JPS59152503A - Optical pickup device - Google Patents

Abstract

PURPOSE:To reduce the overall weight and capacity of an optical head and at the same time to eliminate the evil effect of generation of heat, by protruding a ferromagnetic substance extended from a part of a magnetic circuit which drives an objective lens against a recording medium and therefore ensuring the effective use of the leaked magnetic flux of the magnetic circuit to obtain a magnetic field. CONSTITUTION:A projection part 32 of a ferromagnetic substance is fixed at the tip of a yoke 7b of one side and opposite to the recording surface of a recording medium 11. Thus the magnetic flux leaked from a magnetic circuit is led to a place nerar the medium 11 via the part 32 as shown by an arrow 33, and the magnetic field is intensified on the medium 11. Therefore a magnetic field of the direction where the magnetization is easily produced acts on the medium 11 by the leaked magnetic flux of the magnetic circuit applied via the part 32. Thus it is possible to record the information as conventional with irradiation of a light beam. In such a way, a magnetic field is applied to the medium 11 by means of a magnetic flux leaked from a magnetic circuit which drives an objective lens 2. Thus, a magnetism applying device consisting of an electromagnet, a coil, etc. is eliminated. Therefore the overall weight and capacity of an optical head including an optical pickup device can be greatly reduced.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an optical pickup device angle that uses electromagnetic force to adjust a lens focus, etc., and in particular to an optical pickup device that focuses a light beam on a recording medium made of a magnetic thin film. The present invention is suitable for an optical pickup device of a magneto-optical recording device that records, reproduces and erases information using a magneto-optical recording device.

Prior Art Conventionally, in this type of magneto-optical recording device, when recording information, a light beam is generally focused into a spot on a disk-shaped recording medium made of a thin uniaxially anisotropic magnetic material such as GdTbFe. By heating the irradiated portion to a temperature near the cue point, a magnetization reversal region is formed, thereby recording an information signal. Further, at this time, the light beam is irradiated onto the recording medium that is uniformly magnetized in the perpendicular direction while applying a magnetic field using an electromagnet or the like in a direction that facilitates magnetization reversal. - When reproducing recorded information, a relatively weak light beam suitable for reading information is focused onto the recording medium mentioned above, and the reflected light or transmitted light of the light beam is The reproduced signal is obtained by utilizing the fact that the Kerr rotation angle or Faraday rotation angle differs depending on the magnetization direction.

For this reason, in the conventional device δ, in order to constantly focus the light beam on the recording medium when recording and reproducing information TFU, the entire optical system or a portion of the optical system such as the objective lens is focused using electromagnetic force. An optical pickup device equipped with a drive mechanism that drives in the force direction (optical axis direction) and a magnetic field device such as an electromagnet that applies a magnetic field in a predetermined direction to a recording medium when recording information [1η] do.

Figures 1 and 2 show examples of the configuration of such a conventional optical pickup device and magnetic field attachment device, respectively.

First, to explain the conventional example shown in Fig. 1, the optical pickup device 1 shown in the figure supports an objective lens 2 for condensing light, a mirror +J3 supporting the objective lens 2, and an fm drawer 3 movable in the vertical force direction. A pair of upper and lower bullets 1; support rests 4a and 4b; a housing 5 that covers the outer edges of the elastic supports 4a and 4b; a drive coil 6 for driving the lens barrel identified in the lens barrel 3; The recording device is composed of a pair of yokes 7a and 7b that apply a magnetic field to the coil 6, a magnetic circuit that serves as a permanent magnet 8 between the yokes, and a Calhano mirror 9 that displaces the light beam in the horizontal force direction, and is irradiated with a light beam 10. It is disposed parallel to and facing the recording surface of the medium 11. - Recording medium 1 when recording power and information
An electromagnet 12 corresponding to a magnetic field applying device that applies a magnetic field of 1.
The U-shaped ferromagnetic member 13 and the coil 14 sandwiching both sides of the recording medium 1 are fixed, and the optical pin-qua-amp device 1 is assembled.
It is fixed to the casing 5 of and moves integrally.

This optical pickup device 1 picks up the recording medium 11 with a light beam 10 while moving relatively parallel to the recording medium 11.
, f: in the form of a trunk, and the information reproduction H)l reproduces the information using reflected light while tracking the information (not shown) already formed on the recording medium 1. conduct. At this time, the relative distance between the recording medium 11 and the optical pink amplifier device 1 changes depending on the unevenness of the surface of the recording medium 11, vertical movement during movement, external vibrations, and the like. Therefore,
In order to ensure that the optical beam 10 is always focused on the recording medium 11, a photodetector (not shown) detects the focal shift error (i) and adjusts the objective lens 2 to the lens barrel 3 according to the detected value. A so-called focus control is performed to set the focus force by a drive device composed of a drive coil 6 and magnetic circuits ?a, 7b and 8 via the elastic supports 4a and 4b. In order to prevent the beam 1.1o from deviating from the information track once grasped, the amount of track deviation is detected by a separately provided photodetector (not shown), and the carbanomirror 8 is driven in accordance with the detected value. Thus, so-called tracking control is performed in which the light beam 10 is displaced with respect to the surface of the medium 11.

In the conventional example shown in FIG. 2, the optical pickup device 1 is the same as that shown in FIG. an annular coil 1.4a disposed facing the surface of the
Another advantage is that it is composed of a rod-shaped ferromagnetic pole 13a disposed opposite to the optical pickup device with the recording medium 11 in between. When recording information, coil 1
The magnetic field applied to the recording medium 11 is strengthened by passing a current through the recording medium 4a to generate a magnetic field and magnetizing the magnetic pole 13a on the reflective side with the recording medium 11 in between.

However, in order to obtain the necessary magnetic field with the conventional magnetic field generating device 12 or 12a as shown in FIG. 1 or 2, the number of turns of the coil 14 or 14a (
It was necessary to increase the number of turns) or increase the J10E current flowing through the coil 14 or 14a.

This increases the volume of the coil 14 or 14a, making it difficult to arrange it in terms of space, and increasing the burden on the optical pickup device 1. Furthermore, there has been a problem in that the heat generated by the above-mentioned applied current has an adverse effect on the medium and the like.

Purpose: Therefore, in view of the two points, the present invention provides a ferromagnetic material extended from a part of the magnetic circuit for driving the objective lens of the optical pink amplifier device y1, and protrudes from a part of the magnetic circuit to face the recording surface of the recording medium. By doing so, it is possible to effectively utilize the leakage magnetic flux of the magnetic circuit to apply a magnetic field (=f) to the recording medium, thereby reducing the amount and volume of the entire optical head including the optical pump device. And 5?: An object of the present invention is to provide an optical link-up device which is free from adverse effects such as heat.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 shows an example of the configuration of an optical pickup device according to the present invention, in which parts similar to those of the conventional device shown in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted. The optical pickup device 31 shown in FIG. 3 is particularly different from the conventional device 1 shown in FIG.
A part of a magnetic circuit composed of a pair of yokes 7a and 7b and a permanent magnet 8, for example, one yoke? A protrusion 32 made of ferromagnetic material is fixed at the tip of b, and this protrusion 32 is disposed facing the recording surface of the recording medium 11.

As a result, the leakage magnetic flux leaking from the magnetic circuit mentioned above is guided to the vicinity of the recording medium 11 through the above-mentioned protrusion 32, as shown by the arrow 33 in the figure, and the magnetic field is strengthened on the recording medium. Therefore, on the information recording/reproducing surface, a magnetic field in a direction that tends to cause magnetization reversal on the recording medium acts on the information recording/reproducing surface due to the leakage magnetic flux of the magnetic circuit applied via the protrusion 32. IEQ) Information can be recorded by irradiation with a light beam. Note that even when reproducing information using the same optical pickup device, the reading light beam is weaker than the writing light beam, so information can be reproduced without magnetization rotation regardless of the effect of the magnetic field described above. .

In this way, according to this embodiment, the magnetic field can be applied to the recording medium using the leakage magnetic flux of the magnetic circuit that drives the objective lens 2, so a conventional magnetic application device consisting of an electromagnet or a coil is not required. As a result, it is possible to significantly reduce the weight and volume of the entire optical head including the optical pickup device, and to eliminate adverse effects such as heat generation due to applied current.

FIG. 4 shows another embodiment of the present invention. The optical pickup device 41 shown in the figure has almost the same structure as the device 31 of the previous embodiment shown in FIG. The difference is that a magnetic flux concentration member 42 made of a rod-shaped ferromagnetic material is disposed at substantially opposing positions. Therefore, in the present embodiment shown in FIG. 4, the leakage magnetic flux coming out of the protrusion 32 of the magnetic circuit passes through the recording medium 11 and concentrates on the ferromagnetic member 42, so the strength of the magnetic field applied to the recording medium 11 is further increased. can do. Note that the above-mentioned member 42 may be made movable depending on the magnetic field strength.

Next, another embodiment of the present invention will be described with reference to FIG. In the embodiment of FIG. 5, the magnetic circuit of the optical pickup device 51 is the same as that of FIG. 1, but a ferromagnetic member 52 and its A support member 53 is arranged.

As a result, the leakage magnetic flux leaked from the magnetic circuit magnetizes the ferromagnetic member 52, and furthermore, the ferromagnetic member 52 is attached to the recording medium 11.
2 can apply a magnetic field.

In addition, although the above-mentioned embodiment was explained using recording as an example,
The present invention can be applied to at least an optical pickup in which information is erased by directing a light beam onto a recording medium, and even in that case, an auxiliary magnetic field is applied in the direction of erasing information on the recording medium with a simple configuration. can do.

Effects As explained above, according to the present invention, a protrusion that guides the leakage magnetic flux emitted from the magnetic circuit of the optical pickup device onto the recording medium is provided in a part of the magnetic circuit. The necessary magnetic field can be applied to the recording medium when recording or erasing information without providing a separate number.As a result, the optical head can be made lighter and smaller, and adverse effects such as heat generation can be eliminated. You can get the effect that you can.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views showing an example of the configuration of a conventional device, FIG. 3 is a longitudinal sectional view showing an example of the configuration of the device of the present invention, and FIG. 4 is a longitudinal sectional view of another example of the configuration of the device of the present invention. A longitudinal cross-sectional view showing,
FIG. 5 is a longitudinal sectional view showing another example of the configuration of the device of the present invention. 1.31, 41.51... Optical pickup device, 2.
...Objective lens, □ 3... Lens barrel, 4a, 4b... Elastic support, 5... Housing, 6... Drive coil, 7a, 7b... Yoke, 8... Permanent Magnet, 9...7 mirror to Cal 7, 10...Light beam, 11...Recording medium, 12...Electromagnet, 12a...Magnetic field H4 device, 13, 13a...Ferromagnetic member , 14 , 14a... Coil, 32... Ferromagnetic protrusion, 33... Crystal leakage magnetic flux, 42.52... Ferromagnetic member, 53... Female hand 1811 material. Patent applicant: Canon Co., Ltd. Figure 1 0 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1) A device for erasing at least information recorded by condensing and irradiating a light beam on a recording medium made of a magnetic thin film using an optical pickup device having an optical system, An optical pickup device comprising: a magnetic guide means for guiding leakage magnetic flux from a magnetic circuit constituting an electromagnetic drive means for displacing the optical system in a predetermined direction to the recording medium as an auxiliary magnetic field. 2. In the apparatus set forth in claim 1, it is provided that the magnetic induction means is a ferromagnetic material protruding from a part of the magnetic circuit that drives the objective lens and facing the recording medium. Features optical pink-up device.