JPS6322512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus capable of special (variable speed) reproduction, such as a rotating head type azimuth recording type video tape recorder.

In recent years, there has been an increasing demand for a special (variable speed) playback function that allows video signal magnetic recording and playback devices or video signal magnetic playback devices that use magnetic tape, such as video tape recorders, to play back at a different tape speed than when recording. ing. For still playback or slow playback, a method has been proposed in which the running of the magnetic tape is controlled so that the portion where the playback head output decreases is the vertical retrace period. It has been put into practical use. However, no device has been proposed that realizes high-speed playback or reverse high-speed playback, which is one of the special (variable speed) playback functions, without noise bars.

The present invention uses an auxiliary rotary head and selects its azimuth angle and rotation plane to compensate for the drop in the reproduction output signal of the main rotary head that occurs during high-speed reproduction or reverse high-speed reproduction, and provides high-speed reproduction without noise bars. Alternatively, it enables reverse high-speed reproduction.

The present invention can also compensate for a decrease in the playback output of the main rotary head that occurs during slow playback and still playback.

In the present invention, since the timing for supplementing with the reproduction output signal of the auxiliary rotary head is synchronized with the horizontal synchronization signal, noise at the time of switching does not appear on the screen.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a diagram showing the main part of an embodiment of the present invention, and FIG. 2 shows an example of a track pattern of a magnetic tape recorded azimuthally. In FIG. 1, M1 is the main rotating head with an azimuth angle of +6 degrees and S1 is the auxiliary rotating head with an azimuth angle of -6 degrees. M2 is another main rotating head with an azimuth angle of -6 degrees, and S2 is another auxiliary rotating head with an azimuth angle of +6 degrees. The main rotating heads M1 and M2 are 180° apart from each other.
The auxiliary rotary heads S1 and S2 are also 180° apart from each other. These main rotating heads and auxiliary rotating heads are
For example, as shown in FIG. 1, they are mounted on a rotary disk (or drum) 3 on the same rotation plane at a distance corresponding to two horizontal synchronizing signal periods of the video signal. Rotating disk 3 is rotating shaft 4
in the direction of arrow 9 by motor 5 through
It can be rotated at a rotation speed of 1800rpm. The magnetic tape 6 is guided by guide posts 7 and 8, wrapped around the rotary disk 3 over 180 degrees, and is run in the direction of arrow 10 by a pinch roller 11 and a capstan 12. A schematic track pattern of the magnetic tape 6 is shown in FIG. In Figure 2, track 99,1
01, 103, 105, 107 and 109 are +
recorded with a rotating head with an azimuth angle of 6°,
Truck 100, 102, 104, 106, 10
8 and 110 are tracks recorded with a rotating head having an azimuth angle of -6°.

The diagonal lines in each track in FIG. 2 indicate the horizontal synchronizing signal recording position, and the inclination angle thereof indicates the azimuth angle. (Diagonal lines are omitted in the widthwise central part of the magnetic tape 6.) Figure 2 shows the case where the magnetic tape 6 is running at 1x speed (same as the tape speed during recording). It shows the track pattern. Therefore, when the main rotary head M1 scans the start point of the track 101 at the field start point during 1x speed reproduction, it scans the end point of the track 101 at the end of the field. As an example of high-speed playback, when playing at 9x speed,
When the main rotating head M1 is at the field start point,
If the starting point of track 101 is scanned, then at the end of the field, the ending point of track 109 is scanned. The auxiliary head S1 has the same rotational plane as the main rotating head M1, and is mounted close to the main rotating head M1 (in this embodiment, separated by a distance corresponding to two horizontal synchronizing signal periods of the video signal). Therefore, almost the same scanning as that of the main rotating head M1 is performed. During such 9x speed playback,
Since the main rotating head M1 has an azimuth angle of +6 DEG, a head output signal as shown in FIG. 3a is obtained. Further, since the auxiliary rotary head S1 has an azimuth angle of -6°, a head output signal as shown in FIG. 3b is obtained. Typically, these head output signals consist of an FM modulated luminance signal with a carrier frequency of approximately 3.9 MHz and a carrier chrominance signal that is downconverted to a chrominance subcarrier frequency of approximately 629 MHz. The time scale is shown in Figure 3i. this is,
t ₀ indicates the field start time, and t ₅ indicates the field end time. A drawback of the conventional example is that several noise bars (portions where the head output signal is zero) appear within the field during high-speed reproduction as shown in FIG. 3a. The present invention compensates for such a decrease in the reproduction head output of the main rotary head M1 with the reproduction head output signal of the auxiliary rotary head S1 as shown in FIG. 3b, as shown in FIG. 3c. This allows you to get a high-speed playback screen without noise bars.

FIG. 4 shows a block diagram of an embodiment of the present invention which can compensate for the above-mentioned drop in playback head output and provide a high-speed playback screen free of noise bars. In FIG. 4, the same components as those explained in FIG. 1 are given the same reference numerals. The output signal of the main rotary head M1 is amplified by a preamplifier 51 and supplied to a gate circuit 52 and an amplitude detector 53. The output signal of the gate circuit 52 is sent to the adder 5
4. The output signal of amplitude detector 53 is supplied to the negative input terminal of comparator 55. The output signal of the auxiliary rotary head S1 is amplified by a preamplifier 56 and supplied to a gate circuit 57 and an amplitude detector 58. The output signal of the gate circuit 57 is supplied to the adder 54. The output signal of adder 54 is supplied to switch circuit 59. The output signal of amplitude detector 58 is supplied to the positive input terminal of comparator 55. The output signal of comparator 55 is supplied to the D input terminal of D-type flip-flop circuit 60. The above flip-flop circuit 6
Horizontal synchronization signal separation circuit 61 is connected to the 0 CP input terminal.
output signal is provided. Further, the output signal of the Q output terminal of the flip-flop circuit 60 is supplied to the gate control terminal of the gate circuit 52, and is also applied to the switch rotation 62 so as to control its movable piece. The output signal of the output terminal is supplied to the gate control terminal of the gate circuit 57. The output signals of the main rotary head M2 and the auxiliary rotary head S2 have similar circuit configurations, namely, preamplifiers 71, 76, gate circuits 72, 77, amplitude detectors 73, 78, comparator 75, D-type flip-flop circuit 79, and adder. The same processing is performed in the device 74. The output signal of the adder 74 is supplied to the switch circuit 59. The output signal of the switch circuit 59 is supplied to the horizontal synchronizing signal separation circuit 61, the switch circuit 62 and the delay line 64 via a video signal demodulator 63. The output signal of the switch circuit 42 is supplied to an output terminal 65.

Next, the operation of this embodiment will be explained with reference to the waveform diagram in FIG. First, if a head output signal as shown in FIG. 3a is output from the preamplifier 51, an envelope signal as shown in FIG. 3d is output from the amplitude detector 53. Note that the amplitude detector 53 is composed of, for example, a well-known diode detection circuit. Similarly, if a head output signal as shown in FIG. 3b is output from preamplifier 56, an envelope signal as shown in FIG. 3e is output from amplitude detector 58. The amplitude detector 58 has the same configuration as the amplitude detector 53. These envelope signals are compared in level by a comparator 55 and input to a D-type flip-flop circuit 60. CP of D-type flip-flop circuit 60
The terminal receives the regenerated horizontal synchronization signal (described later).
is input, so the Q output terminal is shown as f in Figure 3.
An output signal of the comparator 55 synchronized with the horizontal synchronizing signal as shown in FIG. In FIG. 3f, the H level indicates that the output level of the auxiliary rotary head S1 is higher than the output level of the main rotary head M1, and the L level indicates that the output level of the main rotary head M1 is higher than that of the auxiliary rotary head S1. Indicates that the level is higher than the output level. A signal of opposite polarity to the Q output terminal is obtained at the output terminal. By controlling the gate circuit 52 with respect to the output signal of the Q output terminal, an output signal of only the high level portion of the main rotary head M1 as shown in FIG. 3g is obtained at the output terminal of the gate circuit 52. Similarly, by controlling the gate circuit 57 with respect to the output signal of the output terminal, the output terminal of the gate circuit 57 receives the output signal of the auxiliary rotary head S1 of only the high level portion as shown in FIG. 3h. It will be done. The gate circuits 52 and 57 are constituted by well-known analog gate circuits using, for example, field effect transistors.

By adding the signals shown in FIGS. 3g and 3h in the adder 54, as shown in FIG. A head output signal corresponding to the field can be obtained. Since this complementary period is timed with a horizontal synchronizing signal using the D-type flip-flop circuit 60, switching noise does not occur in the reproduced image. In this field, the movable part of the switch circuit 59 is tilted toward the adder 54, so the output signal of the adder 54 is supplied to the video signal demodulator 63 via the switch circuit 59 and converted into a video signal. . This video signal demodulator 63, as is well known,
It consists of a luminance signal demodulation system and a carrier color signal demodulation system. The luminance signal demodulation system demodulates the FM-modulated luminance signal, and the carrier color signal demodulation system removes jitter from the reproduced low-frequency converted carrier color signal to produce a carrier color signal with a color subcarrier frequency of approximately 3.579545MHz. Convert. The video signal demodulated in this manner is supplied to a horizontal synchronizing signal separation circuit 61, a delay line 64, and a switch circuit 62. The horizontal synchronization signal is separated and extracted by the horizontal synchronization signal separation circuit 61. delay line 6
4, the auxiliary rotary head S1 and the main rotary head M1
The video signal is delayed by a time difference (in this embodiment, a time equivalent to two horizontal synchronizing signals). As the delay line 64, a glass delay line or a semiconductor delay line using a semiconductor such as a CCD is used to delay the video signal with a low distortion rate. In particular, in order to accurately correct the time difference between the auxiliary rotary head S1 and the main rotary head M1, it is desirable to use a semiconductor delay line whose delay time can be easily adjusted. Since the main rotary head M1 reproduces the track in advance of the auxiliary rotary head S1 by a time equivalent to two horizontal synchronizing signals, when the Q output signal of the D-type flip-flop circuit 60 is at H level, the switch circuit 62 The movable piece of the delay line 64
When the movable piece is at the L level, the movable piece is moved toward the video signal demodulator 63 side. As a result, a video signal from which the time difference between the auxiliary rotary head S1 and the main rotary head M1 described above has been removed is outputted to the output terminal 65.
In the next field, the output signal of the main rotary head M2 and the output signal of the auxiliary rotary head S2 are processed in the same process as described above, and the switch circuit 59
By tilting the movable piece toward the adder 74 side, a reproduced video signal without noise bars can be continuously obtained at the output terminal 65.

Thus, by using the auxiliary rotary head and selecting its azimuth angle and plane of rotation, it is possible to compensate for the drop in the reproduction output signal of the main rotary head that occurs during high-speed reproduction. As a result, a high-speed playback screen without noise bars is obtained.

During reverse high-speed reproduction, the scanning loci of the main rotary head and the auxiliary rotary head with respect to the magnetic tape 6 are different from those described above, but are shown in FIGS. 3a and 3b.
The output signal of the main rotary head and the output signal of the auxiliary rotary head have a similar relationship as shown in (i.e., the time of the point indicating the maximum output level and the time of the point indicating the minimum output level almost match). Therefore, with the circuit configuration as illustrated in FIG. 4, a reverse high-speed reproduction screen without noise bars can be obtained.

Even during slow playback or still playback, the output signal level of the auxiliary rotary head is complementary to the output signal level of the main rotary head, just like during high-speed playback, so it is possible to prevent the output signal level of the main rotary head from decreasing. By supplementing with the output signal of the auxiliary rotary head, it is possible to obtain a slow playback image or a still playback image without noise bars.

Further, according to the present invention, the reproduction output signal of the auxiliary rotary head is supplemented at a timing synchronized with the horizontal synchronizing signal, so that no noise appears on the screen at the time of switching. Incidentally, if the above-mentioned switching can be performed at high speed, or if some noise can be allowed to occur on the screen at the time of switching, the D-type flip-flop circuits 60 and 79 in FIG. 4 are unnecessary.

In addition, although the above explanation assumes that the rotating heads M1, M2, S1, and S2 are attached to the same rotating plane, the rotation of the auxiliary rotating heads S1 and S2 is different from the rotating plane of the main rotating heads M1 and M2. Almost the same effect can be obtained even if the plane is set to a rotating plane that is an even number times the track pitch.

Further, in the above explanation, it is assumed that the track width of the recording track and the track width of the rotary heads M1, M2, S1 and S2 are almost the same, but the head widths of the auxiliary rotary heads S1 and S2 are the same as those of the main rotary head M1,
Even if the head width is wider than M2, almost the same effect can be obtained. Especially when a guard band is provided between recording tracks, a wide head is advantageous in terms of reproduction output level.

[Brief explanation of the drawing]

Fig. 1 is a main part configuration diagram of an embodiment of the present invention, Fig. 2
The figure shows an example of a track pattern of a magnetic tape recorded azimuthally.
d, e, f, g, h, and i are time charts of signals in the embodiment of the present invention, and FIG. 4 is a block circuit diagram of the embodiment of the present invention. M1, M2...Main rotating head, S1, S2...
Auxiliary rotating head, 3... Rotating disk, 6... Magnetic tape, 52, 57, 72, 77... Gate circuit, 53, 58, 73, 78... Amplitude detector, 5
5, 75... Comparator, 54, 74... Adder, 60, 79... D-type flip-flop, 59
...Switch circuit, 61...Horizontal synchronizing signal separation circuit, 62...Switch circuit, 64...Delay line.

Claims (1)

[Scope of Claims] 1. A magnetic recording and reproducing device that has first and second main rotating heads with different azimuth angles, and that reproduces a magnetic tape by running it at a running speed different from the running speed during recording. The apparatus is characterized in that an auxiliary rotary head is provided, and the period in which the reproduced output signal of the main rotary head decreases is compensated by the reproduced output signal of the auxiliary rotary head in units of horizontal synchronization periods. magnetic recording and reproducing device. 2. In the statement of claim 1, the auxiliary rotating head is arranged in the same rotational plane as the main rotating head or with respect to the rotational plane of the rotating head,
mounted close to the main rotating head on a rotating plane spaced apart by an even number of track pitches;
and the azimuth angle of the auxiliary rotating head is approximately
A magnetic recording/reproducing device characterized in that the azimuth angle is the same as that of another main rotating head 180° apart. 3. A magnetic recording and reproducing apparatus as set forth in claim 1 or 2, characterized in that the magnetic tape traveling speed during reproduction is in the same direction or in the opposite direction to that during recording, and is several times or more higher. 4. A magnetic recording and reproducing apparatus according to claim 1 or 2, characterized in that the head width of the auxiliary rotary head is wider than the head width of the main rotary head. 5. In the statement of claim 1 or 2, the timing for supplementing with the reproduction output signal of the auxiliary rotary head during a period in which the reproduction output signal of the main rotary head has decreased is started by a horizontal synchronization signal. hand,
A magnetic recording/reproducing device characterized in that completion is completed with a horizontal synchronization signal. 6. In claim 1 or 2, it is provided that a delay line is used to compensate for a timing deviation of the reproduction output signal of the auxiliary head with respect to the reproduction output signal of the main rotary head. Features of magnetic recording and reproducing device.