JPH0467456A - Tracking control device - Google Patents

Abstract

PURPOSE:To reduce a noise on a picture by providing a means to adjust the phase of a traveling system to travel a tape, i.e., the revolving phase of a capstan motor so that a detection signal sampled at specified time becomes a peak. CONSTITUTION:At the time of special reproduction, a reproducing signal reproduced from the tape by a reproducing head 5 is amplified by a pre-amplifier 1, and afterwards, it is inputted to a DC detection circuit 2. The detection circuit 2 detects the level of the inputted signal, and outputs it to a microcomputer 3. The microcomputer 3 samples the inputted detection signal at the prescribed time T1, T2, T3, and executes control. Namely, the reproducing signal at the time of the special reproduction is sampled at the beginning time T1, the central part time T2 and the time at the vicinity of the end of a vertical scanning period, and the revolving phase of the capstan motor is controlled so that the level (detection signal of detection circuit 2) of the reproducing signal at the time T2 of the vicinity of the central part becomes the peak. Thus, the noise on the picture can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a tracking control device during special playback of a video tape recorder (VTR).

(Prior art) When performing double-speed playback or special playback such as stills on a VTR that records and plays back signals on magnetic tape using a helical scan method, the tape runs at a different speed than when recording, so the tape is The scanning playback head is shown in Figure 4 (A>,
As shown in (B), the signal is reproduced by diagonally crossing the recording track a on the tape 10 as indicated by the arrow in the figure.

For this reason, the signal waveform reproduced by the reproducing head becomes a waveform as shown in FIG. 5(B), and is no longer a flat waveform as in normal reproduction. However, the fifth
Figure (A) shows head switching pulses.

By the way, during the special reproduction, if the peak portion P of the wave-shaped reproduced signal shown in FIG. 5(B) is controlled to be at the center of the screen, a reproduced image with less noise can be obtained.

However, conventional VTRs are not equipped with a circuit that automatically detects the phase of the output waveform as described above, so the user manually adjusts the tracking to reduce noise on the screen. This had the disadvantage of poor operability.

(Problems to be Solved by the Invention) As mentioned above, in conventional VTRs, the reproduced signal has a waveform during special playback, so the phase of this waveform is adjusted.
Tracking adjustments must be made to reduce noise on the screen, but there is no circuit to automatically do this, and the user has to manually make the tracking adjustments while looking at the screen, resulting in poor operability. There was a drawback.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and provides a tracking control device that can automatically adjust tracking so as to obtain the best image based on the phase of a head reproduction signal during special reproduction. It is an object.

[Structure of the invention]

(Means for Solving the Problems) The present invention runs a magnetic tape, which is run at a predetermined speed and on which video signals are recorded diagonally and sequentially to form tracks by rotating magnets, at a speed different from the above speed. In the tracking control device for a video tape recorder having a special playback function of playing back the video signal by the rotating magnetic head while the rotating magnetic head is moving, the tracking control device includes a level detecting means for detecting the level of the playback signal played by the rotating magnetic head during the special playback. , a sampling means for sampling the level of the reproduction signal detected by the level detection means at a plurality of timings, and a magnitude relationship between a predetermined number of reproduction signals sampled by the sampling means satisfying a predetermined condition; and a phase control means for controlling the rotational phase of the tape running system so that the condition is satisfied by the determining means.

(Function) In the tracking control device of the present invention, the level detection means detects the level of the reproduction signal reproduced by the rotating magnetic head during special reproduction.

The sampling means samples the level of the reproduction signal detected by the level detection means at a plurality of timings. The determining means determines whether or not the level relationship of the predetermined number of reproduced signals sampled by the sampling means satisfies a predetermined condition. The phase control means controls the rotational phase of the tape running system so that the condition is satisfied by the determination means.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a tracking control device of the present invention. 1 is a preamplifier that amplifies the playback signal output from the playback head 5; 2 is a DC detection circuit 8 that detects the level of the playback signal output from the preamplifier 1;
3 is a microcomputer that performs tracking control based on the level of the reproduction signal output from the DC detection circuit 2; 4 is a capstan driver circuit that controls the speed and phase of a capstan motor (not shown); 5 is a tape drive circuit; This is a helical scanning playback head.

Here, the DC detection circuit #I2 constitutes a level detection means, and the microcomputer 3 constitutes a sampling means, a determination means, and a phase control means.

Next, the operation of this embodiment will be explained. During special playback, a playback signal played from a tape (not shown) by the playback head 5 is amplified by the preamplifier 1 and then sent to the DC
The signal is input to the detection circuit 2.

The DC detection circuit 82 detects the level of the input signal,
This is output to the A/D port of the microcomputer 3. The microcomputer 3 samples the detected signal input to the A/D boat at predetermined times T1, T2-T3, and performs the following control.

Here, FIG. 2 is a diagram showing the level of the detection signal (that is, corresponding to the level of the head output signal) sampled by the microcomputer 3 at times T1, T2, and T3. However, at the sampling times T1 is set to be at the beginning of the vertical scanning period, T2 is at the middle, and T3 is at the latter half.From this figure, the level of the detected signal sampled at time T2 is higher than the level of the detected signal sampled at other times T1 and T2. If the tracking is adjusted so that the detected signal sampled at this time T2 reaches its peak (this is the same as adjusting the phase of the running system that runs the tape, that is, the rotational phase of the capstan motor),
The peak value will be at the center of the screen.

By the way, when the second row from the top of the diagram shown in FIG. Assuming that the level of the detection signal at time T3 is 12 and the level of the detected signal at time T3 is L3, the following conditions hold true.

(1) Ll<L2 and L3<L2 However, under these conditions, the phase of the reproduced signal may be biased toward time T1 or T3, so in addition to the above conditions, (2) L
, =L3 only needs to be satisfied.

The microcomputer 3 operates the capstan driver #! so that the conditions (1) and (2) above are satisfied. When the rotational phase of the capstan motor (not shown) is controlled through the capstan motor (not shown), and as a result, the above conditions are satisfied, the output of the reproduced signal near the top and bottom ends of the monitor screen (not shown) will be almost the same, and The output of the playback signal in the center of the screen is as above.
Since it is larger than that at the bottom edge, noise on the screen can be reduced.

FIG. 3 is a flowchart showing tracking control processing by the microcomputer. First step 30
In step 1, the level of the reproduced signal (detected signal of DC detection circuit #I2) is sampled at times T1, T2, and T3, and then in step 302, it is determined whether the conditions of Ll<L and L3<L2 are satisfied. It is determined whether or not the condition of L1=L3 is satisfied, and if it is not satisfied, the process proceeds to step 303, and if it is satisfied, the process is performed to step 304.In step 304, it is determined whether the condition L1=L3 is satisfied, and if it is not satisfied, the process proceeds to step 304. Proceed to step 303, and if satisfied, return to step 301. In step 303, the rotation phase of the capstan motor is controlled via the capstan driver circuit 4, and step 302
Return to

According to this embodiment, the microcomputer 3 samples the playback signal during special playback at time T1 at the beginning of the vertical scanning period, at time T2 at the center, and at time T3 near the end,
Since the rotational phase of the capstan motor is controlled so that the level of the reproduction signal at time T2 near the center is at its peak, noise on the reproduction screen during special reproduction can be automatically minimized.

〔Effect of the invention〕

As described above, according to the tracking control device of the present invention, tracking adjustment can be automatically performed based on the phase of the head reproduction signal during special reproduction so as to obtain the best image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the tiger knocking control device of the present invention, FIG. 2 is a diagram showing an example of sampling the reproduced signal of the microcomputer shown in FIG. 1, and FIG. Figure 1 is a flowchart showing the tracking control process of the microcomputer, Figure 4 is a diagram showing an example of the travel trajectory of the head during special playback, and Figure 3 is an example of the head output playback signal during special playback. FIG. 1...Preamplifier 2...DC detection circuit 3...Microcomputer 4...Capstan driver circuit 5...Playback head agent Patent attorney Noriyoshi Chika Yudo Hiroshi Uji figure

Claims (1)

[Claims] A special method in which a magnetic tape is run at a predetermined speed and on which video signals are recorded diagonally and sequentially to form tracks by a rotating magnetic head, and the video signal is reproduced by the rotating magnetic head while running at a speed different from the above speed. A tracking control device for a video tape recorder having a playback function, comprising: level detection means for detecting the level of a playback signal played by the rotating magnetic head during the special playback; and a level of the playback signal detected by the level detection means. a sampling means for sampling at a plurality of timings; a determining means for determining whether or not a level relationship of a predetermined number of reproduction signals sampled by the sampling means satisfies a predetermined condition; A tracking control device comprising: phase control means for controlling the rotational phase of the system so that the determination means satisfies the condition.