JPS6141284A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To always have flat reproduction frequency characteristics by sampling a part where a reference signal is fitted and recorded out of a reproduction signal to give the wave detection to said part and to feed it back to a frequency characteristic varying means and giving control to secure a fixed reproduction level of the reference signal. CONSTITUTION:The reproduction video signal is supplied to a gate circuit 27 from a de-emphasis circuit 24, and the reference signal applied in a record mode is sampled out of the reproduction video signal by a gate pulse. The sampled reproduction reference signal undergoes the peak wave detection through a wave detecting circuit 26 and is held to be converted into a DC component according to the amplitude of the reproduction reference signal. The wave detection output is fed back to a variable frequency characteristic circuit 21, and the reproduction level of the reference signal of 3.58MHz is fixed. The reproduction video signal controlled to a fixed level is sent to a blanking circuit 32 so that the reference signal part of the video signal is deleted. Then the reproduction video signal is delivered in the form of a luminance signal output.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing device that records and reproduces luminance signals and color signals on separate tracks.

Conventional configuration and its problems Composite color television signals are directly FM modulated and recorded.
In the so-called direct FM recording method for playback, frequencies near the upper limit of the playback frequency band are included in the input signal as bursts and subcarriers, and this occurs due to variations in the frequency characteristics of the video head, azimuth differences between the video heads, etc. , the unbalance of frequency characteristics between channels during playback and the flatness of playback frequency characteristics due to differences between recording tapes are manually adjusted for each playback head each time using the burst and subcarrier playback levels as a guide. was.

In addition, in recent years, due to advances in recording media and video heads, and the development of new recording methods, methods that can record and reproduce high quality video signals at low relative speeds have been developed and put into practical use.

In this case, since the relative speed is low, it is not possible to adopt the above-mentioned direct FM method, so the color composite signal is divided into a luminance signal and two component color signals, each frequency modulated, and the FM luminance A so-called Y/C separated track recording method is used in which a signal is simultaneously recorded on one track and two FM component color signals are recorded on another track. In this method,
In particular, it serves as a reference for the flatness of the frequency characteristics of the luminance signal, which is important for determining the playback image quality. is likely to occur.

Therefore, as a means to prevent this, there is a problem in that the reproduction frequency characteristics must be managed each time using a reference tape on which multi-burst or sweep signals are recorded.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and is aimed at solving the difference in playback frequency characteristics caused by the difference in frequency characteristics of the video head, the difference in azimuth, etc. in the Y/C separated track recording system.
Another object of the present invention is to provide a magnetic recording and reproducing device that can automatically correct differences in frequency characteristics between channels and always keep reproduction frequency characteristics flat.

Structure of the Invention In order to achieve the above object, the magnetic recording and reproducing apparatus of the present invention uses a signal having a frequency near the upper limit of the reproduction frequency bandwidth as a reference signal during part of the vertical blanking period or the horizontal blanking period during recording. a reference signal inset means for inset recording at a constant level; a frequency characteristic variable means disposed in a reproducing circuit system; and a portion of the reproduced signal in which the reference signal is inset and recorded is extracted and detected, and then fed back to the frequency characteristic variable means. and feedback means for controlling the reproduction level of the reference signal to be constant.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram of a recording system of a luminance signal channel of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG. 1, and FIG. FIG. 4 is a circuit block diagram of a reproduction system of a luminance signal channel of a magnetic recording and reproducing apparatus according to an embodiment of the invention.
FIG. 3 is a signal waveform diagram of each part of the circuit shown in the figure.

In Figure 1, (1) is a buffer amplifier, (2) is a clamp circuit, (3) is a mixing circuit, (4) is a sync signal separation circuit, (5) is a vertical sync signal separation circuit, and (6) is a counter. , (7) is a pulse shaping circuit, (8) is a gate circuit,
(9) is a 3.58M1lz oscillation circuit, (10) is a pre-emphasis circuit, (11) is a white clip and dark clip circuit, (12) is an FM modulation circuit, (13) is a
) (14) is a recording amplifier circuit, (15) and (16) are magnetic heads. The input luminance signal is supplied to a clamp circuit (2) and a synchronization signal separation circuit (4) through a buffer amplifier (1). The output of the synchronization signal separation circuit (4) is supplied to a counter (6) to count the number of horizontal synchronization signals, but the counter (6) is reset by the vertical synchronization pulse from the vertical synchronization signal separation circuit (5). , a horizontal scanning section located at a fixed time position from the vertical synchronizing signal is selected, shaped by a pulse shaping circuit (7), and supplied to a gate circuit (8). On the other hand, 3.58M)Iz
The output of the oscillation circuit (9) is supplied to the gate circuit (8), and the gated frequency of 3.58 MHz is outputted only for a predetermined period of time. This gate circuit (
The output signal of 8) is inserted into the input signal clamped by the clamp circuit (2) in the mixer circuit (3), passes through the pre-emphasis circuit (10) and the white clip and dark clip circuit (11), and is subjected to FM modulation. Circuit (12)
and frequency modulated. FM modulation circuit (12)
The FM output is power amplified by recording amplifier circuits (13) and (14), and is then sent to a magnetic head (15) for recording the luminance channel.
(16) is recorded on the magnetic tape.

Figure 2 shows the waveforms with the vertical blanking period expanded. (a) is the input waveform of the luminance signal, (b) is the output waveform of the pulse shaping circuit (7), and (C) is the waveform gated by the gate pulse. The output waveform of the gate circuit (8), which is the signal of 3,58M) lz, (d) is the gated 3,58M
)lz signal is mixed within the 19th horizontal scanning period.

FIG. 3 shows the reproduction system of the luminance signal channel.

(17) (18) is a magnetic head, (19) (20)
is a regenerative amplifier circuit, (21) is a variable frequency characteristic circuit, (2
2) is a limiter circuit, (23) is an FM demodulation circuit, and (24) is a limiter circuit.
) is a de-emphasis circuit, (25) is an output amplification circuit,
(26) is a detection circuit, (27) is a gate circuit, (28)
(29) is a counter, (30) is a vertical synchronization signal separation circuit, (31) is a synchronization signal separation circuit, and (32) is a blanking circuit. A reproduction signal from the reproduction magnetic head (17) (18) passes through reproduction amplifier circuits (19) (20) and is supplied to a variable frequency characteristic circuit (21) comprising, for example, a cosine collector circuit. The output passes through a limiter circuit (22) and an FM demodulation circuit (23), and then a de-emphasis circuit (23).
4) and is supplied to the output amplifier circuit (25). On the other hand, the de-emphasized reproduced video signal is supplied to a synchronization signal separation circuit (31), and a counter (29) counts horizontal synchronization signals. Further, this counter (29) is reset by a vertical synchronizing signal from a vertical synchronizing signal separation circuit (30), and a horizontal scanning section at a predetermined time position from the vertical synchronizing signal is selected and shaped by a pulse shaping circuit (28). The gate pulse is output,
Goo 1 - is supplied to the circuit (27). On the other hand, the gate circuit (27) is supplied with the reproduced video signal from the de-emphasis circuit (24), and the reference signal inserted during recording is extracted from the reproduced video signal by the gate pulse. The extracted reproduced reference signal is subjected to peak detection and held by a detection circuit (2G), and converted into a DC component according to the amplitude of the reproduced reference signal. This detection output is output from the variable frequency characteristic circuit (
21), and operates so that the reproduction level of the 3.58 MHz reference signal is kept at a constant level. Through such an operation, the reproduced video signal whose reference signal is controlled to be at a constant level has the reference signal portion removed by the blanking circuit (32) and is output as a luminance signal output.

FIG. 4 shows an enlarged waveform diagram of the vertical blanking period, (,) is the output waveform of the de-emphasis circuit (24),
(b) is the output waveform of the pulse shaping circuit (28), (c) is the reproduced reference signal waveform gated by the gate circuit (27), and (d) is the luminance with the reference signal removed by the blanking circuit (32). This is the signal output waveform.

In this way, by automatically correcting the reproduced reference signal to a predetermined level, the reproduced frequency characteristics can always be kept flat.

In this example, the reference signal is 3.58MHz.
However, there is no particular limitation as long as the frequency is near the upper limit of the reproduction frequency band.

Furthermore, in this embodiment, an example has been described in which the reference signal is inserted into the 19th horizontal scanning period within the vertical blanking period, but the present invention is not limited to one horizontal scanning period, and a plurality of horizontal scanning periods may be used. . Furthermore, a similar reference frequency may be superimposed as a burst during the horizontal blanking period.

Further, in this embodiment, an example of a luminance signal channel has been described, but it goes without saying that a similar method can be applied to a chroma signal as well.

As described in detail, according to the present invention, since the reproduced reference signal is automatically corrected to a predetermined level, the reproduced frequency characteristic can always be kept flat.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a recording system of a luminance signal channel of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG. 1, and FIG. FIG. 4 is a circuit block diagram of a reproducing system of a luminance signal channel of a magnetic recording and reproducing apparatus in one embodiment. FIG. 4 is a signal waveform diagram of each part of the circuit shown in FIG. 3. (3)...Mixing circuit, (4)(31)...Synchronizing signal separation circuit, (5)
(30)...Series synchronization signal separation circuit. (6) (29)...Counter, (7) (28)
...Pulse shaping circuit.

Claims (1)

[Claims] 1. Reference signal inset means for inset recording a signal having a frequency near the upper limit of the reproduction frequency bandwidth as a reference signal at a certain level in a part of the vertical blanking period or the horizontal blanking period during recording; and a feedback means for extracting and detecting a portion in which the reference signal is embedded and recorded from the reproduced signal and then feeding it back to the frequency characteristic varying means, so that the reproduction level of the reference signal is constant. A magnetic recording and reproducing device configured to control the magnetic recording and reproducing apparatus.