JPH0444801B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention has two double azimuth heads.
The present invention relates to a search playback device suitable for VTRs.

[Background of the invention]

As is well known, most general VTRs use a two-head helical scan azimuth recording method using a rotating cylinder.

Nowadays, the same deck often has two recording time modes. In this case, the standard mode determined by the standard (hereinafter referred to as SP mode) is used, and the magnetic tape running speed is reduced to 1/2 (or 1/3) in order to record for a long time while sacrificing some of the playback quality and sound quality. It also has a long-time mode (hereinafter referred to as LP mode).
The width of the recorded pattern remaining on the magnetic tape is two or three times as wide in SP mode as in LP mode, so two video heads indexed at 180° from each other are required for both modes, or a total of four. Become.

Recently, the gap between the +azimuth head in SP mode and the -azimuth head in LP mode has been made very close (so-called double azimuth head), and SP
There is a system in which the gaps between the azimuth head of the mode and the +azimuth head of the LP mode are placed very close together, and a total of two double azimuth heads indexed by 180 degrees from each other are used to function as the above four video heads.

The operation in this case will be briefly explained. First, during recording and normal playback, SP mode heads are used for both azimuths in SP mode, and LP mode heads are used for both azimuths in LP mode. During field stay playback, the SP -azimuth head and LP -azimuth head are used in SP mode, and the LP +azimuth head is used in LP mode.
Use SP + azimuth head.

That is, during special playback, even an LP mode head is used in SP mode, and conversely, an SP mode head is used in LP mode. Therefore, the head track width cannot be made extremely narrow for LP mode or extremely wide for SP mode. For example, the track pitch on a magnetic tape is in SP mode.
In the case of 20 μm and 10 μm in LP mode, it is said that the head track width is approximately 20 to 21 μm for SP and 14 to 15 μm for LP, that is, it is appropriate to make Just Track for SP and wide for LP.

When the head track width is selected as described above, during search playback, the LP mode head is selected for both azimuths in the LP mode, and the head with the maximum output among the four video heads is selected and used in the SP mode. If the SP head is used when searching in LP mode, interference from adjacent or adjacent tracks will be a problem, and if only the SP head is used when searching in SP mode, noise bands will appear in the reproduced picture, so this method is used.

Therefore, two double azimuth heads are used.
In a VTR, it is necessary to provide a reproduction amplifier for each of the four video heads in total, and the reproduction signal must be switched and output according to the operating mode.

At present, some magnetic tape video tracks are frequency-multiplexed with a pilot signal for tracking control during playback. In this case, the pilot signal has a frequency of 100 to 200 KHz, and the recording level must be about 30 dB lower than the video brightness FM signal, so the reproduction level is extremely low and should be separately amplified and output.

Furthermore, magnetic tape is wrapped around a rotating cylinder over 180 degrees, and an overlap period of about 20 to 30 degrees is provided.
Here, there is a proposal to record audio signals as PCM signals. In this case, of course, it is necessary to separate the PCM audio signal from the output of the video head and output it.

Conventionally, functions such as reproduction amplification of these four systems and selective output of video information according to the reproduction mode were performed by combining existing components, and the circuit was quite large. Also, there was no dedicated IC.
There was no precedent for a dedicated output method for pilot signals and PCM audio signals.

Furthermore, in magnetic recording of PAL color video signals, which is a chromaticity line sequential method, the direction of chroma rotation is different between adjacent tracks. It is switched for each track to match the direction of chroma rotation. PAL
Even if the double azimuth head described above is applied to a VTR for a digital camera, and the head with the maximum output is switched and selected even in the middle of one field period during search playback, the direction of chroma rotation will also be switched at the same time as this head switching is selected. Otherwise, a color fading phenomenon will occur.

[Object of the Invention] The object of the present invention is to make it possible to search and reproduce a magnetic tape on which a line-sequential color video signal such as the PAL system is recorded using a 4-head VTR without causing color fading. To provide a search playback device.

[Summary of the Invention] In order to achieve the above object, in the present invention, first and second head pairs each consisting of heads arranged at 180 degree intervals on a rotating cylinder and having different azimuth angle polarities, are arranged on one side. A magnetic tape on which a head having an azimuth angle and polarity of one pair of heads and a head having the other azimuth angle and polarity of the other pair of heads are provided in close proximity to each other, and on which a color video signal of a chromaticity line sequential system is recorded. In a magnetic recording and reproducing apparatus capable of searching and reproducing, a determination selection means for determining the magnitude of the amplitude of a reproduced signal reproduced from each head during search reproduction, and selecting and outputting a reproduced signal with the maximum amplitude. and azimuth discriminating means connected to the discriminating and selecting means and generating a control signal indicating which polarity of the azimuth angle of the head generating the reproduced signal of the maximum amplitude is connected to the discriminating and selecting means. a track jump detection means for generating a track jump signal when switching tracks; and a track jump detection means for controlling chroma rotation processing during search playback based on a control signal from the azimuth discrimination means, and a track jump detection means for generating a track jump signal from the track jump detection means. and a chromaticity signal processing circuit for correcting discontinuity of chroma rotation during track jump based on the jump signal.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is the first example, showing the internal configuration of the IC in a block diagram. The IC package is typically a 28-pin package with pins protruding on all sides (8 pins on two sides, 6 pins on the remaining two sides), and an example of the pin arrangement is also shown in the figure. Note that this number of pins does not necessarily limit the present invention.

The pins are labeled counterclockwise as shown, a to z, and α, β. 1 is the first video head (Here, it is the LP mode + azimuth head.)
This is an amplifier for amplifying the reproduced output of the amplifier, and the e pin is its input terminal. d pin is the reference of the amplifier
A terminal for applying a DC potential. Generally, a large capacitor is connected between this and the ground point.
This is an amplifier for amplifying the playback output of each of the 2 to 4 video heads (in this case, the LP mode -azimuth head, the SP mode +azimuth head, and the SP mode -azimuth head). , k pin is the previous e pin, and f,
The j and e pins have functions corresponding to the d pin mentioned above. 5 is connected in the direction shown in the figure when the first video head is in the video recording area of the magnetic tape, and conversely in the opposite direction as shown in the diagram when the second video head is in the corresponding area, so that the video recording signal is continuously transmitted. This is the first switch that can be used. 6 is a second switch that operates in the opposite phase relationship to 5, and from here on
Continuously extracts PCM audio signals. (When one video head plays back a PCM audio signal, the other video head plays back a video recording signal, so switching should be done in opposite phases.)
These switches 5 and 6 are driven by a control signal G, which is low when the first video head is in the video recording area, high when the video head in FIG. 2 is in the video recording area, and low when it is low. switch 5,
The purpose can be achieved by connecting the parts 6 as shown in the figure. Further, the functions of the third switch 7 and the fourth switch 8 correspond to the previous switches 5 and 6, respectively. Similarly, PCM audio signals are extracted continuously. The control signal H that drives these is Low when the third video head is in the video recording area, and is Low when the fourth video head is in the video recording area.
The purpose can be achieved by setting it to High and connecting switches 7 and 8 as shown in the figure when it is Low. In addition, as mentioned above, the first, fourth, and second
Since the third video head and the third video head are very close to each other, the control signals G and H have opposite phases to each other.

The third switch 9 is for selecting the PCM audio signal from either switch 6 or 8 depending on the operation mode and outputting it to the r pin. Connected in the opposite direction to that shown. It is driven by a control signal A from the n pin, for example when A is in SP mode
If it is set to High and Low in LP mode, it will be connected in the direction shown in the figure when it is Low.

The fourth switch 10 is for selecting a video recording signal from either switch 5 or 7 depending on the operation mode. During normal playback in LP mode and search playback in LP mode, move the SP in the direction shown.
During normal playback mode, connections are made in the opposite direction. Further, the outputs of the first and third video heads are switched so that they can be taken out continuously during LP mode stay playback, and the outputs of the second and fourth video heads are taken out continuously during SP mode stay playback. Also
During SP mode search playback, switching is performed to select the one with the highest output in the video recording section out of a total of four video heads. The control signal F for these is a signal A that becomes, for example, High in the SP mode, and a signal that becomes, for example, High in the stay mode.
Signal B from pin, in search mode, for example
Signal C from the α pin that goes high, when the first video head is in the LP mode and the third video head is in the video recording area when in the SP mode, for example
When the output of the amplitude detection circuit 11 that detects the output of the switch 5 and the signal D from the β pin that becomes Low and High in the opposite case is lower than the output of the amplitude detection circuit 12 that detects the output of the switch 7, It is created by a logic circuit 14 that receives a total of five control signals, including the output E of the comparator 13 whose output is, for example, High. When the control signal F is Low, the output of the video head for LP mode is selected, and when it is High, the output of the video head for SP mode is selected, and when it is Low, the switch 10 is connected in the direction shown. Then you can achieve your goal.

Note that the o pin is a connection terminal of a capacitor for detecting the output of the detection circuit 12 and the g pin of the detection circuit 11. If it is possible to incorporate a capacitor, these pins can be eliminated.

The logic circuit 14 is made up of, for example, I ² L, and the control signal F as well as the aforementioned G and H can be easily generated here.

The output of the switch 10 is further amplified by an amplifier 15 as required and output to the v pin. The t pin is a terminal for applying a reference DC potential to the amplifier 15, and a first capacitor is generally connected here.
(It would be even more convenient if the gain frequency characteristics could be adjusted by connecting a series RC circuit.)
The output of the v pin is sent to a reproduction chromaticity signal processing circuit or the like. On the other hand, after extracting the luminance FM modulation signal, it is added to the w pin and input to the AGC amplifier 16.
Here, it becomes constant regardless of the reproduction output of the AGC detection circuit 17 head and appears at the y pin. This is sent to the reproduced luminance signal processing circuit. (Since the level is constant, good DropOut detection is performed.) Note that the x pin is a connection terminal for a large-capacity detection capacitor for the AGC detection circuit 17. Also, the amplifier 15,
The AGC amplifier 16 and its detection circuit 17 are not necessarily necessary components in the present invention. The greatest intention of the present invention is to integrate at least amplifiers 1-4, switches 5-10, amplitude detection circuits 11, 12, comparator 13, and logic circuit 14 on the same chip.

The c pin is a power supply terminal for the first stage of the four amplifiers 1 to 4, and the Z pin is a power supply terminal for all other circuits. Similarly, the k pin is a ground terminal for the first stage of amplifiers 1 to 4, and the s pin is a ground terminal for all other circuits. In general, preamplifier ICs often have a gain of 60 dB or more from the input terminal (e, g, i, k pin) to the output terminal (v pin), and the feedback of the signal from the subsequent stage amplifier to the first stage amplifier is , oscillation, and poor frequency characteristics are likely to occur. Therefore, it is desirable to separate the power supply and ground for the first stage from other parts and supply them from separate pins. Further, the m pin is an input pin for a control signal that becomes, for example, High when the VTR is in the playback mode.
If the bias current in the IC flows when this pin voltage is high and is cut off when it is low, current consumption during unnecessary times can be reduced.

Next, the pin arrangement will be explained. As mentioned earlier, the input terminals of amplifiers 1 to 4 are e, g,
Feedback of signals from the downstream amplifier to the i and k pins must be suppressed as much as possible. Since AC has high impedance and is prone to signal jumps, sufficient consideration is required. ~This is a pin that is easy to excite a signal. Therefore, the former 4 pins and the latter 3 pins should be separated spatially. Also, generally the output signal level is about 0.2Vp-p at the r and y pins, and 1Vp at the v pin.
Since the voltage is about -p, special consideration must be given to the v pin. Even if signal feedback occurs and affects the frequency characteristics of the amplifiers, it is desirable to have a similar effect on the four amplifiers 1 to 4.

Therefore, as shown in the diagram, the input terminals (e, g, i, h pins) of amplifiers 1 to 4 and the output terminals (r, v, y pins) of the amplified signal are divided into two opposing sides of the IC. Deploy. Especially when the output signal level is high
The pin should be placed approximately in the center and approximately equidistant from any of the e, g, i, and k pins.

Since the d, f, j, and l pins are pins with low AC impedance in most cases, the e, g,
It is arranged narrowly between the i and k pins to prevent signal crosstalk between the input terminals of amplifiers 1 to 4. Since the x pin is a pin with low AC impedance, the isolation between the w and y pins is increased to prevent the AGC amplifier 16 from oscillating. (Since the w pin is a high impedance pin, signal jump from the adjacent v pin may be a problem, but it is not a problem since the signals are almost the same.) Also, the v pin output and the r pin output are completely different types. Since these are signals, care should be taken not to cause crosstalk with each other, but in this case there are three pins in between, and the s pin is a ground terminal, so sufficient isolation can be achieved.

Considering the pins on the other two sides, the c pin and z pin are power supply terminals, and the g pin and σ pin are large capacity capacitor connection terminals, so they have low AC impedance. The a, m, n, α, and β pins are input pins for control signals, but in many cases, the circuit that drives them has low impedance, and high-frequency signals that cause signals to jump to other pins are problematic. I never pass. Therefore, all these pins have the function of isolating between the e, g, i, k pins and the r, v, y pins.

The validity of the pin arrangement shown in FIG. 1 will be clear from the above explanation.

Next, a second embodiment will be described using FIG. 2.
In this case, the basic configuration is the same as that in FIG. 1, but the new outputs J and K from the logic circuit 14 are
It is displayed on pin and u pin. J is a rotation control signal sent to the chromaticity signal processing circuit,
K is a track jump signal during search playback.

As is well known, the chromaticity signal processing circuit rotates the phase of the chromaticity signal every horizontal period in order to eliminate crosstalk from adjacent tracks during reproduction. The directions of rotation are made to be opposite to each other depending on the azimuth direction of the video head. (There are cases where one side is rotated and the other side is not.)
Therefore, a control signal is required to inform the chromaticity signal processing circuit which azimuth of the video head outputs the reproduced signal outputted to the v pin. In particular, with the preamplifier IC of the present invention, when performing still playback, the azimuth is always +azimuth (or -azimuth).
The generation of this control signal is important because the head output is used, and during SP mode search playback, the azimuth changes at any time, resulting in a complicated operation mode. However, the signals can be in a simple format such as Low when using the +azimuth head output and High when using the -azimuth head output, so the control signals A, B, C, etc. explained earlier can be used.
It can be formed by a logic circuit 14 to which D and E are input.
By outputting the signal thus formed to the p-pin and sending it to the chromaticity signal processing circuit, this preamplifier IC can be highly functional.

On the other hand, in VTRs that use a chromaticity line sequential system such as the CCIR system, color fading occurs unless the signal processing is switched at the moment the track to be played during search playback changes. In order to correct this, it is necessary to send a track jump signal to the chromaticity signal processing circuit. Since the signal E indicating the track switching timing is input to the logic circuit 14, this signal K can also be generated by the preamplifier IC. By outputting this to the u pin, higher functionality can be achieved.

Note that both the p pin and the u pin have low impedance, and since there is no input/output of high frequency signals, there is an effect of providing isolation between peripheral pins.

Next, a third embodiment will be described using FIG. 3. In the figure, the uses of the constituent elements 1 to 17, c to l pins, σ to z pins, and β pins are the same as in FIG. 2.

In Figure 2, the control signal indicating the playback mode is
A control signal indicating the SP mode is input from the n pin, but in Figure 3 the n pin is ternary controlled, and for example, when it is High, SP mode playback,
It enables control such as LP mode playback when set to Middle and bias current cutoff when set to Low, and the previous 2 pins are integrated into 1 pin. 18 is a circuit that discriminates between these three-value modes. In addition, in Figure 2, the control signal that informs the stay mode is sent from the a pin.
The control signal that informs the search mode is input from the α pin, but in Figure 3, the m pin is ternary controlled, allowing control such as search when it is High and stay when it is Middle. Integrated into pin. Reference numeral 19 is a circuit that discriminates between these three-value modes. It is a circuit.

By using the pins reduced by implementing three-level control in this way, an output circuit dedicated to the pilot signal for tracking control was provided. The output of the switch circuit 5 on the head side for LP mode and the output of the switch circuit 7 on the head side for SP mode are connected to the seventh switch circuit 2.
0 selects any side, LPF21 removes high frequency signals such as brightness FM modulation signals, and
A low-level pilot signal with a frequency component at 200KHz is extracted. The signal is then amplified by the amplifier 22 to a sufficient level and output to the α pin. The a pin is a pin for applying a reference DC potential to the amplifier 22, and it would be convenient if the gain could be adjusted here in the same way as the t pin.

The b pin is a three-value controlled terminal; for example, when this is Low, the switch 20 moves in the direction shown in the figure.
When the switch is in the Middle position, it is connected in the opposite direction to that shown in the figure, and when it is in the High position, it operates in the same way as the switch 10.
23 is this three-value level discrimination circuit. 24 is a logic circuit for driving the switch 20 in response to the output (Y, Z) of this discrimination circuit.

By providing an output circuit exclusively for the pilot signal, this low-level signal can be used to increase the brightness.
Regardless of the level of the FM modulation signal, it can be amplified to any size and output. In addition, since the output of any video head can be selected regardless of the operation of the switch 10, it becomes possible to accurately identify tracks in each operation mode in the tracking servo system, especially during search playback, and it is possible to accurately identify the track in each operation mode, especially during search playback in the tracking servo system. High functionality is possible. Further, since the α pin, which is the output terminal for the pilot signal, outputs only a low frequency signal, there is little possibility that feedback will be applied from there to the e, g, i, and k pins. However, since it is desirable to keep them as far apart as possible, they are placed in the position shown in the figure with a z pin and a β pin that have low impedance.

In the explanation so far, for example, m, n,
Control signals input and output through p, u, α, β, and a pins
The relationship between High, Low and operation mode has been defined, but
This does not limit the invention.

We also made some regulations regarding the pin arrangement, but we arranged the input terminals of amplifiers 1 to 4 on one side.
Several modifications can be considered on the premise that the amplified signal output pins are aligned on one opposing side, and that low-impedance pins that do not carry high-frequency signals are narrowed in areas where isolation between pins is required.

Furthermore, during search playback, only the SP mode selects and outputs the one showing the maximum output from among the four heads, but this may also be done in the LP mode. It is also conceivable to increase the number of IC pins so that one can be selected depending on the voltage applied to these pins, making it even more functional. During stay playback, we decided to use the +azimuth head for SP mode and the +azimuth head for LP mode in LP mode, and the -azimuth head for SP mode and the -azimuth head for LP mode in SP mode, but the point is to use the same azimuth head. For example, it may be configured to use a +azimuth head or a -azimuth head in both LP and SP modes. It is also possible to increase the number of IC pins so that one can be selected depending on the voltage applied there. This can be easily handled by changing the logic of the logic circuit 14 to change the F and J signals.

〔Effect of the invention〕

As described above, the present invention provides a four-head type VTR having two double azimuth heads.
High-performance playback preamplifier with a rational configuration
The idea is to provide IC.

According to the present invention, complicated head output switching in the special reproduction mode, which was conventionally performed by combining existing parts, can be performed with a single chip IC.
Also, overlapping recording with the video recording signal is performed.
PCM audio signals can be switched and output.
Rotation control signals in the chromaticity signal processing circuit can be formed and output. A truck jump signal can be output. In addition, the pilot signal for tracking control, which has a low playback level, can be amplified by itself and output at a high level, and the video head channel from which the pilot signal is obtained can be arbitrarily selected by itself, which is especially useful for track discrimination during search playback. It also has the effect of making it more accurate.

It is also easy to change the head channel used during special playback, if necessary.

Furthermore, the pin arrangement has been selected to avoid feedback phenomena, which can cause performance deterioration, as much as possible, making it possible to create a high performance, highly functional, and versatile playback preamplifier integrated circuit for 4-head VTRs.

[Brief explanation of the drawing]

1 to 3 are circuit block diagrams showing embodiments of the present invention. 1, 2, 3, 4, 22...Amplifier, 5, 6,
7, 8, 9, 10, 20... switch circuit, 1
1, 12...Amplitude detection circuit, 13...Comparator, 1
4, 24...Logic circuit, 21...LPF.

Claims (1)

[Claims] 1. Arranged at intervals of 180 degrees on a rotating cylinder,
First and second pairs of heads each consisting of heads with different azimuth angle polarities are arranged such that the head of one pair of heads has a polarity of one azimuth angle and the head of the other pair of heads has a polarity of the other azimuth angle. In a magnetic recording and reproducing device that is installed close to each other and is capable of searching and reproducing magnetic tapes on which color video signals of the chromaticity line sequential method are recorded, the amplitude of the reproduction signal reproduced from each head during search reproduction is discrimination and selection means for discriminating the magnitude of the reproduction signal having the maximum amplitude and outputting the reproduced signal; azimuth discrimination means that generates a control signal indicating which one the track is; track jump detection means that is connected to the discrimination selection means and generates a track jump signal when switching tracks; and based on the control signal from the azimuth discrimination means. a chromaticity signal processing circuit that controls chroma rotation processing during search playback based on the track jump detection means and corrects discontinuity in chroma rotation during track jump based on the track jump signal from the track jump detection means; A search playback device characterized by: