JP2000132858A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup capable of enhancing an access speed with respect to a recording medium by reducing the size of an optical head with a simple constitution. SOLUTION: This optical pickup is provided with a laser light source 2, a collimating lens 4 making laser beams emitted from the laser beam source 2 a parallel luminous flux, a relay lens 12 converging the laser beams made to be the parallel luminous flux by this collimating lens 4, an imaging lens 14 making the laser beams converged by this relay lens 12 a parallel luminous flux, an optical head 16 converging the laser beams made to be the parallel luminous flux by this imaging lens 14 on a recording medium 22 and a deflection optical device 10 deflecting the laser beams being converged on the recording medium by this optical head 16, and the diameter of the luminous flux of the laser beams made to be the parallel luminous flux by the imaging lens 14 is more reduced than that of the luminous flux of the laser beams made to be the parallel luminous flux by the collimating lens 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup for performing optical recording or optical reproduction of information on a recording medium.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-5-174417 and JP-A-5-159316 disclose a technique using this kind of optical pickup. For example, as shown in FIG. 5, in an optical pickup, a laser beam emitted from a laser light source (for example, a semiconductor laser) 2 is converted into a parallel light beam by a collimating lens 4, and then substantially rounded by beam shaping prisms 6 and 8. Shaped into shape. The laser light shaped into a substantially perfect circle is a deflecting optical element (for example,
(Galvanomirror) After reflecting from 10, relay lens 1
After being converged by 2 and forming a focal point F, it diverges again and irradiates the imaging lens 14. The imaging lens 14 converts the divergent laser beam into a parallel light beam and irradiates the optical head 16 with the light beam. The beam diameter of the laser beam converted into a parallel beam by the imaging lens 14 is the same as the beam diameter of the laser beam converted into a parallel beam by the collimating lens 4 described above.

The optical head 16 includes a reflection mirror (prism) 18 and an objective lens 20, and the parallel light applied to the optical head 16 is reflected by the reflection mirror (prism) 1
After being reflected from 8, it is condensed on a recording surface (not shown) of a recording medium (for example, an optical disk, a magneto-optical disk, etc.) 22 by the objective lens 20. At this time, the parallel movement or swing movement of the optical head 16 is performed along the recording medium 22 to perform coarse tracking control on the recording surface of the recording medium 22.
By finely rotating 0, fine tracking control for the recording surface of the recording medium 22 is performed. Then, the recording medium 22 is controlled while performing such tracking control.
Is optically recorded or reproduced.

In this case, the return light reflected from the recording medium 22 is again guided from the optical head 16 to the deflecting optical element 10 via the imaging lens 14 and the collimating lens 12, and then is returned to the beam shaping prisms 6, 8. The light is reflected from the reflection surface 24 and is applied to the light detection unit 26. The light detection unit 26 detects a tracking error signal, an information reproduction signal, and the like based on the optical characteristics of the return light from the recording medium 22.

[0005]

The recording medium 2
2 (specifically, the access speed of the coarse tracking control on the recording surface of the recording medium 22)
In order to increase the power, it is necessary to reduce the weight of the optical head 16 and its inertia.

As a method of reducing the weight of the optical head 16, for example, a method of reducing the size of each component (the reflecting mirror (prism) 18, the objective lens 20) of the optical head 16 can be considered.

However, in the above-described conventional optical pickup, the beam diameter of the laser beam parallelized by the imaging lens 14 is the same as the beam diameter of the laser beam parallelized by the collimating lens 4. Each component (reflection mirror (prism) 18, objective lens 20) of the optical head 16 cannot be reduced to a size equal to or smaller than the diameter of the laser beam converted into a parallel light beam by the imaging lens 14. Therefore, there is a certain limit in reducing the weight of the optical head 16.

A method of reducing the diameter of the beam emitted from the semiconductor laser 2 is conceivable, but it is difficult in terms of the spread angle of the laser beam. Furthermore, for example, a method of forcibly reducing the light beam diameter with a diaphragm or the like is also conceivable, but in this method, since the laser output is reduced,
It becomes difficult to accurately perform optical recording or optical reproduction of information on the recording medium 22. Also, if the beam diameter of all the laser beams guided in the optical pickup is reduced, high surface accuracy is required for all optical components constituting the optical pickup. Significant optical effects appear.

The present invention has been made to solve such a problem, and an object of the present invention is to reduce the size of an optical head with a simple configuration and improve the access speed to a recording medium. It is to provide a simple optical pickup.

[0010]

To achieve the above object, an optical pickup according to the present invention comprises a laser light source, a collimating lens for converting a laser beam emitted from the laser light source into a parallel light beam, and a collimating lens. A relay lens for converging the laser beam collimated by the lens, an imaging lens for collimating the laser beam converged by the relay lens, and a laser beam collimated by the imaging lens to a recording medium. An optical head for emitting light, and a deflecting optical element for deflecting the laser light condensed on the recording medium by the optical head, wherein the beam diameter of the laser light collimated by the imaging lens is Laser beam collimated by lens is smaller than beam diameter It is.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical pickup according to a first embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same reference numerals are given to the same components as those of the above-described conventional optical pickup, and
The description is omitted.

As shown in FIG. 1, in the optical pickup of the present embodiment, a laser beam emitted from a laser light source (for example, a semiconductor laser) 2 is converted into a parallel light beam by a collimating lens 4 and then a beam shaping prism. It is shaped into a substantially perfect circle by 6,8. The laser light shaped into a substantially perfect circle is reflected from a deflecting optical element (for example, a galvano mirror) 10 that can rotate in the direction of the arrow in the drawing, and then converged by a relay lens 12 to form a focal point F.
Are diverged again and irradiate the imaging lens 14. The imaging lens 14 converts the divergent laser light into a parallel light beam and irradiates the optical head 16 with the light.

The optical head 16 includes a reflecting mirror (prism) 18 and an objective lens 20. The parallel light applied to the optical head 16 is reflected by the reflecting mirror (prism) 1
After being reflected from 8, it is condensed on a recording surface (not shown) of a recording medium (for example, an optical disk, a magneto-optical disk, etc.) 22 by the objective lens 20. At this time, coarse movement tracking control is performed on the recording surface of the recording medium 22 by linearly translating the optical head 16 along the recording medium 22 in the direction of the arrow in the figure. By slightly turning in the direction of the middle arrow,
Fine movement tracking control for the recording surface of the recording medium 22 is performed. Then, optical recording or optical reproduction of information on the recording medium 22 is performed while performing such coarse movement and fine movement tracking control.

In this case, the return light reflected from the recording medium 22 is again guided from the optical head 16 to the deflecting optical element 10 via the imaging lens 14 and the collimating lens 12, and then is returned to the beam shaping prisms 6, 8. The light is reflected from the reflection surface 24 and is applied to the light detection unit 26.

The light detection unit 26 detects a tracking error signal, an information reproduction signal, and the like based on the optical characteristics of the return light from the recording medium 22. In the optical pickup of the present embodiment, the beam diameter of the laser beam converted into a parallel beam by the imaging lens 14 is smaller than the beam diameter of the laser beam converted into a parallel beam by the collimator lens 4 described above.

As a method of reducing the beam diameter of the laser beam converted into a parallel beam by the imaging lens 14, in the present embodiment, the position where the imaging lens 14 is disposed is adjusted. Specifically, the imaging lens 14 is arranged close to the focal point F by a predetermined amount. In this case, assuming that the beam diameter of the laser beam parallelized by the collimator lens 4 is, for example, 1.7 mm, the beam diameter of the laser beam parallelized by the imaging lens 14 is 20% of this beam diameter. The position of the imaging lens 14 is adjusted so as to be in the range of not less than 80% and preferably in the range of not less than 20% and not more than 60%. Because at 80% or more,
This is because the optical head 16 cannot be sufficiently reduced in size, so that reduction of its inertia force cannot be expected.

As described above, according to the present embodiment, the diameter of the laser beam converted into a parallel light beam by the imaging lens 14 is made smaller than the diameter of the laser beam converted into a parallel light beam by the collimating lens 4. ,
Each component (reflection mirror (prism) 1) of optical head 16
8. The size of the objective lens 20) can be reduced. As a result, the weight of the optical head 16 can be reduced, and its inertia can be reduced.
The access speed of the optical head 16 to the optical disk 2 can be improved.

The present invention is not limited to the above-described embodiment, but can be variously modified as follows. For example, a hemispherical lens (not shown) (for example, S
An IL (solid immersion lens) and a magnetic coil are added to the optical head 16, and the condensed light from the objective lens 20 is further narrowed down by a hemispherical lens, so that the spot diameter of the laser light focused on the recording surface of the recording medium 22 May be further reduced, and the optical head 16 may be slightly lifted from the recording surface of the recording medium 22 by the aerodynamic lift acting between the rotated recording medium 22 and the optical head 16. By combining such techniques, the spot diameter of the laser beam can be further reduced without performing focus control, and the recording density on the recording surface of the recording medium 22 can be improved.

The arrangement of the light detection unit 26 is as follows.
The present invention is not limited to the above-described embodiment, and various arrangements are possible according to the purpose of use. Further, the beam shaping prisms 6, 8 are not always necessary.

Next, an optical pickup according to a second embodiment of the present invention will be described with reference to FIG. FIG.
As shown in (1), in the optical pickup according to the present embodiment, the relay lens 12 is disposed in the optical path between the beam shaping prisms 6, 8 and the deflecting optical element (for example, galvanometer mirror) 10.

Except for this point, the other configuration is the same as the configuration of the first embodiment, and the description thereof is omitted.
In such a configuration, a laser beam emitted from a laser light source (for example, a semiconductor laser) 2 is converted into a parallel light beam by a collimating lens 4 and then shaped into a substantially perfect circular shape by beam shaping prisms 6 and 8. The laser light shaped into a substantially perfect circle is converged by a relay lens 12 onto a deflecting optical element (for example, a galvanometer mirror) 10 that can rotate in the direction of the arrow in the figure. The laser beam reflected from the deflecting optical element 10 diverges again after forming the focal point F and is irradiated on the imaging lens 14. The imaging lens 14 converts the divergent laser light into a parallel light beam and irradiates the optical head 16 with the light.

The other operations are the same as those of the first embodiment, and the description is omitted. In the optical pickup of the present embodiment, the imaging lens 14
The beam diameter of the laser beam converted into a parallel beam by the laser beam is smaller than the beam diameter of the laser beam incident on the relay lens 12 (that is, the beam diameter of the laser beam converted into the parallel beam by the collimating lens 4).

The method for reducing the beam diameter of the laser beam converted into a parallel beam by the imaging lens 14 is the same as in the first embodiment described above, and a description thereof will be omitted.

According to the present embodiment, similarly to the first embodiment, it is possible to reduce the size of each component of the optical head 16 (the reflecting mirror (prism) 18 and the objective lens 20). As a result, the weight of the optical head 16 can be reduced, and its inertia can be reduced.
The access speed of the optical head 16 to the optical disk 2 can be improved.

The present invention is not limited to the above-described embodiment, but can be variously modified as follows. Similarly to the first embodiment, if a hemispherical lens (for example, SIL (solid immersion lens)) and a magnetic coil (not shown) are added to the optical head 16, the recording density on the recording surface of the recording medium 22 is dramatically increased. Can be improved. The arrangement of the light detection unit 26 is not limited to the above-described embodiment, and various arrangements can be made according to the purpose of use. Further, the beam shaping prisms 6, 8 are not always necessary.

Next, an optical pickup according to a third embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 3A, in the optical pickup of the present embodiment, all the optical components
The optical head 16 is mounted on a swing arm 28 extending from the swing arm 28. Such a swing arm 28 is configured so as to be able to swing the swing arm portion 30 in the direction of the arrow in FIG.

In this embodiment, the optical head 16 is configured for near-field recording as shown in FIG. 3B, and includes a reflecting mirror (prism) 18
The objective lens 20 includes a hemispherical lens (for example, an SIL (solid immersion lens)) 34 and a magnetic coil 36. The objective lens 20, the hemispherical lens 34, and the magnetic coil 36 are housed in a single housing 38. The housing 38 is connected to a swing arm via an elastic support member (for example, a thin plate spring) 40. It is elastically supported at the tip of the part 30.

In the optical pickup according to the present embodiment, the laser light emitted from the laser light source (for example, a semiconductor laser) 2 is converted into a parallel light beam by the collimating lens 4 and then by the beam shaping prisms 6 and 8. It is shaped into an almost perfect circle. The laser light shaped into a substantially perfect circle is converged by a relay lens 12 onto a deflecting optical element (for example, a galvanometer mirror) 10 that can rotate in the direction of the arrow in the figure. The laser beam reflected from the deflecting optical element 10 diverges again after forming the focal point F and is irradiated on the imaging lens 14. The imaging lens 14 converts the divergent laser beam into a parallel light beam and irradiates the optical head 16 at the tip of the swing arm unit 30.

The parallel light applied to the optical head 16 is reflected by a reflecting mirror (prism) 18 and is reflected by an objective lens 20.
After that, the light is further narrowed down by a hemispherical lens 34 and focused on a recording surface (not shown) of a recording medium (for example, an optical disk or a magneto-optical disk) 22.

At this time, by rotating the swing arm 28 about the rotation shaft 32 and swinging the optical head 16 at the tip of the swing arm section 30 in the direction of the arrow in FIG. Is performed, and fine movement tracking control is performed on the recording surface of the recording medium 22 by slightly rotating the deflecting optical element 10 in the direction of the arrow in the figure. Then, optical recording or optical reproduction of information on the recording medium 22 is performed while performing such coarse movement and fine movement tracking control. In this case, the optical head 16 slightly floats from the recording surface of the recording medium 22 due to the aerodynamic lift acting between the rotating recording medium 22 and the optical head 16 (housing 38). And the spot diameter of the laser beam can be further reduced.
Recording density on the recording surface can be improved.

In this state, the return light reflected from the recording medium 22 is again guided from the optical head 16 to the collimating lens 12 via the imaging lens 14 and the deflecting optical element 10, and then the beam shaping prisms 6, 8 Is irradiated. The return light applied to the beam shaping prisms 6 and 8 is reflected from the reflection surface 24a, and then reflected by the light splitting surface 24b.
Is divided into two directions.

The return light reflected from the light dividing surface 24b is condensed on the light detecting unit 26 by the condensing lens 42. Then, the light detection unit 26 detects a tracking error signal, an information reproduction signal, and the like based on the optical characteristics of the return light from the recording medium 22. The return light transmitted through the light splitting surface 24b is directly applied to the first optical sensor 44. The first optical sensor 44 detects, for example, the angle of the deflecting optical element (for example, galvanomirror) 10.

On the other hand, of the laser light emitted from the laser light source 2, the reflection surfaces 24 of the beam shaping prisms 6, 8
The light reflected from the second optical sensor 46
Is irradiated. In the second optical sensor 46, for example, the output of the laser light source 2 is detected.

In the optical pickup of this embodiment,
The beam diameter of the laser beam that has been converted into a parallel beam by the imaging lens 14 is smaller than the beam diameter of the laser beam that enters the relay lens 12 (that is, the beam diameter of the laser beam that has been converted into a parallel beam by the collimating lens 4). I have.

The method for reducing the beam diameter of the laser beam converted into a parallel beam by the imaging lens 14 is the same as in the first embodiment described above, and a description thereof will be omitted.

According to the present embodiment, similarly to the first embodiment, the beam diameter of the laser beam parallelized by the imaging lens 14 is changed to the beam diameter of the laser beam incident on the relay lens 12 (ie, the beam diameter of the laser beam incident on the relay lens 12). The size of each component (reflection mirror (prism) 18, objective lens 20) of the optical head 16 can be reduced by making it smaller than the light beam diameter of the laser beam converted into a parallel light beam by the collimating lens 4. At the same time, swing arm 2
It is also possible to reduce the size of the swing arm portion 8 of FIG. As a result, the weight of the optical head 16 and the weight of the swing arm 28 (specifically, the weight of the swing arm 30) can be reduced, and the overall inertial force can be reduced. The access speed of the head 16 can be improved.

In the above-described embodiment, the optical head 16 for near-field recording is applied. However, the same applies when the conventional optical head 16 including the reflection mirror (prism) 18 and the objective lens 20 is applied. It is possible to achieve the function and effect of the present invention. The arrangement of the light detection unit 26 and the first and second optical sensors 44 and 46 is not limited to the above-described embodiment, and various arrangements can be made according to the purpose of use. Further, the beam shaping prisms 6, 8 are not always necessary.

Next, an optical pickup according to a fourth embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 4, the optical pickup of the present embodiment is particularly concerned with a partial improvement of the second embodiment, and includes a plurality of lenses (the first and second lenses in the present embodiment). The imaging lens group including the lenses 48 and 50)
It is arranged in the optical path between the deflecting optical element (for example, galvanometer mirror) 10 and the optical head 16. In this case, as an example, a biconvex lens is applied as the first lens 48 and a biconcave lens is applied as the second lens 50.

Except for this point, the other configuration is the same as the configuration of the second embodiment, and the description is omitted.
In such a configuration, a laser beam emitted from a laser light source (for example, a semiconductor laser) 2 is converted into a parallel light beam by a collimating lens 4 and then shaped into a substantially perfect circular shape by beam shaping prisms 6 and 8. The laser light shaped into a substantially perfect circle is converged by the relay lens 12 and forms a focal point F, then diverges again, and is directed to a deflecting optical element (for example, a galvano mirror) 10 rotatable in the direction of the arrow in FIG. Irradiated.

The divergent laser light reflected from the deflecting optical element 10 is converted into a parallel light beam by the imaging lens group and is irradiated on the optical head 16. Specifically, the divergent laser light reflected from the deflecting optical element 10 is converged by the first lens 48 and then converted by the second lens 50 into a parallel light beam having a predetermined light beam diameter.

The other operations are the same as those of the first embodiment, and the description is omitted. In the optical pickup according to the present embodiment, the light beam diameter of the laser light converted into a parallel light beam by the imaging lens group (that is, the light beam diameter of the laser light emitted from the second lens 50).
Is smaller than the light beam diameter of the laser light incident on the relay lens 12 (that is, the light beam diameter of the laser light converted into a parallel light beam by the collimating lens 4).

As a method for reducing the beam diameter of the laser beam converted into a parallel beam by the imaging lens group,
In the present embodiment, the positions where the first and second lenses 48 and 50 constituting the imaging lens group are arranged are adjusted. For example, after positioning the first lens 48, the arrangement of the second lens 50 is adjusted. In this case, assuming that the beam diameter of the laser beam collimated by the collimating lens 4 is, for example, 1.7 mm, the beam diameter of the laser beam emitted from the second lens 50 is 20% of this beam diameter. Not less than 80%, preferably not less than 20% and not more than 60%.
The position of the second lens 50 is adjusted.

According to the present embodiment, similarly to the first embodiment, it is possible to reduce the size of each component of the optical head 16 (the reflecting mirror (prism) 18 and the objective lens 20). As a result, the weight of the optical head 16 can be reduced, and its inertia can be reduced.
The access speed of the optical head 16 to the optical disk 2 can be improved.

The present invention is not limited to the above-described embodiment, but can be variously modified as follows. Similarly to the first embodiment, if a hemispherical lens (for example, SIL (solid immersion lens)) and a magnetic coil (not shown) are added to the optical head 16, the recording density on the recording surface of the recording medium 22 is dramatically increased. Can be improved. The arrangement of the light detection unit 26 is not limited to the above-described embodiment, and various arrangements can be made according to the purpose of use. Further, the beam shaping prisms 6, 8 are not always necessary.

[0047]

According to the present invention, the size of the optical head is reduced by reducing the beam diameter of the laser beam parallelized by the imaging lens to be smaller than the beam diameter of the laser beam parallelized by the collimating lens. Can be reduced, and as a result, it is possible to provide an optical pickup capable of improving the access speed to the recording medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an optical pickup according to a second embodiment of the present invention.

3A is a diagram illustrating a configuration of an optical pickup according to a third embodiment of the present invention, and FIG. 3B is a diagram illustrating a configuration of an optical head used in the third embodiment; .

FIG. 4 is a diagram showing a configuration of an optical pickup according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional optical pickup.

[Explanation of symbols]

 2 Laser Light Source 4 Collimating Lens 10 Deflection Optical Element 12 Relay Lens 14 Imaging Lens 16 Optical Head 22 Recording Medium

Claims (3)

[Claims] 1. A laser light source; a collimator lens for converting a laser beam emitted from the laser light source into a parallel light beam; a relay lens for converging the laser light beam converted into a parallel light beam by the collimator lens; An imaging lens that converts the laser light collimated into a parallel light beam, an optical head that condenses the laser light collimated by the imaging lens onto a recording medium, and a laser light that condenses the recording medium with the optical head. A deflecting optical element for deflecting the laser beam, wherein the beam diameter of the laser beam parallelized by the imaging lens is smaller than the beam diameter of the laser beam parallelized by the collimating lens. Optical pickup. 2. The optical pickup according to claim 1, wherein the optical head moves in parallel along a recording medium. 3. A swing arm rotatable about a rotation axis, wherein the optical head is provided at a tip end of a swing arm portion extending from the swing arm. 2. The optical pickup according to 1.