JPH1186432A - Magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make image quality improvement effective for visual sensation by controlling the frequency characteristic of an equalizer circuit by the multiplied output of the output meeting the amplitude level of a regenerative video FM signal and the output meeting the spread of an FM demodulated luminance signal frequency band. SOLUTION: The video FM signal inputted to an FM equalizer circuit 2 is subjected to the correction of its frequency characteristic and is inputted to an FM demodulation circuit 3. The demodulated luminance signal is passed through a deemphasis circuit 4 and is then inputted to a luminance signal detecting circuit 6 which converts the frequency band of the luminance signal to a DC voltage. The output thereof is inputted to one input side (b) of a multiplier circuit 7. On the other hand, the signal converted to the DC voltage meeting the magnitude of the amplitude level of the FM signal in an envelope detecting circuit 8 by receiving the signal of a head amplifier 1 is inputted to another inlet side (a) of the multiplier circuit 7. The multiplier circuit 7 outputs the voltage of (a-side input voltage × b-side input voltage)/k, where (k) is a constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus having an FM equalizer circuit, and more particularly to a means for improving image quality in a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art An example of image quality improving means in a conventional magnetic recording and reproducing apparatus will be described with reference to FIGS. FIG.
The video FM signal recorded on the magnetic tape 11 is picked up by the video head 12. The picked-up video FM signal is amplified by the head amplifier 1 and has an FM equalizer circuit 2 having a lower sideband variable function by a DC voltage (in this case, the higher the DC voltage, the higher the lower sideband is emphasized). , And after being corrected in frequency characteristics, is input to the FM demodulation circuit 3. The luminance signal demodulated by the FM demodulation circuit 3 is input to a detection circuit 6 after passing through a de-emphasis circuit 4, and is converted into a DC signal f corresponding to the frequency band e of the luminance signal (in this case, the luminance signal The characteristic of outputting a higher voltage as the frequency band is narrower is shown). And FM equalizer 2
Is the output DC voltage f of the detection circuit 6.
Variable control.

A video FM signal in which the lower sideband is emphasized by the FM equalizer 2 is demodulated as a luminance signal in which a high band of a base band is emphasized when FM demodulation is performed, and thereafter, a demodulation (luminance) signal processing circuit The signal is output to the output terminal via the terminal 5. In this conventional magnetic recording / reproducing apparatus, the head amplifier circuit 1 includes the recording / reproducing amplifier IC 9 and
An FM equalizer circuit 2, an FM demodulation circuit 3, a de-emphasis circuit 4, and a
The luminance signal processing circuit 5 uses a circuit built in the video signal processing IC 10.

Here, a VHS video tape recorder will be described as an example. In FIG. 4, a frequency characteristic e of a signal after being FM-demodulated and passed through a de-emphasis circuit 4 is up to a high frequency range as indicated by e1. When it is extended, the output voltage f of the detection circuit 6 becomes a low value like f1, and
The frequency characteristic g1 of the M equalizer circuit 2 does not change. Therefore, the frequency characteristic after the FM modulation, that is, the video output h1 does not change. Conversely, when the frequency characteristic e of the 78th pin output falls in the high range as shown by e2, the output voltage f of the detection circuit 6 becomes a high value as shown by f2, and the frequency characteristic g2 of the equalizer circuit 2 is shown in FIG. And the frequency characteristic h2 of the video output h is such that the high range is emphasized. That is, in this case, the high frequency range is extended by the detection circuit 6 to improve the resolution of the reproduced video on the screen.

The characteristics g1 and g of the frequency characteristic g shown in FIG.
2 schematically shows an example of the static characteristics of the FM equalizer circuit 2 alone, and does not show the frequency spectrum of the FM signal itself reproduced from the tape. The characteristics e1 and e2 of the frequency characteristic e of the luminance signal schematically show an example of the baseband luminance signal spectrum after FM demodulation.

Another prior art is disclosed in, for example,
As disclosed in JP-A--18755 and JP-A-6-150538, the amplitude of a reproduced FM signal is detected.
A method of controlling the frequency-amplitude characteristics of the equalizer circuit only from the detected value, and a method of controlling the carrier frequency component of the FM modulation of the FM-modulated reproduction signal and the sideband of the FM modulation disclosed in Japanese Patent Application Laid-Open No. 2-263359. There is a type in which the frequency-amplitude characteristic of an RF equalizer is made variable based on a frequency component comparison output and an output obtained by detecting the envelope level of the reproduction signal.

[0007]

In the conventional magnetic recording / reproducing apparatus described with reference to FIGS. 3 and 4, for example,
When the playback output from the video head is a small signal, FM
The luminance signal after demodulation has a poor S / N ratio as compared with the case where the reproduced signal is large, and further attempts to enhance the resolution of the luminance signal by enhancing the lower band with a DC voltage corresponding to the frequency band of the luminance signal. Therefore, a phenomenon that the S / N is further deteriorated occurs. That is, when the reproduction output from the video head is small, the advantage of improving the resolution in the viewing angle can be obtained, but there is a problem that the S / N degradation occurs.

[0008] JP-A-2-18755, JP-A-6-1994
In the device disclosed in JP-A-150538, the frequency-amplitude characteristic of the equalizer circuit is controlled only by the amplitude detection value of the reproduced FM signal, and it is difficult to control the equalization effect to be optimal. JP-A-2-2633
In Japanese Patent No. 59, separate control is performed by using an amplitude detection value of a reproduced FM signal and a frequency band detection comparison signal output.
It is difficult to optimally control the correction effect, and there is a problem that the circuit scale and the characteristic adjustment become complicated if the optimal control is performed.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a magnetic recording / reproducing apparatus which can obtain a visually effective image quality improving effect with a simple structure, and more specifically, a reproducing FM signal in addition to an improvement in resolution. And S / S depending on the level of
An object of the present invention is to provide a magnetic recording / reproducing apparatus capable of automatically controlling the balance of N so as to be optimal, thereby solving the problems of the prior art. According to a first aspect of the present invention, in a magnetic recording / reproducing apparatus having an equalizer circuit for correcting a frequency characteristic of a reproduced video FM signal and an FM demodulation circuit, an output corresponding to the amplitude level of the reproduced video FM signal and FM demodulation are performed. This is a magnetic recording / reproducing apparatus that controls the frequency characteristics of an equalizer circuit by multiplying an output according to the spread of the luminance signal frequency band.

According to a second aspect of the present invention, there is provided a magnetic recording / reproducing apparatus having an equalizer circuit for correcting a frequency characteristic of a reproduced video FM signal and an FM demodulation circuit.
Envelope detection means for the reproduced video FM signal, frequency band detection means for the FM demodulated luminance signal, multiplication means for multiplying the output of the envelope detection means and the output of the frequency band detection means, and the frequency characteristics of the equalizer circuit by means of the multiplication means output And means for controlling the

In the present invention, the output (a) of the detection circuit for converting the amplitude level of the video FM signal into a DC voltage and the output (a) of the detection circuit for converting the luminance signal after the FM demodulation into a DC voltage corresponding to the frequency band. b) is input to a multiplier circuit, and the output voltage value (c) = {(a) × (b)} / k is input to an FM equalizer circuit capable of variably controlling the level of the lower sideband of the video FM signal. Accordingly, when the amplitude level of the video FM signal is small, (a) × (b) becomes small, so that the output of the multiplication circuit is lower than the output voltage when only the conventional video frequency detection circuit is used. It operates in the direction to decrease the emphasis amount of the sideband. Conversely, when the amplitude level of the video FM signal is large, (a) × (b) becomes large,
The output of the multiplication circuit becomes almost the same as the output voltage when only the conventional video frequency detection circuit is used, and the enhancement of the lower sideband can be increased.

[0012]

1 and 2 show an embodiment of the present invention.
Will be described with reference to FIG. In FIG. 1, the same parts as those of the conventional magnetic recording / reproducing apparatus shown in FIG. 3 are denoted by the same reference numerals. The video FM signal recorded on the tape 11 is picked up by the video head 12 and
Amplified by The amplified signal is output from the output terminal 30 pin of the IC, and the frequency characteristic can be varied by the DC voltage.
The signal is input to pin 40 of the IC 10 in which the M equalizer circuit 2 is built. At the same time, from the head amplifier IC9,
A signal converted into a DC voltage according to the amplitude level of the FM signal by the envelope detection circuit 8 in the head amplifier IC is output from pin 27. FM equalizer circuit 2
Are input to the FM demodulation circuit 3 after their frequency characteristics are corrected there. The demodulated luminance signal passes through a de-emphasis circuit 4 and is then input to a detection circuit 6 that converts the frequency band of the luminance signal into a DC voltage. The output voltage of the detection circuit is then input to one input side b of the multiplication circuit 7. The other input a of the multiplication circuit 7
Is input with the DC voltage generated by the envelope detection circuit 8 in the head amplifier IC 9 described above.

The multiplying circuit 7 operates to output a voltage of {(a) × (b)} / k (k is a constant value) from the voltage of the input (a) and the voltage of the input (b). When the level of the FM signal is low, that is, when the output of the head amplifier is low (when the S / N of the reproduced luminance signal is low), the voltage of (a) becomes low, and the value of (a) × (b), that is, the output The voltage is also reduced, and the amount of low-frequency enhancement of the FM equalizer is small. As a result, the high-frequency characteristics of the luminance signal after the FM modulation do not increase so much, and the apparent S / N deterioration is reduced.
Conversely, when the level of the video FM signal is large (the S / N of the reproduced luminance signal is good), the voltage of (a) becomes high,
Since the value of (a) × (b) increases, and the value (c) of the output voltage increases, the amount of low-frequency enhancement of the FM equalizer increases, and as a result, the luminance signal after FM demodulation has a high level. The frequency characteristics of the region are improved, and the resolution is improved.

FIG. 2 exemplifies the voltage values of the terminals a, b, c of the multiplying circuit 7. The multiplication circuit 7 calculates the input voltage value (a)
And the value of the input voltage (b) and the value of the output voltage (c)
A constant is set such that (c) = {(a) × (b)} / 5. Also, 0 <(a) <5 (volts), 0 <(b) <5
(Bolts), the multiplication circuit 7 and the detection circuit 8 are set. As shown by a1 and a2 in FIG. 2, when the voltage of the input (a) is high, that is, when the level of the video FM signal is high, (a) ≒ 5 (volts), so that (c) =
{(A) × (b)} / 5} (b), and the voltage (b) corresponding to the frequency characteristic of the demodulated luminance signal is output with almost the same value. This voltage is close to the value obtained with the conventional method.

Next, as shown by a3 and a4 in FIG. 2, when the voltage of the input (a) is low, that is, when the level of the video FM signal is low, (a) ≒ 0, and the FM equalizer 2 The amount of low-frequency enhancement hardly changes. Therefore, FM
Since the high-frequency characteristics of the demodulated luminance signal do not rise as in the prior art, there is no apparent deterioration in S / N. The multiplication circuit 7 shown in FIG. 1 can be implemented by a circuit using components such as a general-purpose IC.

[0016]

According to the present invention, an output of a detection circuit for converting a luminance signal subjected to FM demodulation into a DC voltage according to the spread of a frequency band and a detection circuit for converting a reproduced video FM signal into a DC voltage corresponding to the amplitude level of the signal. Since the frequency characteristic of the equalizer circuit is controlled by the output multiplied by the output of the circuit,
When the level of the reproduced video FM signal is low, that is, in the case of a reproduced signal having a poor S / N, an operation of suppressing the enhancement amount of the lower sideband is performed, and when the level of the reproduced video FM signal is high (when the S / N is good). Can increase the amount of enhancement of the lower sideband.
In other words, with a simple configuration, it is possible to automatically control the balance between the resolution and the S / N in accordance with the level of the reproduced FM signal, in addition to the improvement in the resolution, so as to optimize the balance.

[Brief description of the drawings]

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

FIG. 2 is an output diagram of the multiplication circuit shown in FIG.

FIG. 3 is a block diagram showing image quality improving means of a conventional magnetic recording / reproducing apparatus.

FIG. 4 is an output diagram at each of points e, f, g, and h in the block diagram shown in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Head amplifier, 2 ... FM equalizer circuit, 3 ... FM
Demodulation circuit, 4 ... De-emphasis circuit, 5 ... Luminance signal processing circuit, 6 ... Luminance signal detection circuit, 7 ... Multiplication circuit, 8 ... Envelope detection circuit, 9 ... IC for recording / reproduction amplifier, 10
... video signal processing IC, 11 ... magnetic tape, 12 ... video head.

Claims (2)

[Claims] 1. A magnetic recording / reproducing apparatus having an equalizer circuit for correcting a frequency characteristic of a reproduced video FM signal and an FM demodulation circuit, wherein an output corresponding to the amplitude level of the reproduced video FM signal and a luminance signal frequency band subjected to FM demodulation. A magnetic recording / reproducing apparatus for controlling a frequency characteristic of an equalizer circuit by a multiplied output with an output corresponding to the spread of the signal. 2. A magnetic recording / reproducing apparatus having an equalizer circuit for correcting a frequency characteristic of a reproduced video FM signal and an FM demodulation circuit, an envelope detector for the reproduced video FM signal, and a frequency band detection of the FM demodulated luminance signal. Means, multiplication means for multiplying the output of the envelope detection means and the output of the frequency band detection means, and control means for controlling the frequency characteristic of the equalizer circuit by the output of the multiplication means. Recording and playback device.