JPH028461Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention uses a pair of main heads and a pair of subheads of a rotating cylinder to produce a slow mode tape running speed that is 1/3 that of standard playback. The present invention relates to a helical scan video tape recorder that performs digital playback.

[Conventional technology]

Traditionally, helical scan type video tape recorders, which have standard playback functions and special playback functions such as still playback and slow motion playback, have rotating cylinders with mutually opposite azimuths in order to improve the S/N ratio during slow motion playback. On the other hand, the other main head is provided 180 degrees opposite to the other main head, and one sub-head having the same azimuth as the other main head is placed in the vicinity of one main head, that is, one horizontal section length of the reproduced image from one main head. At the same time, the other sub-head, which has the same azimuth as one main head, is placed near the other main head, that is, separated from the other main head by an integer multiple of the length of one horizontal section of the reproduced image. It is formed in a certain position.

At this time, as shown in FIG.
The head widths Wsa of the respective heads 2a are formed to be the same 27 μm.

Note that the arrow in FIG. 1 indicates the running direction of the tape.

During standard playback, both main heads M1 and M2
Each track on the tape is alternately scanned and played back, and during static playback, the same track on the tape is alternately scanned and played back by the main head and subheads of the same azimuth, for example, main head M1 and subhead S2a. do.

Also, during slow motion playback, the tape running speed is 1/3 that of standard playback, and the amount of tape movement is reduced to 1/3. S1a, the main head M2, the sub-head S1a, and the main head M2 are repeatedly scanned and reproduced three times in this order, and each even-numbered track following each odd-numbered track is transferred to the main head M
1 and the sub head S2a, the main head M1, the sub head S2a, and the main head M1 are repeatedly scanned three times in the order of reproduction.

Next, each head M during slow motion playback
1, M2, S1a, S2a head reproduction output,
An embodiment of the present invention will be explained with reference to FIG. 2.

Figure 2 is an envelope analysis diagram with the vertical and horizontal axes representing the amount of tape movement and time, and each section is surrounded by a straight line at the time interval of one field f and a diagonal line at the interval of the tape width tw. indicates each track on the tape, and during standard playback, by alternately scanning heads M1 and M2, as shown by the dashed arrow, the first field f tracks track number 1, and the next field f tracks track number 2. Truck,..., 8
In the th field f, the reproduction proceeds in the order of track number 8, . . . .

During slow motion playback, each head M1, M2, S1a, and S2a is connected to one of the two heads in FIG.
Scan and reproduce the range surrounded by dotted lines a and a',
At this time, by switching the head for each field f, for example, as shown by diagonal lines, the track with track number 2 is transferred to the main head M in the first three fields f.
2. The sub head S1a performs three repeated scans in the order of the main head M2, the sub head S1a, and the main head M2, and the track number 3 is reproduced in the next three fields f, the main head M1 and the sub head S.
2a, the main head M1, the sub-head S2a, and the main head M1 are repeatedly scanned three times in this order,
In the next three fields f, the track with track number 4 is reproduced by the main head M2 and the sub head S1a by scanning the main head M2, the sub head S1a, and the main head M2 repeatedly three times, and the same operation is repeated thereafter. It will be returned.

In FIG. 2, the head reproduction output with the same azimuth as the scanned track is indicated by diagonal lines in the direction corresponding to the azimuth, and the size and shape of each diagonal line determines the head reproduction output obtained during slow motion reproduction. Seek.

[The problem that the idea attempts to solve]

By the way, in the case of the conventional video tape recorder, main heads M1, M2 and sub heads S1a,
Since the head width of S2a is the same, each head M
1, M2, S1a, and S2a are arranged in a cylinder so that their centers are on the same line, so-called center alignment, and during slow motion playback, each head M1, M2, S1a, and S2a is in an almost on-track state as shown in Fig. 2. Even if the head is scanned in this manner, the reproduction output of the head during slow motion reproduction drops significantly at the head switching point between the main and sub heads, as shown in FIG. 3a.

That is, as shown in FIG. 3a, the main head M
From the scan number 3 of each 3-times repeated scan to the switching point xa where the head output of No. 2 switches to the head output of the main head M1, etc., to 1 of the next 3-times repeated scan.
Compared to the switching point of the head reproduction output between the main heads when switching to the second scan, the switching point xb where the main head M2 switches to the sub head S1a, and the switching point
Switching point xc from 1a to main head M2,
The switching point xd at which the main head M1 switches to the subhead S2a, the switching point xe at which the subhead S2a switches to the main head M1, etc., from the first scan to the second scan, and from the second scan to the third scan.
At the switching point of the head reproduction output between the main and sub-heads at the time of the second scan, the reproduction outputs of the first and third main heads decrease.

Furthermore, there is a problem in that the S/N ratio during slow motion reproduction decreases due to fluctuations in the decrease in the head reproduction output.

In addition, the reproduction output (envelope output) of both main heads M1 and M2 is increased, and each switching point xa~
In order to increase the main head reproduction output in xe, if the head width of both main heads M1 and M2 is increased,
Both main heads M1, M with respect to the track width of the tape
The head width of 2 becomes too large and the S/N during standard playback decreases.
This may cause problems such as deterioration of both main heads M.
1. The head width of M2 cannot be increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a helical scan video tape recorder that prevents S/N deterioration during standard playback and improves S/N during slow motion playback.

[Means to solve the problem]

In order to achieve the above object, the video tape recorder of the present invention includes a pair of main heads having opposite azimuths at opposite positions of a rotating cylinder, and a pair of main heads opposite to each other in the vicinity of the two main heads. During slow motion playback with a pair of azimuth sub-heads and the tape running speed reduced to 1/3 of standard playback, one azimuth main and sub-head scans repeatedly three times, and the other azimuth main and sub-head scans repeatedly three times. In a helical scan video tape recorder that reproduces the tape by alternately performing three repeated scans by the sub-heads, the head width of both the sub-heads is formed to be larger than the head width of both the main heads, and The main heads are arranged so that the centers of both main heads and the centers of the two width heads are located on the same line, and an RF pulse signal that is inverted at the switching timing of the head scan every half rotation of the cylinder and the playback control signal of the tape are connected. gate pulse forming means for forming a gate pulse that becomes logic 1 only during a predetermined head scanning period of either one of the two three-time repetitive scans by means of an original gate process; and a column operated by the RF pulse signal and the gate pulse. A head switching signal for reproduction output selection which gate-processes the output signals of two connected bistable multivibrators and the RF pulse signal, and becomes logic 0 only during the second scanning period of each of the three repeated scans. a switching signal forming means for forming a sub-head reproducing output with a logic 1 of said head switching signal, a main head reproducing output with a logic 0 of said head switching signal, and a sub-head reproducing output with a logic 0 of said head switching signal; The apparatus includes output selection switch means for sequentially outputting a head reproduction output, a main head reproduction output, and a sub-head reproduction output.

[Effect]

In the video tape recorder of the present invention configured as described above, during slow motion playback,
Conventional main head, sub-head, main head (3 each)
Instead of repeated scanning, the tape is played back by repeatedly scanning the subhead, main head, and subhead three times each in the order of three times, and at this time, the centers of both main heads and both subheads are located on the same line. Then, each head is arranged in a cylinder with so-called center alignment,
In addition, the first and third scans of each of the 8-time repeated scans are performed with the sub-head with the largest head width, and the head reproduction outputs of each of the 3-time repeated scans are selected in the order of increasing sub-head reproduction output. The effective playback area of 3 times repeated scanning is the largest, and the sub head playback output of the 1st and 3rd scans of each 3 times repeated scan does not decrease, so a drop in the head playback output is prevented and the S/N improves. .

Furthermore, since the head widths of both main heads are not made large, no deterioration of the S/N ratio occurs during standard playback.

〔Example〕

One embodiment will be described below with reference to FIG. 2 and the following drawings.

First, as shown in FIG. 4, both main heads M1,
With respect to the head width Wm of M2, which is 27 μm, the head width Wsb of both subheads S1b and S2b is increased to 33 μm, and the center mc of both main heads M1 and M2 and the center sc of both subheads S1b and S2b are on the same center line.
Each head M1, M2,
S1a and S2b are placed in the cylinder with their centers aligned.

Note that the subhead S1b is the subhead S1 in FIG.
The subhead S2b corresponds to the subhead S2a in FIG.

That is, the center of the tape is located at both main heads M1 and M.
Both main heads M1, M2 pass through the center mc of 2 and the center sc of both sub heads S1b,
and both sub-heads S2b, S2b are arranged.

On the other hand, as shown in Fig. 5, it is reversed at the switching timing of the head scan every half rotation of the cylinder.
The RF pulse signal is sent to the head switching signal generation circuit 1.
The signal is input to the RF pulse input terminal Ia and the stationary contact pa of the reproduction state changeover switch 2, and the tape reproduction control signal is input to the control pulse input terminal Ib of the creation circuit 1.

The switch 2 has a stationary contact pa, a grounded standard contact PB, and a slow motion contact PC, and the switching valve x switches to the contacts PB, PA, and PC respectively by standard regeneration, static regeneration, and slow motion regeneration. Change.

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

Also, the playback control signal of input terminal Ib is
First and second monostable multivibrators 6a, 6b
and is input to the first AND gate 5a via the third inverter 3c.

The tape running speed is 1/3 that of standard playback.
During slow motion playback, the RF pulse signal changes to logic 1 and 0 at 30Hz in synchronization with the head scan, as in standard playback, based on the cylinder's constant rotation of 30 revolutions/second (= 2 fields/second). (Hereinafter, logic 1 and 0 will be referred to as "1" and "0", respectively.) For example, as shown in FIG.
It becomes "0" during the scanning period.

Also, based on the decrease in the running speed of the tape, the playback control signal changes from "1" to "0" at the scanning start end of the main head M1, as shown in FIG. 6b, for example.
and changes at 10Hz.

Then, in order to perform slow motion reproduction by repeating three scans with each of the main heads M1 and M2 as the second scan, the production circuit 1 operates as described below.

First, the first and second monostable multivibrators 6
A, 6b, third inverter 3c, and first AND gate 5a form gate pulse forming means, for example, bistable multivibrators 6a, 6 based on the rise of the reproduction control signal in FIG. 6b.
b is operated to form a timing pulse for extracting the RF pulse signal, and based on the RF pulse signal passed through the second inverter 3b and the timing pulse passed through the third inverter 3c, the first AND gate 5a 1. To the second bistable multivibrators 4a and 4b, for example, a gate pulse that always becomes "1" during the scanning period of the subhead SIb following the main head M2 is outputted.

That is, the gate pulse forming means includes three pulses in the order of subhead S2b, main head M1, and subhead S2b.
As a gate pulse that becomes "1" only during a predetermined head scanning period of either one of the main head M2
A gate pulse that becomes "1" is formed and output during the next scanning period of the sub-head S1b.

Then, with the rise of the gate pulse of the first AND gate 5a, the first and second bistable multivibrators 4a and 4b, which have reset priority, are reset, and at this time, both bistable multivibrators 4
The non-inverting output terminals Q of a and 4b become "1".

Further, 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 output signal of the non-inverting output terminal Q of the first bistable multivibrator 4a. Triggered on the rising edge of

Therefore, the first bistable multivibrator 4a
The output signals of the non-inverting output terminal Q and the inverting output terminal of the second bistable multivibrator 4b change as shown in FIG. It changes as shown in Figures f and g, respectively.

That is, the cascade-connected first and second bistable multivibrators 4a and 4b are connected to the first bistable multivibrator based on the RF pulse signal and the gate pulse signal of the first AND gate 5a via the second inverter 3b. The output signal of the non-inverting output terminal Q of 4a becomes a non-inverting pulse of "0" only during the scanning period of the main head M1 and the sub-head S2b in that order.
The output signal of the non-inverting output terminal Q of the second bistable multivibrator 4b becomes a non-inverting pulse of "0" only during the scanning period of the sub head S1b and the main head M2 in that order.

Then, the RF pulse signal via the second inverter 3b, the output signal of the inverting output terminal of the first bistable multivibrator 4a, and the output signal of the non-inverting output terminal Q of the second bistable multivibrator 4b are connected to the second AND gate 5b. The RF pulse signal via the first inverter 3a, the output signal of the non-inverting output terminal Q of the first bistable multivibrator 4a, and the output signal of the inverting output terminal of the second bistable multivibrator 4b are input to the third AND. The signal is input to gate 5c.

Therefore, a pulse that becomes "1" is output from the second AND gate 5b to the NOR gate 6 only during the scanning period of the main head M1, as shown in FIG. i
As shown in Figure J, a pulse that becomes "1" is output only during the scanning period of the main head M2, and the pulse that becomes "1" is output from the NOR gate 6 to the slow motion contact Pc of the switch 2, as shown in Figure J, during the scanning period of the main heads M1 and M2. A head switching signal that becomes "0" is output only when

That is, the first and second bistable multivibrators 4a, 4b, the second and third AND gates 5b, 5
c. The switching signal forming means formed by the NOR gate 6 operates with the RF pulse signal and the gate pulse of the first AND gate 5a, and only during the scanning period of the second main head M1 or M2 in each three-times repeated scan. A head switching signal for reproduction output selection which becomes "0" is formed.

Furthermore, the output signal of the non-inverting output terminal Q of the second bistable multivibrator 4b and the output signal of the fourth inverter 3d
The gate pulse of the first AND gate 5a is input to the fourth AND gate 5d, and the output signal of the fourth AND gate 5d is 3 as shown in FIG.
It changes every time the tape is scanned repeatedly, that is, every time the tape moves one track and the playback track changes.

The output signal of the fourth AND gate 5d is then output to the slow motion contact pc' of the color changeover switch 7, which is switched in conjunction with the switch 2.

In addition, in the switch 7, the stationary contact pa' is grounded, the standard regeneration contact Pb' is connected to the RF pulse input terminal Ia, and the switching piece x' is connected to the contact pb during standard regeneration, static regeneration, and slow motion regeneration. ′、pa′、
pc′ respectively.

On the other hand, the head reproduction outputs of the main heads M1 and M2 are transmitted via first and second preamplifiers 8a and 8b to first and second switch circuits 9a and 9 for selecting reproduction outputs.
The head reproduction outputs of the sub-heads S1b and S2b are input to third and fourth switch circuits 9c and 9d for reproduction output selection via third and fourth preamplifiers 8c and 8d, respectively.

The third and fourth switch circuits 9c and 9d output the output signal "1" and "0" of the switching piece x of the switch 2, respectively.
The first and second switch circuits 9a and 9b are turned on and off when the output signal of the fifth inverter 3e, which is an inversion of the output signal of the switching piece x of the switch 2, is "1" and "0". Turn off.

Therefore, during standard playback, the fifth inverter 3e
The output signal of the main head M1 and M2 is held at "1", the first and second switch circuits 9a and 9b are held on, the third and fourth switch circuits 9c and 9d are held off, and the main heads M1 and M2 are turned off. Only the playback output is selected, and the head playback outputs of the main heads M1 and M2 are inputted to the fifth and sixth switch circuits 9e and 9f via the first and second video amplifiers 10a and 10b, respectively.

At this time, the sixth switch circuit 9f turns on and off in response to "0" and "1" of the RF pulse signal, and the fifth switch circuit 9f turns on and off the output signal of the sixth inverter 3f which inverts the RF pulse signal. It is turned on and off when it is set to "1", and both switch circuits 9e and 9f are turned on only during the scanning period of the main heads M1 and M2, respectively, and the head playback outputs of the main heads M1 and M2 are combined and the third video amplifier 10c is turned on. and the composite output of the video amplifier 10c is input to the seventh switch circuit 9.
It is output from the playback output terminal O via g.

Note that the seventh switch circuit 9g is a fifth inverter 3 which inverts the output signal of the switching piece x of the switch 2.
It is turned on and off by "1" and "0" of the output signal of e.

Furthermore, during static playback based on the scanning of the main head M2 and the sub head S1b, the output signal of the switching piece x of the switch 2 becomes an RF pulse signal, and the main head M2
During the scanning period, the first and second switch circuits 9a and 9b
Then, the fifth and seventh switch circuits 5e and 5g are turned on, and the third and fourth switch circuits 9c and 9d and the sixth switch circuit 5f are turned on during the scanning period of the sub head S2b, and the head reproduction output of the main head M2 is turned on. Second switch circuit 9b, second video amplifier 10b, fifth
The head reproduction output of the sub head S1b is output to the reproduction output terminal O via the switch circuit 9e, the third video amplifier 10c, and the seventh switch circuit 9g.
switch circuit 9c, first video amplifier 10a, sixth switch circuit 9f, third video amplifier 10c,
The signal is output to the reproduction output terminal O via the one horizontal period delay circuit 11 for time adjustment.

Next, during slow motion reproduction, the output signal of the switching piece x of switch 2 becomes the head switching signal shown in FIG. The third and fourth switch circuits 9c and 9d are turned on, and the first and second switch circuits 9a and 9b and the seventh switch circuit 9g are turned on during the scanning period of the second main head M2 or M1.

Further, during the scanning period of the main head M1 and the sub-head S1b, the fifth switch 9e is turned on, and the main head M1 and the sub-head S1b are scanned.
2. The sixth switch 9f is turned on during the scanning period of the subhead S2b.

Therefore, while the main head M1 and the sub-head S2b repeatedly scan odd or even tracks three times, the head reproduction output of the sub-head S2b, the head reproduction output of the main head M1, and the head reproduction output of the sub-head S2b are selected. During the repeated scanning of the next track three times by the main head M2 and the sub head S1b, the sub head S
The head reproduction output of head 1b, the head reproduction output of main head M2, and the head reproduction output of subhead S1b are selected in order and outputted to reproduction output terminal O.

That is, the first to fourth switch circuits 9a to
During slow motion playback, the output selection switch means formed by 9d selects the subhead playback output of the subhead S1b or S2b, the main head playback output of the main head M2 or M1, and the subhead playback output of the subhead S1b or S2b for each three repeated scans. The sub head reproduction outputs of S2b are selected and output in order.

Then, the main heads M1, M2 and the sub head S1
b and S2b are arranged in the cylinder in a centered manner, and the head width of the sub heads S1b and S2b is larger than that of the main heads M1 and M2. Therefore, during slow motion playback, each head M1 and M
2, S1b, and S2b travel in the on-track state within the range indicated by two-dot broken lines b and b' in FIG. Accordingly,
Sub head S2b, main head M1, sub head S2b
The next track with track number 6 is played back three times in the order of
2, the track is reproduced three times in the order of subhead S1b, main head M2, and subhead S1b, and the next track with track number 7 is played back on subhead S2b.
and main head M1, the sub head S2b, the main head M1, and the sub head S2b are repeatedly reproduced three times in the order of The effective reproduction area of the three-time repeated scan is the largest, and the first and third scans of each three-time repetitive scan are performed in the sub-head S1b or S2b, which has a wide head width. Then, the head reproduction outputs for each three repeated scans are selected in the order of increasing sub-head reproduction outputs.

Therefore, from the first to the second scan of each three-time repetition
The secondary head reproduction output corresponding to the conventional main head reproduction output at the switching point from the second head to the third head does not decrease, and the combined head reproduction output remains the same as shown in Figure 3b. Head switching points corresponding to conventional head switching points xb to xe in figure a
The decreases in xb′, xc′, xd′, and xe′ become extremely small.

Therefore, during slow motion reproduction, the head reproduction output for each three repeated scans is performed with the best scan and output selection, preventing a drop in the head reproduction output and improving the S/N.

Since the head widths of the main heads M1 and M2 are not widened, no deterioration in S/N occurs during standard playback.

In addition, the main heads M1, M2 and the sub head S1
Of course, the S/N will not improve even if S2b is arranged so that its lower end coincides with the reference line Lo or its upper end coincides with it.

Furthermore, the gate pulse of the first AND gate 5a may be output during a predetermined head scanning period different from that in the embodiment. In this case, the switching signal forming means etc. It is sufficient to change the structure of the head switching signal and generate a head switching signal that becomes "0" during the second scanning period of each three-times repeated scanning.

Furthermore, main heads M1, M2, sub head S1
The head widths of b and S2b are 27 μm and 33 μm in the example.
It may be other than each.

[Effect of idea]

Since the present invention is configured as described above, it produces the effects described below.

During slow motion playback, the tape is played back by repeatedly scanning the subhead, main head, and subhead three times each, instead of the conventional method of repeatedly scanning the main head, subhead, and main head three times each. When,
Each head is arranged in a cylinder in a so-called centered manner so that the centers of both main heads and both sub-heads are located on the same line, and the first and third scans of each of the three repeated scans are performed so that the centers of both main heads and both sub-heads are located on the same line. By selecting the head playback output for each three-time repeated scan in the order of increasing sub-head playback output by using a wide head, the effective playback area for each three-time repeat scan is maximized, and each three-time repeat playback is maximized. It is possible to prevent a decrease in the reproduction output of the sub-heads in the first and third scans, and since the head widths of both main heads are not increased, there is no S/N deterioration during standard reproduction. S/N during standard playback
It is possible to improve the S/N ratio during slow motion playback by preventing deterioration of the recording speed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the arrangement of the main head and sub-head of a conventional video tape recorder. FIG. 2 and the following drawings show an embodiment of the video tape recorder of this invention. Figure a,
Each b is an explanatory diagram of the head reproduction output based on Fig. 2, Fig. 4 is an explanatory diagram of the arrangement of the main head and sub-head, Fig. 5 is a circuit block diagram, and Figs. 6 a to k are explanatory diagrams of the operation of Fig. 5. This is a timing chart for. M1, M2...Main head, S1b, S2b...Sub head, Lc...Center line, 1...Head switching signal generation circuit, 4a, 4b...Bistable multivibrator, 6
a, 6b...monostable multivibrator, 8a-8
d...Preamplifier, 9a-9g...Switch circuit, 1
0a to 10c...video amplifier, 11...1 horizontal period delay circuit.

Claims (1)

[Claims for Utility Model Registration] A pair of main heads with opposite azimuths are provided at opposite positions of a rotating cylinder, and a pair of subheads with opposite azimuths are provided near each of the main heads. During slow motion playback with the tape running speed reduced to 1/3 of standard playback, the main and sub heads of one azimuth perform three repeated scans, and the main and sub heads of the other azimuth perform three repeated scans. In a helical scan video tape recorder that reproduces the tape by alternately performing The sub-heads are arranged so that their centers are on the same line, and gate processing is performed based on the RF pulse signal, which is inverted at the switching timing of the head scan every half rotation of the cylinder, and the tape playback control signal, so that both of the three times are performed. gate pulse forming means for forming a gate pulse that becomes logic 1 only during a predetermined head scanning period of one of the repetitive scans; and two bistable multi-channel devices connected in cascade that operate using the RF pulse signal and the gate pulse. switching signal forming means for gate-processing the output signal of the vibrator and the RF pulse signal to form a head switching signal for reproduction output selection that becomes logic 0 only during the second scanning period of each of the three repeated scannings; , the logic 1 of the head switching signal selects the sub-head reproduction output, the logic 0 of the head switching signal selects the main head reproduction output, and the sub-head reproduction output and the main head reproduction output are selected for each of the three repeated scans. , and output selection switch means for sequentially outputting sub-head playback outputs.