JPH04372751A - Method for adjusting magnetic head position controller - Google Patents

Abstract

PURPOSE:To easily provide a method adjusting the magnetic head position controller of a magneto-optical device without using a displacement gage to measure the displacement quantity of a movable part of an optical pickup and the magnetic head. CONSTITUTION:An object lens 21 being the movable part of the optical pickup and the magnetic head 23 are connected and the object lens 21 is displaced. Thereafter the gain of a differential amplifier 33 is adjusted such that the displacement signal of the object lens outputted from the differential amplifier 28 of the first displacement sensor is equal to the displacement signal of the magnetic head 23 outputted from a differential amplifier 33 of a second displacement sensor. Thus, by equalizing the sensitivities of the first displacement sensor and the second displacement sensor, the magnetic head position controller is adjusted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a position control device for a magnetic head included in a magnetic field modulation overwrite type magneto-optical disk drive.

0002

2. Description of the Related Art In recent years, magnetic field modulation overwrite technology has been developed that allows writing without erasing. In this magnetic field modulation overwrite, when writing data to a magneto-optical disk, it is necessary to apply a magnetic field that reverses at high speed to the magnetic head, so the inductance of the magnetic head coil must be reduced. However, if the inductance is reduced, the number of turns in the coil will be reduced and the generated magnetic field will be reduced. In order to write data on a magneto-optical disk using a small magnetic field, it is necessary to narrow the distance between the magnetic head and the magneto-optical disk. For example, compact disc (CD)
) and CD-ROM, the distance between the magnetic head and the magneto-optical disk is 0.1 to 0.
．． It is about 2 mm. On the other hand, the surface runout and warpage of magneto-optical disks are as large as approximately 1 mm, and for fixed magnetic heads, the distance between the magneto-optical disk and the magnetic head is 0.1 to 0.2.
It is not possible to maintain it at about mm.

For these reasons, in a magneto-optical disk drive using a magnetic field modulation overwrite method, the magnetic head is generally attached to an actuator and moved in a direction perpendicular to the surface of the magneto-optical disk, thereby controlling the interaction between the magnetic head and the magneto-optical disk. A control method is used to keep the interval constant.

One of the configurations of a magnetic head position control device for such a magneto-optical disk device is shown in FIG. In FIG. 2, 21 is an objective lens which is a movable part of the optical pickup 20, and 39 is an objective lens actuator. 23 is a magnetic head, and 37 is a magnetic head actuator. The first displacement sensor detects the displacement of the objective lens 21 in the focus direction, and includes a light emitting LED (LED).
Diode) 24, PSD (Position Se)
nsing Device) 25, current voltage converter 2
6, 27, and a differential amplifier 28. The second displacement sensor detects the displacement of the magnetic head 23, and includes a light emitting element 29, a light receiving element 30, current voltage converters 31, 32,
It consists of a differential amplifier 33. 22 is a magneto-optical disk, 34
35 is a phase compensation circuit for stabilizing the control loop, 36 is a magnetic head drive circuit, and 38 is an arm for connecting the magnetic head actuator 37 and the optical pickup 20. The objective lens 21 and the magneto-optical disk 22 are controlled by a focus servo (not shown) to maintain a constant distance, so that their displacements match.

The operation of the magnetic head position control device shown in FIG. 2 will be explained below. The displacement amount of the magneto-optical disk 22 is indirectly detected by detecting with the first displacement sensor the displacement amount of the objective lens 21 whose displacement matches that of the magneto-optical disk 22, and this displacement amount and the second displacement are detected. The actuator of the magnetic head 23 is adjusted so that the amount of displacement of the magnetic head 23 detected by the sensor is equal.

To explain in more detail, the first displacement sensor is an LE mounted on the movable part of the optical pickup.
The displacement signal from D24 is detected by PSD25 attached to the fixed part of the optical pickup. Two output terminals are attached to this PSD 25, and the current value from each output terminal changes depending on the position of the light spot. These two currents are transferred to the current-voltage converter 2
6 and 27, respectively, and the difference between these voltages is outputted from a differential amplifier 28, thereby detecting a displacement signal of the objective lens 21. Similarly, a displacement signal of the magnetic head 23 is detected by the second displacement sensor.

The displacement signal of the objective lens 21 output from the differential amplifier 28 and the displacement signal of the magnetic head 23 output from the differential amplifier 33 are input to a subtracter 34, and after passing through a phase compensation circuit 35, The power is amplified by the drive circuit 36 and drives the magnetic head actuator 37 .

[0008] In this way, the amount of displacement of the magnetic head 23 is controlled to be equal to the amount of displacement of the objective lens 21 and the magneto-optical disk 22.

However, with the above method, the magnetic head 2
When the displacement amount of 3 is adjusted, the first displacement sensor and the second displacement sensor are adjusted.
If the sensitivities of the displacement sensors differ, an error will occur in the adjusted displacement amount. For example, the sensitivity of the first displacement sensor is 1V/
Assuming that the sensitivity of the second displacement sensor is 1.2V/mm in mm, the magnetic head 2 is set so that when the output of the first displacement sensor is 0.5V, the output of the second displacement sensor is 0.5V.
When the position of 3 is controlled, the displacement of the objective lens 21 is 0.5
mm, whereas the displacement of the magnetic head 23 is 0.6 mm.
mm, resulting in an error of 0.1 mm. The difference in sensitivity between the first displacement sensor and the second displacement sensor is mainly caused by variations in the drive current of the light source versus the amount of light and variations in the received light amount versus output current characteristic of the optical spot position detector. It is something that cannot be avoided.

A method conventionally used for matching the sensitivities of the first displacement sensor and the second displacement sensor will be explained based on the flowchart of FIG.

In FIG. 4, the objective lens 21 is displaced and the amount of displacement ΔL is measured by a displacement meter. Next, the first
After measuring the amount of change ΔV1L in the output of the first displacement sensor using a voltmeter, the sensitivity of the first displacement sensor is calculated as ΔV1L/ΔL.
Find it as.

Similarly, the magnetic head is displaced and the amount of displacement ΔM is measured. The gain of the differential amplifier 33 is adjusted so that the output ΔV2M from the differential amplifier 33 at that time becomes equal to the value of ΔM·ΔV1L/ΔL.

After adjusting the magnetic head position control device by matching the sensitivities of the first and second displacement sensors as described above, the magneto-optical disk device of FIG. 2 is used.

Table 1 shows the results of measuring the detection sensitivity ΔVL/ΔL for 11 displacement sensors. Table 1 shows that the sensitivity varies greatly depending on the displacement sensor.

[0015]

[Table 1]

[0016]

However, the conventional method described above requires a displacement meter when adjusting the sensitivity of the displacement sensor. This displacement meter needs to have relatively high measurement accuracy of about ±10 μm, and because the thrust of the objective lens of the optical pickup and the actuator of the magnetic head is small, it needs to be a non-contact type displacement meter. Such displacement meters are generally expensive.

An object of the present invention is to provide a method for easily adjusting a magnetic head position control device without using such an expensive displacement meter.

[0018]

[Means for Solving the Problems] The present invention provides a displacement amount adjustment method for controlling the amount of displacement of a magnetic head of a magneto-optical disk drive, which comprises coupling an optical pickup and a magnetic head of the magneto-optical disk drive. , the optical pickup is displaced, the resulting displacement of the optical pickup itself is measured by a first displacement sensor, the displacement of the magnetic head at this time is measured by a second displacement sensor, and then the first The amount of displacement of the optical pickup detected by the displacement sensor and the second
The first displacement sensor or the second displacement sensor is adjusted so that the amount of displacement of the magnetic head detected by the displacement sensor is equal to the amount of displacement of the magnetic head.

[0019]

[Operation] Since the objective lens and the magnetic head are connected, equal displacement can be applied to the objective lens and the magnetic head. If the displacements are equal in this way, the sensitivities can be made the same simply by matching the amounts of change in the displacement signals output from the respective displacement sensors. Therefore, the first and second
The sensitivities of the displacement meters can be easily matched, and the magnetic head position control device can be adjusted without using an expensive displacement meter.

[0020]

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

FIG. 1 shows a magnetic head position control device for explaining an adjustment method of the magnetic head position control device according to the present invention, and FIG. 3 is a flowchart for explaining the present invention. In FIG. 1, 1 is an objective lens 21 and a magnetic head 2.
This is a connector for connecting 3, and can be removed using a connecting jig. 2 is a first measuring device for measuring the displacement signal of the objective lens, and 3 is a second measuring device for measuring the displacement signal of the magnetic head 23.

In FIG. 1, parts that have the same configuration and operate in the same way as the magnetic head control device shown in FIG. 2 are designated by the same reference numerals, and their explanation will be omitted.

The process will be explained below based on the flowchart shown in FIG. First, as shown in FIG. 3, the objective lens 21 and the magnetic head 23 were connected using the coupler 1. Next, the objective lens 21 is displaced, but the objective lens 21 and the magnetic head 2
3 is connected by the connector 1, so it is displaced in the same way. In this embodiment, a sine wave is input to the drive circuit of the objective lens actuator 39 to cause a current to flow through the objective lens actuator 39, thereby displacing the objective lens 21.

Next, displacement signals of the objective lens 21 and the magnetic head 23 outputted from the differential amplifiers 28 and 33 are measured using the displacement measuring devices 2 and 3, respectively.

The displacement signal of the objective lens 21 at this time is ΔV
1L and the displacement signal of the magnetic head 23 is ΔV2M,
The magnetic head 2 is adjusted so that ΔV1L and ΔV2M are equal.
The gain of the differential amplifier 33 on the third side is adjusted. In this embodiment, the drive circuit of the objective lens actuator 37 has a sinusoidal
Since the objective lens 21 is displaced by inputting a wave, the output displacement signal also becomes a sine wave. Therefore, 2
The gain of the differential amplifier 33 may be adjusted so that the signal amplitudes of the displacement signals consisting of two sine waves are equal. Thereafter, the coupler 1 is removed, and the sensitivity adjustment of the second displacement sensor is completed.

In this embodiment, a current is applied to the objective lens actuator 39 to displace the objective lens 21.
The displacement sensor on the objective lens 21 side may be adjusted by displacing the magnetic head 23 by passing a current through the magnetic head actuator 37. Further, in the displacement sensor used in this embodiment, the amount of displacement was detected using a combination of an LED and a PSD, but the amount of displacement may be detected using a capacitance detection type, an eddy current detection type, or the like. Furthermore, in this embodiment, the sensitivity of the displacement sensor was adjusted by adjusting the gain of the differential amplifier, but by providing a variable gain amplifier for sensitivity adjustment after the differential amplifier and adjusting the gain, the displacement sensor You may adjust the sensitivity.

[0027]

According to the present invention, with the optical pickup and the magnetic head connected, the optical pickup is displaced, and the resulting displacement of the optical pickup itself is measured by the first displacement sensor; The amount of displacement of the magnetic head at this time is measured by a second displacement sensor, and the first displacement sensor or the second displacement sensor is adjusted so that the amount of displacement of the optical pickup and the amount of displacement of the magnetic head are equal. Therefore, a displacement meter is not required, and the magnetic head position control device can be adjusted at low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a magnetic head position control device for explaining one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a magnetic head position control device for explaining a conventional example.

FIG. 3 is a flowchart for explaining the operation of one embodiment of the present invention.

FIG. 4 is a flowchart for explaining a conventional example.

[Explanation of symbols]

1 Coupler 2, 3 Displacement measuring device 21 Objective lens 22 Magneto-optical disk 23 Magnetic head 24, 29 LED 25, 30 PSD 26, 27, 31, 32 Current-voltage converter 33, 28
differential amplifier

Claims (1)

[Claims] 1. A method for adjusting a magnetic head position control device of a magneto-optical disk device, comprising: coupling an optical pickup movable section and a magnetic head; displacing the optical pickup movable section; After measuring the amount of displacement with the first displacement sensor and further measuring the amount of displacement of the magnetic head at this time with the second displacement sensor, it is determined that the amount of displacement of the optical pickup movable part and the amount of displacement of the magnetic head are equal. 1. A method for adjusting a magnetic head position control device, comprising: adjusting the gain of the first displacement sensor or the second displacement sensor so that the first displacement sensor or the second displacement sensor is adjusted.