JPH0452525B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a rotary head type magnetic recording and reproducing device that uses a position control element such as a bimorph plate to control the tracing position of a rotary head to enable noiseless variable speed reproduction. This invention relates to a head position control device for a VTR device.

[Background of the invention]

In a rotary head type magnetic recording and reproducing apparatus, it is essential to perform tracking control so that the rotary head correctly traces the inclined recording track on the magnetic tape during reproduction. Conventionally, such tracking control means have been used to accurately track the rotating head, especially in variable speed playback (slow, still, quick, etc.) modes in which the magnetic tape is played back by running at a speed different from that during recording. In order to make this possible, a rotating head is attached to a rotating drum via a position control element such as a bimorph plate, and during playback, this is displaced by supplying a control signal to electrodes attached to both sides of the bimorph plate. It has been proposed to control the rotary head to automatically trace correctly on an inclined recording track.

First, such a conventional technique will be explained using FIGS. 1 to 6.

FIG. 1 is a block diagram schematically showing a rotary head type magnetic recording and reproducing apparatus having the above-mentioned conventional tracking control means, in which 1 is a magnetic tape, 2 is a rotary drum, 3 and 4 are two rotary heads; The rotating heads 3, 4 are attached to the rotating drum 2 via movable parts of two bimorph plates 5, 6, respectively. 7 and 8 are amplifiers, and 9 is a demodulation circuit (including a head switching circuit). After that, it is demodulated and outputted from the output terminal 10 as a demodulated video signal. 11,12
1 is an automatic tracking circuit, and 13 is a tilt signal generating circuit. These circuits 11 to 13 control the positions of the bimorph plates 5 and 6 so that the rotary heads 3 and 4 correctly trace the tilt recording track on the magnetic tape 1. It constitutes a control circuit to That is, as shown in FIG.
4 to a scanning locus 21, and its inclination angle matches the inclination angle of the recording track 19. To this end, the inclination signal generating circuit 13 changes the scanning locus 20 of the rotary heads 3 and 4 into a scanning locus 21, and makes the inclination angle of the inclination coincide with the inclination angle of the recording track 19. During the scanning period, a slope signal whose level gradually increases is generated, and the bimorph plates 5 and 6 are driven to be displaced in accordance with the level of the slope signal. Such correction of the inclination angle of the scanning locus needs to be performed every alternate rotational scan of each rotary head 3, 4, and therefore the above-mentioned inclination signal is
It must be generated repeatedly in synchronization with the four alternating rotational scanning periods, and in order to enable the tilt angle correction of the scanning trajectory described above in any of the various variable speed playback modes. The inclination angle of the above-mentioned inclination signal must be different depending on the magnetic tape running speed (including stopping) for each variable speed playback mode. For this purpose, the tilt signal generating circuit 13 receives a signal from a head switching signal generator 15 (a signal indicating the alternate rotation scanning period of the rotary heads 3 and 4) and a rotation speed detector 16 that detects the rotation speed of the capstan 17. signals (signals indicating the running speed of the magnetic tape) are input, and the above-mentioned inclination signal is formed based on these signals.

On the other hand, the automatic tracking circuits 11 and 12 have the function of correcting and changing the scanning trajectory 21 which is deviated in the width direction of the recording track 19 to a scanning trajectory 23 without deviation, as shown in FIG. 2b. For this purpose, the automatic tracking circuits 11 and 12 detect the amplitude of the reproduced FM video signal from the rotary heads 3 and 4 inputted via the amplifiers 7 and 8, and move the bimorph plates 5 and 6 so that the amplitude is maximized. The displacement position is controlled.

By controlling the positions of the bimorph plates 5 and 6 as described above, the rotary heads 3 and 4 can trace the inclined recording track on the magnetic tape 1 at the correct inclination angle and without positional deviation. However, the rotary heads 3 and 4 do not necessarily trace a predetermined recording track sequentially, and in some cases,
A recording track traced by one rotary head may not become a predetermined recording track, but may shift to the previous or subsequent recording track, resulting in so-called track jumping. This is because the slope signal generation circuit 13 generates the slope signal using feedforward control, and the rotary heads 3 and 4 are switched for reproduction. When the vicinity of the recorded track before or after that is traced, the rotary head 3 moves to actively trace the recorded track due to the action of the automatic tracking circuit 12 described above, and remains stable in that state. This is because you end up doing it.

FIG. 3 is a diagram showing a scanning locus pattern by the rotary heads 3 and 4 when the above-mentioned track jump occurs, for example, during still playback. In the figure, if the recording track 19 is an azimuth recording track and the rotary heads 3 and 4 have the same azimuth angle to realize field still reproduction, then during still reproduction, the rotation Originally, the scanning trajectories by the heads 3 and 4 should both be the scanning trajectories 23 on the same recording track, but if a track jump occurs, for example, the scanning trajectories of one of the rotary heads 3 become 25. Or move like 26. In this case, the reason why the scanning locus of the rotary head 3 does not move onto the recording track adjacent to the scanning locus 23 is because the reproduction FM video signal output by the rotary head 3 cannot be obtained from these recording tracks due to the difference in recording azimuth. It is.

Now, as is clear from FIG. 3, when one of the rotary heads 3 moves to the traveling trajectory 25 or 26, these scanning trajectories 25, 2
6 moves downward or upward, respectively, along the longitudinal direction of the recording track, and as a result, discontinuities on the time axis occur in the reproduced video signals alternately output from the rotary heads 3 and 4. will occur. For example, in FIG. 3, when the rotating head 3 traces the scanning trajectory 25 following the tracing of the scanning trajectory 23 by the rotating head 4, the reproduction time interval of the vertical synchronizing signal indicated by the reference numeral 28 is as follows.
The time interval becomes longer than the normal time interval, and conversely becomes shorter when the rotary head 3 traces the scanning locus 26. Such discontinuities on the time axis appear as image blur on the playback screen, which is undesirable.
Therefore, in the conventional example shown in FIG. 1, a track jump correction circuit 14 is provided, and the track jump is corrected by the correction circuit 14. This track jump correction circuit 14 detects the occurrence of a track jump by using the change in the vertical synchronizing signal interval described above, and uses the detection output to detect, for example, one bimorph board 5.
The displacement position of the track jump is controlled to correct track jump, and its specific configuration is shown in FIG. In the figure, 32 is an up-down counter for detecting a change in the vertical synchronization signal interval when the track jump occurs, 31 is a reference clock that is a counting input of the counter, and VS is a demodulator 9 (second clock). Figure 1)
A vertical synchronizing signal is separated from the video signal demodulated by appropriate means (not shown). 3
3 is a determination circuit that determines the output of the counter 32 after up-counting and down-counting.
HSW is the head switching signal generator 15 (Fig. 1)
The determination timing of the determination circuit 33 is set by the signal from the determination circuit 33.

FIG. 5 is an operating waveform diagram of the track jump correction circuit shown in FIG. 4, where a is the HSW signal waveform of FIG. 4,
b is the vertical synchronizing signal VS during normal operation without track jumping, c and d are the vertical synchronizing signals VS when track jumping is occurring, and c
d is the result when one of the rotary heads 3 traces the scanning locus 25, as shown in FIG. 3, and d is the result when the rotary head 3 traces the scanning locus 26. e indicates the output of the up-down counter 32, 38 indicates the down count output corresponding to the vertical synchronizing signal VS during normal operation shown in b, and 39 and 40 indicate the output during track jump shown in c and d, respectively. This is a down count output corresponding to the vertical synchronization signal VS. As is clear from the waveform diagram of the down count output, if the final value of the down count is read by the determination circuit 33 based on the timing setting by the HSW signal shown in a,
The direction and amount of track jump can be detected, and the track jump can be corrected based on the detected output. The final values of the down-count outputs 39 and 40 are reset at the start of the next up-count, so that the final value count error is not accumulated.

Next, consider the case where the magnetic tape 1 is run at the same speed as during recording and the recorded video signal is reproduced in the standard speed reproduction mode in the rotary head type magnetic recording/reproducing apparatus shown in FIG. As mentioned above,
Since the rotating heads 3 and 4 have the same azimuth angle in order to realize field still playback, the scanning locus pattern on the magnetic tape 1 in the standard speed playback mode by these heads is as shown in Figure 6. . That is, the rotating heads 3, 4
As shown by scanning trajectories 42, 43, 44, 45, 46, . . . , only the recording tracks having a recording azimuth that matches the azimuth angle of both are sequentially updated and reproduced once at a time. I'm going to go to the middle of the day. In this case, the scanning locus of one of the rotary heads is originally the scanning locus 42', 42'.
3', 44', etc., for example, they are forcibly displaced one track pitch in the direction of the arrow shown in the figure to the adjacent track position. Therefore, one of the rotary heads is always in the track position in the standard speed playback mode. This means that you are making a jump. This track jump is a relatively small fixed amount of one track pitch, which is within the permissible range. However, if the track jump correction circuit 14 described above is activated due to such track jump, the correction operation will cause the track jump correction circuit 14 to operate. Large truck jumps occur all the time,
This caused a problem in that image blurring of the reproduced image occurred. Such a problem may occur not only in the standard speed playback mode, but also in, for example, the double speed playback mode, when predetermined recording tracks are sequentially updated and played back by displacing the position of one of the rotary heads. Also,
In addition to track updating, when the magnetic tape speed changes transiently, such as in frame-by-frame playback mode, the magnetic tape may be updated by changing the position of the rotary head for tracking on a predetermined recording track. There was a problem in that the vertical synchronization signal interval was disturbed and the track jump correction circuit malfunctioned, similar to the above.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
A head position control device for a rotary head type magnetic recording/reproducing device is provided which can detect only when an undesired track jump occurs in which the trace state of the rotary head deviates from a predetermined recording track and can correct the track jump. It is on offer.

[Summary of the invention]

In order to achieve this object, the present invention provides a rotary head type magnetic recording and reproducing apparatus having the conventional track jump correction circuit, wherein the track jump correction circuit is provided with an erroneous detection prevention means. The present invention is characterized in that the track jump correction circuit is configured so as not to detect changes in the vertical synchronization signal interval due to causes other than the undesired track jump.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 7 to 10.

FIG. 7 is a block diagram showing an outline of an embodiment of a track jump correction circuit according to the present invention, which corresponds to the track jump correction circuit in the conventional example shown in FIG. are given the same reference numerals. In the figure, reference numeral 47 is a reference clock correction circuit constituting means for preventing false detection, which is a feature of the present invention.
1, the track update signal 48 and the magnetic tape movement speed information signal 49 (for example, the first
The rotation speed detector 16 of the capstan shown in the figure
form a counting clock which is variably controlled by a signal from

32 is an up/down counter that counts the counting clock output from the reference clock correction circuit 47, and VS is an up/down counter of the counter 32.
A vertical synchronization signal for sequentially and alternately switching down counts; 33 is a determination circuit for determining the output of the counter 32 after up-counting and down-counting;
HSW is a signal from the head switching signal generator 15 (FIG. 1) that sets the determination timing of the determination circuit 33, and these signals are equivalent to the conventional example shown in FIG.

In this embodiment, as explained in the prior art example, even if the vertical synchronization signal interval changes due to track update or transient speed fluctuations of the magnetic tape, the change is caused by the track update signal 48 and the magnetic tape. Due to the variable control of the counting clock by the tape movement speed information signal 49, it does not appear in the final downcount value of the updown counter 32. First, the operation of this embodiment during the track update operation will be explained in more detail with reference to the operation waveform diagram of FIG. Now, assuming that the track update operation is in the standard speed playback mode shown in FIG. 6, the interval of the vertical synchronization signal VS in this case is
For the normal vertical synchronization signal interval shown in Figure b,
The fixed amount changes as shown in FIG. 8c or d in response to the displacement of one track pitch of one of the rotary heads described above.

Here, in FIG. 8c, one of the rotary heads is in the sixth position.
FIG. 8d shows the change in the vertical synchronizing signal interval when the vertical synchronizing signal is displaced by one track pitch in the direction of the arrow in the figure, and when the vertical synchronizing signal is displaced in the opposite direction.

In general, in double speed playback mode including standard speed playback mode (double speed ratio is 1 in standard speed playback mode), when the double speed ratio is an odd number, the same fixed amount of change in the interval of the vertical synchronization signal VS as above occurs, and the double speed When the ratio is an even number, no change occurs in the interval of the vertical synchronizing signal VS. The reason is that when the speed ratio is an odd number,
The track pitch of the sequential reproduction scanning trajectory by each rotary head is also an odd number, and one of the rotary heads always reproduces and scans on the recording track of the opposite azimuth.
It is necessary to displace the track pitch, but
When the speed ratio is an even number, the track pitch of the reproduction scanning trajectory by each rotary head is also an even number.
This is because the displacement of one of the rotary heads as described above is not necessary.

Now, such a vertical synchronizing signal VS is applied to the up/down counter 3 as in the conventional example shown in FIG.
The determination circuit 33 reads the final value of the down count of the counter 32 at the determination timing according to the head switching signal HSW shown in FIG. At this time, the reference clock correction circuit 47 controls the up-down counter 32 so that the final down-count value of the up-down counter 32 remains constant regardless of the state of change in the vertical synchronization signal interval. Variably controls the input counting clock. That is, when the vertical synchronizing signal VS has the normal interval shown in FIG. 8b, the reference clock correction circuit 47 supplies a predetermined counting clock to the up-down counter 32; When the interval changes by a fixed amount as shown in FIG. 8c or d, the up-down counter 32
During the down-count operation, the frequency of the counting clock is doubled or the supply of the counting clock is stopped for a predetermined period (a period corresponding to the fixed amount change in the vertical synchronizing signal interval). Figure 8e
38, 52, 5 indicate the counting output of the up-down counter 32 in each case.
3, the vertical synchronizing signal VS is Fig. 8 b, c,
This corresponds to the case where d. As is clear from the figure, the count output of the up-down counter 32 has the same final down-count value in any case, so the determination circuit 33 determines whether the vertical synchronization signal interval changes by a fixed amount, i.e. Does not detect changes in vertical synchronization signal interval based on track updates. However, if the vertical synchronization signal interval changes beyond the fixed amount due to a track jump or the like, there will be a difference in the final down count value of the up/down counter 32, and the determination circuit 33 will detect this as a track jump. It goes without saying that you should.

For variable control of the counting clock, the reference clock correction circuit 47 includes a ramp signal generation circuit 13.
A track update signal 48 is provided from.
The track update signal 48 determines which of the rotary heads 3, 4 will update the track first.
The reference clock correction circuit 47 includes the track update timing information shown in FIG. The counting clock is configured to determine the state of change in the vertical synchronizing signal interval, and to perform variable control of the counting clock in accordance with this. The track update signal is formed by counting the capstan FG, which is a moving speed information signal of the magnetic tape, during, for example, a high period of the head switching signal HSW (referred to as a reproduction period of the rotary head 3). In other words, during normal playback, this
Since it is determined how many capstan FGs are counted during the high period of HSW, it is possible to judge how many tracks need to be updated depending on the playback speed.
Furthermore, by comparing the numbers between the high and low periods of HSW during slow playback, it is possible to determine which of the rotating heads 3 and 4 updates the track first. Further, in order to set the variable control period to the above-mentioned predetermined period, the reference cross correction circuit 47 includes a fixed correction amount output circuit that generates a fixed correction amount output as shown in FIG. 8g.

A specific example of the configuration of such a reference clock correction circuit 47 is shown in FIG. In the figure, 56 is a determination circuit for determining the state of change in the vertical synchronization signal interval based on the track update signal 48, 57 is the fixed correction amount output circuit, and 58, 59, 60, and 61 are
62 is an inverter; 63 is a counting clock forming circuit that forms a counting clock based on the reference clock input 31; 64 and 65 are flip-flops;
The frequency is divided by 1/2 by 4, and then the flip-flop 6
The frequency is divided by 1/2 by 5. The discrimination circuit 56 receives the track update pulse for each rotating head included in the track update signal 48 as a clock input, and operates a counter that performs up/down switching according to the track update timing information [FIG. 8f]. Since the magnitude relationship of the number of track update pulses for each rotating head corresponds to the vertical synchronization signal interval shown in FIG. 8b, c, and d, the final downcount value of the counter can be read. This makes it possible to determine the state of change in the vertical synchronization signal.

Now, assuming that the vertical synchronization signal interval is in the state shown in FIG. 8b (normal interval), the output 56 of the discrimination circuit 56
b becomes logic 1, and output 56a becomes logic 0. In this state, the output of the fixed correction amount output circuit 57 [Fig. 8g] is at a low level (logic 0), and the inverter 62
If the output of the flip-flop is logic 1, the NAND gates 58 and 60 are closed and only the NAND gate 59 is open.
is supplied to the up/down counter 32 via the NAND gates 58 and 60 (which are open because both outputs are logic 1), and the output of the fixed correction output circuit 57 is at a high level (which is logic 1). ), then instead of the NAND circuit 59
Since only NAND gate 60 is open, the 1/4 frequency divided counting clock from flip-flop 65 is supplied to up-down counter 32 in this case as well.

Next, when the vertical synchronizing signal interval is in the state shown in FIG. 8c, the output 56a of the discrimination circuit 56 becomes logic 1, and the output 56b becomes logic 0. In this state,
During the period when the output of the fixed correction amount output circuit 57 is at a low level (logical 0), the NAND gates 59 and 60 are closed and only the NAAND gate 58 is open. is supplied to the up-down counter 32 via the fixed correction output circuit 57.
The period when the output of is high level (logic 1) is:
Since only NAND gate 60 is open, the 1/4 frequency division counting clock from flip-flop 65 is supplied to up-down counter 32. That is, during the period when the output of the fixed correction amount output circuit 57 is at a low level, the frequency of the counting clock supplied to the up-down counter 32 is twice as high as during the period when the output is at a high level.

When the vertical synchronization signal interval is in the state shown in FIG. ), all NAND games 58-60 will be closed,
The supply of the counting clock to the up-down counter 32 is stopped. When the output of the fixed correction amount output circuit 57 becomes high level (logic 1), only the NAND gate 60 opens, and as in the other cases, the 1/2 output from the flip-flop 65 is sent to the up-down counter 32.
A divide-by-4 counting clock is provided.

Reference clock correction circuit 4 of FIG. 9 explained above
7, it is clear that the count output of the up-down counter 32 can be made as shown in FIG. In some cases, it may not change. It goes without saying that the low level period of the output of the fixed correction amount output circuit 57 (FIG. 8g) should be set in accordance with the fixed amount change in the vertical synchronization signal interval, and therefore The low level period differs depending on the recording modes EP, LP, and SP of the magnetic recording/playback device.

Next, the magnetic tape moving speed information signal 49
The counting clock is variably controlled by the track jump correction circuit 1, and even if the vertical synchronizing signal interval is disturbed due to transient fluctuations in the running speed of the magnetic tape, this is corrected by the track jump correction circuit 1.
A specific example of a configuration and its operation for preventing false detection of 4 will be explained.

In this embodiment, the above-mentioned prevention of erroneous detection is achieved by the counting clock forming circuit 63 shown in FIG. That is, during a period of transient fluctuation in the running speed of the magnetic tape, for example from a stopped state to a predetermined running speed, or from a predetermined running speed to a stopped state, etc., the rotary head adjusts the transient state of the magnetic tape in order to obtain the best tracking state. This displacement follows the speed fluctuation of the magnetic tape, and this displacement causes a disturbance in the vertical synchronizing signal interval, but this disturbance (increase or decrease) in the vertical synchronizing signal interval is caused by the amount of displacement of the rotating head, that is, the amount of speed fluctuation of the magnetic tape. It is approximately proportional to
Therefore, if the frequency of the counting clock for counting the interval of the vertical synchronizing signal is variably controlled by the magnetic tape movement speed information signal 49 so as to be almost inversely proportional to the speed fluctuation, the counted value, i.e. The count value of the up-down counter 32 can be made independent of changes in the vertical synchronization signal interval due to transient speed fluctuations of the magnetic tape.

Here, the displacement direction necessary for the rotating head to obtain the best tracking state during the transient speed fluctuation period of the magnetic tape varies depending on the running direction of the magnetic tape, and therefore the change in the vertical synchronization signal interval also varies according to the normal Since the polarity is reversed with respect to the interval, the variable control of the counting clock also requires switching its polarity depending on the running direction of the magnetic tape. Therefore, the magnetic tape movement speed information signal 49 is
It contains not only speed fluctuation information of the magnetic tape, but also information about its running direction, so that the counting clock forming circuit 63 in FIG. 9 decreases the counting clock for the forward running of the magnetic tape. ,
Further, the magnetic tape is configured to be variably controlled in the increasing direction for running in the reverse direction.

FIG. 10 shows a specific configuration of the counting clock forming circuit 63, in which 66 is
A detection circuit for the magnetic tape movement speed information signal 49 outputs speed fluctuation information 77 to its first output terminal.
It also outputs running direction information 78 to its second output terminal. 67, 68, 69, and 70 are NAND gates, 71, 72 are inverters, and 75, 76 are flip-flops. Reference numeral 73 denotes a frequency-divided clock obtained by dividing the frequency of the reference clock 31 by 1/2 by an appropriate means (not shown), and the frequency-divided clock is inputted to the T terminal of the flip-flop 75 via the T terminal of the flip-flop 76 and the inverter 71. ing. 7
4 is a multiplication clock that doubles the frequency of the reference clock 31 by appropriate means (not shown);
It is input to one input terminal of the NAND gate 68. Note that the reference clock 31 is the NAND gate 6.
9 is input to one input terminal, and
The output of the NAND gate 70, ie, the output of the counting clock forming circuit 63, is input to the T terminal of the flip-flop 64 as shown in FIG.

Hereinafter, the operation of the counting clock forming circuit described above will be explained as follows.
This will be explained with reference to the operating waveform diagram in FIG. In FIG. 11, a is the reference clock 31, b is the frequency-divided clock 73 obtained by dividing this by 1/2, and c is the detection circuit 66.
The speed variation information 77 is input to the D terminal of the flip-flop 76, and resets the flip-flop 76 at its rising edge _c1 . On the other hand, the frequency dividing clock 73 is connected to the flip-flop 76.
Since it is input to the T terminal of and sets the flip-flop 76 at the rising edge _b1 after the above-mentioned reset,
The Q terminal output becomes logic 1, and the output is
The signal is input to one input terminal of the NAND gate 67 and is also input to the D terminal of the flip-flop 75, thereby resetting the flip-flop 75. Therefore, the terminal output of flip-flop 75 also becomes logic 1, and this output is input to the other input terminal of NAND gate 67. at this point
Since both inputs of the NAND gate 67 are both logic 1, its output is logic 0;
The signal is input to one input terminal of the NAND gate 69 and the gate 69 is closed.

On the other hand, the output of the NAND gate 67 becomes logic 1 via the inverter 72, and is also input to one input terminal of the NAND gate 68. Now, the running direction information 78 of the magnetic tape is shown in FIG. 11d. As shown, if it is in the low level state (forward direction running state), the above running direction information 78 is input as logic 0 to the other input terminal of the NAND gate 68, so the NANDD gate 68 is in the low level state (forward direction running state). It remains closed. Therefore, in this state, both NAND gates 68 and 69 are closed and no output is produced, so that the counting clock output from NAND gate 70 is also stopped. Next, when the divider clock 73 falls at edge _b2 , this falling sets the flip-flop 75 through the inverter 71, and its output becomes a logic zero. Therefore, at this point, NAND gate 6
The output of 7 is converted to logic 1 and the output of NAND gate 6
Open 9. Along with this, the
The input to NAND gate 68 is converted to a logic zero, but this does not cause any change;
NAND gate 68 remains closed.

When the NAND gate 69 is opened, the reference clock 31 input to the other terminal of the gate is outputted to its output terminal, and the reference clock 31 is connected to the NAND gate 70 (the NAND gate 70).
A zero is output as a counting clock through a logic one output from NAND gate 68 (opened by a logic one output from closed NAND gate 68). This state does not change depending on the subsequent rising and falling edges b ₃ , b _{4 .} . . of the dividing clock 73. The reason is that, as described above, once the flip-flops 76 and 75 are set to the set state by the rising and falling edges b ₁ and b ₂ of the frequency dividing clock 73, This is because it does not respond to the rising and falling edges b ₃ , b ₄ . However, when the flip-flop 76 is reset again by the rising edge _c2 of the magnetic tape speed fluctuation information 77, the above operation is repeated (the magnetic tape running direction information 78 is held at a low level). ). Thereafter, the above operation is repeated for each rising edge of the speed fluctuation information, and eventually the counting clock output from the NAND gate 70 is shown in FIG.
As shown, one pulse of the reference clock 31 is subtracted for each period of the speed fluctuation information 77. Therefore, when the magnetic tape is running in the forward direction, the average frequency of the counting clock is variably controlled so as to decrease in approximately inverse proportion to the variation in the running speed of the magnetic tape.

On the other hand, when the magnetic tape runs in the reverse direction, the 11th
Since the traveling direction information 78 in FIG.
During the period when the output of the NAND gate 67 is logic 0,
When the output from inverter 72 causes another input of NAND gate 68 to become a logic 1, NAND gate 68 is opened for this period and multiplier clock 74 having twice the frequency of reference clock 32 passes through gate 68. Then, it is outputted as a counting clock via a NAND gate 70. In other periods, as in the case of the forward running of the magnetic tape, the NAND gate 70 sends the data to the NAND gate 6.
The reference clock 31 from 9 is output as a counting clock. Therefore, when the magnetic tape runs in the reverse direction, the counting clock output corresponds to the number of pulses only once per period of the magnetic tape speed fluctuation information 77, as shown in FIG. 11e as 80. is increased to two, and its average frequency increases in almost inverse proportion to fluctuations in the running speed of the magnetic tape.

The counting clock thus formed is input to a flip-flop 64 (corresponding to flip-flop 64 in FIG. 9) and is used as a counting clock for the up-down counter 32.

〔Effect of the invention〕

As explained above, according to the present invention, a rotary head type magnetic recording device is provided with a track jump correction circuit that detects and corrects track jumps by utilizing changes in the vertical synchronization signal interval of a video signal reproduced from the rotary head. In the playback device, the track jump correction circuit compensates for changes in the vertical synchronizing signal interval due to causes other than track jumping, such as a fixed amount change in the vertical synchronizing signal interval during a track update operation of a rotating head, or a change in the running speed of the magnetic tape. It is possible to reliably prevent erroneous detection of changes in the vertical synchronization signal interval caused by transient fluctuations, and these erroneous detections can cause the track jump correction circuit to malfunction.
Since it is possible to prevent image blurring from constantly occurring in reproduced images, it is possible to provide a head position control device for a rotary head type magnetic recording and reproducing device that eliminates the drawbacks of the above-mentioned prior art and has excellent functions. can.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing a rotary head type magnetic recording and reproducing device having a conventional tracking control means, Fig. 2 is an explanatory diagram of its operation, and Fig. 3 is a scanning locus of the rotary head when track jump occurs. 4 is a block diagram showing the specific configuration of the track jump correction circuit 14 in FIG. 1, FIG. 5 is an operation waveform diagram thereof, and FIG. 6 is a scanning locus pattern diagram of the rotary head in standard speed playback mode. ,
FIG. 7 is a block diagram showing an embodiment of the track jump correction circuit according to the present invention, FIG. 8 is an operation waveform diagram thereof, and FIG. 9 is a block diagram showing a specific example of the configuration of the reference clock correction circuit 47 in FIG. Figure, 10th
This figure is a block diagram showing a specific example of the configuration of the counting clock forming circuit 63 in FIG. 9, and FIG. 11 is an operation waveform diagram thereof. 14...Track jump correction circuit, 31...Reference clock, 47...Reference clock correction circuit, 48
...Track update signal, 49...Magnetic tape movement speed information signal, 56...Discrimination circuit, 57...Fixed correction amount output circuit, 58-61, 67-70...
NAND gate, 62, 71, 72... Inverter, 63... Counting clock forming circuit, 64, 6
5, 75, 76...flipflop, 66...
Detection circuit, 73...dividing clock, 74... multiplying clock.

Claims (1)

[Scope of Claims] 1. N rotary heads provided on the movable parts of the N position control elements, and the position control so that the rotary heads sequentially trace predetermined inclined recording tracks on the magnetic tape. a control circuit for controlling an element; and a control circuit for reproducing the track jump from the rotary head when the trace state of the rotary head by the control circuit deviates from the predetermined inclined recording track and moves to a track before or after the track jump. In a rotating head type magnetic recording and reproducing apparatus having a track jump correction circuit that corrects the track jump by detecting a change in the interval of a vertical synchronizing signal of a video signal, the track jump correction circuit is provided with a false detection prevention means, A head position control device for a rotary head type magnetic recording and reproducing apparatus, characterized in that the track jump correction circuit is configured to prevent the track jump correction circuit from detecting a change in the vertical synchronizing signal interval due to a cause other than the track jump, using an erroneous detection prevention means. 2. The false detection prevention means is configured to prevent the detection of a change in the vertical synchronization signal interval based on a track update operation when the rotary head is normally tracing the inclined recording track. A head position control device for a rotating head type magnetic recording/reproducing device according to claim 1. 3. The rotation control device according to claim 2, wherein the false detection prevention means is configured to further prevent detection of changes in the vertical synchronization signal interval based on transient running speed fluctuations of the magnetic tape. A head position control device for a head type magnetic recording/playback device.