JPH0612724A - Magnetic field coil position controller - Google Patents

Abstract

PURPOSE:To keep the relative distance between a magnetic field coil and a magneto-optical disk constant regardless of variations in the temperature characteristics of a circuit, optical disturbance and the reflectivity of a magneto- optical disk and to attain the miniaturization of a magneto-optical disk recorder and the reduction in weight by constituting a controller with a light emitting element and light receiving elements. CONSTITUTION:In the magnetic field coil position controller of the magneto- optical disk recorder, a light emitting element 6 which illuminates the surface opposed to a magnetic field coil 1 of the magneto-optical disk 4 by diffused light and two light receiving elements 7 and 8 for receiving the diffused light reflected at the above-mentioned surface are driven together with the coil 1. Also depending on the level difference of the outputs of respective elements 7 and 8, the relative distance between the disk 4 and the coil 1 is kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field coil position control device used in a magneto-optical disk recording device.

[0002]

2. Description of the Related Art In a magneto-optical disk recording apparatus, a magnetic field coil for applying a magnetic field for recording and erasing information to the magneto-optical disk is arranged in non-contact with the magneto-optical disk in order to obtain high reliability and durability. Conventionally, the above-mentioned magneto-optical disk is fixed at a position farther than the range in which it is vertically moved due to so-called surface wobbling.

However, in this case, since the relative distance between the magneto-optical disk and the magnetic field coil becomes large, it is necessary to generate a strong magnetic field from the magnetic field coil, which results in a large power consumption. There are drawbacks such as electromagnetic radiation radiation.

Therefore, the magnetic field coil can be brought close to the magneto-optical disk by providing a control mechanism for keeping the relative distance to the magneto-optical disk constant as in the focus servo mechanism of the optical pickup. It is desirable to do so.

As such a device, for example, the following has been proposed.

For example, in the structure shown in FIG. 7, a mechanism for detecting a change in the relative distance to the magneto-optical disk 60 using a laser beam is mounted in a housing 62 common to the magnetic field coil 61, as in the optical pickup. . The laser beam output from the laser diode 63 is passed through the collimator lens 64 and the objective lens 65 to produce the magneto-optical disk 6 described above.
The laser beam that has been irradiated onto the laser beam 0 and reflected from the magneto-optical disk 60 is separated from the outward path by the beam splitter 66 and is passed through the cylindrical lens 67 to the photodetector 6
Given to 8.

Then, the light quantity distribution of the laser beam given to the photodetector 68 is detected by the stigma method or the off axis method (see Japanese Patent Laid-Open No. 50-110647), and an output indicating the displacement is output from the differential amplifier 69. obtain. By driving the drive coil 71 by the drive circuit 70 according to this output, the magnetic field coil 61 and the magneto-optical disc 60 are driven.
Servo is applied so that the relative distance d to and becomes constant.

In addition, as shown in FIG. 8, a set of a light emitting element 81 and a light receiving element 8 are arranged so as to face the magneto-optical disk 80.
2 are attached to a housing 84 common to the magnetic field coil 83. The light emitting element 81 illuminates the magneto-optical disk 80, and the light reflected by the magneto-optical disk 80 is received by the light receiving element 82. The amount of light received by the light receiving element 82 depends on the relative distance d to the magneto-optical disk 80. Therefore, the output voltage V of the light receiving element 82 depends on the relative distance d as shown by the solid line in FIG. Change.

Therefore, this relative distance d is the predetermined distance d.
A differential output between the output voltage V of a predetermined voltage V _R and the light-receiving element 82 when the _R form with the differential amplifier 85, the driving coil 87 by the drive circuit 86 in response to the differential output By driving, the servo is applied so that the relative distance d between the magnetic field coil 83 and the magneto-optical disk 80 becomes the predetermined distance d _R.

[0010]

However, in the device shown in FIG. 7, for example, a large number of high-precision optical components that require adjustment are used, which complicates the configuration and reduces the size and cost. It has the drawback of not being suitable.

Further, for example, in the case shown in FIG. 8, the output voltage V of the light receiving element 82 is the predetermined voltage V.
_In order to apply the servo so that it becomes _R , the relative distance d is changed when the characteristics are changed as shown by the phantom line in FIG. It has the drawback that it cannot be kept constant.

The present invention has been made in view of the above problems, and it is an object of the present invention to keep the relative distance between a magneto-optical disk and a magnetic field coil constant without causing the above-mentioned drawbacks. It is to provide a magnetic field coil position control device having a novel configuration that can be performed.

[0013]

In order to achieve the above-mentioned object, a magnetic field coil position control device according to the present invention comprises a light emitting means for illuminating a surface of a magneto-optical disk facing a magnetic field coil with diffused light. Two light receiving means arranged at mutually different angle positions with respect to a vertical line from the light emitting means to the facing surface, and for generating an output according to the amount of received diffused light from the light emitting means reflected by the facing surface; A differential detecting means for driving the light emitting means and the light receiving means in the perpendicular direction together with the magnetic field coil, and a differential detecting means for detecting a level difference between outputs of the light receiving means. The driving means is driven according to the output of the.

Further, in order to adjust the level balance of the outputs of the respective light receiving means, the output of the light receiving means is provided between at least one of the two light receiving means and the differential detecting means. It is possible to provide a level conversion means for converting the level of the.

[0015]

In the magnetic field coil position control device according to the present invention, 2
Since the two light receiving means are arranged at different angular positions with respect to the perpendicular from the light emitting means to the facing surface of the magneto-optical disk, the magneto-optical disk and the magnetic field when the output level of each of the light receiving means becomes maximum. The relative distance from the coil is different. Then, in the middle of the relative distance where the output level of each of these light receiving means is maximum, the output level of each of the above light receiving means becomes equal. The relative distance at which the output levels of the respective light receiving means are equal does not change due to factors commonly acting on the respective light receiving means, such as the temperature characteristics of the circuit, the disturbance of light, the fluctuation of the reflectance of the magneto-optical disk, etc. It is constant.

Therefore, in the magnetic field coil position control device according to the present invention, the level difference of the output of each light receiving means is differentially detected as the information indicating the displacement from the relative distance where the output level of each light receiving means becomes equal. Servo is applied so that the relative distance between the magneto-optical disk and the magnetic field coil becomes a relative distance at which the output levels of the respective light receiving means become equal according to the detection output.

Further, by providing level converting means for converting the level of the output of the light receiving means between at least one of the two light receiving means and the differential detecting means, each light receiving means is provided. It is possible to correct the balance of the output levels of the means and set so as to cross at a desired relative distance.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an essential part of a magneto-optical disk recording apparatus to which the present invention is applied.

A magnetic field coil 1 for generating a magnetic field corresponding to a recording signal is attached to a housing 2 and the housing 2
It is driven together with the housing 2 in the near-far direction A with respect to the magneto-optical disk 4 in accordance with the control current applied to the drive coil 3 wound around the outer wall. A light emitting element 6 such as a light emitting diode (LED) that emits diffused light and a photodiode 2 that generates an output voltage according to the amount of received light are provided on the bottom surface portion 5 of the housing 2 facing the magneto-optical disk 4. Two light receiving elements 7 and 8 are arranged close to the magnetic field coil 1.

The light emitting element 6 emits light by receiving a current supplied from an external circuit, and illuminates the surface 9 of the magneto-optical disk 4 facing the magnetic field coil 1 with diffused light. The diffused light from the light emitting element 6 is reflected by the facing surface 9 and guided to the light receiving elements 7 and 8.

Here, each of the light receiving elements 7 and 8 is located on a plane parallel to the facing surface 9 of the magneto-optical disk 4 and has different predetermined distances x ₁ and x ₂ (x ₁ <from the light emitting element 6).
x ₂ ) spaced apart. Therefore, the light receiving elements 7 and 8 are arranged from the light emitting element 6 to the facing surface 9
They are arranged at positions at different angles θ ₁ and θ ₂ with respect to the perpendicular line r to.

By arranging the light receiving elements 7 and 8 in this way, the light receiving element 7 and the light receiving element 8 are different in distance position from the facing surface 9 where the amount of received light is maximum, and The output voltages a and b change as shown in FIG. 2 according to the relative distance d between the magnetic field coil 1 and the facing surface 9.

That is, the light receiving element 7 arranged closer to the light emitting element 6 than the light receiving element 8 has a relative distance d ₁ shorter than the relative distance d _{3 at} which the light receiving amount of the light receiving element 8 is maximum.
The amount of received light becomes maximum, and the output voltage a thereof becomes maximum.
In the light receiving element 7, the amount of light received decreases as the magnetic field coil 1 moves away from the facing surface 9 of the magneto-optical disk 4 with respect to the relative distance d _1, so the output voltage a also decreases.

Further, in the other light receiving element 8, the light receiving amount increases as the magnetic field coil 1 is farther from the facing surface 9 than the relative distance d ₁ , and the light receiving amount becomes maximum at the relative distance d ₃ . The output voltage b also increases according to such a change in the amount of received light. Then, in the middle of the relative distance d _{1 at} which the light receiving amount of the light receiving element 7 is maximum and the relative distance d _{3 at} which the light receiving amount of the light receiving element 8 is maximum, these light receiving elements 7,
Relative distance d _{2 at which the} output voltages a and b of 8 are equal to each other
There is.

The relative distance d _{2 at} which the output voltages a and b of the light receiving elements 7 and 8 are equal to each other is the above-mentioned temperature characteristic of the circuit, disturbance of light, fluctuation of reflectance of the magneto-optical disk 4, and the like. It does not change depending on the factors that commonly act on the light receiving elements 7 and 8.

That is, for example, when the reflectance of the magneto-optical disk 4 decreases, the amount of light received by each of the light receiving elements 7 and 8 decreases at the same rate.
The output voltages a and b of No. 8 also decrease at the same rate as shown by the phantom line in FIG. 2, but the relative distance d ₂ at which the output voltages a and b become equal does not change.

In order to satisfy such a relationship, the light receiving elements 7 and 8 are arranged at different angular positions with respect to a perpendicular line r from the light emitting element 6 to the facing surface 9 of the magneto-optical disk 4. For example, as shown in FIG. 3, the light receiving elements 7 and 8 may be arranged at positions having different distances y ₁ and y _{2 in the} direction perpendicular to the facing surface 9 of the magneto-optical disk 4.

Output voltages a and b of these light receiving elements 7 and 8
Is supplied to the differential amplifier 10 and becomes an output voltage c according to the difference between the output voltages a and b in the differential amplifier 10. The output voltage c is always 0 at the relative distance d ₂ as shown in FIG. Then, when the relative distance d ₂ deviates in the relative distance d ₁ direction, a positive value is obtained,
If the relative distance d ₂ deviates in the relative distance d ₃ direction, the value becomes negative.

Further, even when the output voltages a and b of the respective light receiving elements 7 and 8 change as shown by the phantom line in FIG. 2, the output as shown by the phantom line in FIG. Although the absolute value of the voltage c changes, the polarity does not change and is always 0 at the relative distance d ₂ .

By the way, the light receiving elements 7 and 8 shown in FIGS. 1 and 2 have different angular positions with respect to the perpendicular line r from the light emitting element 6 to the facing surface 9 of the magneto-optical disk 4 as described above. However, when the light receiving amount of the light receiving device 8 whose optical path is longer than that of the light receiving device 7 becomes very small, the level of the output voltage b of the light receiving device 8 having the smaller light receiving amount becomes higher. Since it becomes low, the balance with the output voltage a of the other light receiving element 7 becomes unbalanced as shown by b _{1 in} FIG. 5, or in extreme cases, it does not cross as shown by b _{2 in} FIG. As a result, the servo targeting the relative distance d ₂ will not operate.

Therefore, in such a case, as shown in FIG. 6, an amplifier 13 for gain conversion is provided between the light receiving element 8 having a lower output voltage level and the differential amplifier 10. The level of the output voltage b of the light receiving element 8 may be increased as shown by a virtual line b _{3 in} FIG.

By providing the gain converting amplifier 13 between the light receiving element 8 and the differential amplifier 10 in this manner, the balance of the output levels of the respective light receiving means 7 and 8 is corrected and desired. It can be set to cross at the relative distance d ₂ of, and the servo can be stabilized.

In FIG. 6, the amplifiers 11 and 12 connected to the light receiving means 7 and 8 are for the first stage output of the light receiving means 7 and 8.

Further, as shown in FIG. 6, by providing a differential amplifier 14 at the subsequent stage of the differential amplifier 10 to add a desired offset amount to the output voltage c of the differential amplifier 10, The target relative distance d ₂ can be easily set by the offset.

Referring again to FIG. 1, the output voltage c of the differential amplifier 10 is supplied from the differential amplifier 10 to the drive circuit 11. The drive circuit 11 applies a control current to the drive coil 2 according to the output current c, and drives the housing 4 in the direction in which the output current c becomes 0 by the drive coil 2.

This drive mechanism can be constructed similarly to the focus control drive unit of the optical pickup. Therefore, the magnetic field coil 1 is controlled so that the relative distance to the facing surface 9 of the magneto-optical disk 4 is always kept constant.

[0038]

Since the magnetic field coil position control device according to the present invention controls the relative distance between the magneto-optical disk and the magnetic field coil in accordance with the level difference between the outputs of the two light receiving means, the temperature characteristics of the circuit and the optical characteristics of the circuit are controlled. The relative distance can always be kept constant irrespective of disturbance or fluctuations in the reflectance of the magneto-optical disk.

Therefore, by applying the present invention to the magneto-optical disk recording apparatus, the magnetic field coil can be brought closer to the magneto-optical disk, so that the power consumption can be reduced and the electromagnetic wave radiation interference can be eliminated. become.

Further, since the magnetic field coil position control device according to the present invention is simply constituted by the light emitting means and the two light receiving means as described above, it is very difficult to reduce the size and cost of the magneto-optical disk recording device. Be beneficial.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a magneto-optical disk recording apparatus according to an embodiment in which a magnetic field coil position control device according to the present invention is applied to the magneto-optical disk recording apparatus.

FIG. 2 is a characteristic diagram showing a relationship between a relative distance between a magneto-optical disk and a drive coil of the magneto-optical disk recording apparatus according to the above-described embodiment and an output voltage of each light receiving element.

FIG. 3 is a sectional view showing a main part of a magneto-optical disk recording apparatus according to another embodiment in which the magnetic field coil position control device according to the present invention is applied to the magneto-optical disk recording apparatus.

FIG. 4 is a characteristic diagram showing the relationship between the relative distance and the output voltage of the differential amplifier in the magneto-optical disk recording apparatus according to the embodiment.

FIG. 5 is a characteristic diagram showing a relationship between the relative distance and the output voltage of each light receiving element in the magneto-optical disk recording apparatus according to the other embodiment.

FIG. 6 is a circuit diagram showing another configuration example of the circuit section of the magneto-optical disk recording device shown in FIGS. 1 and 2.

FIG. 7 is a sectional view of a conventional magnetic field coil position control device.

FIG. 8 is a sectional view of another conventional magnetic field coil position control device.

FIG. 9 is a characteristic diagram showing a characteristic of an output voltage of a light receiving element provided in another conventional magnetic field coil position control device.

[Explanation of symbols]

 1 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Magnetic field coil 3 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Drive coil 4 ・ ・ ・ ・ ・ ・ ・ ・.. Magneto-optical disk 6 ... Light-emitting element 7, 8 ... Light-receiving element 10 ...・ ・ ・ ・ ・ ・ Differential amplifier 11 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Drive circuit 13 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Amplifier for gain conversion

Claims (2)

[Claims] 1. A light emitting means for illuminating a surface of a magneto-optical disk facing a magnetic field coil with diffused light, and a light emitting means arranged at different angular positions with respect to a perpendicular line from the light emitting means to the facing surface. 2 produces an output according to the amount of diffused light received from the light emitting means reflected by
A light receiving means, a driving means for driving the light emitting means and the respective light receiving means together with the magnetic field coil in the perpendicular direction, and a differential detecting means for detecting a level difference between outputs of the respective light receiving means, A magnetic field coil position control device for driving the drive means according to the output of the differential detection means. 2. The level conversion means for converting the level of the output of the light receiving means is provided between the light receiving means of at least one of the two light receiving means and the differential detecting means. Magnetic field coil position controller.