JPH01264652A - magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate a faint effect of an unnecessary component upon a regenerative signal and to obtain a high quality reproduced picture by providing a means for transmitting a signal by separating an earth voltage of the input and output respectively between a head changeover signal generating means and a head changeover means. CONSTITUTION:At the time of reproducing, signals reproduced by heads 11 and 12 are alternately selected by a changeover circuit 16 via amplifiers 14 and 15 to obtain their continuous signal. This is given to a digital signal circuit (reproducing system digital signal processor) 18 via an FM demodulation circuit 17 to be processed by converting its timing axis to be reverse to the settlement of redundant time tau of a recording digital signal processing circuit 4, and hence a continuous video signal is restored. A changeover reference signal (f) is generated by a reference signal generating circuit 20 with a tuck pulse (e) synchronized with a rotary cylinder 13 of the heads 11 and 12, and is latched with a specific signal (b) of the signal processing circuit 18 by a signal generating circuit 21 to generate a head changeover signal (c). This is passed through a light isolator 22 to remove the unnecessary component of the earth voltage to obtain a signal (d), with which a head changeover circuit 16 changes accurately the heads within the redundant time tau to prevent the reproducing video information from lacking. By this constitution, the reproducing picture is prevented from deteriorating in picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a helical scan type magnetic recording and reproducing device, and particularly to a magnetic recording and reproducing device equipped with a digital processing means for a reproduced signal.

[Conventional technology]

Conventional helical scan magnetic recording/reproducing device (hereinafter referred to as
In a VTR, two or more magnetic heads are used. During playback, these magnetic heads scan the magnetic tape in order to reproduce signals, and the reproduced signals from these magnetic heads are sequentially transferred to a head switching circuit. However, the head switching signal that controls the head switching circuit is, for example, as shown in Yokoyo's book [Introduction to VTR, published by Tokyo Denki University Press, p. 92-93].
It is formed by supplying a tack pulse synchronized with the rotational phase of the magnetic head to a delay circuit such as a monostable multivibrator. This head switching signal has a duty ratio of 5
A rectangular signal of 0% is used, and the reproduction signal of the valley magnetic head is selected according to its polarity (level).

On the other hand, in order to be able to record and play back broadband video signals,
A VTR that uses the so-called segment recording method, in which the valley field of the video signal is divided into multiple tracks for recording and playback.
There is also. In such a VTR, head switching in a head switching circuit is performed within a field period of a video signal. In this case, if there is a phase shift between the reproduced signals of each magnetic head, distortion (skew) will occur in the reproduced image at the head switching point. For this purpose, a digital time axis correction circuit is provided, which corrects the phase shift between the reproduction signals of each magnetic head.

This digital time axis correction circuit also switches the reproduction signal from each magnetic head within the redundant period for head switching provided between each segment in order to prevent the reproduction image information from being lost. Generates a head switching signal. This head switching signal is supplied to a head switching circuit.

The digital time base correction circuit performs skew correction within this redundant period.

[Problem to be solved by the invention]

By the way, the head switching signal generated by the digital time axis correction circuit and its ground potential include unnecessary components such as clock components used in this digital time axis correction circuit, and these unnecessary components are There is a problem in that this affects the minute reproduction signal selected by the switching circuit, and as a result, the quality of the reproduced image deteriorates.

It is an object of the present invention to provide a magnetic recording and reproducing device which eliminates such problems, eliminates the influence of the above-mentioned unnecessary components on minute reproduced signals, and makes it possible to obtain high-quality reproduced images. That's true.

[Means to solve the problem]

In order to achieve the above object, the present invention provides ground potential separation means between the head switching signal generation means and the head switching means for separating input and output ground potentials and transmitting signals.

[Effect]

The head switching signal is supplied to the head switching circuit via the ground potential separation means. According to this, the level difference of the head switching signal is transmitted, but since the ground potential is separated, the ground potential separation is Unnecessary components such as clocks generated in the digital processing circuit connected to the input side do not leak into the head switching signal outputted from the means, and a head switching signal with an excellent S/N ratio can be obtained. Therefore, the continuous reproduction signal obtained by switching the reproduction signal from each magnetic head using this head switching signal is not affected by the clock etc. in the digital processing circuit, and the final video signal is It will not be affected by that influence.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing device using a segment recording method according to the present invention, in which 1 is an input terminal for a video signal, 2 is an input terminal for a horizontal synchronizing signal, and 3 is a vertical synchronizing signal. 4 is a recording system digital signal processing circuit, 5 is a frequency modulation circuit, 6 is a recording amplifier, 7.8 is a magnetic head, 9 is a cylinder, 10 is a magnetic tape, +L
12 is a magnetic head, 10 is a cylinder, 14. 15 is a reproduction amplifier, 16 is a head switching circuit, 17 is a frequency demodulation circuit, 18 is a reproduction system digital signal processing circuit, 19 is a video signal output terminal, 20 is a reference signal generation circuit, 21 is a head switching signal generation circuit, 22 is an optical isolator.

In the figure, a video signal input from an input terminal 1 is input to a recording system digital signal processing circuit 4. The recording system digital signal processing circuit 4 includes an A/D converter, a memory, and a D/D converter.
It is composed of an A converter, etc., and uses the horizontal synchronization signal input from input terminal 2 and the vertical synchronization signal input from input terminal 3 as a reference, performs processing such as changing the memory read timing, and converts the video signal into a recording signal. Convert to a and output.

This recording signal a is frequency modulated by a frequency modulation circuit 5, further amplified by a recording amplifier 6, and then is sent to a magnetic head 7.
．． 8 and recorded on the magnetic tape 10.

For example, when recording and reproducing a wideband video signal such as in a high-definition television system, the magnetic head 7.8 is used to increase the relative speed between the magnetic tape 10 and the magnetic head 7.8.
The cylinder 11 loaded with
Rotate with D Orpm. At this time, one field period of the recording signal a is divided into three tracks and recorded as shown in FIG. For this reason, in the playback screen, in order to be able to perform processing to eliminate discontinuous parts during 0 playback, in which discontinuous parts of the screen occur due to head switching at six places in one screen, in the recording system digital signal processing circuit 4, Intercostal axis conversion as shown in FIG. 6 is performed in advance.

That is, in the recording system digital signal processing circuit 4,
The video signal input from input terminal 1 as shown in FIG. 6(a) is divided into six segments (A, B, C) for each field.
Furthermore, as shown in FIG. 3(b), the time axis is shifted in units of segments, and a redundant period τ for head switching is provided between each segment. As a result, as shown in Figure 2, each segment A, B,
C is recorded such that the redundancy period τ is located at the head switching point (shaded area in the figure) on the track on the tape.

In FIG. 1, during reproduction, signals reproduced by magnetic heads 11 and 12 are supplied to a head switching circuit 16 via reproduction amplifiers 14 and 15, respectively, and are alternately selected to form continuous reproduction signals. This reproduced signal is frequency demodulated by a frequency demodulation circuit 17 and then input to a reproduction digital signal processing circuit 18 .

The recycled yarn digital signal processing circuit 18 is an A/D converter.

Memo 1c The recording system digital signal processing circuit 4 is configured with multiple D/A converters, etc., and performs time axis conversion, etc., which is opposite to that of the recording system digital signal processing circuit 4, and converts the input playback signal into a continuous video signal on the original time axis. is restored and output from the output terminal 19, and a head switching signal d is generated to control the head switching circuit 16 to accurately switch heads within the above-mentioned redundancy period τ so that the reproduced video information is not lost. It generates and outputs a head switching designation signal.

In order to generate this head switching signal d, the magnetic head 4
4. A tank pulse e that is synchronized with the rotational phase of the cylinder 3 carrying the head 12 is supplied to a head switching reference signal generating circuit 20 composed of a monostable multivibrator or the like to obtain a head switching reference signal f.

In the head switching signal generating circuit 21, the head switching signal C is generated and output by latching this head switching reference signal f with the head switching designation signal.

As shown in FIG. 4 (8), this head switching signal C contains unnecessary components such as a clock component used in the reproduction system digital processing circuit 18 at its ground potential, and this head switching signal C is By passing it through the isolator 22, a head switching signal d such as shown in FIG. 4(d) in which the arm potential does not contain unnecessary components can be obtained.

This switching signal d is supplied to the head switching circuit 16, which outputs the reproduction signal from the regenerative amplifier 14 shown in FIG. 4(a) and the reproduced signal from the regenerative amplifier 15 shown in FIG. 4(b). The head switching signal d is alternately switched within the redundant period τ, and a continuous reproduction signal as shown in FIG. Since no unnecessary components are mixed into the reproduced signal, and therefore unnecessary components are not demodulated by the frequency demodulation circuit 17, deterioration in the quality of the reproduced image can be avoided. Although the optical isolator 22 is used to remove the clock component in the reproduction digital signal processing circuit 18 contained in the ground potential of the switching signal C, the present invention is not limited to this. It is clear that other isolation means capable of separating the ground potential between input and output can be used, and in this case also the same effect as the above embodiment can be obtained.

Further, such an isolation means is provided between the reproduction system digital signal processing circuit 18 and the head switching signal generation circuit 21.
Alternatively, the object of the present invention can be achieved even if it is placed between the head switching reference signal generation circuit 20 and the head switching signal generation circuit 21, and the same effect as the above embodiment can be obtained.

Further, the isolation means may be provided between the head switching circuit 16 and the frequency demodulation circuit 17 or between the frequency demodulation circuit 1
7 and the reproduction system digital signal processing circuit 18, the ground potential of the digital system and the ground potential of the analog system are completely separated during reproduction, and the effect of a shielding layer can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to remove the influence of unnecessary components such as clock components generated in the digital signal processing circuit during reproduction on minute reproduced analog signals, and to obtain good reproduced image quality. It has the excellent effect of being able to

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a track pattern diagram on a magnetic tape in the segment recording method, and FIG. 3 is a recording system digital signal processing in FIG. 1. FIG. 4 is an explanatory diagram of the operation of the circuit. FIG. 4 is an explanatory diagram of the operation of the reproduction system in FIG. 1D "°゛Magnetic tape, N, 12...Magnetic head, 16...Head switching circuit, 18...Reproduction system digital signal processing circuit, 20...Reference signal generation circuit, 21...Head switching Signal generation circuit, 22...optical isolator. d), d1\
Me\cs -00? −\ha℃ [F] to −). 6 mountains

Claims (1)

[Claims] 1. In a magnetic recording and reproducing apparatus equipped with processing means for converting the reproduction signals of a plurality of magnetic heads into continuous reproduction signals by sequentially selecting them with a head switching circuit and digitally processing the continuous reproduction signals, the processing means a first means for outputting a switching designation signal and generating the head switching signal in response to the head switching designation signal; and a first means to which the head switching signal is supplied and transmits the signal by separating input and output ground potentials. A magnetic recording/reproducing apparatus comprising: a second means for switching the head, and supplying a head switching signal outputted from the second switching means to the head switching circuit.