JPH0580741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides a method for sequentially scanning a plurality of tracks by a rotating head from a recording medium on which information signals are recorded so as to form a plurality of tracks adjacent to each other. Accordingly, the present invention relates to an information signal reproducing device for reproducing the above-mentioned information signal. In particular, the present invention relates to a tracking device that controls tracking of the rotary head based on a reproduced output of a control signal for tracking control of the rotary head that is recorded together with the information signal on the information signal track.

[Technical background of the invention]

A helical scan video tape recorder (hereinafter referred to as VTR) is a typical example of the information signal reproducing device. This VTR is provided with a tracking device that corrects tracking deviations of the video head.

As this tracking device, in recent years, a device of a pilot type has been used. In this method, a tracking control signal (a so-called pilot signal) is recorded on a video signal track. Then, the video head reproduces the pilot signal and changes the running speed of the magnetic tape based on the reproduction output to control the relative position of the video head and the magnetic tape, thereby controlling the tracking of the video head. .

By the way, in VTRs, the head actuator is generally used to correct the linearity discrepancy between video signal tracks during recording and playback due to compatibility between devices, and to eliminate noise during still image playback. provided. This head actuator has an electromechanical transducer element that supports the video head on a rotating cylinder, and by applying a voltage to this element, the video head can be moved in the width direction of the video signal track. Therefore, the relative position of the video head and the magnetic tape can be controlled by the voltage applied to the conversion element, thereby making it possible to correct the linearity discrepancy and eliminate noise.

[Problems with background technology]

In the VTR described above, a tracking error signal indicating a deviation in the tracking position of the video head obtained from a pilot type tracking device is also applied to the head actuator, and the head actuator is used as a means for controlling the running speed of the magnetic tape. It is conceivable to control the tracking of the video head by both means. Here, since the pilot method tracking control controls the tracking of the video head by detecting the position of the video head itself, it is possible to control the tracking of the video head by simultaneously applying a tracking error signal to both of the above means. There is no problem with that.

However, by using a tracking error signal with exactly the same content for driving the head actuator and for driving the means for controlling the running of the magnetic tape, both can use the same effect on the control amount of tracking error. The stable point is no longer single and may become stable when either a positive or negative DC voltage is applied to the electrical/mechanical conversion element.

In this case, when using an element with a so-called bimorph structure, in which two piezoelectric ceramic plates are bonded together so that their polarization directions are in series, as the electric/mechanical transducer of the head actuator, the tip of the head tip and the magnetic tape may Contact may become unstable or the performance of the electrical/mechanical conversion element may deteriorate. That is, in the case of an electrical/mechanical transducer having a bimorph structure, the displacement of the video head is obtained by bending the bimorph. However, when tracking reaches a stable point when a DC voltage is applied to the electrical/mechanical transducer with this structure,
Since the tip of the head tip is oriented diagonally upward or downward compared to the non-displaced state, the contact between the tip of the head tip and the magnetic tape becomes unstable. Furthermore, if the applied DC voltage is excessive, it will affect the polarization of the piezoelectric ceramic plate, resulting in deterioration of device performance.

[Purpose of the invention]

This invention was made to address the above-mentioned circumstances, and even when a bimorph-structured electrical/mechanical transducer element is used, it is possible to prevent performance deterioration of the element and poor contact between the tip of the head chip and the recording medium. The purpose is to provide a tracking device. Particularly, the present invention provides a simple device for controlling an electric/mechanical conversion element and a capstan motor in an appropriate control mode according to each mode in both still image playback mode and normal playback mode. The purpose is to achieve this through configuration.

[Summary of the invention]

In this invention, the tracking error signal is band-separated, and the DC component of the tracking error signal is not applied to the means for displacing the rotary head in the width direction of the information signal track, so that the rotary head can be swung without displacement. This is how it was done.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In the following explanation, the case where the present invention is applied to a helical scan type VTR will be explained as a representative example.

First, pilot type tracking control will be explained with reference to FIG. FIG. 2 is a diagram showing an example of a tape format in the above-mentioned Hercal Scan type VTR. In Figure 2, 1
1 is the magnetic tape, X ₁ is the tape scanning direction, and X ₂ is the head scanning direction. A ₁ , A ₂ ,…
is a video signal track formed by one of the two video heads (hereinafter referred to as head A), and B ₁ , B ₂ , ... are formed by the other (hereinafter referred to as head B). This is a video signal track formed by

As pilot signals for tracking control, there are, for example, four signals having mutually different frequencies.
Assuming that these four pilot signals are P(f ₁ ) to P(f ₄ ), they are recorded one by one on each track A ₁ , B ₁ , etc. in a predetermined order, as shown in FIG. .

The magnetic tape 11 on which the pilot signals P(f ₁ ) to P(f ₄ ) are recorded as described above is transferred to video heads A and B.
When played back, the pilot signal is the pilot signal from the track being scanned (main track) (hereinafter referred to as main pilot signal).
Then, a pilot signal (hereinafter referred to as a crosstalk pilot signal) given as a crosstalk component from both adjacent tracks is reproduced. For example, as shown in FIG. 2, head B is connected to track B ₁
If we consider the case where P(f ₂ ) is obtained as the main pilot signal, P(f ₁ ), P(f ₃ )
is obtained as a crosstalk pilot signal.

Here, two crosstalk pilot signals P
By comparing the magnitudes of (f ₁ ) and P(f ₃ ), a tracking error signal S _E1 indicating the amount of tracking deviation of head B can be obtained. Therefore,
By controlling the running speed of the magnetic tape using this tracking error signal _SE1 , it is possible to obtain an appropriate tracking state in which the head center and track center coincide.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

In the figure, 12 is a capstan motor. 13 is a capstan which is rotationally driven by this motor 12, and 14 is a pinch roller which is pressed against this capstan 13. These capstan motor 12, capstan 13, and pinch roller 14 connect the magnetic tape 11 and video head A,
A first relative position control means for controlling the relative position of B is configured.

15 is a rotational frequency detector that detects the rotational frequency of the capstan 13; 16 is a frequency dividing circuit that divides the detection output of this detector 15; and 17 is a frequency dividing circuit 16.
18 is a phase compensation circuit; 18 is a phase compensation circuit; ₁₈ is a phase compensation circuit; 18 is a phase compensation circuit;
9 is an amplifier circuit, and 20 is a switch. The above circuit forms an automatic frequency control loop that controls the rotational frequency of the capstan. Here, the frequency dividing circuit 16
By changing the frequency division ratio, high-speed playback or slow playback can be set.

21 is an electrical/mechanical conversion element. Video heads A and B are supported by this element 21 and mounted on a rotating cylinder (not shown). This element 21
head A, depending on the level of the applied voltage.
The position of the video signal track in the width direction (the direction of the arrow (X ₃ ←→X ₄ ) shown in FIG. 2) in B can be controlled. This electrical/mechanical conversion element 21 constitutes a second relative position control means for controlling the relative positions of the magnetic tape 11 and the video heads A and B.

22 is a tracking error signal generation circuit that generates the tracking error signal S _E1 . This circuit 2
2 generates the tracking error signal S _E1 by comparing the levels of crosstalk pilot signals from both adjacent tracks reproduced by video heads A and B.

The above-mentioned capstan motor 20 and electric/mechanical conversion element 21 are driven by this tracking error signal S _E1 , and tracking error removal processing is performed.

In this case, the tracking error signal S _E1 is band-separated so that the DC component of the tracking error signal S _E1 is not applied to the electrical/mechanical conversion element 21.

That is, the tracking error signal S _E1 is input to the low-pass circuit 23 and the high-pass circuit 24. The low-pass circuit 23 extracts the low-frequency component (DC component C ₁₁ and low-frequency error component C ₁₂ ) C ₁ from the input tracking error signal S _E1 . On the other hand, the high-pass circuit 24 receives the input tracking error signal.
The low frequency component C ₁ is removed from S _E1 , and the high frequency error component (not including the DC component) C ₂ is extracted.

After the low frequency component C ₁ passes through the phase compensation circuit 25,
The adder circuit 26 adds the rotational frequency error signal S _E2 from the frequency discrimination circuit 17 to the capstan 13.
input into the automatic frequency control loop. As a result, the rotational frequency of the capstan 13 is controlled by the low frequency component _C1 of the tracking error signal _SE1 . As a result, the relative positions of the magnetic tape 11 and the video heads A and B are changed, and low-frequency tracking errors are eliminated.

On the other hand, the high-frequency error component C ₂ extracted by the high-pass circuit 24 is supplied to the amplifier circuit 28 after receiving phase compensation in the phase compensation circuit 27 . Then, the signal is amplified by the amplifier circuit 28 to a level capable of driving the electromechanical conversion element 21 and then applied to the element 21. This causes video heads A and B to move in the width direction of the track. As a result, the relative position between the magnetic tape 11 and the video heads A and B changes, and tracking errors are eliminated.

Here, the configuration and operation will be described when noiseless reproduction of still images is achieved using the electrical/mechanical conversion element 21.

This noiselessness is achieved by applying a predetermined DC voltage to the electromechanical conversion element 21 and changing the video heads A and B by a predetermined amount. however,
In this case, the DC voltage is set at a level that does not cause unstable contact between the tip of the head chip and the magnetic tape 11.

In the case of Fig. 1, this DC voltage is
It is created using the output of 3. Low pass circuit 23
The low frequency component _C1 output from the phase compensation circuit 29
After receiving phase compensation at , the amplitude is limited by an amplitude limiting circuit 30 and converted into a DC voltage. This DC voltage is applied to an adder circuit 32 via a switch 31 and added to the output of the phase compensation circuit 27. This addition output is amplified by the amplifier circuit 28, and used as a control voltage for noiseless generation by the electrical/mechanical conversion element 2.
given to 1. This suppresses the generation of noise during still image playback.

In the above configuration, since the amplitude of the DC voltage is sufficiently limited by the amplitude limiting circuit 30, the electrical/
An excessive DC voltage is not applied to the mechanical conversion element 21. Therefore, unstable contact between the tip of the head chip and the magnetic tape 11 can be avoided. On the other hand, since the high frequency error component _C2 is not subject to amplitude limitations, the high frequency tracking error can be sufficiently removed.

Further, in this still image reproduction, the switch 20 is turned off and the conveyance of the magnetic tape 11 is stopped. In this case, the switch 31 is turned on only when the magnetic tape 11 comes to a complete stop. By setting the timing for turning on the switch 31 as described above, the magnetic tape 1
The positions of the video heads A and B will not be displaced more than necessary due to unstable tape running during the transition period when moving from playback involving the transport of 1 to still image playback. Therefore, video heads A and B
This means that when the magnetic tape 11 is stopped, the closest track among the tracks to be tracked can be tracked. In other words, the DC voltage applied to the electrical/mechanical conversion element 21 can be minimized, and unstable contact between the magnetic tape 11 and the tip of the head chip can be avoided as much as possible.

Note that by turning on the switch 31 while the switch 20 is on, it is possible to correct the discrepancy in the linearity of the video signal track during recording and playback.

This embodiment described in detail above has the following effects.

The DC component _C11 of the tracking error signal S _E1 is not applied to the electrical/mechanical conversion element 21, and the video heads A and B are swung around the no-displacement state. Therefore, even if an element with a bimorph structure is used as the electrical/mechanical conversion element 21, the contact between the tip of the head chip and the magnetic tape 11 will not become unstable, and the element 21 will not deteriorate due to the application of excessive DC voltage. and destruction can be prevented.

In addition, the electrical/mechanical conversion element 21 for eliminating high-frequency tracking errors can also be used as the electrical/mechanical conversion element of the head actuator, which is used for noiseless still image playback, resulting in an increase in the number of parts. Not at all.

Note that this invention is of course applicable to systems other than VTRs.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a tracking device that can prevent performance deterioration of the device and poor contact between the tip of the head chip and the recording medium even when an electric/mechanical transducer element having a bimorph structure is used. can. Further, according to the present invention, it is possible to easily provide a device that controls the electric/mechanical conversion element and the capstan motor in an appropriate control mode according to each mode in both still image playback mode and normal playback mode. Achieved through configuration.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a tape format for explaining pilot type tracking. 11... Magnetic tape, 12... Capstan motor, 13... Capstan, 14... Pinch roller,
15... Rotation frequency detector, 16... Frequency dividing circuit, 17
...Frequency discrimination circuit, 18, 25, 27, 29... Phase compensation circuit, 19, 28... Amplification circuit, 20, 31
...Switch, 21...Electrical/mechanical conversion element, 22...
Tracking error signal generation circuit, 23...low pass circuit, 24...high pass circuit, 26, 32...addition circuit, 30...amplitude limiting circuit, A, B...video head.

Claims (1)

[Claims] 1. Based on the reproduction output of a control signal for tracking control of a rotary head recorded on a plurality of information signal tracks formed adjacently on a recording medium,
A tracking device that generates a tracking error signal indicating the amount of tracking deviation of the rotary head and controls the tracking of the rotary head according to this tracking error signal, extracts a high-frequency component of the tracking error signal, a first path that supplies a control signal to an electrical/mechanical transducer that supports the head; and a rotational frequency control of a capstan motor that extracts the low frequency component of the tracking error signal to drive the recording medium. a second path for providing an external control signal to the circuit; during still image reproduction, a low frequency component of the tracking error signal is led from the second path and added to the control signal of the electromechanical transducer; A tracking device comprising: a third path; and means for stopping the rotation of the capstan motor during still image reproduction.