JPH0456364B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus that has a helical scan type head device and performs FM modulation on an audio signal to record and reproduce it on diagonal tracks on a tape.

BACKGROUND ART AND PROBLEMS The applicant of the present application previously proposed a new video tape recorder (VTR) with improved audio signal characteristics.

That is, as shown in FIG. 1, two rotating magnetic heads H _V1 and H _V2 are installed with an angular spacing of approximately 180°, and two rotating magnetic heads are installed adjacent to these heads H _V1 and H _V2 , respectively. Magnetic head H _A1 and H _A2
are attached with an angular spacing of approximately 180°. In addition, heads H _A1 and H _A2 are heads H _V1 and H A2, respectively.
It is installed on the rotational direction X side of the heads H _V1 and H _V2 so as to precede H _V2 . Further, the magnetic tape T is run diagonally along the tape guide drum 4 over an angular range of approximately 180 degrees in the Y direction.
As shown in FIG _{. 2 , the} azimuth angles ₍ inclination angles _with respect to the direction perpendicular to the scanning direction _V1 ≒+7°, θ _V2 ≒−7°. Furthermore, the azimuth angles θ _A1 and θ _A2 of the gaps g _A1 and g _A2 of _the heads H A1 and H _A2 are made different from each other. In general, the crosstalk ratio due to azimuth loss is as follows: crosstalk is _Cx , signal is S, recording wavelength is λ, track width is w, and relative azimuth angle is θ.
Then, C _x /S=sin(2πw/λ・tanθ)/2πw/λ・ta
It can be expressed as nθ...(1). The azimuth angles θ _A1 and θ _A2 of _the gaps g _A1 and g _A2 of heads H _A1 and H _A2 are
In the relationship between H _A2 , H _A1 and H _V1 , and H _A2 and H _V2 ,
For example, tan θ in the above equation (1) is set to be 1 or more, so that almost no crosstalk occurs between the two. For example, θ _A1 ≒ −
45°, θ _A2 ≒ +45°. Also, these heads
Gap of H _A1 and H _A2g Width of _A1 and g _A2 is head
The gap of H _V1 and H _V2 is made wider than the width of g _V1 and g _V2 . For example, the width of gaps _gV1 and _gV2 of heads H _V1 and H _V2 is about 0.3 μm, whereas the width of gaps g _A1 and g _A2 of heads H _A1 and H _A2 is 1.5 to 2.0 μm. be done. Normally, in magnetic recording, it is possible to record on the magnetic layer of a magnetic tape to a depth that is approximately half the gap width of a magnetic head. Furthermore, when considering reproduction, the longer the recording wavelength, the deeper recording can be made in the magnetic layer. head
The width of the gaps g _A1 and g _A2 of H _A1 and H _A2 is made wider than the width of the gaps g _V1 and gθ _V2 of heads H _V1 and H _V2 because the signals recorded at heads H _V1 and H _V2 are This is because the signals recorded by heads H _A1 and H _A2 are recorded deeper into the magnetic layer of the magnetic tape.

Furthermore, the heads H _V1 , H _V2 , H _A1 , and H _A2 are rotated once in one frame, for example. And head
H _A1 , H _V1 and heads H _A2 , H _V2 are configured to alternately scan the magnetic tape T every field. At this time, heads H _A1 and H _A2 scan the magnetic tape T in advance of heads H _V1 and H _V2 , respectively.

When recording with this device, heads H _V1 and
A composite signal of the normal low-frequency conversion color signal C _D and the modulated luminance signal Y _FM is supplied to H _V2 . Also, the head
A composite signal of modulated audio signals A _{LFM and A RFM obtained} by FM modulating the audio signal in a predetermined band, respectively, is supplied to H _A1 and H _A2 . Therefore, as shown in Figure 3,
On the magnetic tape T, alternately every field,
A recording track T ₁ by the heads H _A1 and _HV1 and a recording track T ₂ by the heads H _A2 and _HV2 are sequentially formed. Then, on the recording tracks _T1 and _T2 , a composite signal of the low-frequency conversion color signal _CD and modulated luminance signal _YFM and a composite signal of the modulated audio signals _ALFM and _ARFM are recorded overlappingly at different recording azimuths. be done. That is,
FIG. 44A shows the recording track _T1 by the heads H _A1 and H _V1 . When observing this cross section, as _shown in FIG. The composite signal of _LFM and A _RFM is recorded deep into the magnetic layer Ta of the magnetic tape T, and then the composite signal of the low frequency conversion color signal _CD and the modulated luminance signal _YFM is recorded on the magnetic layer Ta by the head H _V1 . lightly recorded. The same applies to track _T2 . In FIG. 4B, Tb is the base.

Further, during reproduction, heads H _A1 and H _V1 and heads H _A2 and H _V2 scan recording tracks _T1 and _T2 , respectively. Therefore, head H _A1
and H _A2 , a composite signal of the modulated audio signals A _LFM and A _RFM is reproduced from the recording tracks T ₁ and T ₂ , respectively.
In addition, heads H _V1 and H _V2 each record a track.
A composite signal of the low frequency conversion color signal C _D and the modulated luminance signal Y _FM is reproduced from T ₁ and T ₂ .

FIG. 5 shows an example of a specific circuit configuration. In the figure,
100V is a circuit for recording a video signal, and a video signal S _V is supplied to a terminal 11 . This video signal S _V is supplied to a low-pass filter 12 to obtain a luminance signal Y, which is supplied to an FM modulator 14 through a pre-emphasis circuit 13 .
In the FM modulator 14, the luminance signal Y is FM modulated so that the white peak is 4.8 MHz and the sync chip is 3.6 MHz, and the modulated luminance signal Y _FM
is obtained. This modulated luminance signal Y _FM is band-limited through a high-pass filter 15 , further amplified by an amplifier 16 , and then supplied to a combiner 17 .

Further, the video signal S _V supplied to the terminal 11 is supplied to a bandpass filter 18 to obtain a color signal C, which is supplied to a frequency converter 19 .
This frequency converter 19 is supplied with a conversion signal from an oscillation circuit 20, and the carrier frequency is, for example,
A 688kHz low-frequency conversion color signal C _D is obtained. This low-pass converted color signal C _D is band-limited through a low-pass filter 21, further amplified by an amplifier 22, and then supplied to a combiner 17.

The composite signal of the modulated luminance signal Y _FM and the low frequency conversion color signal C _D obtained from the synthesizer 17 is transferred to the selector switch 2.
3 and the head through the rotary transformer 24.
It is supplied to the head H _V1 and also to the head H _V2 through the changeover switch 25 and the rotary transformer 26. The changeover switches 23 and 25 are respectively connected to the R side during recording and to the P side during playback.

100A is an audio signal recording circuit, and terminals 30L and 30R are connected to the first audio signal (left signal for stereo, main signal for dual audio) A _L and the second audio signal.
An audio signal (right signal for stereo, sub signal for dual audio) A _R is supplied.

The first audio signal A _L is passed from the terminal 30L through the compression circuit 31L that constitutes the noise reduction circuit.
It is supplied to the FM modulator 32L. And this
In the FM modulator 32L, the first audio signal A _L
is FM-modulated, for example, with a carrier frequency of 1.35 MHz and a frequency deviation of ±75 KHz, to obtain a modulated audio signal _ALFM . This modulated luminance signal A _LFM is supplied to the synthesizer 34 through a low-pass filter or band-pass filter 33L for removing harmonics. Also,
The second audio signal A _R is passed from the terminal 30R through the compression circuit 31R that constitutes the noise reduction circuit.
It is supplied to the FM modulator 32R. And this
In the FM modulator 32R, the first audio signal A _R
For example, if the carrier frequency is 1.50MHz and the frequency deviation is ±
It is FM modulated at 75kHz to obtain a modulated audio signal A _RFM . This modulated audio signal A _RFM is passed through a low-pass filter or band-pass filter 3 for removing harmonics.
It is supplied to the combiner 34 through 3R.

In the synthesizer 34, the modulated sound signal A _LFM ,
A _RFM is synthesized. Then, this composite signal is amplified by an amplifier 36, and the signal from this amplifier 36 is transmitted to a changeover switch 39 and a rotary transformer 40.
This signal is supplied to the head H _A1 through the selector switch 41 and the rotary transformer 42.
is supplied to head H _A2 through. The changeover switches 39 and 41 are connected to the R side during recording, respectively.
During playback, it is connected to the P side.

During recording, switch 23, 25, 39, 4
1 are respectively switched to the R side, so that the composite signal of the low frequency conversion color signal _CD and the modulated luminance signal _YFM is supplied to the heads H _V1 and H _V2 as described above. In addition, the heads H _A1 and H _A2 have modulated audio signals A _LFM ,
A _RFM composite signal or cancellation signal is supplied.
Therefore, as shown in FIG. 3, heads H _A1 and H _V1 are placed alternately for each field on the magnetic tape T.
A recording track T ₁ by the head H _A2 and a recording track T ₂ by the heads H A2 and H _V2 are sequentially formed.

200V is a video signal reproduction circuit. As mentioned above, the low frequency converted color signal C _D and the modulated luminance signal Y _FM are reproduced from the recording track T ₁ by the head H _V1 .
The combined signal is supplied to the switch circuit 51 through the amplifier ₅₀₁ . Further, as described above, a composite signal of the low frequency converted color signal _CD and the modulated luminance signal _YFM reproduced from the recording track _T2 by the head H _V2 is supplied to the switch circuit ₅₁ through the amplifier 502.
The switch circuit 51 has a head connected to the terminal 51a.
A switching control signal Sa obtained according to the rotational positions of H _V1 and H _V2 is supplied to control the switching.
From this switch circuit 51, the head
A composite signal reproduced by H _V1 and H _V2 is obtained alternately for each field.

The composite signal obtained from this switch circuit 51 is supplied to a high pass filter 52, from which a modulated luminance signal _YFM is obtained.
This modulated luminance signal Y _FM is supplied to the FM demodulator 54 through the limiter circuit 53.
4, the luminance signal Y is obtained. This luminance signal Y is supplied to a combiner 56 through a de-emphasis circuit 55.

Further, the composite signal obtained from the switch circuit 51 is supplied to a low pass filter 57, from which a low frequency converted color signal C _D is obtained. This low frequency converted color signal C _D is sent to the frequency converter 58
supplied to This frequency converter 58 has an AFPC
A conversion signal is supplied from a circuit (automatic frequency and phase control circuit) 59, and the low frequency conversion color signal C _D is converted into a color signal C having a carrier frequency of, for example, 3.58 MHz. This color signal C is supplied to a combiner 56 through a bandpass filter 60.

In the synthesizer 56, the luminance signal Y and the color signal C are synthesized, and the output terminal 61 receives the video signal S _V
is obtained.

200A is a circuit for reproducing audio signals. As mentioned above, the composite signal of the modulated audio signals A _LFM and A _RFM reproduced from the recording track T ₁ by the head H A ₁ is passed through the amplifier 70 ₁ and has a center frequency of about 1.35 MHz.
The signal is supplied to a bandpass filter 71L ₁ whose center frequency is approximately 1.50 MHz, and is also supplied to a bandpass filter 71R ₁ whose center frequency is approximately 1.50 MHz. A modulated audio signal A _LFM is obtained from the bandpass filter 71L ₁ and is supplied to the FM demodulator 73L ₁ through the limiter circuit 72L ₁ . This FM demodulator 73L ₁
A first audio signal A _L is obtained from the switch circuit 74L, and is supplied to one terminal of the switch circuit 74L. Also,
From the bandpass filter 71R ₁ , the modulated sound signal
A _RFM is obtained and supplied to the FM demodulator 73R ₁ through the limiter circuit 72R ₁ . A second audio signal _AR is obtained from the FM demodulator _73R1 , and is supplied to one terminal of the switch circuit 74R.

Further, as mentioned above, the composite signal of the modulated audio signals A _LFM and A _RFM reproduced by the head H _A2 from the recording track T ₂ is passed through the amplifier 70 ₂ to the band pass filter 71 L ₂ whose center frequency is approximately 1.35 MHz. At the same time, it is also supplied to a bandpass filter _71R2 whose center frequency is approximately 1.50MHz.
Modulated audio signal from bandpass filter 71L ₂
A _LFM is obtained and supplied to the FM demodulator 73L ₂ through the limiter circuit 72L ₂ . A first audio signal A _L is obtained from this FM demodulator 73L ₂ and is supplied to the other terminal of the switch circuit 74L. Further, a modulated audio signal A _RFM is obtained from the bandpass filter 71R ₂ and is supplied to the FM demodulator 73R ₂ through the limiter circuit 72R ₂ .
A second audio signal A _R is obtained from this FM demodulator 73R ₂ and is supplied to the other terminal of the switch circuit 74R.

A switching control signal Sa obtained according to the rotational positions of the heads H _A1 and H _A2 is supplied from a terminal 74 La to the switch circuit 74L, and the switching is controlled. That is, during one field period when head H _A1 is scanning recording track _T1 , the terminal is switched to one terminal, and during another field period when head H _A2 is scanning recording track _T2 , the terminal is switched to the other terminal. It will be done. Therefore, from this switch circuit 74L,
The first audio signal A _L obtained from the FM demodulators 73L ₁ and 73L ₂ is obtained alternately for each field, and this is sent to the expander 7 which constitutes the noise reduction circuit.
It is supplied to the output terminal 76L through 5L.

Further, the switching control signal Sa is also supplied to the switch circuit 74R from the terminal 74Ra.
The switching is controlled in the same way as 4L. Therefore, from this switch circuit 74R, the FM demodulator 73R ₁
and 73R ₂ are obtained alternately for each field, and are supplied to an output terminal _76R through an expander 75R constituting a noise reduction circuit.

However, in the above device, the heads H _A1 ,
When H _A2 first contacts (enters) the tape T, the tape T stretches due to the head collision. When recording is performed in this state, when each diagonal track is viewed continuously, the elongated portion shown in Figure 6A becomes shorter when the tape T returns to its original position, and this portion is recorded. As shown in FIG. 6B, the recording signal becomes denser and the frequency of the recording signal becomes higher.

This phenomenon is not a problem when recording and playing back on the same VTR because the expansion and contraction occurs in almost the same state, but when playing back on another VTR, the head H _A1 ,
_H Noise will occur in the FM demodulation output. And this noise is head
It has a periodicity of 50 or 60 Hz depending on the rotation of H _A1 and H _A2 , and this harmonic component is especially harsh in the range of about 1 kHz or less.

Note that in conventional recording of only video signals, this part was outside the effective screen, so no problem occurred.

OBJECTS OF THE INVENTION In view of these points, the present invention has a simple structure that prevents noise from occurring due to expansion and contraction of the tape.

SUMMARY OF THE INVENTION The present invention provides a recording and reproducing apparatus which has a helical scan type head device and which performs FM modulation on an audio signal and records and reproduces it on diagonal tracks on a tape. Another head is provided in front of the first head, and the first head and the other head are arranged so that the first head plunges into the tape at least during the residual period of the shaking due to the plunge of the other head into the tape. This is a recording and reproducing apparatus characterized by having a tape having a simple structure and no noise caused by expansion and contraction of the tape.

Example In Fig. 7, heads H _A1 and H _A2 are
After H _V1 , H _V2 , for example 0.5 ~ at normal rotation speed
Provided at a position 1msec behind. Furthermore, as shown in FIG. 8, between the heads H _A1 and H _V1 and between H _A2 and H _V2 , a step h of about one pitch or more of the diagonal track on the tape T is created so that the heads H _A1 and H _A2 can T
Provided so that it is on the supply side.

As a result, the tape T first has heads H _V1 ,
Elongation occurs when H _V2 collides, but
At the same time, the tape T vibrates, and while this vibration remains, the heads H _A1 and H _A2 rush in, and the heads H _A1 and H _A2 come into contact with the tape T without colliding with the tape T. In the heads H _A1 and H _A2 , recording and reproduction are performed without elongation of the tape T.

Therefore, recording and reproduction are performed without expanding or contracting the tape T, and there is no risk of noise occurring even when reproduction is performed on another VTR having the same configuration.

In addition, when performing deep recording as described above, by providing the step h as described above, the tape T
In the above example, recording is first performed by heads H _A1 and H _A2 , and then recording is performed by heads H _V1 and H _V2 .

Note that the step h may be recorded by the heads H _A1 and H _A2 a plurality of tracks in advance. Also, in this case, by providing an extra step by 1/2 track pitch, the heads H _V1 and H _V2 , which are formed wider than the heads H _A1 and H _A2 , can straddle the three deep recorded tracks during playback. Noise due to crosstalk of deeply recorded signals can be minimized.

Furthermore, as mentioned above, the optimal spacing between heads H _A1 , H _V1 and H _A2 , H _V2 is 0.5 to 1 msec at normal rotation speed, which is, for example, 5.4 to 10.8 msec at 60 Hz rotation.
Corresponds to an angular interval of degrees.

As a result of simulation, it was confirmed that noise was improved by about 3dB.

Also, when frequency multiplexing an FM audio signal between a luminance signal and a chroma signal and recording and reproducing it using a set of rotating heads, the same effect can be obtained by providing a dummy head in front of the head. be able to.

Effects of the Invention According to the present invention, noise caused by expansion and contraction of the tape can be prevented from occurring with a simple configuration.

[Brief explanation of the drawing]

1 to 6 are diagrams for explaining a new VTR previously proposed by the applicant, and FIGS. 7 and 8 are configuration diagrams of an example of the present invention. H _A1 and H _A2 are recording and reproducing heads for FM audio signals;
H _V1 and H _V2 are other heads, T is the tape, and h is the step.

Claims (1)

[Claims] 1. In a recording and reproducing apparatus that has a helical scan type head device and records and reproduces FM-modulated audio signals on diagonal tracks on a tape, a head that precedes one head on which the audio signal is recorded and reproduced. The first head and the other head are arranged such that the first head plunges into the tape at least during the remaining period of shaking due to the plunge of the preceding other head of the tape. A recording and reproducing device that performs