JPS63160025A - Optical head - Google Patents

Abstract

PURPOSE:To attain small size and light weight of an optical head by making a light incident into an optical path up to an objective lens collecting light onto an information recording medium from the opposite side while clipping a support means supporting the objective lens so as to eliminate a useless space. CONSTITUTION:A disk 40 with an information track 42 formed thereupon is supported turnably onto a driver and the objective lens 44 is provided under the disk 40. the lens 44 is driven by a drive means in focusing and tracking direction x, y. The center line 46 of the center rotary shaft in the direction (y) is arranged between a collimator lens 50 and the lens 44 with respect to a semiconductor laser 48. Moreover, a beam shaping prism 54, a mirror 58 and a PBS 56 are arranged at the position of the center line 46 and the light beam radiated from the laser 48 is radiated to the optical path reaching an RF disk 52. Then the laser beam is incident in the RF disk 52 from the opposite side while clipping the center line 46 for the support of the lens 44 to attain light weight and small size of the optical head.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head provided in an optical information recording/reproducing device such as a magneto-optical disk device.

[Conventional technology]

With the development of today's electronics.

2. Description of the Related Art Optical information recording and reproducing devices that can randomly record and/or reproduce and/or erase audio or image information with high performance using a light beam such as a laser beam are being commercialized.

In particular, in a magneto-optical disk, a magnetic thin film having an axis of easy magnetization perpendicular to the film surface on a substrate is formed, and information is recorded by changing the direction of magnetization force in this magnetic thin film. During recording, the magnetization direction of the magnetic thin film is first aligned in one direction, and a laser beam digitally modulated in accordance with an information signal is irradiated while applying a bias magnetic field in the opposite direction to the magnetization direction. As a result, the temperature of the area irradiated by the laser beam increases, the coercive force decreases, and the area is magnetized in the opposite direction to the surrounding area due to the influence of the bias magnetic field.
A magnetization pattern is formed according to the information.

Information recorded in this manner can be optically read out using the well-known magneto-optic effect by irradiating the medium with a low-power unmodulated beam. Furthermore, recorded information can also be erased by applying a magnetic field in the opposite direction to the bias magnetic field during recording.

An example of the arrangement of optical components of a conventional magneto-optical head is shown in FIG.

Below, the light beam emitted from the semiconductor laser 2 is RF
The optical path leading to the detector 4 will be explained using arrows.

As shown in FIG. 6, the light beam emitted from the semiconductor laser 2 is transmitted from the collimator lens 6 to the beam shaping prism 8.
→Pus l O→Mirror 12→Objective lens 14. The light is then irradiated onto the 16th surface of the disk. The light beam reflected on the surface of the disk 16 is transmitted through the objective lens 14←mirror 12→2.
The light passes through several condenser lenses 18 and is divided into two parts by a PBS 20. One of the light beams separated by the PB820 enters the detector 22, and the other light beam is split by the PB820.
824 and is further divided into two parts, each of which enters the RF detector 4.

Autofocusing (X
direction) and auto-tracking (y direction).

Also, by finding the difference between the signals detected by the two RF detectors 4, the information recorded on the surface of the disk 16 is read.

Furthermore, in the past, the size perpendicular to the disk, that is, the height of the device, was not much of an issue as in the conventional example above, but magneto-optical disks are known to have rewritable information. Since it is capable of high-density recording, it is expected to replace magnetic disks.

[Background of the invention]

However, in order for magneto-optical disks to replace magnetic disks, magneto-optical disks must at least reach the full-hide size of 51/4-inch disk drives (height: 82 m, width: 146 m, depth: 203 to 206 m), which is the mainstream of magnetic disks. Equipment must be made smaller. Therefore, it has become necessary to arrange and design optical components in consideration of miniaturization of the magneto-optical head.

In addition, in the case of a rotary sliding deaf objective lens driving device 26 as shown in FIG. 7, optical components such as a beam shaping prism 32, a collimator lens 34, and a semiconductor laser are installed only on the objective lens 30 side when viewed from the rotation center axis 28. 36th grade is placed,
The space on the opposite side of the objective lens 30 when viewed from the central axis of rotation 28 is not used, resulting in a wasted space when attempting to downsize the optical head.

〔the purpose〕

The present invention is based on the above-mentioned prior art, and its purpose is to reduce the size and weight of an optical head provided in an optical information recording/reproducing device.

[Summary of the invention]

According to the present invention, the above object is an optical head that irradiates a light beam onto an information recording medium, the optical head having an optical system that focuses the light beam on the information recording medium,
An optical head, characterized in that the optical path of the light beam to the optical system is configured such that it enters from a direction opposite to the optical system across support means for supporting the optical system. achieved.

〔Example〕

Embodiments of the present invention will be explained in detail below with reference to the drawings. FIG. 1 is a schematic perspective view showing an embodiment of the optical head of the present invention.

The illustrated 40ti disk is rotatably supported by a drive device (not illustrated). Information tracks 42 are formed on the disc 40. An objective lens 44 is provided below the disk 40. The objective lens 44 is arranged in the illustrated X direction (focusing direction) and y direction.
It is supported movably in the direction (tracking direction) by a driving means (not shown). The number 46 is the center line of a rotation center axis (not shown) that supports the movement of the objective lens 44 in the y direction. The center line 46 is located between the illustrated semiconductor laser 48 and collimator lens 50, and the objective lens 44.

Below, the light beam emitted from the semiconductor laser 4B is R
The optical path leading to the F detector 52 will be explained using arrows.

As shown in FIG. 1, the light beam emitted from the semiconductor laser 48 is transmitted through the collimator lens 50 → beam shaping prism 54 → PBS 56 → mirror 58 → objective lens 44,
The light is then irradiated onto the disk 40 surface. The light beam reflected on the surface of the disk 40 is transmitted through the objective lens 44←mirror 58.
→The light passes through two condensing lenses 60 and is divided into two by a PBS 62. One of the light beams separated by the PBS 62 is the sir? the other light beam l
-j It enters the PBS 66 and is further divided into two parts, each of which enters the RF detector 52.

Auto-focusing (in the X direction) and auto-tracking (in the y-direction) of the objective lens 44 are performed based on the signal detected by the laser detector 64 in the optical path. Furthermore, by determining the difference between the signals detected by the two RF detectors 52, information recorded on the surface of the disk 40 is read.

In the optical head of this embodiment, the center line 46 of the rotation center axis that supports the movement of the objective lens 44 in the tracking direction is located between the semiconductor laser 48 and the collimator lens 50, and the objective lens 44. The entire head can be made smaller and lighter.

Next, a second embodiment of the present invention will be described using FIG.

FIG. 2 is an exploded perspective view showing a second embodiment of the optical head of the present invention.

In the embodiment of FIG. 2, 70 shown is an objective lens. The lens 70 is held by an objective lens holding member 72. A focusing coil 74 is wound around the side of the holding member 72, and four tracking coils 76 are provided on the focusing coil 74.

A counterweight 78 is provided on the objective lens holding member 72 to balance the center of gravity. The lower part of the weight 78 is connected to one end of a neutral holding rubber 80, and the other end of the neutral holding rubber 80 is fixed to a base 82. Two permanent magnets 84 are provided on the base 82 so as to face each other. Further, the illustrated reference numeral 86 is a yoke.

A rotation center shaft 88 is fixed and protrudes from the center of the base 82 . A bearing 90 provided on the objective lens holding member 72 is fitted onto the central shaft 88 so as to be slidable and rotatable.

The objective lens holding member 72 is movable in the illustrated X direction (focusing direction) and Y direction (tracking direction) by electromagnetic interaction between a focusing coil 74, a tracking coil 76, and a permanent magnet 84. .

In this embodiment, below the objective lens driving device as described above, a combination of the mirror 58, PBS 56, and beam shaping prism 54 shown in FIG. 1 is arranged.

Further, since the semiconductor laser 48 and the collimator lens 50 are provided at the positions shown in the figure, the structure is such that the light beam is incident from opposite directions across the rotation center when viewed from the objective lens 70. In addition, 62 and 66 shown in the figure are P
BS, 64 is a detector, and 52 is an RF detector.

In the above embodiment, an example was given in which the mirror, PBS, and beam shaping prism were integrated, but the present invention is also applicable to structures in which the mirror, PBS, and beam shaping prism are integrated.

Although FIG. 2 shows an example of a sliding type that rotates around the central axis of rotation 88, as shown in FIG. It can be passed from the direction of the rotation center 100 for tracking, and can be an embodiment of the present invention.

Further, as shown in FIG. 4, a base 102 that constitutes a magnetic circuit
The part where the rotational center shaft 104 is press-fitted is not affected by the magnetic circuit, so this part is cut out and the mirror 106, PB
It is also possible to arrange S, etc.

Further, as shown in FIG. 5, a light beam passage hole 11 through which a movable member 112 including an objective lens 110 passes a light beam
Furthermore, in the case of an objective lens drive device having a pressure of 4, it is possible to further reduce the size and weight of the optical head including the objective lens drive system.

Further, in this explanation, the magneto-optical optical head has been mainly explained, but it goes without saying that the embodiments of the present invention are sufficiently effective in the case of optical disks as well.

〔Effect of the invention〕

As described above in detail and specifically, the present invention provides a method in which the optical path of the light beam to the objective lens that focuses the light on the information recording medium is from the opposite direction across the support means that supports the objective lens. Since the optical head is configured to allow light to enter, the optical head can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of the optical head of the present invention, FIG. 2 is an exploded perspective view showing a second embodiment of the invention,
3 is a perspective view showing another embodiment of the invention, FIG. 4 is a sectional view showing another embodiment of the invention, FIG. 5 is a perspective view showing another embodiment of the invention, and FIG. 6 is a perspective view showing another embodiment of the invention. The figure is a schematic oblique view showing a conventional optical head, and FIG. 7 is a perspective view showing a conventional objective lens driving device. 40...Disc, 44...Objective lens, 48...
・Semiconductor laser, 50...collimator lens. Agent Patent Attorney Jo Taira Yamashita Figure 1 Figure 2 Figure 6 Figure 7

Claims (1)

[Claims] (1) In an optical head that irradiates a light beam onto an information recording medium, the optical head has an optical system that focuses the light beam on the information recording medium, and the optical path of the light beam to the optical system is An optical head characterized in that the optical head is configured such that light enters from the direction opposite to the optical system across support means for supporting the optical system.