JPH0410203A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent color inversion by eliminating unnecessary signals by delaying the output signal of a head amplifier circuit to the position of the unnecessary signal caused by a pseudo gap by a delay means, and adding the delayed signals after inverting the polarities. CONSTITUTION:A delay circuit 15, unnecessary signal eliminating circuit 16, system control part 17 and operation part 18 are provided, and the delay circuit 15 can be composed of a passive delay line, which is composed of a coil and a capacitor, or the CCD delay line of a semiconductor. For example shown in the figure using the CCD delay line of the semiconductor, the clock component of a CCD delay line 23 is eliminated by a signal input terminal 21, signal output terminal 22, CCD delay line 23 of the semiconductor and low-pass filter 24. A clock generating circuit 25 is provided and when the number of steps in the CCD delay line 23 is defined as N and time for one cycle of the clock is defined as (p), delay time T is expressed by T=Nx(p). On the other hand, a clock control input terminal 26 is provided and according to the state of this terminal 26, the oscillation frequency of the clock, namely, the time for one cycle can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the removal of unnecessary signals in a magnetic recording/reproducing device.

(Prior Art) An example of a conventional magnetic recording/reproducing device will be described with reference to a block diagram of a video floppy player shown in FIG.

51 is a video floppy disk, and 52 is a magnetic head.

53 is a spindle motor, 54 is a magnetic head moving mechanism centered on a stepping motor, 55 is a spindle motor circuit consisting of a control circuit and a drive circuit, and 56 is a stepping motor circuit consisting of a control circuit and a drive circuit. A head amplifier 57 amplifies the signal reproduced by the magnetic head. 58 is a bypass filter, 59 is a low-pass filter, 60 is a luminance signal FM demodulation circuit, 61 is a chrominance signal FM demodulation circuit, 62 is a luminance signal reproduction processing section, 63 is a chrominance signal reproduction processing section, 64 is a video output terminal, 65 is a system control section, and 66 is an operation section. As shown in Figure 6, the video floppy disk has frequency multiplexed FM signals including a luminance signal and a color signal, and one color signal consists of two color difference signals, R-Y and B-Y, which are switched for each horizontal scan. The line sequential signal is FM modulated, and the carrier frequency is 1.2 MHz for R-Y and 1.3 MHz for B-Y.
and the bandwidth is 2.5 MHz. The brightness signal has a sync chip of 7.7MHz and a white peak of 9.
It is 7MHz. Furthermore, a video floppy disk has 50 concentric tracks and can record 50 screens. This video floppy disk is rotated approximately 60 times per second by a spindle motor. The head movement mechanism is 50
It is used to construct a track, and moves the head in the radial direction of the disk. The magnetic head is an amorphous head called the MIG type, and FIG. 7 shows a schematic view of the head from the sliding surface. 71 is a gap, 72 is ferrite, 73 is amorphous, and 74 is glass. Compared to conventional ferrite heads, amorphous material is added to the gap to strengthen the magnetic flux. The head output signal is amplified by a head amplifier, a luminance signal component is extracted by a bypass filter, and a chrominance signal component is extracted by a low-pass filter. The FM demodulated luminance signal is subjected to signal processing such as de-emphasis, pseudo frame processing, synchronization separation, and two-color signal synthesis in a luminance signal reproduction processing circuit. On the other hand, the FM demodulated color signal is subjected to signal processing such as de-emphasis, intercolor temporalization, and color encoding in a color signal reproduction processing circuit.

(Problems to be Solved by the Invention) In the case of an MIG type amorphous head, in addition to a regular gap, a pseudo gap is formed at the interface between the ferrite and the amorphous, and unnecessary signals are reproduced. High-frequency luminance signals can be attenuated to a level that does not cause problems by making the shape of the boundary surface into a waveform, for example.
In the case of color signals, this unnecessary signal may cause undesirable phenomena such as color inversion. When the pulse waveform shown in FIG. 8(a) was recorded on a video floppy disk, the output of the magnetic head had a drawback that an unnecessary signal was generated due to a pseudo gap at the point where the output of the magnetic head was delayed from Δ as shown in FIG. 8(b).

An object of the present invention is to provide a magnetic recording and reproducing apparatus that eliminates this unnecessary signal to a level that causes no problem through circuit processing.

(l! Means for Solving the Problem) The magnetic recording and reproducing apparatus of the present invention includes a magnetic head for reproducing signals recorded on a recording medium, a head amplifier circuit, an FM
Video floppy disk recording/playback machine equipped with demodulation means and signal reproduction processing means (hereinafter referred to as video floppy playback machine)
A magnetic recording/reproducing device such as the above includes a delay means for delaying a head amplifier circuit output signal, and an unnecessary signal removing means for subtracting a predetermined level of the head amplifier circuit output signal and the delayed signal by the delay means to remove unnecessary signals. The signal that has passed through the signal removal means is input to the FM demodulation means.

(Function) According to the present invention, the head amplifier circuit output signal is delayed by the delay means to the position of the unnecessary signal due to the pseudo gap, and the unnecessary signal is canceled by inverting the polarity and adding.

(Embodiment) An embodiment of the present invention will be described with reference to a block diagram of a video floppy player shown in FIG.

1 is a video floppy disk, 2 is a magnetic head, 3 is a spindle motor, 4 is a magnetic head moving mechanism centered on a stepping motor, 5 is a spindle motor circuit consisting of a control circuit and a drive circuit, and 6 is controlled by a stepping motor circuit. It consists of a circuit and a drive circuit. 7 is a head amplifier that amplifies the signal reproduced by the magnetic head. 8 is a bypass filter, 9 is a low-pass filter, IO is a luminance signal FM demodulation circuit, 11 is a chrominance signal FM demodulation circuit, 12 is a luminance signal reproduction processing section, 13 is a chrominance signal reproduction processing section, 14 is a video output terminal, 15 is a delay circuit, 16 is an unnecessary signal removal circuit, 17 is a system control section, and 18 is an operation section. The delay circuit 15 can be composed of a passive delay line composed of a coil and a capacitor, a semiconductor CCD delay line, or the like. FIG. 2 shows an embodiment using a semiconductor CCD delay line. 21 is a signal input terminal, 22 is a signal output terminal, 2
3 is a semiconductor CCD delay line, and 24 is a low-pass filter that removes the clock component of the CCD delay line output. 25 is a clock generation circuit. If the number of stages of the CCD delay line is N and the time of one clock cycle is p, then the delay time T is T=N
It is Xp. 26 is a clock control input terminal, and the oscillation frequency of the clock, that is, the time of one cycle can be changed depending on the state of this terminal. FIG. 3 shows an unnecessary signal removal circuit. 31 is an input terminal for a delayed signal, 32 is an input terminal for a signal passed through the low-pass filter 9, 33 is an inversion circuit, 34 is an amplitude adjustment circuit, 35 is an addition circuit, and 36 is an output terminal.

The signal reproduced from the video floppy disk 1 by the magnetic head 2 is an FM signal as explained in the conventional example, but for the sake of simplicity, a pulse signal will be used in the explanation with reference to FIG.

(A) is a pulse signal recorded on a video floppy disk, (B) is a signal that has been reproduced by adding an unnecessary signal due to a pseudo gap and has passed through the head amplifier 7 and the low-pass filter 9. (C) is a signal that has been processed by a delay circuit for a time T The signal (d) is the inverted and amplitude-adjusted signal of (c), and is adjusted to an amount that cancels the unnecessary signal of (b). (
The sum of (a) and (d) is (e), and unnecessary signals due to pseudo gaps are removed.

In the case of a video floppy disk, the relative speed between the head and the disk changes depending on the track position, so the delay time is varied depending on the track position. Therefore, as shown in Figure 2, C
The clock of the CD delay line is changed depending on the track information.

(Effects of the Invention) According to the present invention, unnecessary signals generated by pseudo gaps can be removed and color reversal can be prevented, which has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of a video floppy player according to the present invention, and FIG. 2 is a diagram showing an embodiment of a delay circuit.
FIG. 3 is a diagram showing an embodiment of an unnecessary signal removal circuit, FIG. 4 is a diagram explaining unnecessary signal removal using a pseudo gap, FIG. 5 is a circuit diagram of a conventional example in a video floppy player, and FIG.
The figure shows the video floppy disk recording frequency allocation, FIG. 7 shows the head gap surface, and FIG. 8 shows the generation of unnecessary signals due to pseudo gaps. DESCRIPTION OF SYMBOLS 1... Video floppy disk, 2... Magnetic head, 3... Spindle motor, 4... Magnetic head movement mechanism (stepping motor), 5... Spindle motor circuit, 6... Stepping motor circuit, 7
...Head amplifier, 8..Bypass filter, 9.
-Low pass filter, 10... FM demodulation circuit for luminance signal, 11... FM demodulation circuit for color signal, 12... Luminance signal reproduction processing section, 13... Color signal reproduction processing section, 1
4...Video output terminal, 15...Delay circuit, 16
...Unnecessary signal removal circuit, 17...System control section, 21...Signal input terminal, 22...Signal output terminal, 23...CCD delay line, 24...
low-pass filter, 25... clock generation circuit,
26...Clock control input terminal, 31°32...
Input terminal, 33... Inversion circuit, 34... Amplitude adjustment circuit, 35... Addition circuit, 36... Output terminal. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] (1) A magnetic head for reproducing signals recorded on a recording medium, a head amplifier circuit, a delay means for delaying the head amplifier circuit output signal, and a predetermined level of the delayed signal by the delay means from the head amplifier circuit output signal. What is claimed is: 1. A magnetic recording and reproducing apparatus comprising: an unnecessary signal removing means for removing an unnecessary signal by subtracting an unnecessary signal; an FM demodulating means for demodulating a signal passed through the unnecessary signal removing means; and a signal reproducing processing means. (2) Claim (1) characterized in that the signal input to the FM demodulation means is a color signal of a video floppy disk.
The magnetic recording/reproducing device described above. (3) The magnetic recording and reproducing apparatus according to claim (1), characterized in that the delay time of the delay means can be varied.