JPH0795533A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent optimum picture quality from being damaged by deciding whether or not picture quality correction is loaded corresponding to the noise level of a video signal and switching whether a picture quality correction control signal is supplied to the respective circuits of a reproducing system or not at a switch circuit. CONSTITUTION:A regenerative FM wave outputted from a head amplifier 1 is supplied to an envelope detection circuit 2. Corresponding to a detected output level, a DC voltage generator 3 for control outputs a signal for control. A double limiter circuit 5, noise canceler circuit 8, Y noise reduction or line term circuit 9 and picture tone circuit 10 are controlled by the control signal. A noise detection circuit 12 extracts only the noise component from the video signal after the FM wave demodulation. A comparator 13 compares the level of the extracted noise component with a previously set reference level. Corresponding to the control signal from the comparator 13, a switch circuit 14 switches the control signal from the DC voltage generator for control.

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, and more particularly, it controls whether or not image quality correction is performed according to the noise level of a video signal, and sends the image quality correction control signal to each circuit of the reproducing system. The present invention relates to a magnetic recording / reproducing apparatus in which optimum image quality is not impaired by switching a switch circuit as to whether or not to supply.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional magnetic recording / reproducing apparatus. In the figure, 21 is a head amplifier, 22 is an envelope detecting circuit, 23 is a control DC voltage generator, and 24 is a reproducing FM wave equalizer (EQ). ) Circuit, 25 is a double limiter circuit, 26 is a demodulator, 27 is a de-emphasis circuit, 2
Reference numeral 8 is a noise canceller (NC) circuit, 29 is a Y (luminance signal) noise reduction (NR) circuit or line correlation circuit, 30 is a picture tone circuit, and 31 is a MIX circuit.

The signal from the magnetic head is sent to the head amplifier 21.
Playback F input to the head amplifier 21 and output from the head amplifier 21.
The M wave is supplied to the reproduction FM wave equalizer circuit 24 and the envelope detection circuit 22. The envelope detection output is then fed to the control DC voltage generator 23.
The image quality correction control signal is output according to the envelope detection output level. The output control signals are respectively supplied to the reproduction FM equalizer circuit 24, the double limiter circuit 25, the noise canceller circuit 28, the Y noise reduction circuit or line correlation circuit 29, and the picture tone circuit 30, and the image quality is corrected.

For example, in the reproduction FM equalizer circuit 24, when a control signal for strong correction (correction of image quality in the direction of blur) is applied, the frequency characteristic of the reproduction FM wave in the high range (around 4.0 to 5.0 MHz) is improved. If a control signal for weak correction (correction of image quality in the hard direction) is added, the frequency characteristic of the low frequency band (around 3.0 to 4.0 MHz) of the reproduced FM wave is slightly increased. Operate. This is to prevent a reversal phenomenon (black ghosting) when the envelope of the reproduced FM wave is in the direction in which it is small.

The double limiter circuit 25 also functions to prevent inversion noise. For example, when a strong correction control signal is applied, the double limiter circuit 25 operates to raise the level of the FM wave after passing through the high pass filter, and after passing through the limiter. Inversion noise is prevented by changing the MIX ratio with the low-pass filter side so that the high-frequency side is increased. Also, when a weak correction control signal is added, it operates so as to slightly raise the level of the FM wave after passing through the low-pass filter side, and after performing MIX with the high-pass filter side, a limiter is applied and 2 MHz of the demodulated video signal is applied. It works to improve the frequency characteristics in the vicinity.

In the noise canceller circuit 28, in the case of the control signal for strong correction, the frequency characteristic is changed so that the frequency moves to the low range and the amount of down increases, and conversely, in the case of the control signal for weak correction, the frequency is slightly changed. Moves to the high range and works to reduce the amount of down a little. The Y noise reduction circuit or the line correlation circuit 29 works to increase the amount of noise component subtracted from the main signal in the case of the strong correction control signal, and in the case of the weak correction control signal, the noise component subtracted from the main signal. Works to reduce the amount slightly.

The image quality improvement correction by the correction control signal in the noise canceller circuit 28 and the Y noise reduction circuit or the line correlation circuit 29 is the improvement of the S / N ratio. In the picture tone circuit 30, in the case of a strong correction control signal,
The image quality is changed toward softening, and in the case of the weak correction control signal, the image quality is changed toward slightly hardware so that the frequency characteristic is slightly increased.

[0008]

As described above, in the conventional magnetic recording / reproducing apparatus, when the envelope of the reproducing FM wave becomes small, the image quality is corrected by the control signal without fail. For example, the SP of recording 30/32 μm head width is used. Mode (58
When a tape recorded with a track width of (μm) is reproduced with a head width of 58 μm, if the envelope is small, strong correction (correction in the direction of image blur) is applied even if the S / N and the image quality (f characteristic, etc.) are not bad. , As a result, the optimum image quality was lost.

The present invention has been made in view of the above circumstances, and determines whether to apply image quality correction based on the noise level of the video signal and supplies the image quality correction control signal to each circuit of the reproduction system. An object of the present invention is to provide a magnetic recording / reproducing apparatus in which the optimum image quality is not impaired by switching whether or not it is a switch.

[0010]

In order to achieve the above object, the present invention controls based on an envelope detection circuit to which a reproduced FM wave output from a head amplifier is supplied and a detection level of the envelope detection circuit. A control DC voltage generator that outputs a signal, a double limiter circuit controlled by a control signal from the control DC voltage generator, a noise detection circuit that extracts only a noise component from the demodulated video signal, and the noise A comparator that outputs a control signal by comparing the noise component level from the detection circuit with a preset reference level, and a switch circuit that switches the control signal from the control DC voltage generator according to the control signal from the comparator. It consists of and.

[0011]

The control DC voltage generator generates a control voltage according to the envelope output level detected by the envelope detection circuit, while the reproduced FM wave, after passing through the demodulator, receives only the noise component from the video signal by the noise detection circuit. The extracted noise component is compared with a preset reference level, and when it is below the reference level, a control signal for turning off the switch circuit for switching the control voltage is output by the comparator. Also, the switch circuit is normally O
If the noise component is N or higher than the reference level, the control signal is not supplied from the comparator to the switch circuit.

[0012]

Embodiments will be described below with reference to the drawings. 1 (a) and 1 (b) are block diagrams for explaining an embodiment of a magnetic recording / reproducing apparatus according to the present invention, in which 1 is a head amplifier, 2 is an envelope detection circuit, and 3 is a head amplifier.
Is a control DC voltage generator, 4 is a reproduction FM wave equalizer (E
Q) circuit, 5 double limiter circuit, 6 demodulator, 7 de-emphasis circuit, 8 noise canceller (NC)
Circuit, 9 Y (luminance signal) noise reduction or line correlation circuit, 10 picture tone circuit, 11 MI
X circuit, 12 is a noise detection circuit, 13 is a comparator, and 14 is a switch circuit. Note that, a specific circuit example of the noise detection circuit is shown in FIG.

The reproduced FM wave output from the head amplifier 1 is supplied to the reproduced FM wave (equalizer) circuit 4 and the envelope detection circuit 2. The envelope detection output is then input to the control DC voltage generator 3, where the envelope detection output level is changed according to the envelope detection output level.
When the level is low, the image quality strong correction control signal is output, and when the level is high, the image quality weak correction control signal is output. Thereafter, the output control signal is supplied to the switch circuit 14, and each of the reproduction FM equalizer circuit 4, the double limiter circuit 5, the noise canceller circuit 8, the Y (luminance signal) noise reduction or line correlation circuit 9, and the picture tone circuit 10 is supplied. The control signal is supplied to the circuit to control the characteristics of each circuit.

On the other hand, after the reproduced FM wave passes through the demodulator 6, only the noise component is extracted from the video signal by the noise detection circuit 12, and the extracted noise component is compared with a preset reference level to obtain a reference level. In the following cases, the comparator 1 outputs a control signal that turns off the switch circuit 14 that switches whether to supply the control signal to each circuit.
3 outputs. On the contrary, when the noise level is higher than the reference level, the control signal is not output from the comparator 13 to the switch circuit 14.

With such a configuration, in the prior art, if the reproduced FM wave envelope is small, the image quality is always corrected by the control signal, whereas in the present invention, even if the envelope is small, the S / N is not bad. Nevertheless, it has a function of improving that the strong correction is applied, and determining whether or not to apply the image quality correction by the control signal based on the noise level of the video signal.

[0016]

As is apparent from the above description, the present invention has the following effects. That is, in the prior art, when a tape in which the reproduced FM wave envelope is small and the S / N image quality is not bad is played back, it depends on the determination of the envelope level, so that strong correction (image quality deterioration, forced correction in the blur direction) is performed. In contrast to this, the optimum image quality is impaired, but in the present invention, it is determined whether or not the image quality correction is performed based on the noise level of the video signal, and whether or not the image quality correction control signal is supplied to each circuit of the reproduction system is determined. By switching by the switch circuit, the optimum image quality is not deteriorated by the inverse strong correction unlike the conventional case.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

1 ... Head amplifier, 2 ... Envelope detection circuit, 3 ... Control DC voltage generator, 4 ... Reproduction FM wave equalizer (EQ)
Circuit, 5 ... Double limiter circuit, 6 ... Demodulator, 7 ... De-emphasis circuit, 8 ... Noise canceller (NC) circuit, 9 ... Y (luminance signal) noise reduction or line correlation circuit, 10 ... Picture tone circuit, 11 ... MIX
Circuit, 12 ... Noise detection circuit, 13 ... Comparator, 14 ... Switch circuit.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area H04N 5/7826

Claims (1)

[Claims] 1. An envelope detection circuit to which a reproduced FM wave output from a head amplifier is supplied, a control DC voltage generator that outputs a control signal based on a detection level of the envelope detection circuit, and the control DC. A double limiter circuit controlled by a control signal from a voltage generator, a noise detection circuit that extracts only the noise component from the demodulated video signal, and the noise component level from the noise detection circuit is compared with a preset reference level And a switch circuit for switching the control signal from the control DC voltage generator according to a control signal from the comparator, and a magnetic recording / reproducing apparatus.