JPH0636588B2 - Video signal playback device - Google Patents

Description

The present invention relates to a video signal reproducing device using a pair of rotatable movable magnetic heads that are displaceable in a direction substantially orthogonal to the scanning direction.

[Outline of Invention]

The present invention relates to a video signal reproducing apparatus using a pair of rotatable movable magnetic heads that are displaceable in a direction substantially orthogonal to the scanning direction, and a pair of a pair of rotatable magnetic heads at the time of generating a magnetic head rotation phase pulse and at a standard speed running of a magnetic tape. The time between switching points of the switching signals for switching the respective reproduced video signals from the rotary movable magnetic head is C ₀ , and the time proportional to the initial displacement amount H at the start of scanning of the inclined tracks of the pair of rotary movable magnetic heads is CH.
(Where C is a proportional constant), a predetermined time D (= D ₀ −CH) is calculated using the initial displacement amount H obtained from the drive signal forming means for displacement driving the pair of rotary movable magnetic heads, and the magnetic field is calculated. The magnetic tape runs by setting the time between the switching time point of the switching signal for switching the reproduced video signal from the pair of rotary magnetic heads from the generation time point of the head rotation phase pulse at the calculated predetermined time D. The reproduced video signals from the pair of rotatable movable magnetic heads can be switched without loss regardless of the speed.

[Conventional technology]

FIG. 5 shows a track pattern on a magnetic tape in a video signal reproducing apparatus (beta cam type VTR) having a pair of rotatable movable magnetic heads. T _A and T _B indicate inclined tracks formed on the magnetic tape by the pair of rotatable movable magnetic heads when the magnetic tape is running at the standard speed in the direction of arrow a. Video signals are recorded on the respective inclined tracks so that the recording positions of the horizontal synchronizing signals are aligned. In this case, the phase difference between the start ends of the adjacent inclined tracks T _A and T _B is 4.5 H (H is a horizontal period). Equivalent to.
Incidentally, b indicates the scanning direction of the magnetic head at that time.

By the way, when the magnetic tape on which the video signal is recorded in this way is run at a speed three times higher than the standard speed, for example, a scanning track when scanning the magnetic tape without displacing the rotatable movable magnetic head. As shown by T _A3 , the magnetic tape becomes steeper and the length on the magnetic tape is shorter than that of the inclined track T _A1 when the magnetic tape is running at the standard speed. Then, even if the magnetic tape is running at three times the standard speed, a drive signal such as a sawtooth wave signal is sent to the bimorph of the rotary movable magnetic head so that the tilted track T _A1 can be scanned when running at the standard speed. The magnetic head is supplied to displace the magnetic head so that the scanning track T _A3 overlaps the inclined track T _A1 , for example. However, in this case, the rotary movable magnetic head has α and β times before and after one field time (the maximum value of the total of α and β times is 9H minutes).
The tilt track T _A1 must not be scanned only in time. By doing so, the reproduced video signal from the adjacent inclined tracks T _A and T _B has a large overlapping signal section.

By the way, the reproduced video signal reproduced by the pair of rotatable movable magnetic heads is supplied to the switching circuit and switched for each field by the fixed phase switching signal generated from the drum rotation phase pulse.

[Problems to be solved by the invention]

However, during variable speed reproduction, that is, when the magnetic tape is traveling at a traveling speed different from the standard traveling speed, the reproduction video signal obtained from the pair of rotary movable magnetic heads is supplied to the above-mentioned switching circuit to fix the above-mentioned fixed circuit. When switching is performed by the phase switching signal, the switching timing of this switching signal is set in accordance with the constant speed reproduction, so in the case of variable speed reproduction, the switching timing is poor and there is a possibility that part of the video signal will be lost. .

In view of such a point, the present invention provides a video signal reproducing apparatus having a pair of rotationally movable magnetic heads that can be displaced in a direction substantially orthogonal to the scanning direction, regardless of the traveling speed of the magnetic tape. The present invention intends to propose a device capable of switching the reproduced video signals from the magnetic head without omission.

[Means for solving problems]

In the video signal reproducing device according to the present invention, the head (1) is attached to the bimorph (2), and the pair of rotatable movable magnetic heads (3) are displaceable in a direction substantially orthogonal to the scanning direction.
And a drive signal forming means (4) for forming a drive signal according to the running speed of the magnetic tape and supplying the drive signal to the bimorph (2).
And a switching signal forming circuit (18) that forms a switching signal based on the magnetic head rotation phase pulse, and under control of this switching signal, the reproduced video signals from the pair of rotary movable magnetic heads (3) alternate. Switching circuit (21)
In the video signal reproducing device having the following, the time between the generation time of the magnetic head rotation phase pulse and the switching time point of the switching signal when the magnetic tape is running at the standard speed is C ₀ , and the inclined tracks of the pair of rotatable movable magnetic heads (3) When the time proportional to the initial displacement amount H at the start of scanning is CH (where C is a proportional constant), the initial displacement amount H obtained from the drive signal forming means (4) is used for a predetermined time D (= The switching signal forming circuit (1) is provided with a calculating means (13) for calculating C ₀ -CH).
It is characterized in that the time between the generation time of the magnetic head rotation phase pulse in 8) and the switching time of the switching signal is set by the predetermined time D calculated by the calculation means (13).

[Action]

According to the present invention described above, the switching timing to be supplied to the switching circuit (21) for switching the reproduced video signal from the pair of rotary movable magnetic heads (3) is changed according to the traveling speed of the magnetic tape during reproduction. As a result, the output reproduced video signal can be obtained without omission.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. (3) shows a pair of rotatable movable magnetic heads, each of which is constructed by attaching the head (1) to the tip of a bimorph (2). The other end of the bimorph (2) is attached to a part of the rotating drum of the tape guide drum. By supplying a drive signal to the bimorph (2), the rotary movable magnetic head (3) is displaced in a direction substantially orthogonal to the scanning direction. (30) indicates a microcomputer, and
The function of this microcomputer (30) will be described.
(4) is a drive signal forming means, which will be described below. The capstan rotation frequency signal generated by the frequency generator based on the rotation of the capstan is supplied to the counting means (7) as a clock signal. On the side edge of the magnetic tape, the control signal recorded corresponding to every other inclined track is reproduced by the fixed magnetic head,
It is supplied to the counting means (7) as a reset signal. The capstan rotation frequency signal is further supplied to the tape traveling speed detecting means (8) to detect the tape traveling speed, and the detection output thereof is at the start of scanning the inclined track of the rotatable movable magnetic head (3) by the bimorph (2). Is supplied to the initial displacement amount calculation means (9) to calculate the initial displacement amount. Then, the outputs of the counting means (7) and the initial displacement amount calculating means (9) are supplied to the combiner (10) and added. Thus, on the output side of the synthesizer (10), a digital output corresponding to the initial displacement amount H at the start of scanning of the inclined track of the rotary movable magnetic head is obtained, and this digital output is supplied to the counting means (12) as load data. . On the other hand, the drum rotation phase pulse (magnetic head rotation phase pulse) generated from the pulse generator in response to the rotation of the rotating drum of the tape guide drum transmits the scanning start timing signal at the entrance of the inclined track of the rotatable movable magnetic head (3). The timing signal, which is supplied to the signal generating means (11) for generating and is obtained from this, is the counting means (12).
Supplied as a load pulse. By doing so, the digitizing signal of the drive signal of the period or the inclination corresponding to the traveling speed of the magnetic tape and the initial displacement amount at the start of scanning of the inclined track and the magnetic tape traveling speed is output from the counting means (12). The output signal is supplied to the D / A converter (5), converted into an analog signal, and then supplied to the bimorph (2) via the drive amplifier (6).

Next, the calculation means (13) of the microcomputer (30) will be described. (14) is a latch circuit, which is the synthesizer described above.
The initial displacement amount which is the output of (10) is latched by the timing signal from the scanning start tamming signal generating means (11). The initial displacement amount H is supplied to the multiplication circuit (15) and multiplied by the proportional constant C, and then supplied to the combiner (17). (16) is a means for generating a constant C ₀ , which is a synthesizer (1
It is supplied to 7) and the output CH of the multiplier (15) is subtracted from this constant C ₀ . Thus, the combiner (17) outputs a signal of D (= C ₀ -CH) for a predetermined time.

On the other hand, the drum rotation phase pulse (see FIG. 2A) constitutes the switching signal forming circuit (18), and the switching signal generating means (1
9) and the obtained switching signal (see FIG. 2B)
Is supplied to the delay circuit (20) and delayed by the above-mentioned predetermined time D, and a switching signal (see FIG. 2C) is obtained at the output side thereof. Reference numeral (21) is a switching circuit for switching the reproduced video signals from the pair of rotary movable magnetic heads (3) supplied to the input terminals (22) and (23), which is switched by the switching signal from the switching signal forming circuit (18). The output reproduction video signal is output to the output terminal (24). Incidentally, SA and SB in FIG. 2 respectively show switching modes of reproduced video signals from the pair of rotatable movable magnetic heads (3).

Next, the operation of the main part of the present invention will be described with reference to FIG. 3 and FIG. In FIG. 3, T ₀ indicates an inclined track in which the magnetic tape may be running at standard speed. T
₁ , T ₂ are running speeds of the magnetic tape different from the standard speed,
For example, when traveling at a traveling speed higher than that, scanning tracks when scanning is performed without displacing the rotary movable magnetic head (3) are shown respectively. When the magnetic tape is running at a speed different from the standard running speed, the bimorph (2) causes the scanning track T to move.
It is necessary to displace ₁ and T ₂ by H ₁ and H _{2 respectively} at the start of scanning. Thus, the rotary movable magnetic head (3) has a displacement amount H ₁ , at the entrance side of the inclined track.
The tilt tracks T ₀ must be additionally scanned in proportion to H ₂ for the time periods E ₁ and E ₂ , respectively. Incidentally, L is a straight line connecting the starting ends of the respective inclined tracks.

By the way, when the magnetic tape is running at the standard running speed, the timing of the drum rotation phase pulse (magnetic head rotation phase pulse) P ₀ is delayed by a predetermined time C ₀ to obtain the switching signal switching timing ST _0. I have to. During variable speed reproduction, the drum rotation phase pulse is generated at the time points P ₁ and P ₂ , respectively. Therefore, the switching signal switching timing is obtained at the time points ST ₁ and ST ₂ which are delayed by C ₀ , respectively, and the rotation is performed. When each reproduction video signal from the movable magnetic head (3) is switched, when the rotary movable magnetic head (3) is displaced and the inclined track T ₀ is scanned, E ₁ , E _{2 in} the vicinity of the scanning start portion, Each has a missing part. Therefore, even when the magnetic tape is run at a running speed different from the standard running speed, it is necessary to match the switching timings ST ₁ and ST ₂ of the switching signal with the switching timing ST ₀ when considering each on the magnetic tape. .

To further explain this point, for example, the scanning track T
Consider a case where the rotary movable magnetic head (3) is displaced so that ₁ coincides with the inclined track T ₀ . In this case, (in the case of the scanning track _{T 2 Q 2)} intersections to _{Q 1} and the straight line L of the scanning tracks _{T 1} and. Also, the inclined track T ₀
A straight line passing through the intersection Q ₀ with the straight line L and intersecting the inclined track T ₀ is N. Then, for example, the scanning track T
And Drum rotation phase pulse P ₁ on _one extension line, the time between the timing ST ₁ switching this P ₁ is a C _0, in order to match the timing ST ₁ to ST _0, the drum rotation phase pulse It is necessary to generate a switching signal that switches at timing ST ₀ delayed from P ₁ by time D ₁ . In this case, E ₁ is the scanning track T ₁
Shows the time between points Q ₁ and Q ₀ when is superimposed on the tilt track T ₀ . That is, the delay amount D ₁ is obtained by subtracting the time E ₁ from the time C ₀ . Time E ₁ is the initial change amount H
Since for the specific column _1, when the ratio column constant C, E 1 ₌ CH ₁
Becomes Thus, from time _{C 0,} by subtracting the time was Hiretsu the initial displacement amount _{E 1} CH, drum rotation phase pulse _P delay time ₁ of the timing _D 1 _{(= C} 0 -CH
By generating the switching signal at the timing delayed by ₁ ), the reproduced video signal from the pair of rotary movable magnetic heads can be output without omission.

For example, a case of 3 × speed will be described as an example. Figure 4A,
B indicates a signal section in the vicinity of the vertical synchronizing signal VD of each reproduced video signal reproduced by the pair of rotatable movable magnetic heads (3). HD is a horizontal synchronization signal. FIG. 4B shows a case where the video signal of one field is numbered at the beginning, that is, every 3H from the front of the vertical synchronizing signal VD. In the case of the beta-cam type VTR, since the required signal section of the video signal of each field is from the 12th H to the end of the video signal section, the reproduced video signal reproduced by the pair of rotatable movable magnetic heads (3) is There is no problem even if the first to 11th H-numbers including the vertical synchronizing signal VD are lost. In the case of this beta cam type VTR, the phase difference between the starting ends of the adjacent inclined tracks is 4.5H as described above, and therefore, in the case of the triple speed, the phase difference between the reproduced video signals from the pair of rotary movable magnetic heads is 9H, so 11
A period of 2H, which is obtained by subtracting 9H (= 4.5H × 2) from H, is set as a timing possible period of the switching signal. So the fourth
As shown in FIG. C, it is understood that it is sufficient to generate a switching signal with a switching timing within the 2H section of the 10th H and the 11th H. For example, the switching timing of the switching signal is set at the 10th H position of the video signal of each field.

In the 3x to 2x speed reproduction, the switching timing possible period is 2H, and from the 1x speed to the still reproduction, 6.
It becomes 75H (= 4.5H x 1.5). Therefore, set the switching timing within each possible switching timing period,
Based on that, the proportional constant C is determined, and the delay time when the switching signal is formed from the drum rotation phase pulse may be determined.

〔The invention's effect〕

According to the present invention described above, in a video signal reproducing apparatus using a pair of rotatable movable magnetic heads, each reproduced video signal can be switched from the pair of rotatable movable magnetic heads without loss regardless of the running speed of the magnetic tape. You can get what you can.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal reproducing apparatus according to the present invention, FIG. 2 is a time chart for explaining switching timing, and FIG. 3 is a diagram for explaining delay time. FIG. 4 is a time chart for explaining the switching timing, and FIG. 5 is a pattern diagram showing a track pattern of the magnetic tape. (1) is a head, (2) is a bimorph, (3) is a rotary movable magnetic head, (4) is a drive signal generating means, (13) is a computing means, (18) is a switching signal forming circuit, and (19) is Switching signal generating means, (20) is a delay circuit, and (21) is a switching circuit.

Claims (1)

[Claims] 1. A pair of rotationally movable magnetic heads, each having a head attached to a bimorph and displaceable in a direction substantially orthogonal to a scanning direction, and a drive signal corresponding to a running speed of a magnetic tape, which forms a drive signal to the bimorph. A drive signal forming means to be supplied, a switching signal forming circuit for forming a switching signal based on a magnetic head rotation phase pulse, and each reproduced video signal from the pair of rotary movable magnetic heads under the control of the switching signal. In a video signal reproducing apparatus having a switching circuit which is switched alternately, the time between the generation time point of the magnetic head rotation phase pulse and the switching time point of the switching signal when the magnetic tape is running at standard speed is C ₀ , When the time proportional to the initial displacement amount H at the start of scanning of the inclined track of the rotatable movable magnetic head is CH (where C is a proportional constant), By using the initial displacement amount H obtained from the driving signal generating means is provided with calculating means for calculating a predetermined time D (= C 0 _-CH), said the time point of generation of the magnetic head rotational phase pulse in the switching signal generating circuit The time at the time of switching the switching signal is the predetermined time D calculated by the calculating means.
Video signal reproducing device characterized by being set in.