JPS61192058A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To enable fine slow reproduction even with tracking systems using 4 types of pilot signals by providing a means of obtaining positional pulse signals (pseudo CTL signals) varying according to the voltage of tracking error signals generated in the fine slow lay mode, especially in the constant speed section. CONSTITUTION:Signal (F) that is high during the field period in which the head scans in the constant speed section is given to the delayed pulse generating circuit 14 through the terminal 9. Pulse is generated, for example, around at the middle between the leading end and the trailing end of the signal (F), and input to the pulse position varying circuit 12, which changes the position of pulse generated by the delayed pulse generating circuit 14 depending on the potential at the output terminal of the amplifier 11. Thus, output signal (J) and the pseudo CTL signal are available at terminals 12 and 15 of the pulse position generating circuit 12. The pseudo CTL is used instead of conventional CTL signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a magnetic recording/reproducing device (hereinafter referred to as VTR) that uses a rotating head to sequentially record and reproduce signals on a magnetic tape as an inclined discontinuous recording trajectory. In particular, this invention relates to a VTR that performs tracking control using pilot signals.

Conventional technology First, in a conventional tracking method using a CTL signal, a magnetic tape is driven intermittently, and still playback is performed with the degraded part of the playback output located near the vertical blanking (V blanking) part. The so-called fine-throw reproduction, which obtains a reproduced image with a good S/N ratio, will be explained with reference to FIG.

Now, during the period from to to tl, the capstan motor that controls tape feeding is controlled to be accelerated, and after the acceleration period ends, a constant speed period (slower speed than normal) is entered from t1.

During this constant speed section, a CTL signal written every frame is detected at the end of the tape in a temporally constant relationship with the on-track position during recording, and after a certain period of time from the point 1C when the CTL signal is detected. The tape is fed at a constant speed until t2, and from t2 to t3, the capstan motor is braked and enters the deceleration section, then stopped and enters the still state. After repeating the still state several times according to the slow ratio, The above operation is repeated again to perform fine slow playback.

FIG. 7 shows the head scanning locus with respect to the track during fine-slow playback. From the still state (■), when entering the acceleration section, scanning shown by (■) is performed, and then when entering the constant speed section, The scan shown by (2) is performed, and when the deceleration section is entered, the scan shown by (2) is performed, and then the head scanning trajectory becomes as shown by (2), resulting in a still state.

The above is the principle of fine slow playback in the conventional tracking method using the CTL signal.As can be seen from the above, the K'' CTL signal is a reference signal essential for controlling the still stop position.

Next, an outline of a tracking method using four types of pilot signals, which is adopted in 8 mm video that does not use a general CTL signal, will be explained.

During recording, four types of pilot signals 11 to f4 are sequentially switched for each field and recorded while being superimposed on the video signal. The recording order of the pilot signals is <f1→f2→f3→f4 as shown in FIG. 3, and one type of pilot signal is continuously recorded within one field period.

The frequency of the pilot signal is set to a value shown in Table 1, for example.

Table 1 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6,5 fH indicates a frequency that is 6.6 times the frequency of the horizontal synchronization signal.

Next, we will discuss playback.

Since the pilot signal is a relatively low frequency signal, the pilot signal recorded on an adjacent track is also reproduced as a crosstalk signal.

Now, when the head regenerates and scans the track on which the pilot signal f3 is recorded, f2° f 3 +
The composite signal of f4 is reproduced. This composite signal and a reference pilot signal (a signal with the same frequency as the pilot signal recorded on the main scanning track) are balanced-modulated to extract a signal with a difference frequency.

The difference frequency signals are fH and 3fH signals as shown in FIG. When the head scans a track on which pilot signals fl and f3 are recorded, those on the right side are 3fH. Furthermore, when the head scans a track on which the pilot signal f 2 r f 4 is recorded, the left-right relationship is opposite to that described above. If the reproduction levels of both fH and 3fH signals obtained by this balanced modulation are compared by a comparator circuit, the signals after comparison are as follows.
It includes information on the amount of track deviation and the direction of deviation. This signal is used as a tracking error signal to control the relative position between the recording track and the reproducing scanning locus of the reproducing magnetic head.

The above is an overview of the tracking method using four types of pilot signals.

Problems to be Solved by the Invention However, even in the above-mentioned tracking method that does not use a CTL signal, there is a problem in performing fast-low reproduction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording/reproducing apparatus which can perform fine slow reproduction similar to that using a CTL signal even in a tracking method using four types of pilot signals.

Means for Solving the Problems The present invention is configured to use four types of pilot signals to control the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head. Position nox signal (hereinafter referred to as pseudo CTL signal) according to the voltage value of the tracking error signal obtained in the fast section
This is a magnetic recording/reproducing device having means for obtaining the following information.

Effect Since the tracking error signal includes information on the amount of track deviation, fine slow playback becomes possible by using a pseudo CTL signal whose generation position changes depending on the voltage value of the tracking error signal.

Example First, Figure 4 shows the head scanning trajectory when scanning a track on which four types of pilot signals are recorded when fine slow playback is performed under normal conditions. Operation waveforms are shown in FIG. 6 and will be explained. In order to obtain the tracking signal shown in FIG. 6, the pilot signal f4 is used in the constant speed section, and the pilot signal fl is used in the other scanning sections as the above-mentioned reference pilot signal.

Currently, a still scan (■) is being performed on the track where fl is recorded. When the vehicle enters the acceleration zone from this state, the scan shown by ■ is performed, and when the vehicle enters the constant speed zone, the scan shown by ■ is performed. During this scanning, the head scans the track where f2 is recorded in a nearly on-track state.

Next, when entering the deceleration zone, the scan shown by ■ is performed and 1
It stops on the track where f3, which is a frame away, is recorded, and performs still scanning.

After repeating this still scanning multiple times according to an arbitrary slow ratio,
head scanning is performed, still scanning is performed on the track where fl is recorded, and the above operation is repeated.

Further, ■, which scans in the constant speed section during fine slow playback between 07 and 06, scans on the track where f3 is recorded.

FIG. 6 is obtained during the fine-throw playback. fH obtained by balanced modulation as shown above.

3 shows a knocking error signal comparing the reproduction levels of both signals of 3 f H.

In FIG. 5, the potential v0 indicated by the center of the tracking error signal represents the potential of the tracking error signal when scanning the center of the track in normal reproduction, that is, when scanning is performed while on-track.

Tracking error signal 2 during fine slow playback scanning at ■−■−■−■−■1■′−■′−
The tracking error signal during fine slow playback scanning at ■'-■'-■ is inverted with respect to vo.

This is because the pilot signal f4 in the constant speed section and fl in the other scanning sections is used as the reference pilot signal, and during scanning from ■-■-■-■-a,
This is because, on the paper, the relationship between the difference between the reference pilot signal and the frequency of the left and right tracks (fH and 3fH'') is reversed during scanning from -1 σ -1 ■'.

The above is an explanation of the head scanning locus and changes in the tracking error signal when fine slow playback is performed.

The present invention detects the tracking error signal shown in FIG. 5, especially the potential of the tracking error signal obtained when scanning in a constant speed section, that is, the value of vl that changes from vo, and uses this detection signal to A pseudo CTL signal is created to replace the CTL signal.

An embodiment of the present invention for creating a pseudo CTL signal is shown in FIG. 1, and FIG. 2 shows an operational waveform diagram of the main part of FIG. 1, and will be described.

A tracking error signal (a) during fine slow playback is input to an analog inversion circuit 2 via a terminal 1, and its output is applied to one input of an analog switch (SW-1) a. For the other input of (SW-1)3,
The aforementioned tracking error signal (a) is input as is.

Furthermore, this tracking error signal (a) is input to the sample and hold circuit 4. From the terminal 6, a signal (b) which becomes Hi during the acceleration section, constant speed section, and deceleration section is input, and is applied to the sample pulse generation circuit 6. The sample pulse generating circuit 6 is configured to generate a pulse signal at the falling edge of the signal (b). One of these sampling pulses is input to the sample and hold circuit 4, and the tracking error signal is sampled and held. This sampled and held output is input to a waveform shaping circuit 7 which generates a Low output if it is lower than the threshold value v0, and a Hi output if it is higher. Now, the tracking error signal during the period of head scanning ■−■−■−■ is expressed as the sample pulse (
/The voltage sampled and held now is lower than vo, and the voltage obtained by holding the tracking error signal in the period of -1σ-a by the sample pulse e→te sample thread is higher than vo.

Therefore, from the output of the waveform shaping circuit 7, the head scanning ■-
Low in the period of ■−■−■, head scanning ■′−■′−
High during the period ■'-■', and Low again during head scanning ■.
) can be obtained as an output signal w.

) to this output signal, the analog switch (SW-1
)3 is used as a switching signal.

Analog switch (SW-1) 3 has an output signal (L).
When it is OW, the tracking error signal inputted from the terminal 1 is output as it is, and when the output signal () is Hi, when it is 0, a signal obtained by inverting the tracking error signal (A) by the analog inverting circuit 2 is output. Therefore, the output of analog switch (SW-1) 3 is head scanning ■-■
−■−■ and head scanning■′−■′−■′−
In the period up to (2)', as shown by the output signal (E), the operating output has almost the same polarity and level change.

A signal (to) that becomes HL only at the timing when the head scans in a constant speed section is inputted from the terminal 9 to a sample pulse generation circuit 1o configured to generate a pulse signal at the rising position of the signal (to). From this output,
Obtain the sampling pulse (g). This sampling pulse (g) is input to a sample and hold circuit 8, and the output signal (e) of the analog switch (SW-1) 3 is sampled and held. Output of sample and hold circuit (
The potential b) is the tracking error signal obtained when the head scans during the constant speed section, here, head scanning ■ and σ, and is the potential obtained when the head starts scanning on the track. be. Now, the position where the head starts scanning on the track during head scans ■ and ■' is slightly shifted to the right from the on-track position, so the potential v0 of the tracking error signal obtained during normal playback is
An output potential lower than V' potential is obtained from the sample and hold circuit 8. Note that if the position where the head starts scanning on the track during head scanning) and δ■ is the same as the on-track position, the output voltage (g) of the sample and hold circuit 8 is v0 potential, which is lower than the on-track position. , mentioned above. If it shifts to the left by the same amount as the shift to the right, the output voltage (A) will be ■. The V' potential becomes higher.

In this way, the output voltage from the sample and hold circuit changes in accordance with the amount by which the position where the head starts scanning on the track during head scans ① and q deviates from the on-track position.

This sample-and-hold output voltage (c) is input to the amplifier 11 and amplified. The amplifier 11 amplifies only the y level with the vo potential as a reference.
If the gain of is β, the output is configured to output a potential of v0±βV′ and to be output in the same phase.

A signal (to) that is input from the terminal 9 and becomes Hi only during the field period in which the head scans in a constant speed section is input to the delay pulse generation circuit 14, and for example, the signal (to) is inputted to the delay pulse generating circuit 14, and the signal (to) is set at approximately the center from the rise to the fall of the signal (to). A pulse signal is obtained near the position of , and this pulse signal is input to the pulse position variable circuit 12.

This pulse position variable circuit 12 allows the generation position of the pulse signal obtained from the delayed pulse generation circuit 14 to be adjusted by the amplifier 11.
An output signal (su) is obtained from the output of the variable pulse position circuit 12, and a pseudo CTL signal is obtained from the terminal 16, which is used in place of the conventional CTL signal.

The pulse position variable circuit 12 is configured to control the output β of the amplifier 11.
- The configuration is such that the pulse position moves left and right, responding only to changes in the V' potential, and furthermore, the output potential of the amplifier 11 is V. If it becomes lower, the generation position of the pulse output signal (su) will be
Move the amplifier 1 to the left according to the V' potential, and vice versa.
The output voltage of 1 is ■. When higher, the pulse output signal (
The configuration is such that the generation position of 2) is moved to the right in accordance with the β·V' potential.

With this configuration, the position at which the head starts scanning in the head scans (2) and (a) is f 2 + f
When the pulse output signal (IJ) shifts to the right from the on-track position of the track where the number 4 is recorded, the pulse output signal (IJ) moves to the left. Also, the position where the head starts scanning in the head scans ① and ②' is f2. If the on-track position of the track where f4 is recorded is shifted to the left,
The pulse output signal (su) moves to the right. This direction of movement is the same as when performing fine slow playback using a conventional CTL signal.

Further, the amount of movement of the generation position of the pulse output signal (S) can be changed by changing the gain β of the amplifier 110 according to the amount of deviation from the on-track position.

In this way, the pulse output signal (or pseudo CTL signal) obtained from the terminal 16 is equivalent to the conventional CTL signal, and fine slow reproduction is possible using the pseudo CTL signal◇Details of the invention As explained above, according to the present invention, stable fine-throw playback is possible even in a tracking method using a four-frequency pilot signal without using the conventional CTL signal. In the previous method,
An external tracking volume was required to absorb mechanical variations and adjustment errors, but this external tracking volume can be removed with a tracking method that uses a 4-frequency pilot signal.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a processing circuit that generates a pseudo CTL signal according to an embodiment of the present invention, Fig. 2 is an operation waveform diagram of the embodiment, and Fig. 3 is a recording in a tracking method using a four-frequency pilot signal. Pattern diagram, Figure 4 is a head scanning trajectory diagram when a recording track on which a 4-frequency pilot signal is recorded is played back in slow motion, and Figure 6 is a tracking error signal diagram when the head scan shown in Figure 4 is performed. FIG. 6 is a waveform chart showing the capstan speed during fine-throw playback, and FIG. 7 is a head scanning locus chart during fine-throw playback. 2...analog inversion circuit, 3...analog switch, 4, 8...sample hold circuit,
6, 10...Sample pulse generation circuit, 7...
...Waveform shaping circuit, 11...Amplifier, 12
...Pulse position variable circuit, 14... Delayed pulse generation circuit 〇 Name of agent Patent attorney Toshio Nakao Hagaichimeika 1rlA Figure 2 Figure 3 Figure 4r:! J Figure 5 Figure 6 Door Z2

Claims (1)

[Claims] During recording, a pilot signal for tracking control during playback is superimposed on the television signal to be recorded, and is sequentially recorded on the magnetic tape as close recording tracks by a rotating magnetic head. Due to the level difference in the crosstalk signal of the pilot signal reproduced from the front and rear adjacent recording tracks,
The present invention is configured to control the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head by detecting a tracking error, and when performing reproduction scanning at a speed mode different from the tape feeding speed during recording. A magnetic recording and reproducing apparatus characterized in that it has means for generating a pulse signal whose generation position changes according to the voltage value of a tracking error signal obtained during reproduction scanning.