JPH05250698A - Optical head device - Google Patents

Abstract

PURPOSE:To improve high speed accessibility of the optical head device. CONSTITUTION:A rotational body 52 is composed of a fixed part 53, a connecting part 54 and movable part 55 altogether, rotatively arranged around an axis 14 and transfers the movable part 55 in the radial direction of the optical disk 12. An objective lens 56 and a mirror 58 are fixed and arranged on the movable part 55 as the optical system of the movable part 91. A mirror 80, a 1/4 wave plate 82, a collimator lens 62, beam splitter 64, a laser diode 60, a condenser lens 84 and a PIN photodiode 86 are arranged on the fixed part 53 as the optical system of the fixed part 90. By driving the collimator lens 62 so as to move in the direction of the optical axis by means of a focusing actuator 88, the focusing control is carried out. Since the movable part 55 unnecessitates the focusing actuator, the movable part becomes light in weight and accelerated accessibility is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device in an optical disk device such as an optical disk device and a magneto-optical disk device, which has improved high-speed accessibility.

[0002]

2. Description of the Related Art Since a conventional optical head device has a structure in which the whole is integrally transferred in the disk radial direction, it has large inertia and poor high-speed accessibility. The separate type optical head solves such a problem of the conventional apparatus.
As shown in FIG.
The movable portion 38 is provided with an objective lens 42, a prism 44, a focus actuator 41 for moving the objective lens 42 in the disc surface direction, and the like.
A laser diode, a photodiode, or the like is arranged at 0, and these are optically connected through a space, and the movable portion 3
Only No. 8 moves in the radial direction of the optical disk 46. With such a configuration, the movable portion 38 can be made lighter, and thus high-speed accessibility is improved.

As a swing arm type optical head device of a separate type, there is proposed a separate type optical head of Japanese Patent Application No. 2-238242 filed by the present applicant. FIG. 3 is a specific example thereof. This optical head device 50
Has a rotating body 52. The rotating body 52 is the fixed portion 5.
3, the connecting portion 54 and the movable portion 56 are integrally connected. The rotating body 52 passes through the center of the fixed portion 53 and uses the axis 14 perpendicular to the recording surface of the optical disc 12 as a fulcrum,
It is arranged rotatably in the disc radial direction in a plane substantially parallel to the disc surface. A tracking coil 22 is attached in the middle of the connecting portion 54, and a fixed rail 24 made of a magnet is passed through the tracking coil 22 to form a linear motor. ..

The internal structure of the rotating body 52 is shown in FIG. Further, its plan view is shown in FIG. The rotating body 52 is supported rotatably about the axis 14 as a fulcrum by a bearing 74 attached to a fixed portion 72 such as a chassis of the optical disk device.

An objective lens 56, a mirror 58, a focus actuator 51 for moving the objective lens 56 in the disk surface direction, and the like are arranged in the movable portion 55.

In the fixed portion 53, the laser diode 6
0, a collimator lens 62, a prism 64, a PIN photodiode 66, a balancer (weight) 68 for balancing, and the like, and rotate together with the rotating body 52.

The connecting portion 54 is composed of a hollow pipe having high rigidity and small deflection, and its internal space constitutes an optical path 70 which optically connects the movable portion 55 and the fixed portion 53.

According to the above configuration, the laser diode 60
The laser beam 76 emitted from the collimator lens 62
Are collimated into parallel light, are totally reflected by the front reflection surface 64a of the prism 64, and are guided to the optical path 70 in the connecting portion 54. Then, it is reflected by the mirror 58 in the movable portion 55 and is irradiated onto the recording surface 12 a of the optical disk 12 via the objective lens 56. Then, the reflected light enters the objective lens 56, is reflected by the mirror 58, returns through the optical path 70, is reflected by the half mirror surface 64 b of the prism 64, and is received by the PIN photodiode 66. Based on the received light signal, reproduction of disc recording information, tracking error detection by the push-pull method, focus error detection by the knife edge method, etc. are performed.

Access to the target address is performed by supplying a control signal for access to the tracking coil 22. At this time, the movable portion 55 makes a large movement around the axis 14 required for access, but there is only the objective lens 56 and the mirror 58 there, and the other optical system is in the fixed portion 53, and the movement is small. Therefore, the rotary body 52 as a whole has a small effective mass and a small inertia, so that high-speed access (for example, access time 40 to
60 ms) is possible.

Further, since the optical systems 56, 58 and the like in the movable portion 55 and the optical systems 60, 62, 64 and 66 and the like in the fixed portion 53 move integrally, they are rotated by a rotation as compared with the system of FIG. No deviation of the optical axis of the optical path 70 occurs. Furthermore, the rotating body 52
Since it is a circular motion, it can be supported by a shaft, and it can be easily supported and has a simple structure.

[0011]

According to the separation type optical head device of FIGS. 2 and 3, the focus actuator 4 is used.
1, 51 must be arranged in the movable part 55 to drive the objective lenses 42, 56. For this reason, the coils, coil bobbins, permanent magnets, and the like that form the focus actuators 41 and 51 are present in the movable portions 38 and 55, and there is a limit to weight reduction, and high-speed access as hard disks cannot be realized.

The present invention intends to solve the above problems in the prior art and to provide an optical head device which is lighter than the conventional separation type optical head device and has improved high-speed accessibility. It is a thing.

[0013]

According to the present invention, there is provided a movable part which is arranged in an optical disk device so as to be movable in a disk radial direction in a plane substantially parallel to the disk surface, and the movable part which is separated from the movable part. A fixed portion disposed on the fixed portion, and at least a light source that emits a recording beam or a reproducing beam to the movable portion, which is disposed on the fixed portion, and that receives the disc reflected beam returned from the movable portion. A fixed part optical system having a collimator lens and a photodetector, and a fixed part disposed in the movable part in the focus direction, and a recording beam or a reproducing beam emitted from the fixed part is incident and irradiated on the disc surface. And, by changing the relative distance between the light source and the collimator lens, the movable part optical system which returns the reflected beam to the fixed part and has at least an objective lens, Recording beam or those formed by and a focus actuator for changing the focused position of the beam spot of the reproducing beam is Isa.

[0014]

The collimator lens is usually used for collimating the beam from the light source, but in the present invention, the relative distance between the light source and the collimator lens is changed. The emitted beam becomes non-parallel, the focus position of the beam emitted from the objective lens changes, and focus adjustment is performed. According to this, since the objective lens may be fixedly arranged in the focus direction, the movable portion does not need a focus actuator, and the movable portion can be reduced in weight by that amount to improve high-speed accessibility. Average access time is also feasible.

[0015]

FIG. 1 shows an embodiment in which the present invention is applied to a swing arm type optical head device. 1A is a side sectional view showing the internal structure, and FIG. 1B is a plan view. The external appearance is the same as that shown in FIG. 3 except that the objective lens 56 is fixed to the movable portion 55.

In FIG. 1, the optical head device 100 has a rotating body 52. The rotating body 52 is configured by disposing a fixed portion 53 and a movable portion 55 separately, and connecting them integrally by a connecting body 54. The rotating body 52 is supported by a bearing 74 attached to a fixed portion 72 such as a chassis of the optical disk device, and is thereby rotatable about the axis 14 which passes through the center of the fixed portion 53 and is perpendicular to the recording surface of the optical disk 12 as a fulcrum. The movable portion 56 is arranged so as to be rotatable in the disc radial direction in a plane substantially parallel to the disc surface. The tracking coil 22 is provided in the middle of the connecting portion 54.
Is attached, and the fixed rail 24 composed of a magnet is passed through the linear motor to form a linear motor, and the rotary body 52 is driven in the disk radial direction around the axis 14 to perform feed (feed control) and tracking control. To do.

In the movable part 55, an objective lens 56 and a mirror 58 are fixedly arranged as a movable part optical system 91. A laser diode 60 (light source), a beam splitter 64, a collimator lens 62, a PIN photodiode 86 (photodetector), and a focus actuator 88 are provided in the fixed portion 53 as a fixed portion optical system 90. In addition, a balancer (weight) for balancing 6
8 and the like are arranged and rotate together with the rotating body 52. The collimator lens 62 is supported by a suspension and is movable in the vertical direction (optical axis direction). Other optical components 60,
All of 64, 82, 80, 84 and 86 are fixedly arranged.

The connecting portion 54 is formed of a lightweight hollow pipe having high rigidity and small deflection, and its internal space constitutes an optical path 70 which optically connects the movable portion 55 and the fixed portion 53.

A specific example of the focus actuator 88 is shown in FIG. This uses a conventional focus actuator that drives an objective lens. The collimator lens 62 is supported by the suspension 92 and is movable in the optical axis direction 94. The collimator lens 62 is attached to the coil bobbin 94, and the focus coil 96 is wound around the outer peripheral surface of the coil bobbin 94. The coil bobbin 94 is arranged in a ring-shaped magnetic circuit composed of the magnet 98 and the core 102. And P
The collimator lens 62 is driven in the optical axis direction by supplying the focus coil 96 with a current corresponding to the focus error obtained by calculating the light reception signal of the IN photodiode 66. The laser light is the hollow portion 1 of the core 102.
Pass 02a.

According to the above configuration, the laser diode 60
The laser beam 76 emitted from the
And is made into a state close to parallel light by the collimator lens 62, and is guided to the optical path 70 in the connecting portion 54 via the quarter-wave plate 82 and the mirror 80. And the movable part 55
It is reflected by the inner mirror 58 and is irradiated onto the recording surface 12 a of the optical disk 12 via the objective lens 56. And
The reflected light 76 ′ is incident on the objective lens 56, reflected by the mirror 58, and returned through the optical path 70 to the mirrors 80, 1.
The light is reflected at a right angle by the beam splitter 64 via the / 4 wavelength plate 82 and the collimator lens 62, and is received by the PIN photodiode 66 via the condenser lens 84. On the basis of this received light signal, reproduction of disc recording information, tracking error detection by push-pull method, 3-beam method, etc., focus error detection by knife edge method, astigmatism method, etc. are performed.

The focus control operation by the collimator lens 62 will be described. In the state of FIG. 1A in which the distance between the disc recording surface 12a and the objective lens 56 matches a predetermined reference distance (here, it is assumed to be equal to the focal length of the objective lens 56), the collimator lens 62 is The position of the laser diode 60 is controlled so that the light emitting position of the laser diode 60 coincides with the focal position of the laser diode 60. At this time, the collimator lens 6
The laser light 76 emitted from the laser beam 2 is a parallel light beam, and is passed through the objective lens 56 and is at the focal position thereof.
The beam spot 110 is focused on 2a.

From this state, when the distance between the disk recording surface 12a and the objective lens 56 is increased as shown in FIG. 7A, the focus error signal causes the focus actuator 88 to move the collimator lens 62 downward (laser diode 60). Move (in the direction closer to). As a result, the laser light 76 emitted from the collimator lens 62 becomes divergent light, and the position where the beam spot 110 converges moves away from the focal position of the objective lens 56, and the disc recording surface 1
Focus on 2a.

When the distance between the disk recording surface 12a and the objective lens 56 approaches as shown in FIG. 7B, the focus actuator 88 is activated by the focus error signal.
Moves the collimator lens 62 downward (laser diode 6
Move it away from 0). As a result, the laser light 76 emitted from the collimator lens 62 becomes convergent light,
The position where the beam spot 110 converges is the objective lens 56.
The focal point is closer to the focal point of the disk and the light is focused on the disk recording surface 12a. In this way, the focus control by the collimator lens 62 is performed.

The access to the target address is performed by supplying a control signal for access to the tracking coil 22. At this time, the movable portion 55 makes a large movement around the axis 14 required for access, but there is only the objective lens 56 and the mirror 58 there, and the focus actuator 88 and other optical systems are in the fixed portion 53. The movement is small. Therefore, since the rotary body 52 as a whole has a small effective mass and a small inertia, high-speed access close to that of a hard disk becomes possible.

[0025]

[Modification] In the above embodiment, the beam emitted from the collimator lens is set to parallel light in a state where the distance between the objective lens and the recording surface of the optical disc is at the reference distance. It can also be set.

Further, the arrangement of the fixed part optical system is not limited to that shown in FIG. 1, and it may be arranged as shown in FIG. If the arrangement is such that the laser light passes back and forth through the collimator lens as shown in FIGS. 1 and 8, there is no beam movement on the photodetector due to the movement of the collimator lens, and the photodetector or the like is moved in accordance with the movement of the collimator lens. You don't have to move it.

Further, the laser diode (light source) can be moved instead of moving the collimator lens 62. The point is that the relative distance between the collimator mens and the light source should change.

In the above embodiment, the tracking coil 22 and the fixed rail 24 are used for both feed control and tracking control, but a tracking actuator may be separately provided for independent tracking control. In that case, the tracking actuator can be arranged on the objective lens side, but if it is arranged on the collimator lens side, the weight of the movable portion does not increase.

Further, the present invention can be applied to optical head devices of various types such as a three-beam type and a one-beam type,
Further, the feed system is not limited to the swing arm system, and can be applied to various systems such as the linear slide system shown in FIG. Further, it can be applied to any of a recording device, a reproducing device recording, and a reproducing combined device.

[0030]

As described above, according to the present invention, the focus control is performed by the collimator lens in the fixed portion, so that the objective lens may be fixedly arranged in the focus direction, so that the movable portion is not provided in the movable portion. The focus actuator is no longer required, the movable part can be lightened accordingly, and high-speed accessibility can be improved, and access time comparable to that of a hard disk can be realized.

Further, since the focus actuator is arranged in the fixed portion, there are few restrictions on the magnetic circuit configuration of the focus actuator, the degree of freedom is increased, the space in the fixed portion can be effectively used, and the stability as the focus actuator is increased.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a side view showing a linear slide type separation type optical head device.

FIG. 3 is a perspective view showing a swing arm type separation type optical head device.

FIG. 4 is a side view showing a conventional swing arm type separated optical head device.

FIG. 5 is a plan view of FIG.

6 is a side sectional view showing a specific example of the focus actuator of FIG.

7 is a side view showing a focus control operation by the optical head device of FIG. 1. FIG.

FIG. 8 is a side view showing another arrangement example of the fixed part optical system.

[Explanation of symbols]

 12 optical disk 53 fixed part 55 movable part 56 objective lens 60 laser diode (light source) 62 collimator lens 76 laser light (recording beam or reproducing beam) 76 'disk reflected beam 86 PIN photodiode (photodetector) 88 focus actuator 90 Fixed part optical system 91 Movable part optical system 100 Optical head device 110 Beam spot

Claims (1)

[Claims] 1. A movable part arranged in the optical disk device so as to be movable in the disk radial direction in a plane substantially parallel to the disk surface, and a fixed part arranged in the optical disk device separately from the movable part. It has at least a light source, a collimator lens, and a photodetector which are disposed on the fixed part and emit a recording beam or a reproducing beam to the movable part and which makes the disc reflected beam returned from the movable part incident. A fixed part optical system and a fixed part fixed to the movable part in the focus direction so that the recording beam or the reproducing beam emitted from the fixed part is incident on the disk surface and the reflected beam is fixed. And a recording beam emitted from the objective lens by changing the relative distance between the light source and the collimator lens. Is an optical head device comprising a focus actuator for changing the focus position of the beam spot of the reproducing beam.