JPS6056027B2 - Tape running speed control device for magnetic recording and playback equipment - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a helical scan rotary head type magnetic recording/reproducing device (hereinafter referred to as VTR) in which the tape running speed is kept constant during fast forwarding and rewinding of the tape. The present invention relates to a tape running speed control device.

[Technical background of the invention]

Generally, during fast forwarding and rewinding, the capstan does not participate in tape running, and the tape is run so as to be wound onto a take-up reel by a take-up reel drive motor.

At this time, the take-up reel drive motor is controlled to have a substantially constant rotational speed. Therefore, the running speed of the tape changes depending on the amount of tape wound onto the take-up reel. [Problems with the background technology] There is no problem with changes in tape speed as long as normal fast-forwarding and rewinding are performed, but for example, when the tape is running at high speed and playing video signals to reproduce the video signal, so-called high-speed In the playback state, the following problems occur.

In other words, in a so-called helical scan rotating head type VTR that sequentially forms recording tracks by a rotating video head diagonally with respect to the running direction of the tape, when performing fast-forward playback or rewind playback of a recorded tape, the tape Since the running speed of the video head is faster than the recording state, if the video head rotation speed is the same as that during recording,
, Tsudo does not trace correctly on the recording track, but traces across multiple tracks.

In normal recording systems, in order to prevent crosstalk between adjacent tracks during playback, a part (guard band) where no signal is recorded is provided between tracks, or two heads with different azimuth angles are used to separate each track. are recorded without gaps by each head, and the adjacent tracks serve as guard bands. In either case, peaks and valleys appear in the head playback output during fast forwarding and rewinding.

For example, the video head playback output in the azimuth recording method is as shown in FIG. As a result, the S/N (signal-to-noise ratio) becomes extremely poor in the valley part, and on the playback screen,
Appears as horizontal bands of noise.

As the tape running speed changes, the position and number of peaks and troughs in the playback output of the video head also change, causing noise bands to flow up and down on the screen, making it unsightly.

[Purpose of the invention]

This invention was made in response to the above points, and fast forward,
The purpose is to control the running speed of the tape to be constant during rewinding.

[Summary of the Invention] The present invention achieves the above object by providing a servo loop for controlling the reel drive motor so that the reproduction control signal has a constant frequency.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tape running speed control device for a VTR according to the present invention will be described in detail below with reference to the drawings.

Figure 1 shows the V of a general two-head helical scan system.
In TR, a drive transmission mechanism for running the tape is shown. In the figure, 1 is a tape supply reel, and the tape starts from this reel 1, goes to capstan 3, and then goes to capstan 3. The control head is wound around a cylinder 6 via a male guide pin 5, and is further routed to a take-up reel 10 via guide pins 7, 8, and 9.

Two video heads A and b are housed in the cylinder 6 and fixed on a rotating disk so as to be in contact with the tape obliquely with respect to the tape running direction. Also each reel 1, 1
0 are placed on stands 31 and 32, each having a drive shaft (not shown). During recording and reproduction, the tape 2 is run as follows.

A first pulley 13 fixed to the shaft of a capstan motor 12 and a capstan motor 12 are connected to each other. The knob I month 1 is hung by a belt, and rotation is transmitted to the capstan 3. Furthermore, rotation is transmitted from the second pulley 14 to the rapid feed idler pulley 15 by a belt. A fast-forward idler 16 coaxially with respect to the fast-forward rear idler pulley 5,
A third pulley 17 is provided, the third pulley) 1
Rotation is transmitted from the recording/reproducing idler 18 by a belt. By operating a recording/playback button (not shown), the pinch roller 19 moves in the direction of the first arrow 20, presses the tape 2 against the capstan 3, and causes the tape 2 to run. Simultaneously recording and reproducing; the idler 18 moves in the direction of the second arrow 21 and comes into pressure contact with the stand 32 of the take-up reel, applying rotational force to the take-up reel 10. As a result, the tape 2 travels while being wound onto the take-up reel 10. If it is in the recording state at this time, video track A is formed diagonally on the tape 2 by video head a, and video track B is formed by video head b, as shown in FIGS. 3 and 4. Video signals for fields are recorded.
At the same time, a control signal is recorded on the bottom edge of the tape 2 by the control head 4 for controlling each head A and B to correctly trace the recorded video track during reproduction, thereby forming a control track CT. During fast forwarding, by operating a fast forwarding button (not shown), the fast forwarding idler 16 moves in the direction of the arrow 22 in FIG. At the same time, the pinch roller 19 moves in the opposite direction to the first arrow 20 and separates from the capstan 3. Thereby, the tape 2 is driven only by the take-up reel 10 and runs at high speed. At this time, the recording/reproducing idler 18 is connected to the take-up reel stand 3.
He has left 2. In the rewind state, the rewind idler 23 moves to the fourth arrow 2 by operating a rewind button (not shown).
4, the pinch roller 19 presses against both the fast-forward idler 16 and the supply reel stand 31, applies a high rotational force to the supply reel 1 in the opposite direction to that during recording and reproduction, and the pinch roller 19 moves in the direction of the first arrow 20. It moves in the opposite direction and separates from capstan 3.

Thereby, the tape 2 is driven only by the take-up reel 10 and runs at high speed. At this time as well, the recording/reproducing idler 18 is detached from the take-up reel stand.

Video track A of tape 2 during fast forwarding and rewinding
, B of video heads A and B. The state of the base is as shown in FIGS. 3 and 4, and video tracks A and B are not being traced correctly.

FIG. 3 shows the fast-forwarding state, and FIG. 4 shows the rewinding state. Each arrow indicates the tape running direction, and video heads A and b trace from the bottom edge of the tape toward the top edge. In other words, in the fast-forward state, the relative speed between the tape 2 and video heads A and b becomes low, and the trace angles of the video heads A and b become larger than the angles of the video tracks A and B; The relative speed of A and b increases,
The trace angle of video heads A and b is video track A.
, B is smaller than the angle of B. For example, when video head a traces as shown in FIG. 3a, the playback outputs of video heads A and b are as shown in FIG. 5, 2n-1.
At the starting point of the trace, video head a is on video track B.
Since it is in contact with the video track A, almost no signal output is obtained, and as tracing progresses, the area in contact with the video track A increases, and the signal output also increases accordingly. The output is maximum when the video head a contacts only the video track A, and then decreases as the video head a traces over the video track B. Thereafter, by repeating this process, the reproduced output finally consists of three valleys and three peaks as shown in FIG. 4, 2n-1. In the valley, where there is almost no video signal, the S/N is extremely poor, and video head b traces as shown in Figure 3b.
The reproduced output similarly has three valleys and three peaks. In addition, video heads A and b are a″,
If tracing is performed as shown by b', the reproduced output will be as shown in FIG. 4, 2n. In any case, since there is almost no video signal in the valley, the S/N ratio is extremely poor, and when the valley is displayed on a television receiver, that part appears as a noise band. If the tape running speed is constant, this noise band will either stop on the screen or flow slowly up and down, making the screen easier to see.

In this invention, in order to keep the tape running speed constant, a control signal recorded on the control track CT of tape 2 is used, the running speed of tape 2 is detected from the reproduced control signal, and the reel drive motor is controlled. ing.

FIG. 2 shows an embodiment of a device for controlling the tape speed at a constant level during fast forwarding and rewinding according to the present invention.

In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals.

In the figure, 12 is a reel driving motor, and this motor 1
2 by tape winding or tape supply reel 10
, 1 are driven, and the tape 2 is run. At this time, the control signal is detected by the control head 4, is reproduced by the control signal reproducing circuit 41, and the speed detector 4 detects the control signal.
Leads to 2. The speed detector 42 can be of a general circuit configuration that measures the time between pulses. Since the frequency of the reproduction control signal changes depending on the running speed of the tape 2, the tape running speed is detected by measuring the time between the signal pulses. The speed detection signal is taken out as a DC voltage and supplied to the inverting input terminal (1) of an operational amplifier 44 via a resistor 43. A DC voltage divided by a resistor 45 and a variable resistor 46 from a power supply +B is applied to a non-inverting input terminal (10) of the operational amplifier 44 .
Further, a feedback resistor 47 is connected between the output terminal and the inverting input terminal (-) of the operational amplifier 44. Therefore, the voltage difference between the voltage set by the variable resistor 46 and the input voltage at the inverting input terminal (-) is obtained as an output, amplified by the DC amplifier 48, and applied to the reel drive motor 12. As described above, the automatic frequency control (AFC) servo ruge is formed so that the frequency of the reproduction control signal is constant, that is, the running speed of the tape 2 is constant.
The rotational speed of the reel drive motor 12 changes depending on the amount of winding of the tape 2. Due to the AFC servo loop as described above, the running speed of the tape 2 is kept constant, and the noise band on the screen of the television receiver either stops or gradually flows, making the playback screen easier to see.

In the above embodiments, the case where the present invention is applied to a high-speed playback device has been described, but the invention is not limited thereto.

〔Effect of the invention〕

As described above, according to the present invention, by providing a servo loop that controls the reel drive motor so that the frequency of the playback control signal is constant, the tape can be run at a constant speed even during fast forwarding and rewinding. Therefore, it is possible to provide a tape running speed control device that can perform the following steps.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a general tape running drive transmission mechanism in a VTR, FIG. 2 is a block diagram showing an embodiment of a tape running speed control device according to the present invention, and FIG. Fig. 4 is a block diagram showing the tape tracing state of the video head during fast forwarding, Fig. 4 is a block diagram showing the tape tracing state of the video head during rewinding, and Fig. 5 shows the playback output of the video head during fast forwarding and rewinding. FIG.

1, 10... Reel, 2... Magnetic tape, 4... Control head, 12...
... Reel drive motor, 42 ... Speed detector,
A, b... Video head.

Claims (1)

[Claims] 1. A magnetic strip on which a video signal is recorded by a rotating magnetic head that travels in the longitudinal direction at a predetermined speed and rotates diagonally with respect to the traveling direction, and a control signal of a constant frequency is recorded by a control head. a take-up reel for winding a tape; a reel drive motor that applies rotational force to the reel and causes the magnetic strip to travel at a higher speed than the aforementioned speed; and when the magnetic strip is in a high-speed running state. A magnetic recording/recording reproducing device comprising tape running control means for reproducing the control signal using the control head and controlling the reel drive motor so that the frequency of the reproduction control signal is constant. tape running speed control device.