JPH054735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a VTR that can reproduce stable images even in high-speed running mode.

FIG. 1 is a diagram showing an example of a tape running system of a helical scan type VTR, in which a magnetic tape 2 unwound from a supply reel 1 is wound around a rotating drum 3 over an angular range of approximately 300 degrees or more. Thereafter, it is wound up by the take-up reel 4. A tape tension control device 5 is provided between the supply reel 1 and the rotating drum 3. This device 5 is composed of a tension arm 6 and a spring 7 as shown in the figure.

8 and 9 are tape guides. Further, 11 is a capstan, 12 is a pinch roller, 13 is a timer roller, and 15 is a tape tension control device on the take-up side provided between the timer roller and the take-up reel 4, which is connected to a tension arm 16. It consists of a spring 17 attached to this. 2
1 is the erase head, 22 is the control head, 2
3 is an audio head.

Now, as is well known, the helical scan type VTR configured as described above can realize special playback modes such as still slow motion, quick motion, and reverse slow motion. However, recently, research and development efforts have been made to obtain stable reproduced images even in high-speed driving modes (high-speed forward driving mode and high-speed reverse driving mode) by dynamic tracking control of the rotating magnetic head provided on the rotating drum 3. is in progress.

However, as long as the tape running control device (not shown, the tension servo on the supply reel side has a system etc. on the supply reel side) provided in the tape running system 10 as shown in FIG. Tension disturbances occur immediately after mode switching, making it difficult to reproduce a stable image immediately after mode switching, and the direction of tension rapidly reversing, making it difficult to apply appropriate tension after mode switching. . The response speed of the reel tension, especially the servo system of the reel tension on the supply side, depends on the presence of tape resonance and the phase delay of the servo system caused by the mass of the supply reel, the tension detection arm 6, tape compliance, etc. This limitation is largely responsible for the inability of the tape tension to quickly respond to sudden changes in tape speed or tape running direction.

In particular, since the tape tension control device 5 provided in a normal tape running system has a buffering effect, this buffering effect actually causes deterioration of transient characteristics during direction changes in high-speed running mode.

2 and 3 show the resonance characteristics of the tape system, with the horizontal axis representing frequency and the vertical axis representing response. This response is obtained by detecting the displacement of the tension arm 6 when random noise is applied to the drive motor of the supply reel 1, and calculating the ratio between the detected output and the random noise.

In FIG. 2, a curve la shows the resonance characteristic of the tape system when the tape is run with the pinch roller 12 pressed against the capstan 11, that is, in the capstan running mode.
It has been confirmed that this resonance characteristic is hardly affected by the tape speed, and that if the tape runs even slightly, the resonance characteristic at that time becomes like the curve la.

On the other hand, if we look at the resonance characteristics in capstan stop mode, in which the tape is stopped with the pinch roller pressed, it will be as shown by curve lb in Figure 3. This resonance characteristic also makes the pinch roller 12
It has been confirmed that in a mode in which the tape is driven to run by the take-up reel 4 while being separated from the tape 1 (reel running mode), the resonance characteristics are almost the same as when the tape 2 is stopped.

Note that when the tape is driven in the reel running mode instead of the capstan running mode, the resonance characteristic is as shown by the curve lc in FIG. 2, and this resonance characteristic is almost the same as the capstan stop mode.

The reason why the resonance characteristics of the tape system are different between the capstan running mode and the tape stop mode (including the reel running mode; the same applies hereinafter) is that in the capstan running mode, the tape between the supply reel 1 and the capstan 11 is Running characteristics became a problem, and at this time the capstan 11
This seems to be due to the fact that the rotating drum 3 acts as a knot, whereas in the stop mode the influence of the rotating drum 3 is strong, and the rotating drum 3 acts as a knot.

Due to the resonance characteristics of tape systems, the limit of response speed has conventionally been set so as not to include these resonance characteristics. That is, if the response frequency of the servo system is determined to include the resonance frequency as shown in the figure, the servo system will oscillate around this resonance frequency, making it impossible to realize stable tension servo. Therefore, the response frequency of conventional servo systems is selected to be much lower than this resonance frequency.

As a result, the response speed of the servo system becomes slow, and especially when the tape running direction must be changed in high-speed running mode as described above, tension disturbances during and after the switching transition period can be absorbed sufficiently quickly. As a result, disturbances in image quality were unavoidable when changing direction of travel and for a certain period of time thereafter.

Therefore, in consideration of these points, this invention pays particular attention to the resonance characteristics of the tape system, and provides a special circuit configuration so that the resonance characteristics at these specific frequencies do not exist, especially in high-speed running mode. By eliminating the influence of resonance, high-speed response of the reel travel control system is made possible.

Therefore, by using this running control device, even when the tape running direction is changed in high-speed running mode, the image is not disturbed and stable image quality can be reproduced from the beginning of the direction change.

Next, an example of the present invention will be explained with reference to FIG. 4 and subsequent figures. In this invention, the tape tension control device 5 itself shown in FIG. 1 is used as tension detection means. In order to increase the response speed of the reel travel control system, each constant of the reel travel control device is selected to correspond to the response speed.

FIG. 4 shows an example of a reel travel control device according to the present invention, which corresponds to a conventional tape tension servo circuit. The amount of displacement of the tension arm 6 is detected by a detection element 31, and its output is amplified by an amplifier 32. The detection signal corresponding to the amount of displacement of the tension arm consists of a DC component and an AC component.

The DC component is an output related to tension fluctuations during steady state, and this DC component is output from the A-D converter 33.
After being supplied to the gain adjustment circuit 34 and converted to a level related to the tape running mode, the signal is supplied to the D-A converter 35 and converted to a predetermined DC component. be done. This is fed to a combiner 36.

On the other hand, the AC component in the detection signal is supplied to a phase corrector 40.

This phase corrector 40 is for inversely correcting the resonance characteristics of the tape system shown in FIGS. 2 and 3, and has an inverter 41 composed of an operational amplifier as shown in FIG. , first and second phase correction circuits 42 and 43 are connected between the input and output thereof. The first phase correction circuit 42 is a correction circuit for inversely correcting the resonance characteristics in the capstan running mode, and the second phase correction circuit 43 is for inversely correcting the resonance characteristics in the tape stop mode.

The first phase correction circuit 42 includes a secondary resonance type low-pass filter 42A and a differential amplifier 42B as shown in the figure.
The secondary resonant frequency of the low-pass filter 42A is selected to be a frequency near the resonant frequency in FIG. 2 (35 to 45 Hz in this example). on the other hand,
The second phase correction circuit 43 is also composed of a secondary resonance type low-pass filter 43A and a differential amplifier 43B, and the secondary resonance frequency of the low-pass filter 43A is selected near the resonance frequency (80 to 90Hz) shown in FIG. be done.

One of the outputs of these phase correction circuits 42 and 43 is switched by a switching circuit 44, and then supplied to a negative input terminal of an inverter 41. The switching circuit 44 is controlled by the output of a detector 45 which detects whether or not the table is running.

The tape speed detector 45 uses the output of a frequency generator provided in connection with the capstan 11, for example, and detects that "the tape is running" when there is an output from the frequency generator, and when there is no output from the frequency generator. detects that the tape is stopped. In addition,
With this kind of detection, if the tape speed is such that the output of the frequency generator is generated, it can be detected that the tape is "running" regardless of the tape running speed. is running at an extremely low speed, or the tape is vibrating due to noise in the control system, in other words, the amount of tape movement within a unit time is extremely small (in the present invention, (defined as a stopped mode) can be detected as being stopped, and thereby the switching circuit 44 can be stably controlled. When the running state of the tape 2 is detected by this detector 45,
The first phase correction circuit 42 is selected based on its output, and is connected to the feedback path of the inverter 41.

When the first phase correction circuit 42 is connected, the resonance characteristics of the tape system at that time become as shown by curve la' in Figure 2, and the peak due to resonance when the first phase correction circuit 42 is not connected is sufficiently suppressed. It can be suppressed. Therefore, even if the response speed of the reel tension servo system is increased, the tape travel control system does not resonate, and the response frequency can be extended to a high frequency range. Therefore, even in the high-speed running mode, the tape system and tape running control system can realize a steep response without oscillating.

On the other hand, detector 4 detects the mode in which the tape is stopped.
5 is detected, the second phase correction circuit 43 is connected to the feedback path of the inverter 41 by its output, and the resonance characteristic of the tape system at that time is shown by the curve lb in FIG. 'become that way. Therefore,
By inserting the second phase correction circuit 43, it is possible to sufficiently suppress resonance development in the high frequency range that occurs in the tape system, so even in this case, even if the response frequency is increased, the tape running control system etc. will not oscillate. Instead, you can expect a steep rise when changing direction.

The phase-corrected AC component is transferred to a first-order differentiator circuit 47.
As a result, the peak value occurring on the lower frequency side of the curve la in FIG. 2 is suppressed. The phase change is within 90°. This phase-corrected AC component is further supplied to a gain adjustment circuit 48 and adjusted to a predetermined level in each operation mode, and then supplied to a combiner 36 where it is combined with the DC component and then sent to the supply reel. The motor torque of the supply reel 1 is supplied to the drive motor torque control circuit 51, and the motor torque of the supply reel 1 is divided into these phase-corrected AC components and DC components.
It is controlled in a predetermined manner by the output of the component.

In addition, 50 is a control circuit controlled by key operation, and is a gain adjustment circuit 34, 4.
8 respectively. In this example, the level is controlled to be shifted to 1/2 of the level in the stop mode in the forward drive mode and twice as much in the reverse drive mode.

As explained above, in the present invention, the phase corrector 40 is provided to sufficiently suppress the resonance occurring in each mode of the tape, and the gain adjustment circuits 34 and 48 are configured to adjust the gain necessary for each running mode. As a result, the response speed of the tape running control system can be made faster than before, and in particular, stable tension control can be achieved even immediately after changing the running direction in high-speed running mode. Stable images can be played back.

In this way, the present invention stabilizes the image quality during each transition period when changing the direction of high-speed driving mode, that is, switching from high-speed forward driving mode to high-speed reverse driving mode, and switching from high-speed reverse driving mode to high-speed forward driving mode. At the same time, it is possible to stabilize the tape tension in the subsequent high-speed running mode, so that a constant image quality can always be obtained.

In the embodiment described above, the output of the frequency generator provided in the capstan 11 is used as means for detecting the mode in which the tape 2 is driven by the capstan 11 and the mode in which the tape 2 is substantially stopped. However, it is also possible to configure the state of each mode to be detected by other methods. Further, in the above embodiment, the capstan running mode in which the tape 2 is driven by the capstan 11 and the mode in which the tape 2 is stopped are detected, but the resonance characteristics in the reel running mode are different from the capstan stop mode. Since the resonant characteristics are approximately equal to the resonant characteristics of the mode, the reel running mode may be further detected and the second phase correction circuit may be selected in this mode to correct the resonant characteristics.

Furthermore, although the correction characteristic in the phase corrector 40 is selected to be the frequency located at the center of each resonance characteristic as described above, it may also be selected to be a frequency in the vicinity thereof.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a tape running system of a helical scan type VTR, FIGS. 2 and 3 are waveform diagrams for explaining the present invention, and FIG. 4 is an example of a tape running control device according to the present invention. The system diagram shown in FIG. 5 is a connection diagram of an example of a phase corrector. 1 is a supply reel, 3 is a rotating drum, 5 is a tape tension detection means, 11 is a capstan, 12
is a pinch roller, 30 is a tape tension servo circuit, 31 is a detection element, 40 is a phase corrector, 45
is the tape speed detector.

Claims (1)

[Scope of Claims] 1. A tape running control device in which a tape from a tape supply reel is wound around a rotating drum, and the tape is caused to run by a capstan, wherein: a first state in which the tape is driven by the capstan; and a second state in which the tape is stopped; a mode detection means for detecting tension of the tape running between the reel and the drum; For the output from the tension detection means,
a phase correction means for correcting the resonance characteristics of the tape corresponding to the at least two states; and a torque for controlling the rotational torque of the reel based on the output of the phase correction means and adjusting the tension of the tape to a predetermined value. 1. A tape running control device comprising: a control means, wherein the correction characteristic of the phase correction means is switched in accordance with the output of the mode detection means.