JPH024545Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is equipped with a pair of main heads and a pair of sub-heads, and is based on the selection switching of each head and the control of a different (inverted) color phase for each track of the tape. For helical scan video tape recorders that perform standard playback, slow-motion playback, still playback, frame advance, and other special playback, it is now possible to switch the color phase appropriately regardless of the playback status with simple gate processing. The aim is to provide a video tape recorder with

Traditionally, helical scan type video tape recorders, such as helical scan β type video tape recorders, have not only standard playback functions but also special playback functions such as still playback and slow motion playback. In order to eliminate noise in the reproduced image at the time, two main heads M1 and M2, one and the other with mutually opposite azimuths, are attached to the rotating cylinder C, as shown in FIG.
are provided facing each other at 180°, and the other main head M
One of the sub-heads S1 having the same azimuth as 2 is provided in the vicinity of one of the main heads M1, that is, at a position separated from one of the main heads M1 by an integral multiple of the length of one horizontal section of the reproduced image.
The other sub-head S2 with the same azimuth as the main head M2 is placed near the other main head M2, that is, the other main head M2.
In the case of Fig. 1, both sub-heads S1 and S2 are located one horizontal section length away from each of the main heads M1 and M2. When the two main heads M1 and M2 are in the standard playback state, each track of the tape is scanned alternately, and in the stationary playback state, the main head and the subhead have the same azimuth, for example, one main head M1 and the other. The sub head S2 of the tape repeatedly scans the same track on the tape, and furthermore, in the slow motion playback state in which playback is performed at one third of the running speed in the standard playback state, each odd track on the tape is scanned repeatedly. , for example, by one main head M1 and the other sub-head S2.
1. The other sub head S2 and one main head M1 are scanned three times in this order, and each even track of the tape is scanned, for example, from the other main head M2.
and one sub-head S1, the other main head M2, one sub-head S1, and the other main head M2.
Repeat scanning three times in this order.

In addition, when forming a color reproduction image based on the reproduction output of each head M1, M2, S1, S2,
Each head M1, M2, S1, S2 and each head M
1, M2, S1, and S2, and since the color phase of each track on the tape is inverted, it is necessary to perform color phase inversion control using a so-called color switching signal.

The head switching signal is the periodic RF pulse signal shown in Fig. 2 which is inverted every half cycle of cylinder C in synchronization with head scanning, for example a 30 Hz RF pulse signal, and the reproduction control pulse signal, that is, in the standard reproduction state. It is formed using a reproduction control pulse signal that has a frequency of 30 Hz and changes in frequency depending on the traveling speed. In FIG. 2, "1" indicates a logic 1 level, and "0" indicates a logic 0 level.

By the way, each head M1 in each reproduction state,
Switching of M2, S1, and S2 is shown in Figures 3 and 4.
To explain with reference to the figure, as shown in Figure 3,
The RF pulse signal shown in FIG. The control pulse is transmitted to the control pulse input terminal Ib. The reproduction state changeover switch 2 includes a grounded standard contact Pb, a slow motion contact PC, and a switching piece x.

Then, the RF pulse signal at the RF pulse input terminal Ia is transmitted to the first bistable multivibrator 4a and the first and second AND gates 5a and 5b via the inverters 3a and 3b, and the first inverter 3a
The RF pulse signal via the third AND gate 5c
transmitted to.

Further, the reproduction control signal of the control pulse input terminal Ib is transmitted to the first AND gate 5a via the first and second monostable multivibrators 6a, 6b and the third inverter 3c, and is transmitted from the first AND gate 5a to the first AND gate 5a. 1. When the second bistable multivibrator 4a and 4b is in a slow motion playback state where the running speed is 1/3 of the standard playback state, that is, one of the odd tracks of the tape.
one main head M1, the other sub head S2,
One main head M1 is scanned in this order, and then one of the even-numbered tracks adjacent to the odd-numbered track on the tape is scanned.
One is the other main head M2, one is the sub-head S1,
When scanning is repeated in the order of the other sub-head M2, for example, a gate pulse that becomes "1" is output only during the period when one main head M1 is always scanning, and the gate pulse of "1" causes both the main heads to be scanned. Stable multivibrators 4a, 4b are reset.
In addition, when the running speed is 1/3 of the standard playback state,
The frequency of the playback control signal, which is 30Hz in standard playback mode, becomes 10Hz.

Then, the first bistable multivibrator 4a is triggered by the rising edge of the RF pulse signal via the second inverter 3b, and the second bistable multivibrator 4b is triggered by the rising edge of the non-inverted output pulse of the first bistable multivibrator 4a. , a non-inverting output pulse is output from the non-inverting output terminal Q of the first bistable multivibrator 4a, which becomes "0" only during the period when the other main head M2 scans after one sub-head S1. At the same time, the bistable multivibrator 4a
An inverted output pulse, which is an inverted version of the non-inverted output pulse, is output from the inverted output terminal of the second bistable multivibrator 4b, and one main head M1 is then scanned by the other sub-head S2 from the non-inverted output terminal Q of the second bistable multivibrator 4b. A non-inverted output pulse that becomes "0" only during this period is output, and an inverted output pulse obtained by inverting the non-inverted output pulse is output from the inverted output terminal Q of the bistable multivibrator 4b.

Further, the non-inverted output pulse of the first bistable multivibrator 4a is transmitted to the third AND gate 5c, and the inverted output pulse of the bistable multivibrator 4a is transmitted to the second AND gate 5b, and the second bistable multivibrator 4a is transmitted to the second AND gate 5b. The non-inverted output pulse of the multivibrator 4b is transmitted to the second AND gate 5b, and the inverted output pulse of the bistable multivibrator 4b is transmitted to the third AND gate 5c.

Then, a gate pulse that becomes "1" only during the scanning period of one sub-head S1 is output from the second AND gate 5b to the first NOR gate 6a, and a gate pulse that becomes "1" is output from the third AND gate 5c to the first NOR gate 6a. A gate pulse that becomes "1" is output only during the scanning period of the sub-head S2, and the gate pulse that becomes "1" is output from the first NOR gate 6a to the slow motion contact pc of the reproduction state changeover switch 2.
A gate pulse that becomes "1" only during the scanning period of each of the two is output.

Therefore, by switching the switching piece x of the playback state changeover switch 2, the switch 2
A head switching signal of "0" is always output from the switching piece x in the standard playback state, and a "0" head switching signal is output based on the RF pulse signal when one main head M1 and the other subhead S2 are in a static playback state in which the tape is scanned. A head switching signal that alternately changes to "1" and "0" is output, and in the slow motion reproduction state, a head switching signal based on the gate pulse of the NOR gate 6a is output.

On the other hand, the reproduction outputs of both main heads M1 and M2 are amplified by first and second preamplifiers 7a and 7b, respectively, and both subheads S1 and S2
The playback outputs of the 3rd and 4th preamplifiers 7 respectively
c, 7d, and each amplifier 7a.
-7d are transmitted to the first to fourth switch circuits 8a, 8b, 8c, and 8d, respectively, and at this time, the first and second switch circuits 8a, 8
A head switching signal from switching piece x of switch 2 is transmitted to switch 2b, and a head switching signal via fourth inverter 3d is transmitted to third and fourth switch circuits 8c and 8d.

Therefore, as shown in the head switching signal column of FIG. 4, in the standard playback state, the first,
A head switching signal of "0" is always transmitted to the second switch circuits 8a and 8b, and both switch circuits 8a and 8b
As a and 8b continue to be turned on, a head switching signal of "1", which is the inversion of the head switching signal of always "0", is transmitted to the third and fourth switch circuits 8c and 8d, and both switch circuits 8c and 8d are turned on. The outputs of the first and second preamplifiers 7a and 7b via the first and second switch circuits 8a and 8b, that is, the playback outputs of both main heads M1 and M2, are output to the first and second video outputs. Amplifier 9
a, 9b to the fifth and sixth switch circuits 8e and 8f, respectively, and at this time, the on/off of the fifth switch circuit 8e is controlled by the RF pulse signal, and the RF pulse signal is transmitted to the sixth switch circuit 8f. The on/off state is controlled by the RF pulse signal inverted by the fifth inverter 3e, and both switch circuits 8e and 8f are turned on alternately at the cycle of the RF pulse signal, and both main heads M1 and M2 each scan the tape. Both switch circuits 8
Both main heads M1 and M2 via e and 8f, respectively
The respective playback outputs are transmitted to the third video amplifier 9c, and the playback outputs of both main heads M1 and M2 via the video amplifier 9c are transmitted to the seventh switch circuit 8g.
The signal is transmitted to the playback output terminal Oa via the playback output terminal Oa. In addition,
The on/off state of the seventh switch circuit 8g is controlled by the head switching signal.

Next, when one of the main heads M1 and the other sub-head S2 is in a static playback state in which the tape is scanned, the first and second heads are selected from the switching piece x of the switch 2, as shown in the head switching signal column of FIG. 2
A head switching signal that alternately changes to "1" and "0" in synchronization with the RF pulse signal is transmitted to the switch circuits 8a and 8b and the fifth and seventh switch circuits 8e and 8g. The inverted head switching signal is transmitted to the four switch circuits 8c, 8d and the sixth switch circuit 8f.
While the switch circuits 8a and 8b and the fifth and seventh switch circuits 8e and 8g are turned off, the other subhead S2 scans the tape, and the playback output of the other subhead S2 is transferred to the fourth preamplifier 7d and the fourth preamplifier 7d. It is transmitted to one horizontal delay circuit 10 via the four switch circuit 8d, the second video amplifier 9b, the sixth switch circuit 8f, and the third video amplifier 9c, and the reproduction output of the other subhead S2 corresponds to the length of one horizontal section. 1
After being delayed by a horizontal period, it is transmitted to the reproduction output terminal Oa. Further, while the first and second switch circuits 8a and 8b and the fifth and seventh switch circuits 8e and 8g are turned on by the head switching signal of "0", one main head M1 scans the tape, and one The playback output of the main head M1 is transmitted to the playback output terminal Oa via the first switch circuit 8a, first video amplifier 9a, fifth switch circuit 8e, third video amplifier 9c, and seventh switch circuit 8g.

Furthermore, in the slow motion playback state, as shown in the column of head switching signals in FIG. 8g, a head switching signal that becomes "1" only during the period when both subheads S1 and S2 scan the tape is transmitted, and each even-numbered track of the tape is switched between the other main head M2, one subhead S1, and the other subhead M2. While the main head M2 is sequentially scanning, the playback outputs of the other main head M2 and one of the subheads S1 are transmitted to the playback output terminal Oa, and each odd track of the tape is transferred to one of the main heads M1 and the other. While the sub-head S2 and the main head M1 are sequentially scanning, the reproduction outputs of the main head M1 and the sub-head S2 are transmitted to the reproduction output terminal Oa.

That is, in the standard playback state, main heads M1 and M2 are selected by a head switching signal of "0", and during static playback in which one main head M1 and the other subhead S2 scan the tape, they are selected by the RF pulse signal. A head switching signal that changes synchronously to "1" and "0" alternately selects one main head M1 and the other sub-head S2, or the other main head M2 and one sub-head S1, and performs slow motion. In the playback state, for example, one main head M1 and the other sub-head S2 which scan odd-numbered tracks are selected in the order of one main head M1, the other sub-head S2, and one main head M1, and then the even-numbered tracks are selected. The other main head M2 and one sub-head S1 scan the other main head M2 and one sub-head S1.
1, and the other main head M2.

On the other hand, for the color switching signal of a conventional helical scan β type video tape recorder, a color switching switch is provided which switches in conjunction with switch 2 of the head switching signal generation circuit 1, and the standard contact of the switch is connected to the RF pulse input terminal. Ia, the stationary contact is grounded, and the AND signal of the non-inverted output pulse of the second bistable multivibrator 4b and the inverted pulse of the gate pulse of the first AND gate 5a is transmitted to the slow motion contact. For example, in the standard playback state, the color switching signal is
The color switching signal is alternately changed to "1" and "0" in synchronization with the selection of both main heads M1 and M2, respectively, and the color switching signal is always set to "0" during the above-mentioned static playback state.
and when in slow motion playback mode,
It is necessary to alternately change the color switching signal to "0" and "1" during the selection period of one main head M1 and the other subhead S2, and during the selection period of the other main head M2 and one subhead S1. Therefore, it is necessary to change the color changeover switch according to each reproduction state, and in this case, it is necessary to synchronize the color changeover signal and the head changeover signal.

Furthermore, when a frame advance playback function is added, for example, as shown in the head switch signal column of FIG. 4, based on the head switch signal, the other sub-head S2 , one main head M1, the other sub head S
2. After one main head M1 is selected in turn,
When the other main head M2 is selected by frame feeding, it is necessary to change the color switching signal from "0" to "1", but it is impossible to switch the color switching signal using the color switching switch mentioned above. Yes, it is necessary to separately provide a changeover switch for frame advance playback, or to provide a circuit that changes the color change signal from "0" to "1" only when the other main head M2 is selected by frame advance. There is.

That is, as new playback functions such as frame advance playback functions are added, the circuit configuration becomes more complicated.

This invention has been made with the above-mentioned points in mind, and next, this invention will be explained in detail with reference to the drawings from FIG. 3 onwards showing one embodiment of the invention.

That is, while the head switching signal HS and the RF pulse signal RS output from the switching piece x of the switch 2 of the head switching signal generating circuit 1 become "1" and "0" at the same time, the color switching signal becomes "1". Since it is only necessary to switch, a color switching signal is generated by a logic circuit that satisfies the following logical formula based on the head switching signal HS and the RF pulse signal RS. Note that , indicates an inverted signal based on the negation of the head switching signal HS and the RF pulse signal RS.

・RS+HS・ Therefore, as shown in FIG. 3, the head switching signal HS output from the switching piece The data is transmitted to the fourth AND gate 5d forming the gate, and the fifth AND gate forming the other AND gate 5d.
The RF pulse signal RS of the RF pulse input terminal Ia is further transmitted to the fourth AND gate 5d and the seventh inverter 3g.
The head switching signal HS is transmitted to the fifth AND gate 5e via the fourth AND gate 5d.
The fifth AND gate 5e calculates the logical product of the head switching signal HS and the reversed signal of the RF pulse signal RS.

Then, the outputs of the fourth AND gate 5d and the fifth AND gate 5e are transmitted to a NOR gate that calculates the logical sum of both outputs, that is, a second NOR gate 6b, and a color switching signal is formed by the output of the second NOR gate 6b. The formed color switching signal is transmitted to the color switching output terminal Ob.

Therefore, according to the embodiment, the color switching signal becomes "1" while the head switching signal HS and the RF pulse signal RS simultaneously become "1" and "0", and the color switching signal of FIG. As shown in the column, when the reproduction track is in the standard reproduction state where it changes every half period of the RF pulse signal,
A color switching signal is output that becomes "1" while the other main head M2 is playing the tape and becomes "0" while the one main head M1 is playing the tape. When the sub head S2 is in a static playback state in which it scans the same track on the tape, a color switching signal that is always "0" is output, and in a slow motion playback state in which the playback track changes every 1.5 cycles of the RF pulse signal. A color that becomes "1" while the other main head M2 and one sub-head S1 scan the tape and becomes "0" while one main head M1 and the other sub-head S2 scan the tape. A switching signal is output, and a color switching signal that becomes "1" only when the other main head M2 scans the tape during frame advance playback is output, for example, during frame advance playback. It is possible to form and output an appropriate color switching signal corresponding to each playback state using a simple logic circuit 11 without having to do this. For example, even when a frame advance playback function is added, an appropriate color switching signal can be output. With simple gate processing, an appropriate color switching signal can be formed and the color phase can be controlled regardless of the reproduction state.

As described above, this invention includes a head switching signal generation circuit that generates a head switching signal for selecting and switching each head according to various types of special playback such as standard playback, slow motion playback, still playback, and frame forwarding; RF synchronized to each head scan
The present invention provides a video tape recorder comprising a logic circuit that calculates the exclusive OR of a pulse signal and the head switching signal to form a color switching signal for color phase control.

Therefore, according to the video tape recorder of this invention, an appropriate color switching signal can be formed regardless of the playback state, especially through simple gate processing of the logic circuit, and slow motion playback, which has a slower tape speed than standard playback, can be performed. Appropriate color reproduction processing can also be performed during special reproduction such as still reproduction and frame advance.

The logic circuit also includes one AND gate that calculates the logical product of the RF pulse signal and the inverted signal of the head switching signal, and the other AND gate that calculates the logical product of the inverted signal of the RF pulse signal and the head switching signal. and a NOR gate that calculates the logical sum of the outputs of the two gates, and a color switching signal is formed by the output of the NOR gate, making it possible to form a logic circuit extremely easily.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the arrangement of the four heads, Figure 2 is
RF pulse signal waveform diagram, Figure 3 The following drawings show one embodiment of the video tape recorder of this invention, Figure 3 is a circuit block diagram, and Figure 4 shows the head switching signal of Figure 3 in each playback state. and a color switching signal. 1...Head switching signal generation circuit, 5d, 5
e...Fourth and fifth AND gates, 6b...Second NOR gate, 11...Logic circuit, Ia...RF pulse input terminal, M1, M2...Main head, S1, S2
...Sub head, Ob...Color switching output terminal.

Claims (1)

[Claims for Utility Model Registration] A pair of main heads with opposite azimuths provided in a cylinder 180 degrees apart, and a pair of main heads with opposite azimuths provided near both main heads. A video tape recorder equipped with a sub-head and capable of various special playbacks such as standard playback, slow motion playback, still playback, and frame forwarding based on selection switching of each head and control of different color phases for each track of the tape. A head switching signal generation circuit for forming a head switching signal for selecting each of the heads according to the standard playback and each special playback, and an exclusive OR of the RF pulse signal and the head switching signal. and a logic circuit for calculating negation to form a color switching signal for controlling the color phase. The logic circuit includes one AND gate that calculates the logical product of the RF pulse signal and the inverted signal of the head switching signal, and the other AND gate that calculates the logical product of the inverted signal of the RF pulse signal and the head switching signal, 2. The video tape recorder according to claim 1, further comprising a NOR gate for calculating the logical sum of the outputs of the two gates, and a color switching signal is formed by the output of the NOR gate.