JPH0439752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a novel magnetic recording and reproducing method, in particular, a signal, such as a video signal, is FM modulated, magnetically recorded on concentric tracks of a magnetic recording medium, and the tracks are magnetically recorded. This relates to a magnetic recording and reproducing method that reproduces a recorded signal and demodulates the reproduced signal, and the frequency characteristics of the demodulated signal are different when magnetically recorded on the inner track and when magnetically recorded on the outer track. It is an object of the present invention to provide a new magnetic recording and reproducing method that prevents magnetic change.

BACKGROUND TECHNOLOGY AND PROBLEMS As a method of recording video, etc., a magnetic disk is installed in an electronic still camera, and one field or one frame of video signals is magnetically recorded on each concentric track of the magnetic disk. A method has been developed at the applicant company. The reproduction is performed by attaching the magnetic disk on which the video signal is magnetically recorded to a suitable reproducing device, processing the video signal, and drawing the video on the screen of the television receiver. Furthermore, video signals are recorded by a method of magnetically recording a signal obtained by FM modulating a carrier wave having a certain frequency using the video signal. Therefore, on the playback side, the playback signal is
Demodulation processing is performed using an FM demodulator.

By the way, in the method of magnetically recording on the concentric tracks of a magnetic disk, the relative speed of the recording head and the reproducing head with respect to the track changes between the inner track and the outer track, and the resolution of the reproduced image changes. There was a problem. This is because one still image always consists of one or two tracks, regardless of whether it is an inner track or an outer track.
It is designed to record magnetically on the book's track.
When magnetically recording a still image, the rotational speed (number of rotations) given to the magnetic disk is constant regardless of the track to be recorded. Therefore, the relative speed of the head to the track becomes lower the closer the track is to the inner circumference. If the synchronization speed of the heads with respect to the track differs, the relationship between the levels of the upper and lower sides of the carrier wave of the output of the head that reproduces the FM-modulated magnetic recording signal will differ, resulting in the frequency characteristics of the demodulated signal. changes. Specifically, the following phenomenon occurs. In other words, there is almost no drop in the level of the lower wave of the demodulated signal when recording on either the outer or inner track, but the carrier level does not decrease much when recorded on the outer track. On the other hand, when recording is performed on tracks on the inner circumferential side, the decrease is relatively large. Therefore, when recording on the inner track, a so-called overmodulation phenomenon occurs in which the frequency characteristics of the lower wave appear to be higher, resulting in poor image quality. In addition, the level of the upper wave drops relatively significantly no matter which track is magnetically recorded on, but the level decreases more when it is recorded on the inner track than when it is recorded on the outer track. It's also big. The frequency characteristics of such demodulated signals vary greatly depending on the track, which causes a large difference in resolution.

Purpose of the Invention Accordingly, the present invention provides a method for converting signals such as video signals into
When magnetic recording is performed on the inner track in a magnetic recording and reproducing method in which FM modulation is performed to magnetically record on concentric tracks of a magnetic recording medium, the signal magnetically recorded on the track is reproduced, and the reproduced signal is demodulated. The purpose of this is to prevent the frequency characteristics of the demodulated signal from changing between the case of magnetic recording on the outer track and the case of magnetic recording on the outer track.

Summary of the Invention The magnetic recording and reproducing method of the present invention achieves the above objects by FM modulating a signal, magnetically recording it on concentric tracks of a magnetic recording medium, reproducing the signal magnetically recorded on the track, and reproducing the signal. In a magnetic recording and reproducing method for demodulating a signal, a pilot signal having a constant frequency is intermittently superimposed on the signal before FM modulation, and a pilot signal of the reproduced signal after signal reproduction and demodulation is used. is synchronously detected to detect its output level, and the frequency characteristic of the reproduced signal path is changed according to the output level of the synchronous detection so that the frequency characteristic of the signal is constant regardless of the difference in tracks. It is something to do.

Embodiments The magnetic recording and reproducing method of the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

1 and 2 show the circuit configuration of an apparatus for carrying out the magnetic recording and reproducing method of the present invention.
The figure shows a recording device, and FIG. 2 shows a reproducing device.

First, the recording device will be explained. 1 is an amplifier that amplifies the video signal, and 2 is a mixer that superimposes the video signal output from the amplifier 1 and a pilot signal. This pilot signal is, for example, 3.58M
This is obtained by gating the output signal of the oscillator 3, which generates a signal with a frequency of Hz, by means of a gate circuit 4. The gate signal applied to the gate circuit 4 is generated using the horizontal synchronizing signal H.Sync of the video signal, and the pilot signal is superimposed on the back porch of the horizontal synchronizing signal H.Sync. The video signal in which the pilot signal is superimposed on the back porch of the horizontal synchronization signal H.Sync is input from the mixer 2 to the FM modulator 5, where it is FM modulated. The FM modulated video signal is amplified by a recording amplifier 6 and input to a recording head, where it is magnetically recorded on concentric tracks of a magnetic disk. Note that FM modulation with a low modulation degree is called angle modulation, and in this specification, FM modulation naturally includes angle modulation.

Next, the playback device will be explained. 7 is a preamplifier that amplifies the video signal from the playback head, and 8 is a preamplifier that amplifies the video signal from the playback head.
The COS equalizer consists of a variable gain amplifier 9, a delay circuit 10, and a subtracter 11. This equalizer 8 has a linear phase characteristic in which the amplitude changes without changing the phase characteristic. The variable gain amplifier 9 has a gain that changes depending on a DC gain control voltage, and amplifies the video signal output from the preamplifier 7. The delay circuit 10 delays the video signal output from the preamplifier 7, and a subtracter 11 subtracts the output signal of the delay circuit 10 and the output signal of the variable gain amplifier 9 from one of them. Then, the output signal of the subtracter 11 is COS
This becomes the output signal of the equalizer 8. The frequency characteristics of the COS equalizer 8 are as shown in FIG.
In other words, the gain control voltage is low and the variable gain amplifier 9
If the output signal is 0 and only the reproduced signal output from the preamplifier 7 is output from the COS equalizer 8 through the subtracter 11, its frequency characteristic will be the third
Although it is flat as shown by the solid line a in the figure, when the gain control voltage increases, the frequency characteristics change as shown by the broken line b, the dashed line c, and the dashed double dot line d. In addition, the frequency where the frequency characteristic seesaws, that is, the seesaw point
CP changes depending on the amount of signal delay by the delay circuit 10.

The output signal of the COS equalizer 8 is sent to the FM modulator 12
It is demodulated at The demodulated signal output from the FM modulator 12 is input to a muting circuit 13, where muting is performed to remove the pilot signal PS. The output signal of the muting circuit 13 is sent to a color encoder (not shown), where it is processed and used for image reproduction. A gate signal applied to a gate circuit 14, which will be described next, is applied to the muting circuit 13 as a signal specifying a muting period.

The output signal of the FM modulator 12 is also input to a gate circuit 14 for extracting a pilot signal PS.
The gate circuit 14 receives a horizontal synchronizing signal H.
In response to the gate signal formed based on H.Sync, the gate is opened during the arrival period of the pilot signal PS superimposed on the back porch of the horizontal synchronization signal H.Sync.

Pilot signal output from gate circuit 14
The peak value of the output level of the PS is detected by the peak detector 15 through synchronous detection. The peak detector 15 includes a sampling pulse generation circuit 16
and a sampling hold 17. The sampling pulse generation circuit 16 amplifies the pilot signal PS output from the gate circuit 14 and passes the amplified signal through a limiter circuit or the like to appropriately shape the waveform and obtain a sampling pulse. Pilot signal PS
and the resulting sampling pulse. The sampling hold circuit 15 has a circuit configuration as shown in FIG. 5, for example. This circuit receives a sampling pulse at its base and applies a pilot signal PS to a capacitor C through a transistor Tr which is switched by the sampling pulse, and the capacitor C holds the peak level of the pilot signal PS for one horizontal synchronization period. The terminal voltage of capacitor C is amplified via the source follower FET circuit.

Therefore, the output of the peak detector 15 becomes a direct current whose voltage changes depending on the peak level of the pilot signal PS. If the magnetically recorded track is on the outer track, the level of the pilot signal PS will be low as shown by the solid line in Figure 4, and the more the track is on the inner track, the lower the level of the pilot signal PS will be.
Since the level of PS becomes higher as shown by the two-dot chain line in FIG. 4, the output voltage of the peak detector 15 becomes higher as the recorded track is closer to the inner circumference.

The output voltage of the peak detector 15 is determined by the DC amplifier 18.
The voltage is amplified by and input to the variable gain amplifier 9 as a gain control voltage.

Next, a case where magnetic recording is performed using the recording device shown in FIG. 1 and reproduction is performed using the reproducing device shown in FIG. 2 will be described.

The more magnetic recording is performed on the inner track of the variable gain amplifier, the greater the level of the lower side wave of the demodulated signal relative to the level of the carrier wave becomes. The change in the frequency characteristic appears as a change in the level of the pilot signal PS, in which the level of the pilot signal PS becomes higher after demodulation when magnetically recorded on the inner track. Therefore, the level of the pilot signal PS of the demodulated signal becomes higher as the signal is recorded on the inner track, and the peak detector 1
7 also becomes high, the voltage applied from the DC amplifier 18 to the variable gain amplifier 9 of the COS equalizer 8 as a gain control voltage becomes high.
Then, the frequency characteristics of the COS equalizer 8 change as shown by a broken line b, a dashed dotted line c, and a dashed double dotted line d. In the case of a signal recorded on a track slightly closer to the inner circumference, it becomes as shown by the broken line b, and in the case of a signal recorded on a track even closer to the inner circumference, it becomes as shown in the broken line b. In the case of a signal recorded on a track further towards the inner circumference, the signal is shown as a one-dot chain line c, and in the case of a signal recorded on the innermost track, it is as shown on a two-dot chain line d. . Therefore, the COS equalizer 8 can correct the tendency that the ratio of the lower side wave level to the carrier wave level becomes larger and the upper side wave level becomes lower as the signal is recorded on the inner track.

In addition, since the present invention grasps the frequency characteristics of the demodulated signal by detecting the level of the demodulated signal of the pilot signal PS, the frequency of the pilot signal PS is based on the frequency characteristics of the inner track and the outer track. It is necessary to set the level of the pilot signal PS to a value that changes depending on the difference. Further, the equalizer 8 only needs to have a linear phase characteristic, and is not limited to a COS equalizer.

Furthermore, by adjusting the variable resistor VR to the magnitude of the gain control voltage of the DC amplifier 18 for the same level of the demodulated pilot signal PS, the degree to which the frequency characteristics change with respect to the change in the demodulation level of the same pilot signal PS can be controlled. Further, the see-saw point CP of the frequency characteristic can be adjusted as appropriate by adjusting the delay amount of the delay circuit 10.

Effects of the Invention As described above, the magnetic recording and reproducing method of the present invention includes FM modulating a signal, magnetically recording it on concentric tracks of a magnetic recording medium, reproducing the signal magnetically recorded on the track, In a magnetic recording and reproducing method for demodulating the reproduced signal, a pilot signal having a constant frequency is intermittently superimposed on the signal before FM modulation, and a pilot signal having a constant frequency is intermittently superimposed on the signal, and the reproduced signal is The pilot signal is synchronously detected to detect its output level, and the frequency characteristic of the reproduced signal path is changed according to the output level of the synchronous detection so that the frequency characteristic of the signal is constant regardless of the difference in tracks. This is a characteristic feature. Therefore, it is possible to prevent the frequency characteristics of the demodulated signal from changing between when magnetic recording is performed on the inner track and when magnetic recording is performed on the outer track.

[Brief explanation of drawings]

The drawings are for explaining an example of implementation of the magnetic recording and reproducing method of the present invention, and FIG. 1 is a circuit block diagram showing the configuration of a recording device, FIG. 2 is a circuit block diagram showing the configuration of a reproducing device, and FIG. Figure 3 is a diagram showing the frequency characteristics of the equalizer, Figure 4 is a time chart showing the pilot signal and sampling pulse,
FIG. 5 is a circuit diagram showing the main parts of the sampling and holding circuit. Explanation of symbols 2...mixer, 3...oscillator,
4...Gate circuit, 5...FM modulator, 8...Equalizer, 12...FM demodulator, 14...Gate circuit, 15...Peak detector.

Claims (1)

[Claims] 1. In a magnetic recording and reproducing method in which a signal is FM modulated and magnetically recorded on concentric tracks of a magnetic recording medium, the signal magnetically recorded on the track is reproduced, and the reproduced signal is demodulated,
Before FM modulation, a pilot signal with a constant frequency is intermittently superimposed, and after signal reproduction and demodulation, the pilot signal of the reproduced signal is synchronously detected to detect its output level, and the frequency characteristics of the signal are determined. 1. A magnetic recording and reproducing method, characterized in that the frequency characteristics of the reproduced signal path are changed in accordance with the output level of the synchronous detection so that the frequency is constant regardless of the difference in tracks.