JPS63171464A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the influence of a false signal and also to stabilize a regenerated output from a CTL track by constituting the titled device in such a manner to amplify an output signal by a higher threshold voltage than the false signal level included in an output signal from a variable gain control amplifier. CONSTITUTION:A regenerative signal of a CTL head 6 is impressed to the variable gain CTL amplifier 17, and its output A is led to a positive polarity amplifier 10 and negative polarity amplifier 14 respectively, while a peak-to-peak value detecting circuit 15 detects a peak value of the CTL signal or cue signal and input it to a time constant circuit 16, from which a smoothed output is fed back to the amplifier 17 to control its gain. The max. value of an output of the amplifier 17 is settable near a saturated level by properly selecting a loop gain in a feedback control system. The output signal of the amplifier 17 is amplified with a higher threshold voltage than the false signal included in said signal by the amplifiers 10 and 14. Consequently, the influence of the false signal is reduced and hence the regenerative output from a CTL track can be stabilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides, for example, a control track (hereinafter referred to as "CTL track") of a videotape, along with a control signal (hereinafter referred to as "rCTL signal") as well as an address signal. The present invention relates to a magnetic recording and reproducing device that records information signals on a magnetic tape.

[Conventional technology]! Figure 83 is shown, for example, in Japanese Patent Publication No. 48811/1983. CTL) In Figure 0, which is a block circuit diagram of a control signal recording/reproducing system of a conventional magnetic recording/reproducing device designed to rewrite cue signals recorded on a rack, (6) is a control head (hereinafter referred to as "rCTL head"). .

(8) is the first switcher, (9) is the control amplifier (hereinafter referred to as "rCTL amplifier"), (10) is the positive polarity amplifier, (11) is the second switcher, (12)
(13) is a cue signal recording circuit, (14) is a negative polarity amplifier. Fig. 4 is a signal waveform diagram of each part of this conventional example, and Fig. 5 is a diagram showing a recording pattern on a video tape, where (1) is the video tape, (2) is the video signal recording part, and (3) is a diagram showing the recording pattern on the video tape. is a CTL track, (4)
(7) is a recording track of a video signal, and (7) is a control signal (hereinafter referred to as "rCTL signal").

Next, the operation will be explained. In FIG. 3, the switcher (8), which is the first switching means, connects the CTL head (6) and the CTL head (6).
When the amplifier (9) is connected, the CTL recorded on the side edge of the video tape (1) as shown in FIG.
The signal reproduced from track (3) is transferred to the CTL amplifier (
9) to obtain a reproduced signal A as shown in FIG.
Then, as shown in FIG. 4(B), only the CTL signal Bc, which is the first signal, is amplified and output. Negative polarity amplifier (14
), only the negative polarity signal is amplified (not shown), and this is used as the cue signal Q, which is the second signal.

The CTL signal signal line of the output of the positive polarity amplifier (lO) is used for controlling the rotary head or capstan, and is applied to the gate pulse generating means (12).
As shown in Figure (C), a gate pulse g is generated which is generated after a certain period of time after the CTL signal Bc and which ends before the next CTL signal line. This gate pulse g is applied to a switcher (11) serving as a second switching means, and when the switcher (11) is turned ON by a cue signal write command signal which is a command to create a new second signal, the gate pulse g operates the switcher (8) and applies the output of the cue signal recording circuit (13), that is, the third signal for creating a new second signal, to the CTL head (8) only during the period of the gate pulse g. let

The cue signal recording circuit (13) generates a recording signal rl as shown in FIG. 4(D), for example, in response to the cue signal write command signal and the desired cue signal Q to be written at that time. In this example, recording is performed in two sections of the CTL signal Be.
The time interval of the TL signal rate signal ql is longer than the previous TI
This shows how the data is written after being changed from T2 to T2. At this time, first, by generating a gate pulse g, the CTL head (8) is moved so that the magnetization becomes saturated magnetization (in this case, north pole) of the same polarity as the magnetization already saturated recorded on the video tape (1).
A signal is applied to the CTL head (6) with a delay of the CTL signal signal rate time T2 due to the queue signal Q to be written next. As a result, the magnetization of the video tape (1) is reversed (from saturated north pole to saturated south pole), and this reverse direction signal ends at the end of gate pulse g. Here, the end point of the gate pulse g is set to be the original S pole, so even if the reverse direction signal ends, the S pole remains on the CTL rack (3). In this way, a new cue signal (if) is recorded, and when it is reproduced, a new cue signal ql is obtained as shown in FIG. 4(E).

Next, as another example, the case where the time interval of the CTL signal rate signal q2 is T3 is shown in FIG. 4(F).
In this case, a new cue signal is recorded in the same manner as described above, as shown in (G). However, in the conventional example described above, the north pole of magnetization was reversed to the south pole midway through, but in this example, as shown in FIG. )
As shown in , even if the N pole that has already been recorded ends and becomes the S pole, the signal in the same direction is still being applied to the CTL head (8).
) is reversed to a north pole. CTL head (6
) is reversed by the cue signal Q, the magnetization is reversed to the south pole, and when the signal ends, the original south pole remains.

When this is reproduced, a new cue signal q2 delayed by the CTL signal rate time T3 is obtained as shown in FIG. 4(G).

[Problems to be Solved by the Invention] By the way, when recording an address signal or cue signal on the CTL rack (3) as described above, or rewriting an already written cue signal, it is necessary to In addition to when (1) is recorded and played back on the same VTR,
The videotape (1) is rewritten as described above on another VTR and played back on the original VTR, or recording and playback as described above is performed between three VTRs. It is also conceivable that various types of compatible recording/playback may be performed. When such compatible recording session playback is performed, if the width of the CTL head (6) is
If there is variation between the R, there will also be variation in the width of the CTL recording track (3), which will generate false signals during compatible playback, resulting in incorrect reading of the cue signal and damage to the rotating head and capstan. A problem arises in that rotation control is disturbed. An example will be explained below.

Figure 6 shows how a videotape recorded on a first VTR with a narrow CTL head is transferred to a second VTR with a wide CTL head.
FIG. 6 is a diagram showing a case where the cue signal is rewritten by the TR and this portion is played back again by the VTR. That is,
As shown in FIG. 6(A), the CTI of the videotape (1) recorded by the first VTR with a narrow CTL head,
) The width of the rack (3) is a, and this videotape (1)
As shown in the same figure (A), the wide CTL head (8)
Assuming that the width of the CTL track (3) when the cue signal is rewritten in the second VTR with the 2nd VTR is b, and this part is to be played back again with the CTL head (6), as shown in Fig. 6 (A). As shown, the sixth magnetization is applied to the saturation magnetization N-pole and S-pole in the roughly hatched areas in the same manner as described above.
When the recording signal r shown in Figure 6(C) is applied to the CTL head (+3), new saturation magnetization north and south poles are formed in the densely shaded areas in Figure 6(A). . As can be seen from this figure, the width of the newly recorded CTL track (3) is wider than the width a of the original CTL track (3), and in this example, it is wider by (ba).

When a videotape (1) having a CTL rack (3) formed in this manner is played back using the same CTL head (6), the playback output of the CTL amplifier (9) is as shown in Figure 6 (D).
As shown in FIG. 2, a false signal S appears in addition to the CTL signal and the cue signal q. In this example, the level of this false signal S is 20fLOg-T with respect to the CTL signal -bell.
−c d B ).

The value of a is 750 I for VH5 type VTR (7)
L is the standard, but variations of about ±100 rivers occur due to variations in the width of the CTL head as described above, misalignment of video tape running, etc.

Therefore, for example, a=750#L, b=(750+1
00) p, the false signal S is 20JL
It occurs at a level of o g −'−= −17,5dB.

Also, a= (750-100) g, b= (75
In the case of a river (0+100), the false signal S reaches -10 dB.

When the CTL signal containing such a false signal S is amplified by the positive polarity amplifier (lO), the false signal S also becomes a pulse Bs which is indistinguishable from the CTL pulse Bc, as shown in FIG. 6(E). If this happens, the control of the rotary head or capstan will be disrupted, causing a problem that it will no longer operate normally.

As mentioned above, the width of the CTL track (
3) The playback output from the head also varies. Therefore, the gain of the CTL amplifier (8) is generally set to be sufficiently large, and when the reproduction output of the CTL head is large, the output of the CTL amplifier (9) reaches a saturation region and the peak of the reproduction output is clipped. In this case, the false signal S has substantially increased as a CTL signal, and the positive polarity amplifier (
10) False pulses S are more likely to occur in the output. In addition, since variations occur in the playback output of the CTL head as described above, naturally the output level of the CTL amplifier (3) also varies, so there is a difference in the output level, especially when the output level decreases. The threshold level of the positive polarity amplifier (lO) is set sufficiently low so that the positive polarity amplifier (lO) always receives a CTL output pulse even when the false signal S is small. This will generate false output pulses.

The above example shows an example in which the false signal S appears as the same polarity as the CTL signal signal.
) Various combinations of rack width and CTL head width,
The position of the cue signal to be rewritten and the position of the original cue signal before being rewritten (in the above example, the position of the original cue signal was the position shown by qo in FIG. 6(B)).
If we consider various combinations of (the phase is changed to a position delayed from qo as shown in q in the same figure (D) by rewriting), it will not necessarily be like the above example,
The false signal S may appear with the same polarity as the cue signal q. In this case, a pulse due to the false signal S is generated in addition to the cue signal pulse in the negative polarity amplifier (14), causing a problem that the cue signal is read out incorrectly.

This invention was made to solve the above-mentioned problems, and in the case of compatible recording/playback, it is possible to reduce the influence of the above-mentioned false signals, and it is also possible to stabilize the playback output from the CTL rack. The purpose of the present invention is to provide a magnetic recording/reproducing device.

[Means for Solving the Problems] The A1 recording and reproducing apparatus according to the present invention includes an automatic gain control circuit that amplifies a CTL signal reproduced from a control track to an unsaturated desired level, and an output signal of this circuit. is equipped with an amplifier circuit having a threshold at a level that can remove false signals inputted to the CTL, and the output of this amplifier circuit is
It is designed to be output as a signal.

[Operation] The gain of the automatic gain control circuit according to the present invention is controlled so that the peak values of the CTL signal and the address signal are at an unsaturated level or a level just before saturation. In addition, the amplifier circuit cuts out false signals contained in the input signal, and the original CTL
Output only the signal.

[Embodiment 1 of the Invention Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
In the figure, the same symbols as those in the conventional example shown in FIG. 3 indicate the same components, and (15) is the peak value detection circuit, (18) is the time constant circuit, and (17) is the variable gain CTL.
It's an amplifier. Furthermore, Fig. 2 is a waveform diagram for explaining the operation of this embodiment, and Fig. 2 (A) shows a variable gain amplifier (1
7), the figure (B) is the output waveform of the positive polarity amplifier (10), and the figure (C) is the output waveform of the negative polarity amplifier (14).

Next, the operation will be explained. A case will be described in which the cue signal is rewritten as described in FIG. 3 of the conventional example above, and the output of the CTL head (6) as described in FIG. 6 is obtained, for example. The method is carried out in exactly the same manner as the conventional example shown in FIG. 3, so a description thereof will be omitted. Now, the signal reproduced from the CTL head (8) passes through the switcher (8) to the variable gain C
is applied to the TL amplifier (17), and its output A (Fig. 4 (
A) As shown) is a positive polarity amplifier (lO), a negative polarity amplifier (
14) and a peak value detection circuit (15). The peak value detection circuit (15) is composed of, for example, a diode and a capacitor, and the CTL signal type O detects the peak value of the cue signal qo, and the detection output is applied to the next time constant circuit (1B), where smoothed by . This smoothed output is returned to the variable gain CTL amplifier (17) as a control signal to control its gain. The gain is controlled by using, for example, an amplification transistor in the amplification stage constituting the variable gain CTL amplifier (17), and by changing the base current and controlling hfe (current amplification factor) to change the gain. Variable gain CTL amplifier (17), peak detection circuit (15)
The variable gain CTL amplifier (
! 7) The maximum value of the signal output can be set almost to the saturation level. For example, as shown in FIG. It can be set slightly less than that. In this way, for example, a false signal sl of a level as shown in FIG. 6(A),! ! 2 is CTI, signal C
or -17,5 as above for cue signal q
dB is held at a value of -10 dB, and video tape (
Even if the reproduction output of the CTL head fluctuates due to changes in the contact state between the CTL head 1) and the CTL head (8), the peak value of the CTL signal C or the cue signal q is maintained close to the saturation level. The output of the variable gain CTL amplifier (17) obtained in this way is amplified by the next stage positive polarity amplifier (lO) and negative polarity amplifier (14), but these amplifiers (10), (14) By choosing the threshold level Vth of FIG. 2(B) above the level of the false signal Sl or S2 shown in FIG.
) and (C), the CTL signal C
and an output pulse Bc in which only the cue signal q is amplified,
Q is obtained. Here, the threshold level vth
If the level is set higher than -10 dB, for example, about -6 dB, with a margin, even if the variation becomes larger, it can be handled.

By doing the above, even if the playback output of the CTL head fluctuates due to changes in the speed of the tape during playback, the same effect can be achieved for fast forward playback and slow playback. A similar effect can also be achieved in detecting cue signals during early spring return. In addition, ordinary VT does not have cue signal recording or playback functions.
Also in R, since the output of the CTL amplifier (17) can be stably extracted, control of the rotating head, etc. becomes more reliable.

The time constant circuit (16) in the above embodiment changes its time constant according to the speed of the video tape, that is, the tape speed during fast forward playback, slow playback, fast forward play, early spring return, etc. (1) For example, if the tape speed becomes faster, The feedback loose response may be made faster by decreasing the time constant.

Furthermore, in the above embodiment, the peak value of the output signal of the variable gain amplifier (17) was set to be near the saturation level.
An amplifier may be further inserted after the variable gain amplifier (17) so that the peak value of the output signal of the amplifier is brought close to the saturation level.

[Effects of the Invention] As described above, according to the present invention, the CTL head reproduction output is passed through the variable gain CTL amplifier, the gain is controlled so that the maximum output level is near the saturation level, and the output signal is Since the threshold voltage of the amplifier that takes out the CTL signal and cue signal from the CTL signal is set to a value higher than the level of the false signal included in the output signal, compatible recording and playback allows the CTL signal to be output even if the rack width changes. Since the level difference that can separate the false signal contained in the signal from the CTL @ signal and cue signal can always be maintained, the false signal can be removed and the original CTL signal and cue signal can be extracted. This has the effect of providing a magnetic recording/reproducing device in which the rotational control of the capstan and capstan is not disturbed.

[Brief Description of the Drawings] Fig. 1 is a block circuit diagram of an embodiment of the present invention, Fig. 2 is a waveform diagram for explaining the operation of this embodiment, and Fig. 3 is a diagram of a conventional magnetic recording/reproducing device. A block circuit diagram of the CTL signal recording/reproducing system, Fig. 4 is an output waveform diagram of each part of this conventional example, Fig. 5 is a diagram showing a video tape recording pattern, Fig. 6
The figure is a waveform diagram for explaining the reason why false signals occur during compatible recording and reproduction. (8)...CTL head, (lO)...Positive polarity amplifier, (14)...Negative polarity amplifier, (15)...Peak value detection circuit, (1111)...Time constant circuit , (17
)...Variable gain CTL amplifier. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A variable gain control amplifier that amplifies the playback signal of the control head, a peak detection circuit that detects the peak value of the output signal of this amplifier, and a peak detection circuit that smoothes the output signal of this circuit and outputs it to the variable gain control amplifier. A time constant circuit that feeds back and controls the gain of the amplifier to a high level that does not saturate the output signal of the amplifier, and a time constant circuit that controls the output signal of the variable gain control amplifier to a level of the false signal contained in the output signal. A magnetic recording and reproducing device equipped with a control signal reproducing system having a positive polarity amplifier and a negative polarity amplifier that amplify even at a higher threshold voltage. (2) A magnetic recording and reproducing apparatus according to claim 1, wherein the time constant of the time constant circuit is configured to change depending on the running speed of the video tape.