JPH0441403B2 - - Google Patents

Description

[Detailed description of the invention] purpose of invention (Industrial application field) The present invention relates to a magnetic tape inspection method.

(Prior Art) In a normal VTR device, a rotating cylinder 1 shown in FIG. 3 is provided in the magnetic tape running system, and two magnetic heads 2 are placed in this rotating cylinder 1 at positions facing each other at 180 degrees. It is set in. These magnetic heads 2 alternately magnetically record video signals on the magnetic tape.
This video signal track (magnetic recording track)
are usually inclined at a predetermined angle with respect to the magnetic tape and are adjacent to each other with a small gap between them.

As shown in FIGS. 4 and 5, each magnetic head 2
Gaps Ga and Gb are formed in the chips 3a and 3b, and each gap Ga and Gb is inclined in different directions with respect to the rotation axis of the rotating cylinder 1 (this angle of inclination is called an azimuth angle). ).
As a result, since the direction of magnetic recording is different on the video signal track by each magnetic head 2, even if the position of the magnetic head shifts slightly during playback, the inconvenience of picking up recording from the adjacent video signal track is prevented. has been done.

By the way, when inspecting whether the running system etc. of a VTR device is operating normally, a method has been developed for optically inspecting the magnetic tape actually magnetically recorded by the magnetic head of the VTR device. That is, the magnetic tape on which the video signal is magnetically recorded is immersed in a special developer containing iron powder or magnetic powder such as cobalt or manganese, and the iron powder is attached to the video signal track (hereinafter, this process is referred to as developing). ). Then, light is applied to this magnetic tape, reflected by a video signal track to which iron powder is attached, and a magnifying optical system is used to inspect whether the reflected image of this video signal track has linearity or not. It is.

In the above method, simply applying light will not
Both reflected images of the video signal track due to different magnetic heads 2 will appear. As mentioned above, since these video signal tracks are adjacent to each other with a small gap in between, it is easy to determine whether the video signal track is drawing a normal trajectory from the reflected images of both video signal tracks. I can't.

For this reason, in the past, one magnetic head 2 was removed from the rotating cylinder 1 and magnetic recording was performed only by the other magnetic head 2, thereby forming a video signal track with a sufficient gap and performing the above-mentioned optical recording. I was conducting an inspection.

(Problem to be solved by the invention) However, in the above method, the magnetic head 2
had to be attached to and removed from the rotating cylinder 1, which made inspection work very difficult.

Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention installs a magnetic tape at a predetermined position, and a gap of one of the magnetic heads that performs magnetic recording on the magnetic tape. By irradiating the magnetic tape with parallel light from a direction substantially perpendicular to the direction of the tape, the light is not reflected from the magnetic recording track of one of the magnetic heads, and the light is reflected from the magnetic recording track of the other magnetic head. The present invention provides a magnetic tape inspection method characterized in that the reflected image of the magnetic recording track is inspected using an enlarging optical system.

(Embodiment) As shown in FIG. 6, a video signal track 6 is recorded on the magnetic tape 5 by the two magnetic heads 2.
A, 6b are formed, and a timing signal track 6c is formed by a magnetic head (not shown) different from the magnetic head 2 described above. This magnetic tape 5 is developed and optically inspected.

As a result of experiments, the inventor discovered that when parallel light is incident on the magnetic tape 5, no light is reflected from one of the video signal tracks 6a (or 6b) at a specific irradiation angle.

The above principle will be explained in detail. The gaps Ga and Gb of the magnetic head 2 that performs magnetic recording have different azimuth angles as described above, and come into contact with the magnetic tape 5 at different angles as shown by the dotted lines in FIG. Signal tracks 6a, 6b are formed. In each video signal track 6a, 6b,
The direction of magnetic recording is different. When the developed magnetic tape 5 is irradiated with parallel light from a direction (arrow direction in the figure) almost perpendicular to the direction of one gap Ga, no light is reflected from the video signal track 6a due to this gap Ga. , the light is reflected from the video signal track 6b by the other gap Gb.

As mentioned above, one video signal track 6a
If the irradiation angle of the parallel light is determined so as to eliminate the reflected image of the other video signal track 6b (or 6b), the reflected images of the other video signal track 6b (or 6a) can be displayed with sufficient intervals as shown in FIG. I can do it.

The irradiation angle of the parallel light with respect to the longitudinal direction of the magnetic tape 5 (the irradiation angle when the magnetic tape 5 is viewed from directly above) is determined as follows. Fig. 9 Middle line T
indicates the longitudinal direction of the magnetic tape 5, and line R indicates the running direction of the magnetic head 2 relative to the magnetic tape 5, that is, the longitudinal direction of the video signal tracks 6a, 6b. The angle between line T and line R (lead angle) is indicated by Θr. Further, a line N in the figure indicates a direction perpendicular to the line R, that is, the direction of the rotation axis of the rotary cylinder 1. Lines Ga and Gb indicate the direction of the gap, and the angle (azimuth angle) between these lines Ga and Gb and line N is
are denoted by Θa and Θb. Further, line J indicates a direction perpendicular to gap Ga, and therefore indicates the direction of irradiation of parallel light that is not reflected by video signal track 6a. The angle between this irradiation direction J and the longitudinal direction T of the magnetic tape 5 is assumed to be Θj. Similarly, line K indicates a direction perpendicular to gap Gb and therefore indicates the direction of illumination of parallel light that is not reflected by video signal track 6b. Let the angle between this irradiation direction K and the longitudinal direction T of the magnetic tape 5 be Θk. ΘJ,
Θk is determined by the following formula.

Θj = Θr - Θa Θk = Θr + Θb Next, an example of the apparatus for carrying out the method of the present invention will be described in the first example.
This will be explained with reference to FIGS. In the figure, 11 is an X stage that moves horizontally in the X-axis direction, and 12 is a Y stage.
This is a Y stage that moves horizontally in the axial direction. A support mechanism (not shown) for supporting the magnetic tape 5 is provided above the X stage 11.

The stages 11 and 12 are moved by moving mechanisms 14 and 15. Moving mechanism 1
Reference numerals 4 and 15 have built-in optical encoders and the like, and generate electric pulses each time each stage 11 and 12 is moved a unit distance. Moving mechanism 14, 15
The electrical pulses from the counter (not shown)
It is now being sent to and counted.

A magnifying optical system 20 is arranged above the stage 11, and on both sides of the magnifying optical system 20 there are two light irradiation devices for irradiating parallel light onto the magnetic tape 5 placed on the X stage 11. 31 and 32 are arranged.

The irradiation angle from the light irradiation devices 31 and 32 (the irradiation angle when viewed from directly above) is set at a predetermined angle Θj,
It has Θk. For example, if the lead angle Θr is approximately 6°,
When the azimuth angles Θa and Θb are approximately 6°, the irradiation angle Θj of the light irradiation device 31 is approximately 0°, that is, approximately parallel to the longitudinal direction of the magnetic tape 5, as shown in FIG. The irradiation angle Θk of No. 32 is about 12°. In addition, the light irradiation devices 31, 3 when viewed from the side
There is no particular restriction on the irradiation angle from 2, that is, the elevation angle, but the magnifying optical system 20 and the light irradiation device 31,
32 and the reflection efficiency, the angle is set to about 45° as shown in FIG.

The magnifying optical system 20 has an objective lens 21, an eyepiece lens 22, and a half mirror 24 arranged between these lenses 21 and 22.

Parallel light from the light irradiation devices 31 and 32 is reflected by the magnetic tape 5, and a portion of the reflected light passes through the enlarging optical system 20 and reaches the eyes of the examiner.

A portion of the reflected light from the magnetic tape 5 is reflected by a half mirror 24 of an enlarging optical system 20, passes through a fine slit 25, and is converted into an electrical signal by a photomultiplier tube 26. .

The developed magnetic tape 5 is inspected using the above-described apparatus. First, the magnetic tape 5 is set on the X stage 11. In this set state,
As shown in FIGS. 2 and 7, the longitudinal direction of the magnetic tape 5 is parallel to the X axis.

Next, the magnetic tape 5 is irradiated with parallel light from the light irradiation device 31 . As a result, as shown in FIG. 7, no light is reflected from the video signal track 6a, but only by the video signal track 6b and the timing signal track 6c. These reflected images are inspected by the magnifying optical system 20.

First, the timing signal track 6c is examined. That is, the X stage 11 is moved to move the magnetic tape 5 in the longitudinal direction, and the reflected image of the timing signal track 6c is detected by the photomultiplier tube 26 via the slit 25. Based on this detection signal and the count of electric pulses from the moving mechanism 14 of the X stage 11, the interval between the timing signal tracks 6c is measured. If this interval is constant, it means that the running speed of the magnetic tape 5 in the running system of the VTR device is constant. By the way, even if there is a slight deviation in the running speed, the VTR
There is no effect on the performance of the device.

Next, the video signal track 6b is examined. That is, the Y stage 12 is moved to move the magnetic tape 5 in a direction perpendicular to the longitudinal direction, and the image of the video signal track 6b is detected by the photomultiplier tube 26 through the slit 25. Based on this detection signal and the count value of electric pulses from the moving mechanism 15 of the Y stage 12, the video signal track 6
Measure the distance b. At this time, calculation processing is performed so as to obtain the interval between the center lines of the width of the video signal track 6b. If the interval between the video signal tracks 6b is constant, it can be assumed that the linearity is maintained. Note that this measurement is performed at a plurality of locations along the longitudinal direction of the magnetic tape 5. Also,
This linearity measurement is calculated taking into account the speed deviation of the timing signal.

In the above measurement, the slit 26 is rotated in accordance with the reflected images of the timing signal track 6c and the video signal track 6b, and adjusted so as to be parallel to the respective reflected images. Thereby, the detection sensitivity of the photomultiplier tube 26 can be maintained.

Next, parallel light is irradiated from the light irradiation device 32, and the linearity of the video signal track 6a is measured in the same manner as described above.

Note that the present invention is not limited to the above-mentioned embodiments, and various embodiments are possible. For example, it can be applied to magnetic tapes used in other than VTR equipment.

Effects of the Invention As explained above, according to the method of the present invention, by irradiating a developed magnetic tape with parallel light at a predetermined angle, a magnetic recording track is recorded by a plurality of magnetic heads having different gap azimuth angles. ,
Reflection images can be selectively obtained, and optical inspection of magnetic recording tracks can be easily and accurately performed from reflection images having sufficient spacing.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of an apparatus for carrying out the method of the present invention, FIG. 2 is a plan view showing the angle of irradiation of parallel light onto a magnetic tape, and FIG. 3 is a front view of a rotating cylinder equipped with a magnetic head. 4 and 5 are enlarged front views of the chips of each magnetic head, FIG. 6 is a plan view of the magnetic tape showing the magnetic recording tracks, and FIG.
The figure is a plan view of a magnetic tape with magnetic recording tracks selectively reflected; FIG. 8 is a plan view showing the principle of the method of the present invention; and FIG. It is a top view which shows the principle for determination. Ga, Gb...gap, 2...magnetic head, 5
...magnetic tape, 6a, 6b...video signal track (magnetic recording track), 20...magnifying optical system,
25...Slit, 26...Photomultiplier tube, 3
1, 32...Light irradiation device.

Claims (1)

[Claims] 1. In a method of optically inspecting a magnetic recording track by attaching magnetic powder to the magnetic tape after magnetic recording is performed on a magnetic tape using a plurality of magnetic heads with gap azimuth angles different from each other, the magnetic tape is placed at a predetermined position. At the same time, by irradiating the magnetic tape with parallel light from a direction almost perpendicular to the direction of the gap of the one magnetic head that performed magnetic recording on the magnetic tape, magnetic recording by one of the magnetic heads is performed. A magnetic tape inspection method characterized in that the light is not reflected from the track, but is reflected from a magnetic recording track formed by the other magnetic head, and the reflected image of the magnetic recording track is inspected by an enlarging optical system.