JPH0555678U - Automatic tracking device - Google Patents

Abstract

(57) [Summary] [Purpose] Performing highly accurate tracking control by focusing on the crosstalk component from adjacent tracks. [Structure] Until the reproduction envelope of the video signal and the reproduction envelope of the high-fidelity audio signal exceed a preset constant level, the tracking control circuit 28 performs tracking control with the aim of maximizing these reproduction envelopes and reproducing them. After the envelope exceeds a certain level, the tracking control circuit 28 performs tracking control with the aim of minimizing the crosstalk component from the adjacent track which the crosstalk detection circuit 27 converts into a DC voltage and outputs. Improves transient response and steady-state stability of tracking control.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to an automatic tracking device that enables highly accurate tracking control by focusing on crosstalk components from adjacent tracks.

[0002]

[Prior Art]

 The automatic tracking device 1 shown in FIG. 4 is a device for a home VHS system video tape recorder. The video signal read from the magnetic tape 3 by the video magnetic head 2 is sent to the luminance / color separation circuit 5 via the reproduction amplifier 4 and separated into a frequency-modulated luminance signal and a low-frequency conversion color signal, The luminance processing circuit 6 and the color processing circuit 7 respectively perform predetermined signal processing, and finally the adding circuit 8 adds the signals and outputs the NTSC signal to the outside. The high-fidelity audio signal deeply recorded on the magnetic tape 3 is read from the magnetic tape 3 by the audio magnetic head 9 and supplied to the FM demodulation circuit 11 via the reproduction amplifier 10 where it is FM-demodulated. It is output externally. Envelope detection circuits 12 and 13 for detecting the reproduction envelopes of the video signal and the audio signal, respectively, are branched and connected to the output lines of the reproduction amplifiers 4 and 10, and the reproduction envelopes of the video signal and the audio signal are respectively sized. Convert to a proportional DC voltage. The detection outputs of the envelope detection circuits 12 and 13 are supplied to the tracking control circuit 14, and a reference signal for providing a phase reference of the reproduction control signal in the servo circuit 15 is supplied so that the reproduction envelopes of the video signal and the audio signal are both maximized. It is delayed according to the output of the tracking control circuit 14. The servo circuit 15 compares the control signal reproduced by the control head 16 with a reference signal of 30 Hz which gives the phase reference, and adds the speed error signal from the speed servo system to the obtained phase error signal. The capstan 17 is rotationally controlled by.

Generally, when a reference signal that gives a phase reference of a reproduction control signal is delayed, the reproduction envelope changes into a trapezoid with respect to the delay amount as shown in FIG. Is selected as the optimum tracking point. Therefore, the tracking control circuit 14 samples the reproduction envelope at an appropriate cycle, and first, for example, gradually reduces the delay amount from the initial setting delay amount given by the preset position. At this time, the playback envelope sharply drops when it enters the left shoulder from the flat part of the trapezoid. Therefore, when the reproduction envelope falls from the level corresponding to the initially set delay amount by the constant level Ec, the delay amount is switched to the increasing side. As a result, the reproduction envelope changes from decreasing to increasing and moves to the right shoulder of the trapezoid via the flat portion where the level does not change much. Also here, when the reproduction envelope falls from the level corresponding to the initial setting delay amount by a constant level Ec, the delay amount is switched to the decreasing side this time. However, since it is clear that the level decrease this time occurred in the right shoulder part of the trapezoid, it was confirmed that the flat part up to that point was the upper part of the trapezoid, and at the same time, the level decrease of the first reproduction envelope was It is also confirmed that it occurred on the left shoulder of the trapezoid. Therefore, the tracking control circuit 14 specifies the point corresponding to the maximum value of the reproduction envelope obtained in the flat part of the trapezoid as the optimum tracking point, and gives this optimum tracking point, based on the tracking control process so far. The delay amount was set in the servo circuit 15.

[0004]

[Problems to be solved by the device]

 The conventional automatic tracking device 1 described above has a trapezoidal shape in which the reproduction envelope of the magnetic heads 2 and 9 to be tracking-controlled shows the delay amount when the reference signal that gives the phase reference of the reproduction control signal is delayed. Based on the change, the optimum tracking point was basically determined near the point where the playback envelope became the maximum, but when looking at the tracking control process, the delay amount gradually increased from the initial setting delay amount specified by the preset. Is decreased, the delay amount is inverted after passing the left shoulder portion from the flat portion to return to the flat portion, and after reaching the right shoulder portion, it returns to the point where the playback envelope becomes the maximum. There was a problem that it took more than one round trip and it took time to decide the optimum tracking point.

Further, unlike the recording in the standard mode, the conventional automatic tracking device 1 reproduces the crosstalk from the adjacent tracks when reproducing the guard bandless magnetic tape 3 recorded in the triple mode or the like. Since the crosstalk component causes the playback envelope to be inflated because it is greatly affected by the components, the playback envelope that is inflated by the crosstalk component is apparent even though it is actually outside the optimum tracking point. In some cases, the maximum point was mistaken for the optimum tracking point. In such a case, the crosstalk component from the adjacent track, which depends on the actual tracking error, affects the reproduced color signal, which tends to cause edge noise, and the reproduction envelope of the audio signal. Even if a method is used in which tracking control is performed by weighting the playback envelope of the video signal and the playback envelope of the video signal, the situation does not change. Therefore, the center of gravity of both playback envelopes of the audio signal and the video signal is set as the optimum tracking point. So I couldn't solve it.

[0006]

[Means for Solving the Problems]

 The present invention solves the above problem, and a crosstalk extraction for extracting a crosstalk component from an adjacent track superimposed on the color signal from a color processing circuit for reproducing the color signal read from the magnetic tape. Means and a tracking control means for supplying the crosstalk component from the crosstalk extraction means and performing tracking control so that the crosstalk component is minimized. Of the reproduction signal of the audio signal recorded on the same track as the reproduction envelope of the video signal or the video signal, and the color processing circuit for reproducing the color signal read from the magnetic tape, Crosstalk extracting means for extracting a crosstalk component from overlapping adjacent tracks; Is a tracking control aiming at maximizing the reproduction envelope until the reproduction envelope of the audio signal exceeds a predetermined level, and after the reproduction envelope exceeds the predetermined level, the crosstalk component The second feature is to provide a tracking control means for performing tracking control with the goal of minimizing

[0007]

[Action]

 This invention extracts a crosstalk component from an adjacent track that is superimposed on the color signal from a color processing circuit that reproduces the color signal read from the magnetic tape and performs tracking so that this crosstalk component is minimized. By controlling, tracking control is performed by an effective method when crosstalk components from adjacent tracks are significant. Furthermore, until the reproduction envelope of the video signal or the reproduction envelope of the audio signal recorded on the same track as the video signal exceeds a preset constant level, tracking control is performed with the goal of maximizing the reproduction envelope. After the reproduction envelope exceeds the predetermined level, the tracking control is performed with the aim of minimizing the crosstalk component, thereby enhancing the transient response and steady-state stability of the tracking control.

[0008]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. 1 is a schematic circuit configuration diagram showing an embodiment of the automatic tracking device of the present invention, FIG. 2 is a circuit configuration diagram of the color processing circuit shown in FIG. 1, and FIG. 3 is an automatic tracking device shown in FIG. It is a figure which shows the tracking control progress by an apparatus.

The automatic tracking device 21 shown in FIG. 1 uses a crosstalk component included in a reproduced color signal for tracking control. In the embodiment, a reproduction envelope of a video signal and a reproduction envelope of a hi-fi audio signal are used. Tracking control with the goal of maximizing these playback envelopes until a certain level exceeds a preset level, and minimizing the crosstalk component after these playback envelopes exceed a certain level. It is configured to perform tracking control on the target.

As shown in FIG. 2, the color processing circuit 7 returns the low-frequency converted color signal read from the magnetic tape to the original band by high-frequency conversion, and then cancels the PS processing. And a crosstalk canceller 23 connected downstream of the color process circuit 22. The crosstalk canceller 23 removes the crosstalk component by utilizing the phase inversion of the reproduction color signal for each line. In the embodiment, the line delay circuit 24 delays the reproduction color signal for one line period. And a subtraction circuit 25 for subtracting the reproduction color signal passed through the line delay circuit 24 from the original reproduction color signal. By the way, in contrast to the case where the color signal component is obtained by subtraction, the crosstalk component from the adjacent track is obtained by adding the reproduction color signal that has passed through the line delay circuit 24 and the original reproduction color signal. Here, an adder circuit 26 for extracting the crosstalk component is externally connected to the crosstalk canceller 23.

The crosstalk component obtained from the adder circuit 26 is supplied to the crosstalk detection circuit 27, where it is converted into a DC voltage substantially proportional to the magnitude of the crosstalk. The output voltage of the crosstalk detection circuit 27 is subjected to the minimum value detection in the tracking control circuit 28. Here, as described above, the reproduction envelope of the video signal and the reproduction envelope of the high-fidelity audio signal have a predetermined level. Tracking control is performed with the goal of maximizing these playback envelopes until it exceeds, and after these playback envelopes exceed the certain level, the crosstalk component included in the playback color signal is minimized. The method of tracking control to the target is used.

That is, until the reproduction envelopes of the video signal and the high-fidelity audio signal exceed a preset constant level, the crosstalk component contained in the reproduction color signal is not used as a judgment material, and these reproduction envelopes are maximized. Tracking control with the goal. For this reason, during this period, the tracking point at the preset position is almost good as shown in FIG. 3 immediately after the automatic tracking is started by the optimum tracking control focused on the reproduction envelope of the video signal and the audio signal. It is possible to drive into P quickly, which can improve the transient response at the beginning of tracking control. In FIG. 3, the delay amount is reduced to the left shoulder of the trapezoidal change indicated by the reproduction envelope with respect to the delay amount, and then the flat portion of the trapezoid is traced back to drive it into the region P. However, it is also possible to control so as to linearly reach the region P from the preset position. On the other hand, after the tracking point has been driven into the area P that is considered to be good, tracking control focusing on the crosstalk component contained in the reproduced color signal is not used as the judgment material for the reproduction envelope of the video signal and the hi-fi audio signal. By shifting, accurate tracking control that eliminates the influence of crosstalk components from adjacent tracks is possible, and the steady stability of tracking control can be improved. In this case, the optimum tracking point is reached before the right shoulder portion of the trapezoid is reached as in the conventional case, so the time until the optimum tracking point is found can be shortened. In the embodiment, the line delay circuit 24, the adder circuit 26, and the crosstalk detection circuit 27 constitute crosstalk extraction means, and the envelope detection circuits 12 and 13 respectively constitute envelope detection means. In the area P, a certain standard is set for the reproduction envelope, and a tracking state in which a reproduction envelope exceeding the reference is obtained is defined in the area.

As described above, the automatic tracking device 21 extracts the crosstalk component superimposed on the reproduced color signal from the color processing circuit 7 and supplies it to the tracking control circuit 28. In the area P, the crosstalk component is detected. Since the tracking control is configured to be the minimum, for example, when reproducing the magnetic tape 3 recorded in the triple mode in which the guard bandless recording is performed, it remains partially erased by overwriting. Since the recording track is tracked by the wide magnetic head 2 so as to straddle the adjacent tracks, when the crosstalk component from the adjacent tracks is significantly included, the reproduction envelope of the video signal is different from the conventional one. Even if there is an error in finding the optimum tracking point from the playback envelope of the audio signal or the audio signal, , It is possible to accurately find the optimum tracking point. This also enables tracking control that minimizes the crosstalk component of the color signal from the adjacent track, which improves the stability of the reproduced color signal and at the same time eliminates edge noise parasitic on the edge of the image. It can be suppressed well. Furthermore, since the jitter that causes the fluctuation of the reproduction time axis can be satisfactorily reduced, it is possible to improve the reproduction image quality in the triple mode particularly in a home video tape recorder.

In the above embodiment, the tracking control circuit 28 may be configured to perform tracking control by focusing only on the crosstalk component of the color signal. In addition to the crosstalk component of the color signal, Alternatively, only one of the reproduction envelopes of the high-fidelity audio signal may be added to the judgment material.

In the above embodiment, the NTSC system video tape recorder is taken as an example, but the automatic tracking device of the present invention can also be applied to the PAL system video tape recorder. Since the signal is composed of line-sequential signals of a red color difference signal and a blue color difference signal, the crosstalk canceller 23 should preferably use a delay circuit that delays for two line periods.

[0016]

[Effect of the device]

 As described above, the present invention extracts the crosstalk component from the adjacent track that is superimposed on the color signal from the color processing circuit that reproduces and processes the color signal read from the magnetic tape. Since the tracking control is configured to be the minimum, for example, when reproducing a magnetic tape recorded in triple mode in which guard bandless recording is performed, a recording track that remains partially erased by overwriting Is tracked by a wide magnetic head straddling adjacent tracks, and when crosstalk components from adjacent tracks are significantly included, the playback envelope of the video signal and the audio signal Even if the reproduction envelope causes an error in finding the optimum tracking point, An appropriate tracking point can be searched for, and tracking control that minimizes the crosstalk component of the color signal from the adjacent track is possible. The parasitic edge noise can be suppressed well, and the jitter that causes the fluctuation of the playback time axis can be reduced, so that the playback image quality in triple mode for home video tape recorders is especially good. It has excellent effects such as improvement of

Further, the tracking control means maximizes the reproduction envelope of the video signal or the reproduction envelope of the audio signal recorded on the same track as the video signal exceeds a preset constant level. Tracking control is performed with the aim of achieving the following, and after the playback envelope exceeds the certain level, tracking control is performed with the goal of minimizing the crosstalk component. With the optimal tracking focusing on the playback envelope, when the automatic tracking is started, the tracking point that is in the preset state can be quickly swept into the area that is considered to be good. Improves transient response and makes tracking points generally good After driving into the area, tracking control that focuses on the crosstalk component contained in the reproduced color signal enables accurate tracking control that eliminates the influence of the crosstalk component, which enables steady stability of the tracking control. It has the effect of being able to increase

[Brief description of drawings]

FIG. 1 is a schematic circuit configuration diagram showing an embodiment of an automatic tracking device of the present invention.

FIG. 2 is a circuit configuration diagram of a color processing circuit shown in FIG.

FIG. 3 is a diagram showing the progress of tracking control by the tracking control circuit shown in FIG. 1.

FIG. 4 is a schematic circuit configuration diagram showing an example of a conventional automatic tracking device.

5 is a diagram showing the progress of tracking control by the tracking control circuit shown in FIG.

[Explanation of symbols]

3 magnetic tape 7 color processing circuit 2, 9 magnetic head 12, 13 envelope detection means (envelope detection circuit) 21 automatic tracking device 24 crosstalk extraction means (line delay circuit) 25 crosstalk extraction means (subtraction circuit) 27 crosstalk extraction Means (crosstalk detection circuit) 28 Tracking control means (tracking control circuit)

Claims (2)

[Scope of utility model registration request] 1. A crosstalk extracting means for extracting a crosstalk component from an adjacent track which is superimposed on the color signal from a color processing circuit for reproducing the color signal read from the magnetic tape, and the crosstalk extracting means. An automatic tracking device, comprising: tracking control means for controlling the tracking so that the crosstalk component is minimized. 2. An envelope detection means for detecting a reproduction envelope of a video signal or a reproduction envelope of an audio signal recorded on the same track as the video signal, and a color processing circuit for reproducing the color signal read from the magnetic tape. To a crosstalk extraction means for extracting a crosstalk component from an adjacent track to be superimposed on the color signal, and the reproduction envelope of the video signal or the audio signal is maximized until the reproduction envelope exceeds a predetermined level. Tracking control means for performing tracking control with the aim of minimizing the crosstalk component after the reproduction envelope exceeds the predetermined level. apparatus.