JPH0612634A - Device for measuring magnetic head position - Google Patents

Abstract

PURPOSE:To measure the positions of the magnetic heads even when the heights of the magnetic heads are different by holding an optical block so as to be moved along the rotary shaft of a rotary drum and optically measuring the projecting amounts of the magnetic heads. CONSTITUTION:Optical system moving mechanisms 40 to 64 are held on specified positions by holding mechanisms 30, 32, 33 and 34 and when an optical system holding member 54 is moved along the rotary shaft of a rotary drum 16 by these mechanisms 40 to 64, the head positions are measured by changing the position of the holding member 54 even when the heights of the magnetic heads are different. Also, by freely attaching and detaching the optical system moving mechanisms 40 to 64 to and from the drum supporting member 12 of the rotary drum 16 the head positions can be measured easily attaching them.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of the Invention Conventional Technology Problem to be Solved by the Invention (FIG. 17) Means for Solving the Problem (FIG. 2, FIG. 4, FIG. 8 and FIG. 1)
1) Action (FIGS. 2, 4, 8 and 11) Example (1) Measuring principle (FIG. 1) (2) Magnetic head position measuring jig (FIGS. 2 to 6) (3) Optical system moving mechanism (FIGS. 2, 3 and 7) (4) Optical block (FIGS. 2, 3, 8-10) (5) Positioning mechanism (FIGS. 4 and 11) (6) Projection amount detection circuit (FIG. 12) (FIG. 16) (7) Effect of the embodiment (8) Other embodiment Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head position measuring device, which can be applied to, for example, measuring the amount of protrusion and wear of a rotating magnetic head of a video tape recorder.

[0003]

2. Description of the Related Art Conventionally, in a video tape recorder of this type, the magnetic head is slidably contacted with the magnetic tape while the magnetic head is projected from the outer peripheral surface of the rotary drum by a predetermined amount. Without damaging
It is designed so that recording and reproduction can be surely performed.

Therefore, at the time of assembly, in this type of video tape recorder, the protrusion amount of the magnetic head is measured by using a dial gauge or the like, and the protrusion amount is adjusted.

In addition, in this type of video tape recorder, not only the amount of protrusion but also the electromagnetic conversion characteristics change due to wear of the magnetic head after long-term use.

Therefore, in this type of video tape recorder, the amount of wear is detected by periodically measuring the amount of protrusion, and the magnetic head is replaced as necessary.

[0007]

However, the conventional measuring method still has a problem in practical use. That is, in the conventional measuring method, the probe is brought into contact with the magnetic head to measure the amount of protrusion, and when the probe is worn, the measurement accuracy deteriorates accordingly. In addition, the probe may damage the magnetic head.

As one method for solving this problem, a method of detecting the position of the magnetic head by using an optical method can be considered (Japanese Patent Laid-Open No. 62-158616).

In the case of this method, it is possible to solve this kind of problem because the measurement can be performed without contact.

However, as shown in FIG. 17, in this type of video tape recorder, a plurality of magnetic heads are mounted on a rotary drum, and the magnetic heads are located at different positions in the axial direction of the rotary drum (that is, in the drum axial direction). It is attached when the height is different).

Therefore, when the optical method is applied to this type of video tape recorder, there is a problem that it is difficult to easily measure the protrusion amount for all magnetic heads.

The present invention has been made in consideration of the above points, and it is possible to easily measure the amount of protrusion and the amount of wear even if magnetic heads are attached to different heights in a non-contact manner. The head position measuring device is proposed.

[0013]

In order to solve the above problems, in the first invention, the magnetic heads 2A to 2D mounted on the rotary drum 16 are irradiated with the light beam LA1 and the magnetic heads 2A to 2D are also irradiated. The reflected light beam LA2 of the light beam LA1 obtained from
Based on the detection result S0 of A2, the magnetic heads 2A to 2D
In the magnetic head position detecting device 10 for detecting the position of the
4, the reflected light beam receiving optical systems 3 and 5 for receiving the reflected light beam LA2, and the optical system holding member 54 for holding the light beam irradiation optical systems 1 and 4 and the reflected light beam receiving optical systems 3 and 5.
An optical system moving mechanism 40 to 64 for moving the optical system holding member 54 along the rotation axis of the rotary drum 16, and a holding mechanism 30 for holding the optical system moving mechanism 40 to 64 at a predetermined position.
32, 33, and 34.

Further, in the second invention, the light beam irradiation optical systems 1 and 4 and / or the reflected light beam receiving optical systems 3 and 5 are provided.
Is the optical path from the magnetic heads 2A to 2D to the light source 1 that emits the light beam LA1 and / or the optical path from the magnetic heads 2A to 2D to the light receiving element 5 that receives the reflected light beam LA2, in the rotation axis direction of the rotating drum 16. It is formed by bending it at a right angle so that it extends substantially in parallel.

Further, in the third invention, the holding mechanism 3
Reference numerals 0, 32, 33, and 34 detachably hold the optical system moving mechanisms 40 to 64.

Further, in the fourth invention, the holding mechanism 3
Reference numerals 0, 32, 33, and 34 detachably hold the optical system moving mechanisms 40 to 64 with respect to the drum support member 12 of the rotary drum 16.

Further, in the fifth invention, the holding mechanism 3
Reference numerals 0, 32, 33, and 34 each have a predetermined positioning mechanism 38, and the positioning mechanism 38, with respect to the fixed drum 14 forming the rotary drum 16, has the light beam irradiation optical systems 1 and 4 and the reflected light beam receiving optical system. Hold the systems 3, 5 in place.

[0018]

The holding mechanisms 30, 32, 33 and 34 hold the optical system moving mechanisms 40 to 64 at predetermined positions, and the optical system moving mechanisms 40 to 64 move the optical system holding member 54 along the rotary shaft of the rotary drum 16. If the magnetic heads 2A to 2D have different heights, the head position can be measured by displacing the position of the optical system holding member 54 for each of the magnetic heads 2A to 2D.

At this time, the rotating drum 16 rotates through the optical path from the magnetic heads 2A to 2D to the light source 1 for emitting the light beam LA1 and the optical path from the magnetic heads 2A to 2D to the light receiving element 5 for receiving the reflected light beam LA2. If it is formed by bending at a right angle to the axial direction, the space around the rotary drum 16 can be effectively utilized by that much and the measurement accuracy can be improved.

On the other hand, if the optical system moving mechanisms 40 to 64 are detachably held, the head position of the desired rotating drum can be measured.

At this time, if the optical system moving mechanisms 40 to 64 are detachably held with respect to the drum supporting member 12 of the rotary drum 16, the head position can be measured by simply attaching them.

With respect to the fixed drum 14 forming the rotary drum 6 by the positioning mechanism 38, the light beam irradiation optical systems 1, 4 are provided.
If the reflected light beam receiving optical systems 3 and 5 are held at predetermined positions, reproducible measurement results can be obtained.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Measuring Principle FIG. 1 shows a schematic structure of a magnetic head position measuring device. A light beam LA1 emitted from a laser diode 1 is reflected by a magnetic head 2 and received by a position detecting element 3. The position of the magnetic head 2 is detected.

That is, the magnetic head position measuring apparatus forms an irradiation optical system with the laser diode 1 and the objective lens 4, and this irradiation optical system collects the light beam LA1 emitted from the laser diode 1 with the objective lens 4. As a result, a light source image of the laser diode 1 is formed on the magnetic head 2.

On the other hand, the magnetic head position measuring device is
A light receiving optical system is formed by the position detecting element 3 and the condensing lens 5, and this light receiving optical system condenses the reflected light beam LA2 reflected by the magnetic head 2 by the condensing lens 5, whereby the position detecting element 3 A light source image of the laser diode 1 is formed on the light receiving surface.

The irradiation optical system and the light receiving optical system are arranged in a plane perpendicular to the rotation center axis of the rotating drum 6, and the light beam L is based on the magnetic head whose protrusion amount is 1/2 of the specified value.
It is arranged so that the incident angle of A1 and the reflection angle of the reflected light beam LA2 are equal.

That is, in the magnetic head position measuring device, with respect to the extension line V extending from the rotation center of the rotary drum 6 through the magnetic head 2, the extension line V and the protrusion of the magnetic head have a rotation locus of 1/2. Pass the intersection J _W formed by W and
Further, the irradiation optical system and the light receiving optical system are arranged so that the optical axis is formed on a straight line forming an angle of 45 degrees with the extension line V.

When the projection amount of the magnetic head 2 changes with the irradiation optical system and the light receiving optical system thus arranged, the position of the light source image on the position detecting element 3 is displaced.

That is, the light beams LA2 reflected at the positions J1 and J2 before and after the reference position J _W form the light source images I1 and I2 on the light receiving surface of the light receiving 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 J1.
And J2, the triangle ΔJ formed by the principal point O of the condenser lens 5
By analogy with 1J2O, if the distance from the light receiving element 3 to the principal point O of the condenser lens 5 is E1 and the distance from the principal point O of the condenser lens 5 to the magnetic head 2 is E2,

[Equation 1]

[Equation 2]

[Equation 3] The relational expression of is established.

If the amount of protrusion of the magnetic head 2 is δR,

[Equation 4] By substituting into equation (1),

[Equation 5] The relational expression of can be obtained.

As a result, the detection result S0 of the position detecting element 3 is obtained.
It is found that the protrusion amount δR of the magnetic head 2 can be detected based on the above, and the measurement accuracy can be improved by selecting the focal length of the condenser lens 5 to a desired value and selecting the distances E1 and E2. I understand.

Thus, in this embodiment, the protrusion amount detection circuit 9 processes the detection result S0 of the position detecting element 3 to detect the protrusion amount of the magnetic head 2 for each magnetic head.

(2) Magnetic head position measuring jig In FIG. 2, reference numeral 10 indicates a magnetic head position measuring jig as a whole, which is attached to the drum support 12 of the rotary head device 7 as shown in FIGS. 3 and 4. use.

Incidentally, as shown in FIG. 5, the rotary head device 7 is formed by coaxially holding the lower drum 14, the middle drum 16 and the upper drum 18, and the lower drum 14 is fixedly held by the chassis. .

Further, the lower drum 14 supports a drum shaft 22 via a bearing 20, and the drum shaft 22 supports the middle drum 16.

The drum support 12 fixes the upper drum 18 to the lower drum 14, so that the upper drum 18 and the lower drum 14 in the rotary drum device 7 are connected to the magnetic tape 2 by the magnetic tape 2.
The magnetic drum 2 (2A, 2B) mounted on the intermediate drum 16 is driven by rotating the intermediate drum 16 while guiding the magnetic head 4.
Are brought into sliding contact with the magnetic tape 24.

Here, as shown in FIG. 6, in the middle drum 22, by using the screws 26, four magnetic heads 4A to 4A.
It is designed to be equipped with 4B. As a result, in the rotary drum device 7, the four magnetic heads 4A to 4A are
The magnetic tape 24 is scanned at B, and recording tracks are sequentially formed obliquely.

In this drum support 12, a screw hole 12A is formed on the upper side (FIG. 2), and a screw (not shown) formed at the tip of the knob 30 is passed through the through hole of the arm 32 to form this screw. By screwing into the hole 12A, the knob 30 can be operated to attach the magnetic head position measuring jig 10 to the rotary head device 7.

The arm 32 has a rotating shaft 33 formed at its tip end, which rotatably supports the arm 34, and a torsion coil spring 35 attached to the rotating shaft 33 (FIG. 4).
The arm 34 is urged in the direction of the rotary head device 7 as indicated by the arrow a.

The arm 34 comprises an optical block 36 forming an optical system of the magnetic head position measuring device, an optical system moving mechanism for moving the optical block 36 along the rotation axis of the rotary head device 7, and an optical block 36. Is mounted on the rotary head device 7, and thereby a holding mechanism for the magnetic head position measuring jig 10 is formed together with the knob 30, the arm 32, the rotating shaft 33 and the torsion coil spring 36.

(3) Optical system moving mechanism The arm 34 vertically stands and holds two guide rods 40 and 42 in parallel with the rotation axis of the rotary head device 7, and the guide rods 40 and 42 serve as an optical system block. Guide the moving direction of 36.

Further, as shown in FIG. 7, the arm 34 holds the stepping motor 44 with a screw 46 so that the rotation shaft 48 of the stepping motor 44 is parallel to the guide rods 40 and 42. The drive shaft 52 is connected via the joint 50.

The drive shaft 52 has an M3 fine thread on its tip end so that it can rotate in a desired rotation direction by driving the stepping motor 44.

On the other hand, in the base member 54 of the optical block 36, in addition to the through holes (FIGS. 2 and 4) through which the guide rods 40 and 42 pass, a through hole 56 through which the drive shaft 52 passes is formed. , A tap plate 58 that meshes with the drive shaft 52
Is fastened to the upper end surface of the through hole 56 with a screw 60.

As a result, the base member 54 is fixed to the drive shaft 52.
When it rotates, it is guided by the guide rods 40 and 42 to move in the vertical direction as shown by the arrow b. Therefore, in the magnetic head position measuring device, the stepping motor 44 is driven to drive the optical block 36 and the optical block 36. The positioning mechanism 38 can be moved along the rotation axis of the rotary head device 7.

A tap plate 64 is screwed onto the drive shaft 52 so as to press the corrugated spring washer 62 above the tap plate 58.
It is designed to be restricted by 6.

As a result, in the magnetic head position measuring jig 10, rattling due to the rotation of the drive shaft 52 is prevented by using the spreading force of the wave spring washer 62, and the measurement by this rattling is performed. It is designed to prevent deterioration of accuracy.

The pin 66 is held so as to stand upright from the upper end surface of the base member 54, and the upper end position is adjusted so as to project from the upper end surface of the base member 54 by a predetermined length.

On the other hand, in the joint 50, the pin 68 is arranged so as to be orthogonal to the drive shaft, which drives the stepping motor 44 to move the base member 54 upward to a predetermined position. The rotating pin 68 hits the pin 66.

As a result, in the magnetic head position measuring jig 10, the base member 54 is held so as not to move upward more than a predetermined position, and the upper position is set by the pin 66, so that the measurement can be performed with a simple structure. The reference position for is set so that it can be set.

(4) Optical Block The optical block 36 holds an optical component such as a laser light source on the base member 54, thereby forming an optical system of this magnetic head position measuring jig.

That is, as shown in FIG. 8, the optical block 36 holds the laser diode 1, the diaphragm 74, and the objective lens 4 on the base member 54 with the laser diode block 70 and the lens block 72, and the position through the PSD block 76. The detection element 3 is held by the base member 54.

At this time, the optical block 36 reflects the reflected light beam LA2 condensed by the condenser lens 5 at a right angle by the mirror 78, so that the reflected light beam LA2 is parallel along the rotation axis of the rotary head device 7. To the position detection element 3.

That is, as described above with respect to the expression (5), the detection accuracy can be improved by increasing the distance E1 from the condenser lens 5 to the position detecting element 3.

However, in the video tape recorder, a magnetic tape running system such as a guide post is formed around the rotary head device 7 so that the rotary head device 7 can be operated.
There is a small space around and the distance E1 cannot be increased if the reflected light beam LA2 is linearly guided to the position detecting element 3.

However, if the optical path is formed by bending it at a right angle as in this embodiment, the space E can be effectively utilized to increase the distance E1 and the measurement accuracy can be improved.

The mirror 78 has a through hole for forming the optical path of the reflected light beam LA2 formed in the base member 54, and a mirror 78 is provided from the back side of the through hole with a predetermined stop plate 80 (FIGS. 2 and 3). By fixing the stopper plate 80 with a screw 82, the fixing plate 80 is fixed to the base member 54.

On the other hand, as shown in FIG. 9, in the objective lens 4, after being inserted into the through hole of the base member 54, the objective lens 4 is held so as to be sandwiched by the base member 54 and the lens block 72 together with the diaphragm 74. Is held at a predetermined position on the base member 54.

At this time, the lens block 72 is adapted to be screwed by a screw 88 after the parallel pin 84 is inserted into the hole 86 of the base member 54 for positioning.

On the other hand, the laser diode 1 is inserted into the laser diode block 70, and then the laser diode pressing plate 90 is fixed to the laser diode block 70 from the rear side with the screw 89, thereby fixing to the laser diode block 70. To be done.

The laser diode block 70 is fixed to the base member 54 through the lens block 72 by inserting a screw 92 into the through hole 94 and screwing the lens block 72.

The through hole 94 is formed as an elongated hole extending in the vertical direction, whereby the laser diode block 7 is formed.
The position 0 can be adjusted in the vertical direction when screwed with the screw 92.

In order to simplify this position adjusting work, the lens block 72 is screwed to the laser diode adjusting plate 98 with the screw 96 using the screw hole formed at the upper end.

The laser diode adjusting plate 98 has a through hole 1
00 and a screw hole 102 are formed, and the laser diode block 70 corresponds to the through hole 100 and has a screw hole 104.
Are formed.

As a result, the laser diode block 70
Screw the screw 106 through the through hole 100 and
After being screwed in 4, the screw 106 can be further tightened to move upward, whereas the screw 108 screwed in the screw hole 102 can be further tightened to increase the protrusion amount of the screw 108 from the laser diode adjusting plate 98. It is made possible to move downward.

Thus, in the magnetic head position adjusting jig 10, the mounting position of the laser diode 1 can be adjusted by a simple adjusting mechanism.

As shown in FIG. 10, a PSD block 76
Is fixed to the base member 54 with a screw 112 with the parallel pin 110 facing.

Further, the PSD block 76 has a groove formed on the upper end surface thereof, and after the position detecting element 3 is inserted into this groove,
The position detecting element 3 is held by screwing the pressing plate 114 with screws 116 from the back side.

The pressing plate 11 is formed in a U-shaped cross section so as to block the extending direction of the groove, and the screw 118 is screwed into the screw holes formed on both side plates to adjust the protruding amount of the screw 118. Thereby, the screws 118 are pressed against both side surfaces of the position detecting element 3, whereby the position detecting element 3 can be positioned by a simple adjusting mechanism.

(5) Positioning Mechanism As shown in FIG. 11, the positioning mechanism 38 adjusts the amount of protrusion of the positioning pin 120 (FIG. 4) protruding toward the rotary head device 7 side so that the rotary head device 7 can be optically moved. The distance to the block 36 is adjusted, thereby positioning the optical block 36.

That is, as shown by the arrow a, the position of the positioning pin 120 is such that the arm 32 is biased toward the rotary head device 7 side by the torsion coil spring 36, so that the tip of the arm 32 contacts the lower drum of the rotary head device 7. In this way, the amount of protrusion is adjusted to adjust the distance from the rotary head device 7 to the optical block 36.

Here, the positioning mechanism 38 is configured to fix the positioning block 122 to the base member 54 with the screw 124, and at this time, the groove 1 opening to the base member 54 side.
The positioning shaft 126 is inserted into 25 and held.

The positioning shaft 126 is formed with a taper after the intermediate portion is threaded so that a fall-preventing collar is formed between the tapered portion and the threaded portion. Has been done.

The positioning shaft 126 is configured such that the threaded portion is screwed into the screw hole of the positioning shaft holding plate 128, and the positioning shaft holding plate 128 is fixed to the positioning block 122 with the screw 130.

Further, the positioning shaft 126 is fixed at the set screw 134 by inserting the tip end portion extending from the threaded portion into the through hole of the knob 132, whereby the knob 132 can be freely rotated by operating the knob 132. ing.

Accordingly, the positioning shaft 126 has the knob 1
With the rotation of 32, it is guided by the screw hole of the positioning shaft holding plate 128 and moves along the groove 125 as shown by an arrow d.

The positioning block 122 has a through hole formed at a position where the tapered portion of the positioning shaft 126 is located when the positioning shaft 126 is held, so as to be orthogonal to the groove 125, and the positioning pin is provided in the through hole. Insert and hold 120.

At this time, the positioning mechanism 38 screws the retaining plate 134 to the positioning block 122 with the screw 136 in order to prevent the positioning pin 120 from falling off.

Thus, in the positioning pin 120,
When the positioning shaft 126 is moved along the groove 125, it is pushed out by the taper portion of the positioning shaft 126, whereby the magnetic head position measurement result 10 can be easily positioned by rotating the knob 132.

(6) Projection amount detection circuit In the magnetic head position detection device, the projection amount detection circuit 9 shown in FIG. 12 processes the output signal S0 of the position detection element 3 to detect the projection amount of the magnetic head. .

At this time, the protrusion amount detection circuit 9 also detects the amount of eccentricity (hereinafter referred to as "circular deviation") on the outer periphery of the middle drum.

That is, in the protrusion amount detection circuit 9, the rotary drum pulse generator 140 generates the rotary drum pulse PG whose signal level rises in the rotation cycle of the middle drum 16, and outputs it to the clock counter 142.

The rotating drum frequency generator 144 generates a rotating frequency signal FG whose signal level is switched when the middle drum 16 rotates by a predetermined angle, and outputs it to the clock counter 142.

The clock counter 142 resets the count value based on the rotating drum pulse PG and counts the rotating frequency signal FG. As a result, when the middle drum 16 makes one rotation, the signal level is switched and the middle cycle 16 When the drum 16 rotates a predetermined angle, a rotation angle signal whose signal level is switched is generated.

The timing pulse generating circuit 146 controls the control circuit 1 based on the rotation period signal and the rotation angle signal.
A sampling pulse which rises at a predetermined timing is generated based on a control signal output from 48, and this sampling pulse is sampled and held by a sample hold circuit (SH) 15
The output signal S0 of the position detecting element 3 is sampled and held.

As a result, the protrusion amount detection circuit 9 detects the position of the outer peripheral surface of the intermediate drum 16 at every predetermined angle to detect the circumferential deviation.

Further, the protrusion amount detection circuit 9 similarly obtains the position detection result of the magnetic head, and subtracts the position detection result of the outer peripheral surface of the middle drum 18 from this position detection result to detect the protrusion amount of the magnetic head. .

That is, as shown in FIG. 13, the output signal S
At 0, the signal level changes in synchronization with the rotation of the middle drum 18.

Therefore, in this embodiment, the output signal S0 is sampled and held on the basis of the rotation period signal and the rotation angle signal generated from the rotation drum pulse PG and the rotation frequency signal FG, so that the irradiation position of the light beam LA1 can be obtained. Output signal S0 at the timing when the magnetic head crosses the
Signal level U1 of the magnetic head, 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 the 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 the following expression is obtained.

[Equation 6] Then, the magnetic head projection amount Y is detected.

Therefore, in the control circuit 148, the sample and hold result of the sample and hold circuit 150 is fetched through the analog digital conversion circuit (AD) 152, and at this time, the stepping motor 44 is driven through the motor drive section 154. By driving, the position of the optical block 36 is adjusted according to the height of the magnetic head to be measured.

That is, in the control circuit 148, the operation mode is switched in response to the operation of a predetermined operator, and when the operator for starting the measurement is pressed, the processing procedure of FIG. 14 or 15 is executed.

Here, in the control circuit 148, when the operation sensor for starting measurement is set in the circumferential shake measurement mode and the measurement start operator is pressed, the operation moves from step SP1 to step SP2, where a control signal is output to the motor drive circuit 154. By doing so, the stepping motor 44 is driven to move the optical block 36 upward.

At this time, in the control circuit 148, the stepping motor 44 is rotationally driven until the stepping motor 44 becomes difficult to rotate, whereby the optical block 36 is driven.
Is moved to a reference position determined by the protrusion amount of the pin 66 (FIG. 7).

Then, in step SP3, the control circuit 1
Reference numeral 48 drives the stepping motor 44 to move the optical block 36 downward so that the optical block 36 faces the outer peripheral surface of the intermediate drum 16.

In this state, the control circuit 148 switches the operation of the timing pulse generation circuit 146 in the subsequent step SP4, and thereby outputs a sampling pulse to the sample hold circuit 150 every time the middle drum 16 rotates 22.5 degrees.

As a result, the control circuit 148 sequentially takes in the sample and hold results via the analog digital conversion circuit 152, divides the outer peripheral surface of the middle drum 16 into 16 equal intervals, and sets sample points. The position of the outer peripheral surface is detected for each point.

When the measurement of the outer peripheral surface is completed, the control circuit 148 moves to step SP6 and displays the measurement result on the operation display unit 156.

Here, as shown in FIG. 16, the operation display unit 15
6, the magnetic head and channel selection operators 160 and 162 for selecting the protrusion amount detection result, and the LEDs 164 and 166 for displaying the selection result are arranged.

Further, the operation display unit 156 is provided with an LED 168 indicating the circumferential shake measurement mode and a display unit 170 showing the projection amount and the circumferential shake measurement result. The display unit 170 is a display unit showing the projection amount and the circumferential shake amount. 172 and an LED are arranged at equal angles, and an adjustment instructing unit 174 is arranged so as to correspond to a sampling point of the middle drum 16 and indicates a circumferential shake correction position.

Here, the control circuit 148 determines that
While turning on the LED 168 representing the shake measurement mode,
An average value is detected from the measurement result of each sampling point, and the LED of the adjustment instruction unit 174 is turned on for the sampling point having the largest deviation from this average value.

Further, the control circuit 148 displays this largest deviation on the display unit 172, so that the operator can easily judge whether or not the amount of circumferential shake is below the standard value based on the display on the display unit 172. Has been done.

Further, the control circuit 148 determines that the operator is instructed to make an adjustment instructing unit 174 when the amount of shake is not less than the standard value.
Based on the display of, the adjustment location can be easily confirmed.

Further, when the control circuit 148 drives the display operator 156 in this manner, the control circuit 148 continues to step SP6.
Then, it is determined whether or not the restart operator has been pressed, and if a positive result is obtained here, the process returns to step SP4.

As a result, the operator can immediately confirm the adjustment result by restarting the circumference shake measurement as necessary, and by doing so, repeat the measurement and adjustment work as necessary to easily perform the circumference shake. Can be corrected.

On the other hand, if a negative result is obtained in step SP6, the control circuit 148 moves to step SP7 and determines whether or not the stop operator has been pressed. If a negative result is obtained here, the step is judged. While returning to SP6, if a positive result is obtained here, the process proceeds to step SP8 to complete the measurement of the shake.

Since the optical block 36 can be moved along the rotary shaft of the rotary head device 7 in this way, not only the amount of protrusion of the magnetic head but also the circumferential deviation can be easily detected.

On the other hand, when the measurement start operator is pressed in the protrusion amount measurement mode after adjusting the circumferential deviation, the control circuit 148 shifts from step SP9 to step SP10 (FIG. 15), and With respect to the magnetic head located on the upper side, the optical block 36 is moved to a position facing the magnetic head.

Subsequently, the control circuit 148 proceeds to step SP1.
Then, the control signal is output to the timing pulse generation circuit 146, and the output signal S0 is sampled and held at the timing when the magnetic head crosses the irradiation position of the light beam LA1.

As a result, the control circuit 148 detects, for the uppermost magnetic head, the position of the sliding contact surface of this magnetic head, and then moves to step SP12 to determine whether or not the measurement has been completed for all magnetic heads. to decide.

If a negative result is obtained here, the control circuit 1
Step 48 returns to step SP10, moves the optical block 36 to a position facing the subsequent magnetic head, and then moves to step SP11.

As a result, the control circuit 148 sequentially executes the processing procedure of steps SP10-SP11-SP12-SP10, thereby sequentially moving the position of the optical block 36 for each magnetic head mounted on the middle drum 16. The position of the sliding contact surface is detected.

Therefore, in the magnetic head position measuring device, the position of the sliding contact surface can be automatically detected for the magnetic heads having different heights without adjusting the position of the optical block 36. As a result, the assembling work and the maintenance work can be greatly simplified.

Thus, in the control circuit 148, when the measurement work is completed for all the magnetic heads, a positive result is obtained in step SP12, so that the process proceeds to step SP13 to complete the processing procedure.

Further, when the measurement result is obtained in this way, the control circuit 148 executes the arithmetic processing of the equations (5) and (6) to detect the protrusion amount, and the operation elements 160 and 1
In response to the operation of 62, the projection amount of the magnetic head selected by the operator is displayed on the display unit 172 in units of μm.

(7) Effects of the Embodiments According to the above construction, the stepping motor is driven so that the optical block can be moved along the rotary shaft of the rotary drum device, and the stepping motor is sequentially driven. By processing the output signal S0 of the position detecting element with the magnetic head, the position of the optical block can be adjusted according to the height of the magnetic head to obtain a measurement result. Therefore, even when the height of the magnetic head is different, The amount of protrusion can be detected for each magnetic head,
In addition to this, it is possible to detect a shake in the circumference.

(8) Other Embodiments In the above-mentioned embodiments, the case where the protrusion amount of the magnetic head is detected for the video tape recorder in which the magnetic heads are arranged on the middle drum at angular intervals of 90 degrees has been described.
The present invention is not limited to this, and can be applied to various video tape recorders to measure the amount of protrusion.

Further, in the above-mentioned embodiment, the case where the peripheral shake is measured in addition to the protrusion amount is described, but the present invention is not limited to this, and only the protrusion amount may be measured.

Further, in the above embodiment, the case where the optical path of the light receiving optical system is bent by 90 degrees has been described, but the present invention is not limited to this, and when a sufficient space can be secured,
The optical path may be formed linearly.

Further, in the above-mentioned embodiment, the case where the control circuit drives the stepping motor to automatically measure the protrusion amount is described. However, the present invention is not limited to this, and if necessary, for example, an optical block may be performed. May be manually moved.

Further, in the above-mentioned embodiment, the case where the whole is formed into a jig so as to be detachable from the rotary drum device has been described, but the present invention is not limited to this, and may be integrated into the rotary drum device. . By doing so, it is possible to self-diagnose the wear amount of the magnetic head.

[0124]

As described above, according to the present invention, the optical block is held so as to be movable along the rotary shaft of the rotary drum, and the amount of protrusion of the magnetic head is optically measured by this optical block. Thus, even if the height of the magnetic head is different, the position of the magnetic head can be measured by moving the optical block.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the measurement principle of the present invention.

FIG. 2 is a perspective view showing a magnetic head position measuring jig.

FIG. 3 is a perspective view showing a state of being attached to the rotary drum.

FIG. 4 is a plan view thereof.

FIG. 5 is a cross-sectional view showing a rotary head device.

FIG. 6 is a plan view showing a drum therein.

FIG. 7 is a sectional view for explaining an optical system moving mechanism.

FIG. 8 is a perspective view showing a partial cross section for explaining an optical system.

FIG. 9 is an exploded perspective view showing the periphery of the laser diode.

FIG. 10 is an exploded perspective view showing the periphery of the position detecting element.

FIG. 11 is an exploded perspective view showing the periphery of a positioning pin.

FIG. 12 is a block diagram showing a protrusion amount detection circuit.

FIG. 13 is a signal waveform diagram for explaining the operation.

FIG. 14 is a flow chart used for the description of the measurement of the circumferential shake.

FIG. 15 is a flow chart used for explaining the position measurement of the magnetic head.

FIG. 16 is a plan view showing the display operation unit.

FIG. 17 is a schematic diagram for explaining the case where the heights of the magnetic heads are different.

[Explanation of symbols]

1 ... Laser diode, 2, 2A to 2D ... Magnetic head, 3 ... Position detecting element, 4, 5 ... Lens, 6 ... Rotating drum, 7 ... Rotating head device, 9 ... Projection amount detecting circuit 10 ... Magnetic head position measuring jig, 12 ... Drum support, 16 ... Medium drum, 36 ... Optical block, 38
...... Positioning mechanism, 44 ...... Stepping motor, 14
8 ... Control circuit.

Claims (5)

[Claims] 1. A magnetic head mounted on a rotating drum is irradiated with a light beam, and a reflected light beam of the light beam obtained from the magnetic head is detected, and based on the detection result of the reflected light beam. A magnetic head position detecting device for detecting the position of the magnetic head; a light beam irradiation optical system for irradiating the light beam; a reflected light beam receiving optical system for receiving the reflected light beam; and a light beam irradiation optical system. And an optical system holding member for holding the reflected light beam receiving optical system, an optical system moving mechanism for moving the optical system holding member along the rotation axis of the rotary drum, and holding the optical system moving mechanism at a predetermined position. A magnetic head position measuring device characterized by comprising: 2. The light beam irradiating optical system and / or the reflected light beam receiving optical system includes an optical path from the magnetic head to a light source for emitting the light beam and / or a light receiving device for receiving the reflected light beam from the magnetic head. The optical path to the element,
2. The magnetic head position measuring device according to claim 1, wherein the magnetic head position measuring device is formed by bending the rotary drum at a right angle so as to extend substantially parallel to the rotation axis direction of the rotary drum. 3. The magnetic head position measuring device according to claim 1, wherein the holding mechanism holds the optical system moving mechanism in a detachable manner. 4. The magnetic head position measuring device according to claim 3, wherein the holding mechanism detachably holds the optical system moving mechanism with respect to a drum supporting member of the rotary drum. 5. The holding mechanism has a predetermined positioning mechanism, and the positioning mechanism includes the light beam irradiation optical system and the reflected light beam receiving optical system with respect to a fixed drum forming the rotary drum. The magnetic head position measuring device according to claim 1, 2, 3, or 4, which is held at a predetermined position.