JPS61152178A - Tape tension controller of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce skew distortion by detecting a tape tension by turning of a tension arm at the recording time and detecting the tape tension by the variance of the horizontal scanning time of a reproduced video signal at the reproducing time to control the elongation of a tape. CONSTITUTION:When a magnetic tape 8 is run, a tension arm 17 is energized clockwise of the tape tension of the tape 8, and the turning angle of the arm 17 is so set that the tape tension and the energizing force of a tension spring 20 are balanced. A tape tension detecting means 21 detects the turning angle of the arm 17 to detect the tape tension. A horizontal scanning period variance detecting means 22 detects the variance of the period of a horizontal synchronizing signal of a reproduced video signal (a) to detect the variation of the horizontal scanning period. At the recording time, a changeover switch 23 is switched to the contact R side, and the output voltage of the means 21 is supplied to a driving circuit 24, and a supply reel motor 16 is so driven that the tape tension is constant. At the reproducing time, the output of the means 22 is supplied to the circuit 24. Thus, the skew distortion is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording/reproducing device that divides a video signal into a plurality of parts within one field and records each part on a different track. The present invention relates to a tape tension control device suitable for reducing skew distortion caused by discontinuity in horizontal scanning periods that occurs at the joints of video signals reproduced from each track.

[Background of the invention]

In recent years, in the field of television broadcasting technology, progress has been made in the direction of realizing the transmission of even higher quality video information than the current standard method. , MUS1i! New types of television signals such as C-MAC signals and C-MAC signals have been proposed.

The television signal containing such high-definition video information (hereinafter referred to as the high-definition television signal) has a frequency band that is more than twice that of the current standard television signal.
In order to record and reproduce this high-quality television signal using a magnetic recording and reproducing device, it is necessary to increase the relative speed between the tape and the head to more than twice that when recording and reproducing television signals using the current standard system.

Therefore, when recording and reproducing video and image signals of high-definition television signals by alternately scanning a magnetic tape with two rotating magnetic heads, as in the current helical scan type magnetic recording and reproducing apparatus, , the video signal to be recorded is 1
It is necessary to adopt a so-called segment recording method in which a field is divided into two or more and each divided video signal is recorded on a different track.

By the way, there are differences in the environment between recording and playback, etc.
The degree of elongation of the magnetic tape may be different during recording and playback, and due to this, during playback, the horizontal scanning period (horizontal synchronization signal period) K fluctuation occurs at the joint of the video signal reproduced from each track. arise. As a result, image distortion, or skew distortion, occurs at this seam.
When the segment recording method is adopted, this seam always exists in the projected screen, so as shown in Figure 11, skew distortion will appear at the seam A in the reproduced screen, greatly reducing the image quality. This will lead to deterioration.

In particular, in order to ensure high S/H and promote high-density direct recording, it is inevitable that thin metal tapes will become the mainstream for magnetic tapes. The degree of elongation varies greatly depending on the environment and other factors. Therefore, when such a low-rigidity magnetic tape is used, skew distortion becomes a particular problem.

As a conventional technique for reducing such skew distortion, for example, as disclosed in Japanese Utility Model Publication No. 58-15479, while a user visually views a screen displayed on a monitor,
It is known that a knob that can be operated extremely easily with a weak operating force is operated so that skew distortion is minimized.

However, in this conventional technology, since correction of skew distortion relies on visual inspection, the adjustment operation is very delicate and requires a great deal of time, and furthermore, adjustment is required every time playback is performed. Because of this, it is very troublesome.

In particular, in magnetic recording and reproducing apparatuses using the segment recording method, skew distortion appears in the playback screen, which requires adjustment for highly accurate skew distortion correction, which poses a serious problem.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques, to significantly reduce skew distortion without requiring manual adjustment, and to record high-quality television signals and reproduce high-quality images using the segment recording method. It is possible to provide a tape tension control device for nine magnetic recording sickle playback devices.

[Summary of the invention]

In order to achieve the objective, the present invention detects tape tension by rotating a tensile arm during recording,
The tension/length of the magnetic tape is controlled to keep the elongation of the magnetic tape constant, and during playback, the variation in the horizontal scanning period of the reproduced video signal is detected to control the tape tension of the magnetic tape. The feature is that the elongation of the magnetic tape is made equal during recording.

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

First, an example of a magnetic recording/reproducing device employing the present invention will be described as a second example.
This will be explained with a diagram. In addition, in FIG. 2, 1 is a drum device; 2. i is a rotating magnetic head.

3 is a tape guide, 4 is a guide roller, 5 is an impedance roller, 6 is an erase head, 7 is an audio/control head, 8 is a magnetic tape, 9 is a pinch roller, 1
0 is a capstan, 11 is a cassette, 12 is a supply reel stand, 13 is a take-up reel stand, 14 is a take-up reel,
15 is a supply IJ-rule, 16 is a supply reel motor, 17 is a tension arm, 1 is a tension pin, 19 is a rotation support, 19' is a stator, and 20 is a tension 9 spring.

In the figure, in the cassette 11, a supply reel 15,
A magnetic tape 8 is stretched between the take-up reels 14. When the cassette 11 is installed in a magnetic recording/reproducing apparatus, the supply reel 15 is mounted on a supply reel stand 12 directly connected to a supply reel motor 16, and the take-up reel 14 is mounted on a take-up reel stand 13.

When the recording mode or playback mode is designated, the magnetic chip 8 is pulled out from the cassette 11 and moved to the tape guide 3.
In other words, it is wound around the drum device 1 in a helical manner over a rather large angle of 1800 mm. At the same time, the magnetic tape 8 comes into contact with the tension pin 18, the erasing head 6, the inheatance roller 5, the guide roller 4, and the audio/control head 7, and is held between the pinch roller 9 and the capstan 10. , a magnetic tape 80 running path is formed. After that, Capsta/
10 rotates, and the magnetic tape 8 runs in the direction of the arrow (■).

Although not shown, the drum device 1 includes a rotating part and a fixed part, and a plurality of rotating magnetic heads are provided at equal intervals on the rotating part. Here, two rotating magnetic heads 2.2' are provided at an interval of 180°. Rotating magnetic head 2.
2' rotates in the direction of the arrow at a predetermined number of rotations and alternately scans the magnetic tape 8 for recording or reproduction.

Assume that a four-segment recording method is adopted in which a video signal is divided into four parts within one field and each part is recorded on a separate track. In this case, the rotating magnetic head 2
．． 2' rotates at 120 revolutions per second, and the third
As shown in the figure, one rotation of the magnetic head 2.2 alternately turns tracks A and B.

C, D, A, . . . are formed, and a 1/4 field video signal is recorded on each of these tracks. Therefore, one field of video signals is recorded on four tracks A, B, C, and D. Note that 1 indicated by CHl
The three tracks A, C, A, . . . are formed by one rotary magnetic head 2, and the other one indicated by CH2.
The third tracks B, D, . . . are formed by the other rotating magnetic head 2'.

During reproduction, tracks A, B, C, D, A, etc. are scanned by the rotating magnetic head 2.2' in the order of reproduction, and the video signals reproduced from these tracks are spliced together to form the original continuous image. to video signal. In this case, in order to prevent missing parts from occurring at the joints of video signals, the magnetic tape 8 is wound around the drum device 1 at a slightly larger angle of 180 degrees as described above, and the magnetic tape 8 is wound around the drum device 1 at a slightly larger angle than the magnetic head 2.2' for one rotation. An overlap period is provided in which the magnetic tape 8 is simultaneously scanned, and video signals reproduced by the rotary magnetic head 2.2' are switched (that is, head switching) during the overlap period with the magnetic tape 8.

Now, in such a magnetic recording and reproducing apparatus, the magnetic tape 8
In order to run the magnetic tape stably without sag, a back tension of 71 mm is added to the magnetic tape 8, but in the present invention,
At the time of recording, the elongation of the magnetic tape 8 is maintained at a constant level using a constant tape tension created by the back tensioner, and at the time of playback, the tape tension is adjusted by detecting fluctuations in the horizontal scanning period of the reproduced video signal.
The skew distortion that occurs in the reproduced screen is reduced by adjusting K so that the extension of the image is equal to that during recording.

FIG. 1 is a block diagram showing an embodiment of a tape tension control device for a magnetic recording/reproducing apparatus according to the present invention for reducing skew distortion, in which 21 is a tape tension detection means, 22 is a horizontal scanning period. fluctuation detection means,
23 is a changeover switch, 24 is a drive circuit, and 16 is a t
This is the supply reel motor shown in Figure a2.

In FIG. 1, tape tension detection means 21 detects tape tension by rotating a tension arm. That is, in FIG. 2, the tension arm 17 to which the tension pin 18 is attached is connected to the stator 19.
' is attached and is rotatable about the nine rotation support shafts 19, and is biased counterclockwise by a tension panel 20.

When the magnetic tape 8 runs, the tension arm 17 is biased clockwise by the tape tension of the magnetic tape 8, and the rotation angle of the tension arm 17 is adjusted so that this tape tension and the biasing force of the tension spring 20 are balanced. Set. Therefore, when the tape tension changes, the tension arm 17 rotates in the direction of the arrow, and by detecting the rotation angle of the tension arm 17, the tape tension can be detected.

The horizontal scanning period variation detecting means 22 detects a variation in the period of the horizontal synchronizing signal of the reproduced video signal a to detect the amount of variation in the horizontal scanning period. As explained earlier, if the elongation of the magnetic tape during playback is different from that during recording, the period of the horizontal synchronizing signal will vary at the joints of the video signals reproduced from each track. 22 detects this variation and outputs a voltage according to this variation.

The changeover switch 23 is closed to the R side during recording, and the output voltage of the tape tension detection means 21 is set to the changeover switch 2.
3 to the drive circuit 24, and the drive torque of the supply reel motor 16 is controlled so that the tape tension is constant. Therefore, the magnetic tape 8 (Fig. 2)
A certain tape tension is added to the magnetic tape 8.
is set to a constant extension state to ensure stable running.

On the other hand, during reproduction, the changeover switch 25 is closed to the P side, and the output voltage of the horizontal scanning period fluctuation detection means 22 is supplied to the drive circuit 24 via the changeover switch 23, and the reproduced video signal a
The driving torque of the supply reel motor 16 is controlled so that the horizontal scanning period of the supply reel motor 16 is constant. As a result, the back tension of the magnetic tape 8 changes, the tape tension changes, and the magnetic tape 8 becomes stretched in the same manner as during recording.

Therefore, skew distortion on the playback screen is significantly reduced.

FIG. 4(a) shows the tape tension detection means 21 of FIG.
25 is a vertical cross-sectional view showing a specific example of
2 is a conductive contact piece, 27 is a power supply terminal, and parts corresponding to those in FIG. 2 are given the same reference numerals.

Further, FIG. 4(b) is a plan view showing the substrate 25 of FIG. 4(a), and 28 is a resistive film.

In FIG. 4(a), a base plate 25 is attached to the stator 19' on which the rotation support shaft 19 is installed, and a rotation support is placed on this base plate 25 as shown in FIG. 4(b). A resistive film 28 is provided in an arc shape with respect to the axis 19. Further, the tension arm 17 is configured to slide the resistive film 28 on the substrate 25 as the tension arm 17 rotates.
A conductive contact piece 26 is attached to the conductive contact piece 26.
A power supply terminal 27, 27' is connected to one end of the resistive film 2B, and a constant voltage is applied thereto. Here, current terminal 2
When a constant voltage is applied between the power terminals 27' and 27 so that the 7 side is the glass and the power terminal 27 side is negative,
The flowing current changes depending on the distance (ie, resistance value) between the connection point of the power supply terminal 27 of the resistive film 28 and the contact point of the conductive contact piece 26.

Therefore, when the tape tension of the magnetic tape 8 increases, the tension arm 17 rotates clockwise as shown in FIG.
In figure (b), the resistive film 2 slides in the direction of arrow (a).
The resistance value due to 8 increases and the current decreases. Conversely, when the tension of the magnetic tape 8 decreases, the resistance value due to the resistive film decreases and the current increases in the same way. The voltage corresponding to the change in current becomes the output of the tape tension detection means shown in FIG.

Figure 3 shows the supply reel motor 1 shown in Figures 1 and 2.
6 is a longitudinal sectional view showing a specific example of 6, in which 29 is a fixed support shaft, 30 is a rotor magnet, 31 is a rotor holder, and 32
3 is a bearing, 33 is a stator coil, and 34 is a drive terminal. Components corresponding to those in FIG. 2 are given the same reference numerals.

In FIG. 3, a rotor holder 31 is rotatably attached to the fixed support shaft 29 via a bearing 52, and a rotor magnet 30 and a supply reel stand 12 are fixed to the rotor holder 31. Further, a stator coil 35 is provided integrally with the fixed support shaft 29 and facing the rotor magnet 30, and the stator coil 55 is provided with a drive terminal 3.
A drive current is supplied from a drive circuit 24 (FIG. 1) via 4. Supply reel 15 around which magnetic tape 8 is wound
is fitted and mounted on the supply reel stand 121C.

The drive current supplied to the stator coil 33 via the drive terminal 34 changes depending on the output voltage of the tape tension detection means 21 and the output voltage of the horizontal scanning period fluctuation detection means 22 shown in FIG. The change in current changes the torque produced in the supply reel motor 16, which changes the back tension on the magnetic tape 8 and controls tape tension.

FIG. 6 is a block diagram showing a specific example of the horizontal scanning period variation detecting means 22 in FIG. AND gate, 41 is a trapezoidal waveform forming circuit, 42
4 is a sample hold circuit, 43 is a delay circuit, 44 is an AND gate, and 45 is a voltage variable circuit.

FIGS. 7(a) and 7(b) are waveform diagrams showing signals of each part in FIG. 6, and signals corresponding to those in FIG. 6 are given the same reference numerals.

The operation of this specific example will be described below assuming that the 4-segment recording method described above is used.

There are 1800 tack devices (not shown) installed in the rotating part of the drum section 1 (FIG. 2) facing each other. Supplied to circuits 55,56. The delay circuit 35 generates a delay pulse C having a rising edge and a width τ0 at the front edge of the tack signal, and this is supplied to the pulse forming circuit 38 to generate a 120 Hz head switching signal which is inverted at every falling edge of the delay pulse C. d is formed.

On the other hand, in the delay circuit 56, a delay pulse e having a rising edge and a width τ is formed at the front of the tack signal S, and this delay pulse e is further supplied to a delay circuit 57 consisting of a monostable multipipe rake or the like. . This delay circuit 37 generates a gate pulse f which rises at the falling edge of the delay pulse e and has a width of 2H (where H is the horizontal scanning period). However, the center of this gate pulse f is made to coincide with the edge of the head switching signal d, and therefore the delay time τ of the delay circuit 36 is made shorter than the delay time τ0 of the delay circuit 35 by 1H. For this reason, the gate pulse f is applied during head switching (
In other words, it represents a 2H period centered around the joint of video signals reproduced from each track.

The reproduced video signal a is supplied to a horizontal synchronizing signal separation circuit 39, where the horizontal synchronizing signal g is separated.

This horizontal synchronizing signal g is supplied to the AND gate 40 together with the gate pulse f from the delay circuit 37.

For this purpose, the AND gate 40 extracts the horizontal synchronization signal existing in the 2H period centered on the joint of the video signal a reproduced from each track.

Therefore, the output signal of the AND gate 40 is supplied to a trapezoidal waveform forming circuit 41, a delay circuit 43 consisting of a monostable multivibrator, etc., and an AND gate 44, each consisting of two pulses per gate pulse f.

The trapezoidal waveform forming circuit 41 rises at a predetermined slope angle for 2H from the falling edge of the first pulse of the output signal of the AND gate 40, and the maximum value is V. A trapezoidal wave k is formed.

Similarly, the delay circuit 43 forms a gate pulse 1 whose width is larger than 1H at the rising edge of the first pulse of the output signal. This gate pulse 1 is supplied to an AND gate 44 to extract the second pulse j of the output signal.

The trapezoidal wave output from the trapezoidal waveform format circuit 41 is supplied to a sample and hold circuit 421C, and sampled using the pulse j from the AND gate 44 as a sampling pulse. The sampled voltage is held at least 1/4 field, and the hold voltage v' is supplied to the voltage variable circuit 45, and the voltage V'' formed by the voltage variable circuit 45 is the output voltage of the horizontal scanning period variation detection means 22. Become.

Therefore, assuming that there is no change in the horizontal scanning period at the joint of the video signals reproduced from each track, the time interval between two pulses in the output signal of the AND gate 40 is 1H, and therefore, the sample The voltage V' held by sampling the trapezoidal wave k in the hold circuit 42 is v0/2.

The voltage variable circuit 45 forms a voltage V, where the bias voltage is V'' (where % is a constant). Therefore, when the output voltage V' of the sample and hold circuit 42 is v0/2, K is v= v
This voltage V 2 is then supplied to the drive circuit 24 (FIG. 1). At this time, the elongation state of the magnetic tape 8 (FIG. 2) is the same as that during recording.

Further, as shown in FIG. 8, since the extension state of the magnetic chip 18 during reproduction is different from that during recording, the video signal a' reproduced from one track and the video signal a reproduced from the next track are connected. If the time length H' of the horizontal scanning period becomes shorter than 1H at the joint between the two combined video signals a, as is clear from FIG. The voltage V' that is sampled and held is V. /2 is also lower, so (VD/2-V') becomes positive, and from the above equation (1), v < v. For this purpose, the drive circuit 24
(FIG. 1) becomes lower and the torque of the supply reel motor 16 decreases. According to this K, the elongation state of the magnetic tape 8 is adjusted, and even at the joint of the video signal a, the time length of the horizontal scanning period becomes 1H.

Conversely, the time length H of the horizontal scanning period at the joint of the video signal a
′ becomes longer than 1H, the sample hold circuit 42
The output voltage V' is V. /2 is also higher, and the drive circuit 2
41/C The supplied voltage V 1 is higher than the bias voltage V 2 .

In this way, variations in the horizontal scanning period are detected every 1/4 field, that is, every joint of the reproduced video signal, and the torque of the supply reel motor 16 is controlled so as to eliminate this variation.

The tape tension when a noise bar appears on the playback screen, such as during variable speed playback, is controlled in the same manner as during recording by closing the selector switch 23 to the R side in FIG.

FIG. 9 is an explanatory diagram of another specific example of the horizontal scanning period variation detecting means 22 of FIG. 1, and shows a method of detecting the horizontal scanning period of a reproduced video signal.

In this specific example, every 8 intervals of the horizontal synchronization signal of the reproduced video signal, a clock φ having a frequency sufficiently higher than the horizontal synchronization frequency is used.
The amount of skew distortion is detected by counting the count value of each horizontal scanning period based on the count value when the time width of the horizontal scanning period is 1H. This clock φ is generated by an oscillation circuit that starts oscillating at the falling edge of the horizontal synchronizing signal g and stops oscillating at the rising edge, and is counted every horizontal scanning period by a counter that is reset every horizontal synchronizing signal g. be done.

As described above, by keeping the tape tension constant and keeping the elongation of the magnetic tape constant during recording, the magnetic tape runs stably and tracks are formed at regular intervals. Furthermore, during reproduction, by setting the elongation state of the magnetic tape to be equal during recording, the length of the horizontal scanning period at the joint of the video signal reproduced from each track can be set to 1H. There is no fluctuation in the horizontal scanning period in the spliced video signal,
As shown in FIG. 11, the skew distortion at the seam A of the playback screen is significantly reduced.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to eliminate fluctuations in the horizontal scanning period at the joints of the reproduced video signal due to head switching, and eliminate the skew that appears in the reproduced screen without the need for manual operation. Distortion can be significantly reduced, and even in the segment recording method, excellent effects can be obtained in that reproduced images of good quality can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a tape tension 7 control device of a magnetic recording/reproducing apparatus according to the present invention, and FIG. 2 is a block diagram showing an example of a magnetic recording/reproducing apparatus employing the present invention.
FIG. 3 is a track pattern diagram on a magnetic tape according to the segment recording method, FIG. ), FIG. 3 is a vertical sectional view showing a specific example of the supply reel motor shown in FIG. 1, and FIG.
7(a) and 7(b) are waveform diagrams showing signals of each part in FIG. 6, and FIG. 8 is a reproduced image when switching heads. An explanatory diagram showing fluctuations in the horizontal scanning period of the signal, Fig. 9 is 31
FIG. 10 is a schematic diagram showing skew distortion due to the segment recording method; FIG. 11 is a schematic diagram showing the skew distortion reduction effect according to the present invention. be. 1...Drum device 2.2...Rotating magnetic head 8...Magnetic tape 12...Supply reel stand 16...Supply reel motor 17... Tensilon arm 21... Tape tensilon detection means 22...
. . . Horizontal scanning period variation detection means 23 . . . Changeover switch. sai l sai 2 sai 35iI (ku) ya ≦ sai 7 fig (^) sai 7 (!I ke10 sai // I!I

Claims (1)

[Claims] In a magnetic recording and reproducing device that divides a video signal into multiple parts within one field and records them on different tracks,
a first means for detecting tape tension by rotation of a tension arm; a second means for detecting tape tension by variation in horizontal scanning time of a reproduced video signal;
a third means for selecting detection outputs of the first and second means; and a fourth means for adjusting tape tension according to the detection output selected by the third means; A tape tension control device for a magnetic recording/reproducing apparatus, wherein the means selects the detection output of the first means during recording and selects the detection output of the second means during reproduction.