JPS6038751A - Tracking device of video tape recorder - Google Patents

Abstract

PURPOSE:To facilitate considerably a tape travelling control operation when the VTR parts are assembled by performing the tracking control based on the information only on some sections of a video track. CONSTITUTION:A pulse of width T1 is produced from a pulse generating circuit 32 with a delay of time Td compared with a head switching pulse. The output of a voltage comparator 21 is sampled by the pulse T1. This sampled output is held for the period of are field to eliminate the complicated tape driving control. In other words, the error information obtained from a video track is used as a tracking detecting signal after sampling it at a fixed position and for a fixed time width. Furthermore, the tracking detection output corresponding to the track linearity is extracted by shifting the sampling point to facilitate the easy checking of the linearity of a track pattern.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a tracking device for a video tape recorder, and more specifically, it records a video signal by superimposing a pilot signal, and uses a rotating magnetic field based on the pilot signal obtained during playback. The present invention relates to a tracking device for a video tape recorder that performs head tracking.

[Technical background of the invention]

Conventionally, in a helical scan video recorder (hereinafter referred to as VTR), when performing tracking control so that the rotating magnetic head accurately scans the recording track (video track), control No. 40 recorded on the tape is used. There is. That is, during recording, a control signal is recorded on the side edge of the tape along its length, and during playback, the tape feed is controlled so that the phase of this control signal matches the phase of the reference signal. In this way, the rotating magnetic head can accurately scan the video track. However, if the recording position accuracy of the control signal or the video track was insufficient, or if the track linearity was poor, tracking could not be achieved when the tape was played back between different devices. arise. Therefore, in general, the phase control of the control signal is not fixed to a constant value.
By providing a tracking volume that can vary the phase stability point of the control signal and adjusting it, tapes can be made compatible with different devices.

By the way, for users who don't know how to adjust the tracking volume or find it troublesome, there is a VT that can automatically adjust the tracking volume.
R has been proposed. One method is to superimpose and record four different frequency pilots (number i) on the video track together with the video signal, and during playback, use the playback pilot signal to determine whether the rotating magnetic bed is shifted to the front or back of the video track to be scanned. There is a method that detects whether the head is moving and controls the tracking phase of the head based on the detected output.

A VTR tracking device using these four pilot signals will be explained in detail below.

FIG. 1 is an example of a tape recording pattern of V'l having the above-mentioned tracking device. In this case, there is no traditional control track. Tape (1) has video tracks (2J, (3), f4), (5), (6), (
7) Places are formed in order. Track (21, (
4L (6) is recorded by one of the two rotating magnetic heads (head A), and track (3)
), (5), f was recorded by the other head (head B). These tracks are recorded with a pilot signal superimposed on the video signal.
As mentioned above, these pilot signals are recorded on the video tracks in the predetermined order of the four different frequency pylons (M numbers), that is, tracks (2) to (7).
) have frequencies 'l+r2. fs, '4
+ r,, rt (hereinafter et al.

f4. ...) pilot signals are superimposed and recorded on the video signal. Note that arrow A indicates the tape running direction, and arrow opening indicates the scanning direction of the rotating magnetic head.

During reproduction, a rotating magnetic head scans, for example, a track (5) as shown in the figure. At this time, this head B receives the pilot signal P of frequency f4 recorded on track (5).
(f4) (and video signal), and at the same time, pilot signals P(fl) and P(fl) with a frequency of 13°f are played back from tracks (4) and (6) on both sides, respectively. Since the frequency is low and the influence of azimuth loss is small, the pilot signals of adjacent tracks are also reproduced at the same time). Next, these signal outputs are detected by the tracking device shown in FIG. 2 to create signals for tracking control.

Next, the operation of the circuit shown in FIG. 2 will be explained. Rotating magnetic head A
, B are respectively transmitted through a rotating transformer (ll
a) a regenerative preamplifier (12a) via (ub);
(12b) and further input to the switch SWI, which is opened and closed by the head switching pulse inputted from ☆;M child 00).
The outputs of amplifiers (12a) and (12b) are taken out alternately from I, and this output is fed to a bandpass amplifier (BPA) α3).
1, and this pilot signal output is input to the automatic gain control (AGC) circuit 04).
The signal is input to the same frequency as the pilot signal, whose amplitude is adjusted, and then supplied to heads A and B during recording.
The converted pilot signals, which are also in the same order, are input to a balanced modulator (BM) αQ supplied from the terminal α9 and subjected to balanced modulation. At this time, if the frequencies of the pilot signals P (fl) to P ('4) are determined as shown in the table below (the converted pilot signal naturally has a frequency equal to each of these pilot signal frequencies) , this BM (15) provides signals with frequency components of 3fH and fH.

For example, when the head B is scanning the track (5) as shown in FIG. 1, the pilot signal P ('4) of the same wave number f4 is reproduced from the track (5) as described above.
And from adjacent tracks (4) and (61 on both sides, pilot signals P(ra) and P(fl) of frequency r'l are reproduced, respectively. At this time, the converted pilot signal is the same frequency as the pilot signal P(f4). The converted pilot signal is supplied to the terminal (f51 to 13M (lfil) (it is like this because the servo is applied). Therefore, the above frequency components are synthesized from BM (IG),
In this case, the frequency component If4- corresponding to the advance of the tape
Frequency component 1f corresponding to f11 signal and tape delay
, -f, l signals are obtained. In addition, track (5)
The frequency component corresponding to the scanning becomes zero (f4-f4=
O).

The level of the signal having frequency components of 3fH and fH from BM Q5 is determined by the scanning of head A or B to the left or (
However, fIl (horizontal synchronization frequency) is the amount of shift to the right and the proportional magnitude of the shift. That is, depending on whether the scanning of head A or B is delayed or advanced, the level of one of the signals having frequency components of 3fH and fH will be higher than the other. As can be seen from the table, the frequency components corresponding to delays (or advances) are inverted in heads A and B, but this can be done by switching switch SW2 using a head switching pulse, as will be described later. As shown in FIG. 3, track deviation up to one track pitch can be obtained as a substantially linear phase difference detection output.

The output of BM (1G) is passed through a band pass filter (BPF) to extract the frequency components of fH and 3f1 (
) ft7), (18). BPF ft7)
The signals having frequency components of fH and 3fH extracted from the field are detected in level by level detectors (19, (21), respectively, and input to the switch 8W2. As described above, this switch 8W2 is Since the frequency components corresponding to the advance and lag of heads A and B are reversed, this is used for switching between them.In other words, head A
When playing back with head B, the frequency component corresponding to the advance is 1fH (the delay is 3fH), and when playing with head B, it is 3fIi (the delay is fH), so this switch SW2 is 3rH13 when A is playing
The output of PF (18) is switched to the ten terminal of the voltage comparator (21), and the output of fHBPF ft7) is switched to one terminal of the voltage comparator eυ (i.e., switch ≠ S
W2 is connected to terminal a), and when head B is playing, it is exactly the opposite (switch 8W2 is connected to terminal a).
connected to the side). Voltage comparator (21)
Then, the signal levels of the frequency components of fl-1°3fxt are compared, and the difference is output. This phase difference output is the reference rep/l/,! Since the capstan motor that drives the tape is activated by automatic phase control (APC), heads A and B are tracked to accurately track their own video tracks. That is, the tape feed is controlled so that the two signal levels representing the frequency components of fH and 3fl-1 are the same or have a constant pressure difference.

Note that the terminal o2 in FIG. 2 is a playback video output terminal.

[Problems with background technology]

The above-mentioned tracking device has a drawback in that even if an attempt is made to adjust the tape running system during tape running adjustment during VTR assembly, changes corresponding to the adjustment movement cannot be clearly observed. In other words, since the above-mentioned tracking control is performed even when adjusting the tape running, even if the adjustment is not good and the tracking is incomplete (tracking deviation has occurred), the tracking information from the head will cause shift feedback), You end up controlling it. Therefore, even if an attempt is made to adjust the original tape running by moving the tape guide of the tape running system, the effect of moving this guide cannot be seen and the correct running adjustment cannot be made.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a tracking device for a video tape recorder that can easily adjust the running angle of the tape.

[Summary of the invention]

In the present invention, a plurality of pilot signals each having a different frequency value are sequentially superimposed on a video signal and supplied to a rotating magnetic head in a predetermined order so that one type of pilot signal is recorded for each recording track. In a tracking device for a video tape recorder, a control signal is created by recording on a tape, and a pilot signal obtained during playback is used to track a rotating magnetic head. The above-mentioned tracking is performed based on information of only a partial section on the time axis.

[Embodiments of the invention]

An embodiment of a tracking device for a VTR according to the present invention will be described below with reference to diagram M4. In FIG. 4, the same parts as those in FIG. 2 are designated by the same reference numerals, and the explanation thereof will be omitted. In FIG. 4, C3) is a sampling circuit, and a delay pulse generation circuit outputs a pulse of width Ill after a predetermined time (Td) delay from the rising and falling edges of the head switching pulse. During the pulse generation period, the output voltage of the voltage comparator (21) is sampled. θj
is a hold circuit that holds the sampled value of this sampling circuit 01) for one field period. This output is input to the non-inverting input terminal of the operational amplifier.

On the other hand, the capstan A is connected to the inverting input terminal of the amplifier.
FC (automatic frequency control) output is input from terminal 01. The output of this operational amplifier (b) is the motor drive amplifier 06
), and the output of this amplifier C is input to the Sarani Cab Zutan Motor 07).

Next, the operation of the apparatus shown in FIG. 4 will be explained along with an adjustment method based on an example of the tape running system shown in FIG.

In FIG. 5, (41) is the tape cassette 7), and (41) is the tape cassette 7).
4ri to (4 seconds is a tape guide, (19) is a tape guide drum with a rotating head, 00 is a full width erase head,
(51) is an audio head, (52) is a capstan, and (53) is a pinch roller. By the way, in order to load the tape (1) diagonally on the tape guide drum (=lil), the tape (1) must be lowered by the video track length in the tape width direction from the tape guide (i~(TSUKDA-\). Therefore, when adjusting the tape guide (43 to
In other words, the envelope output of the portion corresponding to the writing start portion of the head changes.

Figure 6(a) shows the voltage comparator (21) of the conventional device shown in Figure 2.
An example of the output (phase control output) is shown below. In this case, adjust the envelope output by adjusting the tape guide (43 to However, as described above, since feedback is automatically applied, the change occurs as shown by the dotted line (62), for example.As a result, it is not clear whether the adjustment of the tape guide has an effect or not.

6) is another example of the output of the voltage comparator Cυ in FIG. In this case, adjust the tape guides (4G to 4G) and the audio head (51). This will greatly change the envelope output on the upper side of the tape, that is, on the exit side.

For example, the output before adjustment shown by the solid line (E) changes as shown by the dot (E). In this case as well, although it would originally be as shown by the dashed line (2)), the feedback becomes stronger due to the eye movement and changes as shown by the dotted line (b). Therefore, the above-mentioned drawbacks occur.

In this example, from the head switch
A delayed pulse of width T (see FIG. 6(C)) is generated by the pulse generating circuit C3, which samples the output of the stain pressure comparator Qυ and converts it to 1 By holding the field period, it is possible to eliminate the difficulty in adjusting the running of the tape. That is, error information obtained from one video track is sampled at a certain position and over a certain time period and used as a tracking detection signal. Therefore, for example, if the output of the voltage comparator (21) is sampled and controlled by a node as shown in FIG. 6(C), the phase control output of the voltage comparator (2I) will be as shown in FIG. 6(C).
The solid line (66) shown in d) becomes like the dotted line (a).

Therefore, the effect of adjusting the running of the tape at the beginning and end of writing becomes obvious and the adjustment becomes easier. especially,
Tape guide the point at which the output of the voltage comparator Qυ is sampled.

Place the sampling point in the center of the tape, which is difficult to change by adjusting the Place it in (
Extend the delay time Td of the pulse generator >), tape guide (4119 to (4υ) and audio head (51)
By placing the sampling point near the beginning of the recording on the tape, the effect of the adjustment will be visible and the adjustment will be easier.

Note that in FIGS. 6(a) to 6(d), the horizontal axis represents time.

〔Effect of the invention〕

As described above, according to the present invention, among the information obtained from the pilot signal recorded on the video track,
By performing tracking control based on information on only a partial section of the video track, tape running adjustment work when assembling VTR products becomes much easier. Furthermore, by moving the sampling point, a tracking output corresponding to the linearity of the track can be obtained, making it easy to check the linearity of the track pattern.

[Brief explanation of the drawing]

Fig. 1 shows an example of a tape recording pattern of a VTIL with a conventional tracking device, Fig. 2 shows an example of a conventional tracking device, and Fig. 3 shows the phase difference of the voltage comparator shown in Fig. 2. (FIG. 4 is a diagram showing an embodiment of a tracking device for a video tape recorder according to the present invention; FIG. 5 is a diagram showing an example of a tape running system of a video tape recorder); The figure is a diagram for showing the characteristics of the apparatuses shown in FIGS. 2 and 4. 13... Bandwidth amplifier. 16...Balanced modulator. 17, 18...Band pass filter. 19, 20... Level detector. 21...Voltage comparator. 31...Sampling circuit. 32... Delayed pulse generation circuit. 33...Hold circuit. 34...Operation amplifier. 37... Capstan motor. A, 13...Rotating magnetic head. Agent Patent attorney Kensuke Norichika (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 5 Figure 9 Figure 4 Figure 6 ■Field period

Claims (1)

[Claims] A plurality of pilot signals, each having a different frequency value, are sequentially supplied to a rotating magnetic head along with a video signal in a predetermined order so that a type of pilot signal is recorded for each recording track, and recording is performed on the tape. In a tracking device for a video tape recorder, a control signal is created using the obtained pilot signal, and a rotating magnetic head is tracked using this signal.
A video tape recorder tracking device comprising means for performing the above-mentioned tracking based on a control signal for a partial section on a time axis of a recording track.