JPH11273178A - Dynamic curvature measuring method of magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the dynamic curvature of a magnetic tape inexpensively and simply by canceling the movement of the width direction of the magnetic tape to dispense with requirements for the mechanical accuracy of a measurement device. SOLUTION: The quantity of the dynamic curvature of a magnetic tape 1 is calculated by arranging three pieces of displacement sensors 4 to 6 along the running direction of the magnetic tape 1 at a regular interval, detecting edge positions of the tape 1 with respective displacement sensors 4 to 6, calculating the difference between the average value of detection positions at the displacement sensors 4, 6 of both sides and a detection position at the center displacement sensor 5 and measuring the displacement quantity of the shape of the magnetic tape 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape having a length of several cm to several tens cm on the order of microns in the longitudinal direction of the tape.
The present invention relates to a method for measuring dynamic bending generated at a pitch.

[0002]

2. Description of the Related Art The dynamic bending of a magnetic tape means that when a magnetic tape is run, several centimeters to several tens of centimeters in the longitudinal direction.
Is a phenomenon in which the film is curved and displaced so as to meander in the width direction at the pitch (wavelength) of. The occurrence of this dynamic bending causes a change in the contact position of the magnetic tape with the magnetic head or the like during the running of the magnetic tape.
It changes the reproduction characteristics.

As a specific measurement of the dynamic curvature of the magnetic tape as described above, a method in which the displacement of the tape edge is measured by using one displacement sensor is as follows.
The detection cannot separate the measurement of the dynamic curvature (shape displacement) of the magnetic tape from the measurement of the movement displacement in the width direction that does not depend on the dynamic curvature of the tape during running. In order to increase the height, it is required to move the edge of the magnetic tape with high accuracy at a fixed position, or to move the displacement sensor with high accuracy while keeping the tape stationary without moving the tape, and this is mainly required. The measurement is achieved by improving the machine accuracy.

[0004] However, in order to obtain the above-mentioned accuracy, the measuring apparatus has become very complicated and expensive.

[0005]

By the way, high speed measurement of the dynamic curvature of the magnetic tape as described above is required, and accordingly, it is necessary to increase the tape feeding or the moving speed of the displacement sensor. It is desired to maintain the feed accuracy at high speed at higher speed, but at present it is difficult to achieve it.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it has been made possible to cancel a slight movement in the width direction which does not depend on dynamic bending in detecting an edge position of a magnetic tape. It is an object of the present invention to provide a method for measuring the dynamic curvature of a magnetic tape capable of performing high-speed measurement at a low cost and with a simple measurement that requires less mechanical precision.

[0007]

According to the present invention, which has solved the above-mentioned problems, three displacement sensors are arranged at regular intervals along the running direction of a magnetic tape, and each displacement sensor detects the edge position of the magnetic tape. By calculating the difference between the average value of the detection positions of the displacement sensors at both ends and the detection position of the center displacement sensor, the amount of displacement of the shape of the magnetic tape is measured to determine the amount of dynamic bending. It is characterized by the following.

As the displacement sensor, a laser displacement sensor, a CCD line sensor or the like can be used.

[0009]

According to the present invention as described above, the edge positions of the magnetic tape are detected by three displacement sensors arranged at equal intervals along the running direction of the magnetic tape, and the detection positions of the displacement sensors at both ends are detected. By calculating the amount of dynamic bending from the difference between the average value of and the position detected by the central displacement sensor, the movement component in the width direction independent of the dynamic bending of the magnetic tape can be separated in the measurement. Thus, the dynamic curvature can be measured with high accuracy, the requirement of the mechanical accuracy of the measuring device for improving the measurement accuracy is relaxed and reduced, and it can be easily and inexpensively prepared, and the measurement can be speeded up.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows a dynamic bending measurement state as an example, and FIG. 2 shows a cross-sectional state.

The magnetic tape 1 has tape guides 3 on both sides.
It is traveling in a state where it is held in. This magnetic tape 1
In the running of the magnetic tape, if there is a dynamic curve, the position of the edge 1a of the magnetic tape 1 is several centimeters due to the meandering shape.
Waveforms having a displacement on the order of microns are displaced with a pitch of up to several tens of cm. Further, in addition to the above-described dynamic bending, the running of the magnetic tape 1 generally varies in the width direction.

With respect to the running of the magnetic tape 1 as described above, a first method for detecting the displacement of the edge 1a of the magnetic tape 1 is described.
To three third displacement sensors 4 to 6 are arranged at equal intervals. The center second displacement sensor 5 is disposed at the center of the tape guides 3 and 3 on both sides, and the first and second guides 3 and 3 are located at the same distance from the center second displacement sensor 5 on both sides and close to the tape guides 3 and 3. The third displacement sensors 4 and 6 are provided so as to measure the edge position at three points.

The first to third displacement sensors 4 to 6
A known displacement sensor such as a laser displacement sensor or a CCD line sensor is used to measure a displacement amount of a tape edge position from a reference position. For example, a reference is made to a tape length (cm) as shown in FIG. Is measured (μm).

In response to the detection by each of the displacement sensors 4 to 6 as described above, the first and third displacement sensors 4 and 6 at both ends thereof are used.
Of the edge position due to the dynamic bending of the magnetic tape 1 by calculating the difference between the average value of the detected positions of the magnetic tape 1 and the detected position of the center second displacement sensor 5, and the dynamic bending as shown in FIG. The corresponding displacement (μm) is determined.

By the processing of the measured values and the detected values using the three displacement sensors 4 to 6 as described above, the first and third displacement sensors at both ends can be used for the fluctuation in the overall width of the magnetic tape 1. The average value of the detection positions of 4 and 6 is calculated as the second value at the center.
It can be separated and removed by subtracting it from the detection position of the displacement sensor 5, and the second displacement sensor 5 at the center after this processing is performed.
Is a detection value of only the fluctuation of the edge position based on the dynamic curvature of the magnetic tape 1.

That is, the displacement measured by the second displacement sensor 5 in the center of FIG. 3 measures a maximum variation of about 40 μm, and when the movement of the magnetic tape 1 in the width direction is subtracted therefrom, As shown in the measurement result of FIG. 4, the dynamic curvature of the magnetic tape 1 is such that the pitch in the tape length direction is about 1 unit.
It was required that the displacement amount be about 6 to 10 μm at 4 cm.

In some cases, photo interrupters can be used as the displacement sensors 4 to 6. In other words, the photointerrupter is normally used for detecting the ON-OFF position, but the position fluctuation range of the tape edge with respect to the sensor body depends on the number of rising edges where the position-voltage characteristic of the photointerrupter has linearity. 100 μm
When the area is set so as to be, the position can be detected in the same manner as the above-described displacement sensor. If this photo interrupter can be used, it is advantageous in terms of cost and size as compared with a laser displacement sensor or a CCD line sensor.

The deformation in the running of the magnetic tape includes bending in the width direction (cupping). This cupping is a deformation that curves in an arc shape when the magnetic tape is viewed in a cross section in a direction perpendicular to the running direction, and the edge position of the magnetic tape changes with the occurrence of this cupping,
When measuring the above-mentioned meandering dynamic curvature more precisely, it is preferable to eliminate the influence of the cupping.

At that time, the measurement is performed using a glass guide. Specifically, the magnetic tape was applied to a transparent curved glass covering the entire width of the magnetic tape, and the tape was run without cupping.In this state, the displacement of the edge position of the magnetic tape was measured, and the influence of cupping was eliminated. 1st to 3rd
By processing the edge positions of points as described above, the VTR
It becomes possible to measure the dynamic curvature of a shape close to that at the time of traveling in the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a dynamic bending measurement state according to one embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrows AA in FIG. 1;

FIG. 3 is a graph showing a measurement example of a displacement amount from a reference of an edge position with respect to a tape length by first to third displacement sensors.

FIG. 4 is a graph showing the amount of displacement corresponding to the dynamic bending with respect to the tape length after the conversion of the data of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 3 Tape guide 4-6 Displacement sensor

Claims (1)

[Claims] 1. Three displacement sensors are arranged at regular intervals along the running direction of a magnetic tape, and each displacement sensor detects an edge position of the magnetic tape. A method of measuring a dynamic curvature amount of a magnetic tape by measuring a displacement amount of a shape of the magnetic tape by calculating a difference from a position detected by a center displacement sensor.