JPS6346602A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To obtain an excellent picture quality by switching an equalizer characteristic of an equalizer circuit receiving a reproduced FM video signal from a common head amplifier corresponding to one recording mode of a reproduced frequency modulation video signal so as to prevent the deterioration in the S/N and frequency characteristic. CONSTITUTION:A reproduced FM (frequency modulation) luminance signal from an HPF (high-pass filter) incoming to a terminal 19 is fed to an FM equalizer 20. The equalizer characteristic of the FM equalizer 20 is changed by one or both the A mode (standard picture quality mode) discrimination signal from the terminal 21 and the B mode (high picture quality mode) discrimination signal from a terminal 22. Since the signal is reproduced and outputted while being provided with an optimum prescribed equalizer characteristic to the recording mode at the reproduction in this way, whatever the recording mode may be, the reproduced video signal with excellent S/N and frequency characteristic and excellent picture quality depending on the mode is always obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal reproducing device, and more particularly to a video signal reproducing device that reproduces a video signal recorded on a recording medium by selectively switching the carrier frequency of a frequency modulated video signal. Regarding a playback device.

2. Description of the Related Art In recent years, there has been an increasing demand for higher resolution video equipment, and various methods have been proposed. For example, a large screen display of 28 inches or more is desired to have a high resolution, and some home-use displays have a horizontal resolution of 560 TV lines, for example. In addition, in television broadcasting, research is being conducted to further increase the resolution while maintaining compatibility with the current system (for example, Journal of the Television Society Vol.

40, NH3, “Small W Collection EDTV and IDTV” (198
May 6th issue) etc.). Furthermore, among video signal reproducing devices,
Horizontal resolution 40 for video disc playback devices
Some have even achieved 0TV TV production.

In response to this trend toward higher image quality, it is desired to achieve even higher resolution in helical scan type VTRs using the low frequency conversion color recording and reproducing type. FIG. 10 shows a block diagram of an example of a reproduction system of this VTR, that is, a video signal reproduction device. In the figure, a frequency division multiplexed signal of a frequency modulated luminance signal (FMi degree signal) and a low frequency conversion carrier color signal is reproduced from the recording track on the magnetic tape by rotary heads 1 and 2, and a rotary transformer 3.4 The signal is sequentially passed through head amplifiers 5 and 6 and supplied to a switch circuit 7, where it is alternately switched for each field to form a continuous reproduced frequency division multiplexed signal. Incidentally, capacitors Ca and Cb connected between the input of the head amplifier 5.6 and the ground are for obtaining head resonance.

The reproduced frequency division multiplexed signal taken out from the switch circuit 7 is branched into two, one of which is passed through a high-pass filter (referred to as HPF).
8 and receives the reproduced FM luminance signal as a 11flP wave, while the other is outputted via a terminal 9 to a well-known color system. The reproduced FMf [if signal taken out from HPF8 is the FM equalizer 10, △GC circuit 11, limiter 1
2, the signal is supplied to the FM demodulator 13, where it is FM demodulated into a reproduced luminance signal, and then passed through a low-pass filter (hereinafter referred to as L).
(referred to as PF) 14 and 74127792 circuit 15, and is output to the output terminal 16.

The recorded video signal on the magnetic tape that is played back by such a video signal playback device is in the mode of the current VTR standard (hereinafter referred to as
In this mode (referred to as standard image quality mode or A mode), as shown in FIG. This is a frequency division multiplexed signal consisting of an FM luminance signal YA having a frequency shift and a low-pass converted carrier color signal CA having a color subcarrier frequency of 629kHz.

On the other hand, in recent years, the performance of magnetic tape and the performance of rotary heads have significantly improved. It has become possible to record and reproduce in a high-quality mode (also referred to as B-mode), which obtains high-quality images with higher horizontal resolution than images recorded and reproduced in .

Therefore, when focusing only on image quality, it is possible to configure a video signal reproducing device exclusively for the above-mentioned high-quality mode, but in the standard-quality mode (A mode), inexpensive magnetic tape can be used, and in the high-quality mode ( It has the advantage of being able to reproduce video signals recorded using a conventional standard-definition mode dedicated video signal recording device that is not capable of recording in the standard-definition mode (B mode), making it difficult to abandon the standard-definition mode. Therefore, the present invention relates to a video signal reproducing apparatus capable of switching between the A and 8 modes.

Problems to be Solved by the Invention When switching between A and 8 modes is performed using the video signal reproducing apparatus configured as described above, the video signal recorded in the high-quality mode (B mode) is as shown in FIG. ) shows the frequency spectrum, for example, the FM Terumaro signal Y8 has a carrier frequency deviation of 5.4 MHz corresponding to the sync chip level, and 7.0 MHz the carrier frequency corresponding to the white peak level, and the color sub signal Y8. A frequency consisting of a low frequency converted carrier color signal Ca with a carrier frequency of 629kHz.
1J is a several-division multiplexed signal, and the carrier frequency of the FM luminance signal is different in both modes, as shown in FIGS. 2(A) and 2(B).

For this reason, if FM equalization 10 is used in both modes as shown in FIG. 10, the characteristics will not be optimal in at least one of the modes, so the S/N ratio will be lower in the reproduced video signal.
There was a problem in that good image quality could not be obtained due to deterioration of the image quality and frequency characteristics.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a video signal reproducing apparatus that solves the above problems by switching the equalizer characteristics of a single equalizer circuit in each mode.

Means for Solving the Problems The video signal reproducing device of the present invention records the equalizer characteristics of the equalizer circuit to which the reproduced frequency-modulated video signal is supplied from a common head amplifier, in one recording of the reproduced frequency-modulated video signal. The configuration is such that switching is possible depending on the mode.

The carrier wave frequencies of the frequency-modulated video signals are different from each other.
A frequency modulated video signal is reproduced by a common head from a recording medium in which a frequency-modulated video signal is recorded in any one of the following modes (n is an integer of 2 or more). The modulated video signal is supplied to the equalizer circuit through a common head amplifier. The equalizer circuit switches the recording mode to a predetermined equalizer characteristic based on a signal obtained by determining the recording mode of the reproduced frequency-modulated video signal.

This is due to the following reason. Now, the n types of modes mentioned above are the standard image quality mode (A mode) and the high image quality mode (B mode).
mode), and the reproduction output when reproducing a recording medium on which signals of each frequency are recorded at the optimum recording current exhibits frequency characteristics as shown by the solid line in Figure 2 (C). do.

When the A-mode frequency division multiplexed signal shown in FIG. 2(A) is recorded on such a recording medium and reproduced, F
Since the reproduction output level of the lower side band of the frequency-modulated luminance signal is higher than the reproduction output level near the Mm transmission frequency, a so-called inversion phenomenon occurs. Therefore, level correction is normally performed using an equalizer circuit so that the reproduction output level near the FM carrier wave becomes higher than the reproduction output level of the lower sideband.

Figure 2 (D) shows this A-mode frequency modulated luminance signal (
This is an example of equalizer characteristics for FMff1 degree signal), where the peak level frequency (peaking frequency) is 4M
By combining the peaking characteristic I of about H2 and the peaking characteristic ■ having a peak level frequency of about 5.5 MHz, the equalizer characteristic shown by the solid line ■ is obtained as a whole. The frequency spectrum shown in FIG. 2(A) is recorded on a recording medium with the characteristics shown by the solid line in FIG. 2(C), and the FM luminance signal YA obtained by reproducing this is
) is passed through an equalizer circuit having the equalizer characteristics shown by the solid line .

On the other hand, the frequency characteristics of the playback output of a high-performance recording medium with a wide recordable and playable frequency range that can record and play back video signals in high-quality mode (B mode) are as shown by the broken line in Figure 2 (C). In this case, the FMii degree signal Y8 is divided from the B-mode video signal of the frequency spectrum as shown in FIG. 2(B) reproduced from this high-performance recording medium.
When an iP wave is passed through an equalizer circuit having the equalizer characteristics shown by the solid line (■) in FIG. Inversion phenomenon easily occurs, the frequency characteristics of the reproduced video signal are poor, and the reproduced image becomes unnatural.

Therefore, when the recording mode of reproduction FMIIIff1 is 8 mode, the equalizer circuit described above is used, for example, as shown in FIG.
), the peak level frequency 5. Peaking characteristics near sMH2 and peak level frequency 7.5MH
Solid line obtained by combining peaking characteristics V near Z
The equalizer characteristics are switched to those shown in . As a result, the B-mode reproduced FM luminance signal is given optimal equalizer characteristics and is extracted from the equalizer circuit.

Embodiment FIG. 1 shows a block system diagram of a first embodiment of the essential parts of the equipment of the present invention. In the figure, if the reproduced FM luminance signal from the HPF 8 that enters the terminal 19 is recorded on the magnetic tape in A mode (standard definition mode), the frequency will be as shown by YA in Figure 2 (A). If the image has a spectrum and was recorded in B mode (high quality mode),
As mentioned above, it has a frequency spectrum as shown by Ya in FIG. 2(B). This reproduced FM luminance signal is supplied to a 1M equalizer 20.

The 1M equalizer 20 is configured so that its equalizer characteristics can be changed based on either or both of the A mode discrimination signal from the terminal 21 and the B mode discrimination signal from the terminal 22. The equalizer characteristics of the 1M equalizer 20 are as shown in Figure 2 (D) when the reproduced FMR4 degree signal is in A mode.
When the reproduced FMi degree signal is in the B mode, the frequency characteristic as shown by the solid line ■ in FIG. 2F is selected. This 1M equalizer 20
The reproduced FM degree signal from the output terminal 23 is supplied to the reproduction system after the AGC circuit 11 in FIG.

Next, specific embodiments of the 1M equalizer 20 shown in FIG. 1 and modifications thereof will be described with reference to FIGS. 3 to 6. FIG. 3(A) shows a specific circuit of the first embodiment of the F1 equalizer, in which the same components as in FIG. 1 are given the same reference numerals. In FIG. 3 (A>), the reproduced FM luminance signal is supplied to the base of the NPN transistor Q1 via the input terminal 19, amplified here, and outputted from the collector of QI to the output terminal 23.

When the recording mode of the input reproduced FM luminance signal is A mode, the switch circuits SW2 and SW3 are connected to the terminal 21a.
and 21b, and the switch circuits S W + and SWa are turned off. Therefore, between the collector of transistor Q1 and power supply voltage +Vcc,
A first circuit consisting of a capacitor Clx coil L1 and a resistor R1.
A resistor Ra is connected in series to a parallel resonant circuit, and a first series resonant circuit consisting of a coil L3, a capacitor C3, and a resistor R3 is connected in parallel to the emitter resistor Rb between the emitter of the transistor Q1 and the ground. The configuration is as follows: coil 12, L4, capacitor C21Ca
, resistance R2, and Ra are equivalent to not existing.

The frequency characteristic of one of the first parallel resonant circuit and the first series resonant circuit described above is selected to be one of the peaking characteristics indicated by the broken line and ■ in Fig. 2 (D), and the frequency characteristic of the other resonant circuit is The frequency characteristic is selected to be the other peaking characteristic. For this reason, the output terminal 23 has the frequency characteristics indicated by the solid line ■ in FIG. 2(D). degree signal is extracted.

On the other hand, when the recording mode of the input reproduced FM luminance signal is B mode, the switch circuits SW + and SWa are connected to terminal 2.
The switch circuits SW 2 and SW 3 are turned on by the input signals 2a and 22b, respectively, and turned off. Therefore, the collector of transistor Q1 and the power supply voltage +Vc
between capacitor C2, coil L2 and resistor R2
A resistor Ra is connected in series to a second parallel resonant circuit consisting of a coil LJ, a capacitor C4, and a resistor R4, and a resistor Rb is connected between the emitter of the transistor Q1 and the ground. The configuration is connected in parallel, with coils L+, L3, capacitor C+,
Cm, resistance Rt, and R3 are equivalent to not existing.

One of the second parallel resonant circuit and the second series resonant circuit described above is selected to have one of the peaking characteristics t1 and V shown in Fig. 2 (F), and the other resonant circuit is selected to have the other peaking characteristic. It is. Therefore, the input reproduction FMIEi of B mode
The frequency signal is given an equalizer characteristic indicated by a solid line ▪ in FIG.

Next, a modification of this embodiment will be described. Figure 3 (△)
The circuit shown in Figure 1 uses a small number of coils, but since the coils occupy a large area especially when high-density packaging is performed, it is desirable to have as few coils as possible. Therefore, an example in which the number of coils is reduced is shown in FIG. 3(B). In the same figure (B), Figure 3 (
Components that are the same as those in A) are given the same reference numerals and their explanations will be omitted.

In Fig. 3(B), coil 1' and capacitor C1
' and a parallel resonant circuit consisting of a resistor R1' and a coil L3.
', a series resonant circuit consisting of a capacitor C3' and a resistor R3' provide A-mode equalizer characteristics, and a parallel resonant circuit consisting of a coil L1', a capacitor C2' and a resistor R2', a coil L1', a capacitor C4' B-mode equalizer characteristics are provided by a series resonant circuit consisting of a resistor Ra' and a resistor Ra'. The resonant frequency of these resonant circuits can be given by selecting the capacitance value of the capacitor, and the sharpness (Q) of the resonance can be set to an appropriate equalizer characteristic by selecting the resistance value.

Next, a second embodiment of the present invention will be described. 1st above
In the embodiment, two peaking frequencies were independently set for each of the A and B modes. However, the A and B modes are, for example, as shown in FIG. 2 (A).

In the case of the spectrum arrangement shown in (B), the peaking frequency of the high frequency side peaking characteristic ■ in the case of A mode shown in the same figure (D) and the case of B mode shown in the same figure (F) It is possible to share the peaking frequency (5.5M1-IZ in this embodiment) with the peaking frequency of the low-frequency side peaking characteristic (2). This embodiment was created in view of the above points, and FIG. 4(A) shows a specific circuit diagram of this second embodiment, and the same components as in FIG. 3(A) are denoted by the same reference numerals. , and the explanation thereof will be omitted.

In FIG. 4(A), the above shared peaking frequency is provided by a capacitor C5 and a coil L5 connected to the collector side of the transistor Q+, and a resistor connected in parallel to the parallel circuit of Cs, Ls and a resistor R5A. Rs.
Q at this common peaking frequency can be changed by the switch circuit S W s in the series circuit of e and the switch circuit SWs. Among the A and B modes, in the mode in which Q is smaller at this peaking frequency in order to obtain good reproduced image quality, the switch circuit SWs is turned on by the mode discrimination signal from the terminal 25. In addition, the resistance R
The values of 5A and Rsa are set to provide the optimum Q in each mode.

Further, in the A mode, the switch circuit S"Ws is turned on, and the above-mentioned peaking characteristic (■) is given by the series resonant circuit consisting of the coil L6, the capacitor C6, and the resistor R6. On the other hand, in the B mode, the switch circuit S"Ws is turned on.
is turned on, and the peaking characteristic V
is given.

FIG. 4(B) is a modification of the second embodiment of the FM equalizer 2o shown in FIG. 4(A), and the same components as in FIG. 4(A) are given the same reference numerals and their explanations are omitted. Fourth
In the circuit shown in figure (B), capacitor C5 and coil L
A series circuit consisting of resistors R5A' and Rse' is connected in parallel to the parallel circuit of 5, and a switch circuit SWs' is connected in parallel to the resistor Rsa'.

As a result, in the mode in which it is desirable to have a smaller Q at the common peaking frequency in order to obtain good playback image quality among both modes A and B, the switch circuit SWs'
is turned on, and when the mode is such that a larger Q is better, S
Ws' is turned off.

FIG. 4(C) shows yet another modification of the second embodiment of the FM equalizer 20, and in FIG. 4(A) and (B-), A
, B, the common peaking frequency of both modes is set to transistor Q.
In this modification, what was obtained by the parallel resonant circuit on the collector side of transistor Q1 is obtained by the series resonant circuit on the emitter side of transistor Q1. That is, the common peaking frequency is given by a series resonant circuit consisting of a coil +6, a capacitor CIo, a resistor RIIIA, and a resistor Rn+e.
When the reproduced FM luminance signal in the mode in which good reproduced image quality is obtained when the Q at the peaking frequency is larger, the switch circuit SW 10 is turned on based on the input signal of the terminal 26, and the switch circuit SW 10 is turned on based on the input signal of the terminal 26, ; ++o is disconnected from the circuit.

On the other hand, the peaking characteristic I is applied to the collector side of the transistor Q1 by a parallel resonant circuit consisting of a capacitor C8, a coil L8, and a resistor R8, with the switch circuit S W a turned on and S W s turned off in the A mode. and when in B mode, switch circuit SW8 is turned off.
When SW9 is turned on, the peaking characteristic V is given by the parallel resonant circuit made up of the capacitor C9, the coil L3, and the resistor R9. Note that the Q of the common peaking circuit may not be switched, but a resistor having a common resistance value that allows the image quality to be practically acceptable in each mode may be connected.

Next, a third embodiment of the FM equalizer 20 is shown in FIG. 5(A), and modifications thereof are shown in FIGS. 5(B) to (E), respectively. In each figure, Figure 1, Figure 3 (A) and Figure 5 (A),
Components that are the same as those in (B) are given the same reference numerals, and their explanations will be omitted. The circuits shown in Figures 4(A) to (C) required three coils, but the circuits shown in Figures 5(A) to (E) required three coils, but the number of coils was further reduced to two. It is a circuit.

FIG. 5 (A>) shows a coil L11 provided on the emitter side of the transistor Q1, as in the circuit shown in FIG. 4 (C).
A, B
Another peaking characteristic that differs between both modes 1. The peaking frequency of V and switching of Q are performed by a parallel resonant circuit on the collector side of transistor Q1.

In other words, the switch circuit S W ++ which is turned on only in the A[- mode] causes the capacitor C12 to be turned on in the A mode.
, the coil L12, the resistor R12, the capacitor CI3, and the resistor R13 constitute a parallel resonant circuit, and the above-mentioned peaking characteristic (2) is obtained. On the other hand, in the B mode, the switch circuit S W n is turned off, so the transistor Q
The parallel resonant circuit on the collector side of No. 1 consists of only a capacitor C12, a coil L+z, and a resistor R12, and thereby the peaking characteristic V described above is obtained. Note that in the circuit shown in FIG. 5(A), A.

Although the Q at the peaking frequency common to both B modes cannot be switched, the Q can be changed by dividing the resistor Ru and connecting or disconnecting one side with a switch circuit, as shown in Figure 4 (C), for example. Can be switched.

Each modification shown in FIGS. 5(B) to 5(D) is A.

B Capacitor CI4 and coil L1 with peaking characteristics common to both modes are provided on the collector side of transistor Q1.
A
, B modes are configured to generate another peaking frequency which is different between the two modes by switching with a series resonant circuit on the emitter side of 01. That is, in the case of FIG. 5(B), the series resonant circuit on the emitter side of the transistor Q1 described above is A.
In the mode, the switch circuit SW +2 is turned on, and the capacitor Cl5 is connected in series with the coil L15 and the resistor R+s.
In contrast to the configuration in which the parallel circuits A and Ca5e are connected, the switch circuit S W +2 is turned off in the B mode, so that the capacitor Ca5e is disconnected.

In addition, in the circuit shown in FIG. 5(C), the switch circuit 5WI3, which is turned on only in the A mode, connects the capacitor C+so in series only in the B mode to the series resonant circuit consisting of the capacitor Cl5C% coil L+s and the resistor R+s. Add to.

Furthermore, in the circuit shown in FIG. 5(D), the transistor Q1
The circuit on the emitter side of is configured by a switch circuit 5W14 that is turned on only in A mode and a switch circuit S W +s that is turned on only in B mode.
, a series resonant circuit b< +M consisting of a capacitor C+SE and a resistor RISE is formed, and in the B mode, the coil L15
, a series resonant circuit consisting of a capacitor Cl3F and a resistor RI5F is constructed. According to the modification shown in FIG. 5(D), the Q of the emitter-side resonant circuit can be adjusted in each mode.

Furthermore, in the circuit shown in FIG. 5 (A>), the transistor Q1
The value of the resistance component that determines the Q of the parallel resonant circuit on the collector side of is smaller in the A mode than in the B mode, but here is a modified example in which the value can be determined independently in both modes. It is shown in FIG. 5(E). In FIG. 5(E), in the △ mode, the switch circuit S W +s is turned on and the capacitor C! is connected to the coil L+z. 3A and the resistor R13A are connected in parallel, and in the B mode, the switch circuit SW17 is turned on, and the capacitor CI3[] and the resistor R11B are connected in parallel to the coil L12.

Next, a fourth embodiment of the FM equalizer 20 is shown in FIG. 6 (Δ), and a modified example thereof is shown in FIG. 6 (B).

In the embodiment described above, the two peaking characteristics used for equalization in both the Δ and B modes are both FM
It was made by Ikoraza. However, in a magnetic reproducing device, as shown in FIG.
, inductance due to rotary transformer 3.4,
Capacitor C installed at the input stage of head amplifier 5°6
a and Cb, it is possible to perform peaking due to so-called head resonance. Therefore, in this embodiment and its modification, this head resonance is used for any one of the peaking characteristics in equalization described above.

FIG. 6(A) shows a circuit of the FM equalizer 20 when the values of the capacitors Ca and Cb are selected so that the peaking characteristic V on the high frequency side in B mode is provided by head resonance. In FIG. 6(A), capacitor C16 and coil L on the collector side of transistor Q+
The parallel resonant circuit consisting of +s and resistor R+6 provides a common peaking characteristic for both A and 8 modes, and in A mode, the switch circuit S W +a is turned off and Ql
A series resonant circuit consisting of a resistor R17As, a capacitor C17, a coil LI7, and a resistor Rays is formed on the emitter side of the resistor R17 to provide the peaking characteristic (2). On the other hand, in the B mode, the switch circuit SW+a is turned on, and the coil L
17 and resistor R178 are short-circuited to ground, and a series resonant circuit is not formed on the emitter side of transistor Q1, and resistor R178 is shorted to ground.
A series circuit consisting of 17A and capacitor CI7 is resistor R.
b is connected in parallel.

As a result, in the B mode, the circuit shown in FIG. 6(A) exhibits a peaking characteristic (2) on the low frequency side or a simple high frequency emphasis characteristic having a characteristic similar thereto.

Since the other peaking characteristic V in the B mode is caused by head resonance, the FM equalizer does not particularly peak at this frequency. In addition, the above-mentioned high frequency emphasis characteristic is not performed,
The circuit configuration on the emitter side of the transistor Q1 may be changed to include only the emitter resistor Rb.

The circuit shown in FIG. 6(B) provides a peaking characteristic common to both modes A and B on the emitter side of Ql, and coil LL9.
A series resonant circuit consisting of capacitor CI9 and resistor R+s is connected in parallel to resistor Rb, and in A mode, switch circuit SW+s is turned on and capacitor C1
8. A parallel resonant circuit consisting of a resistor R+s and a coil L's is formed on the collector side of 01 to provide another A-mode peaking characteristic. On the other hand, in the B mode, the switch circuit SW19 is turned off, so a parallel resonant circuit is not configured on the collector side of the transistor Q1, and a parallel circuit of the coil L's and the resistor R+s is connected to the resistor Ra.
The circuit shown in FIG. 6(B) simply exhibits high-frequency emphasis characteristics.

In addition, in place of the switch circuit SW 1s, by providing a switch circuit that short-circuits both ends of the parallel circuit consisting of the capacitor C18, the resistor R+s, and the coil 18 only in the 8 mode, the above-mentioned high frequency range can be reduced in the B mode. Emphasis characteristics can also be turned off.

In addition, in A mode, head resonance suitable for B mode emphasizes bands that are not originally needed, resulting in poor S/N, but in order to avoid this, FM demodulation is required from the head amplifier In the circuit system up to device 13, the head resonance frequency trap circuit and low-pass filter are inserted only when the reproduced FM luminance signal is in A mode. The band can be attenuated.

Of course, if the above S/N deterioration is tolerable in practice,
It is not necessary to insert or connect the trap circuit or low-pass filter described above.

Next, FIG. 7 (A
) and (B). As explained in conjunction with FIGS. 3 to 6, the FM equalizer 20 shown in FIG. The FM equalizer 30 of this embodiment has a main equalizer 31 as shown in FIG. 7 (A>).
and correction equalizer 32 in a cascade connection configuration, which costs ¥1.
have symptoms.

The main equalizer 31 is, for example, an 8-mode equalizer, and the correction equalizer 32 corrects the B-mode equalizer characteristics (■ in Figure 2 (F)) to create the A-mode equalizer characteristics (■ in Figure 2 (D)). It is an equalizer that obtains. This allows the input reproduced FM luminance signal to be input to the main equalizer 3.
1 and the correction equalizer 32, the reproduced FMiti degree signal to which the A-mode equalizer characteristic is applied is extracted to the output terminal 33, and the B-mode equalizer characteristic is output from the main equalizer 31 to the output terminal 34. A reproduced FM luminance signal to which characteristics have been added is extracted.

FIG. 7(B) shows the FM equalizer 30 shown in FIG. 7(A).
This is a circuit diagram of an embodiment of the present invention, and the same components as those in FIG. By selecting the constants of the resonant circuit on the emitter side of the NPN transistor Tr+ and providing one of the peaking characteristics of the B mode by the head resonance, equalizer characteristics for the B mode are created, and each of the emitter side and collector side of the PNP transistor Tr3 is Correcting is performed using the constant of the resonant circuit to obtain equalization characteristics for A mode. Note 1. ', I P N transistor Tr2 and NPN transistor Tr+ are emitter followers.

Next, FIG. 8 (A
) and the same diagram (B).

This will be explained together with the circuit diagram (C). Figure 8 (A)-(C)
Inside, the same components are given the same reference numerals. The FM equalizer 36 of this embodiment has a main equalizer 37 and a correction equalizer 38 connected in series, and the correction equalizer 38 has a configuration in which the equalizer characteristics can be switched between the two modes by a mode discrimination signal from three terminals. It is something.

Figure 8 (,B) shows the FM equalization [A36] of Figure 8 (A).
1 shows a circuit diagram of an embodiment of the invention. Main equalizer 37 is N
The correction equalizer 38 consists of a PN transistor Tr5ri, a PNPI transistor Tra, a resonance circuit on its collector and emitter side, and a switch circuit SW2Ll, S
It consists of W21 etc. Each of the switch circuits SW20 and SW2+ is turned on only in the A mode. A signal taken out from the collector of the transistor Trs is outputted via the base and emitter of the PNP transistor Tr7, which is an emitter follower.

Another specific circuit of the FM equalizer 36 shown in FIG. 8(A) is shown in FIG. 8(C). In FIG. 8(C), the constants of the feedback circuit of the differential amplifier 41 provide peaking characteristics common to both modes, and the NPN
Transistor Tr7, switch circuit SWZ! ,5W23
The characteristics of the correction equalizer 38 consisting of the following can be changed by switching the external constant of Try between A and 8 modes. The switch circuit 5W22 is turned on only in A mode by the signal from the terminal 39a, and the switch circuit 5W23 is turned on by the signal from the terminal 39a.
It is turned on only in B mode by a signal from b. It goes without saying that the equalization by the feedback circuit of the differential amplifier 41 may be performed by external constants of the transistors as in other embodiments.

In the present invention, the main equalizer and the correction equalizer do not necessarily need to be directly connected in cascade, and modifications as shown in FIGS. 9A to 9C can be considered. In FIGS. 9(A) to 9(C), the same components as those in FIG. 10 are designated by the same reference numerals, and their actual use will be omitted. Also, the 9th
In Figures (A) to (C), the head 2, rotary transformer 4, head amplifier 6, capacitor Cb1 switch circuit 7, etc. are omitted for the sake of simplification. Furthermore, in FIGS. 9(B) and 9(C), subscripts a and b indicate circuits for A and BE-does. As shown in FIG. 9(A), the main equalizer 43 (31, 37) and the correction equalizer 44 (
32, 38), other circuits such as the AGC circuit 11 may be inserted between them. AGC circuit 1 inside the head amplifier IC
1 is built-in, the circuits before the AGC circuit 11 are mounted around the drum in this way, and the circuits after the correction equalizer 44 are mounted elsewhere, thereby reducing the scale of the circuits to be mounted around the drum. Since it is small, it has the advantage that this circuit can be mounted in a small place.

In addition, especially when different outputs are provided in each mode as shown in Fig. 7 (△), the circuits after the limiters 12a and 12b are also made into separate circuits in both modes as shown in Fig. 9 (B).
Each equalizer output terminal may be connected to subsequent circuitry for each mode. In this case, all the circuits after the limiter do not need to be separate circuits; for example, as shown in Fig. 9 (C
), in order to share the 1M demodulator 13, a switch circuit 45 is provided on its input side, and an LPF 14a is provided.

It is also possible to have a configuration in which the 14b1 system support circuits 15a and 15t) are provided separately and their outputs are switched by the switch circuit 46.

It should be noted that the invention is not limited to the above-mentioned embodiments; for example, the frequency modulated video signal is not limited to the FM luminance signal, but may also be used, for example, as an FM composite color video signal.

An FM time-division multiplexed video signal, an FM color signal, etc. may be used, and the present invention can be similarly applied to three or more modes. The present invention can also be applied to 4-head VTRs other than 2-head VTRs.

Effects of the Invention As described above, according to the present invention, an FM video signal recorded in any one of a plurality of modes is given a predetermined equalizer characteristic that is optimal for that recording mode at the time of playback. Therefore, regardless of the recording mode, it is possible to always obtain a reproduced video signal with good S/N ratio, good frequency characteristics, and good image quality specified for that mode. It is something that you have.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the main part of the present invention, FIG. 2 is a diagram showing a frequency spectrum for explaining the present invention,
3 to 6 are diagrams showing respective embodiments of specific circuits of the circuit shown in FIG. 1 and modifications thereof, and FIGS. 7(A) and (B)
8A and 8B are block diagrams of a second embodiment of the main part of the present invention and a circuit diagram of one embodiment thereof, respectively, and FIGS. 8A and 8B are blocks of a third practical example of the main part of the invention, respectively. A system diagram and a circuit diagram of one embodiment thereof, FIGS. 9A to 9C are block system diagrams showing other modifications of the present invention, and FIG. 10 is a block system diagram showing an example of a conventional device. 19... Reproduction FM brightness signal input terminal, 20.30°3
6-F M -1': I riser, 21.21a, 21
b-...A mode discrimination signal input terminal, 22.22a, 2
2b...B mode discrimination signal input terminal, 23.33.3
4... Output terminal, 31.37.43... Main equalizer, 32.3.8.44... Correction equalizer, 3
9...Mode discrimination signal input terminal. Patent Applicant: Victor Company of Japan Co., Ltd. )

Claims (3)

[Claims] (1) From a recording medium on which a frequency-modulated video signal is recorded in any one of n types of modes (where n is an integer of 2 or more) in which the carrier wave frequency of the frequency-modulated video signal is different from each other. A video signal reproducing device that reproduces a recorded frequency-modulated video signal using a common head and a head amplifier, in which the equalizer characteristics of an equalizer circuit to which the reproduced frequency-modulated video signal that has passed through the head amplifier is supplied are Video signal reproduction characterized in that, among the equalizer characteristics of the frequency modulated video signal in n types of modes, switching is made to one equalizer characteristic corresponding to one recording mode of the reproduced frequency modulated video signal. Device. (2) The equalizer circuit generates equalizer characteristics of two types of modes as composite characteristics of a plurality of peaking circuits, and in the equalizer characteristics of the two types of modes, a part of the constant of the peaking circuit is generated in the two types of equalizer characteristics. Claim 1 characterized in that it is configured to be shared in the mode of
The video signal reproducing device as described in . (3) The equalizer circuit has a cascade connection configuration of a first equalizer circuit section and a second equalizer circuit section, and one of the first and second equalizer circuit sections is of two types among the n types. 2. The video signal reproducing device according to claim 1, wherein the video signal reproducing device has common equalizer characteristics for the modes.