JPS6055777A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the horizontal deflection of a reproduced picture during switching of a reproduction mode by providing a reference signal generating circuit to produce a reference signal of a normal reproduction mode and a reference signal of variable speed reproduction mode respectively. CONSTITUTION:A reference signal generating circuit 21 produces a reference signal RP1 for phase comparison with a head control signal SP1 in a normal reproduction mode and a reference signal RP2 for phase comparison with a head control signal SP2 in a variable speed reproduction mode. The switching is carried out between signals RP1 and RP2 by a changeover switch 24 together with the switching between normal and variable speed reproduction modes. Thus a phase difference can be eliminated between signals SP1, SP2 and signals RP1, RP2 in a switching mode. This prevents the horizontal deflection of a reproduced picture when the switching is carried out between the normal and variable reproduction modes.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a single-rotation head type helical scan type (diagonal scanning type) magnetic recording device, and particularly relates to a magnetic recording device that can be used in addition to normal (standard) magnetic tape speed playback. 1 For example, 2x speed playback, 5
Double speed playback, reverse playback - double speed playback, slow playback,
So-called.

The present invention relates to a magnetic recording and reproducing apparatus including a servo control device for a rotary head device in which a pair of heads for variable speed reproduction is newly provided in addition to a pair of heads for normal reproduction in order to perform variable speed reproduction.

[Background of the invention]

A conventional magnetic recording and reproducing apparatus for video signals will be explained with reference to FIGS. 1 to 5.

FIG. 1 is a block diagram schematically showing a conventional oblique scanning type magnetic recording device, in which 1 indicates a magnetic tape.

2 is a capstan motor, 5 is a capstan control circuit,
4 is a control signal detector that detects a control signal on the magnetic tape, 5 is an amplification and waveform shaper, and 6 and 18 are phase comparators.

The phase comparator 6 consists of a sampling hold circuit 7 and a trapezoidal wave generating circuit 8, and the one phase comparator 18 consists of a sampling hold circuit 20 and a trapezoidal wave generating circuit 19. 9 is a rotating head drum, 10 is a first pair of heads, 11 is a second head
The head pair 10 and 11 are attached to a rotary head drum 9 at an angle of 90 degrees to each other in the rotational direction, and the rotary head drum 9 and the head pair 10 and 11 constitute a rotating gutter structure. 12 is a head drum motor, 15 is a drum control circuit, 14 is a head drum rotation phase detector, 15 is an amplifier, 16 is a head/throat control circuit (head switch control circuit), 17 is a head control signal generation circuit, and 21 is a reference. Signal generation circuit.

22 is a switch, and 25 is a variable speed reproduction command signal input terminal. 2 and 6 are waveform diagrams showing each signal in FIG. 1, and signals corresponding to those in FIG. 1 are given the same reference numerals.

Next, the operation shown in FIG. 1 will be explained with reference to FIGS. 2 and 6.

First, 1 normal playback will be explained. At this time, the video signal is reproduced by the one-rotation head 10 via a switching circuit (not shown). - The detection signal representing the head rotational phase detected by the rotational phase detector 14 is amplified by the amplifier 15 to obtain the signal TP. The signal Tp is applied to the head control signal generation circuit 17VC to obtain rectangular first and second head control signals S and SF3 which rise and fall a little later than the signal TP. The phases of the head control signals SP and SF20 correspond to the rotational phases of the head pair 10 and the head pair 110, respectively, and have a phase difference of 90° from each other as shown in FIG. During normal playback,
The switch 22 is connected to the terminal α and receives the head control signal SP.
is input to the head control circuit 16, and the head control circuit 16
is a continuous video signal (not shown), which alternately switches and extracts the reproduction outputs of the two heads constituting the first head pair 10 every positive and negative half cycle of the head control signal SP. I'm trying to get it. Further, the head control signal SP1 is supplied to a phase comparator 18, and a trapezoidal wave generating circuit 19 outputs trapezoidal wave signals LH and f. Further, the reference signal generation circuit 21 outputs a reference signal Rp.

The trapezoidal wave signal Lll and the reference signal RP are supplied to a sampling halt circuit 20, and a phase error signal EA representing the phase difference between the trapezoidal wave signal LE and the reference signal PR is obtained.

On the other hand, in the capstan phase control servo system, similar to the phase control of one or more head drums.

The control signal reproduced from the magnetic tape 1 and the reference signal Rp are phase-compared by a phase comparator 6, and the phase error signal obtained from the comparator 6 is applied to the capstan control circuit 3 to determine the running speed of the magnetic tape 1. is controlled.

Now, when the variable speed playback command signal VC is input to the head control circuit 16 from the terminal 25, the rotation is switched from the first rotary head pair 10 to the second rotary head pair 11 exclusively for variable speed playback. At the same time, the signal VC switches the switch 22 from contact a to contact i. From this, the head control signal S
P2 is supplied to the output control circuit 16, and the two heads constituting the head pair 11 are alternately switched every positive and negative half cycle of the head control signal SP2 to extract a reproduced video signal. The head control signal SP is also input to the phase comparison circuit 18, and as a result, the trapezoidal wave generating circuit 19 outputs the trapezoidal wave signal LH2. Here, up until now, the trapezoidal wave signal LH and the reference signal RP have been in a steady phase relationship with their phases matching, but due to the variable speed reproduction command signal RP, the phase comparison relationship between the trapezoidal wave signal LH2 and the reference signal RP is changed. Phase control is performed by switching to . Therefore, as shown in FIG. 6, a phase difference is detected in the single phase comparator 18,
A large phase error signal EA is output. Then, until the phase relationship between the one trapezoidal wave signal LE2 and the reference signal RP becomes the same as the phase relationship between the trapezoidal wave signal 1-H and the reference signal kP before the variable speed reproduction command, the one phase error signal EA is applied to the head drum control circuit. Added to 15. The state of the phase error signal EA at this time changes as shown in FIG. At this time, a large correction signal is applied to the drum motor 12, and during this period, the rotary head drum 9 is in an excessive state and shakes violently, so that the phase of the reproduced horizontal synchronization signal etc. is disturbed. Therefore, the AFC circuit of the television receiver fluctuates to the extent that it cannot follow it.

Horizontal shaking of the image occurs. The horizontal shaking of this image is very unsightly.

On the other hand, in the capstan control system, there is no change in the phase relationship even after the transition to variable speed regeneration compared to before the transition. For this reason, no large phase error is detected and fluctuations in the capstan 2 are not detected.
2 when switching from 0 to variable speed playback head pair 11.
A situation may occur in which the head to be switched among the pair of rotating heads 11 is separated from the tape 1, and in such a situation, a pressure reproduced image cannot be obtained after switching, and there are disadvantages such as noise appearing and an unsightly screen. there were.

The above describes the case of switching from normal playback to variable speed playback, but when switching from variable speed playback to normal playback, horizontal shaking and noise of one image similarly occur [Invention OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the drawbacks of the conventional apparatus described above, and to prevent horizontal shaking of reproduced images at the time of switching between the magnetic head for normal reproduction and the magnetic head for variable speed reproduction. The present invention provides a magnetic recording and reproducing device with a magnetic recording and reproducing system.

[Summary of the invention]

In order to achieve this object, the present invention provides (1) a first reference signal for phase comparison with the head control signal during normal playback, and a second reference signal for phase comparison with the head control signal during variable speed playback. A reference signal generation circuit is provided to generate the reference signal.

The first and second reference signals are switched at the same time as switching between energized regeneration and variable speed regeneration.

The feature is that it is possible to eliminate the phase difference between the head control signal and the reference signal at the time of such switching.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, in which 24 is a switch, and parts corresponding to those in FIG. Omitted.

5 and 6 are waveform diagrams showing signals of each part in FIG. 4, and signals corresponding to those in FIG. 4 are given the same reference numerals.

First, during normal playback, the switches 22 and 24 are each closed to contact a. This condition is.

The operation is exactly the same as the one-time playback described in the conventional example shown in FIG.

The switch 24 switches in synchronization with the switch 22.

The reference signals RP, RP2 of different phases generated by the reference signal generation circuit 21 are switched. Reference signal RP, .

The RP20 phase is the head control signal SP and the reference signal RP.
, the phase relationship between the head control signal SP2 and the reference signal RP.
2, which phase relationships are set to be equal to each other.

Now, when the variable speed reproduction command signal VC is input to the head control circuit 16 from the terminal 23, the head used is switched from the normal reproduction rotary head pair 10 to the variable speed reproduction exclusive head pair 11. At the same time, the switches 22 and 24 are respectively switched from contact a to contact Accordingly, each head of the rotating head pair 11 is alternately switched. Further, the head control signal SP2 is transmitted to the phase comparator 18.
Therefore, the output of the trapezoidal wave generating circuit 19 in the 1-phase comparator 18 is the trapezoidal wave signal Lll, to the trapezoidal wave signal LH2.
It changes in an instant. - side, reference signal generation circuit 2
Similarly, the reference signal from 1 is also the reference signal RP, to RP
2 and is input to the 1 phase comparator 18, and the 1
It is also supplied to the phase comparator 6. Therefore, 1 phase comparator 18
The phase relationship between the trapezoidal wave signal LH2 and the reference signal RP2 supplied to the sampling and hold circuit 20 inside is the same as during normal reproduction. Therefore, the phase error signal EA from the first phase comparator 18 is as shown in FIG.

There is no disturbance at all even immediately after shifting from normal playback to variable speed playback. Therefore, the rotational speed of the head drum 90 for one rotation is always constant, and no horizontal shaking of one image occurs.

Similarly, when switching from variable speed playback to normal playback, horizontal shaking of one image can be prevented by operating in the reverse order of the above operations.

On the other hand, the capstan phase control servo system.

During normal reproduction, the trapezoidal wave signal LT and the control signal CP reproduced from the magnetic tape 1 are supplied to the sampling and hold circuit 7, and the capstan motor 2 is controlled to rotate steadily by the phase error signal EB. . but.

The reference signal supplied to the phase comparator 6 by the variable speed reproduction command signal VC is the reference signal RP, and when it changes to the reference signal RP2, the output signal from the trapezoidal wave generation circuit 8 becomes the trapezoidal wave M LT, and then the trapezoidal wave signal. Immediately after switching to variable speed playback, the trapezoidal wave signal LT2 and control signal CP are supplied to the sample hold circuit 7 with a phase relationship as shown in FIG. 5, so a large phase difference occurs. A detected phase error signal EB as shown in FIG. 6 is output from the phase comparator 6. As a result.

In transient conditions immediately after switching to variable speed regeneration.

Capstan motor 2 shaking for a moment is a trap.

Image quality deteriorates due to mistracking. However, this image quality deterioration occurs only slightly in extreme cases,
It's not a visual problem.

Similarly, when returning from variable speed playback to normal playback, there is a slight deterioration in image quality due to temperature.

No problem.

As described above, this embodiment can prevent fluctuations in image quality even when switching between normal playback and variable speed playback. However, if the timing of this switching is made random, noise often occurs.

Therefore, another embodiment of the present invention that prevents the occurrence of such noise will be described with reference to FIGS. 7 and 8. FIG. 7 is an enlarged view of the rotating drum 9 in FIG. 4 seen from directly above, and its peripheral system is the same as that in FIG. 4. In FIG. 7, 10A, 10B, ++, 4. +1B is a rotating head. Also, in Figure 8, sp, and SF
3 are the same first and second head control signals (switch signals) as shown in FIG. 5, FA is a reproduction signal of the rotary heads 10 and 4, FB is a reproduction signal of the rotary head 10B, FA
2 is a reproduction signal of the rotary head 1+A, and a reproduction signal of the FB2 rotary head 1+B. The shaded portions of the reproduction signals FA, -FB2 indicate the operating range of each rotary head (period in which it is in contact with the tape).

In FIG. 7, the one-turn trim 9 is rotating in the direction of the arrow in the figure. Also, one rotation to Rad 10,4 and rotating head 1
0B constitutes a pair of rotary heads for normal reproduction, and the one-rotation rotary head ILA and the rotary head 11B are arranged perpendicularly to the rotary heads 10A and 10E, which are dedicated to variable speed reproduction. The head gap of the one-turn head 10A is set to a positive azimuth angle, and the head gaps of the one-turn heads 1°B, 1+A, and 11B are set to a negative azimuth angle. Further, at the time of transition from 1 normal reproduction to variable speed reproduction, the rotating head 10, 4 or +oB during 1 normal reproduction is switched to the rotating head 11A or 11B delayed by 900 phases.

Here, for example, by setting the timing of head switching within period C shown in FIG.

By synchronizing with the falling edge of the head control signal SP, the period during which the rotary heads 10B and 11B, which have the same azimuth angle, simultaneously output reproduction signals (the hatched part of the reproduction signal FB and the hatched part of the reproduction signal FB2) (range where the parts overlap) K will be switched.

No noise appears on the screen.

Further, as can be similarly understood from FIG. 8, when changing from variable speed playback to normal playback, the same applies.

By switching within the period C, for example, by switching in synchronization with the rise of the head control signal SP2, it is possible to prevent the generation of noise.

As described above, according to this embodiment, it is possible to prevent noise that occurs when switching between the normal reproduction head and the variable speed reproduction head.

It should be noted that all of the switching control as described above can be realized within the control IC, and there is no increase in the cost of the IC or an increase in the number of external components.

〔Effect of the invention〕

According to the present invention, in a diagonal scanning magnetic recording/reproducing apparatus having two rotary heads for normal playback and variable speed playback, during normal playback, a first pair of rotary heads for normal playback; a first control signal representing a rotational phase of the first control signal;
The first reference signal χ having a phase corresponding to the control signal of A second control signal is generated using a second rotating head pair, a second control signal representing the rotational phase of the second rotating head pair, and a second reference signal having a phase corresponding to the second control signal. Since the second reference signal is switched to be supplied to the servo system, it is possible to obtain a stable image without horizontal image shake even before and after this switching, and also, since the first control signal and a second control signal are used as switch signals for alternately switching the two rotary heads in the first rotary head pair and the two rotary heads in the second rotary head pair, respectively. By appropriately setting the timing of switching from normal playback to variable speed playback or vice versa in relation to the first or second control signal, it is possible to prevent the generation of noise before and after this switching, and the above-mentioned It is possible to provide a magnetic recording/reproducing device with excellent functions, except for the drawbacks of the prior art.

[Brief explanation of the drawing]

wL1 is a block diagram showing an example of a conventional magnetic recording/reproducing device, FIGS. 2 and 5 are waveform diagrams showing signals of each part in FIG. 1, and FIG. 4 is an implementation of the magnetic recording/reproducing device according to the present invention. A block diagram showing an example, FIGS. 5 and 6 are waveform diagrams showing the signals of each part in FIG. 4, and FIG. 7 is a rotation diagram for explaining another embodiment of the magnetic recording/reproducing apparatus according to the present invention. FIG. 8, which is a plan view showing the head structure, is a waveform chart for explaining the operation of this embodiment. 1...Magnetic tape, 2...Capstan motor. 3... Capstar 7 control 74 circuit, 4... Control signal detector, 6. IQ...phase comparator, 7.20
...Sample hold circuit, 8.19...Trapezoidal wave generation circuit. 9... Rotating head drum, 10... First rotating head pair, 11... Second rotating head pair, 13... Head drum control circuit, 14... Rotational phase detector, 16...
. . . Head control (2) circuit, 17 . . . Head control signal generation circuit, 21 . . . Reference signal generation circuit, 25 . . . Variable speed reproduction command signal input terminal. Continuing from page 1 of S Figure 7 8Z 0 Inventor Kenji Kano Inada, Katsuta City] 0 Inventor Kiyoshi Hiramatsu 1141 Hata, Inada, Katsuta City 41 Hata, Tokai Plant, Hitachi, Ltd. Hitachi, Ltd. Tokai Factory -482-

Claims (1)

[Claims] A rotary head structure includes a first pair of rotary heads for normal reproduction and a second pair of rotary heads for variable speed reproduction attached to a rotary body at different angles in the rotational direction; generating means for generating first and second control signals respectively representing rotational phases of the two pairs of rotary heads; and first and second control signals f each having a corresponding phase.
and a reference signal generating means for generating a second reference signal;
During normal reproduction, the reproduction signal of each head constituting the first rotary head pair is alternately switched by the first control signal, and during variable speed reproduction, the reproduction signal of each head constituting the second rotary head pair is switched alternately. The rotary head pair and the control signal for the switch circuit are switched so as to alternately switch according to the second control signal, and the phase comparison between the first control signal and the first reference signal is performed during normal playback, and during variable speed playback. the second control signal and the second
A magnetic recording/reproducing device 0 comprising means for switching a control signal and a reference signal supplied to a rotary head servo system so as to synchronize the rotational phase of the rotary head with the reference signal by comparing the phases of the reference signals.