JPH04117610A - Optical disk recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain distance detecting signals even when the reflectivity of the back face of a disk is not equal by providing a pressure sensor on a magnetic head so that a pressure in the neighborhood of a disk surface, which is generated due to the rotation of the disk, can be detected. CONSTITUTION:An objective lens 2 is arranged at the one side, and a magnetic head 3 constituted of a magnetic core 301 and a magnetic field generating coil 302 with which the magnetic core is wound is arranged at the other side with interposed disk 1. Then, a hole 303 is prepared at the central part of the magnetic head 3, and a strain gage 9 is adhered through a thin plastic plate 10 to the side which is not opposed with the disk 1 so that the hole 303 can be filled up. The pressure P of the center of the magnetic head 3 is transmitted through the hole 303 to the thin plastic plate 10 on the top face of the magnetic head 3, and can be detected by the strain gage 9. Thus, the distance detecting signals can be obtained regardless of the reflectivity of the back face of the disk.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disk recording/reproducing device, and more specifically, the present invention relates to an optical disk recording/reproducing device, and more specifically, by applying an external magnetic field to the disk and increasing the temperature by a light spot, the optical magnetism on the disk is improved. Optical disk recording and playback in which recording is performed by changing the direction of magnetization of the recording medium, and during playback, a light spot with lower power than during recording is irradiated onto the surface of the magneto-optical recording medium, and the direction of magnetization is optically read. It is related to the device.

[Prior Art] FIG. 4 is a sectional view showing the main parts of a conventional optical disc recording/reproducing device. In the figure, 1 is a magneto-optical disk (hereinafter referred to as a disk), 2 is an objective lens for forming a light spot across the disk L, and 3 is a magnetic field that applies a magnetic field to the disk 1 when recording and erasing information. The magnetic head is composed of a core 301 and a magnetic field generating coil 302 wound around the core. Further, the magnetic head 3 is fixed to the movable holder 5 together with an optical distance detection mechanism 4 consisting of a light emitting diode 401 and a two-split photodetector 402. A cylindrical driving coil 6 is attached to the other end of the movable holder 5 and is disposed in a magnetic gap formed by the yoke 7 and the radially magnetized driving magnet 8.

Next, the operation will be explained using FIGS. 5 and 6.

Figure 5 is a characteristic diagram showing the relationship between the distance d between the disk and the magnetic head and the magnetic field strength H on the disk information recording surface.As is clear from this diagram, it can be seen that as the distance d increases, the magnetic field strength H decreases. .

In this configuration, the distance d is 0.2 mm to ensure the necessary magnetic field (about 2000 e) on the information recording surface of the disk l.
Must be kept below. However, disk 1 is connected to the motor (
(not shown), and the amount of fluctuation of the disk 1 due to surface runout, deflection, etc. of the disk 1 may be about ±0.7 mm.If the magnetic head position is fixed, the disk 1 and the magnetic head 3 may collide or the necessary magnetic field strength may not be secured. Therefore, a mechanism is required to detect the amount of variation in the disk 1, drive the magnetic head 3, and keep the distance d constant.

Next, a mechanism for keeping the distance d constant will be explained.

In Fig. 6, (a) to (C) are, for example, published in Japanese Patent Application Laid-Open No. 1-25135.
9 is a diagram showing the operating principle of the conventional optical magnetic head distance detection mechanism disclosed in Publication No. 9, in which a light emitting diode 401
The substantially parallel beam emitted obliquely to the disk 1 is reflected by the surface of the disk 1 and enters the two-split photodetector 402 . Figure 6 (a), (b), (c
), when the position of the disk 1 changes, the light spot on the two-split photodetector 402 moves in the direction perpendicular to the dividing line, so by taking the difference between the two divided detection signals, the distance detection signal E is obtained. can be obtained. Further, by dividing this distance detection signal E by the sum signal of the two-split photodetector 402, it is possible to obtain a distance detection signal even for disks l having slightly different reflectances. Then, by applying a current proportional to the distance detection signal to the drive coil 6 disposed in the magnetic field, an electromagnetic force acts, and the magnetic head 3 fixed to the movable holder 5 is moved at a distance d as the disk l changes. is driven so that it remains constant.

[Problems to be Solved by the Invention] Since the conventional optical disc recording/reproducing device is configured as described above, the reflectance may be low due to a label printed on the back surface of the disc 1 facing the magnetic head 3, etc. For non-uniform objects, it becomes difficult to obtain a distance detection signal,
There was a problem in that the distance between the magnetic head 3 and the disk 1 could not be kept constant, making recording and erasing operations unstable.

This invention was made to solve the above-mentioned problems, and it provides an optical disc recording/reproducing system that can record, reproduce, and erase data even on discs with uneven reflectance due to a label printed on the back side, etc. The purpose is to provide equipment.

[Means for Solving the Problems] An optical disk recording/reproducing apparatus according to the present invention is provided with a pressure sensor on a magnetic head so as to detect the pressure caused by the air flow near the disk surface caused by the rotation of the disk.

[Function] In the optical disc recording and reproducing apparatus according to the present invention, since a pressure sensor is used in the distance detection mechanism of the magnetic head, it is possible to obtain a distance detection signal that is related to the reflectance of the back surface of the disc.

[Example] Hereinafter, this invention will be explained based on the drawings.

FIG. 1 is a cross-sectional view showing an optical disc recording/reproducing apparatus according to an embodiment of the present invention, in which an objective lens 2 for focusing a light spot is provided on one side of the disc I, and an objective lens 2 is provided on the other side with the disc I interposed therebetween. A magnetic head 3 composed of a magnetic core 301 that applies a magnetic field to the disk 1 when recording and erasing information and a magnetic field generating coil 302 wound around the magnetic core 301 is arranged.

The magnetic head 3 is mounted on the movable holder 5.
A cylindrical driving coil 6 is attached to the other end of the movable holder 5, and is disposed in a magnetic gap formed by the yoke 7 and the radially magnetized driving magnet '-8. The above configuration is the same as the conventional example, but in this example, a hole 303 is provided in the center of the magnetic head 3, and on the side that does not face the disk l, a strain gauge 9 is inserted through a thin plastic plate IO. It is glued so as to close the hole 303.

Next, the operation will be explained.

As shown in FIG. 2, the disk 1 is connected to a motor (not shown).
Since the disk is being rotated at a constant linear velocity (CLV) in the A direction, an airflow F is generated near the disk 1, and the magnetic head 3
The pressure distribution at the tip is as shown in C. The pressure P at the center of the magnetic head 3 is transmitted to the thin plastic plate 10 on the top surface of the magnetic head 3 through the hole 303, and this can be detected by the strain gauge 9. Therefore, by applying current to the drive coil 6 to drive the magnetic head 3 so as to keep the pressure P constant, the magnetic head 3. The distance d between the disks 1 can be kept constant. Also, the disk 1 has a constant angular velocity (CA
Even when rotating at V), the distance d can be kept constant by calculating the linear velocity of the disk.

FIG. 3 is a sectional view of the main parts of another embodiment of the invention. In the figure, reference numeral 11 denotes a semiconductor pressure sensor, which is arranged so as to close the upper end of the hole 303 as in the first embodiment, and detects the pressure P. The distance d of 1 can be kept constant.

[Effects of the Invention] As described above, according to the present invention, a pressure sensor is provided on the magnetic head as a distance detection means for the magnetic head so as to be able to detect the pressure near the disk surface caused by the rotation of the disk. Therefore, a distance detection signal can be obtained even if the reflectance is uneven, such as when a label is printed on the back of the disk.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an optical disc recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of the main part in FIG. 1, and FIG. 3 is a sectional view of the main part of another embodiment of the invention. 4 is a sectional view showing the main parts of a conventional optical disk recording/reproducing device, FIG. 5 is a characteristic diagram showing the relationship between the distance Md between the disk and the magnetic head and the magnetic field strength H on the disk recording surface, and FIG.
Figures (a) to (c) are diagrams showing the principle of a conventional optical magnetic head distance detection mechanism. In the figure, 1 is a disk, 2 is an objective lens, 3 is a magnetic head, 5 is a movable holder, 6 is a driving coil, 7 is a yoke, 9 is a strain gauge, 10 is a plastic plate, 11 is a semiconductor pressure sensor, and 301 is a A magnetic core, 302 is a magnetic field generating coil, and 303 is a hole. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] an objective lens that focuses a light spot on a magneto-optical disk;
A magnetic head is disposed on the opposite side of the objective lens across the magneto-optical disk and applies a magnetic field when recording and erasing information, and the distance between the magnetic head and the magneto-optical disk is detected and distance information is obtained. distance detection means that outputs
In an optical disk recording and reproducing apparatus comprising: a magnetic head driving means for driving a magnetic head so that the distance becomes constant based on the distance information; An optical disc recording and reproducing device characterized by using a pressure sensor that detects changes.