JPH06139537A - Position adjusting device for magnetic head - Google Patents

Abstract

PURPOSE:To prevent the tape edge of a magnetic tape from being impaired by detecting the displacement of a tape width direction based on the differential information between first and second sensors at a tape position detection part and controlling the move of a rotary head in a cylinder rotating axis direction corresponding to a detecting signal. CONSTITUTION:First and second sensors 19 and 22 of a position detection part 17 are provided on the side of a tape entrance, and the detecting outputs of the sensors 19 and 22 are amplified by amplifiers 25 and 26. Outputs from the amplifiers 25 and 26 are inputted to a differential circuit 27, and level difference between the input signals is outputted. On the other hand, first and second sensors 28 and 29 of a tape position detection part 18 are provided on the side of a tape exit, detecting outputs from the sensors are amplified by amplifiers 30 and 31, outputs from the amplifiers 30 and 31 are inputted to a differential circuit 32, and difference between the input signals is outputted. Thus, since the difference is calculated between the first sensors 19 and 28 and the second sensors 22 and 29, exact magnetic tape fluctuating amounts A and B in the width direction with a noise level removed can be calculated and corresponding to these fluctuating amounts, an actuator 37 for dynamic tracking is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position adjusting device for a rotary magnetic head in a magnetic recording / reproducing device such as a VTR.

[0002]

2. Description of the Related Art Conventionally, in a magnetic recording / reproducing apparatus such as a VTR (video tape recorder) and a DAT (digital audio tape recorder), a tape edge of a magnetic tape is mechanically brought into contact with a flange of a post for pulling out the tape. By forcing the magnetic tape to move along the width of the magnetic tape to suppress the fluctuation in the width direction, the magnetic head scans the magnetic tape with high accuracy to form a highly accurate track pattern. However, this method has a problem that the tape edge of the magnetic tape is damaged.

As a method for solving this problem, as disclosed in, for example, Japanese Patent Laid-Open No. 3-125357, light is emitted toward a tape pull-out post at a position where a magnetic tape is pulled out and tape loading is completed. Then
In addition, sensors for receiving the reflected light are provided on both the tape inlet side and the tape outlet side of the rotating drum, and the position in the width direction of the magnetic tape is detected by the change in the output voltage from this sensor. There is a method of correcting the running position of the magnetic tape by controlling the movement of the tape pulling post.

However, even in the method of correcting the running position of the magnetic tape by detecting the position in the width direction of the magnetic tape by the sensor including the light emitting portion and the light receiving portion described above,
The amount of light emitted from the light emitting part changes with temperature and time,
Since the amount of light received by the light receiving unit changes due to changes in the amount of light emitted from the light emitting unit and light from the outside, there is a problem that the position of the magnetic tape cannot be detected with high accuracy.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the drawbacks of the above-mentioned conventional example, and does not damage the tape edge of the magnetic tape, and also changes in the environment such as temperature change and external light. Position of the magnetic tape that can accurately detect the position of the magnetic tape even when a problem occurs, and the magnetic head can scan the magnetic tape with high accuracy to form a highly accurate track pattern. The purpose is to provide a device.

[0006]

SUMMARY OF THE INVENTION A magnetic head position adjusting device of the present invention is a light emitting section which emits light toward a tape edge of a magnetic tape on a tape inlet side and a tape outlet side of a guide cylinder on which a rotary head is mounted. And a first sensor including a light receiving unit that receives reflected light of the light from the light emitting unit,
A second light emitting part that emits light toward the central portion of the tape of the magnetic tape; and a light receiving part that receives light from the light emitting part
And a tape position detecting section each of which is provided with each sensor, and the tape is wound around the guide cylinder of the magnetic tape based on the difference information between the first sensor and the second sensor in each tape position detecting section. It is characterized in that the displacement of the tape width direction in the present portion is detected and the movement of the rotary head in the cylinder rotation axis direction is controlled by the detection signal.

[0007]

According to the above construction, the information from the first sensor includes the influence of the change in the environment along with the variation amount in the width direction of the magnetic tape, and the information from the second sensor in the width direction of the magnetic tape. Since the variation amount is not included, but only the influence due to the change in the environment is included, the difference information between the first sensor and the second sensor is the accurate variation amount in the width direction of the magnetic tape, and the change in the environment. Even in the case of occurrence of, the accurate displacement of the magnetic tape from the reference position in the width direction can be detected.

[0008]

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

FIG. 2 is a plan view showing the outline of the entire tape running system in the loading state of the VTR of this embodiment.

In the VTR of this embodiment, the magnetic tape 1 is pulled out from the cassette 7 by the tape pulling posts 2, 3, 4, 5 and the back tension post 6 and is inclined at a predetermined angle with respect to the cassette surface. Cylinder 8
It is wound at a predetermined angle. In the figure, 9, 10, 11, 1
2 is a fixed guide fixed to the chassis, 13 is a front width erasing head, 14 is an audio / control head, 15
Is an impedance roller, 16 is a pinch roller, and 17 is a capstan. Of the posts 2, 3, 4, 5 for pulling out the tape, 2 and 5 are vertical posts 3, 4, 5.
Is an inclined post.

In this embodiment, tape position detecting portions 18A and 18B are provided on both the tape inlet side and the tape outlet side of the cylinder so as to face the vertical posts 2 and 5 in the loading state and the magnetic tape 1, respectively. is set up.

FIG. 3 is a diagram showing the structure of the tape position detecting section 18A.

In FIG. 3, 19 is a light emitting portion 20 such as an LED which emits light toward the tape edge below the magnetic tape 1.
And a light receiving section 21 such as a phototransistor for detecting the reflected light of the light emitted from the light emitting section 20. Reference numeral 22 denotes a second light emitting portion 23 such as an LED that emits light toward the central portion of the magnetic tape 1 and a light receiving portion 24 such as a phototransistor that detects reflected light from the light emitting portion 23. It is a sensor. The light receiving units 21 and 24 detect a change in the amount of reflected light due to a difference in reflectance of an object that reflects the light from the light emitting unit. That is, since the reflectance is different between the mirror-finished whitish vertical post 2 and the blackish magnetic tape 1, when the magnetic tape 1 fluctuates in the width direction, light is emitted toward the tape edge.
The amount of light reflected from the light emitting unit 20 of the sensor 19 changes, and the light receiving unit 21 detects the amount of fluctuation of the magnetic tape 1 based on the change in the amount of reflected light. For example, when the detection distance between the post and the sensor is constant and the tape edge below the magnetic tape 1 fluctuates above the reference traveling position (measurement center), the amount of reflected light from the vertical post 2 increases, and The detection current in the light receiving section 21 of the sensor 19 becomes large, and when the tape edge moves downward, the amount of light reflected from the vertical post 2 decreases and the detection current in the light receiving section 21 becomes small. On the other hand, since the light emitting portion 23 of the second sensor 22 emits light toward the tape central portion of the magnetic tape 1, even if the magnetic tape 1 varies in the width direction, the amount of light reflected from the light emitting portion 23 is small. It does not change and the amount of light received by the light receiving unit 24 is constant.

Further, in this embodiment, the tape position detecting section 18 provided on the tape outlet side of the cylinder also has the same structure as the above-mentioned tape position detecting section 17.

FIG. 1 is a block diagram showing the arrangement of a magnetic head position adjusting apparatus according to this embodiment. In the figure, 19 and 22 are a first sensor and a second sensor of the tape position detecting unit 17 provided on the tape entrance side. Reference numerals 25 and 26 are amplifiers for amplifying the detection outputs of the first and second sensors 19 and 22. 27 inputs the outputs from the amplifiers 25 and 26,
It is a difference circuit that outputs the difference between the levels of the input signals.

Further, 28 and 29 are a first sensor and a second sensor of the tape position detector 18 provided on the tape outlet side. 30 and 31 are the first and second sensors 28 and 29.
Is an amplifier that amplifies the detection output of. Reference numeral 32 is a difference circuit that receives the outputs from the amplifiers 30 and 31 and outputs the difference between the levels of the input signals.

Numeral 33 is a P head mounted on the guide cylinder 8 and is P in response to the rotation of the cylinder.
A PG pulse generation circuit for generating a G pulse, 34 is the P
A sampling clock generation circuit that generates a plurality of sampling clock pulses in synchronization with the G pulse, and 35 is a counter that counts the sampling clock pulses and resets the count number by the PG pulses.

Reference numeral 36 is a dynamic tracking driver for inputting the outputs from the differential circuits 27, 32, the pulse generating circuit 34, and the counter 35. The dynamic tracking driver 36 is a vertical post on the cylinder inlet side. Of the tape position of the magnetic tape 1 from the reference position, ΔB, the amount of change of the tape position from the reference position of the vertical post at the cylinder exit side from the reference position, the length of the magnetic tape 1 between the vertical posts 2 and 5 is L, and sampling is performed. The frequency of the clock is F, the number of counts in the counter 35 is N,
The displacement amount ΔX from the reference position at each sampling point of the recording / reproducing rotary head mounted on the guide cylinder 8 is obtained by the following formula (1). Reference numeral 37 is a dynamic tracking actuator that moves the rotary magnetic head in the vertical direction along the rotation axis of the cylinder by a control signal based on the displacement amount ΔX obtained by the dynamic tracking driver 36.

[0019]

[Equation 1]

Next, the operation of the magnetic head position adjusting apparatus of this embodiment will be described.

The output signal from the first sensor 19 on the tape inlet side of the cylinder includes noise such as ambient light, light emission, and temperature change of the light receiving element as well as the amount of fluctuation in the width direction of the magnetic tape 1. . On the other hand, the output signal from the second sensor 22 does not include the fluctuation amount of the magnetic tape 1 in the width direction, but includes only noise such as ambient light, light emission, and temperature change of the light receiving element. These first and second sensors 1
After the output signals from 9 and 22 are amplified by amplifiers 25 and 26, the noise level is removed from the output signal of the first sensor 19 by the difference circuit 27, and the tape position reference at the vertical post on the cylinder inlet side is obtained. Variation from position Δ
A is input to the dynamic tracking driver 36.

The first tape on the tape outlet side of the cylinder
The output signal from the sensor 28 includes noise such as ambient light, light emission, and temperature change of the light receiving element as well as the variation amount of the magnetic tape 1 in the width direction. On the other hand, the second sensor 2
The output signal from 9 does not include the fluctuation amount of the magnetic tape 1 in the width direction, but includes only noise such as ambient light, light emission, and temperature change of the light receiving element. The output signals from the first and second sensors 28 and 29 are amplified by amplifiers 30 and 31, and then the difference circuit 32 causes the first sensor 2 to operate.
The noise level is removed from the output signal of No. 8, and the variation amount ΔB of the tape position on the vertical post on the cylinder inlet side from the reference position is input to the dynamic tracking driver 36.

That is, the fluctuation amounts ΔA and ΔB input to the dynamic tracking driver 36 are accurate fluctuation amounts in the width direction of the magnetic tape 1 without being affected by noise such as disturbances. The displacement amount ΔX from the reference position of the rotary head at each sampling point is obtained by the above equation 3, and the rotary head mounted on the guide cylinder 8 moves in the vertical direction of the cylinder by the dynamic tracking actuator 37. By feedback control, the position is adjusted so as to form a highly accurate track pattern.

As described above, in the magnetic head position adjusting apparatus according to the present embodiment, the difference between the first sensor and the second sensor is calculated to accurately change the width of the magnetic tape with the noise level removed. The amounts ΔA and ΔB are calculated, and this variation Δ
Since the dynamic tracking actuator 37 is controlled by A and ΔB, even if a temperature change or an environmental change such as light from the outside occurs, the rotary head is highly accurate without being affected by the environmental change. The position can be adjusted to form a track pattern. Moreover, in the VTR of the present embodiment, the rotary head can form a highly precise track pattern as described above without mechanically forcing the variation in the width direction of the magnetic tape by the flange or the like. The tape edge of the magnetic tape 1 is not damaged.

[0025]

According to the present invention, the position of the magnetic tape can be accurately detected without damaging the tape edge of the magnetic tape and even when a change in environment such as temperature change or light from the outside occurs. Therefore, it is possible to provide a position adjusting device for a magnetic head that allows the magnetic head to scan a magnetic tape with high accuracy to form a highly accurate track pattern.

[Brief description of drawings]

FIG. 1 is a block diagram showing welfare of a magnetic head position adjusting device of the present invention.

FIG. 2 is a plan view showing the outline of the entire tape running system of the VTR of the present invention.

FIG. 3 is a diagram showing a configuration of a tape position detection unit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 18A, 18B Tape position detection part 19, 28 1st sensor 21, 23 Light emitting part 22, 24 Light receiving part 27, 32 Differential circuit 36 Dynamic tracking driver

Claims (1)

[Claims] 1. A light emitting portion which emits light toward a tape edge of a magnetic tape on a tape inlet side and a tape outlet side of a guide cylinder to which a rotary head is mounted, and a light receiving portion which receives reflected light from the light emitting portion. A first sensor having a section,
A second light emitting part that emits light toward the central portion of the tape of the magnetic tape; and a light receiving part that receives light from the light emitting part
And a tape position detecting section each of which is provided with each sensor, and is wound around the guide cylinder of the magnetic tape based on the difference information between the first sensor and the second sensor in each tape position detecting section. A position adjusting device for a magnetic head, characterized in that a displacement in a tape width direction at a portion of the magnetic head is detected, and the rotary head is controlled to move in the rotary axis direction of the cylinder by the detection signal.