JPS5819193B2 - Rotating magnetic disk imaging recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention records video output signals of a color camera that outputs a plurality of multiplexed color signals on a rotating magnetic sheet, and reproduces this to produce a general color television signal such as an NTSC signal. The present invention relates to a rotating magnetic disk imaging recording/reproducing device to be assembled.

In conventional magnetic recording and reproducing devices, magnetic tape was mainly used as the recording medium, but in recent years, video signals have been magnetically recorded and reproduced not only on tape but also on magnetic sheets, which are rotating magnetic disks. It's starting to look like this.

However, recording and reproducing using such a rotating magnetic sheet has the following problems.

In other words, in magnetic recording and reproducing methods using tape, the relative speed between the tape and the magnetic head was always constant according to the designed value, but in magnetic recording and reproducing using rotating magnetic sheets,
The relative speed between the recording medium and the magnetic head changes depending on the recording tracks on the inner and outer peripheries.

Therefore, even if the recording signals have the same frequency, the recording wavelengths will be different.

As a result, as shown in FIG. 1, the frequency characteristics, especially in the high range, of recorded and reproduced video signals change as shown in 11.12 between tracks on the inner circumference and tracks on the outer circumference of the magnetic sheet.

Therefore, if a broadband video signal is directly recorded and reproduced using this recording/reproducing characteristic, frequency correction becomes extremely difficult because the frequency ratio between low frequency and high frequency is large.

Generally, this problem is solved by using frequency modulation, but even in this case, the frequency characteristics of recording and reproduction must be flat within the frequency band used, and therefore frequency correction is necessary.

As mentioned above, since the relative speed is constant in conventional tape recording and reproduction, correction can be easily performed.

However, when the recording medium changes from a tape to a rotating magnetic sheet, the frequency characteristics differ between the inner and outer circumferences of the disk and the frequency characteristics of recorded and reproduced video signals change with the conventional constant correction.

In this case, if the signal to be recorded and reproduced is a system that has color information in the high frequency region of the video signal, such as an NTSC signal, the color density will change, but this is generally caused by the color burst signal of the NTSC signal. It can be corrected using , so it does not pose much of a problem.

However, when a video output signal from a preamplifier of a frequency-separated single-tube color camera having a spectrum as shown in FIG. 2 is used as a recording/reproduction signal, a very serious problem arises.

That is, as described above (because the frequency characteristics of the outer tracks are longer than those of the inner tracks), if the frequency correction is set to the maximum on the inner tracks, over-correction will occur on the outer tracks, and the high frequency portion of the video signal will deteriorate.

This is because the sidebands of the frequency modulated wave become relatively small within the transmission band, and as a result, the R (red) and B (blue) color signals become smaller, and the hue changes toward green.The opposite is true. The color will change towards magenta.

Therefore, when recording and reproducing video signals from a frequency-separated single-tube color camera, the difference in frequency amplitude characteristics between the inner and outer peripheries of the magnetic sheet as described above is not just a change in color density; This results in a change in hue, which can be an extremely serious problem.

The present invention has been made in view of the above-mentioned problems.The present invention corrects changes in the frequency amplitude characteristics of magnetic recording and reproduction due to differences in recording track radius in accordance with the movement of the magnetic head. It is an object of the present invention to provide a rotating magnetic disk imaging, recording and reproducing device in which changes in color density and hue of an image are compensated for.

The present invention will be explained in detail below with reference to the drawings.

FIG. 3 is a block diagram showing the configuration of a rotating magnetic disk imaging recording and reproducing apparatus according to an embodiment of the present invention.

In the figure, reference numeral 31 denotes a color camera that outputs a plurality of multiplexed color signals, for example a frequency-separated single-tube color camera, and this output signal has the frequency spectrum shown in FIG. 2 above.

This output signal is frequency modulated by a frequency modulator 32 and guided to a recording amplifier 34 through a gain control circuit 33.

After being amplified by the amplifier 34, the switch 35
The signal is supplied to a magnetic head 36 for magnetic recording and reproducing through the magnetic head 36 for magnetic recording and reproduction.

37 is a rotating magnetic sheet, and signals are recorded on tracks 37a, 37b, etc. by the magnetic head 35 as shown in FIG.

Reference numeral 38 in Fig. 3 is a head moving mechanism, which allows the head base 38-1 mounted on the guide rail to be moved in the radial direction of the magnetic sheet by rotating a feeding screw. As the head base 38-1 moves, the magnetic head 36 moves.

Further, a slider of an edge cal potentiometer type resistor 39 is connected to the head base 38-1, and this slider is moved by the movement of the head base, that is, the magnetic head 36. ing.

A DC voltage 40 is applied to both ends of the variable resistor 39, and a DC voltage corresponding to the amount of movement of the slider, that is, the amount of movement of the magnetic head 36, is taken out from the terminals of the slider.

This DC voltage is supplied to the gain control circuit 33 as a gain control signal.

The gain control circuit 33 controls the magnetic sheet 3 based on this control signal.
Recording currents of different magnitudes are applied to the magnetic head 36 corresponding to the tracks on the magnetic head 7.

Specifically, the current is controlled so that more current flows in the outer circumference than in the inner circumference.

The gain control circuit 33 may be any amplifier whose gain changes depending on the DC voltage as described above. For example, the gain control circuit 33 changes the gain by controlling the constant current source 502 of the differential amplifier 501 with the DC voltage as shown in FIG. Well-known circuits can be used.

1. The rotation phase of the rotating magnetic sheet 37 is determined by providing a slit on the sheet 37 through which light passes, and detecting the light from the light source 41 with the light receiver 42, sending it to the terminal 44a' of the control circuit 44 of the motor 43, and transmitting it from the camera 31. The rotation and phase shift of the motor 43 are controlled by comparing with the sent standard pulse 44b.

During reproduction, the switch 35 is connected to the reproduction side 35b, and the output from the magnetic head 36 is guided to the amplifier 45.

The output signal amplified by this amplifier 45 is sent to a frequency correction circuit 46 where frequency correction is performed.

This correction is performed using a DC voltage obtained by the movement of the magnetic head 36, and the configuration of this frequency correction circuit 46 is shown in FIG.

This correction circuit 46 is similar to the aperture correction used in television cameras and the like, and increases the amplitude component of high frequencies compared to low frequencies.

That is, the reproduced frequency modulated wave, which is the output obtained from the magnetic head, enters an input terminal 601 in FIG. 6, is divided into two parts, and is sent to a variable delay circuit 602 and a variable amplifier 603, respectively.

The variable delay circuit 602 and the variable amplifier 603 are supplied with DC voltages obtained in response to the movement of the magnetic head 35 at terminals 604 and 605, respectively, and the variable delay circuit 602 is controlled depending on the magnitude of the DC voltage. The delay time and the amplification degree of variable amplifier 603 are determined.

The outputs of variable delay circuit 602 and variable amplifier 603 are sent to differential amplifier 606, and a frequency-corrected reproduced frequency modulated wave is obtained from its output terminal 607.

The correction book and correction frequency in this frequency correction circuit 46 are transmitted to the variable delay time amplifier 603 of the variable delay circuit 602 described above.
and the differential amplification ratio of the differential amplifier 606.

FIG. 7 701 shows an example of the frequency characteristics of the output of this frequency correction circuit 46.

702 in the figure is the frequency characteristic before correction.

Note that the above correction does not necessarily require controlling both the delay circuit 602 and the variable amplifier 603, and only one of them may be controlled using the DC voltage.

Also, to change the delay time depending on the DC voltage, for example,
There is a method in which a voltage variable capacitance diode is used as a capacitor in the delay circuit shown in the figure, which consists of an inductance L and a capacitor C, and this is controlled by a DC voltage.

In this case, the reproduced frequency modulated wave enters from the input terminal 801 and is taken out from the output terminal 803, and the time during which it passes is determined by L of the inductances 804a to 804c and C of the voltage variable capacitance diodes 805a to 805d.

A positive DC voltage is applied to the terminal 806 in advance, and by adding the DC voltage obtained by the head moving mechanism to this, C is obtained.
The capacity changes and eventually the delay time.

will change.

The inductance 807 only needs to have a large impedance to the frequency modulated wave and a small impedance to the control signal. Because it is low and dark, separation is possible.

Further, as the variable amplifier 603, a differential amplifier as shown in FIG. 5 can be used.

In this way, the frequency characteristics caused by changes in the relative velocity between the magnetic head and the magnetic sheet at the inner and outer peripheries of the magnetic sheet 37 are corrected.

This corrected reproduction frequency modulation wave is transmitted to the demodulator 47 in FIG.
is guided and demodulated to extract the video signal.

This video signal is passed through a low-pass F wave filter 48 and a bandpass filter 49.
50.

As a result, a luminance signal Y is obtained from the low-pass p-wave filter 48, and necessary color signals are taken out from the bandpass filters 49 and 50, respectively.

The outputs of these bandpass filters 49 and 50 are respectively □detector 5
1.52 and color signals R (red) and B (
blue) is obtained.

And the above Y. The three R and B signals are supplied to a color coder 53, assembled into a standard color television signal such as an NTSC signal, and taken out from an output terminal 54.
Displayed by a television receiver.

At this time, a stable reproduced image with no change in color density or hue between the inner and outer circumferences of the magnetic sheet is obtained due to the frequency correction described above.

□Furthermore, FIG. 3 55 is a circuit that separates and shapes synchronization-related signals, and supplies necessary pulse signals to the color coder 53.

As explained above, the present invention provides an imaging recording and reproducing apparatus that frequency-modulates the video output of a preamplifier of a frequency-separated single-tube color camera, records it on a rotating magnetic sheet, and assembles it into a standard color television signal during reproduction. The recording track exhibits different frequency characteristics depending on the radius of the magnetic sheet, and this frequency characteristic is corrected by a control signal corresponding to the movement of the head moving mechanism during recording or reproduction.

Therefore, according to the present invention, the video output of a color camera with a unique frequency spectrum is recorded and reproduced on a rotating magnetic sheet, and the problem of poor reproduced image quality, especially when it comes to color, has been solved when it is assembled into a standard color television signal. Changes in density and hue are compensated for, and it is possible to obtain a reproduced image that is faithful to one primary color.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways.

For example, the difference in frequency characteristics during reproduction can be corrected by changing the resonant frequency of the magnetic head in accordance with the amount of movement of the magnetic head.

Specifically, it is possible to add a voltage variable capacitance diode to the magnetic head to change and correct the resonant frequency, or to control the Q of the magnetic head to correct the frequency characteristics of the transmission band.

For this purpose, a voltage variable resistor such as a resistor between the drain and source of an FET can also be used.

When using an FET, a control DC voltage may be applied to the gate of the FET.

Further, although the frequency modulated wave is corrected in the above embodiment, the correction may be performed after demodulating the frequency modulated wave.

For example, in FIG. 3, the color encoder 53 has Y, R,
The voltage gain of B may be controlled by a control voltage obtained by moving the head.

For this, there is a method of fixing Y and controlling R and B, and a method of controlling R,
There is a method of fixing B and controlling Y.

In the latter case, the disadvantage is that the saturation changes, but the hue does not change, and the problem is more noticeable because the hue is more noticeable, so this method is also effective.

Furthermore, the present invention can be applied not only to frequency-separated color cameras but also to color cameras that output a plurality of multiplexed color signals, such as interleaved or phase-separated color cameras, to obtain similar effects. .

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the difference in frequency characteristics of magnetic recording and reproduction due to the difference in the tracks of a conventional rotating magnetic disk.
The figure is a frequency spectrum diagram of a video output signal of a general frequency-separated single-tube color camera, FIG. 3 is a block diagram showing the configuration of a rotating magnetic disk imaging recording and reproducing apparatus according to an embodiment of the present invention, and FIG. A diagram showing the trunk on the rotating magnetic disk, FIG. 5 is a diagram showing the specific configuration of the gain control circuit in the above embodiment, and FIG. 6 is an example of the specific configuration of the frequency correction circuit in the same embodiment. 7 is a frequency characteristic diagram of the output of this frequency correction circuit, and FIG. 8 is a diagram showing an example of the configuration of the variable delay circuit in the frequency correction circuit. 31... Frequency separation type single tube color camera, 32
...Frequency modulator, 33...Gain control circuit, 36...Magnetic head, 37...
Magnetic sheet, 38...Head moving mechanism, 39.
... Variable resistor, 46 ... Frequency correction circuit, 47 ... Demodulator, 48 ... Low frequency P
Wave filter, 49, 50...Band filter, 51, 52
......Detector, 53...Color camera.

Claims (1)

[Claims] 1. A color camera that outputs a plurality of multiplexed color signals, a frequency modulator that frequency modulates the output of this color camera, and a gain control circuit that performs gain control on the output of this modulator.
The recording current output from this control circuit is supplied to a magnetic head that performs magnetic recording on a rotating magnetic disk, and corrects changes in the frequency characteristics of signals recorded on the rotating magnetic disk that are reproduced by this magnetic head. A frequency correction circuit, a signal processing circuit that processes the output of this correction circuit and assembles it into a standard color television signal, and connects the magnetic head to the gain control circuit and the frequency correction circuit depending on recording and reproduction. A rotating magnetic disk imaging device comprising: a switching switch; and means for controlling the gain of the gain control circuit and the correction amount of the frequency correction circuit according to the position of the magnetic head on the rotating magnetic disk. Recording and playback device.