JPH05135400A - Optical head - Google Patents

Abstract

PURPOSE:To lighten the movable part of an optical head and to improve an access speed by deflecting these optical paths between an objective lens and an optical system containing a laser light source and a light receiving means and making to coincide reciprocal optical axies by a fixed deflection means. CONSTITUTION:Between a fixed optical system 7 containing the laser light source 8, a photodetector 9 and an objective lens 6 driven in the direction of seeking, a thin type prism body 10 is provided which deflects these optical paths and whose incident plane 10a is prolonged and present in the movable range of the movable part 5. The optical axis from the optical system 7 is deflected 90 degree by the prism 10, and a transparent plate is rotated in accordance with the position of the movable part 5 by a radial direction driving part 14 and the optical path of the incident/emitting light beam of the optical system 7 is moved in parallel. Then, by using the prism body 10 deflecting 90 degree even when the angle forming with the optical path is smaller than 45 degree, the volume of the optical head is reduced. Thus, the movable part of the optical part 4 is lightened and the access speed is improved, and a device is thinned and miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head, and more particularly to an optical axis of an objective lens facing a recording surface of an optical recording medium,
The present invention relates to an optical head in which both are arranged at a position where the optical axis of a fixed optical system including a laser light source is not coaxial with each other.

[0002]

2. Description of the Related Art Conventionally, there is an optical recording device for transmitting / receiving data to / from an optical recording medium such as an optical disk or a magneto-optical disk. An optical head for accessing the recording surface of such an optical recording medium has an optical system including a laser light source, a light receiving unit, etc., and an objective lens facing the recording surface of the optical recording medium. Seek operation.

However, the access speed of the optical head of the optical recording apparatus is lower than that of the fixed magnetic disk apparatus. Therefore, the access speed is improved by improving the optical head for accessing the recording surface of the optical recording medium. Various proposals have been made.

For example, in Japanese Patent Laid-Open No. 2-206032, an optical system including a laser light source and a light receiving unit is fixed, an objective lens facing a recording surface of an optical disc, a focus adjustment actuator for the objective lens, and an objective lens. A deflection means such as a mirror for deflecting these optical paths between the lens and the light receiving system so that their optical axes coincide with each other is integrally mounted, and this is movable in the radial direction of the optical disk, that is, the seek direction. There is disclosed an optical head which is supported by the actuator and driven by an actuator.

Further, in Japanese Patent Laid-Open No. 1-307930, the optical system is fixed in the same manner as described above, the objective lens and the deflecting means are integrally attached, and this is supported by an arm extending in the seek direction. A flying type in which the arm is driven in the seek direction by a voice coil motor, and the objective lens and the deflecting means are always levitated at a predetermined distance from the recording surface by the airflow generated when the optical disc rotates. A head is disclosed.

According to each of the above-mentioned structures, the access speed is improved as the optical head is made relatively lightweight. However, in actuality, any structure has not reached the access speed of the existing fixed magnetic disk drive.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and its main purpose is to provide an optical recording apparatus capable of improving the access speed. To provide the head.

[0008]

According to the present invention, there is provided an optical head which seeks on a recording surface of an optical recording medium to transfer data to and from the optical recording medium. An objective lens that moves the recording surface in a seek direction and faces the recording surface; a fixed optical system that has an optical axis that is not coaxial with the optical axis of the objective lens and that includes a laser light source and a light receiving unit; A fixed optical system and a fixed deflecting means provided over the entire moving range of the objective lens for deflecting irradiation light or reflected light from one of the objective lens toward the other. This is accomplished by providing a featured optical head.
In particular, the optical axis of the fixed optical system and the optical axis of the objective lens form a right angle, the deflecting means has an entrance surface and an exit surface on the same plane, and the angle θ ₁ with the entrance / exit surface is inside. the prism of refractive index n having a reflecting surface forming a light input and output angle of the light axis of the fixed optical system for entering-emission surface as theta _2,

[0009]

[Equation 3]

And

[0011]

[Equation 4]

It is preferable that it is arranged at a position such that

[0013]

As described above, the optical head is movable by fixing the deflecting means for deflecting the optical paths of the objective lens and the optical system including the laser light source and the light receiving means so that their optical axes coincide with each other. The weight is reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a side sectional view showing the structure of the main part of an optical disk device according to the first embodiment of the present invention.

This optical disk device has a spindle motor 3 for holding and rotating an optical disk 1 as an optical recording medium with a holder 2 and an optical head for transmitting and receiving data to and from a recording surface 1a of the held optical disk 1. 4 and. The optical head 4 is connected to a signal processing unit (not shown) and a control unit for driving and controlling a movable portion of the head.

The optical head 4 is movable in a seek direction with respect to the optical disc 1, that is, in a left-right direction parallel to the paper surface in FIG. 1, an objective lens 6 attached to the movable part 5, and the optical disc 1. A fixed optical system 7 including a laser light source 8 for irradiating the recording surface 1a with a laser beam and a light receiving element 9 for receiving reflected light from the optical disc 1 side; a fixed optical system 7 and an objective lens 6; The thin prism body 10 has an entrance / exit surface 10a, which will be described later, extending over the entire movable range of the movable portion 5 as a light deflecting means. Here, the optical axis of the light entering and exiting the fixed optical system 7 and the optical axis of the light passing through the objective lens 6 are arranged so as to be orthogonal to each other. That is, the fixed optical system 7
The optical axis of light entering and exiting the optical disk is the recording surface 1 of the optical disk 1.
The optical axis of light that extends in parallel with a and passes through the objective lens 6 extends perpendicularly to the recording surface 1a.

In the fixed optical system 7, a deflection beam splitter 12, a λ / 4 plate 13 and a radial direction drive section 14 which will be described later are arranged from the laser light source 8 side.
The light from the disk is transmitted and supplied toward the optical disk 1, and the reflected light from the disk 1 is deflected toward the light receiving element 9.

The movable portion 5 is provided with a focusing driving portion 15 for driving the objective lens 6 in the focusing direction, that is, the vertical direction in FIG. The movable portion 5 is driven in the seek direction by an actuator (not shown).

As shown in FIG. 2, the thin prism body 1
In 0, the incident surface and the exit surface of the light are the same,
Further, it has a reflecting surface 10b forming an angle θ ₁ with the entrance / exit surface 10a. Further, in this thin prism body 10, the incident / emission surface 10a described above is arranged such that the incident angle of the optical axis of the light emitted from the fixed optical system 7 or the light incident on the fixed optical system 7 forms an angle θ _2. It is arranged. Here, since the angle formed by the optical axis of the objective lens 6 and the optical axis of the incident / emitted light of the fixed optical system 7 is set to 90 °, the angle θ between the incident / emitted surface 10a and the reflecting surface 10b described above. ₁ and the incident angle θ of the optical axis of the light from the fixed optical system 7 with respect to the entrance / exit surface 10a.
The relationship between ₂ and the refraction angle θ ₃ is that the refractive index of the thin prism body 10 is n,

[0021]

[Equation 5]

And

[0023]

[Equation 6]

It becomes Expanding the equation of Equation 6 above,

[0025]

[Equation 7]

[0026] here,

[0027]

[Equation 8]

Therefore, the equations (5) and (8) are added to the equation (7).
Substituting the equation for and eliminating θ ₃ ,

[0029]

[Equation 9]

It becomes Organize this,

[0031]

[Equation 10]

Further, the angle θ ₂ is considered to be superior to an ordinary mirror,

[0033]

[Equation 11]

As a result, by arranging the thin prism body 10 at a position satisfying the equations (10) and (11), the optical axes become orthogonal to each other. For example, a normal mirror is placed on each optical axis. Compared with the case where the recording device is arranged at an angle of 45 °, the bulkiness of the recording device main body in the direction orthogonal to the recording surface 1a becomes smaller, and the device becomes thinner and smaller. Here, since the entrance / exit surface 10a of the thin prism body 10 is inclined, when the movable portion 5 moves in the seek direction, the optical axis of the objective lens 6 moves in parallel depending on the position, and the fixed optical system 7 moves. It may be considered that the optical axes of the incoming and outgoing lights do not coincide with each other, but in the present embodiment, this is adjusted by the radial direction drive section 14 in the fixed optical system 7. That is,
The transparent plate member is rotated in accordance with the position of the movable portion 5, and the optical axis of the incident / emitted light with respect to the fixed optical system 7 is moved in parallel.

When the seek operation is actually performed on the optical disk 1, the movable portion 5 moves in the seek direction by a command from a control system (not shown), and the radial direction drive portion 1 is accordingly moved.
4 rotates according to the position of the movable part 5, and the laser light emitted from the laser light source 8 is deflected by the deflection beam splitter 12, λ /
4 plate 13, radial direction driving unit 14, thin prism body 1
The recording surface 1a is spot-irradiated via 0 and the objective lens 6, and the reflected light is incident on the fixed optical system 7 along the same path, is reflected by the deflecting beam splitter 12, and is received by the light receiving element 9.

Therefore, in this embodiment, since only the objective lens 6 and its focus direction drive unit 15 are mounted on the movable portion 5 in actuality with the seek operation, the weight is reduced and the seek operation is performed in the conventional manner. Compared to this, it can be performed at high speed.

FIG. 3 is a view similar to FIG. 1 showing a second embodiment to which the present invention is applied. The same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be given. The description is omitted.
In this embodiment, a floating optical head is used as the movable part. That is, the objective lens 6 is held on the floating substrate 21 that is levitated by the air flow accompanying the rotation of the optical disc 1. In addition, the floating board 21 includes a leaf spring arm member 22.
Is supported so as to be movable in the focusing direction, that is, the vertical direction in FIG. The arm member 22 is driven by the voice coil motor 23 in the seek direction.

On the other hand, in the fixed optical system 27, the first
A radial drive unit 14 and a λ / 4 plate 1 similar to the embodiment of FIG.
A fine focusing drive unit 25 is provided between the drive unit 3 and the control unit 3. This is composed of a lens arranged to finely adjust a focusing error in the floating optical head and a driving unit thereof. In this embodiment, as compared with the first embodiment, the weight of the movable portion is reduced by the amount of the focusing drive portion omitted, the responsiveness when moving in the seek direction is further improved, and the access speed is improved. ing. The other structure is the same as that of the first embodiment.

FIG. 4 shows first and second embodiments to which the present invention is applied.
FIG. 8 is a side sectional view of a main part showing a modified example of the above example. In this embodiment, a reflective hologram member 37 is used instead of the thin prism body in the first and second embodiments. The hologram member 37 has a reflection angle of 90 ° when the angle formed by the optical axis of the incident / emitted light with respect to the fixed optical system 7 and the hologram reflection surface 37a is θ4. Therefore, according to the present embodiment, the height direction of the device, that is, FIG. 1 or FIG. 2 is higher than that of the first and second embodiments.
The vertical bulkiness of the device is reduced, and the size of the entire device is further reduced.

In each of the above embodiments, the deflection means 90
Although a thin deflecting means for deflecting the optical axis is used, an ordinary mirror or the like may be arranged actually. In this case, in each of the above-described embodiments, the contour shape of the incident / emitted light with respect to the fixed optical system and the contour shape of the light irradiated on the optical disk and reflected are the same.

Further, in each of the above embodiments, when the laser light emitted from the light source 8 is deflected by the deflecting means, the light is simultaneously supplied over the entire moving range of the movable portion, so that the laser light is contoured. If the laser beam is shaped into an elliptical shape with a shaping prism or the like, it is possible to omit the radial direction driving unit and use only the laser light that passes through the objective lens 6, reducing the number of parts and controlling. It will be easier. However, it goes without saying that it is necessary to increase the output of the light source in this case.

[0042]

As is apparent from the above description, according to the optical head of the present invention, the fixed optical system including the laser light source and the light receiving means and the objective lens driven in the seek direction are provided. By providing a fixed deflecting means over the entire moving range of the objective lens so as to deflect the optical path and make the optical axes coincide with each other, it is possible to reduce the weight of the movable portion of the optical head and improve the seek speed, Access speed is improved. Further, by using, as the deflecting means, a thin deflecting means capable of deflecting light by 90 ° even if the angle formed by the optical axis of the incident / emitted light with respect to the fixed optical system is smaller than 45 °, an optical recording apparatus is provided. The bulkiness in the direction orthogonal to the surface of the optical recording medium can be reduced, and the device can be thinned and downsized.
From the above, the effect of the present invention is great.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of a main part of an optical recording device in a first embodiment to which the invention is applied.

FIG. 2 is an enlarged side sectional view for explaining the configuration and arrangement of the deflecting means in FIG.

FIG. 3 is a side sectional view similar to FIG. 1, showing a second embodiment to which the present invention is applied.

FIG. 4 is an enlarged side sectional view of deflecting means showing a modified example of the first and second embodiments.

[Explanation of symbols]

 1 Optical Disc 1a Recording Surface 2 Holder 3 Spindle Motor 4 Optical Head 5 Movable Part 6 Objective Lens 7 Fixed Optical System 8 Light Source 9 Light-Receiving Element 10 Thin Prism Body 10a Inlet / Outgoing Surface 10b Reflecting Surface 12 λ / 4 Plate 13 Deflection Beam Splitter 14 Radial Directional drive unit 15 Focusing drive unit 21 Floating substrate 22 Arm member 23 Voice coil motor 25 Fine focusing drive unit 27 Fixed optical system 37 Reflective hologram member 37a Holographic reflection surface

Claims (5)

[Claims] 1. An optical head for performing a seek operation on a recording surface of an optical recording medium to exchange data with the optical recording medium, wherein the recording surface is moved in the seek direction and at the same time as the recording surface. Opposing objective lens, fixed optical system having an optical axis which is not coaxial with the optical axis of the objective lens, and including a laser light source and a light receiving means, and irradiation from any one of the fixed optical system and the objective lens An optical head comprising: fixed deflecting means provided over the entire moving range of the objective lens for deflecting the light or the reflected light toward the other. 2. The optical axis of the fixed optical system and the optical axis of the objective lens form a right angle, and the deflecting means has an incident surface and an exit surface that are the same surface, and has the entrance and exit surfaces inside. A prism body having a refractive index n having a reflecting surface forming an angle θ ₁ is defined as follows, where θ ₂ is an incident / emission angle of the optical axis of the fixed optical system with respect to the incident / emission surface. And, and The optical head according to claim 1, wherein the optical head is arranged at a position such that 3. The optical head according to claim 1, wherein the deflecting means comprises a hologram that emits incident light at an angle formed by the optical axis of the fixed optical system and the optical axis of the objective lens. .. 4. A second deflecting device is provided between the objective lens and the fixed optical system, is driven to follow the objective lens, and has a deflecting direction that changes in accordance with the driven position. The optical head according to any one of claims 1 to 3, wherein: 5. The light emitted from the laser light source is
The optical head according to any one of claims 1 to 3, wherein the entire range of movement of the objective lens is simultaneously irradiated via the deflecting unit.