JPH0738710B2 - Magnetic recording / playback device - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus (hereinafter referred to as VTR),
Using a magnetic tape suitable for recording high frequency signals, FM
The present invention relates to a VTR that sets a carrier of a luminance signal to a higher frequency than before and performs recording.

[Conventional technology]

In the current VHS type VTR, a video signal is recorded on a magnetic tape by a luminance signal FM modulation / chromaticity signal low frequency conversion multiplex recording method. That is, the luminance signal has a carrier frequency of 3.4 to
FM modulated to 4.4MHz, chromaticity signal is a subcarrier frequency 3.58MH
From z, it is converted to 0.629MHz and recorded. Therefore, the transmission frequency band of the luminance signal is about 3 MHz, and the horizontal resolution is limited to about 240 lines.

As a means of improving the horizontal resolution, the journal of the Television Society 19
As described in the May 1986 issue, pages 36 to 39, there is a high band recording method in which the carrier frequency of the luminance signal is shifted to the high frequency side.

[Problems to be solved by the invention]

When applying the high band recording method to a VHS type VTR,
A magnetic tape capable of recording a signal having a higher frequency, that is, a shorter wavelength than ever before is required. At present, at the trial production level, magnetic tapes capable of achieving a high band of about 1 to 2 MHz are being made by means such as high density packing of magnetic powder.

By the way, the above-mentioned prior art does not consider the fact that a high-band recording system is newly applied by using a dedicated magnetic tape for high-band recording, and there is a difference between the high-band recording tape and the conventional recording tape. There was a problem in discrimination and compatibility with the conventional recording method.

The object of the present invention is to realize a system for automatically discriminating between a high band recording tape and a conventional tape in a high band recording VTR, and by switching the signal system circuit, both high band recording and conventional recording are possible. In addition, during playback, it is automatically determined whether it was recorded in high band recording or conventional recording to ensure upward compatibility, and to provide a means for improving image quality by applying high band recording. is there.

[Means for solving problems]

 The above object is achieved by the following means.

First, as a magnetic tape for high band recording, one that can record short wavelengths and has excellent recording / reproducing characteristics of high frequency signals is used. Features such as holes, grooves, and protrusions that are not found in

Secondly, a circuit for detecting the cassette half characteristic of the high band recording tape is provided.

Thirdly, a switch is provided which allows the user to select between high band recording and conventional recording during recording. If a high-band recording tape is used according to the output of the detection circuit, either high-band recording or conventional recording can be arbitrarily selected by the position of this switch, and the conventional tape is used. In this case, conventional recording is performed regardless of the position of the switch.

Fourthly, at the time of reproduction, a circuit is provided which discriminates in frequency whether the reproduction signal is high-band recorded or conventionally recorded.

[Action]

By using a magnetic tape with excellent characteristics for short wavelength recording for high band recording, the attenuation of high frequency components of the recording signal is reduced and high band recording with VHS VTR is possible.
Incidentally, conventional recording on a high band tape is naturally possible.

When high band recording is performed, the following advantages are available and image quality can be improved.

(A) The resolution is improved by widening the band of the luminance signal.

(B) The interference between the luminance signal and the chromaticity signal is reduced.

(C) The azimuth effect is increased and the crosstalk from the adjacent track is reduced.

Further, by providing the cassette half of the high-band recording tape with a feature and providing a circuit for detecting this feature in the high-band recording VTR, the tape can be automatically identified.

By providing a switch that allows the user to select between high band recording and conventional recording, and by using this switch together with a circuit that detects the characteristics of the above cassette half, the high band recording tape can be recorded with the recording method desired by the user. In addition, it is possible to prevent accidental high-band recording on the conventional tape. Further, if a frequency discrimination circuit for the reproduction signal is provided, it is possible to automatically discriminate whether the signal recorded on the tape is high band recording or conventional recording. With these automatic discriminating circuits, by switching the signal system circuit in the VTR to the high band mode or the conventional mode, it becomes possible to record and reproduce by any method in the high band VTR, and ensure upward compatibility with the conventional VTR. it can.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows frequency allocation of a video signal recorded on a magnetic tape. Fig. 2 (a) shows the case of a conventional VHS type VTR, with a carrier frequency of 3.4 to 4.4 MHz.
M-modulated luminance signal (Y signal) and subcarrier frequency 3.5
Chromaticity signal (C signal) converted from 8MHz to 0.629MHz
And are frequency-multiplexed and recorded. In this case, the band of the Y signal is about 3 MHz, and the horizontal resolution of the reproduced image is limited to about 240 lines. On the other hand, in one embodiment of the present invention, as shown in FIG. 2 (b), the carrier frequency of the Y signal is, for example, 5.5.
Set to ~ 6.5MHz and make high band about 2MHz. However, the C signal is converted to the low frequency band as usual. In this case, the band of the Y signal is about 5 MHz, and the horizontal resolution can be improved to about 400 lines. However, with conventional magnetic tapes, it is difficult to record at short wavelengths.
The high frequency component of the reproduced signal is greatly attenuated. Therefore, a magnetic tape for high band recording that newly enables short wavelength recording is used. As the high band tape, for example, a magnetic tape, a metal tape or the like may be used.

VTRs designed for use with such high band tapes
When put into practical use, there will be two types of conventional standards and high band standards for both VTRs and tapes. For high band VTRs and tapes, the VTRs of the conventional standard widely used at present
Also, ensuring upward compatibility with tape is an important condition. The securing of upward compatibility will be described below.

FIG. 3 shows the recording / reproducing content in each combination of the conventional standard and the high band standard VTR and tape.

In the case of recording, high band recording is possible only when a high band tape (hereinafter referred to as H tape) is used for a high band VTR (hereinafter referred to as H-VTR). Therefore, when a conventional tape is inserted in the H-VTR, a tape discriminating function is provided in the H-VTR so that high band recording is not erroneously performed.

In order to discriminate the tape, for example, the cassette half of the H tape is provided with shape features such as holes, grooves, and protrusions which are not present in the conventional tape cassette. The H-VTR is provided with a mechanism for detecting this feature, and it is determined whether the tape inserted in the H-VTR is a conventional tape or an H tape depending on the presence or absence of the feature. As this embodiment, FIG. 4 shows an example in which a hole is provided in the cassette half of the H tape. (A) shows the cross section when the conventional tape cassette 23 is inserted into the main body 19 of the H-VTR, and (b) shows the cross section when the H tape cassette 24 is inserted into the main body 19 of the H-VTR. The tape discriminating device 21 is provided with a movable protrusion 20 for detecting the presence or absence of a hole in the cassette half. In the case of (a), since there is no hole in the cassette half, the protrusion 20 is pushed in and the terminal is A signal indicating that the tape inserted from 22 is a conventional tape is output. Also,
In the case of (b), the protrusion 20 hits the hole of the H tape 24 and is not pushed in, and a signal indicating that the tape inserted from the terminal 22 is the H tape is output.

As a result, the H-VTR automatically discriminates the inserted tape, performs high band recording in the case of the H tape, and performs conventional recording in the case of the conventional tape. However, in the case of the H tape, a manual switch for arbitrarily selecting the high band recording or the conventional recording is provided so that the conventional recording can be performed according to the user's need. On the other hand, with conventional VTRs, of course, high-band recording is not possible, so conventional recording is performed regardless of tape. Thus, at the time of recording, there are five kinds of recorded contents shown in FIG. 3 depending on the combination of the tape, VTR, and recording method.

Next, the case of reproducing a tape having these five recorded contents will be described. These tapes may be played back on an H-VTR or may be played back on a conventional VTR. Depending on the combination of tape and VTR at the time of playback, there are 10 playback results as shown in Fig. 3. Become.

During playback, conventional VTR always performs conventional playback regardless of what is recorded on the tape, but H-VTR requires switching between high-band playback and conventional playback according to the recorded content on the tape, and the recorded content determination function Is required. A circuit block diagram of an embodiment of this discrimination function is shown in FIG.
Shown in (b) and (c).

The embodiment of FIG. 5 (a) utilizes a tape discriminating circuit at the time of recording, which will be described later with reference to FIG. 1, and the circuit can be simplified by sharing it with the discriminating circuit at the time of recording. The switch 26 distributes the reproduced FM luminance signal input from the terminal 25 according to the output signal of the tape discriminating circuit input from the terminal 27. In the case of H tape, the signal is applied to switch 28.
The switch 28 is a manual switch that allows the user to judge the recording method by looking at the reproduced image and switch between high band and conventional. A signal is output to the terminal 29 when the recording method is the high band and to the terminal 30 when the recording method is conventional. Also, in the case of conventional tape, all recording methods are conventional recording, so the signal is switched.
Output from 26 to pin 30.

FIG. 5B shows an embodiment using the frequency discriminator 32, and the discrimination at the time of reproduction can be entirely automated. The frequency discriminator 32 frequency-determines whether the reproduced FM luminance signal input from the terminal 25 is a high-band recorded signal or a conventionally recorded signal. Output to terminal 29, conventionally terminal 30. The frequency discrimination circuit 32 may be configured as shown in the block diagram of FIG. 6, for example. The luminance FM signal input from terminal 33 is FMAGC
The amplitude is made constant by the circuit 34 and added to the BPF 35 and BPF 36. For BPF35, for example, around 4MHz, for BPF36, for example, 6MHz
Only the nearby signal components are extracted and added to the level comparator 37. The level comparator 37 determines that the reproduction signal is conventional recording when the output level of the BPF 35 is high, and determines high band recording when the output level of the BPF 36 is high, and outputs the result to the terminal 38.

FIG. 5 (c) is a composite type of (a) and (b). Terminal
The reproduction FM luminance signal input from 25 is switched by the switch 26 according to the output signal of the tape discriminating circuit input from the terminal 27. Signal is switch 31 only for H tape
And to the frequency discriminating circuit 32, and is distributed to the terminal 29 for high band recording and to the terminal 30 for conventional recording as in the embodiment of FIG. Further, in the case of the conventional tape, the signal is directly output to the terminal 30.

According to these embodiments, the recorded contents of the tape are discriminated in the H-VTR and the reproduction is performed according to the discriminated contents. Therefore, the H-VTR can handle all five types of recorded contents.

On the other hand, in the conventional VTR, high band reproduction is impossible,
It is not possible to play back H tapes recorded in high band with H-VTR. However, since the other four types of recorded contents are all conventional recording, they can be reproduced by the conventional VTR.

From the above, according to this embodiment, the recording and reproducing shown in FIG. 3 can be performed, and the upward compatibility with the conventional VTR and the conventional tape can be secured.

Next, an embodiment of the circuit of the present invention will be described. FIG. 1 shows a block diagram of a video signal recording system circuit in the embodiment of the H-VTR. NTSC input from terminal 1 in the figure
The chromaticity signal of the video signal is removed by the chromaticity signal removing circuit 2, and only the luminance signal is added to the switch 3. The output signal of the above-mentioned tape discriminating circuit is inputted to the terminal 4 of the switch 3, and the switch 3 is switched in accordance with this signal,
In the case of H tape, a signal is sent to the switch 5. The switch 5 is a manual switch that can switch between high-band recording and conventional recording according to the user's need. In the case of high-band recording, the signal passes through the LPF6 and FM modulator 7 for high-band recording and then to the switch 8. Added. On the other hand, switch 5
When conventional recording is selected in, the signal is LPF9, F for conventional recording.
It is applied to the switch 8 through the M modulator 10. Also, H
Even when a conventional tape is inserted in the -VTR, the signal is sent from the switch 3 to the LPF 9 and FM modulator 10 and subjected to the conventional recording process. The switch 8 is connected as shown in FIG. 1 in the case of high-band recording and reversely connected in the case of conventional recording, and sends the FM-modulated luminance signal to the HPF 11. The HPF 11 removes a signal component in a frequency band that overlaps with a low-pass converted chromaticity signal, which will be described later, and adds the signal to the adder 12.

The video signal input from terminal 1 is also added to the BPF13, and only the chromaticity signal component is generated at the BPF13, and the frequency converter 14
The sub-carrier frequency is converted from 3.58 MHz to 0.629 MHz in the low frequency range, and the signal component in the frequency band overlapping with the luminance signal FM-modulated by the LPF 15 is removed and added to the adder 12.

The adder 12 frequency-multiplexes the luminance signal and the chromaticity signal, passes through the recording amplifier 16, and passes through the video head 17 to the magnetic tape 18
Recorded in.

FIG. 7 shows a block diagram of a video signal reproduction system circuit in the embodiment. In the figure, the video signal recorded on the magnetic tape 18 is read by the video head 17 and reproduced by the reproducing amplifier 39.
Pass through and be added to HPF40. Here, only the FM luminance signal is obtained. After that, for example, the discrimination circuit shown in FIG.
The content of the recording is discriminated at 41, and in the case of high band recording, it passes through the FM equalizing circuit 42 for high band and is added to the switch 44.

On the other hand, in the case of conventional recording, it is applied to the switch 44 through the conventional FM equalization circuit 43. Switch 44 is a frequency discrimination circuit
With the switch that can be switched by 32 outputs, the connection shown in FIG. 7 is used when the reproduction signal is high-band recording, and the connection is reversed when conventional recording is used. The signal is sent from switch 44 to FM demodulator 45.
To the adder 47. The LPF 46 removes unnecessary frequency components and adds them to the adder 47.

Further, the output of the regenerative amplifier 39 is also added to the LPF 48, and only the chromaticity signal converted in the low frequency range here becomes the frequency converter.
The subcarrier is converted to the original 3.58 MHz at 49, the unnecessary frequency component is removed at the BPF 50, and added to the adder 47. Here, the frequency signal is frequency-multiplexed with the luminance signal described above, and the original NTSC signal is output to the terminal 51.

If the signal recording of the frequency allocation shown in FIG. 2 (b) is performed using the circuit shown in FIGS. 1 and 7, high band recording is possible while ensuring upward compatibility.

〔The invention's effect〕

As described above, the present invention, in the VHS VTR, performs high-band recording using a magnetic tape for high-band recording, which has excellent short-wavelength recording characteristics, and a circuit for discriminating between a high-band tape and a conventional tape, By using the selection switch of the recording system and the circuit for discriminating between the high band of the reproduced signal and the conventional one, it is possible to secure upward compatibility in the VTR for high band recording, and to select and automatically discriminate the recording mode without error.

By the tape discriminating circuit and the frequency discriminating circuit, the discrimination between the high band at the time of reproduction and the conventional system is automated, and
At the time of recording, high band recording can be arbitrarily selected only when the high band tape is used, and the disadvantage that high band recording is erroneously performed on the conventional tape can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a recording system according to the present invention, FIG. 2 is an explanatory diagram showing a conventional standard of VHS system VTR and frequency allocation of recording signals in the present invention, and FIG. 3 is a magnetic tape, VTR. , An explanatory view showing a reproduction result by a combination of recording methods, FIG. 4 is an explanatory view of a tape discriminating device, and FIG.
FIG. 7 is a block diagram of a discriminating circuit at the time of recording, FIG. 6 is a circuit block diagram of a frequency discriminator, and FIG. 7 is a block diagram showing an embodiment of a reproducing system according to the present invention. 2 ... Chromaticity signal removal circuit, 3,5,8 ... Switch, 6,9 ... LPF, 7,10 ... FM modulator, 21 ... Tape discriminating device, 26.28,31 ... Switch, 32 ... … Frequency discriminator, 35,36 …… BPF, 37 …… Level comparator, 41 …… Recording system discrimination circuit, 42,43 …… FM equalization circuit, 44 …… Switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Michio Masuda Inventor Michio Masuda 292 Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture Home Appliances Research Laboratories (72) Inventor Kuniaki Miura 1410 Inada, Katsuta, Ibaraki Hitachi, Ltd. (56) References JP-A-59-81989 (JP, A) JP-A-58-150105 (JP, A)

Claims (2)

[Claims] 1. A first recording mode for recording a video luminance signal as an FM modulated signal of a predetermined carrier frequency on a magnetic tape, and an FM modulated signal of a video luminance signal having a carrier frequency higher than that of the first recording mode. It has a second recording mode for recording on a magnetic tape as a modulated signal, and when recording in the second recording mode, it has excellent short-wavelength recording characteristics and is a cassette type that uses a specified magnetic tape. In the magnetic recording / reproducing apparatus, the cassette half containing the specified magnetic tape used in the second recording mode is provided with a shape feature, a circuit for detecting this feature, and the first and second recording modes are selected at the time of recording. And a circuit for discriminating which of the first and second recording modes is used for recording, based on the frequency of the reproduction signal during reproduction, and the detection circuit used for recording in the second recording mode. When the characteristic of the cassette shape is not detected, the recording is performed in the first recording mode regardless of the switch, and the shape of the cassette used in the second recording mode is detected by the detection circuit during recording. The magnetic recording / reproducing apparatus is characterized in that the recording mode is determined by the output from the selection switch when the characteristic is detected. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the circuit for discriminating the frequency of the reproduced signal has a band leaker for passing the luminance FM carrier frequency in the first recording mode, and Consists of a band leaker that passes the luminance FM carrier frequency of the recording mode and a circuit that compares the levels of the outputs of both band leakers, and inputs the playback luminance FM modulated signal to both band leakers. A magnetic recording / reproducing apparatus having the above structure.