JPS62109483A - Tracking device - Google Patents

Abstract

PURPOSE:To obtain a noise-free reproduced picture after a normal reproduction shifting by discriminating a pilot signal frequency which is recorded on a still reproduced track and advancing the generating phase of the reference signal by 180 deg. in accordance with the signal from the still reproduction to the normal reproduction shift. CONSTITUTION:When a signal f1 is recorded on a main scanning track at the time a still reproduction, an output 8 is on the H level. After releasing the still reproduction by detecting this H level, the reference signal generating circuit generates signals in the sequence of f2-f4 starting from f1. On the other hand, when a signal f3 is recorded on the main scanning track at the time of still reproduction, the output 8 is on the L level. After releasing the still reproduction by detecting this L level, the reference signal generating circuit advances by 180 deg. and generates signals in the sequence of f4, f1 and f2 starting from f3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tracking device for a video tape recorder (VTR), and particularly to a tracking device for a VTR [i] that performs tracking control using a four-frequency pilot signal. It is.

Conventional technology Conventionally, as a method for realizing noise-free still/L/(still image) playback of a 4-frequency pilot VTR, the amount of crosstalk between pilot signals recorded on tracks before and after the main scanning track is equalized. The magnetic tape was transferred intermittently and then stopped. Specific examples will be described below with reference to the drawings.

FIG. 6 is a recording magnetization locus diagram using the four-frequency pilot signal method. In FIG. 6, the message B1. M2゜B2.・・・
... is a magnetic tape with A head and B head.

Each recording track recorded above. Arrow 14 indicates the direction of tape transport. Each recording track has
Pilot signals indicated by f1 to f4 are sequentially recorded for each field together with the video signal. The frequencies of the pilot signals are approximately as shown in Table 1.

Table 1 f in Table 1 indicates the horizontal synchronization signal frequency. As shown in Figure 2, the pilot frequency difference between adjacent tracks of each recording track is f) 1% on the right side of the Ai track (i = 1.2...), and 3 fH on the left side of the B1 trunk. 3/Hs on the right side and fH on the left side.

FIG. 6 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In Figure 6, from terminal 15 there is a reproduction RF
A signal is input. Circuit 16 is a low-pass filter that separates the pilot signal from the reproduced RF signal. The pilot signal at this time is a composite signal of the main scanning track and the crosstalk components of the left and right adjacent tracks.

The circuit 17 is a balanced modulation circuit, and the aforementioned composite signal and the terminal 1
2 and the reference signal input from 2. The reference signal is a pilot signal having the same frequency as the main scanning track during reproduction (normal (normal) 1x speed).

In FIG. 6, when the head scans the 121-rack, the inputs to the balanced modulation circuit 17 are fz, f, , f4.

The reference signal is f3. Therefore, balanced modulation circuit 1
The outputs of 7 are the sum and difference signals of fz, f, f4 and f3, respectively. Circuit 18 is an fH tuning circuit,
Circuit 19 is a 3fH tuning circuit.

Circuits 20 and 21 are detection circuits, and circuit 22 is a comparator. Therefore, the pilot signal extracted as a crosstalk signal from both adjacent tracks is separated and extracted as a difference frequency signal from the pilot signal recorded on the main scanning track, and then sent to the detection circuits 21 and 22.
The comparator 22 outputs a signal corresponding to the level difference between the detected outputs to the terminal 1. fH
If the detected voltage of 13fH is vJH1v5fH, then V
When fH >'iJH (7), terminal 11 is ■VfH (V, f
When □, the terminal 11 becomes each potential of O.

The output of the terminal 1 includes information on the amount and direction of the red track deviation, so it can be used as a tracking error signal.

Circuit 23 is an analog inversion circuit, circuit 24 is an electronic switch, and head switching pulse (H3W pulse) 2
Switch at the level of . The aforementioned Toto (Ai) rack, B
In the IT-rack, the frequency difference (fH or 3fH) between the main scanning track and the adjacent track has an inverse relationship with respect to the head displacement direction, so for example, when playing the Ai track, the output of terminal 1 is output as is to the terminal 25, and when reproducing the Bi I-rack, is outputted to the terminal 26 through the analog inverting circuit 23. For this reason 2
The output of 6 is Ai, Bi) If the head deviates from the track in the right direction in Fig. 5 regardless of the rack, the potential of
In the left direction, the potential of O is output. Therefore, if the tracking error signal obtained at 25 is supplied as the phase error signal of the gear bus stun motor and the tape speed is controlled,
The head always scans on-track to the main scanning track.

Next, still playback will be explained.

FIG. 7 shows the recording track and the center scanning locus of the head during still operation. Same figure BI+A2, B
2, . . . are each recording track, and fz.

f, . . . indicate pilot signals recorded on each recording track. Arrow 14 indicates the tape transport direction, and arrows 27 to 30 indicate head center trajectories in various still states for each track.

FIG. 8 shows the positional relationship between the rotating drum and the head, where 31 indicates the rotating drum and 32 indicates the drum rotation direction. Normal playback uses heads A and B with different azimuth angles, and still playback uses head A/head with the same azimuth for field still playback. In Figure 7, the playback RF signal is at its maximum at the head scanning trajectory of 26.30. Noise-free field still playback can be achieved.

FIG. 9 is an example of a circuit block for detecting the positional relationship between the head and the recording track, such as 26.30 in FIG. 1.
2 is the tracking error signal and H3W corresponding to Fig. 6.
33 is a sample and hold circuit (S/H)
, 36 is a monostable multi-pipe rake (MM), and the tracking error signal is generated from the H8W pulse by the sampling pulse (the center of the rising and falling edges of the H3W pulse) generated by the MM35.
to hold the sample. 36.37 is a comparator,
3B and 39.40 are resistors that create a reference potential for the 36.37 comparator.

When the head scanning trajectory shown in Figure 7 26.30, that is, noise-free field still reproduction is realized, the output terminal 4
1 is configured to output the scanning locus of ■potential 27, 28, 29, that is, when noise appears on the screen, the ■potential is output, and the magnetic tape is intermittently transferred so that the terminal 31 is at the ■potential. By stopping the camera, you can achieve noise-free field still playback.

Fig. 10 is a waveform diagram of each part in Fig. 9, Δ is the H8W pulse, bLL is the sampling pulse generated by M M 35, c1+'2+ ...... is the scanning trajectory #26 to 30 of the head in Fig. 7 Output waveform of terminal 1 in case of .

d, d2... are output waveforms of the output 34 of the S/H circuit. At this time, the reference signal 12 in FIG. 6 has a constant frequency of f, (e, 5f).

When the head scans the locus 2 in Figure 7, the crosstalk of the high lot signal h (7,5fH) on track B5 is higher than that of 82 (9,5fH) at the point where the rad starts contacting the tape. It is larger than . That is, the reproduction level of the difference frequency signal from the reference signal f1 (6, 6fH) is 'Iff.

If Vsfn, then Vf)I>Vsfy When the head is near the center of track entry 2, 'IfH: V5fl+ At the point where the head leaves the tape, vJH<v5fI (Therefore, when the still trajectory is 26, the tracking output to terminal 1 The error signal becomes a sawtooth wave as shown in FIG.
It will be around ef. .

When the head scans the locus 27 in Fig. 7, the tracking error signal of output 1 and the S/H circuit output 34 become as shown in C5, θ3, which is a waveform that has shifted downward in parallel with respect to Vref compared to cl and el. becomes.

Using the same idea, locus 2B in Figure 7 is C4, and 64 is Vre.
The waveform moves upward in parallel from the f potential, and the trajectory "I42"
At 9, VfH>Vsfn, resulting in a waveform of 05 and C5. Also track 5'$30
Then, the playback level of f, , 3flI is vfg < V3fH at the point where the head and tape begin to contact, and vf)Itvsf when the head is near the center of track A3.

At the point where the head leaves the tape, vfH>Vsfn, and the C1 waveform of the locus 26 and the C2 waveform of the locus 30 have waveforms that are symmetrical with respect to the Vref potential.

As explained in Fig. 9, Vre with resistors 38 and 39.40
By using two threshold voltages centered on the f potential and a comparator, el, C of the potentials 61 to e5 in FIG.
Noise-free field still playback can be realized by determining only 2, controlling the kissing drive so that the head trajectory follows the head trajectory shown in FIG. 7, 26.30, and intermittently transporting and stopping the magnetic tape.

Problems to be Solved by the Invention Figure 11 (A) shows the recording track, head trajectory, and reference signal (JRA
The timing relationship of f) is shown. fref during still playback
is fixed at f1, and when transitioning to normal playback, it starts from fl and f
1, f, are entered in the order shown in FIG. 6, 12. As mentioned above, when frer is fl, the pilot signal recorded on the main scanning track of the head is f+, frer
= h, the recorded pilot on the main scanning track is reproduced in the same manner as fl.

Figure 11) also shows the track, head trajectory, and reference signal (fre) when transitioning from still playback to normal playback.
This shows the timing of f), which is the pilot signal f recorded on the main scanning track during still playback, and when transitioning to normal playback, fref starts from fl and is output in the order of fl, f, and so on. After the transition to normal playback, the head moves to the track for one frame (two fields), causing a discrepancy between the two.

In view of the above problems, the present invention determines the frequency of the recording pilot signal on the main scanning track during still playback, and controls the generation phase of the reference signal frequency using the determined signal when transitioning from still playback to normal playback. The aim is to provide a tracking device.

Means for Solving the Problems In order to solve the above-mentioned problems, the tracking device of the present invention uses crosstalk signals of pilot signals recorded on recording tracks before and after the main scanning track and a reference signal during still playback. Tracking error detection means detects the tracking error obtained by multiplying the frequency of the pilot signal recorded on the main scanning track by sampling and holding the tracking error at the start or end of the main scanning track when the head scans the main scanning track. The apparatus is provided with a frequency discrimination means for obtaining a signal for discriminating the reference signal, and has a configuration in which the generation phase of the reference signal is advanced by 18Q0 by the discrimination signal when transitioning from still playback to normal playback.

Effect of the Invention With the above-described structure, the present invention uses the piezo 1 signal recorded on the still playback track to change the signal recorded on the still playback track, depending on the piezo 1 signal recorded on the still playback track. The frequency of the signal is determined, and the generation phase of reference signals f1 to f4 when transitioning from still playback to normal playback is set to 1 according to this signal.
By advancing the 8Q0 phase, noise-free reproduced images can be realized even after transition.

EXAMPLE Hereinafter, a tracking device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention, where 1 is a tracking error signal input corresponding to FIG. 6, 2 is an H3W pulse, and 3 is an S/H circuit.

5'ti "D path," C comparator, 9 is the reference voltage Vref of the comparator (=13Vref)
, 11 is a reference signal generation circuit, and still/normal signal 10. H8W pulse 2, 8 terminals (H, L
) can control the timing of generation of f, to f4 and output to terminal 12.

Figure 2 shows the waveforms of various parts during still playback in Figure 1, where & is the H8W pulse, b is the output S/H pulse of terminal 4, and CI+
dj is the terminal 1.6 waveform in FIG. 1 during still playback of a track in which fl is recorded on the main scanning track, and dl is the start of the edge of H8W.

In other words, it shows a sample-and-hold waveform of the tracking error signal at the portion where the head starts contacting the tape. Note that C1 corresponds to 01 in FIG.

At this time, since dl has a higher potential than vref 13, an H potential is output to terminal 8. C2+d2 is the waveform at terminal 1.6 in FIG. 1 when a track in which f5 is recorded on the main scanning track is being reproduced as a still image, and has an opposite relationship to 'j+dj. At this time, dl has a potential higher than Vr6f13. Since the voltage is low, an L potential is output to terminal 8. Note that C2+d2 corresponds to c2 and dl in FIG.

Figures 3 (a) and (b) show the output of terminal 8 and the reference signal (fre) when transitioning from still playback to normal playback.
f) shows the timing of occurrence.

Figure 3 (a) shows the main scanning track during still playback.
is recorded, output 8 is at H level,
After the still playback is canceled by this L level detection, the reference signal generation circuit sequentially starts from fl, f5, and so on. Signals are generated in the order of f4.

On the other hand, (b) shows f5 on the main scanning track during still playback.
is recorded, the output 8 is at the L level, and after the still playback is canceled due to the detection of this L level, the reference signal generation circuit advances by 1800 and sequentially from f5 to 14. Signals are generated in the order of f, , fl.

Figure 4 shows the waveforms of each part of Figure 1, similar to Figure 2.Since the tracking error signal is sampled and held at the end of the edge of the ASW pulse, that is, at the part where the head separates from the tape, d, 1, d. The potential of ,,1 is shown in Fig. 2d
,,The difference is that the polarity is opposite to d2 and 'Iref, but either the manual polarity at 7 in Figure 1 can be replaced, or the generation timing of the reference signal generation circuit can be changed to the level of output 8 as shown in Figure 2. It is clear that the same operation can be achieved by reversing the explanation.

Effects of the Invention As described above, according to the present invention, the tracking error signal detected during still playback is sampled and held at the start or end of the main scanning track scanned by the head, and the resulting voltage level is used to detect the tracking error signal during main scanning. The frequency of the pilot signal recorded on the track is determined, and the generated phase of the reference signal is advanced by 18Q0 when transitioning from still playback to normal playback based on this determination signal. can be realized.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram of a tracking device according to an embodiment of the present invention, Fig. 2 is a waveform diagram of each part thereof, Fig. 3 is a reference signal generation timing chart when transitioning from still to normal, and Fig. 4 is a waveform of each part thereof. Figure 6 is a recording magnetization locus diagram using a 4-frequency pyro, 71-signal method, Figure 6 is a block diagram of a tracking error signal reproducing circuit, and Figure 7 is a recording track and a Herad 7-inter scanning trajectory during methylation. figure,
FIG. 8 is a schematic diagram showing the positional relationship between the rotating drum and the head. Figure 9 is a block diagram showing an example of a circuit block that detects the recording track and head scanning position, Figure 10 is a waveform diagram of each part, and Figure 11 is the recording track, head trajectory, and reference signal when transitioning from methyl to normal playback. FIG. 2 is a schematic diagram showing the timing relationship of FIG. 3...Sample hold circuit, 6...
Monostable multivibrator, 7... Comparator, 9... Reference voltage source, 11... Reference signal generation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Nu d → Shi - Normal ↓ Nushi → Shiichi Normal ◆ Figure 4 d2 Pa Akebono - 1111 Farm - 1 ■ - Yoshiichi Yoichi - 1 - Me 1 Figure 5 / a Fig. 7 Fig. 8 30 River concave drum Fig. 10 es--- Fig. 10 Fig. 11 (streaking) Te+ f2 b

Claims (2)

[Claims] (1) A video signal of a predetermined unit length is recorded by a rotating magnetic head as a track having a predetermined angle with respect to the longitudinal direction of the magnetic tape. The reproduction crosstalk signal of the pilot signal recorded on the recording track before and after the main scanning track is multiplied by the signal from the pilot signal generator as a reference signal. A pilot signal is recorded on the main scanning track by a tracking error detection means for detecting the resulting tracking error of the head, and a voltage level obtained by sampling and holding the tracking error near the start of the head scanning the main scanning track. The generation phase of the reference signal is changed to 1 by the discrimination signal when transitioning from still playback to normal playback.
A tracking device characterized in that it is configured to advance in phase by 80 degrees. (2) The frequency determining means includes means for obtaining a signal for determining the frequency of the pilot signal recorded on the main scanning track based on the voltage level by sampling and holding the tracking error at the end of the track when the head scans the main scanning track. The first claim characterized in that it comprises
Tracking device as described in section.