JPH07114483B2 - Magnetic image playback device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic image reproducing apparatus for performing slow reproduction without noise.

[Conventional technology]

Conventionally, a device shown in FIG. 6 is known as a magnetic image reproducing device for performing slow reproduction. FIG. 6 is a schematic configuration diagram showing a conventional magnetic image reproducing apparatus, which is a block diagram showing a main configuration part of the magnetic image reproducing apparatus and a signal track in which an image signal of a magnetic tape and a running control signal are recorded. , FIG. 7 is a timing diagram.

In FIG. 6, the magnetic image reproducing apparatus 10 is a magnetic tape 1.
Head drum 11 rotatably installed at the traveling position of
Is included. The head drum 11 is provided with magnetic heads 12 to 15 for recording or reproducing a video signal at an angle on its circumference (in the illustrated case, the magnetic heads 12 and 15 are
And the magnetic heads 13 and 14 are provided at positions separated by 180 °.

Magnetic heads 12 and 14 have the same azimuth angle and magnetic head 13
And azimuth angles of 15 are different. Magnetic head 13
And 15 have the same azimuth angle, which is different from the azimuth angles of the magnetic heads 12 and 14.

The magnetic tape 1 wound around the supply reel 16 and the take-up reel 17 is wound around the head drum 11 in an oblique direction. A drum motor 23 that rotates the head drum 11 is coupled to the head drum 11.

A capstan 20 and a pinch roller 21 are provided in the vicinity of the take-up reel 17 with the magnetic tape 1 interposed therebetween, and the capstan 20 is rotated to drive the magnetic tape 1.
A capstan motor 22 for driving the vehicle is connected.

Further, between the capstan 20 and the head drum 11, a running control signal (hereinafter abbreviated as CTL signal c) which is a reference signal for controlling the running of the magnetic tape 1 is recorded or played back. A playback head 18 is provided.

By the way, when the magnetic image reproducing device 10 is of the VHS system,
Regarding the relationship between the lengthwise direction of the magnetic tape 1 and the head drum 11, the right side portion is lowered and the left side portion is raised. Therefore, the magnetic pattern of the video signal recorded on the magnetic tape 1 is as shown in the upper part of FIG.

In the VHS system, the A track 2 is recorded at 6 degrees and the B track 3 is recorded at -6 degrees, and the CTL signal c is recorded.
Is recorded on the CTL track 4, and the distance X on the magnetic tape 1 between this CTL signal c and the upper end of the center line of the B track 3 is called the X value, and this X value is defined as 79,244 mm. .

The arrow X in the upper magnetic tape 1 in FIG. 6 indicates the running direction of the magnetic tape 1, and the arrow Y also indicates the magnetic head.
12 to 15 scanning directions are shown.

The video signal reproduced by the magnetic heads 12 to 15 passes through a rotary transformer 30 composed of a winding on the head drum 11 side and a winding fixed to the device, and is amplified by video signal amplifiers 31 to 34, respectively. After that, the outputs of the video signal amplifiers 31 and 32 are led to the head switch 35, and the outputs of the video signal amplifiers 33 and 34 are led to the head switch 36.

On the other hand, the head switching devices 35 and 36 are provided with the head switching signal generating element 24 directly connected to the drum motor 23 and the head switching signal detection heads 25 and 26 installed at a certain angle (180 ° in the figure). The head switching signal a generated and amplified and waveform-shaped by the head switching signal generating circuit 27 is input to the magnetic heads 12 to 15 sliding on the tracks 2 and 3 of the magnetic tape 1. The reproduction signal is selected and output.

As shown in FIG. 7A, the head switching signal a is "ON" to select the reproduction signal of the magnetic heads 12 and 13 and "OFF" to select the reproduction signal of the magnetic heads 14 and 15. Is generated as.

The video signal comparator 37 compares the levels of the reproduced video signals f and g input from the head switching devices 35 and 36, and "ON" when the level of the reproduced video signal f is higher than the level of the reproduced video signal g, In the opposite case, the "off" video signal comparison signal h is generated.

In the video signal selection circuit 39, the video signal selection signal i is “on”.
The reproduction video signal g is selected by, and the reproduction video signal f is selected when the video signal selection signal i is “OFF”.

Therefore, during normal reproduction, the video signal selection signal generation circuit 38
Always turns on or off the video signal selection signal i, so that only the reproduced video signal f or only the reproduced video signal g is selected.

FIG. 9A shows a track on which the video signal of the magnetic tape and the CTL signal c are recorded during still image reproduction.
FIG. 6B shows the head switching signal a. This FIG. 9 (b)
As shown in FIG. 9, the video signal selection signal generation circuit 38 outputs a signal of "in phase" or "opposite phase" of the head switching signal a as the video signal selection signal i, so that FIG. 9 (c) and FIG. The reproduced video signals f and g respectively shown in (d) are alternately selected in synchronization with the head switching signal a.

When the video signal selection signal i shown in FIG. 9 (e) is in phase with the head switching signal a (FIG. 9 (b)) (FIG. 9 (e)), recording with the same azimuth as the magnetic heads 12 and 14 is performed. Only the track is reproduced (Fig. 9 (f)).

When the video signal selection signal i is in the opposite phase to the head switching signal a as shown in FIG. 9 (g), only the recording track of the same azimuth as the magnetic heads 13 and 15 is reproduced (FIG. 9 (h)). ).

FIG. 10 (a) shows the track on which the video signal and CTL signal c of the magnetic tape at the time of high speed reproduction are recorded, and FIG. 10 (b) shows the head switching signal a. As shown in FIG. 10A, when the magnetic heads 12 to 15 slide over two or more recording tracks, the video signal selection signal generation circuit 35 causes the video signal comparison signal h (see FIG. 10). By outputting the signal of the opposite phase of (e)) as the video signal selection signal i (Fig. 10 (f)), the video signals f (Fig. 10 (c)) and g (Fig. 10 (c)) are output.
The larger level in Fig. 10 (d) is selected.

Further, the reproduced video signal j (FIG. 10 (g)) output from the video signal selection circuit 39 is subjected to signal processing such as amplification, detection, frequency conversion, etc. in the reproduction signal processing circuit 45, and the pseudo vertical sync signal addition circuit. After passing through 46, the reproduced video signal 47 is output.

Further, the head switching signal a shown in FIG. 7 (a) becomes a pseudo vertical synchronization signal b (FIG. 7 (b)) in the pseudo vertical synchronization signal generation circuit 40, and this pseudo vertical synchronization signal b reproduces a still image or the like. At times, when the vertical synchronizing signal is not normally reproduced due to noise, it is output to the pseudo vertical synchronizing signal adding circuit 46 and added to the reproduced video signal 47.

In the VHS system, since the vertical synchronizing signal is at a position 6.5 times as much as the horizontal scanning synchronizing after the head switching, the delay time from the rising and falling of the head switching signal a to the pseudo vertical synchronizing signal b is The same is set.

On the other hand, the head switching signal a and the CTL signal c reproduced by the recording / reproducing head 18 are input to the capstan control circuit 28, and a voltage signal proportional to the phase difference is output to the capstan motor drive circuit 29.

The capstan motor drive circuit 29 controls the rotation speed of the capstan motor 22 according to the input voltage. Therefore, during normal reproduction, the head switching signal a and the CTL signal c
The magnetic heads 12 to 15 slide on the track of the magnetic tape 1 on which the video signal is recorded.

The reproduction of the still image is realized by stopping the running of the magnetic tape 1.

On the other hand, 50 is a slow reproduction command switch, and the slow reproduction command generated by operating the slow reproduction command switch 50 is a tape running control circuit 51, a video signal selection signal generation circuit 38, and a pseudo vertical synchronization signal generation circuit 40. It is designed to be sent to.

The tape running control circuit 51 and the delay circuit 53 constitute magnetic tape stop position control means 70, and the delay circuit 53 is a CT.
The L signal c is delayed for a predetermined time and output to the tape running control circuit 51. This tape running control circuit 51
Is output to the capstan motor drive circuit 29.

The head switching signal a from the head switching signal generating circuit 27 is also input to the pseudo vertical synchronizing signal generating circuit 40.

As for the head switching signal a, as described above, the pseudo vertical synchronizing signal generating circuit 40 outputs the pseudo vertical synchronizing signal b to the video missing position calculating circuit 42.

This video missing position calculation circuit 42 is a video signal level detection circuit.
An image missing position detecting means 60 is configured with 41 and the tape running control correction circuit 44.

The video signal level detection circuit 41 includes the above video signal selection circuit.
The selected reproduction video signal j from 39 is input, and when the level of the reproduction video signal j becomes a predetermined level or less, the video signal level detection circuit 41 outputs the video omission signal k to the video omission position. It is output to the arithmetic circuit 42.

The video loss position calculation circuit 42 outputs a video loss position signal 1 representing the time difference between the pseudo vertical synchronization signal b and the video loss signal k to the tape running control correction circuit 44.

The tape running control correction circuit 44 detects that the video missing position signal 1 is zero,
That is, the delay time t of the delay circuit 53 is controlled so that the time difference between the video missing signal k and the pseudo vertical synchronizing signal b becomes zero.

A head switching signal counting circuit 52 counts the head switching signal a from the head switching signal generating circuit 27 and outputs it to the tape running control circuit 51 and the delay circuit 53.

During high speed reproduction, a high speed reproduction command switch 54 sends a high speed reproduction command to the capstan motor control circuit 28 and the video signal selection signal generation circuit 38.

Next, the slow reproduction operation in this conventional magnetic image reproducing apparatus will be described. Slow reproduction is realized by alternately performing still reproduction and normal reproduction.

First, when playing back a still image,
The relationship with the stop position of the magnetic tape will be described with reference to FIGS. 7 and 8. When reproducing a still image, only a set of magnetic heads of the same azimuth (in the case of FIG. 6, magnetic heads 12 and 14 or 13 and 15) is used. It is assumed that still images are reproduced by the magnetic heads 12 and 14 having the same azimuth angle as the track A in FIG. 8 (A).

Now, when the relationship between the track on the magnetic tape 1 and the magnetic head locus 5 is as shown in FIG. 8 (A) at the position where the magnetic tape 1 stops running, the A track and the magnetic head 12, Since the 14 azimuths match, the reproduced track is in the narrow range of the shaded area shown in the figure, and a part of the reproduced video signal j is missing as shown in FIG. 7 (f). As a result, in the reproduced screen, the missing portion becomes band-shaped noise, and the image is not reproduced normally.

On the other hand, when the relationship between the track on the magnetic tape 1 and the magnetic head locus 5 is as shown in FIG. 8 (B) at the position where the magnetic tape 1 stops running, the A track and the magnetic head 12, Since the 14 azimuths match, the track to be played back becomes the wide hatched area in the figure, and the playback video signal j
The video missing signal k and the video missing signal k are as shown in FIG. 7 (k) (reproduced video signal j ') and FIG. 7 (l) (video missing signal k'), respectively, and band noise does not appear on the screen.

Next, the operation during slow playback will be described. When the slow reproduction command switch 50 is pressed, the magnetic tape 1 is repeatedly stopped and run to perform the slow operation. While reproducing the still image at the position where the tape running is stopped, the head switching signal counting circuit 52 counts a predetermined number of head switching signals a and outputs the signal e.
To the tape running control circuit 51 and the delay circuit 53.

In response to this signal e, the tape running control circuit 51 turns on the capstan drive signal d (FIG. 7 (e)), and the capstan motor drive circuit 29 drives the capstan motor 22. At the same time, the delay circuit 53 is activated by the signal e, and the CT
The tape running control circuit 51, which receives the signal c ₁ (FIG. 7 (d)) after delaying the L signal c for a fixed time t ₁ (FIG. 7 (e)), outputs it. d (Fig. 7 (e)) is turned off, and the capstan motor drive circuit 29
Stops the capstan motor 22.

Next, the reproduced video signal j (Fig. 7 (f)) after the capstan motor 22 is stopped is input to the video signal level detection circuit 41, and the video missing signal k (Fig. 7) is input during a period below a predetermined level. (G)) is output.

This video loss signal k is input to the video loss position calculation circuit 42 together with the pseudo vertical synchronizing signal b (FIG. 7 (b)),
The video loss position calculation circuit 42 calculates the time difference between the video loss signal k and the pseudo vertical synchronization signal b which is first input after the input of this signal k, and the video loss position signal l ( FIG. 7 (h)) shows a tape running control correction circuit.
Output to 44.

The tape running control correction circuit 44 controls the delay circuit 53 according to the input image drop position signal l.

This control increases the delay time t ₁ of the delay circuit 53 by the time t ₂ (FIG. 7 (h)) represented by the video loss position signal l,
This is done by setting time t ₃ (FIG. 7 (i)).

However, the time t ₃ when it becomes equal to or greater than the period of the CTL signal c is the period is reduced.

Next, when the head switching signal counting circuit 52 counts a predetermined number,
The signal e is output, the tape running control circuit 51 turns on the capstan drive signal d, and the capstan motor drive circuit
29 drives the capstan motor 22.

At the same time, the delay circuit 53 is activated by the signal e, delays the CTL signal c by the time t ₃ = t ₁ + t ₂ , and then the signal c
₁ (signal c ₁ ′ shown in FIG. 7 (i)) is output, and this signal c
_The tape running control circuit 51 receiving " ₁ " turns off the capstan drive signal d (signal d'shown in FIG. 7 (j)), and the capstan motor drive circuit 29 stops the capstan motor 22.

At this time, the delay time is as shown in c ₁ ′ of FIG. 7 (i).
Since it is t ₃ , the start time of the stop operation of the capstan 20 is delayed by t ₂ compared to the time of the first still image playback operation, so it is possible to change from the start operation of the capstan 20 to the stop operation. Since the running distance of the magnetic tape 1 is almost constant up to this point, the positional relationship between the head locus 5 when the magnetic tape 1 is stopped and the tracks 2 and 3 on which the video signal is recorded is driving. The magnetic tape 1 moves forward, that is, to the left in FIG. 8 (A), by the distance that the magnetic tape 1 advances during the time t ₂ as compared with the first reproduction of a still image.

Therefore, the position of the video loss signal k (FIG. 7 (g)) is also
Since it shifts in the same direction by the distance corresponding to the time t ₂ , the stop position of the magnetic tape 1 approaches the position where the video missing position signal 1 becomes almost zero.

FIGS. 7 (k) to 7 (m) show the reproduced video signal j and the video missing signal k in the states of FIGS. 7 (g) to 7 (i).
Also, a reproduced video signal j ', a video missing signal k', and a video missing position signal l'corresponding to the video missing position signal 1 are shown.

[Problems to be solved by the invention]

In the conventional magnetic image reproducing device as described above, the image signal j
Is detected, and the slow playback stop timing is corrected so that it matches the vertical sync signal b.
The above correction is also performed on the missing portion of the video signal due to scratches on the magnetic tape, and there is a drawback that the stop position of the magnetic tape 1 deviates from the proper position.

Further, since the video signal level detection circuit 41 compares the reproduced video signal j with a constant value, it is necessary to determine the comparison value. However, when the comparison value is set low, the width of the video missing signal k is Since the noise width is narrower than the upper noise width, it is difficult to correct near the appropriate stop position, such as noise remaining at the bottom of the screen even when the video missing position signal 1 becomes almost zero.

Further, when the comparison value of the video signal level detection circuit 41 is set high, the width of the video missing signal k may become too wide. Therefore, before the video missing position signal 1 becomes zero, the video missing signal k becomes vertical. It is output after the sync signal b and does not become zero even when the video missing position signal 1 does not generate noise on the screen.

In addition, since the recording track width of each magnetic tape is different, or the amplification factor of the video signal amplifiers 31 to 34 varies with temperature, the level of the video signal varies greatly.
There is a problem that it is difficult to make the comparison value of the video signal level detection circuit 41 proper.

The present invention has been made to solve the above problems, and without using a means for detecting a missing position of a video signal,
An object of the present invention is to obtain a magnetic image reproducing device capable of correcting the stop position during slow reproduction to an appropriate position.

[Means for solving problems]

The magnetic image reproducing device according to the present invention detects the time difference between the comparison signal and the head switching signal by using the image signal comparison signal output from the image signal comparator used during the high speed reproduction during the slow reproduction. A track position detecting means for detecting a phase difference between the recording track and the reproducing head locus based on the time difference and outputting a signal representing the phase difference, and a magnetic tape running control means for making the phase difference approach zero. And a tape running control correcting means for controlling.

[Work]

In the present invention, the track position detecting means detects the phase difference between the track being reproduced and the reproducing head locus from the temporal relationship between the video signal comparison signal and the head switching signal during slow reproduction, and the track showing this phase difference. A position signal is output and the tape running control correction means controls the start operation of the capstan drive circuit to delay or advance the phase difference represented by the track position signal so that the phase difference approaches zero and the recording is performed. The track and playback head trajectory are automatically adjusted so that they have the proper positional relationship, and noise-free slow playback is performed.

〔Example〕

An embodiment of a magnetic image reproducing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of one embodiment thereof, and FIG. 2 is a time chart for explaining the operation of the present invention.

In FIG. 1, reference numerals 1 to 4, 10 to 18, 20 to 40, 44 to 4
The parts indicated by 7, 50 to 54, 70 are the same as in FIG.

In FIG. 1, the image missing position detecting means in FIG.
Instead of 60, track position detecting means 80 is used. The track position detecting means 80 is composed of a track position calculation circuit 43 and a tape running control correction circuit 44.

The track position calculation circuit 43 inputs the video signal comparison signal h from the video signal comparator 37, the head switching signal a, and the output of the tape running control circuit 51. The head switching signal a is compared and a track position signal m (a signal m in FIG. 2 (j)) representing the time difference between the two is output to the tape running control correction circuit 44. Other configurations are 6th
It is similar to the figure.

Next, the operation of this embodiment will be described. The outlines of the normal reproduction operation and the slow reproduction operation are the same as those of the conventional apparatus described above, and a method of correcting the magnetic tape stop timing during the slow reproduction will be described in detail below.

A video signal comparison signal h (FIG. 2 (i)), a head switching signal a (FIG. 2 (a)), and a capstan drive signal d (FIG. 2 (d)) are input to the track position calculation circuit 43. Has been done.

After stopping the capstan 20, the track position calculation circuit 43
From the temporal relationship between the video signal comparison signal h and the head switching signal a, the phase difference between the magnetic head locus 5 (see FIG. 5 (a)) and the recording tracks 2 and 3 (FIG. 1) is calculated. Track position signal m representing the phase difference (m in FIG. 2 (j))
Is shown) is output to the tape running control correction circuit 44.

FIG. 3 shows the state in this case, in which the signal wave of each part is formed corresponding to the track pattern on the magnetic tape during the still image reproduction of FIG.
3 (c) and 3 (d) respectively show the head switching device 3
The reproduced video signals f and g output from 5,36 are shown.

Now, the calculation in the track position calculation circuit 43 of FIG. 1 is time t from the rising of the video signal comparison signal h (FIG. 3 (e)) to the falling of the head switching signal a (FIG. 3 (b)). The time from the fall of _H and the video signal comparison signal h to the rise of the head switching signal a is added and averaged.

Time obtained by this calculation t ₂ = 1/2 × (t _H + t _L )
Indicates the deviation between the center of the period in which the video signal comparison signal h is “on” and the center of the period in which the head switching signal a is “off”.

Next, the tape running control correction circuit 44 controls the delay circuit 53 by the track position signal m input from the track position calculation circuit 43. When the value t ₂ obtained by the above calculation is larger than the half cycle t a of the head switching signal _a (FIG. 3 (b)), the tape running control correction circuit 44 corrects the delay time t ₁ of the delay circuit 53. The amount t ₄ (c ₁ ′ in FIG. 2 (k)) is a value obtained by subtracting the period 2 × t _a of the head switching signal a from t ₂ (t ₄ = t ₂ −2
× t _a ).

This is a negative value, and the delay time t ₁ of the delay circuit 53 is (2 × t _a −
It is decreased by t ₂ ) to become t ₃ (d 'in FIG. 2 (l)).

Since the period of the video signal comparison signal h is also (2 × t _a ),
(2 × t _a −t ₂ ) is the difference between the center of the video signal comparison signal h and the center of the head switching signal a by t ₂ (FIG. 2 (j)), which is (2 × t _a −t 2). ₂ ) = t ₂ ′.

However, if t ₃ (Fig. 2 (l)) becomes negative,
The cycle of the CTL signal c is added.

Contrary to the above case, t ₂ is the half cycle t _a of the head switching signal _a.
The smaller case is shown in FIG. 4, FIG.
Shows the track pattern on the magnetic tape and the scanning locus of the magnetic head during still image reproduction. FIG. 4 (b) shows the head switching signal a, and FIG. 4 (c) and FIG. Signals f and g, and FIG. 4 (e) show the video signal comparison signal h.

In this case, the amount t ₄ when the tape running control correction circuit 44 corrects the delay time t ₁ of the delay circuit 53 is equal to t _2, t ₁ is increased by t _2, t ₃ (d of FIG. 2 (l) ′) However, t ₃ is
When it becomes larger than the cycle of the CTL signal c, the cycle is reduced.

When the next capstan motor 22 is driven, the delay circuit 53
A signal c ₁ (c ₁ ′ in FIG. 2 (k)) obtained by delaying the signal c by (t ₃ = t ₁ + t ₄ ) is output, and the tape running control circuit 51 sings this signal c ₁ and the capstan drive signal. “D” (d ′ in FIG. 2 (l)) is turned off, and the capstan motor drive circuit 29 stops the capstan motor 22.

At this time, the start time point of the stopping operation of the capstan 20 is corrected by t ₄ as compared with the previous still image reproducing operation.
The running distance of the magnetic tape 1 from the start to the stop of the capstan 20 is almost constant.

Therefore, in the case of (t ₄ = t ₂ ), the positional relationship between the head locus 5 when the magnetic tape 1 is stopped and the tracks 2 and 3 on which the video signal is recorded shows that the magnetic tape 1 is in time during driving. t
_The magnetic tape 1 moves in the forward direction, that is, in the leftward direction in FIG. 4 (a), by the distance advanced between ₂ as compared with the previous still image reproducing operation.

Similarly, in the case of (t ₄ = −t ₂ ′), the magnetic tape 1 is moved backward by the distance traveled by the magnetic tape 1 during the time (t ₂ ′) as compared with the previous still image reproducing operation. That is, in FIG. 3 (a), it moves to the right.

During the normal reproducing operation, the magnetic tape 1 outputs the head switching signal a
Recording track two periods during one cycle, i.e., the time t _a
It is traveling at a speed equivalent to the width of one track.

Therefore, if the distance traveled by the magnetic tape 1 during the time t _a is L _a , the magnetic tape 1 during the time t ₄ is (L _a / t _a ) × t ₄
Will only proceed. Therefore, when the start time of the stop operation of the capstan 20 is displaced by the time t _{4, the} stop position is displaced by (L _a / t _a ) × t ₄ .

Further, when the correction amount is t _4, the time difference between the head switching signal a and the video signal comparison signal h is t ₄ (−t _a <t ₄ ≦ t _a ), and when t ₄ = 0. The phase difference between the recording track and the magnetic head locus 5 is zero, that is, the positional relationship is optimum.

FIG. 5 shows the state in this case. FIG. 5 (a) shows the track pattern on the magnetic tape and the scanning trace of the magnetic head during still image reproduction, and FIG. 5 (b) shows the head switching signal. a, FIG. 5 (c), and FIG. 5 (d) show reproduced video signals f and g, and FIG. 5 (e) shows a video signal comparison signal h.

If the phase difference between the recording track and the magnetic head locus 5 when the correction amount is t ₄ , that is, the deviation from the optimum positional relationship is L ₄ , then L ₄ = (t ₄ / t _a ) × L _a = (L _a / t _a ) × t ₄ , and the amount of deviation of the magnetic tape 1, that is, the phase difference is equal to the corrected amount, and noise does not occur on the still screen at the corrected magnetic tape stop position.

Even if the speed of the magnetic tape 1 at the time of driving the capstan is not the same as the speed at the time of normal reproduction, if the speed of the magnetic tape 1 at the time of driving is S (S <1) of the speed at the time of normal reproduction, the capstan When the start time of the stop operation of 20 is shifted by the time t ₄ , the stop position of the magnetic tape 1 shifts by S × (L _a / t _a ) × t ₄ .

That is, by repeating the correction several times, the phase difference between the recording track and the locus of the magnetic head approaches zero, and a still image without noise is gradually obtained.

In this way, no noise is generated in the still image after the tape has been fed several times, and a slow reproduced image without noise can be obtained.

If a part of the video signal is missing due to scratches on the magnetic tape 1, the conventional magnetic video playback device detects only the missing part of the video signal by the video signal level detection circuit (41 in FIG. 6). Therefore, it is impossible to distinguish the image-missing portion due to the phase difference between the recording track and the magnetic head track 5 from the image-missing portion due to a scratch on the magnetic tape 1.

However, in the above embodiment, since the video signal comparison signal h compares the video signal levels of both tracks, when the stop position deviates from the optimum position with no noise, FIG.
As shown in, the output is comparatively wide, but if there is a scratch, the output is relatively steep because only the scratched part is output, so it is possible to easily distinguish. .

As shown in FIG. 2 (p), the video signal comparison signal h is set to "OFF" during the driving of the capstan, and to the "reverse phase" of the head switching signal a during the stopping operation, and the tape running movement amount and the stopping are performed. If the position is controlled, noise-free slow reproduction is possible without using the CTL signal c.

In this case, the amount of movement of the magnetic tape 1 can be detected by counting the number of rotations of the capstan motor 22.

〔The invention's effect〕

As described above, the present invention detects the phase difference between the recording track and the magnetic head locus by using the signal corresponding to the time difference between the video signal comparison signal and the head switching signal, so that the phase difference approaches zero. Since the running control circuit of the magnetic tape is controlled, the apparatus can be made inexpensive without adding an extra circuit such as a video signal level detection circuit.

Also, it is possible to accurately detect the phase difference between the recording track and the magnetic head locus without making any adjustments to variations in the video signal level, no malfunction due to scratches on the tape, and slow playback There is an effect that a more precise control of the tape running stop timing can be obtained, and a stable slow motion image without noise can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the magnetic image reproducing apparatus of the present invention, FIG. 2 is a time chart for explaining the operation of the magnetic image reproducing apparatus of the same as above, and FIGS. 3 to 5 are magnetic images of the same as above. FIG. 6 is a diagram showing a relationship among a track pattern on a magnetic tape, a scanning locus of a magnetic head, a reproduced video signal, a video signal comparison signal, and a head switching signal during reproduction of a still image by the reproducing apparatus, and FIG. 6 is a conventional magnetic video reproducing apparatus. FIG. 7 is a time chart for explaining the operation of the conventional magnetic image reproducing apparatus, and FIGS. 8A and 8B are on a magnetic tape of the conventional magnetic image reproducing apparatus. FIG. 9 is a diagram showing a track pattern and a scanning trace of a magnetic head, FIG. 9 is a diagram showing a relationship between a video signal and a video signal selection signal in a still image of a conventional magnetic image reproducing device, and FIG. 10 is a conventional magnetic image reproducing device. It is a graph showing the relationship of the video signal and the video signal comparison signal and the video signal selection signal during high speed reproduction. 1 ... magnetic tape, 10 ... magnetic image reproducing device, 11 ... head drum, 12-15 ... head, 18 ... recording / reproducing head, 22 ... capstan motor, 27 ... head switching signal generating circuit, 28 …… Capstan motor control circuit, 29 ……
Capstan motor drive circuit, 35, 36 ... Head changer, 37 ... Video signal comparator, 38 ... Video signal selection signal generation circuit, 39 ... Video signal selection circuit, 40 ... Pseudo vertical synchronization signal generation circuit , 43 …… Track position calculation circuit, 44 …… Tape running control correction circuit, 51 …… Tape running control circuit, 53
... Delay circuit, 70 ... Magnetic tape stop position control means, 80
...... Track position detection means. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A pair of heads in which a pair of heads having opposite azimuth angles are arranged adjacent to each other are mounted on a drum, and a magnetic tape on which a video signal is recorded is run by a predetermined length at a predetermined time interval. In the magnetic image reproducing apparatus which reproduces a still image and a moving image by selectively using the outputs of the adjacent heads and performs a slow reproduction operation, an image connected to each of the adjacent heads. A signal amplifier, a head switching signal generating circuit for generating a head switching signal in accordance with the rotation of the drum, a head switching device for switching and outputting the output of the video signal amplifier connected to each head facing the head switching signal, A video signal comparator for comparing the respective output levels of the head switching device to generate a video signal selection signal in a video signal selection signal generating circuit, A video signal selection circuit for selecting and outputting the output of the head switching device according to a selection signal, the head switching signal and the video signal selection signal are input, and calculation is performed based on the time difference between these signals. A track position calculation circuit for outputting a signal indicating a positional phase difference between the track and the reproducing head locus, and a tape running control correction circuit for outputting a tape running control correction signal for controlling the running control means by the signal indicating the phase difference. And a magnetic tape stop position control means for controlling the stop timing of the tape running by the tape running control correction signal to bring the phase difference close to zero. . 2. The structure according to claim 1, wherein the track position detecting means performs the detection operation a plurality of times, and outputs the average value or the majority decision value having the larger number of coincidences as the detection value. Magnetic image playback device.