JPH04150290A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the recording in which a high picture quality reproduced picture is obtained from all magnetic tapes by setting optimizingly a recording current, a frequency characteristic and a Y/C mixing ratio at all times. CONSTITUTION:A test circuit 40 is activated prior to recording, resulting in operating a control circuit 21 in order and when a gain of a voltage controlled amplifier 8 is decided, a characteristic curve of a recording equalizer 7 is decided and then the gain of a voltage controlled amplifier 29 is decided. Then the prescribed characteristic curve is set and the frequency characteristic is adjusted and an FM luminance signal YFM outputted from the recording equalizer 7 is amplified by the voltage controlled amplifier 8, and on the other hand, a low frequency conversion chroma signal CL is amplified by the voltage controlled amplifier 29 and fed to an adder 9, and added to the FM luminance signal YFM from the voltage controlled amplifier 8, the result is amplified by a recording amplifier 10 and fed to a recording head 11 and then recorded. Thus, a high picture quality reproduced picture is always obtained regardless of the performance of the magnetic tape in use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a method for converting a color video signal into a frequency-modulated luminance signal (hereinafter referred to as an FM luminance signal) and a low-frequency converted chroma signal (hereinafter referred to as a low-frequency converted chroma signal). The present invention relates to a magnetic recording and reproducing apparatus that records and reproduces information on a magnetic tape as an added signal with a chroma signal.

[Prior Art] Currently, home VTRs and some professional VTRs employ a method of converting a color video signal into a sum signal of an FM luminance signal and a low frequency converted chroma signal for recording and playback. There is.

In this type of VTR, in order to obtain high-quality playback images, the FM luminance signal is recorded at the optimum recording current that provides the maximum level during playback. A recording equalizer is provided so that the data can be reproduced with suitable frequency characteristics. Furthermore, crosstalk interference due to cross-modulation between the FM luminance signal and the low-frequency converted chroma signal that occurs during playback is made less noticeable.

The mixing ratio of these FM luminance signals and low-frequency converted chroma signals (
Hereinafter, the Y/C mixing ratio) is determined. Among the components produced by this cross-modulation (cross-modulation components), the one that stands out as cross-beat interference is where fY is the carrier frequency of the FM luminance signal, and fc is the chrominance subcarrier frequency of the low-frequency converted chroma signal.

This is a cross-modulation component (hereinafter referred to as cross-modulation component (Y-2G)) with a frequency of (fY-2fc). If the Y/C mixing ratio is too large, the cross-modulation component (Y-2C) will increase and cross-beat interference will become noticeable. Conversely, if the Y/C mixing ratio is too small, the amplitude of the low-frequency converted chroma signal will become small. S/N deteriorates. Therefore, the optimum Y/C mixing ratio is set by taking these balances into account.

By the way, there are grades of commercially available magnetic tapes.
The performance of magnetic tape varies depending on the grade. Furthermore, even if a magnetic tape is of a high grade, its performance deteriorates when it is used repeatedly. If a magnetic tape with such low performance is used, even if the recording current and frequency characteristics of the FM luminance signal are set to be optimal as described above, and the Y/C mixing ratio is set to be optimal. However, if the performance of the magnetic tape differs, it will not be optimal, and it will not be possible to obtain reproduced images of the best quality.

This is of course a problem for home VTRs as well, but it is especially a big problem when producing soft tapes for commercial use, as high grade unused magnetic tapes must be used.

On the other hand, r Audio V 1deo J Dempa Shimbun Publishing, January 1990 Issue 2.85 states that the FM installed in the VTR's playback system according to the condition of the magnetic tape.
A technique is disclosed in which the characteristic curve of an equalizer is automatically controlled.

[Problems to be Solved by the Invention] The above-mentioned conventional techniques are effective in improving the image quality of luminance signals to some extent.

However, VTRs that do not have such an FM equalizer
No consideration has been given to

Furthermore, in the above-mentioned conventional technology, if the performance of the magnetic tape is low, the FM luminance signal will not be recorded with the optimum recording current and frequency characteristics, and the Y/C mixing ratio will not be optimum. Therefore, even if the characteristic curve of the FM equalizer is controlled, if a magnetic tape with low performance is used, image quality deterioration cannot be avoided.

The purpose of the present invention is to solve this problem by providing a magnetic tape that can always provide high-quality reproduced images regardless of the performance of the magnetic tape used or even when reproduced by other magnetic recording and reproducing devices. The purpose of the present invention is to provide a recording/playback device.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a recording equalizer for setting a frequency characteristic of an FM luminance signal, and a first equalizer for setting a recording current of the FM luminance signal. A second voltage controlled amplifier for amplifying the low frequency converted chroma signal and setting the Y/C mixing ratio, and a test circuit are provided. The test circuit changes the gain of the first voltage-controlled amplifier with respect to the tape used, and applies a first test signal having a frequency equal to the center frequency of the carrier wave of the frequency-modulated luminance signal for each change. a first control means for recording and reproducing via a first voltage-controlled amplifier and detecting the gain at which the reproduction level of the first test signal is maximum; and changing the characteristic curve of the recording equalizer to change the gain. every second . of a different frequency within the frequency band of the frequency modulated luminance signal. a second control means for recording and reproducing a third test signal via the recording equalizer and detecting a characteristic curve in which a difference in reproduction level between the second and third test signals is constant; By varying the gain of the voltage controlled amplifier, the first test signal is routed through the first voltage controlled amplifier and at a frequency equal to the chrominance subcarrier of the down-converted chroma signal. The fourth test signal is recorded and reproduced through the second voltage controlled amplifier, and the reproduced first . and third control means for detecting the gain at which the difference between the level of a specific cross-modulation component of the fourth test signal and the reproduction level of the first test signal is constant.

[Operation] A test circuit is operated before recording a color video signal. First in the test circuit. The second and third control circuits operate in sequence. For example, when the first control means operates to determine the gain of the first voltage controlled amplifier, then the second control means operates to determine the gain of the first voltage controlled amplifier.
control means are operated. Once the characteristic curve of the recording equalizer is determined by this, the third control means operates to determine the gain of the second voltage controlled amplifier.

The gain of the first voltage controlled amplifier determined by the first control means is F for the magnetic tape used at this time.
This is the gain at which the M luminance signal is recorded at the optimum recording current. The characteristic curve of the recording equalizer determined by the second control means is a characteristic curve that optimizes the frequency characteristics of the reproduced FM luminance signal when the FM luminance signal is recorded and reproduced on the same magnetic tape. Further, the gain of the second voltage-controlled amplifier determined by the third control means is such that when the FM luminance signal and the low-frequency conversion chroma signal are added and recorded and reproduced on the same magnetic tape, the gain of the second voltage-controlled amplifier is determined to be the optimum Y. /C mixing ratio is the gain.

After the test circuit operates as described above, when a color video signal is recorded on the same magnetic tape, the first
．． Gains determined by the first and third control means are set in the second voltage controlled amplifier, respectively, and a characteristic curve determined by the second control means is set in the recording equalizer. As a result, the FM luminance signal is recorded on this magnetic tape with the optimum recording current and optimum frequency characteristics, and the low-frequency converted chroma signal is recorded with the optimum Y/C mixing ratio.

Therefore, regardless of the performance of the magnetic tape, the color video signal can be recorded in the best condition, and high-quality reproduced images can be obtained even when reproduced by other magnetic recording and reproducing devices.

[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 apparatus according to the present invention, in which 1 is an input terminal, 2 is an AGC (automatic gain control) circuit, 3 is a Y/C separation circuit, and 4 is a pre-emphasis system. circuit, 5 is an FMi adjustment circuit, 6 is a switch, 7 is a recording equalizer, 8 is a voltage control amplifier, 9 is an adder, 1
0 is a recording amplifier, 11 is a recording head, 12 is a playback head, 13 is a preamplifier, 14 is a switch, 15 to 18 are B
PF (band pass filter), 19.20 is a switch,
21 is a control circuit, 22, 23 is a reference value generation circuit, 24 is a reference signal generation source, 25 is an ACC (automatic chroma control) circuit, and 26 is a frequency converter.

27 is an LPF (low pass filter), 28 is a switch, 29 is a voltage control amplifier, 30 is an FM equalizer, 31
is a limiter circuit, 32 is an FM demodulation circuit, 33 is a de-emphasis circuit, 34 is an LPF, 35 is an ACC circuit, 36
is a frequency converter, 37 is a BPF, 38 is an adder, 3
9 is an output terminal, and 40 is a test circuit.

In FIG. 1, the recording/reproducing mode and the recording test mode can be selected by switching switches 6.14.28. The recording test mode is a recording system adjustment mode for ensuring that the same good recording and reproducing characteristics are obtained regardless of the type of magnetic tape used, and is performed on the tape being used.

For recording test mode, switch 6.14.28 to rTEs
Set by closing to TJ side, test circuit 40
By operating, the characteristics of the recording equalizer 7 and the gains of the voltage control amplifiers 8 and 29 are appropriately set. After that, when the switch 6.28 is switched to the rRECJ side and a color video signal is input from the input terminal 1, the characteristics of the recording equalizer 7 and the voltage control amplifier 8 set as described above are changed.
With a gain of .29, the color video signal is recorded at a recording voltage and recording current that maximize the reproduction output level.

The operation of this embodiment will be explained below, but first, the recording/reproducing mode will be briefly explained.

During recording, the switch 6.28 is closed to the rRECJ side. The video signal input from input terminal 1 is
After the amplitude is made constant in the circuit 2, the Y/C separation circuit 3 separates the signal into a luminance signal Y and a chroma signal C.

The brightness signal Y is pre-emphasized by a pre-emphasis circuit 4 and then modulated by an FM modulation circuit 5 to become an FM brightness signal YFM, which is then sent to a recording equalizer 7 via a switch 6.
is supplied to In the recording equalizer 7, a predetermined characteristic curve as will be described later is set by the control circuit 21 of the test circuit 40, and the frequency characteristics of the FM luminance signal YFM are thereby adjusted. The FM luminance signal YFM output from the recording equalizer 7 is amplified by the voltage control amplifier 8 whose gain is set by the control circuit 21 as described later, and then supplied to the adder 9.

Furthermore, the chroma signal C(N
In the case of TSC method, the color subcarrier frequency is 3.58MHz)
is set to a constant amplitude by the ACC circuit 25, then frequency-converted to a low frequency by the frequency converter 26, and unnecessary components are removed by the LPF 27 to become the low-frequency converted chroma signal OL (VH
In the 3 standards, the subcarrier frequency for one color is 629kHz). This low frequency converted chroma signal CL passes through a switch 28, is amplified by a voltage control amplifier 29 whose gain is set by the control circuit 21, is supplied to an adder 9, and is added to the FM luminance signal YF from the voltage control amplifier 8. be done. The addition signal output from the adder 9 is amplified by a recording amplifier 10, supplied to a recording pad 11, and recorded on a magnetic tape (not shown).

During playback, the switch 14 is closed to the rPBJ side.

The sum signal of the FM luminance signal and the low-frequency converted chroma signal reproduced from a magnetic tape (not shown) by the reproduction head 12 is amplified by the preamplifier 13 and sent to the FM via the switch 14.
The signal is supplied to the equalizer 30 and the LPF 34.

In the FM equalizer 30, the FM luminance signal is separated from the added signal, and the amplitude is made constant. This FM brightness signal YF
The upper and lower sidebands of M are balanced by a limiter circuit 31, and the baseband luminance signal Y is converted by an FM demodulator circuit 32.
is demodulated. This luminance signal Y is subjected to de-emphasis processing in a de-emphasis circuit 33 to improve the S/N, and is supplied to an adder 38.

The LPF 34 separates the low frequency converted chroma signal CL from the reproduced addition signal. This low frequency converted chroma signal CL
After the amplitude becomes constant in the ACC circuit 35, the frequency is converted to a high frequency band in the 1-frequency converter 36, unnecessary components are removed in the BPF 37, and the original high color subcarrier frequency (3.58 MHz in the case of the NTSC system) is obtained. becomes the chroma signal C. This chroma signal C is added to the luminance signal Y from the de-emphasis circuit 33 by an adder 38 to form a color video signal, which is output from an output terminal 39.

The above is the recording/reproducing operation in this embodiment, and the control circuit 2
The level of the recording current of the recording head 11 is set by the recording equalizer 7 and the voltage control amplifiers 8 and 29 controlled by the recording head 1 so that the reproduction output level from the reproduction head 12 is maximized.

Next, a recording test mode for setting the characteristic curve of the recording equalizer 7 and the gains of the voltage control amplifiers 8 and 29 in this way will be explained. However, in this mode, the switch 6.14.28 is closed to the rTESTJ side.

Recording test mode is available regardless of the type of tape used.
A recording voltage test mode for determining the optimum recording current that maximizes the reproduction level of the FM luminance signal, a frequency characteristic adjustment mode for making the frequency characteristics of the FM luminance signal good and equal, and a luminance signal and low frequency conversion chroma signal. There is also a color test mode to prevent the effects of cross-modulation. In the recording voltage test mode, the gain of the voltage control amplifier 8 is set, and in the frequency characteristic adjustment mode, the characteristic curve of the recording equalizer 7 is set. Further, in the color test mode, the gain of the voltage control amplifier 29 is set.

First, the recording voltage test mode will be explained.

In this mode, under the control of the control circuit 21, the reference signal generation source 24 operates at the center frequency (V
A signal with a frequency f1 (hereinafter referred to as f11) equal to approximately 4 MHz according to the H8 standard is generated. This f11
The signal passes through a switch 6, is processed by a recording equalizer 7, a voltage control amplifier 8, an adder 9, and a recording amplifier 10, is supplied to a recording head 11, and is recorded on a magnetic tape. At this time, a certain gain is set in the voltage controlled amplifier 8 by the control circuit 21 of the test circuit 40.

When recording for a predetermined period of time is completed, the magnetic tape is rewound and the reproducing head 12 reproduces No. f11.

After this reproduction f, double signal, and amplification by the preamplifier 13,
The signal is supplied to the test circuit 40 via the switch 14. In the test circuit 40, this f-force signal is extracted to the BPF 17 and supplied to the control circuit 21 via the switch 20 closed to the A side. In the control circuit 21, the level of the supplied signal f11 is detected and held.

The above is the first recording and reproduction of the f-signal.

Next, the control circuit 21 changes the gain of the voltage control amplifier 8 by a predetermined amount, and the reference signal generation source 24 generates the f signal again to perform the second recording and reproduction of the f□ signal similar to the above. . Then, the control circuit 21 controls the regenerated f
In addition to detecting and holding the level of the power signal, this level is compared with the level held by f11 from the first recording and reproduction, and if the level of the second f power signal is high, voltage control is performed. The gain of the amplifier $8 is changed by a predetermined amount in the same direction as above, and when the second f11 level is small, the gain of the voltage control amplifier 8 is changed by a predetermined amount in the opposite direction to the above. Then, the reference signal generation source 24 generates the f signal again to perform the third recording and reproduction of f and ff1.

In this way, by repeating the recording and reproducing of the f□-fold signal and changing the gain of the voltage-controlled amplifier 8, the gain of the voltage-controlled amplifier 8 that maximizes the level of the reproduced signal f11 is found. And when the level of reproduction f11 reaches its maximum,
The control circuit 21 fixes the gain of the voltage control amplifier 8 to the gain at this time.

As a result, the FM luminance signal YFM from the FM modulator 5 is recorded on the tested magnetic tape at the optimum recording current that maximizes the reproduction level. Even if the properties of the magnetic tape used differ, the gain set in the voltage control amplifier 8 varies accordingly, making it possible to always perform recording with the optimum recording current.

Next, the 1-frequency characteristic adjustment mode will be explained.

In this mode, the reference signal generation source 24 generates two signals (hereinafter referred to as f2.f signals, respectively) with different frequencies, fitf, within the frequency band of the FM luminance signal. These f2. The f signal is recorded and reproduced in the same manner as the f signal described above, and is sent from the preamplifier 13 to the switch 14.
The signal is supplied to the test circuit 40 via.

FIG. 2 shows in detail the operation of the test circuit 40 in the frequency characteristic adjustment mode. In the figure, the f2 signal among the reproduced f1, f, and signals is extracted by the BPF 15, and the f3 signal is Extracted with BPF16. The extracted f1 and f□ signals are alternately selected by the switch 19 and supplied to the control circuit 21.

In the control circuit 21, the arithmetic unit 41 calculates the difference Xy between the amplitude values of f1, f, and the signal, that is, Xy''lfz fi, and then the comparator 42 calculates the difference The control section 43 controls the recording equalizer 7 in accordance with the difference between the two.

Even in this frequency characteristic adjustment mode, f2. Recording and reproduction of the f3 signal is repeated, and if there is a difference between the difference XY and the reference value X1 for each recording and reproduction, the characteristic curve of the recording equalizer 7 is changed in the direction in which this difference becomes zero. When this difference becomes zero, the characteristic curve of the recording equalizer 7 is fixed to the characteristic curve at this time.

In this way, regardless of the nature of the magnetic tape used, F
The characteristic curve of the recording equalizer 7 is set so that the reproduction frequency characteristic of the M luminance signal is constant.

According to the inventors' research, it has been found that commercially available oxide tapes have different frequency characteristics depending on the grade, and higher grade tapes have better frequency characteristics, as shown in Figure 3. .

In FIG. 3, tape A is a high grade tape and tape D is a normal grade tape.

If recording and reproduction are performed while the frequency characteristics are different in this way, a difference in frequency characteristics will occur in the reproduced FM luminance signal. Fourth
The figure shows playback FM for tapes with different grades of A-D.
It shows the difference in frequency characteristics of the luminance signal, tape A is the highest grade tape, tape B and C
, D are assumed to have lower grades. In addition, the frequency characteristics on the vertical axis are responses at 2 and 5 MHz based on the responses at 0 and 5 MHz, and tape A
It shows the relative level when the response of is taken as the reference (OdB).

Next, the color test mode will be explained.

In FIG. 1, in this mode, the reference signal source 24
is the color subcarrier frequency (VH
8 standard, the signal with frequency f4 equal to 629kHz) (
(hereinafter referred to as f4 signal). The f-power signal passes through a switch 6, a recording equalizer 7, a voltage control amplifier 8,
The f4 signal is sent to switch 28. The signals are added by the adder 9 through the voltage control amplifier 29, recorded and reproduced on a magnetic tape, and supplied to the test circuit 4o via the preamplifier 13 and switch 14, as in the recording voltage test mode.

In the test circuit 4o, as shown in detail in FIG. 5, the f1 signal is extracted from the reproduced signal from the switch 14 by the BPF 17.

By the way, when the FM luminance signal and the low frequency converted chroma signal are mixed and recorded and reproduced, as shown in FIG. If the color subcarrier of f4 is C, then
Cross-modulation components such as a cross-modulation component (Y-2C) with a frequency of (f1-2f,) and a cross-modulation component (y-c) with a frequency of (fl-f,) are generated. Among these cross-modulation components, the cross-modulation component (Y-20) is the cross-modulation component with the maximum energy within the frequency band of the FM luminance signal.

As mentioned above, the output signal from the reference signal source 24.

When the f4 signal is mixed and recorded/reproduced, the same cross-modulation component as explained in FIG. 6 is generated. In the test circuit 40 shown in FIG. 5, the BPF 18 has a frequency f equal to the cross modulation component (Y-2C) in FIG.
．． 742 MHz) is extracted. However, near this f component, there is a slightly higher frequency f, (629kHz in VH3 standard)
Since there is an intermodulation component with a frequency equal to the intermodulation component (y-c) in Fig. 6 (3.371 MHz according to the VH8 standard) separated by , for VH8 standard, for example f5±500
kHz, and only the f component is extracted.

The f□ multiplied signal f and the components extracted by the BPFs 17 and 18 are alternately selected by a switch 20 and supplied to a control circuit 21. In the control circuit 21, the arithmetic unit 44 calculates the f□ times signal f,
The difference XC1 in amplitude value with the component, that is, Xc=f-fs is determined, and then, in the comparator 45, this difference Xc is compared with the reference value X2 from the reference value generation circuit 23. Then, the control section 46 controls the voltage control amplifier 29 according to these differences. Even in this test mode, the previous two
As in the two test modes, the f1, f, and signals are repeatedly recorded and reproduced, and each time the control unit 46 controls the gain of the voltage control amplifier 29, the difference between the difference Xc and the reference value X2 becomes zero. I will make it happen. This results in
Regardless of the properties of the tape used, the cross modulation component (y-2G)
The mixing ratio of the FM luminance signal YFM and the low frequency converted chroma signal OL (hereinafter referred to as Y/C mixing ratio) is set so that the level of YFM remains constant.

FIG. 7 shows experimental results regarding the relationship between the Y/C mixing ratio and the cross-modulation component (Y-2C). Cross modulation component (Y-2G
) is too large, cross-beats will occur in the reproduced image, and if it is too small, the amplitude of the low-frequency converted chroma signal CL will become small and the S/N will deteriorate. Therefore, the intermodulation component (
Y-2C) needs to have a size that maximizes the S/N within a range where crossbeats do not occur, and according to experiments, it was about -23 dB. Therefore, the reference value X2 generated by the reference value generation circuit 23 is set to about -23 dB.

When the Y/C mixing ratio is the same, due to the difference in the properties of the magnetic tape, as shown in Figure 8, the cross modulation component (Y-2C)
are different in size. The above color test mode eliminates this size difference and brings it to the above optimal size. For example, when recording and reproducing tape A without going through the color test mode, the cross modulation component (Y-2C) is -28
dB, by setting the color test mode, it becomes -23 dB, which is an improvement of 5 dB.

Each of the test modes described above is performed in sequence, and when the gains of the voltage control amplifiers 8 and 29 and the characteristic curve of the recording equalizer are set and the recording test mode is completed, the video signal is recorded as described above. Therefore, regardless of the tape used, the FM luminance signal is recorded and reproduced with the best frequency characteristics and with the optimum recording current, and the Y/C mixing ratio at which the cross-modulation component has an optimum magnitude is maintained.

In FIG. 1, a recording head 1 is used as a magnetic head.
Although the recording head 11 and the reproducing head 12 are separately provided, the recording head 11 and the reproducing head 12 may be the same head.In a VHS standard VTR, a recording/reproducing head is used. It goes without saying that the above embodiments can also be applied to such a VTR.

Furthermore, if the recording head 11 and the reproducing head 12 are separate magnetic heads and the recording signal by the recording head 11 can be simultaneously reproduced by the reproducing head 12, in each of the above test modes, the reference signal It is possible to reproduce the signal from the source 24 while recording it, determine the level of the reproduced signal, and adjust the gains of the voltage control amplifiers 8 and 29 and the characteristic curve of the recording equalizer as described above. can. According to this, the adjustment period can be shortened. In this case, it goes without saying that the control circuit 21 automatically shifts to the next test mode when one test mode ends.

By the way, in a VH8 standard VTR, as shown in FIG. 9, a head cylinder 47 is provided with two magnetic heads 48 and 49 for both recording and reproduction. tape 5
Recording and reproduction are performed by repeatedly scanning 0 in order.

In the embodiment shown in FIG.
In this case, the gains of the voltage control amplifiers 8 and 29 and the characteristic curve of the recording equalizer 7 are different from those of the two recording/reproducing heads 48.
I'm sorry to say it's the same for 49.

However, the optimum recording current, optimum frequency characteristics, and Y/C mixing ratio differ not only depending on the properties of the magnetic tape but also depending on the magnetic head if the characteristics of the two magnetic heads are different. Generally, there are variations in the characteristics of magnetic heads, so in order to further improve the reproduced image quality, the optimum gain is set for the voltage control amplifiers 8 and 29 for each magnetic head, and the recording equalizer 7
It is necessary to set the optimum characteristic curve.

FIG. 10 is a block diagram showing another embodiment of the magnetic recording and reproducing apparatus according to the present invention that can realize the above, in which lla and llb are recording heads, 12a and 12b are reproduction heads, and 13a and 13b are A preamplifier, 53 is an input terminal, and 54 is a head selector switch, and parts corresponding to those in FIG. 1 are given the same reference numerals and redundant explanations will be omitted.

In the figure, similarly to the embodiment shown in FIG. 1, the reference signal generation source 24 generates the f1 signal in the recording voltage test mode, the fzyf3 signal in the frequency characteristic adjustment mode, and the f1 and f4 signals in the color test mode. The magnetic tape (not shown) is generated by the recording heads lla and llb, respectively.
Each track is recorded alternately on the top.

FIG. 11 shows the track pattern on the magnetic tape So when recording is performed in this way, where a is the track formed by the recording head lla, and b is the track formed by the recording head llb. . Further, on the magnetic tape 50, area (A) is a recording area in the recording voltage test mode, area (B) is a recording area in the frequency characteristic adjustment mode, and area (C) is a recording area in the color test mode.

Returning to FIG. 10, the reproducing head 12a is the recording head ll.
During reproduction, the reproduction head 12b reproduces and scans the track formed by the recording head lla (track a in FIG. 11), and the reproduction head 12b reproduces and scans the track formed by the recording head lla (track b in FIG. 11). , servo is applied by a servo means (not shown). Playback head 12a, 1
The reproduced signals from 2b are sent to preamplifiers 13a and 13b, respectively.
After being amplified by , the a side of the head selector switch 54 is turned on.

Supplied to side b. This head changeover switch 54 is controlled by a head changeover pulse SW input from the input terminal 53, and as a result, as shown in FIG.
Switches alternately with side b. That is, the head selector switch 54 is closed to the a side during the period when the reproducing head 12a is reproducing and scanning the magnetic tape to select the output reproduction signal of the preamplifier 13a, and closed to the side when the reproducing head 12b is reproducing and scanning the magnetic tape. Select the output reproduction signal of the preamplifier 13b.

This reproducing operation is the same when reproducing in each of the above-mentioned test modes for a recording test.

In each test mode, the reproduction signal output from the head changeover switch 54 is transmitted to the test circuit 40 via the switch 14.
The same processing operation as in the embodiment shown in FIG. 1 is performed for each test mode. The operation is alternately switched between the operation for the reproduction signal from the reproduction head 12a and the operation for the reproduction signal from the reproduction signal 12b.

That is, taking the recording voltage test mode as an example, the operation of the test circuit 40 is basically the same as that in the embodiment shown in FIG. The f□ times signals reproduced from the reproduction heads 12a and 12b are discriminated, and the control circuit 21 determines the gain of the voltage control amplifier 8 by comparing the levels of the previous reproduction f1 signal and the current reproduction f1 signal, respectively, and the recording head lla The optimum gain when recording on the tape (i & the gain that produces an appropriate recording current) and the optimum gain when the recording head llb records on the magnetic tape are determined.

Therefore, if the optimal gain of the former is G4 and the optimal gain of the latter is Gb, then when recording a color video signal from the input terminal 1, the control circuit 21 uses the head switching pulse SW from the input terminal 53 to A gain Gyu is set in the recording period voltage controlled amplifier 8 by the recording head lla, and a gain Gb is set in the recording period voltage controlled amplifier 8 by the recording head].

The above also applies to the frequency characteristic adjustment mode and the color test mode, and the control circuit 21 controls the recording head i.
The optimum characteristic curve of the recording equalizer 7 and the optimum gain of the voltage control amplifier 29 are determined for each la1 and 11b.

In this way, this embodiment can also prevent image quality deterioration due to differences in characteristics between heads.

In each of the above embodiments, test signals for a predetermined number of tracks (signals f to f4) are recorded in each test mode and then reproduced. The gain of the amplifier 8°29 and the characteristic curve of the recording equalizer 7 are sequentially changed in predetermined steps,
Thereafter, this is reproduced by the reproducing head and processed by the control circuit 21, and the level of the reproduced test signal is determined to determine the optimum gain of the voltage control amplifiers 8, 29 and the optimum characteristic curve of the recording equalizer 7. You can also
The period of recording test mode can be shortened.

FIG. 13 shows the track pattern on the magnetic tape in such a recording test mode.

In the figure, taking the recording voltage test mode as an example, when the gain of the voltage control amplifier 8 is changed by n steps during the period when the recording head records one track in this test mode, the magnetic tape formed by this recording head is 50
For example, track 55 above is 55(1), 55(2),
. . , 55(n), and the f-force signal at a different gain of the voltage control amplifier 8 is recorded in each region. The playhead is on this track 5
5 is played back sequentially from area 55 (1), but control circuit 2
1 compares the level of the reproduced f signal and the f1 signal reproduced from the previous region to determine the optimum gain of the voltage control amplifier 8 that maximizes the f□ times signal level. You can decide.

If the number of gain steps of the voltage-controlled amplifier 8 is made sufficiently large, the optimum gain can be set finely and with high precision. Double signal level detection, reproduction from previous area f1
Since the setting must be longer than the time required for processing such as level comparison with the signal, if the gain of all steps of the voltage control amplifier 8 cannot be recorded on one track, it may be recorded over a plurality of tracks.

Further, as in the embodiment shown in FIG. 10, when setting the optimum gain in the voltage control amplifier 8 for each recording head lla, llb, every other track 55, 57 formed by the recording head lla ．． ...and recording head llb
every other track 56. It goes without saying that the f-power signal is recorded in the same way in each case.

The above also applies to the frequency characteristic adjustment mode and color test mode.

[Effects of the Invention] As explained above, according to the present invention, even if there are differences in the properties of the magnetic tape used or variations in the characteristics of the head, the recording current, frequency characteristics, and Y/C mixing ratio can always be optimized. This makes it possible to record high-quality reproduced images on all magnetic tapes.

Therefore, regardless of the type of tape used, it is possible to create a soft tape that conforms to the standards, and even if a magnetic tape recorded according to the present invention is played back with any magnetic recording/playback device, high-quality playback can be achieved. You will get a picture.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIG.
Figure 3 is a diagram showing the difference in frequency characteristics of the reproduced FM luminance signal depending on the type of magnetic tape, and Figure 4 is a diagram showing the difference in frequency characteristics of the reproduced FM luminance signal depending on the type of magnetic tape.
, 2,5 MHz for response at 5 MHz
Figure 5 shows the operation of the test circuit in Figure 1 in color test mode.
The figure shows the cross-modulation between the FM luminance signal and the low-frequency conversion chroma signal, and Figure 7 shows the cross-modulation component (Y-2
0), Figure 8 is a diagram showing the difference in the magnitude of the cross-modulation component (Y -2C) depending on the type of magnetic tape, and Figure 9 is a diagram showing the difference in the magnitude of the cross-modulation component (Y -2C) depending on the type of magnetic tape. FIG. 10 is a schematic plan view showing the vicinity of the head cylinder, and FIG. 10 is a block diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the present invention.
Figure 1 is a diagram showing the track pattern on the magnetic tape in the recording voltage test mode by the recording head in Figure 10, Figure 12 is a diagram showing the operation of the head changeover switch in Figure 10, and Figure 13 is a diagram showing each of the above implementations. FIG. 7 is a diagram showing another specific example of the track pattern on the magnetic tape in the recording voltage test mode in the example. 1... Color video signal input terminal, 3...
...Y/C separation circuit, 5...FM modulation circuit,
6... Switch, 7... Recording equalizer, 8... Voltage control amplifier, 9... Adder, 11. lla, llb...recording head,
12, 12a, 12b... Playback head, 15~
18...Band pass filter, 19°20...
. . . Switch, 21 . . . Control circuit, 22.
23...Reference value generation circuit, 24...Reference signal generation source, 26...Frequency converter, 2
8... Switch, 29... Voltage control amplifier, 40... Test circuit, 41...
Arithmetic section, 42... Comparison section, 43... Control section, 44... Arithmetic section, 45...
... Comparison section, 46 ... Control section, 50.
. . . Magnetic tape, 53 . . . Head switching pulse input terminal, 54 . . . Head switching switch. Figure Figure Figure Figure Figure Rod A Figure Figure Figure

Claims (1)

[Claims] 1. In a magnetic recording/reproducing device that adds a frequency-modulated luminance signal and a low-frequency converted chroma signal and performs recording/reproduction using a recording/reproducing head, the frequency of the frequency-modulated luminance signal is a recording equalizer for setting the characteristics of the frequency-modulated luminance signal; a first voltage-controlled amplifier for setting the recording current of the frequency-modulated luminance signal; A second voltage controlled amplifier for setting a mixing ratio of the low frequency converted chroma signal to the luminance signal, and a test circuit, the test circuit changing the gain of the first voltage controlled amplifier. At each change, a first test signal having a frequency equal to the center frequency of the carrier wave of the frequency-modulated luminance signal is recorded and reproduced via the first voltage control amplifier, and the reproduction level of the first test signal is adjusted. a first control means for detecting the gain at which the recording equalizer has a maximum; a second control means for recording and reproducing a test signal through the recording equalizer and detecting a characteristic curve in which a difference in reproduction level between the second and third test signals is constant; and the second voltage control. With each change in the gain of the amplifier, the first test signal is routed through the first voltage controlled amplifier and a fourth test signal at a frequency equal to the chrominance subcarrier of the down-converted chroma signal. A test signal is recorded and reproduced through the second voltage control amplifier, and the reproduced test signal
a third control means for detecting the gain at which the difference between the level of a specific cross-modulation component of the test signal and the reproduction level of the first test signal is constant; When recording the summed signal of the chroma signal and the low frequency converted chroma signal, the first control means sets the detected gain to the first voltage control amplifier, and the second control means sets the detected gain to the first voltage control amplifier, and the second control means sets the detected gain to the first voltage control amplifier. is set in the recording equalizer, and the third control means sets the detected gain in the second voltage control amplifier. 2. In a magnetic recording/reproducing device that adds a frequency-modulated luminance signal and a low-frequency-converted chroma signal and records and reproduces it on a magnetic tape using a recording/reproducing head, the frequency characteristics of the frequency-modulated luminance signal are set. a recording equalizer for setting a recording current for the frequency modulated luminance signal; a first voltage control amplifier for amplifying the low-frequency converted chroma signal; A second voltage control amplifier for setting a mixing ratio of the low-frequency converted chroma signal, and a test circuit are provided, and the test circuit is configured to perform a second voltage control amplifier for setting a mixing ratio of the low-frequency converted chroma signal, and a test circuit that performs a first test signal having a frequency equal to the center frequency of the carrier wave of the frequency-modulated luminance signal is recorded through the first voltage-controlled amplifier while changing the gain of the first voltage-controlled amplifier in steps; a first control means for detecting the gain at which the reproduction level of the first test signal is maximum during reproduction; a period during which the recording/reproducing head records and scans the magnetic tape;
Second and third test signals of different frequencies within the frequency band of the frequency modulated luminance signal are recorded through the recording equalizer while changing the characteristic curve of the recording equalizer in a stepwise manner, and then reproduced. a second control means for detecting a characteristic curve in which a difference in reproduction level between the second and third test signals is constant; and a fourth test signal of a frequency equal to the chroma subcarrier of the down-converted chroma signal. is recorded via the second voltage control amplifier and then reproduced to determine the difference between the level of the specific cross-modulation component of the first and fourth test signals and the reproduction level of the first test signal. and a third control means for detecting the gain at which the difference is constant, and when recording a sum signal of the frequency-modulated luminance signal and the low-frequency converted chroma signal, the first control means sets the detected gain to the first voltage controlled amplifier, the second control means sets the detected characteristic curve to the recording equalizer, and the third control means sets the detected gain to the second voltage controlled amplifier. A magnetic recording and reproducing device characterized in that it is set to a voltage controlled amplifier. 3. According to claim 1 or 2, the recording/reproducing head is provided with two recording/reproducing heads, and the first control means detects the gain for each recording/reproducing head, and controls the gain for each recording/reproducing head when recording the added signal. A detection gain corresponding to a recording period of the recording/reproducing head is set in the first voltage control amplifier, and the second control means detects the characteristic curve for each recording/reproducing head to record the addition signal. At this time, a detection characteristic curve corresponding to the recording period of each recording/reproducing head is set in the recording equalizer, and the third control means detects the gain for each recording/reproducing head and adjusts the gain when recording the addition signal. , a magnetic recording/reproducing apparatus characterized in that a detection gain corresponding to a recording period of each recording/reproducing head is set in the second voltage control amplifier. 4. In claim 1, 2 or 3, the test circuit includes: a first bandpass filter that extracts the first test signal from the reproduced signal; and extracts the second and third test signals from the reproduced signal. a second band-pass filter that extracts the specific cross-modulation component from the reproduced signal; and a third band-pass filter that extracts the specific cross-modulation component from the reproduced signal; or a first supply means for supplying the second and third test signals extracted by the second bandpass filter to the second control means; A magnetic recording and reproducing device comprising: a second supply means; and a third supply means for supplying the specific cross-modulation component extracted by the third bandpass filter to the third control means. Device. 5. In claim 4, the specific cross-modulation component has a frequency (f_1 and f_4, respectively) of the first and fourth test signals.
1-2f_4), and the third bandpass filter has a passband of ±500 kHz or less with (f_1-2f_4) as the center frequency.