JPH06301941A - Apparatus for measuring position of magnetic head - Google Patents

Abstract

PURPOSE:To measure the position of a magnetic head without moving a light emitting element and a detecting element for detecting the position of the light emitting element. CONSTITUTION:When a light from a light emitting element 1 is cast on a magnetic head 2 set to a drum 16 and the reflecting light is detected by a position detecting element 3, the position of the magnetic head 2 to the drum 16 is measured in this measuring apparatus. The using light from the light emitting element 1 is a linear beam and the position detecting element 3 is a two-dimensional element. Because of the use of the linear beam and the two-dimensional position detecting element, three-dimensional data of the magnetic head can be obtained while both the light emitting element and the two-dimensional position detecting element, are fixed (kept, immobile). Accordingly, the measuring apparatus itself is greatly simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head position measuring device which is suitable for use in measuring the amount of protrusion or wear of a rotary magnetic head provided in a video tape recorder.

[0002]

2. Description of the Related Art A rotary magnetic head provided on a video tape recorder is attached and fixed in a state of protruding from a peripheral surface of a drum by a predetermined length.

A rotary drum device 7 shown in FIG. 11 is of a medium drum rotary type and is formed by holding a lower drum 14, a middle drum 16 and an upper drum 18 coaxially, and the lower drum 14 is fixed to a chassis. Retained. Lower drum 14
Is supported by a drum shaft 22 via a bearing 20, and the drum shaft 22 supports the intermediate drum 16.

The drum support 12 fixes the upper drum 18 to the lower drum 14. As a result, the upper drum 18 and the lower drum 14 guide the magnetic tape 24 and the middle drum 1
6 is rotationally driven, and a plurality of magnetic heads 2 (2A to 2D in the figure) attached to the inner drum 16 are brought into sliding contact with the magnetic tape 24. In FIGS. 11 and 12, 26
Is a head mounting screw.

FIG. 13 shows the magnetic head 2 unfolded over 360 °. Actually, a total of 12 magnetic heads including a recording / reproducing head and an erasing head maintain a predetermined height relationship. It is attached and fixed to the middle drum 16.

In the video tape recorder of this type, the above-mentioned magnetic head 2 is projected from the outer peripheral surfaces of the rotary drums 14 and 18 by a predetermined amount. When the drum is assembled, the projected amount is measured by using a dial gauge or the like. The magnetic head 2 is attached.

If the amount of protrusion of the magnetic head 2 is greater than or equal to a specified value or less than the prescribed value, the ideal contact state between the magnetic head 2 and the magnetic tape 24 cannot be ensured, so that the magnetic head 2 is easily worn. There is an adverse effect such as severe damage to the magnetic tape 24. When the magnetic head 2 is used for a long period of time, it wears, so that not only the head protrusion amount but also the electromagnetic conversion characteristics change.

For this reason, in this type of video tape recorder, the amount of protrusion is adjusted so as to be a prescribed amount at the time of shipment.
Further, the amount of head wear is detected by periodically measuring the amount of projection of the head, and the magnetic head is replaced as necessary. Therefore, a magnetic head position measuring device is required.

As a magnetic head position measuring device, there is a device for detecting the position of the magnetic head by using an optical method as disclosed in Japanese Patent Laid-Open No. 62-158616. In this system, for example, a laser beam is applied to the magnetic head and the light receiving position of the reflected light is measured to measure the protrusion amount of the magnetic head with respect to the outer peripheral surface of the drum.

An example of the amount of protrusion of the magnetic head observed by using this measuring device is shown in FIG. The signal level U1 of the output signal S0 is detected at the timing when the magnetic head crosses the irradiation position of the light beam LA1, and the position of the sliding contact surface of the magnetic head is detected.

Further, the signal level U2 of the output signal S0 is detected during a period in which the outer peripheral surface of the middle drum 18 crosses the irradiation position of the light beam LA1, that is, before the time t1 or after the time t2, and from this, Y = | U1-U2 | ... (1) is executed to detect the protrusion amount Y of the magnetic head. The shape of the head can be known from the amount of protrusion, and the position and amount of wear of the head can be known from this.

The plurality of magnetic heads are not mounted in the same plane of rotation of the middle drum 16, but are mounted and fixed in different height directions (h direction) as shown in FIG. .

Since the beam diameter of the laser beam is narrowed down to the same extent as the width of the head gap (width in the height direction of the head) so as to improve the measurement accuracy, the position of one magnetic head is measured. However, laser light must be scanned in the height direction of the magnetic head (drum rotation axis direction).

In order to measure the protrusion amount of all the magnetic heads having different heights, each time the measurement of the magnetic heads existing in the same plane with the laser light irradiation system and the light receiving system is completed, The position of the measuring device is readjusted, the measuring position is moved so as to face the magnetic head existing in another plane, and in that state, the measurement is performed again by scanning in the height direction of the magnetic head. This position adjustment in the height direction may be performed automatically or manually.

[0015]

As described above, the conventional magnetic head position measuring device measures the position by scanning the laser beam in the height direction of the magnetic head even if the magnetic heads exist in the same plane. It is carried out. To measure a magnetic head lying in another plane, the measuring device has to be moved to another position.

Therefore, the adjustment of the laser beam irradiation position is troublesome. When there are many magnetic heads as shown in FIG. 13 and the heights of the magnetic heads attached and fixed are different, the position adjustment of the measuring device becomes more complicated and troublesome, and the measuring device itself has a height direction. Since the position adjusting means must be attached, there is a drawback that the configuration becomes complicated.

Therefore, the present invention has solved such a conventional problem, and a plurality of devices having different height directions at the time of mounting can be provided without providing such a height adjusting device in the measuring device. The present invention proposes a magnetic head position measuring device capable of simultaneously measuring magnetic heads.

[0018]

In order to solve the above-mentioned problems, according to the present invention, light from a light emitting element is applied to a magnetic head mounted on a drum, and the reflected light is received by a position detecting element. In the magnetic head position measuring device configured to measure the position of the magnetic head with respect to the drum, a linear beam is used as the light from the light emitting element and a two-dimensional element is used as the position detecting element. It is characterized by.

[0019]

The beam shape of the laser light emitted from the light emitting element 1 is a linear spot as shown in FIG. 2, and the length of this linear spot is the width in the height direction of the magnetic head attached to the middle drum 16. It is selected to include at least wh (FIG. 3). In the embodiment, the length is selected so that all of the plurality of magnetic heads 2 mounted on the middle drum 16 can be simultaneously covered (h or more in FIG. 13).

When the magnetic head is obliquely scanned with this linear spot, the data (projection amount) in the direction b in FIG. 3 and the width direction wh of the magnetic head are obtained for each unit time. If it is continuously performed in the length direction L, three-dimensional information can be obtained regarding the protrusion amount of the magnetic head. If the data on the intercept p of the three-dimensional information is used, the two-dimensional information (projection amount with respect to the drum peripheral surface) as shown in FIG. 14 is obtained, and if the data is appropriately processed by the computer, the three-dimensional information shown in FIG. A stereoscopic image is obtained.

Since the linear beam has a length (5 to 6 mm) sufficient to cover the height h in FIG. 13, three-dimensional information can be obtained simultaneously for all magnetic heads mounted on the middle drum 16. .

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example of a magnetic head position measuring device according to the present invention will be described in detail with reference to the drawings. First, the principle of measuring the magnetic head position will be described with reference to FIG.

In the schematic configuration diagram of the magnetic head position measuring apparatus shown in FIG. 1, a light beam LA1 emitted from a laser diode 1 which is a light emitting element is irradiated onto a magnetic head 2 while being condensed by an objective lens 4. The reflected light reflected by the magnetic head 2 is condensed by the condenser lens 5 and is received by the position detecting element (for example, a two-dimensional position detecting sensor such as PDS) 3 to detect the position of the magnetic head 2.

The laser irradiation system and the light receiving system are the middle drum 1
6 is arranged in a plane parallel to the rotating surface, and the incident angle of the light beam LA1 and the reflection angle of the reflected light beam LA2 are equal to each other with reference to the magnetic head whose protrusion amount is ½ of the specified value. Will be placed.

That is, with respect to the extension line V extending from the rotation center of the middle drum 16 through the magnetic head 2, the extension line V and the rotation locus W of the magnetic head 2 having a protrusion amount of 1/2 are formed. The irradiation system and the light receiving system are arranged so as to form an optical axis on a straight line passing through the intersection JW and forming an angle of 45 degrees with the extension line V.

Positions J1 and J2 before and after the reference position JW
The light beam LA2 reflected by the above forms light source images I1 and I2 on the light receiving surface of the position detecting element 3, and the formation position of the light source image is displaced by that amount.

At this time, the light source images I1 and I2, the triangle ΔI1I2O formed by the principal point O of the condenser lens 5, and the position J
1 and J2, which is similar to the triangle ΔJ1J2O formed by the principal point O of the condenser lens 5, the distance from the position detection element 3 to the principal point O of the condenser lens 5 is E1, and the principal point of the condenser lens 5 is E1. When the distance from O to the magnetic head 2 is E2, F2 = (E1 / E2) × F1 ... (2) F1 = J1-J2 ... (3) F2 = I1-I2 ... The relational expression (4) holds.

Here, when the protrusion amount of the magnetic head 2 is set to δR, it can be expressed by F1 = 2 ^1/2 δR (5), so that it is substituted into the equation (2) and F2 = ( The relational expression of (E1 / E2) × 2 ^1/2 δR (6) can be obtained.

As a result, the detection result S0 of the position detecting element 3 is obtained.
The protrusion amount δR for each magnetic head 2 is detected based on
The focal length of the condenser lens 5 is selected to a desired value and the distance E1 is set.
If E2 and E2 are selected, the measurement accuracy can be improved.

The light beam LA1 is an elongated linear beam in which a linear spot as shown in FIG. 2 is formed,
The length h is at least the height w of the magnetic head shown in FIG.
The length is selected to cover h (thickness of ferrite core). In this example, the length is selected to be h or more so as to cover all of the plurality of magnetic heads attached to the middle drum 16 as shown in FIG.

A two-dimensional element is used as the position detecting element 3 as the light beam LA1 becomes a linear beam. As a two-dimensional element, a two-dimensional CCD or a two-dimensional PSD (position
A sensing / detector) array or the like is used, and the size thereof may be, for example, about 1/2 inch.

The relationship between the magnetic head 2 and the linear beam with which it is irradiated will be described with reference to FIG. In the magnetic head 2 shown in the figure, 80 and 81 are ferrite cores and 8
2, 83 is a glass filler, and g is a gap. In the figure, for convenience of description, the linear beam LA1 is applied to the magnetic head 2 from the front, but in reality, the linear beam LA1 is applied from an oblique direction of 45 ° as shown in FIG.

Since the middle drum 16 is rotating at a predetermined speed, if it is assumed that it is rotating counterclockwise now, the linear beam LA1 will scan in the direction a, so a certain time t1 will be considered. Then, the linear beam L at this time
A1 illuminates the surface S, and the data obtained by the position detection element 3 at that time is the amount of protrusion on the surface S in the b direction and the w direction.

Since the data (projection amount) in the b and w directions is obtained every unit time, if this round-slice scanning is continuously performed in the width direction w of the magnetic head, three-dimensional information about the projection amount of the magnetic head is obtained. Is obtained. When the data about the segment p out of the three-dimensional information is used, the two-dimensional information as shown in FIG. 14 (the amount of protrusion at the segment p with respect to the drum peripheral surface) is obtained. 6 stereoscopic images are obtained.

FIG. 4 shows the information processing means 10 provided in the measuring device for performing this two-dimensional display or three-dimensional display.
The data detected by the position detection element 3 is 0, and the data obtained at every predetermined time ti is stored in the RAM 60 for data storage via the CPU 50 which is a processing unit.

When it is desired to know the protrusion amount of the magnetic head from only the data on the predetermined segment p shown in FIG. A two-dimensional display as shown is possible. It is also possible to print out using the printer 70.

When computer processing is performed based on the three-dimensional information stored in the RAM 60, a stereoscopic image near the magnetic head attachment as shown in FIG. 5 or 6 is obtained. It can be seen that a pair of magnetic heads are arranged within the peripheral surface of the drum, and that the uneven wear state of the magnetic heads can be easily grasped.

Here, in the case of the magnetic head on the right side in FIG. 5 or 6, the "constriction" in the central portion is severe, but this is due to the influence of the fillers 82 and 83 shown in FIG. I think that the. This is because the fillers 82 and 83 and the ferrite cores 80 and 81 have different light reflectances.

Since the linear beam LA1 has a length (5 to 6 mm) sufficient to cover the height h in FIG. 13, three-dimensional information can be obtained simultaneously for all magnetic heads mounted on the middle drum 16. To be All of these three-dimensional information can be obtained in principle by rotating the middle drum 16 once, but in reality, the final three-dimensional information is obtained by rotating a predetermined number in consideration of the resolution of the position detecting element 3. I try to get the original information.

Next, a specific example of the magnetic head position measuring device will be described with reference to FIG. As shown in FIG. 8, this magnetic head position measuring device is configured to be attachable to the rotary magnetic head device, and is specifically used by being attached to the drum support 12 of the rotary drum device 7.

The magnetic head position measuring device will be described with reference to FIGS. 7 to 9. This measuring device has a V-shaped support arm portion a. As shown in FIG. 9, the support arm portion a is attached and fixed to a part of the upper surface of the drum support 12 with a fixing screw 30.

The optical block portion c is attached to the lower surface of the front end portion of the support arm portion a via an attachment member 54 provided as required as shown in FIGS.
The optical block section c is configured so that it can store the laser irradiation system and the light receiving system shown in FIG. 1 while maintaining a predetermined angle, and details thereof will be described later with reference to FIG.

As shown in FIG. 9, a positioning block portion d is provided on the side of the optical block portion c so that the optical block portion c always faces the intermediate drum 16 at a predetermined distance. The abutting portion 32 provided on the positioning block portion d is attached to the lower drum (which is a fixed drum that does not rotate) 1
By making contact with the outer peripheral surface of No. 4, the relative positional relationship between the optical block portion c and the inner drum 16 is regulated so that it is always as designed.

In this embodiment, as shown in FIG. 7, a rotating roller portion e constituting a rotation driving means is further provided at the center of the supporting arm portion a. The rotating roller portion e is means for externally applying a rotational driving force so that the drum 16 rotates at a predetermined rotation speed during the measurement of the magnetic head position.

The rotating roller portion e has a motor 302, and a motor rotating shaft (not shown) pulled out from the lower side thereof.
A roller 305 having a predetermined diameter is attached to the motor 302
An arm attachment portion 304 is formed between the roller 305 and the roller 305, and a tip end portion of the L-shaped attachment arm 301 extending from the arm attachment portion 304 is rotatably attached and fixed to a central portion of the support arm portion a by a fixing screw 9. To be done. Figure 8
At 303, the motor 3 is attached to the arm attachment portion 304.
02 is a joint screw for supporting the bearing.

Roller 30 mounted on motor 302
5 has a positional relationship selected so as to be in rolling contact with the peripheral surface of the intermediate drum 16 as shown in FIGS.
Is transmitted to the intermediate drum 16.
Since the peripheral surface of the middle drum 16 is normally hidden by the outer peripheral surface of the upper drum 18, the magnetic head position is measured as shown in FIGS.
It is used with the upper drum removed as shown in.

At this time, the intermediate drum 16 has a predetermined rotation speed (this rotation speed is preferably a low-speed rotation speed as described later).
The rotational speed of the motor 302, the diameter of the roller 305, and the like are appropriately selected in order to be driven by. During the measurement of the magnetic head, the medium drum 16 is driven to rotate at a low speed, so that the processing means (A / D converter, etc.) used in the measuring apparatus can be used at a slow processing speed to reduce the cost of the measuring apparatus itself. This is because

In order to drive the intermediate drum 16 via the roller 305, it is necessary to roll the roller 305 with a proper pressure.

FIG. 10 shows an example of the optical block section c.
The optical block portion c is a base member 54 that is a mounting member.
Is a mechanism for holding a plurality of optical components such as a laser light source.

The optical block portion c is a laser diode block 70 attached to a part of the lower end of the base member 54.
The laser diode 1, the diaphragm 74 and the objective lens 4 are held by the lens block 72 and the base member 54.
The two-dimensional position detecting element 3 is held by the CCD block 76 attached to the upper end of the. The reflected light beam (linear beam) LA2 condensed by the condenser lens 5 is reflected at a right angle by the mirror 78 and is guided to the position detection element 3.

As is clear from the above equation (6), the detection accuracy can be improved by increasing the distance E1 from the condenser lens 5 to the position detecting element 3. However, as in this embodiment, the optical path is perpendicular. If it is formed by bending, the space E can be effectively used to increase the distance E1 and the measurement accuracy can be improved accordingly.

The above-described mirror 78 is held against a through hole for forming the optical path of the reflected light beam LA2 formed on the base member 54 by a predetermined stop plate 80 (see FIG. 7) from the back side of the through hole. .

In the above-described magnetic head position detecting device, the protrusion amount of the magnetic head can be detected by processing the output signal of the position detecting element 3 by the information processing means 100 shown in FIG. The amount of eccentricity (circular deviation) is also detected at the same time.

In the example of FIG. 8, the position of the magnetic head is measured while the rotating roller portion e is provided and the middle drum 16 is driven at a low speed. However, such a rotating roller portion e is not provided, and the same as in the conventional case. The position of the magnetic head may be measured in a constant speed rotation state determined by the specifications of the video tape recorder.

The length of the linear beam may be at least the height of the magnetic head. Even with this length, measurement is performed with the position of the linear beam fixed for the magnetic head groups in the same plane. This is because there are some merits as they can. This is because conventionally, even with a group of magnetic heads lying in the same plane, it is necessary to slide and measure at least the height of the magnetic heads. The video tape recorder to be measured is not limited to this example.

[0056]

As described above, according to the present invention, the linear beam is used for measuring the position of the magnetic head, and
The position detecting element also uses a two-dimensional element.

According to this, since the three-dimensional information of the magnetic head can be obtained while the position of the light emitting element is fixed, the measuring apparatus itself can be greatly simplified, the cost can be reduced, and the length of the linear beam can be increased. If the height is appropriately selected, there is a merit of being able to measure the positions of all the magnetic heads mounted on the drum with the light emitting element and the two-dimensional position detecting element fixed.

Therefore, the present invention is extremely suitable for application to a commercial video tape recorder having strict recording and reproducing characteristics.

[Brief description of drawings]

FIG. 1 is a principle diagram for measuring the position of a magnetic head according to the present invention.

FIG. 2 is a diagram showing a beam shape emitted from a light emitting element.

FIG. 3 is a diagram showing a relationship between a magnetic head and a linear beam.

FIG. 4 is a block diagram showing an example of an information processing means provided in the measuring device.

FIG. 5 is a three-dimensional view of a magnetic head showing a position measurement result.

FIG. 6 is a three-dimensional view of a magnetic head showing a position measurement result.

FIG. 7 is a perspective view showing a state in which the magnetic head position measuring device according to the present invention is mounted on a rotary magnetic head device.

FIG. 8 is a perspective view showing a state before mounting the magnetic head position measuring device.

9 is a top view of FIG. 7. FIG.

FIG. 10 is a cross-sectional view showing a main part of an optical block section.

FIG. 11 is a cross-sectional view of a rotary drum device.

FIG. 12 is a plan view of a middle drum.

FIG. 13 is a development view of a middle drum.

FIG. 14 is a diagram showing a measurement result of a head position.

[Explanation of symbols]

 2, 2A to 2D Magnetic head 1 Light emitting element that emits linear beam 3 Two-dimensional position detection element 16 Middle drum a Support arm portion c Optical block portion d Positioning block portion e Rotation control means (rotating roller portion)

Claims (4)

[Claims] 1. A magnetic head position in which the position of the magnetic head with respect to the drum is measured by irradiating the magnetic head mounted on the drum with light from a light emitting element and receiving the reflected light by a position detecting element. In the measuring apparatus, a linear beam is used as the light from the light emitting element, and a two-dimensional element is used as the position detecting element. 2. The magnetic head position measuring device according to claim 1, wherein the linear beam is selected so as to include at least a width in a height direction of a magnetic head attached to the drum. 3. The magnetic head position measuring device according to claim 1, wherein the linear beam is selected to have a length that can simultaneously cover all of the plurality of magnetic heads attached to the drum. 4. A two-dimensional CC as the position detecting element
The magnetic head position measuring device according to claim 1, wherein a D sensor is used.