JPH01269267A - Automatic tracking device - Google Patents

Abstract

PURPOSE:To discriminate a tracking condition without fail by dividing the period of one tack into the three areas of front, medium and rear areas, sampling a reproducing output and executing tracking control based on three detecting values. CONSTITUTION:In order to obtain the optimum tracking condition in case of a double speed, a reproducing envelope output corresponding to one field is sampled with a prescribed time interval and the total sum of information in the three couples of the front, medium and rear areas is utilized. For example, 15 the reproducing envelope outputs during the H-level period of an RF switching pulse are sampled with a 1msec interval and sections S1, S2 and S3 are shown by adding values addressing to the five outputs. When a head traces a reverse azimuth track, the conditions of S1=S2, S2<S1 and S2<S3 are obtained. The escape of the condition is executed by the adjustment of delay quantity in a reproducing control signal or a reference signal and a delay time is made short. In case of S1>S3, the delay time is made long. In the optimum tracking condition, the condition of S1=S3, S2>=S1 or S2>=S3 is obtained. Thus, the judgement of the tracking condition can be correctly decided without fail and tracking automatic control can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an automatic tracking device in a video tape recorder (VTR) or the like.

--) Conventional technology Japanese Patent Application Laid-Open No. 61-4380 (HO4N 5/7E35
) shows a configuration in which automatic tracking is performed using the difference in playback output between a trace start portion and a trace end portion of an unused head during still playback in an intermittent slow playback mode.

(c) Problems to be Solved by the Invention In the above-mentioned prior art, since the tracking state is determined by sampling two parts of the reproduced output, there is a risk that the possibility of erroneous determination increases.

There is also a possibility that the state becomes stable where the track is being played completely in reverse.

Therefore, in the present invention, the period of one field (one track) is divided into three areas: front, middle, and rear, and the playback output is sampled, and based on these six detected values, tracking control.

Further, each area has a plurality of sampling points, and the detection level of each area is calculated using the levels at the plurality of sampling points for each area.

(E) Function As described above, according to the present invention, since the playback output levels in six areas of the playback output are compared, unlike the prior art, it is possible to trace completely on the paired tracks and stabilize. There is no need to worry about it getting lost. Furthermore, since a plurality of sampling points are provided in each area, the tracking state can be determined without error.

(f) Example Hereinafter, the present invention will be described in detail with reference to the drawings.

First, an example of the present invention applied to double speed playback will be described.

For double speed playback, is the tape speed the same as the rotation of the head?
The data is reproduced at twice the size of recording. In this double speed playback, depending on the state of tracking adjustment, playback outputs such as those shown in FIGS. 3, 4, and 5, for example, can be obtained.

As is well known, tracking adjustment is based on the delay amount of the playback control signal or the reference signal. This is done by changing. The tracking servo is controlled so that the rotational phase of the head and the tape running phase have a predetermined phase relationship.

In FIGS. 5-4, (a) shows the relationship between the recorded track and the trace of the magnetic head, (←) shows the reproduction envelope output, and (c) shows the RF switching pulse.

FIG. 5 shows a case where the delay time is long even though the amount of delay is appropriate. At this time, the playback envelope is small in the first half,
It gets bigger in the second half. FIG. 4 shows a case where the delay time is smaller than an appropriate value.

Contrary to the previous example, the playback envelope is large in the first half and small in the second half.

FIG. 5 shows the optimal tracking state at double speed. At this time, the playback envelope in the central part is dog-eared υ, and decreases in the first half and second half. Considering an actual playback screen, FIG. 5, where a good playback image is obtained at the center of the screen, is the optimal tracking state.

In order to detect this optimal state, in the present invention, the playback envelope output corresponding to the - field is
Divided into six parts, these six parts (St) (82)
(82) is compared. As a result, the areas of five parts will be compared.

For this reason, the playback envelope output equivalent to one field is sampled at predetermined time intervals, divided into five sets corresponding to the front, middle, and back, and the sum of the sampling data for each set is calculated. Make use of it. For example, as shown in FIG. 6, it is assumed that the value represents the H level of the RF switching pulse (and the reproduction envelope outputs S1 and S2.85 of the dL level 3rd stage M).

Next, the determination of the tracking state using this reproduction envelope output and the control of the delay time of the reproduction control signal or reference signal based on this determination will be explained. In the case of Figure 7 (a), is the magnetic head selected for reproduction tracing a track with the opposite azimuth?
It shows. In this case, 31=82 and 82<81
and 82<SS (hereinafter, the sum of sampling values in each area will be expressed as 81, S2, and SS).

To escape from this state, for example, you can shorten the delay time (it is also possible to lengthen it, but when configuring an actual device, when this state is detected, for example, by shortening the delay time, it is possible.) (It is preferable that you have already decided.)

The case of FIG. 7-) corresponds to FIG. At this time, Sl becomes Sl. In this state, the delay time can be shortened. ) corresponds to Fig. 4. At this time, if Sl>Bs, the delay time may be increased.

In the optimal tracking state, as in (c), 51=S
s, 82≧81 or S2≧Ss. Tsumashi, S1
, S2.5M are in these relationships, it can be determined that the tracking condition is good.

Next, a configuration of an embodiment using the above relationship will be described. FIG. 2 is a block diagram showing the main parts of a VTR employing the present invention. In the figure, (1) is a rotating cylinder, (2) is a first recording/reproducing (with a first azimuth angle)
R/P) head, (3) a second R/P head having a second azimuth angle, and (4) an auxiliary head having a first azimuth angle. This VTR is a 6-head type.

(5) Herad motor, (6) Helad servo circuit, (
7) is a capstan, (8) is a pinch roller, (9) is a capstan motor, and is a capstan servo circuit.
υ is an intermittent drive control circuit, (121 is a video tape, 03
1 is a control signal R/P head, α is a selection circuit for playback output from the head, IIS is an amplifier, αe is an envelope detection circuit, σB is a D/A converter, and α8 is a microcomputer that executes automatic tracking control. be.

The rotation of the head motor (5) is controlled by a helad servo circuit (6). In reality, the PG multiplied signal indicating the rotational phase (output of PG head αj)] and the reference (Ref, ) signal (
Control is performed so that the phase relationship between the oscillator output during reproduction and the vertical synchronization signal during recording becomes a predetermined one. Further, the head servo circuit (6) creates an RF switching pulse based on the PG multiplied signal.

The reproduction output selection circuit I is provided with two selection switches. The switch selects the reproduction output from the second R/P head (3) and the auxiliary head (4).

This switch J is controlled by an intermittent drive control circuit 1111. Further, the switch I211 is controlled by an RF switching pulse, and selects either the reproduction output of the first R/P head (2) or the output of the switch (2).

The capstan (7) is driven by a capstan motor (9). Usually, the rotating shaft of the capstan motor (9) is used as the capstan. The capstan servo circuit 02 receives the FG multiplied signal from the capstan motor (9) and controls the speed of the capstan motor based on this FG multiplied signal. Further, during reproduction, for tracking, the phase of the oscillator output (same as that supplied to the head servo circuit (61) and the reproduction control signal is compared, and the phase of the capstan motor is controlled).

Intermittent one-motion control times! ! 8u is a circuit that controls the capstan motor, switch (to), etc. during intermittent slow playback. In intermittent slow playback, still playback and normal playback are performed alternately. The timing of still playback is determined based on a playback control signal.

Further, the timing of starting normal reproduction is determined based on the RF switching pulse. Therefore, intermittent 1 drive control circuit 1
B is supplied with a reproduction control signal and an RFX switching pulse.

The intermittent drive control circuit (111) outputs a signal for controlling the rotation of the capstan motor (9) and a signal for controlling the switch.

The envelope detection circuit W&tte extracts the envelope of the reproduced high frequency signal. The D/A transformer αD changes the g-mark output of this detection circuit into a digital value (C
(may be provided within the PUa&).

A microcomputer (CPU) t181 plays a central role in auto-tracking operations. This microcomputer (1ε) performs the operations described above.

For this purpose, input the digital value of the D/A converter (17). Also, a mode control signal from the system control circuit @ (not shown) is supplied.

When the VTR is set for double speed playback, the capstan servo circuit 1.1Ql changes its operation in accordance with the mode control signal so as to transport the tape at twice the tape speed during recording. Then, the control signal of the switch ■ from the intermittent drive control circuit aυ becomes H level, and the auxiliary head (
4) playback output is selected.

Then, the CPU (181) performs processing corresponding to double speed playback.

Processing corresponding to double speed is as shown in FIG. C
The PUCl8) is normally in a mode determination standby state, and when double speed mode is instructed, it determines this and starts the process shown in FIG.

The playback envelope is then sampled when the RF switching pulse (RFSW) is at the L level, depending on whether the VTR is a 3-head type or a 4-head type, or whether it is in standard (SP) mode or long-term CEP mode. First, it is determined whether to sample at H level (12311241).

Actually, when in the SP mode of a double azimuth 4-head VTR, the L level period of the RFSW is sampled (251°; in other cases, the H level period is sampled). This is because the reproduction output from the narrow head is sampled. By using a narrow head, more accurate tracking adjustment can be achieved.

Sampling is basically the same as the explanation in FIG.

The rising (or falling) edge of RFSW (Fig. 9)) is detected, and the A
/D conversion output for a total of 15 digits/pulling. Since the playback output may be unstable near head switching, the first two are not used. And each of the 5 areas has 4
data is included (wrJ9 diagram)). Therefore, the last data is not used either.

The four data values are added for each factory,
The numerical values of Sl, S2, and Ss are determined. However, when the value of individual data is smaller than a predetermined value, it is ignored and regarded as y. This is because when there is an unrecorded part (girt band) between tracks (this may occur depending on the head width), the tracking adjustment operation is performed using the noise output when tracing this guard band part. This is to ensure that there is no such thing.

Once Sl, S2, and SS are determined, these are compared.

At this time, only a predetermined number of upper bits (for example, 3 to 4 bits) of the 8 bits of the sampled digital value are compared. this is.

This is because the reproduction envelope output fluctuates slightly, and comparing even the lower bits will only complicate the procedure and is meaningless.

First, check whether Sl and Bs are equal.

If they are not equal, the case shown in FIG. 7 (Iff) will occur. Therefore, to check whether f31 < 85, S
If l<SS, the delay time is set to a predetermined value f (2 steps, 0
．． 572m5) (unless 13°81<85, lengthen by a predetermined amount (2 steps) ω.

In the case of 51=Ss, it is the case of FIG. 7 (a) or e→. So I checked to see if 82<83. 82<f3s corresponds to FIG. 7(a), so the delay time is shortened by a predetermined amount (12 steps) □□□. In these six cases ■ In the case of 33341, the tracking adjustment must be continued, so the completion flag is set to / (To)
, as the period state of 150 m5 (9), returns to the original state.

Since 82<83 and S2=ρ does not correspond to FIG. 7(c), the completion flag is set to "1" (to) and the process enters the 1soms standby state C(7). F
32=fH check 3D is performed as described above.
When tracing the guard band part, use SL and S.
This is because there may be a case where all of 2 and S3 become /.

In procedure 33C34, data specifying a new delay time is actually supplied to the capstan servo circuit. Based on this supplied data, the capstan servo circuit [In changes the delay time.

After this change, it takes about 5 ohms for the servo to stabilize, so I put in a standby mode of 150 m5 to allow for some margin. This is because accurate determination cannot be made unless the envelope is checked in a stable state.

In (2), it is checked whether the completion flag is "1" twice in a row. If the value is "1" twice in a row, the mode determination standby state is entered and the tracking adjustment is completed. If it is not "1" twice in a row, tracking adjustment is continued.

The means for changing the delay time of the reproduction control signal according to data from the CPU (181) (in this embodiment, the means for delaying the reproduction control signal is provided in the servo circuit (101) as shown in FIG. This configuration can be considered as an example.Basically, when the counted value of the counter (381) and the data preset in the storage means (to) match, the output is output, and this preset data is changed. Change the time until output is obtained by changing the time until the output is obtained.The counter/brain starts counting by applying the reference signal (
This is done by setting the R-87 lip-flop 411 by inputting the input signal (or reproduction control signal) and opening the gate tG. Also, when output is obtained, this R-8
7. The tip and counter are reset to prepare for the next operation.

Various other configurations can be considered as this variable delay means. For example, a configuration centered on the operation of decrementing a presettable counter using a clock signal may also be considered.

Although not shown in FIG. 1, when double speed playback is determined, data corresponding to the standard delay time is first transferred from the CPU 1t81 to the capstan servo circuit +
101. Also, even if the playback envelope output is checked every 150m5 a predetermined number of times (for example, several seconds), if the completion flag does not become "1" twice in a row, the final delay time is maintained and adjusted. Finish the operation. This is because noise in the playback screen moves during tracking adjustment, and if this state continues for a long time, it will be unsightly.

Also, although I explained next to the 6-head VTR, the 4-head VTR
The same applies to TR (so-called double azimuth 4-head type).

As described above, tracking adjustment is automatically performed during double speed playback.

Next, the auto-tracking operation during intermittent slow playback will be explained. As mentioned earlier, still playback and normal playback are repeated alternately.

Then, the slow ratio is determined according to the ratio of both periods.

The tape speed during intermittent slowing is controlled as shown in FIG. The brake signal (e) for the capstan motor is created by delaying the regeneration control signal (e) (variable delay means for the regeneration control signal is provided in the intermittent drive control circuit).Three-head configuration In this case, the first R/P head (21) and the auxiliary head (21) are used during still playback.
4), but during normal playback, the first and second R/P heads +21
(31 is used.

10 to 12 correspond to different delay times of the reproduction control signal.

In the case of FIG. 10, the delay time (T1) is short, and in FIG. 11, the delay time (T5) is long. In both cases, there is a lot of noise on the screen during still playback, which is inappropriate.

FIG. 12 shows the case where the delay time is optimal.

In the case of intermittent slow play, the playback envelope during still playback must be controlled to be optimal. and,
Since the waveform at that time is considered to be substantially the same as that during double speed reproduction, basically the same operation as in FIG. 1 should be performed.

FIG. 15 is a flowchart showing operations for envelope determination and delay time setting. Sampling of the envelope and the like are the same as in FIG. 1, so they are omitted. Envelope determination is performed at a timing after intermittent driving. Tsumashi, when entering intermittent slow playback from normal playback, first stop it appropriately, then perform the first start @,
Braking is performed according to the initial value of the delay time, and the playback envelope is checked when it is stabilized. The envelope check is thus performed after start-up and braking. Specifically, the RFSW pulses are counted from the timing at which the tape is started, the timing at which stable still playback will be obtained is obtained, and the envelope is checked. Whether sampling is to be performed at the H level or L level of the RFSW is determined by selecting the period traced by the narrow head, as in double speed playback.

First, check whether Ss>81. S5>81
If so, check whether Sl>S2 (g) C procedure (4BFa*muυ will be explained later. These are ignored in slow mode). If sl>82, the case shown in FIG. 14(c) occurs. So there are 17 steps (
t9ms) to shorten the delay time (actually, data is output to the intermittent drive control circuit). If 1.82>83, then the case shown in Fig. 14 (a) is correct, and 4 steps (11 m3
) minutes shorter decoy.

If S2≧3s, it is the case of Fig. 14-), so 1
Shorten the delay time by 1 step (3, 1 m5) Step H (49 After &J, set the completion flag to "/" and proceed to the next process.

83>81, and 51=S! If not S, 511°8
Determine whether 5>82 □□□. S s >8
2, see Figure 14), 17 step C
4.9m5) lengthening flash. If 85>82, S2
If S2>Sl, the 14th
In the case of Figure (e), the delay time is increased by 11 steps (51 ms). If S2≧s1, then Fig. 14 (
In the case of (to), lengthen (transform) by 4 steps (tlms).

After these steps (to) i'5f3 (57), the completion flag is set to "2" and the process proceeds to the primary process.

31=Ss, if Sl>Sl, it is open; if S2←I, it is open, and in the case of FIG. 14 (g), it is the optimal state. In this case, set the completion flag to "1" and
Cloudy, proceed to next process.

Before checking the envelope, the completion flag is checked in the same way as in FIG. 1, and if it is "1" twice in a row, it enters a standby state. If not, check again and change the delay time.

During still playback, after normal playback, the intermittent slow playback mode is entered for a predetermined period of time, and then the tape is completely stopped. In other words, still playback is when the still state of intermittent slow playback continues and it is not started again. Therefore, at the last still of intermittent throw, step (g) mf
51i61), the delay time should not be changed.

The reason why the waveform of the playback envelope is narrower than in the case of double-speed playback is to achieve the optimum state for dragging more quickly.

(Tsuma), do not start the tape during intermittent slowing,
This is because the envelope is not checked, so when the slow ratio is large, it may take a long time to reach the optimum state.

The setting for the amount of change in the delay time of the playback control signal is 2.
Values are determined through experiments for both double-speed playback and intermittent slow playback. The key point at this time is to not make the amount of change too large and to avoid jumping beyond the optimal state of tracking.

Although not shown in the figure, if the adjustment operation is continued without being completed, the screen becomes very unsightly, so the envelope check operation is performed a predetermined number of times (for example, 20 to 60 times).
If the adjustment operation is not completed even after adjustment is completed, the adjustment operation is finished,
What is the delay time? I try to keep it.

In the above embodiment, in order to check the levels of five areas, four pieces of sampling data at approximately equal intervals are added. Various modifications can be considered regarding this. In general, it is preferable to have a large number of samplings, and it is considered better to have equal intervals. Furthermore, since a plurality of pieces of data are added and compared, the number of areas needs to be the same.

Furthermore, it can be easily applied to a 4-head VTR (double azimuth 4-head).

(G) Effects of the Invention As described above, according to the present invention, since the playback envelope is divided into six areas and compared with each other to determine the tracking state, it is possible to determine the tracking state without error. The effect is great because it can be done.

[Brief explanation of the drawing]

FIG. 1 is a 70-chart showing the operation of the first embodiment;
The figure is a block diagram showing the configuration; FIG. 5, FIG. 4, and FIG. 5 are explanatory diagrams of double-speed playback; FIG. 6 is an explanatory diagram of sampling; FIG. FIG. 8 is a block diagram of the variable delay means, FIG. 9 is an explanatory diagram showing a concrete example of Vi tengling, FIGS. 10, 11, and 12 are explanatory diagrams of intermittent slowing, and FIG. FIG. 14 is an explanatory diagram showing the reproduction envelope. (Sl), (82) (82)...6 divided areas, (ll19...envelope detection, (18...
・Microcomputer applicant Sanyo Electric Co., Ltd. − Representative patent attorney Takuji Nishino (1 other person) ■ 0 /
-1ν 1 piece Figure 7 Rope output to playback engine Figure 8 ≠ 17 vk? ``1 Figure 9 S+ 92 5s I for moxibustion・lt' 124242324241 Chi 7゛Return 1 1 Na 7 Kakuretsu] (Chi 7'
i +; j = 1 Figure 11 ← Tape deficiency is a powerful phrase Figure 12 - Tape fixed direction direction Figure 14

Claims (1)

[Claims] (1) Divide and sample the playback output of one track recorded on the magnetic tape into three areas: front, middle, and rear, and perform tracking control by comparing detected values corresponding to these three areas. Automatic tracking device.