JPH04348694A - Video tape recorder - Google Patents

Abstract

PURPOSE:To realize the accurate automatic tracking function of a VTR by implementing tracking control with a crosstalk component of a color signal. CONSTITUTION:An amplifier 12, an LPF 14 and a demodulation circuit 15 are provided respectively to the tape recorder to demodulate a color signal from a magnetic head 11. A color signal whose phase is decoded from the demodulation circuit 15 is delayed by one H at a delay circuit 16 and a subtractor circuit 17 subtracts the delayed color signal from the signal not delayed. The subtraction output represents a crosstalk component of adjacent tracks and used to average the crosstalk while being given to a burst portion averaging circuit 18. Then a tracking control circuit 20 is used to implement tracking control to minimize the crosstalk.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape recorder having an auto-tracking function.

0002

[Prior Art] In recent years, consumer video tape recorders (
There is an increasing demand for higher image quality and improved operability for VTRs (hereinafter referred to as VTRs). Auto tracking function is VT
This is an essential element for R, and more accurate auto-tracking control is required, especially in long-term magnetic tape mode.

A conventional auto-tracking circuit for a VTR will be explained below. FIG. 4 is a block diagram showing an example of the basic configuration of a conventional auto-tracking circuit. In the figure, a reproduction signal output from a magnetic head 1 is amplified by an amplifier 2, and detected by a detection circuit 3 into a video luminance signal, color signal, and audio signal, respectively. A portion of these detection outputs is input to a tracking control circuit 4, and tracking control is performed so that each output signal from the detection circuit 3 is maximized.

0004

[Problems to be Solved by the Invention] However, in such a configuration, the playback track position of the magnetic tape is controlled so that the output signal from the magnetic head is maximized, and the amount of crosstalk from adjacent scanning tracks is controlled. No detection is performed. For this reason, there has been a problem in that the actually controlled track position and the optimal track position on the magnetic tape do not necessarily match.

The present invention has been made in view of these conventional problems, and an object thereof is to provide a video tape recorder capable of performing auto-tracking control that accurately corresponds to the scanning track of a magnetic tape.

[0006]

[Means for Solving the Problems] The invention as set forth in claim 1 of the present application is a video tape recorder that records and reproduces video color signals by shifting the phase of the color signals for each horizontal scanning line, and which Comprising crosstalk detection means for detecting crosstalk components of color signals from adjacent tracks, and tracking control means for controlling the playback track position of the magnetic tape so that the crosstalk signal from the crosstalk detection means is minimized. It is characterized by:

The invention according to claim 2 of the present application is the video tape recorder according to claim 1, in which the crosstalk detection means demodulates the color signal whose phase has been restored from the reproduced color signal for each horizontal scanning period. a delay circuit that delays the demodulated color signal by an integral multiple of one horizontal period; a subtraction circuit that outputs a difference signal between the input and output signals of the delay circuit; and a video signal from the output of the subtraction circuit. The present invention is characterized in that it includes an averaging circuit that extracts a plurality of signals during the burst signal period and takes the average thereof, and provides the output of the averaging circuit to the tracking control means.

[0008]

[Operation] Claims 1 and 2 of the present application having such features
According to the invention, crosstalk components of color signals from adjacent tracks on a magnetic tape are detected, and the amount of track error from the crosstalk detection means is input to the tracking control means. In this way, tracking control is performed so that the crosstalk component of the color signal is minimized, rather than the position where the video signal is maximized.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an auto-tracking circuit used in the VTR of the present invention. The magnetic head 11 records and reproduces video luminance signals and color signals on tracks of a magnetic tape, and the output thereof is given to an amplifier 12 during reproduction. In the VTR of this embodiment, the video signal output from the amplifier 12 is given to the A/D converter 13, and the color signal is digitally processed. A
The output of the /D converter 13 is a low-pass filter (hereinafter referred to as LPF).
14, where the FM-modulated luminance signal is removed and the low-frequency converted color signal component is separated. The color signal from the LPF 14 is given to the demodulation circuit 15,
Here, the low frequency converted color signal is demodulated into a color difference signal, and the phase of each horizontal period is restored. Incidentally, such an amplifier 12, A/D converter 13, LPF 14, demodulation circuit 15
A video processing signal circuit consisting of the above is installed in the VTR regardless of the type of tracking control method.

Next, the output terminal of the demodulation circuit 15 is connected to a delay circuit 16.
and one input terminal 17b of the subtraction circuit 17, respectively. The delay circuit 16 converts the color signal from the demodulation circuit 15 into 1
This is a circuit that delays by a horizontal period (1H). The output of the delay circuit 16 is applied to the other terminal 17a of the subtraction circuit 17. The subtraction circuit 17 subtracts the color signal delayed by 1H from the original color signal to remove similar signal components included in the two scanning lines, and its output is given to the burst averaging circuit 18. . The burst part averaging circuit 18 receives the burst gate signal from the input terminal 19, extracts color signals from the color signals of each horizontal scanning period multiple times during the burst signal period, and averages the results.The output is used for tracking. The signal is applied to the control circuit 20. The tracking control circuit 20 is the same as the tracking control circuit 4 shown in the conventional example.
It is configured to perform the same signal processing as.

Now, a reproduction signal output from the magnetic head 11 by scanning each track of the magnetic tape is amplified by an amplifier 12. The output of the video signal from the amplifier 12 is an A/D
The signal is input to the converter 13 and once converted into a digital signal. This digital video signal is input to the LPF 14 and only the color signal component is separated. This color signal is applied to a demodulation circuit 15, where it is demodulated into a color difference signal. At this time, the phase of the color signal for each horizontal period (0°, ±90°, ±180°, ±
270°) is also restored to be constant. This color signal is input to the delay circuit 16 and delayed by a time of 1H. The chrominance signal and the delayed chrominance signal are respectively input to subtraction circuit 17-2.
The signal is applied to two input terminals 17a and 17b.

FIG. 2 shows a state in which color signals are recorded on tracks of a magnetic tape. For example, in the VHS system, the PS (Phase Shift) system is used to record color signals, and in each track, a color signal whose phase changes clockwise or counterclockwise by 90 degrees is recorded in the recording area of each horizontal scanning line. It is recorded every time. Track # indicated by A
1, a color signal with a phase angle of 0° is recorded on line A1,
+90° for line A2, +180° for line A3
, and line A4, color signals are respectively recorded to form a phase angle of +270°. In addition, in the adjacent track #2 indicated by B, there are 0°, -
Lines B1, B2, B3 and B4 with phase angles of 90°, -180° and -270° are formed.

FIG. 3 shows the color signals recorded using the PS method.
FIG. 3 is an explanatory diagram showing a signal processing procedure for outputting a crosstalk amount of a reproduced color signal. As shown in (a), the color signal from the main track to be scanned is indicated by arrow S, the crosstalked color signal from the adjacent track is indicated by thin arrow C,
It is assumed that these vectors represent the reproduction amplitude and phase angle of the color signal. (b) shows the reproduced output of the color signal reproduced from track #1, and the reproduced main signal of each line A1 to A5 and the crosstalk signal from the adjacent track (track #2) are indicated by arrows, respectively. Also, (c) is track #
2, and displays the reproduced main signal of each line B1 to B5 and the crosstalk signal from the adjacent track (track #1). The crosstalk color signals of track #2 have the same phase angles as the reproduced main signals of lines A1 to A5 of track #1, indicating that only their amplitudes are attenuated. When the phase of each line A1 to A5 of the reproduced output shown in (b) is restored to 0°, a state as shown in (d) is obtained. When the color signals of each line shown in (d) are passed through the delay circuit 16 of FIG. 1, they are delayed by 1H, resulting in the state shown in (e). Next, when the undelayed color signal (d) and the 1H-delayed color signal (e) are added by an adder circuit (not shown), only the color signal recorded on track #1 is reproduced, as shown in (f). It turns out. This means that even if the magnetic head 11 scans across tracks #1 and #2 and causes track misalignment, track #1
This is to make it possible to detect only the color signals from.

On the other hand, when the color signal shown in (d) and the color signal delayed by 1H shown in (e) are respectively input to the terminals 17b and 17a of the subtraction circuit 17 in FIG. The color signal shown in is obtained. Here, the color signals of lines A1 to A5 and lines B1 to B5 of tracks #1 and #2 are removed, and only the crosstalked color signals from adjacent tracks are emphasized and extracted as shown by arrow C. It turns out. That is, the subtraction circuit 17 operates so that the output is 0 when the magnetic head 11 does not cause a tracking error (on-track), and the output signal increases in accordance with the tracking error.

Next, a color signal (g) indicating the amount of crosstalk of the scanning track is applied to a burst averaging circuit 18. Among the color signals of each scanning line, the signal waveforms during the burst period are extremely similar except for the phase, regardless of the video content, and the amount of crosstalk of the color signal extracted from this period accurately corresponds to the track deviation. Become. Therefore, the crosstalk signal is averaged by extracting it from a plurality of lines during the scanning period of one field of the magnetic tape. Next, the output of the burst averaging circuit 18 is given to a tracking control circuit 20, and tracking control similar to the conventional one is performed.

PS color signal processing is originally intended to remove crosstalk color signals when a tracking error occurs, but here the color signals reproduced from the magnetic head are delayed by 1H and added. Instead, track error information is extracted by subtraction processing. Generally, tracks on a magnetic tape recorded in long-time mode are close to each other, so it is easier to detect the amount of crosstalk in color signals than when recorded in standard mode. In this embodiment, the color signal from the demodulation circuit 15 is
Although it is assumed that the delay is delayed by H, as long as the color signal processing is in the VHS system, the delay may be delayed by an odd number multiple of 1H.

[0017]

Effects of the Invention As described above in detail, according to the inventions of claims 1 and 2 of the present application, the phase is restored for each horizontal scanning period by demodulating the color signal reproduced from the magnetic head. Color signals can be obtained. By subtracting this color signal by a color signal delayed by 1H, crosstalk components of color signals from adjacent tracks can be detected. Accurate crosstalk information can be obtained by extracting this crosstalk color signal multiple times during the burst signal period. When this signal is input to the tracking control circuit to perform track control, the scanning track is positioned at a position where the amount of crosstalk is minimized. Therefore, compared to the conventional method that performs tracking control to maximize the playback output from the magnetic head, it has the effect of more accurate tracking control when adjacent tracks are close together, such as in long-duration mode. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an auto-tracking circuit used in a VTR according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state in which color signals are recorded on tracks of a magnetic tape in a VHS type VTR.

FIG. 3 is an explanatory diagram showing color signal processing in a VHS system VTR.

FIG. 4 is a block diagram showing an example of an auto-tracking circuit used in a conventional VTR.

[Explanation of symbols]

11 Magnetic head 12 Amplifier 13 A/D converter 14 LPF 15 Demodulation circuit 16 Delay circuit 17 Subtraction circuit 18 Burst part averaging circuit 20 Tracking control circuit

Claims (2)

[Claims] 1. A video tape recorder that records and reproduces video color signals by shifting the phase of the color signals for each horizontal scanning line, the video tape recorder detecting crosstalk components of color signals from adjacent tracks on a magnetic tape. A video tape recorder comprising: crosstalk detection means; and tracking control means for controlling a reproduction track position of the magnetic tape so that a crosstalk signal from the crosstalk detection means is minimized. 2. The crosstalk detection means includes a demodulation circuit that demodulates a color signal whose phase is restored from the reproduced color signal for each horizontal scanning period, and a demodulation circuit that demodulates the color signal whose phase is restored from the reproduced color signal for each horizontal scanning period, and a demodulation circuit that demodulates the color signal whose phase is restored from the reproduced color signal for each horizontal scanning period; a delay circuit that delays by a time; a subtraction circuit that outputs a difference signal between the input and output signals of the delay circuit; and a signal that is extracted multiple times from the output of the subtraction circuit for a period of the burst signal of the video signal. 2. The video tape recorder according to claim 1, further comprising an averaging circuit for taking the average, and providing an output of said averaging circuit to said tracking control means.