JPH0151113B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a magnetic recording and reproducing device (hereinafter referred to as
This relates to the playback circuit for VTRs (abbreviated as VTR). [Prior Art] In a helical scan VTR, normal reproduction is performed using two heads with different azimuth angles. When performing special playback such as stay/intermittent slow (stay and play state repeatedly), it is possible to use two normal heads.
Since the still image quality is determined on a frame-by-frame basis, there are drawbacks such as shaking when the picture changes at high speed and a small noise tracking margin. For this reason, recently, devices equipped with one or two separate heads for special reproduction have already been put into practical use. (for example,
See "Television Technology, December 1980 issue, p. 45." ) In this case, field stay occurs (two heads with the same azimuth angle reproduce the same field track), and image quality and noise margin are improved. Figure 1 shows a conventional example with three heads, in which heads 2 and 3 have different azimuth angles from each other on cylinder 1, and head 4, which has the same azimuth angle as head 3, is located near head 2. exist. In FIG. 1, an example of the azimuth angle is shown. Recording and standard playback are performed using heads 2 and 3, and heads 3 and 4 of the same azimuth are used for field stay. Figure 2 shows a conventional example with 4 heads. The roles of heads 2 and 3 are the same as in Figure 1, but instead of head 4, heads 5 and 3 of the same azimuth are used. 6 are installed facing each other at 180°. In this case, field stabilization is performed using heads 5 and 6. FIG. 3 shows an example of a track pattern. 10
0 is tape. If the recording track of the azimuth head is 7 and the recording track of the azimuth head is 8, then the reproduction track during field stay is 9, and the portion that contributes to signal reproduction is the shaded area 1.
It becomes 0. This has a larger margin against noise compared to conventional frame staling. However, a common drawback of the above-mentioned conventional examples is that only heads 2 and 3 are used for recording, and like current home VTRs (for example, VHS), 2-hour mode (track pitch 60 μm), 6-hour mode (track pitch 60 μm),
If there are time modes (track pitch 20 μm), it is not possible to select the optimum head track width for each mode. In other words, since the track pitch for 6 hours is 20 μm, the track width of the head is determined by the restriction of adjacent interference.
It cannot be made more than 40 μm. Therefore,
In the 2-hour mode, a guard band in which no signal is recorded occurs, and although field stay is possible, intermittent feed slow is impossible. Also, so-called picture search, which performs high-speed playback, has a guard band in the 2-hour mode, so the noise range is large and is not practical. [Object of the Invention] An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a means that can realize field stay and intermittent feed slow in both the 2-hour mode and the 6-hour mode. [Summary of the Invention] In order to achieve the above object, the present invention includes two 2-hour dedicated heads, two 6-hour dedicated heads, and one special playback head, and a field stay.
When realizing intermittent feed slow mode, one feature of the 6-hour dedicated head and one special playback head are used in both the 2-hour and 6-hour modes. [Examples of the Invention] The present invention will be described in detail below based on specific examples. FIG. 4 shows an embodiment of the present invention, in which two-hour dedicated heads 11 and 12 and a six-hour dedicated head 1 are shown.
3, 14, and a special reproduction head 15. Heads 11 and 12 have different azimuths and face each other at approximately 180°, and heads 13 and 14 also have different azimuths and face each other at approximately 180°. The positional relationship between the heads 11 and 13 is arbitrary. Heads 12, 14, and 15 have the same azimuth. An example of the azimuth angle is shown in the figure. In the case of VHS/VTR, an example of an appropriate head track width for 2-hour mode and 6-hour mode is: Heads 11, 12: Tw = 70 μm Heads 13, 14, 15: Tw = 30 μm, and 2-hour mode Recording and standard playback are performed using heads 11 and 12, and 6-hour mode recording,
Standard reproduction is performed by heads 13 and 14. Head 15 is placed near head 13, and head 13
The distance between the magnetic gap of the head 15 and the magnetic gap of the head 15 is usually 1l ^H to 3l ^H (l ^H is the length equivalent to one horizontal period on the cylinder circumference, and in the case of VHS, it is about 370 μm)
selected. The key point of the present invention is that when realizing field stay/intermittent slow playback, the head 14 has the same azimuth in both the 2-hour mode and the 6-hour mode.
The point is that a head 15 is used. FIGS. 5 and 6 show track patterns during field stay playback. In the 6-hour mode shown in FIG. 5, if the recording track of head 13 is 13W and the recording track of head 14 is 14W, the reproduction track of head 14 and head 15 is 16 during field stay, and the shaded area 17 contributes to the signal. do. In the 2-hour mode shown in FIG. 6, if the recording track of head 11 is 11W and the recording track of head 12 is 12W, the reproduction track of heads 14 and 15 is 18 during field stay, and the shaded area 19 contributes to the signal. . That is, field stay can be achieved by the heads 14 and 15 in the same way in both the 2-hour mode and the 6-hour mode. When performing intermittent feed slow, noiseless playback is possible by using heads 14 and 15 in the stall state, and by using heads 13 and 14 in a transitional play state from one stall to the next. FIG. 7 shows an example of the channel arrangement of the rotary transformer 20 in the 5-head system of the present invention. From the outside, channel 21: connection channel to 6hr azimuth head 13; channel 22: connection channel to 6hr azimuth head 14; channel 23: intermittent feed slow The azimuth head 15 and the connection channel 24 are connected to the 2-hour azimuth head 12, and the connection channel 25 is connected to the 2-hour azimuth head 11. Important factors in determining this placement are crosstalk and adjacent channel
This is a level drop due to short. Among the five heads mentioned above, it is difficult to make good contact with the tape and there is a concern that the output will drop because of the close proximity of head 1.
3. The head 15, and especially the head 13, which is used for 6-hour standard playback, becomes a problem if its output decreases. Further, crosstalk becomes a problem between heads 13 and 15, which are adjacent to each other, and between heads 11 and 12 for 2 hours and heads 13 and 14 for 6 hours.
Therefore, these channels must not be adjacent, or one head must be shot. Each mode will be described in detail below. (1) 2hr standard playback using channels 24 and 25, channel 2
1, 22, and 23 are shot. 2hr playback does not cause any problems as the output is sufficiently large. (2) 6hr standard playback using channels 21 and 22, channel 2
4,25 is shot. At this time, the head 15 reproduces the signal, and crosstalk with the adjacent head 13 becomes a problem, so the channel 22 of the head 14 is inserted between the channel 23 of the head 15 and the channel 21 of the head 13 to prevent crosstalk. . (3) 2hr, 6hr special playback Channels 21, 22, and 23 are used, and channels 24 and 25 are shot. Crosstalk between adjacent heads 13 and 15 is not a problem since channels 21 and 23 are separated. channel 2
4 is shot, the efficiency of the channel 23 decreases and the output of the head 15 decreases, but
The head 15 is used exclusively for special playback (stay/intermittent feed slow) and does not pose any practical problems. Note that the same effect can be obtained even if the channel arrangement shown in FIG. 7 is symmetrically exchanged between the inner and outer channels. Figure 8 shows the head changeover switch circuit.
6, one is on and the other is short. Similarly, the outputs of the 2-hour head 12 and rotary transchannel 24, and the outputs of the 6-hour head 14 and rotary transchannel 22 are switched by a changeover switch 27, one being on and the other being shorted. Also, transistor switches 28, 29, 30, 31, 32, 3
3 exists. The operation of this transistor switch will be explained below. (1) During recording The switch 33 may be off, the switches 28 and 29 may be on, and the switches 30, 31, and 32 may be either on or off. Switch 2 to switch between 2hr and 6hr
6, 27. In the example shown in FIG. 8, the output current of the recording amplifier 34 passes through the head 13 and the switch 28 to GND, and also to the head 14 and the switch 28.
Flows to GND through switch 29. At this time, since a large amplitude is generated at the collector of the switch 33, the switch 33 may be turned on. To prevent this, transistors 35 and 36 are provided. a is a signal that is High at Rec (same as the power supply voltage) and low at PB, b is High at PB,
Connect the signal c, which is low during Rec, to the power supply. In this case, during recording, both transistors 35 and 36 are turned off, and the base of transistor switch 33 is kept open, and there is no path for the base current to flow, so even if a large amplitude signal comes, switch 3
3 does not turn on. (2) During standard reproduction (play) First, transistors 35 and 36 are turned on, and switch 33 is also turned on. Switches 28 and 29 are off, switch 31 is on, and switch 32 is off. The DC base current of the switch 31 flows to ground via the rotary transformer and the switch 33. The switch 30 is turned on during 2-hour playback to prevent crosstalk from channel 23 to channel 24, and the switch 30 is turned on during 6-hour playback because the head 14 that connects to the adjacent channel is located approximately 180 degrees from the head 15, so crosstalk is not a problem. 30 is off. In the example of FIG. 8, the output of the head 13 is sent to the preamplifier 37,
The output of head 14 is applied to preamplifier 38.
Switching between 2hr and 6hr regeneration is performed by switches 26 and 27. (3) During special playback During field stay for both 2hr playback and 6hr playback, switch 31 is turned off, switch 32 is turned on, and playback is performed using heads 14 and 15 of the same azimuth. During the intermittent feed slow, in a transitional play state between one stall and the next stall, the switch 31 is turned on and the switch 32 is turned off. This enables noiseless field stay and intermittent feed slow for both 2hr and 6hr playback. In the above embodiment, field stay is performed using two azimuth heads, but in FIG. (Head 1
3, 15), it is also possible to perform field stay. [Effects of the Invention] As described above, according to the present invention, optimum recording and playback in 2-hour mode, optimum recording and playback in 6-hour mode, and field stay/intermittent feed slow playback in 2-hour mode and 6-hour mode can be performed to the minimum necessary. This can be done with a limited number of heads. 2 hour mode,
Even when performing search playback in 6-hour mode (for example, 10x forward/reverse speed), by using a head with a track width wider than the track pitch in each mode, playback with fewer noise bands is possible. But the effect is great. The above-mentioned 2-hour mode and 6-hour mode are added for convenience, and the present invention can be similarly applied to cases where there are two modes or three or more modes with different track pitches.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional example in the case of 3 heads, FIG. 2 is an explanatory diagram of the conventional example in the case of 4 heads, FIG. 3 is an explanatory diagram showing an example of a track pattern for field stay reproduction, and FIG. 5 is an explanatory diagram showing a head arrangement according to an embodiment of the present invention, FIG. 5 is an explanatory diagram of a track pattern for field stay reproduction in a 6-hour mode, and FIG. 6 is an explanatory diagram of a track pattern for field stay reproduction in a 2-hour mode. , FIG. 7 is a plan view showing an example of the channel arrangement of the rotary transformer in the present invention, and FIG. 8 is a circuit showing an example of a circuit for realizing recording/reproduction switching, 2hr/6hr switching, and standard/special reproduction switching in the present invention. It is a diagram. 1... Cylinder, 11, 12... Head for 2 hours only, 13, 14... Head for 6 hours only, 15...
...Head for special playback.

Claims (1)

[Claims] 1. The first one has a different azimuth angle, is spaced approximately 180 degrees apart, and is used when recording in standard mode.
and a second head having a narrower head track width than the first and second heads, having different azimuth angles, and spaced approximately 180 degrees apart, the tape running speed being in the standard mode. The third mode is used when recording in long-term mode, which is slower than when
and a fifth head which is arranged near the third head and has the same azimuth angle as that of the fourth head. The recording signal is supplied to the second head, and during long-time mode recording, the recording signal is supplied to the third and fourth heads, and the recording signal is supplied to the tape track formed during recording in each mode. A magnetic recording/reproducing apparatus comprising: head selection means for supplying reproduction signals from the fourth and fifth heads to a preamplifier during still reproduction by stopping tape running to obtain a reproduction signal. .