JPH0153958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helical scan type video tape recorder (hereinafter abbreviated as VTR).

Conventional configurations and their problems In recent years, VTRs have been rapidly developed in the direction of longer recording times, multifunctionality, miniaturization, and cost reduction. As recording times have become longer, in recent years VTRs have become available that allow users to freely select either standard mode (2 hour mode) or long time mode (6 hour mode) to record.
Most of them are. However, when playing back recorded magnetic tapes, especially multi-speed playback, still playback, and slow motion playback, it is possible to play back in long-time mode but not in standard mode, or in both standard mode and long-time playback. Although time mode is possible, several noise bars appear during multi-speed playback, and image blur occurs during frame playback during still playback, making it unsatisfactory.

In addition, by providing two auxiliary magnetic heads (for long time mode) with different azimuth angles near the two main magnetic heads (for standard mode) with different azimuth angles, field still playback without image blur and standard There is a known method for realizing multi-speed playback without noise bars in the mode.

However, in order to realize long-time mode field still playback, the track width of the main magnetic head for standard mode is different. Therefore, when performing multi-speed playback in standard mode, the switching position of the main magnetic head and auxiliary magnetic head differs for each field due to the difference in the output of the playback signal due to the difference in track width, which partially causes image blur in the vertical direction. arise,
The image quality is extremely poor.

Hereinafter, with reference to the drawings, a case will be described in which long-time mode field still playback and noiseless multi-speed playback are performed using two conventional main magnetic heads and two auxiliary magnetic heads.

FIG. 1 is a diagram showing the arrangement of a conventional magnetic head and the configuration of a reproduction signal processing circuit. Figure 2 shows
FIG. 2 is a diagram showing a recording track pattern in a long-time mode, a head locus when field still reproduction is performed, and a diagram showing reproduction signals of each magnetic head at that time. FIG. 3 is a diagram showing a recording track pattern in the standard mode, a head trajectory when triple speed reproduction is performed, and a diagram showing reproduction signals of each magnetic head at that time.

FIG. 1A is a diagram showing the arrangement of magnetic heads, in which the rotary cylinder 1 includes standard mode magnetic heads M1 and M2 with different azimuth angles and track widths, as well as magnetic heads M1 and M2 that are in the same rotational plane as both magnetic heads. In addition, magnetic heads S1 and S for long-time mode are installed near both magnetic heads M1 and M2.
2 is placed. As shown in FIG. 1B, the azimuth angle of the magnetic head S1 placed near the magnetic head M1 is the same as that of the magnetic head M2, and the azimuth angle of the magnetic head S2 placed near the magnetic head M2 is , are the same as the magnetic head M1. The magnetic head M1 for standard mode is the same as the track pitch for standard mode, and M2 is used for field still reproduction in long time mode.
It is narrower than 1. The track widths of the magnetic heads S1 and S2 for the long time mode are the same and are wider than the track pitch for the long time mode.

Each magnetic head has track ends aligned for easy height adjustment. Also, the magnetic head M at the outer periphery of the rotation plane of the magnetic head
1 and the magnetic head S1 and the magnetic head M
2 and the magnetic head S2 is nH, where H is the distance of the horizontal synchronizing signal recorded on the magnetic tape.
(n is a positive integer). In this embodiment, for example, n=2.

The reason why this distance is set to be an integral multiple of H is to prevent the interval between horizontal synchronizing signals from being disturbed due to switching of the magnetic head output signal during reproduction.

Next, the configuration of a conventional example will be explained using FIG. 1C. In FIG. 1C, standard mode magnetic heads M1 and M are installed on the rotary cylinder 1.
2 and magnetic heads S1 and S2 for long time mode.
The reproduced signals M1 and M2 are input to the head amplifier 2, and the signals S1 and S2 are input to the head amplifier 3 via rotary transformers R1, R2, R3 and R4, respectively. Reference numeral 10 denotes an input terminal for a head switching signal synchronized with the rotation of the rotary cylinder 1, which is input to the head amplifiers 2 and 3. These head switching signals select reproduction signals for magnetic heads M1 and M2 and magnetic heads S1 and S2, respectively. The output signal of the head amplifier 2 is input to an envelope detection circuit 5 and a changeover switch 8. Similarly, the output signal of the head amplifier 3 is input to an envelope detection circuit 6 and a changeover switch 8. With the envelope detection circuit 5, the standard mode magnetic head M
The envelope detection circuit 6 performs envelope detection of the reproduction signals of the long-time mode magnetic heads S1 and S2. The output signals of the envelope detection circuits 5 and 6 are input to the minus (-) and plus (+) terminals of the respective comparators 7. The output of the comparator 7 is Low level when the output signal of the envelope detection circuit 5 is larger than the output signal of the envelope detection circuit 6; When it is small, it is at a high level. The output of the comparator 7 is connected to a changeover switch 8, which switches the output of the larger reproduced signal from the standard mode magnetic heads M1 and M2 and the long time mode magnetic heads S1 and S2 to the reproduced signal output terminal 9. Switch 8 is switched.

11 is a mode control signal input terminal, and the mode control signal is input to the envelope detection circuits 5 and 6. This mode control signal controls the outputs of the envelope detection circuits 5 and 6 when envelope comparison is not required, such as normal playback slow mode or still playback. According to
The output of the envelope detection circuit 5 is set to High level, and the output of the envelope detection circuit 6 is set to Low level.

Further, during still playback, the envelope detection circuits 5 and 6 are alternately set to High level and Low level for each field. Therefore, during normal playback, the output of comparator 7 is Low.
level, the selector switch 8 is switched to output the playback signals of the standard mode magnetic heads M1 and M2 to the playback signal output terminal 9, and for still playback,
The output of comparator 7 is High in each field.
and Low, and the changeover switch 8 is switched to output the reproduction signals of the standard mode magnetic head M1 and the long-time mode magnetic head S2 of the same azimuth to the reproduction signal output terminal 9.

For standard playback in long-time mode, similarly switch switch 8 to switch to long-time mode magnetic head S1.
and S2 are output to the playback signal output terminal 9, and for still playback in the long-time mode, the selector switch 8 is switched to select the standard mode magnetic head M2 and the long-time mode magnetic head with the same azimuth for each field. The reproduced signal of S1 is output to the reproduced signal output terminal 9.

Next, in the conventional example configured as shown in FIG.
The operation when performing double-speed playback will be explained using FIGS. 2, 3, and 4.

In FIG. 2, a shows a state in which the recording track patterns recorded by the long-time mode magnetic heads S1 and S2 are repeatedly arranged, one scale on the horizontal axis indicates the time of one field, and at the same time the head switching signal is It also shows timing. The vertical axis indicates the amount of movement of the magnetic tape, and each scale indicates the amount of track pitch that the magnetic tape travels during one field time during recording or normal reproduction. Since azimuth recording is used, tracks recorded by magnetic head S1 cannot be reproduced by magnetic head S2. Similarly, tracks recorded by the magnetic head S2 cannot be reproduced by the magnetic head S1. In FIG. 2a, the tracks recorded by the magnetic head S1 are indicated by R, and the tracks recorded by the magnetic head S2 are indicated by L. Further, the R track can be reproduced with M2 of the standard mode magnetic head, and the L track can be reproduced with M1. The thick lines in Figure 2a represent the head trajectories of S1 and S2 of the long-time mode magnetic head when performing still playback.
The broken lines represent the head trajectories of the standard mode magnetic heads M1 and M2. Figure 2b shows the head switching signal. During the period when the head switching signal is High, reproduction signals are obtained from the magnetic heads M1 and S1, and the head switching signal is high.
During the Low period, reproduction signals are obtained from the magnetic heads M2 and S2. Fig. 2c shows standard mode magnetic heads M1 and M when performing still playback.
This is the playback envelope waveform played in step 2, and the first
This is the output signal of the head amplifier 2 in Figure c.

FIG. 2D shows the reproduced envelope waveform reproduced by the long-time mode magnetic heads S1 and S2,
This is the output signal of the head amplifier 3 of FIG. 1C.

In order to perform still playback with field playback without image blurring, the selector switch 8 is switched so that the S1 playback signal is obtained during the period when the head switching signal is High, and the M2 playback signal is obtained during the period when the head switching signal is Low. The waveform of is obtained at the reproduction signal output terminal 9.

The shaded parts of the reproduced waveforms c, d, and e in Figure 2 indicate the crosstalk components of adjacent tracks, and when the crosstalk components increase relative to the reproduction signal level of the main track, crosstalk noise occurs on the reproduction screen. do. Therefore, the standard mode magnetic head M2 used for long-time mode still playback cannot be made as wide as M1 because of the increased crosstalk components between adjacent heads. The limit of crosstalk level is about -10dB, as shown in Figure 2 c and d.
There is no practical problem if the crosstalk of the reproduced signal of M2 as shown in FIG.

Next, in the case of triple-speed playback in standard mode with such a head configuration, the third
This will be explained using the diagram and FIG.

In FIG. 3, a is the long-time magnetic head M1.
This figure shows a state in which the recording track patterns recorded in M2 and M2 are repeatedly arranged, and as in FIG. The vertical axis indicates the amount of movement of the magnetic tape, and each scale indicates the amount of track pitch that the magnetic tape travels during one field time during recording or normal reproduction. Since it is azimuth recording, the magnetic head M1
Tracks recorded by the magnetic head M2 cannot be reproduced by the magnetic head M2. Similarly, tracks recorded by the magnetic head M2 cannot be reproduced by the magnetic head M2. In Fig. 3a, the magnetic head M
The track recorded by magnetic head M2 is indicated by L, and the track recorded by magnetic head M2 is indicated by R. Further, the R track can be reproduced by the long-time mode magnetic head S1, and the L track can be reproduced by S2. The thick lines in Figure 3a represent the head trajectories of the standard mode magnetic heads M1 and M2 during triple speed reproduction, and the broken lines represent the head trajectories of the long time mode magnetic heads S1 and S2. . b is a head switching signal. Magnetic heads M1 and M2 for standard mode when c performs triple speed playback
d is the reproduced envelope waveform reproduced by the long-time mode magnetic heads S1 and S2, and d is the output signal of the head amplifier 2 in FIG. It's a signal. The reproduced envelope waveforms shown in FIGS. 3c and d are passed through the envelope detection circuits 5 and 6 shown in FIG. The reproduced signal shown in FIG. 3e is obtained at the output terminal 9.
As a result, a good reproduced image without noise bars can be obtained during triple-speed reproduction in the standard mode. Note that the reproduction envelope waveforms c, d, and
The line extending between and e indicates the switching position based on envelope comparison.

As shown in FIG. 3, since the track widths of the standard mode magnetic heads M1 and M2 are different, the switching positions determined by envelope comparison are different between the period when the head switching signal is High and the period when it is Low.
For this reason, four switching lines appear on the playback screen, and between two of the lines, there is a partial vertical shift in the playback image, which significantly reduces the playback image quality.

This situation will be explained using FIG. 4. Figure 4a
shows the track patterns recorded with magnetic heads M1 and M2 for standard mode, 50 and 5
2 is a track recorded by the magnetic head M1, and 51 is a track pattern recorded by the magnetic head M2. Recording tracks 50, 51 and 52 are labeled with horizontal synchronization signal numbers. As is well known, in the case of standard mode recording, horizontal synchronizing signals are recorded so that they line up with adjacent tracks with a horizontal synchronizing signal difference of, for example, 1.5H. Also, since one field signal is recorded on one track and one frame signal is recorded on two tracks, the first track records the 1H to 262.5H, and the second track records the 262.5H to 525H. However, almost the same information is recorded for 1H and 263H, so for convenience of explanation,
The same number was given. The initial position for switching from the standard mode magnetic head M1 to the long-time mode magnetic head S1 during the period when the head switching signal is High during triple-speed playback in FIG. 3 is set to A in FIG. 4a.
For example, it is assumed that the 8th H of recording track 50 has finished being reproduced. The distance between the magnetic head caps of the standard mode magnetic head M1 and the long time mode magnetic head S1 is nH as described above, and in this embodiment it is 2H, and the magnetic head S1 rotates in advance of the magnetic head M1. Suppose you are doing so. Therefore, if the magnetic head M1 is switched to the magnetic head S1 at position A in FIG. 4a, the horizontal synchronizing signal number of the reproduced signal will be as shown at 53 in FIG. 4b.

Next, while the head switching signal is Low, the first position at which the standard mode magnetic head M2 is switched to the long time mode magnetic head S2 is set to position B in FIG. When the playback is finished. Similarly, magnetic head M
It is assumed that the magnetic head S2 is rotating in advance of the magnetic head S2. Therefore, at this time, the horizontal synchronization signal number of the reproduced signal is as shown at 54 in FIG. 4b.

53 in FIG. 4b is a reproduction signal of the first field, 54 is a reproduction signal of the second field,
These two make up one frame of a reproduced image. The biggest problem with these reproduced signals 53 and 54 is the period between switching positions A and B, where the horizontal synchronization signal numbers of the reproduced signal 53 are 5, 6, 7, and 8, and the next field is The horizontal synchronization signal numbers of the playback signal 54 are 9, 10, 11, and 12, each shifted by 4H, and during this period, the information in the first field and the second field are significantly different, so there is a vertical shift on the playback screen. It was very difficult to see.

Note that Figure 4 is for explaining the problem in principle; in the triple speed playback shown in Figure 3, the difference between the switching positions of the first field and the second field is approximately 1.3 msec, which is approximately 20H. During the corresponding period, vertical jitter occurs on the playback screen.

As explained above, in the past, the standard mode magnetic head and the long-time mode magnetic head were installed close to each other, and in order to realize long-time mode field still playback, the track width of one side of the standard mode magnetic head was increased. When performing multi-speed playback in standard mode on a video tape recorder configured to narrow the screen, no noise bar will appear on the playback screen, but there will be some vertical wobble, resulting in good multi-speed playback. The problem was that it could not be done.

Similar problems occur even at speeds n times higher than speeds other than triple speeds. For example, at 9x speed,
The width of the vertical jitter is about 7H, which is 1/3 of the 3x speed, but it occurs in three places on the playback screen, and the total is about 20H, the same as in the case of the 3x speed.

OBJECTS OF THE INVENTION An object of the present invention is to provide a video tape recorder that provides good playback images during multi-speed playback.

Composition of the Invention The video tape recorder of the present invention allows a magnetic tape to run at a constant speed at a predetermined first or second speed (however, the first speed>second speed) during recording, and azimuthally first and second magnetic heads with different angles are provided at 180° positions on the rotating substrate, and a third magnetic head with an azimuth angle different from that of the first magnetic head and the same as that of the second magnetic head; The fourth magnetic head has an azimuth angle different from that of the second magnetic head and the same as that of the first magnetic head.
magnetic heads are provided at positions 180° of the rotary head substrate near the first and second magnetic heads, respectively, and when recording is performed at the first speed,
When recording at the second speed using the first and second magnetic heads, the helical scan video tape recorder is configured to use the third and fourth magnetic heads, The track widths of the first and second magnetic heads are the same,
The track widths of the third and fourth magnetic heads are the same, and the track width TW1 of the first and second magnetic heads is wider than the track width TW2 of the third and fourth magnetic heads. The track pitch of the second speed is TP2, the track pitch of the first speed is TP1=3×TP2, 2×TP2≦TW1≦3×TP2 TP2≦TW2≦2×TP2, and the first and second magnetic heads The track width centers of the third and fourth magnetic heads are arranged to be aligned with each other, and as a result, there is no difference in the switching position of each field on the playback screen during multi-speed playback. It is possible to eliminate vertical play.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 5 is a diagram showing the arrangement of magnetic heads in one embodiment of the present invention. Note that the same components as in FIG. 1 are given the same reference numerals. In FIG. 5, A is a diagram showing the arrangement of the magnetic heads. In addition to standard mode magnetic heads M1 and M2 with different azimuth angles, the rotary cylinder 1 has a first magnetic head.
The long-time mode magnetic heads S1 and S2 are arranged as in FIG. A.

As shown in Figure 1B, magnetic heads M1 and 2 for standard mode and magnetic head S for long time mode.
The relative heights of heads 1 and S2 are set so that the centers of the track widths are aligned, and the track width is set so that the track pitch in long-time mode is TP2.The track width of the magnetic head for standard mode is 2 x TP2, and the track width in long-time mode is The track width of the magnetic head for
It is set as TP2. The block diagram of the reproduced signal processing system is the same as that shown in FIG. 1C.

Magnetic heads M1 and M2 are 180° apart from each other. Magnetic heads S1 and S2 are also 180° apart from each other.

Furthermore, the distance between the magnetic heads M1 and the magnetic heads S2 on the outer periphery of the rotation plane of the magnetic heads, and
The distance between the magnetic heads M2 and S2 is nH (n is a positive integer), where H is the distance between horizontal synchronizing signals recorded on the magnetic tape. The reason why this distance is set to be an integral multiple of H is to prevent the interval between horizontal synchronizing signals from being disturbed due to switching of the output signal of the magnetic head during reproduction.

Next, an explanation will be given of the operation in this embodiment when triple speed playback in the standard mode is performed with reference to FIG. In FIG. 6, a shows a state in which the recording track pattern recorded by the standard mode magnetic heads M1 and M2 is repeatedly arranged, one scale on the horizontal axis indicates the time of one field, and at the same time the timing of the head switching signal is shown. Also shown. The vertical axis indicates the amount of movement of the magnetic tape, and each scale indicates the amount of track pitch that the magnetic tape travels during one field time during recording or normal reproduction. Since azimuth recording is used, tracks recorded by magnetic head M1 cannot be reproduced by magnetic head M2. Similarly, tracks recorded by the magnetic head M2 cannot be reproduced by the magnetic head M1. In FIG. 6a, the tracks recorded by the magnetic head M1 are indicated by L, and the tracks recorded by the magnetic head M2 are indicated by R. Also, the R track is the long-time mode magnetic head S1, and the L track is S2.
can be played with. The thick line in Figure 6a shows the standard mode magnetic head M when performing triple speed playback.
1 and M2, and the dashed line represents the head trajectory of long-time mode magnetic heads S1 and S2. b is a head switching signal. c is the reproduction envelope waveform reproduced by the standard mode magnetic heads M1 and M2 during triple speed reproduction, and is the output signal of the head amplifier 2 in FIG. 1C. d is the reproduced envelope waveform reproduced by the long-time mode magnetic heads S1 and S2, and is the output signal of the head amplifier 3 in FIG. 1C.

The reproduced envelope waveforms shown in FIGS. 6c and 6d are passed through envelope detection circuits 5 and 6, which are, for example, well-known diode detection circuits shown in FIG. 1C, for envelope comparison by a comparator 7. By switching the changeover switch 8, the playback signal output terminal 9
The reproduced signal shown in FIG. 6e is obtained. As a result, in this embodiment as well, a good reproduced image without noise bars is obtained during triple speed reproduction in the standard mode. Note that the reproduction envelope waveforms c, d, and
The line extending between and e indicates the switching position based on envelope comparison.

As shown in Figure 6, the standard mode magnetic head M
Since the track widths of 1 and M2 are the same, the reproduced signal waveforms reproduced during the high and low periods of the head switching signal are the same, and the switching positions based on the envelope comparison are also approximately the same.

Since the switching positions of the first field and the second field are the same, there is no vertical shift in the reproduced image due to the difference in switching positions, and the four switching lines become two visually, resulting in a significant improvement in image quality. It can be measured.

As described above, according to this embodiment, by making the standard mode magnetic heads M1 and M2 the same track width and making the long mode magnetic heads S1 and S2 the same track width, reproduction during multi-speed reproduction is achieved. To make the signal switching position the same for a first field and a second field, to eliminate partial vertical wobble in a playback screen, and to visually reduce the number of switching signals to half that of the conventional method to obtain a good playback image. Can be done. In this embodiment, the track width of the standard mode magnetic heads M1 and M2 is twice the track pitch TP2 of the long time mode. Even if M2 is not made wider than M2, it is possible to obtain a good reproduced image without noise bars occurring at the switching point of the reproduction signal in standard mode multi-speed reproduction. Note that the track widths of the standard mode magnetic heads M1 and M2 are determined by the crosstalk noise level of adjacent tracks when used for still playback in the long time mode, so they cannot be made very wide. By aligning the centers of the widths, the head can be made much wider than the standard mode magnetic head used for long-time mode still playback in the conventional configuration. Therefore, it is possible to obtain a field still reproduction image comparable to the conventional one and a multi-speed reproduction image which is significantly improved than the conventional one.

Effects of the Invention As is clear from the above description, the present invention is a helical scan type video tape recorder in which a magnetic head for standard mode and a magnetic head for long time mode are installed, and the centers of their respective track widths are aligned. Magnetic heads M1 and M for standard mode
By making the track widths of the two magnetic heads the same and the track widths of the long-time mode magnetic heads the same, the reproduced signal waveforms of the first field and the second field can be made the same, and the partial portions that occur during multi-speed reproduction can be suppressed. By eliminating vertical play and halving the number of playback signal switching lines, it is possible to obtain good multi-speed playback images. Furthermore, by correcting the difference in the horizontal synchronization signal when switching the reproduction signal using a delay line, a high-quality multi-speed reproduction image without noise or skew can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing the arrangement of the head structure and the playback signal processing system of a conventional video tape recorder; FIG. 3
The figure is a diagram for explaining 3x playback in standard mode in the conventional example shown in Figure 1, and Figure 4 is a diagram for explaining the occurrence of partial vertical play during multi-speed playback in the conventional example shown in Figure 1. 5 is a diagram showing an example of the arrangement of the head structure in the video tape recorder of the present invention, and FIG. 6 is a diagram for explaining triple speed playback in standard time mode in the embodiment of the present invention. M1, M2...Magnetic head for standard mode, S
1, S2... Magnetic head for long time mode, 1...
Rotating cylinder, 2, 3...Head amplifier, 5, 6
... Envelope detection circuit, 7 ... Comparator, 8 ... Selector switch.

Claims (1)

[Claims] 1. The magnetic tape is moved at a predetermined first or second speed during recording (however, the first speed>the second speed)
The first and second magnetic heads, which have different azimuth angles, are mounted on a rotating board.
180°, and the azimuth angle is the first
a third magnetic head that is different from the second magnetic head and the same as the second magnetic head; and a fourth magnetic head that has an azimuth angle that is different from the second magnetic head and is the same as the first magnetic head. When a rotary head is provided near the first and second magnetic heads at a position of 180 degrees on the rotary head substrate and when recording is performed at the first speed, the first and second magnetic heads are used, and the second magnetic head is When recording at high speed, the helical scan video tape recorder is configured to use the third and fourth magnetic heads, and the track widths of the first and second magnetic heads are the same; The track widths of the third and fourth magnetic heads are the same, and the track width TW1 of the first and second magnetic heads is wider than the track width TW2 of the third and fourth magnetic heads;
And the track pitch of the first speed is TP1, and the track pitch of the second speed is TP1.
The track pitch of the first speed is TP2, the track pitch of the first speed is TP1=3×TP2, 2×TP2≦TW1≦3×TP2 TP2≦TW2≦2×TP2, and the first and second magnetic heads A video tape recorder characterized in that the third and fourth magnetic heads are installed so that their track width centers are aligned.