JPS61196406A - Recording device of broad band signal - Google Patents

Abstract

PURPOSE:To prevent the appearance of switching point of tracks as noise on a reproduced picture by (n) dividing an inputted broad band signal, and time axis elongating it and recording and reproducing almost simultaneously. CONSTITUTION:Two heads 11A and 11B are placed at positions of rotational angle close to each other, and at the same time, deviated in the direction of height by a distance (y). The heads 11A, 11B are rotated at a speed twice that of conventional family VTR, that is, one rotation per field. A tape 2 is wound on a guide drum 13 obliquely over angle range of 270 deg.. Video signals for one field divided by time into two is time axis elongated to 270 deg. by rotary heads 11A and 11B. Recording tracks Ta, Tb are formed simultaneously, and video signals for one field are recorded successively as a pair of tracks Ta, Tb.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for recording wideband signals such as video signals of high-definition television broadcasting.

[Summary of the invention]

In this invention, a tape is wound around a drum over an angular range larger than 180°, and a broadband signal corresponding to one rotation time divided into n pieces is transmitted over the tape winding angle by a plurality of rotary heads provided at approximately the same rotational angular position. The time axis is converted to n tracks at the same time, and it is recorded on almost all n tracks at the same time.
This allows wideband signals to be recorded without changing the diameter of the R head drum.

[Conventional technology]

If you try to record a wideband signal with a baseband of as much as 8MHz on a conventional home VTR, the baseband band that can be recorded on the current home VTR is about 2 to 3M.
Since the frequency is as narrow as Hz, the high frequency side of the wideband signal can hardly be recorded or reproduced, and the S/N ratio will be extremely degraded, making it impractical.

Therefore, it is necessary to create a new VTR that can record this wideband signal. In this case, if the diameter of the head drum is increased, even if the tape is wound around the drum by the same angle as before, the part of the tape that is wound around the head drum will be longer, and the recording wavelength will be lengthened accordingly, resulting in a wide band. It becomes possible to record signals. However, it would be necessary to develop a new large-sized hent drum, and the cost and changes to the equipment cannot be ignored.

In this regard, it would be convenient if a VTR for recording wideband signals could be realized without changing the diameter of the head drum, which has been conventionally used as a rotary head device for household VTRs.

Against this background, the following methods can be considered to enable the recording of wideband signals.

That is, FIG. 7 is a schematic diagram of the rotary head device, in which the rotary heads are arranged at angular intervals of 180° as in the conventional case, and the tape (2) is spread over an angular range of 180° with respect to the guide drum. Wrap it around. The number of rotations of the rotary head is increased to twice that of the conventional one, that is, the number of rotations is increased to one rotation per 1 field.

When a video signal is recorded using this rotary head device and a drum phase servo is applied so that the vertical synchronization signal of the video signal is recorded at the part where the head (IA) starts to come into contact with the tape (2), the video signal is sequentially supplied to the rotating heads (IA) and (IB) every 1/2 field, and the tape (
2) The track TA is rotated by the rotating head (IA) on the
Trunks TB are sequentially formed by a rotating head (IB) and video signals are recorded thereon.

Therefore, each track TA and TB has a
The video signal for 1/2 field is recorded, and the signal for one field is recorded on these two trunks. Conventionally, the signal for one field was recorded on one track. If you look at each trunk, the recording wavelength will be twice as long as compared to the case where the recording wavelength is doubled. therefore,
The baseband band that can be recorded as each track becomes wider, making it possible to record wideband signals.

[Problem that the invention seeks to solve]

However, when recording in this way, the information on the upper half of the screen will be recorded on track TA, and the information on the lower half of the screen will be recorded on track TB.
The signals from the TB and TB are switched every 1/2 field and taken out from the two rotating heads during playback, so the playback screen is the upper half of the screen (3A) above the track TA as shown in Figure 9. The lower half of the screen from the trunk TB (
The joint with tape (2B) appears as noise on the screen due to head switch switching, making it unsightly.
), the gains of the reproduction signals from both tracks TA and TB are different,
For this reason, there is a drawback that the brightness differs between the upper half screen (3A) and the lower half screen (3B) shown in FIG. 9.

In addition, tracks TA and TB each record information on the upper half and lower half of the screen of one field, so two
When playing back at variable speeds such as double speed, triple speed, and five times speed, it is very difficult to extract a picture as it is, so in addition to the two heads (IA) and (IB), an additional head for variable speed playback is required. It becomes necessary to take special measures, such as providing a

[Means for solving problems]

This invention provides n (n is an integer of 2 or more) rotating heads that are located close to each other and offset from each other in the height direction, and that
The tape is wound diagonally over an angular range greater than 0°, and the input broadband signal is divided along the time axis into n signals for each rotation of the rotating head, and each of the n outputs of the divided signals are A time axis converting circuit for converting the time axis into a time corresponding to the tape winding angle is provided, and the output of this time axis converting circuit is supplied to each of the n rotary heads.

[Effect]

Each of the n rotary heads divides the wideband signal into n parts, and records each divided signal, which is timed by the tape winding angle, almost simultaneously as n tracks on the tape. In other words, the signal for one rotation of the rotary head is compressed in time to the time for the tape winding angle, but
At this time, the data will be sequentially recorded as n tracks, and the signal of each track will be in a state where the time axis has been expanded. Therefore, the recording of wideband signals is
This can be done without changing the diameter of the TR head drum.

Moreover, in this case, each divided signal is recorded and played back at the same time, so there is no need to switch the head output. However, there are no drawbacks such as switch noise at the joints.

〔Example〕

FIG. 1 shows an example of a rotary head device used in the device of the present invention. In this example, two heads (11^) and (IIB) are arranged at rotational angle positions close to each other, and As shown in FIG. 2, the rotating heads (11^) and (IIB) are also arranged to be shifted by a distance y in the height direction. In addition, in reality, these two rotating heads (IIA
) and (IIB) in the height direction is problematic due to leakage magnetic flux, so they are also arranged apart by X in the rotational direction, as shown in FIG.

Here, when comparing so as to form a guard band between adjacent tracks, the distance My is head (IIA) (IIB)
For the gap width g, let y>g, and both heads (11^
) (11B) may be heads with the same azimuth angle.On the other hand, when recording at high density so as not to form guard bands between adjacent tracks, the head should be 15g, and both heads (II
A) and (11B) have different azimuth angles.

Then, this head (11^) (11B) is rotated at twice the rotation speed of a conventional home VTR, that is, one rotation per 1 field.

In addition, the tape (2) is 27 mm with respect to the guide drum (13).
Wrap diagonally over the 0° angle range.

Then, the video signal for one field is temporally divided into two by the rotating heads (IIA) and (IIB) (the actual time length of each divided signal is 180 degrees), which is 270 degrees.
The time axis is expanded to minutes, and as shown in FIG.
a and Tb are simultaneously formed, and the video signal for one field is sequentially recorded as a pair of tracks Ta and Tb.

Figure 4 shows an example of the recording system, where a wideband video signal through an input terminal (21) is converted into a digital signal by an A/D converter (22), and this digital signal is supplied to a channel division circuit (23). . In this channel division circuit (23), signals are alternately distributed to the first output terminal and the second output terminal, for example, every l horizontal period. Therefore, the digital video signal of the odd-numbered horizontal line is obtained at the first output terminal, and this is transmitted to the time axis expansion circuit (24
A), and a digital video output of even-numbered horizontal lines is obtained at the second output terminal, and this is supplied to the 0 time axis expansion circuit (24B), which is supplied to the time axis expansion circuit (24B).
4A) and (24B), the digital video signal is transmitted 270° for each rotation of the rotary head, that is, for each l field.
The time axis is expanded to minutes.

And these time axis expansion circuits (24^) (24B
) The expanded video signal from the D/A converter (25
＾) and (25B) respectively, are returned to analog signals, and are sent to the FMlii circuits (26＾) and (26B).
After F Iflli at each, the amplifier (27^
) and (27B), head (11^) and (I
IB) and are recorded on the tape by forming tracks Ta and Tb almost simultaneously as shown in FIG.

In this case, the signal of the time axis compression circuit (24A) is supplied to the D/A converter (25^) through the delay circuit (28), but this delay circuit (28) is connected to the head (IIA). This is to compensate for the amount of deviation X in the angular range of the head (IIB) in the rotational direction.

In this way, the input broadband signal is sequentially recorded for each field as two tracks Ta and Tb for each rotation.

In this case, the signal for l field is transmitted by two tracks Ta.
, If you look at the time length of Tb, it will be recorded with time axis compression, but if you look at each track, the data will be 1/2, so it will be time-expanded by 1.5 times. become.

Fig. 5 shows a timing chart during recording at this time, in which the input wideband video signal SV (is divided into 6 parts, and this divided part is sent to the time axis expansion circuits (248) and (24B)). Then, as shown in Fig. 6B and C, the time axis of the tape winding is expanded to an angle of 270 degrees, and the signal is converted back to an analog signal and recorded.Then, the heads (IIA) and (IIB) In order to take into account the deviation X in the rotational direction, the delay circuit (28) compensates for the time difference d corresponding to the deviation.

Note that during this recording, the drum phase servo is applied and the heads (IIA) and (IIB) are aligned with the tape (2).
During the upper scanning period, a signal whose time axis has been expanded by 270° is supplied to these heads (IIA) and (IIB).

During this recording, a signal for tracking control during playback may be recorded at the edge of the tape in the width direction using a fixed head as in the past, or it may be superimposed on the video signal as in the case of 8mm video. It is also possible to record pilot signals of four frequencies cyclically, and to perform tracking using these pilot signals of four frequencies during reproduction.

Figure 6 is a block diagram of the reproduction system for the wideband signals recorded in this way. The signals reproduced by the heads (IIA) and (IIB) are sent to the FM demodulation circuit (31^) through amplifiers (30A) and (30B). and (31B) to be demodulated, and the demodulated signal is sent to the A/D converter (31B) and demodulated.
2A) and (32B) and converted into digital signals. And this A/D converter (32A) and (3
The digital signal from 2B) is sent to the time axis error correction circuit (3B).
3).

The signals through the amplifiers (31A) and (31B) are also supplied to clock generation circuits (34A) and (34B). This clock generation circuit (34A) and (34B
) consists of a PLL circuit, and a time axis error correction circuit (3
3) Form a write signal. In other words, the signals of the clock generation circuits (34A) and (34B) are signals having time axis fluctuations of the reproduced signals, and are thereby stored in the memory of the time axis error correction circuit (33) by the A/D converter (32A). and writes the signal from (32B). On the other hand, a read clock signal based on the output of the crystal oscillator from the timing control circuit (35) is supplied to the time axis error correction circuit (33), and the signal written in the memory is read out and the time axis error is corrected. Ru. This time-base error-corrected signal is then processed by the time-base compression circuit (3
6A) and the head (IIA) and (II
B) is supplied to the time axis compression circuit (36B) through a delay circuit (37) according to the deviation in the rotational direction. and,
The signals expanded in the time axis compression circuits (36A) and (36B) are compressed into the original time axis signals for each horizontal line, and the output signals are supplied to the synthesis circuit (38) and synthesized. A signal having the original time axis and returned to the original time series is obtained from this, which is supplied to the D/A converter (39) and returned to the original wideband analog video signal, and is sent to the output terminal (40). is derived.

As is clear from the above, in this example, track T
The signals of odd-numbered horizontal lines are recorded on track a, and the signals of even-numbered horizontal lines are recorded on track Tb. The recording wavelength of the signals recorded on one track Ta and Tb is 1.5 times longer than the recording wavelength of a conventional home VTR because the tape is wound over 270° and the time is expanded. It becomes five times.

Therefore, if the recordable baseband of a conventional home VTR is about 3MHz, the baseband is about 4MHz.
This means that a signal of about 8 MHz can be recorded on each track, and a wideband signal of 8 MHz can actually be recorded on two tracks.

In addition, in the case of this example, the S/N is improved compared to the case where the tape is wound 180 degrees and the two rotating heads (1^) (IB) are rotated at twice the speed of the conventional method. can be expected.

That is, here, λ: Recording wavelength V: Relative speed between the tape and the rotating head f cc : Center carrier frequency fB: Baseband bandwidth T - Nidrach width Δf: FM31 [ill's deviation C: When taken as a constant, then , a comparison of the values in the example of FIG. 7 and this example is as shown in the following table.

Note that in the case of a configuration with two rotary heads, the recording band per track, that is, one channel, is multiplied by the reciprocal of the time axis compression, which is twice the recording band, or -
fB.

As is clear from the above table, this example increases the S/N.

Note that, although the above description has been made using an example of a video signal as a wideband signal, it is needless to say that the present invention is not limited to a video signal. Alternatively, two or more n heads may be used, and the signal may be divided into n channels and recorded.

〔Effect of the invention〕

According to this invention, although the input wideband signal is divided into n parts, the time axis is expanded and the signals are recorded and played back almost simultaneously, so that the signal from the upper half of the screen and the signal from the lower half of the screen are divided into two parts, unlike the conventional method. The track switching point does not appear as noise on the playback screen.

Furthermore, variable speed playback can be performed using almost the same processing as before.

Further, according to the present invention, since the tape is wound over 180 degrees, the S/N when the recorded signal is played back is
N can be improved as described above compared to doubling the number of rotations of the rotary head mentioned at the beginning.

[Brief explanation of drawings]

Fig. 1 is a diagram illustrating an example of a rotary head device used in the device of the present invention, Fig. 2 is a diagram showing the relationship in the height direction of the rotary head, and Fig. 3 is a diagram showing the recording track pattern thereof. Fig. 4 is a block diagram of an example of the recording system, Fig. 5 is a timing chart during recording, Fig. 6 is a block diagram of an example of the recycled yarn, and Fig. 7 explains an example of a conventional rotary head device. FIG. 8 is a diagram showing the recording track pattern, and FIG. 9 is a diagram showing the reproduction direction. (118) and (IIB) are rotary heads, (23) is a channel division circuit, and (24A) and (24B) are time axis expansion circuits. oh to one, do j [1tl) J'1NII1 mouth Fig. 1 [Wakenmuhemad@&vl'fl (cloud table nema 64 菖 miroku tramakuba ° turn-V Fig. 3 to the circular drop device Φmwtg record Figure 8 Play lll1ll! Exhaust town〕9 prongs

Claims (1)

[Claims] It has n (n is an integer of 2 or more) rotating heads that are located close to each other and offset from each other in the height direction, and that is inclined over an angular range of more than 180° with respect to the rotating circumferential surface of these rotating heads. A rotating head device on which a tape is wound, and an input broadband signal is temporally divided into n parts for each rotation of the rotating head, and each divided signal is time-axis converted into a time length corresponding to the tape winding angle. and the n time-base-converted signals are supplied to the n rotary heads, respectively, to form and record n tracks on the tape almost simultaneously. recording device.