JPS5983480A - Video tape recorder - Google Patents

Abstract

PURPOSE:To avoid skew and hue at variable speed reproduction from being fluctuated, by arranging the time bases of a reproducing signal of a main magnetic head and a sub-magnetic head placed closely in advance and outputting it with switching. CONSTITUTION:An output of a main magnetic head 1a and a sub-magnetic head 3a placed closely is given to a switching device 7 via reproducing amplifier circuits 4a, 4b, demodulating circuits 5a, 5b, AGC circuits 13a, 13b, ACC circuits 15a, 15b and mixing circuits 14a, 14b, and outputted from a terminal 8. The switching device 7 is switched by a flip-flop 11 to which a comparison output of envelope detecting circuits 9a, 9b and an output of synchronizing separation circuit are inputted. Variable delay circuits 17Y, 17C are inputted in the output path of the sub-magnetic head 3a and the time bases are arranged before being inputted to the switching device 7. Then, the skew and hue due to the switching is prevented from being fluctuated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video tape recorder (hereinafter abbreviated as VTR) for recording and reproducing video signals.

BACKGROUND ART AND PROBLEMS Generally, a VTR is provided with a rotating magnetic head device for recording and reproducing video signals.

In this rotating magnetic head device, as shown in FIG. ) and (1b), the azimuth angles of the head gaps are, for example, 7 degrees in different directions as shown in FIGS. 2A and B, and the video signal is recorded on the videotape (2) without a guard band as shown in FIG. It is done as if to record.

In such a VTR, magnetic heads (1a) and (1b)
The recording tracks a and b are every other track, and during reproduction, the recording track a recorded by the magnetic head (1a) is reproduced only by the magnetic head (1a) with the same azimuth, and the recording track a is recorded by the magnetic head (1b). Since the recorded recording track b is reproduced only by the magnetic head (1b) having the same azimuth as this, a good reproduced output signal without crosstalk can be obtained even when recording is performed without a guard band. Such a VTR
For example, when performing a high-speed picture search at 4x speed, the reproduction trajectory C by the magnetic heads (1a) and (1b) is
and d cross a plurality of recording tracks a and b, respectively, as shown in FIG. As a result, the output level of the reproduced composite video signal becomes diamond-shaped as shown in FIG. 4, and the output level becomes zero at the joint between each recording track, resulting in a noise bar on the monitor's video screen, which is extremely difficult to see.

The same applies to other variable speed playbacks such as slow playback.

For this reason, a method as shown in FIGS. 5 and 6 has been proposed as a method for obtaining an easy-to-see reproduced video screen without noise bars even during variable-speed reproduction such as in high-speed picture search.

In this VTR, as shown in FIG. 5 (in the rotating magnetic head device of the VTR, in addition to the main magnetic heads (1a) and (1b) as shown in FIG. A sub magnetic head (3a) whose azimuth is the same as that of the magnetic head (1b) is provided at the position where the azimuth is the same as that of the magnetic head (1b), and a sub magnetic head (3b) whose azimuth is the same as that of the magnetic head (1a) is provided at a position adjacent to the magnetic head (1b). .

In this case, the magnetic head (1a) and the magnetic head (3a) are made to have the same reproduction locus, and the magnetic head (1b)
and the magnetic head (3b) so that they have the same reproduction locus.

In this example, during recording, the main magnetic head (1a) is
and (1b) to record the video signal without a guard band as shown in Figure 3, and also use the main magnetic heads (1a) and (1b) during steady playback in the same manner as in Figure 1. Obtain a video playback output signal.

In this example, in the case of high-speed picture search, etc., the reproduction signals of the main magnetic heads (la) and (lb) and the reproduction signals of the sub magnetic heads (3a) and (3b) are switched as shown in FIG. Make it. Here, when switching between the reproduction signal of the main magnetic head (1b) and the reproduction signal of the sub magnetic head (3b), the reproduction signal of the main magnetic head (1a) and the reproduction signal of the sub magnetic head (3b) are switched.
This is the same as the case of switching between the reproduction signal of the main magnetic head (1a) and the reproduction signal of the auxiliary magnetic head (3a) in FIG. 6. do. In this case, the video signal recorded by the main magnetic head (1a) can be reproduced by the sub magnetic head (3b), and the video signal recorded by the main magnetic head (1b) can be reproduced by the sub magnetic head (3b).
a) can be played back.

In FIG. 6, the reproduction signals of the main magnetic head (1a) and the sub-magnetic head (3a) are respectively transmitted to the reproduction amplifier circuit (
demodulation circuits (5a) and (5) via 4a) and (4b).
b), and the demodulation circuits (5a) and (5b)
The respective demodulated video signals are supplied to the switching device (one and the other fixed contacts (7a) and (7b), respectively, and the movable contact (7c) of this switching device (7) is connected to the video signal output terminal (8). Connect to.

Furthermore, the high frequency signals obtained at the output side of the regenerative amplifier circuits (4a) and (4b) are transmitted to the envelope detection circuits (9a) and (9b).
are supplied to the envelope detection circuits (9a) and (9b), respectively.
) are supplied to one input terminal (2) and the other input terminal (e) of the comparator circuit 00).

In this case, when the signal level supplied to one input terminal ■ is higher than the signal level supplied to the other input terminal ○, this comparator circuit α0) obtains a high level signal “1” at this output terminal. When the signal level supplied to one input terminal ■ is lower than the signal level supplied to the other input terminal e, a low level signal “0” is output to this output terminal.
It is done so that it can be obtained. The output terminal of this comparison circuit (10) is connected to the D terminal of the D-flip-flop circuit 0υ. In addition, the video signal obtained at the video signal output terminal (8) is supplied to the synchronous separation circuit (12+), and this synchronous separation circuit (
The horizontal synchronizing signal as shown in FIG. 7A obtained at the output side of
The movable contact (7) of the switch (7) is switched by the signal obtained at the Q output terminal of the D-flip-flop circuit OD.
C) (in this case, this D-), the Q output terminal of the flip-flop circuit 011 receives a high level signal "1".
In this case, the movable contact (7C) of this switch (7) is connected to one of the fixed contacts (7a), and when this Q output terminal is a low level signal "0", this switch (7)
The movable contact (7C) is connected to the other fixed contact (7b). The rest of the structure is similar to that of a well-known VTR.

To explain the operation shown in FIG. 6, a case will be described in which, for example, a high-speed picture search is performed at 4 times the speed. In this case, the reproduction trajectories of the magnetic heads (1a) and (3a) are almost the same, as shown in the trajectory C in FIG.
As a result, the magnetic head (1a) reproduces only recording track a, and the magnetic head (3a) reproduces recording track b.
Since the reproduction output signal level of the magnetic head (1a) has a diamond shape as shown in FIG. 8A, and the reproduction output signal level of the magnetic head (3a) has a diamond shape as shown in FIG. 8B. . These magnetic heads (1a) and (3a)
This reproduced signal is sent to envelope detection circuits (9a) and (9b).
As shown in FIG. 8A and B, a diamond-shaped envelope waveform as shown in FIG. The output signal obtained at the output side of this comparator circuit is as shown in FIG.
The input low level signal is "0", and at time t2, the low level signal "0" changes to a high level signal "1'', and this is sequentially repeated.

The output signal of this comparator circuit αα as shown in FIG. 8C is D-
It is supplied to the D terminal of the flip-flop circuit fil).

Referring to FIG. 7, the operation of this D-flip-flop circuit near time t2 when the signal supplied to the D terminal changes from the low level signal "0" to the high level signal "1" will be explained. This D-flip-flop circuit (1
1), when the low level signal changes from "0" to "1" at time t2 as shown in FIG. 7B, the signal supplied to the trigger terminal T immediately after that is supplied to the trigger terminal T. As shown in FIG. 7C, the output signal of the Q output terminal of the D-flip-flop circuit (1υ) changes from the low level signal "0" to the high level signal "1" as shown in FIG.
This changed high level signal "1" causes the switch (force movable contact (7C) to switch to one fixed contact (7a).
). In this case, the movable contact (
Since the switching 7c) is performed in synchronization with the horizontal synchronizing signal as shown in FIG. 7C, this switching is performed within the horizontal blanking period and does not affect the video screen.

In this case, the movable contact (7c) of the switch (7) is switched and connected to the one of the envelope detection circuits (9a) and (9b) that has a higher output level, so that the video signal obtained at this movable contact (7c) is The output signal level is always above a predetermined level as shown in Figure 8, and the video signal obtained from this movable contact (7C) is supplied to the video signal output terminal (8), and a video screen of this video signal is obtained. Therefore, an easy-to-read image without noise bars can be obtained.

Also, in the case of other variable speed playback such as through playback, the same operation is performed and an easy-to-see image can be obtained.

However, in such a VTR as shown in FIGS. 5 and 6, the difference between the demodulated video signal of the reproduction signal of the main magnetic head (1a) and the demodulated video signal of the reproduction signal of the sub magnetic head (3a) is Due to a shift in the time axis, the arrangement (H arrangement) of each horizontal synchronizing signal is shifted, and when the movable contact (7C) of the switch (7) is switched, the video signal from the main magnetic head (1a) and the sub magnetic head are (3a) Skew on the video screen at the switching point with the video signal.

There was a risk that the temperature would fluctuate and become unpredictable.

OBJECTS OF THE INVENTION In view of the above, an object of the present invention is to prevent the above-mentioned noise bars from occurring during variable speed playback such as high-speed picture search, and also to prevent the above-mentioned skew and hue fluctuation from occurring.

Summary of the Invention The present invention provides first and second
A main magnetic head and a first sub-magnetic head are disposed close to each other and have the same azimuth as the first sub-magnetic head and a second main magnetic head having the same azimuth as the first sub-magnetic head. and a second sub-magnetic head with a second sub-magnetic head, which enables recording without a guard band during recording, and switches between a reproduction signal of the first main magnetic head and a reproduction signal of the first sub-magnetic head during variable-speed reproduction. In a video tape recorder in which a reproduction output signal is obtained by switching between a reproduction signal of a second main magnetic head and a reproduction signal of a second sub-magnetic head, a variable delay means is provided between the first and second magnetic heads. The time axes of the reproduction signal of the main magnetic head and the reproduction signal of the first and second sub-magnetic heads are aligned before this switching, and according to the present invention, speed changes such as high-speed picture search, etc. It is possible to prevent noise bars from occurring during reproduction, and also to prevent skew and hue fluctuations from occurring.

Embodiment An embodiment of the video tape recorder of the present invention will be described below with reference to FIG. In this Figure 9, the 6th
Portions corresponding to those in the figures are given the same reference numerals, and detailed explanation thereof will be omitted.

In this example, as in FIG. 5, in the rotary magnetic head device of a VTR, a magnetic head (1a) is located close to the main magnetic head (1a) at a position where the spacing between the gears is, for example, 1.25 H (H is the horizontal periodic spacing). A sub magnetic head (3a) whose azimuth is the same as that of the magnetic head (1b) is provided, and a sub magnetic head (3a) whose azimuth is the same as that of the magnetic head (1a) is provided close to the main magnetic head (1b) at a position where the spacing between gears is, for example, 1.25 H. A head (3b) is provided. In this case, the magnetic heads (1a) and (3a) are made to have the same reproduction locus, and the magnetic heads (1b) and (
The playback trajectory is the same as in 3b).

In this example, when recording, the main magnetic heads (1a) and (1b) are used as in Fig. 1, and the video signal is recorded without a guard band as shown in Fig. The magnetic heads (1a) and (1b) are used to obtain a video reproduction output signal in the same way as in the conventional case.

In this example, in the case of high-speed picture search, etc., the reproduction signals of the main magnetic heads (la) and (Ib) and the sub magnetic head (
The reproduction signals 3a) and (3b) are switched as shown in FIG. Here, when switching between the reproduction signal of the main magnetic head (1b) and the reproduction signal of the sub magnetic head (3b), the reproduction signal of the main magnetic head (1a) and the reproduction signal of the sub magnetic head (3b) are switched.
This is the same as the case of switching between the reproduction signal of a), so in this FIG. 9, the case of switching between the reproduction signal of the main magnetic head (1a) and the reproduction signal of the sub magnetic head (3a) will be explained. .

In FIG. 9, the reproduction signals of the main magnetic head (1a) and the sub-magnetic head (3a) are respectively transmitted to the reproduction amplifier circuit (
4a) and (4b). In this case, the regenerative amplifier circuits (4a) and (4b) are configured to separately obtain a luminance signal Y and a color signal C on their output sides. This regenerative amplifier circuit (
The luminance signal Y obtained at the luminance signal output terminal (4Ya) of 4a) is supplied to one input terminal of the mixing circuit (14a) via a series circuit of a demodulation circuit (5a) and an AGC circuit (13a). Further, the color signal C obtained at the color signal output terminal (4Ca) of this regenerative amplifier circuit (4a) is sent to the ACC circuit (15).
a) and the mixing circuit (14) via the APC circuit (16a).
a) to the other input terminal.

In addition, the luminance signal output terminal (4Yb) of the regenerative amplifier circuit (4b)
) is supplied to the demodulation circuit (5b), and the demodulated luminance signal Y obtained at the output side of the demodulation circuit (5i) is sent to the CCD circuit (17y) and the AGC circuit (17y) constituting a variable delay circuit. '3b) through the series circuit of the mixing circuit (
14b). Also, the color signal C obtained at the color signal output terminal (4cb) of this regenerative amplifier circuit (4b) is transferred to a CCD 1 path (17C) constituting a variable delay circuit.
, A CC circuit (15b) and APC circuit (16b)
) to the other input terminal of the mixing circuit (14b). In this case, in the APC circuit (16b), 3,58
A MHz signal is used as a comparison signal, and the phase is matched to this signal.

That is, the color signal C obtained at the output side of the APC circuit (16a)
The phases of the color signal C obtained at the output side of the APC circuit (16b) are made to match.

Further, the clock signal indicates a voltage-controlled variable frequency oscillator that generates a clock signal, and the clock signal obtained at the output side of the voltage-controlled variable frequency oscillator circuit is supplied to the CCD circuits (17y) and (17C), respectively. In this case, the CCD circuit (17
The delay times of y) and (17C) are determined by the frequency of this clock signal. The oscillation frequency of this voltage controlled variable frequency oscillator is determined as follows. That is, the luminance signals Y obtained at the output sides of the demodulation circuits (5a) and (5b) are respectively supplied to the sync separation circuits (19a) and (19b), and the respective sync separation circuits (19a) and (19b) are The horizontal synchronization signal obtained on the output side is supplied to one and the other input terminals of the phase comparison circuit, respectively, to detect the time axis error of the horizontal synchronization signal, and the horizontal synchronization signal obtained on the output side of the phase comparison circuit is A DC voltage corresponding to the time axis error of the equal horizontal synchronization signal is obtained, and the oscillation frequency of this voltage-controlled variable frequency oscillator is controlled by the DC voltage obtained at the output side of this phase comparison circuit (20). To do.

The respective output signals of the mixing circuits (14a) and (14b) are supplied to one and the other fixed reading points (7a) and (7b) of the switch (7), respectively. In addition, the luminance signal Y obtained at the luminance signal output terminals (4Ya) and (4Yb) of the regenerative amplifier circuits (4a) and (4b) is transmitted to the envelope detection circuit (9).
a) and (9b) respectively. The rest of the structure is the same as that shown in FIG.

In this example, for example, when performing a high-speed picture search at 4x speed, the movable contact (7c) of the switch (7) is connected to the outputs of the envelope detection circuits (9a) and (9b), as in FIG. Since the connection is switched to the one with the higher level, the output signal level of the video signal obtained at this movable contact (7C) is always higher than the predetermined level as shown in Figure 8, and the video signal obtained at this movable contact (7C) is the video signal output terminal (8)
Since a video screen of this video signal is obtained, an easy-to-see image without noise bars can be obtained. In addition, in this example, the time axis shift of the horizontal synchronization signal of the luminance signal Y obtained at the output side of the demodulation circuits (5a) and (5b) is corrected by the CCD circuit (17Y). Since the time axis deviation of the color signal C is eliminated by the CCD circuit (17C), the video signal obtained at the switch (force movable contact (7c)) is ideal with H alignment. Vessel (7)
Skew occurs due to switching of the movable contact (7C).

It is possible to obtain an easy-to-see video screen without hue fluctuations.

Also, in the case of other variable speed playback such as slow playback, an easily viewable image can be obtained in the same way.

As described above, according to this example, it is possible to obtain a video screen that does not generate noise bars as described above and also does not generate skew or hue fluctuations during variable speed reproduction such as high-speed picture search.

It goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

Effects of the Invention According to the present invention, it is possible to obtain an easy-to-see video screen that does not generate noise bars and does not have skew or hue fluctuations during variable speed playback such as high-speed picture search.

[Brief explanation of drawings]

Figures 1, 2, 3, and 4 show conventional VTRs, respectively.
Figures 5, 7, and 8 are diagrams for explaining the VTR, Figure 6 is a configuration diagram showing the main parts of an example of a VTR, and Figure 9 is a diagram for explaining the main parts of the VTR. FIG. 7 is a configuration diagram showing an example of a main part of an embodiment of the invention VTR. (la) and (1b) are the main magnetic heads, (2) is the video tape, (3a) and (3b) are the sub magnetic heads, (5a) and (5b) are the demodulation circuits, and (7) is the switch. (8) is an output terminal, (9a) and (9b) are respectively envelope detection circuits, Ql is a comparison circuit, συ is a D-flip-flop circuit, and (19a) and (19b) are synchronous separation circuits, respectively. , (17y) and (17C) are CCDs, respectively.
circuit, (1~ are voltage controlled variable frequency oscillators, (4) is a phase comparator circuit.

Claims (1)

[Claims] A first main magnetic head and a first sub-magnetic head which are arranged close to each other and have different azimuths, and a second main magnetic head and a first sub-magnetic head which are arranged close to each other and have the same azimuth as the first sub-magnetic head.
a main magnetic head and a second sub-magnetic head having the same azimuth as the first main magnetic head. During recording, recording can be performed without a guard band, and during variable speed reproduction, the first main magnetic head A reproduction output signal is obtained by switching the reproduction signal of the head and the reproduction signal of the first sub-magnetic head, and also switching the reproduction signal of the second main magnetic head and the reproduction signal of the second sub-magnetic head. In the video tape recorder, variable delay means is provided to change the time axes of the reproduction signals of the first and second main magnetic heads and the reproduction signals of the first and second sub-magnetic heads before the switching. A videotape recorder characterized in that it is arranged so that the