JPH05325406A - Recording and reproducing device for information signal - Google Patents

Abstract

PURPOSE:To improve S/N keeping interchangeability for reproduced picture quality with the other recording and reproducing device of the same standard. CONSTITUTION:It is selected that an input video signal is directly processed in a CR pre-emphasis circuit 6 based on the existing standard by a switching circuit 3 or after the input signal is processed by a pre-emphasis circuit 2 of which a transfer function is (1+Ksin<2> (omegaT)).exp (-2ST) and which has a phase characteristic of linear state and the maximum gain of approximately 2dB, it is processed by the CR pre-emphasis circuit 6, modulated by a FM modulation circuit 7, and recorded in a magnetic tape 10. Also, a reproduced signal of the magnetic tape 10 is demodulated to a video signal by a FM demodulation circuit 13, after it is processed by a CR de-emphasis circuit 14 having an inverse characteristic to the CR pre-emphasis circuit 6, it is directly outputted from an output terminal 18, or after it is processed by a de-emphasis circuit 15 having an inverse transfer function and a phase characteristic to the pre-emphasis circuit 2, it is outputted from the output terminal 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information signal recording / reproducing apparatus for improving S / N of an information signal such as a video signal.

[0002]

2. Description of the Related Art As a method for improving S / N in recording / reproducing information signals such as video signals, there have been conventionally known methods such as JP-A-53-131814 and JP-A-53-131815.
As described in Japanese Patent Publication No. Sho 61-8632 and Japanese Patent Publication No. 61-8632, the time constants of the pre-emphasis circuit on the recording side and the de-emphasis circuit on the reproducing side are made to completely coincide with each other to flatten the overall frequency characteristic. In this way, high-frequency emphasis recording is performed.

[0003]

However, such a conventional S / N improving method has the following problems. That is, 1. Generally, in order to improve the S / N, when trying to emphasize the high frequency component by the pre-emphasis circuit, when the FM modulation recording method is adopted, the occupied band of the FM modulation signal as the recording signal is widened, A wider transmission band is required, and at the time of reproduction, a so-called inversion phenomenon occurs and the reproduced image quality is significantly deteriorated.

2. In addition, VTR (Video Tape)
In many recording / reproducing devices such as recorders, the parameters (time constant, etc.) of the emphasis circuit are determined by the unified standard, and the emphasis amount should be intentionally increased to improve the S / N. Can not
Further, even if it is increased, it is not possible to maintain compatible reproduction with other recording / reproducing devices of the same standard. Therefore, the actual S / N is determined by the tape head system, and the S / N of the reproduced image quality is not always satisfactory.

An object of the present invention is to solve such a problem and further improve the S / N within the range in which the visually compatible reproduction with another recording / reproducing apparatus of the same standard can be maintained. An object of the present invention is to provide a recording / reproducing device that does this.

[0006]

In order to achieve the above object, according to the present invention, on the recording side, in addition to a pre-emphasis circuit based on the standard, the transfer function is {1 + Ksin ² (ω
T)} · exp (−2ST) and a new pre-emphasis circuit having a maximum gain of N dB, an information signal processed by the new pre-emphasis circuit, and information not processed by the new pre-emphasis circuit. And a first switching circuit for selecting one of the signals, and on the reproducing side, in addition to the standard de-emphasis circuit,
The transfer function is {1-Ksin ² (ωT)} · {1-K ² si
n ⁴ (2ωT)} · exp (−6ST), a new de-emphasis circuit, a reproduction information signal processed by the new de-emphasis circuit, and a reproduction information signal not processed by the new de-emphasis circuit. And a second switching circuit for selecting either of the above.

[0007]

Operation: The transfer function is {1 + Ksin ² (ωT)} · ex
p (-2ST) is approximately expressed, and the maximum gain is Nd.
The information signal processed by the new pre-emphasis circuit B has a pre-shoot and a post-shoot that extend in both directions at the rising edge and the falling edge. This new pre-emphasis circuit has a linear phase characteristic. Since it has, so-called phase distortion does not occur in the information signal processed by this. The information signal having the pre-shoot and the post-shot is recorded in the high-frequency emphasized by the pre-emphasis circuit based on the standard. During reproduction, the reproduction information signal is suppressed in the high frequency band by a de-emphasis circuit based on the standard, and the transfer function is {1-Ksin ² (ω
T)} · {1-K ² sin ⁴ (2ωT)} · exp (−6
The above pre-shoot and post-shu are suppressed by a new de-emphasis circuit that is approximated by ST),
Since this new de-emphasis circuit also has a linear phase characteristic, so-called phase distortion does not occur in the obtained information signal.

Therefore, even if processed by the new pre-emphasis circuit and the new de-emphasis circuit, no waveform distortion occurs in the reproduced information signal. Further, regarding the S / N, the new de-emphasis circuit is used. Only the amount of suppression of high frequency components will be improved.

Further, even if the recording / reproducing apparatus has the same standard as that of the present invention, it is conceivable to record / reproduce by another recording / reproducing apparatus having no new emphasis circuit. That is,
In contrast to the case where recording is performed without passing through a new pre-emphasis circuit and reproduction is performed by the recording / reproducing apparatus of the present invention, conversely, recording is performed via a new pre-emphasis circuit in the recording / reproducing apparatus of the present invention There are two ways of reproducing with another recording / reproducing apparatus of the same standard as this without a new de-emphasis circuit.

First, in the former case, in the present invention, the switching circuit of the reproducing system is switched, the reproduced signal is processed and output without passing through a new de-emphasis circuit, and a reproduced video signal having a flat frequency characteristic is obtained. be able to.

In the latter case, the above-mentioned other recording / reproducing apparatus does not have the above-mentioned switching circuit. Therefore, the FM demodulated signal may be processed as in the conventional case and output as it is. The resolution of the playback screen can be improved due to the emphasis characteristic within the range in which the existing compatible playback is maintained. Needless to say, in the recording / reproducing apparatus according to the present invention, if the switching circuit is switched to the new de-emphasis circuit side and the reproduced video signal is processed and output, the S / N amount corresponding to the suppression amount of the high frequency component by the new de-emphasis circuit. Will be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of an information signal recording / reproducing apparatus according to the present invention, in which 1 is an input terminal, 2 is a pre-emphasis circuit, 3 is a switching circuit, 4 is an input terminal, 5
Is a clamp circuit, 6 is a CR pre-emphasis circuit, 7 is an FM modulation circuit, 8 is a recording amplifier, 9 is a recording head, and 10 is a recording head.
Is a magnetic tape, 11 is a reproducing head, 12 is a reproducing amplifier,
13 is an FM demodulation circuit, 14 is a CR de-emphasis circuit, 15 is a de-emphasis circuit, 16 is a switching circuit, 1
Reference numeral 7 is an input terminal and 18 is an output terminal.

In FIG. 1, a video signal as an information signal input from the input terminal 1 is a pre-emphasis circuit 2.
And the video signal processed by the pre-emphasis circuit 2 is supplied to the b terminal of the switching circuit 3. The switching circuit 3 is controlled by the switching control signal from the input terminal 4 and selects either the a terminal or the b terminal. The video signal selected by the switching circuit 3 is processed by the clamp circuit 5 and the CR pre-emphasis circuit 6, and then F
It is FM-modulated by the M-modulation circuit 7 to be an FM-modulated signal, amplified by the recording amplifier 8 and supplied to the recording head 9, and recorded on the magnetic tape 10.

The signal reproduced from the magnetic tape 10 by the reproducing head 11 is amplified by the reproducing amplifier 12 and then supplied to the FM demodulation circuit 13 to be demodulated into a video signal and processed by the CR de-emphasis circuit 14. Are supplied to the terminal a of the switching circuit 16 and the de-emphasis circuit 15. The video signal processed by the de-emphasis circuit 15 is supplied to the b terminal of the switching circuit 16. Switching circuit 1
6 is controlled by the switching control signal from the input terminal 17, and selects either the a or b terminal. Switching circuit 1
The video signal selected in 6 is output from the output terminal 18.

Here, the pre-emphasis circuit 2 has a transfer function described later and a linear phase characteristic with a maximum gain of about 2 dB, and the de-emphasis circuit 15 transfers the pre-emphasis circuit 2 as described later. It has a linear phase characteristic with a maximum gain of about -2 dB with a transfer function almost opposite to the characteristic. As a result, the total frequency characteristic of the pre-emphasis circuit 2 and the de-emphasis circuit 15 becomes flat. Further, the CR pre-emphasis circuit 6 adopts a pre-emphasis system based on the standard of the recording / reproducing device, and the CR de-emphasis circuit 14 adopts a de-emphasis system based on the standard of the recording / reproducing device. 6 and the CR de-emphasis circuit 14 also flatten the overall frequency characteristic.

FIG. 2 is a block diagram showing a specific example of the pre-emphasis circuit 2 in FIG. 1. Reference numeral 2a is a filter circuit, 2b is a delay circuit, and 2c is an addition circuit.

In FIG. 2, the pre-emphasis circuit 2 comprises a filter circuit 2a having a transfer function, an adder circuit 2c, and a delay circuit 2b having a delay time of 2T. The transfer function of the filter circuit 2a is Ksin ² (ωT)  exp (-2ST) and the delay time of the delay circuit 2b are set to 2T, respectively, and the transfer function of the pre-emphasis circuit 2 is (1 + Ksin ² (ωT)) · exp (-2ST) It is assumed that the approximated expression has a linear phase characteristic with a maximum gain of about 2 dB.

As the filter circuit 2a, for example, the one described in detail in Japanese Patent Publication No. 60-53483 can be used, which has a ladder-shaped inductance and capacitor as shown in FIG. The inductances L ₂ n and L ₂ n- ₁ and the capacitors C ₂ n and C ₂ n- ₁ for having the above transfer function are also shown in FIG.

FIG. 4 is a block diagram showing a specific example of the de-emphasis circuit 15 in FIG. 1. 15a is a filter circuit, 15b is an inverting amplifier, 15c is a delay circuit, and
Reference numeral 15d is an adder circuit, 15e is a filter circuit, 15f is an inverting amplifier, 15g is a delay circuit, and 15h is an adder circuit.

As described above, the de-emphasis circuit 15 has characteristics almost opposite to those of the pre-emphasis circuit 2 in FIG. 1, and as shown in FIG. 4, the filter circuit 15a, the inverting amplifier 15b, and the delay circuit 15c. And a first circuit including an adder circuit 15d and a filter circuit 15
e, inverting amplifier 15f, delay circuit 15g, and adder circuit 1
And a second circuit composed of 5h. here,
The transfer characteristic of the filter circuit 15a is Ksin ² (ωT) · exp (−2ST), the delay time of the delay circuit 15c is 2T, and the overall transfer function of the first circuit is (1-Ksin ² (ωT)) exp (-2ST). The transfer function of the filter circuit 15e is K ² sin ⁴ (2ωT) · exp (−4ST), the delay time of the delay circuit 15g is 4T, and the transfer function of the second circuit is (1-K ² sin ⁴ (2ωT)) · exp (-4ST). Therefore, the total characteristic of the de-emphasis circuit 15 is {1-Ksin ² (ωT)} · {1-K ² sin ⁴ (2ω
T)} · exp (−6ST) and has a linear phase characteristic with a minimum gain of about −2 dB.

CR pre-emphasis circuit 6 in FIG.
As described above, the pre-emphasis method is based on the standard of the recording / reproducing apparatus. For example, when the recording / reproducing apparatus is of the VHS system, a simple circuit including a capacitor C ₁ and resistors R ₁ and R ₂ as shown in FIG. 5 is often used, and the emphasis parameter is X = 4. ,
It is determined that T = 1.3 μsec. Further, as will be described later, the VHS type CR de-emphasis circuit 14 in FIG. 1 often uses a circuit as shown in FIG. 6, and as is well known, the CR pre-emphasis circuit 6 and the C pre-emphasis circuit 6 are used.
By using it together with the R de-emphasis circuit 14, the S / N of the demodulated video signal is improved and the frequency characteristic thereof is kept flat.

There are substantially the following three combinations of switching of the switching circuits 3 and 16 in FIG. That is, 1. When both the switching circuits 3 and 16 are closed on the side of the a terminal: This is because the magnetic tape 10 has the same standard as this embodiment, but does not have the pre-emphasis circuit 2 shown in FIG. The data is recorded by the recording / reproducing apparatus of 1. and is reproduced. On this magnetic tape 10, a video signal processed by a CR pre-emphasis circuit having the same characteristics as the CR pre-emphasis circuit 6 is recorded, and the video signal reproduced from the magnetic tape 10 is C
Since it is processed by the R de-emphasis circuit 14, S / N
Is improved, and the frequency characteristic becomes flat.

2. When the switching circuit 3 closes to the b terminal side and the switching circuit 16 closes to the a terminal side: This is the magnetic tape 10 on which the video signal processed by the pre-emphasis circuit 2 in this embodiment is recorded. Is reproduced by another recording / reproducing apparatus having the same standard as this embodiment and having no de-emphasis circuit 15, or the same magnetic tape 10 is used in this embodiment with the switching circuit 16 closed to the a terminal side. It corresponds to either of the cases of reproduction. In this case, the S / N determined by the CR pre-emphasis circuit 6 and the CR de-emphasis circuit 14 based on the standard is improved.

In this case, the pre-emphasis circuit 2
The amount of emphasis due to the processing of 1 remains in the FM demodulation signal, but this amount of residual emphasis is about 2 dB, which is within the range of maintaining the compatible reproduction, and the pre-emphasis circuit 2 has a linear phase. Because it has characteristics,
Pre-shots and post-shots remain at the rising and falling portions of the reproduced video signal that remains high-frequency emphasized, which improves the resolution of the reproduced screen.

3. When both the switching circuits 3 and 16 are closed on the side of the terminal b: This is the case where the magnetic tape 10 on which the video signal processed by the pre-emphasis circuit 2 is recorded in this embodiment. This corresponds to the case of reproducing, processing the reproduced video signal in the de-emphasis circuit 15, and outputting. In this case, in addition to the improvement of the S / N determined by the CR pre-emphasis circuit 6 and the CR de-emphasis circuit 14 based on the standard, the S / N is further increased by 2d by the pre-emphasis circuit 2 and the de-emphasis circuit 15.
B is improved. Moreover, the high-frequency characteristics of the video signals whose high-frequency characteristics are emphasized by the pre-emphasis circuit 2 and the CR pre-emphasis circuit 6 at the time of recording are suppressed by the de-emphasis circuit 15 and the CR de-emphasis circuit 14, respectively. A video signal having a flat frequency characteristic is obtained at the output terminal 15.

Although the CR pre-emphasis circuit 6 is provided after the clamp circuit 5 in FIG. 1, it may be provided before the clamp circuit 5 or immediately after the input terminal 1. Similarly, the CR de-emphasis circuit 14 may be arranged at the subsequent stage of the switching circuit 16.

The present invention is not limited to the magnetic recording / reproducing apparatus, but may be another recording / reproducing apparatus such as a video disk.

[0028]

According to the present invention, as described above,
Since it is configured, there is an effect as described in the following case. That is: 1. When recording is performed via the new pre-emphasis circuit according to the present invention and is reproduced without passing through the de-emphasis circuit according to the present invention, the CR pre-emphasis circuit based on the standard and the CR pre-emphasis circuit based on the standard are also used. The S / N determined by the circuit is improved, and the FM
Due to the emphasis characteristic existing in the demodulated signal, the resolution of the reproduction screen can be improved within the range of maintaining the compatible reproduction.

2. When recording via the new pre-emphasis circuit of the present invention and reproducing via the new de-emphasis circuit of the present invention, it is based on the same standard as the CR pre-emphasis circuit based on the standard. In addition to the S / N improvement determined by the CR de-emphasis circuit, the S / N is further improved by about 2 dB by the new pre-emphasis circuit and the new de-emphasis circuit according to the present invention. Moreover, the high-frequency characteristics of the video signal emphasized by these pre-emphasis circuits at the time of recording are completely suppressed by the de-emphasis circuits at the time of reproduction, and a video signal having a flat frequency characteristic can be obtained. ..

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an information signal recording / reproducing apparatus according to the present invention.

FIG. 2 is a block showing a specific example of the pre-emphasis circuit 2 in FIG.

3 is a circuit diagram showing a specific example of a filter circuit 2a in FIG.

4 is a block diagram showing a specific example of the de-emphasis circuit 15 in FIG.

5 is a circuit diagram showing a specific example of a CR pre-emphasis circuit 6 in FIG.

6 is a circuit diagram showing a specific example of the CR de-emphasis circuit 14 in FIG.

[Explanation of symbols]

 1 Input Terminal 2 Pre-emphasis Circuit 3 Switching Circuit 6 CR Pre-emphasis Circuit 7 FM Modulation Circuit 9 Recording Head 10 Magnetic Tape 11 Playback Head 13 FM Demodulation Circuit 14 CR De-emphasis Circuit 15 De-emphasis Circuit 16 Switching Circuit 18 Output Terminal

Claims (4)

[Claims] 1. An input information signal is supplied, and a transfer function is {1 + Ksin ² (ωT)} · exp (-2ST) where ω: angular frequency of information signal S: complex angular frequency (S = jω) T: delay Time K, N: a first pre-emphasis means having a maximum gain of N dB, which is approximately represented by a real number equal to or more than 0, and an information signal processed by the first pre-emphasis means,
Switching means for selecting one of the information signals not processed by the first pre-emphasis means, and second for enhancing high frequency characteristics of the information signal from the switching means.
Pre-emphasis means, means for recording the information signal processed by the second pre-emphasis circuit on a recording medium, means for reproducing the information signal from the recording medium, and suppression of high frequency characteristics of the reproduced signal. The first de-emphasis means and the transfer function is {1-Ksin ² (ωT)} · {1-K ² sin ⁴ (2ωT)}
Second de-emphasis means for approximating exp (-6ST) and processing the reproduction information signal processed by the first de-emphasis circuit; and output information signals of the first and second de-emphasis means. And a second switching means for selecting any one of the above. 2. The filter means according to claim 1, wherein the first pre-emphasis means is supplied with the input information signal and a transfer function is approximately expressed by Ksin ² (ωT) · exp (−2ST). An information signal recording / reproducing apparatus comprising: a delay means for delaying the input information signal by a time of 2T; and an adder means for adding the output information signal of the filter means and the output information signal of the delay means. .. 3. The reproduction information signal processed by the first de-emphasis means is supplied to the ^second de-emphasis means, and the transfer function has a transfer function of Ksin ² (ωT) · exp (−2ST). ), A first filter means, a first inverting amplifier means for inverting the output information signal of the first filter means, and a reproduction information signal processed by the first de-emphasis means. First delaying means for adding the output information signal of the first inverting amplifying means and the output information signal of the first delaying means, and output information of the first adding means Second filter means, which takes a signal as an input and whose transfer function is approximately represented by K ² sin ⁴ (2ωT) · exp (−4ST), and a second inversion which inverts an output information signal of the second filter means. Amplification means, and Second delaying means for delaying the output information signal of the first adding means; and second adding means for adding the output information signal of the second inverting amplifying means and the output information signal of the second delaying means. An information signal recording / reproducing apparatus comprising: 4. The information signal recording / reproducing apparatus according to claim 1, 2 or 3, wherein N is 3 or less.