By passing the respective outputs of 3) and Q4) through the subtracter (1!9), a voltage level corresponding to the amount of positional deviation of the magnetic head MH from the track center in FIG. 2 is obtained as the output of the subtracter. .

As is clear from the recording pattern in FIG. 2 and the frequency of flt'tt et al.
When H is tracking Fi or F3 and when it is tracking F26 or F4,
The polarity of the output of the subtracter (2) with respect to the positional deviation of the magnetic head MH from the track center is reversed. Therefore, if the output of the subtracter 05) and the signal obtained by inverting the output of the subtracter (5) by the inverting amplifier 0e are selected using the switch σ in synchronization with the head switching pulse, the track center of the magnetic head MH is An output voltage proportional to the amount of positional deviation from the output terminal α is obtained. Good tracking can be obtained by feeding back the signal obtained from this output terminal (18) to the capstan motor.

As mentioned above, this pilot signal method detects the amount of crosstalk between the pilot signal components of both adjacent tracks tracked by the playback head, so it is possible to Characteristic,
Furthermore, the amount of crosstalk varies depending on the recorded current value of the pilot signal, etc. Therefore, when playing a compatible tape, it is difficult to obtain good tracking in terms of the dynamic range of the tracking error detection circuit or the DC loop gain of the control loop as shown in FIG.

In order to improve this drawback, it is conceivable to configure an automatic gain control circuit (hereinafter referred to as an AGC circuit) using the pilot reproduction signal itself.

FIG. 3 shows an example of an AGC circuit for pilot reproduction signals. The output of L P F (9) is connected to the AGC circuit (
1■, and the output of this AGC circuit (1g) is
The detection circuit (2) converts it into a DC voltage, and the output of this AGC detection circuit (4) controls the gain of the AGC circuit (19).

However, as described in the explanation of the operation of the pilot signal system in Figure 1, the pilot reproduction signal output from the LPF (9) contains crosstalk components of both adjacent tracks that change depending on the deviation of head tracking. To include, AGC
The specific power of the wave detection circuit does not necessarily directly reflect variations in the characteristics of the electromagnetic conversion system.

This invention was made in order to improve the above-mentioned drawbacks, and it uses a control signal for a color signal automatic saturation control circuit (hereinafter referred to as an ACC circuit) among the video signal processing circuits mounted on a normal VTR. By controlling the gain of the pilot playback signal using the rotary head, variations in the electromagnetic conversion system characteristics are accurately reflected, and good tracking can be obtained even when using compatible tapes. The purpose of this invention is to provide a type magnetic recording/playback device.

FIG. 4 shows an example of a color signal processing circuit, and the operation of the ACC circuit will be briefly explained according to this diagram. The reproduced color signal applied to the input terminal (21) is A
The signal is supplied to the CC circuit (22), where the gain is controlled so that it follows the burst level and becomes a constant color signal, and then supplied to the main converter. Frequency conversion is performed in this main converter track, and BPF (24
), a signal component of 3.58 MHz±500 KHz is extracted. The output of this BPF is the compressor (
b), and the burst signal is attenuated to a predetermined burst level.

The output of this compressor (5) is connected to the IH delay line■
The crosstalk component of the color signal is removed here, the ratio is improved to 82, and the signal is sent to an amplifier (5).

01) is a color signal output terminal.

The control input for the ACC circuit is obtained as follows. The output of the above-mentioned amplifier gradient is extracted by the gate circuit (28) only during the application period of the burst gate pulse applied to the input terminal (2), and outputted to the ACCCC detection circuit. ACCC
The burst level supplied only during the burst signal period for the C detection circuit is converted into a DC voltage and sent as a control voltage to the ACC circuit. In the normal human CC detection circuit ■,
The leading value of the burst level of the reproduced color signal is detected.

Now, FIG. 5 shows a block diagram of an embodiment of the present invention. In the same figure, (32) is the ACC shown in FIG.
This is an input terminal into which the control voltage of the circuit (branch), that is, the power for the ACCCC detection circuit is input. 9, AGC circuit (19)
It is connected to the. The output of LPF (91) is connected to the ACC circuit (
By controlling the gain in step 19), the control operation can be performed regardless of the characteristics of the electromagnetic conversion system.

As shown in the embodiment of FIG. 5, the control voltage of the ACC circuit (incorporated) of the color signal processing circuit is
When used to control a CC circuit, there are the following advantages.

(1) To use existing circuit signals as control signals,
The circuit configuration becomes simpler.

(2) As the recording signal frequency on the magnetic tape uses the signal component with the frequency component closest to the pie recording signal frequency, it is not affected by variations in the frequency characteristics of the electromagnetic conversion system characteristics such as core loss. Hateful.

(3) Since it is in a frequency range higher than the pilot signal frequency, the magnitude of the signal component of the main track being tracked by the magnetic herad can be more accurately reflected due to the effect of azimuth loss.

+4) IH delay line (Since it has a built-in delay line, a signal with suppressed crosstalk components from adjacent tracks can be obtained.

In addition, in Fig. 5, the output of LPF (91) is
The circuit (1) was designed to be supplied, but the AGC circuit (1ω
It goes without saying that the same effect can be obtained even if the filter is placed before the LPF or after the mixer (101).

As described above, according to the present invention, since the control signal of the ACC circuit in the video signal processing circuit is used to control the gain of the pilot reproduction signal, variations in the characteristics of the electromagnetic conversion system are accurately reflected. Therefore, it is possible to provide a rotary head type VTR that can obtain good tracking even on compatible magnetic tapes between devices.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a conventional rotary head type magnetic recording/reproducing device using the pilot signal method, and Fig. 2 is a diagram showing the recording pattern on the magnetic tape and the state of the magnetic head used in the device shown in Fig. 1. , FIG. 3 is a block diagram showing an example of an automatic gain control circuit configured using the pilot signal itself, FIG. 4 is a block diagram showing the configuration of an automatic saturation control circuit in a normal color signal processing circuit, and FIG. 5 1 is a block diagram showing an embodiment of the present invention. FIG. +11, (31...input terminal, (4)...recording amplifier, (5), (/'7)...switch, (6)
...Rotary switch, (7)...Magnetic head, (
8)...Regenerative amplifier, (9)...Low pass filter, (11)+12...Band pass filter, (13)
, (14)...Detector, (15)...Subtractor,
(16)...Inverting amplifier, (181...Output terminal,
(1■...Automatic gain control circuit, (branch)...Automatic saturation control circuit, (Foundation)...Automatic saturation control circuit control signal input terminal. In addition, the same symbols in the figures are the same or equivalent parts. Proceedings of the Attorney Masuo Oiwa (voluntary) □6□05♀ Theory 25 Column 6 of "Detailed Description of the Invention" of the subject specification, contents of amendment (1) The specification is corrected as indicated.

Claims (1)

[Claims] (1) In a rotating head type magnetic recording and reproducing device that records and reproduces a pilot signal by superimposing it on a color video signal, detects a tracking error using the reproduced pilot signal, and controls the tracking of the magnetic head. , an automatic gain control circuit is provided in a circuit configured to detect a tracking error signal from a reproduced pilot signal, and the control voltage of the automatic saturation control circuit of the color signal processing circuit is configured to be the control voltage of the automatic gain control circuit. A rotating head type magnetic recording and reproducing device characterized by: