JPH0536160A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To diminish the quantity of data errors of a regenerative signal even in the case of digital recording with high recording density. CONSTITUTION:A tape tension value is outputted by a tape tension setting circuit 12, while tape tension corresponding to this tape tension value is given to a magnetic tape by a servo circuit 13. Under such circumstances, a digital video signal regenerated by a magnetic head 2 is supplied to an error detecting circuit 10, where data error quantity is detected. This data error quantity is compared with reference error quantity R by a comparator 11, and whether this data error quantity is in excess of the reference error quantity or not is decided by a decider 16. When the data error quantity is not in excess of the reference error quantity, the same tape tension value is outputted by the tape tension setting circuit 12 to maintain the tape tension as it is, and when the data error quantity is in excess of the reference error quantity, the tape tension value is corrected by a correction value from a tape tension variable mode generator 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus suitable for digitally recording / reproducing a video signal at a high recording frequency.

[0002]

2. Description of the Related Art In a helical scan type magnetic recording / reproducing apparatus (hereinafter referred to as VTR), when the tape tension changes, the contact state between the magnetic tape and the magnetic head cannot be kept stable and skew distortion occurs. As a result, the quality of the reproduced image deteriorates. Therefore, in the past, for example, “Mechanical Design” by Jiro Kajino p. As described in 66, the rotation of the reel motor is controlled so that the tape tension becomes a predetermined value. The range of this tension value is generally defined by a standard.

[0003]

However, this tape tension is, for example, 2.3N ± 0.3N at the drum winding center.
Since the range is wide, even if the value is controlled to a constant value within this range, the magnetic head, the magnetic head, the magnetic head, the protruding amount of the magnetic head at the time of recording, the tip shape of the magnetic head, the surface condition of the magnetic tape, etc. In some cases, the spacing between the tapes becomes large and sufficient playback output cannot be obtained.

Further, the friction coefficient of the magnetic tape varies about 0.03 depending on the production lot.
Generally, the tape tension is controlled by the supply reel unit, and the winding angle of the fixed guide is about 200 ° up to the center of winding the drum. Therefore, the increase in the magnetic tape tension is about 40 gf. But the tape tension changes significantly. In such a case, the contact state between the magnetic tape and the magnetic head may change, and a sufficient reproduction output may not be obtained.

Particularly, in a digital VTR having a high recording density, the recording frequency is about 100 MHz or higher, and the relative speed between the magnetic head and the magnetic tape is 50 m / m.
Since it is sec or more, the floating amount of the magnetic tape on the outer circumference of the drum is large, the spacing between the magnetic head and the magnetic tape becomes unstable, and data error of the reproduction signal is likely to occur. This spacing amount is approximately 0.1 μm, and it is necessary to suppress the variation in spacing to approximately 20% or less. Therefore, it is very difficult to suppress the change in spacing and reduce the amount of data error simply by controlling the tape tension to a constant value.
It is necessary to make the running adjustment of the magnetic tape, the management of the magnetic tape surface state, the control of the allowable amount of wear of the magnetic head, and the like more strict than in the past.

The object of the present invention has been made in consideration of the above points, and it is possible to solve such a problem and reduce the data error amount of the reproduced signal even in the case of digital recording / reproduction of high recording density. It is an object to provide a magnetic recording / reproducing device that can be used.

[0007]

To achieve the above object, the present invention comprises means for detecting a data error amount of a reproduced signal and means for controlling tape tension based on the detection result of the means. .

[0008]

In order to minimize the spacing between the magnetic head and the magnetic tape in accordance with the detected data error amount,
Tape tension is controlled. As a result, the data error amount of the reproduction signal is suppressed and the quality of the reproduced image is improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention, in which 1 is a magnetic tape, 2 is a magnetic head, 3 is a drum, 4 is a guide roller, 5 is a tension post, and 6 is full width erasing. Magnetic heads, 7a and 7b are guide posts, 8 is a reproduction amplifier, 9 is a signal processing circuit, 10 is an error detection circuit, 11 is a comparator, 12 is a tape tension setting circuit,
13 is a servo circuit, 14 is a supply reel, 15 is a drum winding central portion, 16 is a judging device, and 17 is a tape tension variable mode generator.

In FIG. 1, the magnetic tape 1 is pulled out from the supply reel 14, passes through the guide roller 4, the tension post 5 and the full width erasing magnetic head 6 and then the outer circumference of the drum 3 is predetermined by the guide posts 7a and 7b. Drive over an angle. The magnetic head 2 on the drum 3 scans the magnetic tape 1 while rotating, and reproduces the digital video signal recorded on the magnetic tape 1.

The reproduced digital video signal from the magnetic tape 1 by the magnetic head 2 is amplified by the reproduction amplifier 8 and then subjected to predetermined processing by the signal processing circuit 9 and supplied to the error detection circuit 10. The error detection circuit 10 detects the data error amount of the reproduced digital video signal, and the comparator 11 compares this data error amount with the reference error amount. The comparison result of the error detection circuit 10 is sent to the decision unit 16. The judging device 16 judges from the comparison result whether or not the data error amount exceeds the reference error amount, and operates the tape tension setting circuit 12 and the tape tension variable mode generator 17 according to the judgment result.

The tape tension setting circuit 12 outputs a tape tension value for giving a tape tension to the magnetic tape, and the servo circuit 13 performs a tension servo operation with this tape tension value to control the rotation of a reel motor (not shown). The tape tension corresponding to this tape tension value is obtained. When a certain tape tension value is output from the tape tension setting circuit 12 and the data error amount detected by the error detection circuit 10 by the tape tension at this time does not exceed the reference error amount,
The tape tension setting circuit 12 determines the same tape tension value by the servo circuit 13 based on the judgment result of the judging device 16 indicating this.
To maintain the tape tension. On the other hand, when the data error amount detected by the error detection circuit 10 exceeds the reference error amount, the determiner 16 further operates the tape tension variable mode generator 17. Therefore, the tape tension variable mode generator 17 generates a correction value having a predetermined size and supplies it to the tape tension setting circuit 12. The tape tension setting circuit 12 forms a corrected tape tension value by adding or subtracting the correction value to the tape tension value up to this point, and sends the corrected tape tension value to the servo circuit 13. The servo circuit 13 controls the rotation of the reel motor on the basis of the corrected tape tension value, and changes the tape tension from the previous tape tension by the amount corresponding to this correction value, and detects the data error amount detected by the error detection circuit 10. To be small. If the data error amount detected next by the error detection circuit 10 still exceeds the reference error value, the tape tension variable mode generator 17 further changes the correction value by one step and sends it to the tape tension setting circuit 12. The tape tension value is further corrected to form a new corrected tape tension value to further change the tape tension. In this way, the tape tension changes stepwise, and when the data error amount detected by the error detection circuit 10 does not exceed the reference error amount, the tape tension variable mode generator 17 sets the correction value at that time to the tape tension setting value. Continue to feed the circuit 12 to fix the tape tension value.

The tape tension setting circuit 12 has a predetermined tape tension (hereinafter referred to as initial tape tension).
Initial value that causes (hereinafter referred to as initial tape tension value)
Is set, and the tape tension setting circuit 12 sends this initial tape tension value to the servo circuit 13 when the magnetic recording / reproducing apparatus is started. Therefore, at this start-up, the initial tape tension is applied to the magnetic tape 1. When the initial tape tension is applied and the data error amount detected by the error detection circuit 10 exceeds the reference error value, the tape tension value is corrected as described above. Hereinafter, such a tape tension value is referred to as a corrected tape tension value with respect to the initial tape tension value.

The tape tension value from the tape tension setting circuit 12 determines the tape tension value at the tension post 5, and the tape tension value at the drum winding central portion 15 is about 1.5 times that value. become.

FIG. 2 shows the tape tension setting circuit 1 shown in FIG.
2 is a block diagram showing a specific example of 2, wherein 18 is an initial tape tension setting device, 19 is an A / D (analog / digital) converter, 20 is an adder, and 21 is D / A (digital / analog) conversion. And 22 is an amplifier.

In the figure, the initial tape tension setting device 18
Gives the initial tape tension value. The initial tape tension setting device 18 is composed of, for example, a variable resistor, and can adjust the initial tape tension value. This initial tape tension value is converted into digital data by the A / D converter 19 and supplied to the adder 20. In this adder 20, when the tape tension variable mode generator 17 (FIG. 1) outputs the positive or negative correction value ΔT, the A / D converter 1
This correction value ΔT is added to the digitized initial tape tension value from 9. The output data of the adder 21 is converted into an analog tape tension value, then supplied to an amplifier 22 and added with an output voltage of a potentiometer (not shown) to obtain an initial tape tension value or a corrected tape tension value, which is the servo circuit 13. Is supplied to. The tape tension control by the servo circuit 13 is performed by setting the output voltage of the potentiometer connected to the tension post 5 to a constant value.

FIGS. 3 and 4 show how the correction value ΔT changes, and FIG. 3 shows the correction value ΔT for each step.
4 is a case where it sequentially increases, and FIG. 4 shows a case where it increases every step and then decreases every step. In these examples, one step is about 2 seconds, and the unit correction value is 3 g. The time of about 2 seconds is determined in consideration of the time constant (about 1 second) of the tape tension setting circuit 12. Therefore, in FIG. 1, 1.5 seconds after the servo circuit 13 takes in the initial tape tension value or the corrected tape tension value from the tape tension setting circuit 12, the error detection circuit 10 operates and reproduces for about 1/30 seconds. The data error amount of the digital video signal is detected, and the detected value is sent to the comparator 11.

FIG. 5 shows the dependency of the data error amount on the tape tension in one scanning period of the drum. According to the experiment, the first ⅓ scanning period of the first scanning period has the remaining two. It was found that the tension dependence of the data error amount was higher than that in the / 3 scan period. Therefore, by setting the data error amount to be compared by the comparison air 11 as the data error amount obtained in the first ⅓ scanning period of one scanning period, the tape tension value can be more accurately adjusted to the optimum value.

Further, in this embodiment, as shown in FIGS. 3 and 4, the tape tension was changed in 3 g steps and the maximum value of the correction value ΔT was set to 12 g, but this is erroneously corrected. This is to prevent the tape tension from changing extremely. Therefore, it is possible to increase the size. The reference data error amount was 10 to ³ in terms of word error rate.

Further, in this embodiment, the tape tension is automatically changed. However, a switch is provided, and after confirming the error state, the tape tension is changed by operating this switch. May be.

[0021]

As described above, according to the present invention,
Since the tape tension is controlled according to the data error amount of the reproduction signal, the recording signal can be reproduced under the condition that the spacing between the magnetic head and the magnetic tape is minimized. Therefore, the data error amount can be reduced and the image quality is improved. be able to.

Further, since the optimum tape tension can be set according to variations in the friction coefficient of the magnetic tape, environmental conditions (especially changes in temperature and humidity), wear of the magnetic head, and changes in the magnetic tape surface state, the magnetic head can be set. The life of the device can be extended, and stable recording and reproduction can always be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention.

FIG. 2 is a block diagram showing a specific example of a tape tension setting circuit in FIG.

FIG. 3 is a diagram showing an example of how a correction value output by a tape tension variable mode generator in FIG. 1 changes.

FIG. 4 is a diagram showing another example of how the correction value output by the tape tension variable mode generator in FIG. 1 changes.

FIG. 5 is a diagram showing a relationship between a tape tension and a data error amount in one scanning period of a magnetic tape.

[Explanation of symbols]

1 magnetic tape 2 magnetic head 10 Error detection circuit 11 comparator 12 Tape tension setting circuit 13 Servo circuit 16 Judgment device 17 Tape tension variable mode generator

Claims (2)

[Claims] 1. A magnetic recording / reproducing apparatus for digitally recording and reproducing a video signal on a magnetic tape, and means for detecting a data error amount of a reproduced signal, and applying the means to the magnetic tape based on the detection result of the means. A magnetic recording / reproducing apparatus provided with means for controlling tension. 2. A magnetic recording / reproducing apparatus adapted to control the running of a magnetic tape at a predetermined constant tape tension, a means for detecting a data error amount of a reproduction signal, and a detection result of the means for a reference error amount. And a means for controlling the tape tension so that the tape error is changed stepwise when the detection result exceeds the reference error amount and the data error amount of the reproduction signal is reduced. And a magnetic recording / reproducing apparatus. Method.