JPS6124384A - Skew distortion correcting device of video tape recorder - Google Patents

Abstract

PURPOSE:To correct the entire skew distortion at the time of the special reproduction by a single skew distortion correcting circuit by fitting a special reproducing head in the position where 1/2H skew jump arises even at the special reproduction having no getting over of a track. CONSTITUTION:Recording/reproducing heads A and B are fitted to a rotating body 1 under 180 deg. position relation, while special reproducing heads C and D are fitted at an angle corresponding to 1/4H in the rotating direction of the rotating body with respect to 180 deg., that is, the position advanced by a quarter of about 360 deg./262.5. By fitting the heads C and D under said position relation, an 1/2H skew distortion correcting circuit can be used at the time of the special reproduction of all magnetic tape recording patterns. When the special reproduction is executed by a magnetic tape recorded at a recording mode, the 3rd switch circuit 18 is switched by a signal supplied to a terminal 21 so that a signal at the side of an input terminal 18a can be outputted. Thus a signal for appearing at an output terminal 19 has no skew distortion.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention solves the problem of occurrence of skew distortion in a video tape recorder (hereinafter referred to as VTR) during so-called special playback, in which playback is performed at a tape speed different from that during recording. This is related to the V17R's Schiko distortion correction component "l" that eliminates the distortion.

[Technical application of the invention and its problems] In a home VTR, video signals are sequentially recorded diagonally in the longitudinal direction of a magnetic tape using two heads with different azimuth angles. . J.

That is, as shown in FIG. 3, heads A and B with different azimuth angles are attached to a rotating body 31 at an interval of 180°, and as shown in FIG. C
The video signal for one field is recorded as track A1, and the signal for the next field period is recorded by head B.
It is recorded as one track. After that, repeat the process to move to tracks A2 and B2.

A3, B3, . . . are recorded sequentially.

Furthermore, home VTRs are set so that the tape speed during recording can be reduced to 172 to 1/3 of that of the standard mode. In some cases, the positions of the horizontal synchronizing signals of the video signals are not aligned. For example, as shown in Figure 4, the positions of the horizontal synchronizing signals between adjacent tracks are 0.758.
(H is the horizontal period) [It may deviate.

When a magnetic tape recorded in this manner is run at a high speed and a video signal is reproduced using one head AXB shown in FIG. 3, each head makes one race across a plurality of tracks. At this time, since the azimuth recording method is used, for example, head A plays track A1 and then tracks B.
Although the 11-rack is traced, no output is generated there, and the reproduced output is obtained again in the next A21-rack. Therefore, at the track change point, the position of the horizontal synchronization signal shifts by 0.5H, which causes skew distortion.

Conventionally, in order to correct such skew distortion, when a skew jump occurs, this is detected and 1/2)
The skew distortion is corrected by switching to output a signal delayed by 1 or a signal advanced by 1/2 day.

That is, as shown in FIG.
3 and directly to the other input terminal. Furthermore, a skew jump of the signal applied to the input terminal is detected by the 1/2 +-1 skew detection circuit 54, the bistable multi-by break 55 is triggered, and the switch circuit 53 is switched by the output of the multi-by break 55. The 1/2H skew detection circuit is
For example, a horizontal sync signal separated from the input signal triggers a flywheel oscillator with an oscillation frequency of 2f1 to synchronize its oscillation operation to the horizontal sync signal. Then, a signal with a predetermined pulse width obtained by dividing the output of the oscillator in half is ANDed with the horizontal synchronizing signal. When a skew jump occurs, the AND output is 0.
Since the signal changes from 1 to 0, or from 1 to O, the bistable multi-by-break is inverted by that signal and the switch is changed. As a result, a signal without skew distortion is supplied to the output terminal 56 of the switch circuit.

In addition to such high-speed playback, home VTRs are also set to allow special playback such as double-speed playback, slow playback, and still playback.

In such special playback, by appropriately controlling the head trace position relative to the tape, it is possible to control the head trace so that it is performed on approximately one track rather than across multiple tracks. I can do it.

Therefore, as shown in FIG. 3, in addition to beds A and B, heads C and D having the same azimuth angle (for example, the same azimuth angle as head B) are attached to a rotating body. Tracks 81, 82 and 83 can be controlled to be traced.

In this type of special playback, the head does not cross over the track, so 1/2H skew jump does not occur, but since the head traces one track diagonally, the number of playback horizontal synchronization signals increases. It increases or decreases compared to when recording, and a 1/4H skew jump occurs at the head switching point.

Conventionally, such 1/4H skew jumps are corrected by the horizontal synchronization AFC circuit on the television receiver side to the extent that they are almost invisible on the screen, so there is no need to make any special corrections on the VTR side. If the time constant of the horizontal synchronization AFC circuit on the television receiver side is long, this skew distortion may be noticeable on the screen.

Therefore, it is preferable to provide a 1/4H skew distortion correction circuit in the VTR, but by providing a 1/4H skew distortion correction circuit in addition to the 1/2H skew distortion correction circuit, the circuit configuration becomes complicated. , I didn't like it.

"Purpose of the Invention" This invention has the ability to
By placing the special playback head at a position where a skew jump of /2 +-4 occurs (=J I), all the skew distortion during special playback can be reduced to a single jump of 1.
-Can be corrected with a distortion correction circuit/e V
The purpose is to provide a special reproduction device for TR.

[Summary of the Invention 1 This invention provides a rotating body with two parts having the same azimuth angle for special regeneration.
When installing two heads, one head can be installed with an angle equivalent to 1/4H in the rotational direction relative to 180°, so that even during special playback where the track does not cross over using this head, it is possible to The above objective is achieved by causing a /2H skew jump or by using a 1/4H delay line.

[Embodiment of the Invention] According to an embodiment of the present invention, as shown in FIG. , special playback head C
, D is 180°, 1 / in the rotation direction of the rotating body
An angle corresponding to 4 H, i.e. approximately 360°/26'
It is installed in a position that is advanced by 1/4 of 2.5. Note that 262.5 is the number of horizontal synchronization signals for one field.

By installing the special playback heads C and D in the above positional relationship, the 1/2H skew distortion correction circuit can be used during all special playbacks in the case of the magnetic tape recording pattern shown in Figure 4. .

This will be explained using Table 1.2.

Table 1 Below is the margin Table 2 In other words, Table 1 shows the amount of skew generated during playback by special playback heads C and D.
When installed in the positional relationship shown below, approximately -11/4H or approximately -1/4H when switching heads in still image playback mode, double-speed playback mode, and slow playback (frame-by-frame) mode, respectively.
A skew of about 1/2 H occurs, but in the case of an qIp IC with a relationship of 180° + 1/4 H, a skew of about 1/2 H occurs once every two head changes. Note that the slow playback herein refers to so-called intermittent slow playback, which is a frame-by-frame type in which normal playback and still image playback are performed alternately.

In addition, in the case of special playback using recording head ASB, as shown in Table 2, at the time of head switching during reverse playback,
Furthermore, during fast-forward playback and rewind playback, a sag of about 1/2H occurs each time when 1-rack C is exceeded.

As described above, since the special reproduction head can be set to the relationship of 1ε30°+1/4H, it can be seen that the Schiko distortion is 1/2 + -1 in any special reproduction.

Therefore, the skew distortion correction circuit shown in FIG. 5 can be used as is to correct skew distortion during all special reproductions.

The above-mentioned embodiments are applied when the positions of the horizontal synchronization signals are not aligned between adjacent tracks. However, when the positions of the horizontal synchronization signals are aligned, it is necessary to install the special playback head. In the apparatus shown in FIG. 1 in which the position is shifted by 1/4 to 1, on the contrary, a skew distortion of about 1/4 H always occurs. To solve this problem, it is sufficient to always delay the signal repopulated by the head C, which is mounted with a 1/4H shift, by 1/4H.

A block diagram of the device showing the circuit configuration for this purpose is shown in FIG.

In FIG. 2, the input terminal 11 is connected to a 1/' 2 Ll knee detection circuit 12 and also to a first 1/4H delay line 13. In FIG. Furthermore, the input terminal 11 is connected to one input terminal 161 of the first switch circuit 16 and one input terminal 17b of the second switch circuit 17. First 1/4H delay line 13
The output of is connected to the second 1/4.1-1 delay line 15 and to the other input terminal 17a of the second switch circuit 17. The output of the second 1/4 H Rinobu wire 15 is connected to the other input terminal 15a of the first switch circuit 15. 1/2H skew detection circuit 1
The output of 2 is connected to a bistable multivibrator 14,
The bistable multivibrator 14 is connected to the first switch circuit 1
Outputs a signal to switch 6. The output terminal of the first switch circuit is one input terminal 1 of the third switch circuit 18.
8a, and the output terminal of the second switch circuit 17 is connected to the other input terminal 18b of the third switch circuit 18. The output terminal of the third switch circuit 18 is connected to the output terminal 19. Second switch circuit 17
is controlled by a head switching pulse supplied to terminal F20, and the third switch circuit 18 is controlled by a 7-mode signal supplied to terminal 21.

The 1/2 skiff-1 detection circuit 12 and the bistable multivibrator 14 are the same as shown in FIG.
14 and the first switch circuit 16 is the fifth
It is functionally the same as the one shown in the figure. Therefore, when performing special playback on a magnetic tape recorded in the recording mode as shown in FIG.
is the terminal 21 so that the signal on the input terminal 18a side is outputted.
is switched by a signal supplied to the

In addition, in order to perform special playback using a magnetic tape in which the horizontal synchronizing signals of adjacent racks are aligned, the third switch circuit 18 is connected to the input terminal 1 when connected to the recording head.
The signal on the input terminal 8a side is selected, and when using the special reproduction head, the signal on the input terminal 18b side is selected. Further, when a special reproduction head is used, the second switch circuit 17 is switched in synchronization with the switching of the two heads. In other words, the reproduction number 45 by the head C shifted from the 1/41-1 position is reproduced by the first 1/41-1 position.
'I Cover to pass through the l-1 delay line.

Due to the above operation, the signal appearing at the output terminal 19 is completely free of skew distortion.

[Effects of the Invention] As described above, according to the special playback device of the present invention, the two special playback heads are mounted in a positional relationship that is equivalent to 1/4F1 with respect to 18o. In addition, by using two 1/4H delay lines, it is possible to very efficiently correct the occurrence of S:1-1-distortion during any special reproduction.

[Brief explanation of drawings]

FIG. 1 is a plan view of a rotating body on which a magnetic head is mounted, which is applied to the present invention, FIG. 2 is a circuit diagram of a skew distortion correction circuit applied to this invention, and FIG. 3 is a conventional one. FIG. 4 is a plan view of a rotating body on which a magnetic head is mounted, which is applied to a special playback device. FIG. 4 is a pattern diagram showing the recording 1-rack pattern of a magnetic tape used in a home VTR. FIG. FIG. 2 is a circuit configuration diagram showing a conventional skew distortion correction circuit. A, B...Magnetic head for recording, C, D...
...Magnetic head for special reproduction, 20...Head switching pulse input terminal, 21...Mode Shinkyu input terminal agent (7317) Patent attorney Masasa Norichika j Figure 2

Claims (3)

[Claims] (1) Two magnetic heads with different azimuth angles mounted on a rotating body with a positional interval of 180° record video tracks diagonally and sequentially on a magnetic tape run at a predetermined speed. The magnetic tape is run at different speeds to obtain two different azimuth angles.
At the same azimuth angle as in the first embodiment in which the video signal is reproduced by two heads, one head is angled at an angle corresponding to 1/4H (H is the horizontal period) in the rotational direction of the rotating body. means for selecting a second mode of reproducing the video signal using two heads mounted in advance, and means for correcting skew when a skew occurs in the reproduced signal from the reproducing means using a delay line. Skew distortion correction device for video tape recorders (2) The correction means includes a 1/2 delay line, a 1/2H skew detection circuit, and a switch circuit, and when a skew is detected by the 1/2H skew detection circuit in the first and second aspects. The skew distortion correction device for a video tape recorder according to claim 1, wherein the device is configured to switch between outputting a signal passed through a 1/2H delay line and directly outputting the signal at the output end. (3) The correction means has a 1/4H delay line and a switch circuit, and when in the second mode, only the reproduced signal of the head mounted advanced by an angle corresponding to 1/4H is 1/4H.
A skew distortion correction device for a video tape recorder according to claim 1, characterized in that the device is configured to switch to output the output to the output end with a delay of 4H.