JPH10312578A - Objective lens for optical pickup device, optical pickup device and optical information recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens used for an optical pickup device by which prescribed information can be recorded and reproduced with reference to different optical information recording mediums and which can be made thin and lightweight. SOLUTION: An optical pickup device 30 contains a first light source 1 which outputs light having a first wavelength, a second light source 8 which outputs light having a second wavelength different from the first wavelength and an objective lens 4. It is constituted of an optical system 10 by which the light to be output from either the first light source 1 or the second light sources 8 is condensed selectively on either an appropriate optical information recording medium 7a or an appropriate optical information recording medium 7b. In this case, the objective lens 4 is used for the optical pickup device 30 which has a wavelength-selection and aperture-limitation function 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens used in an optical pickup device, and to an optical pickup device using the objective lens. More specifically, the present invention adds a wavelength selection aperture limiting function required for an optical pickup having two different wavelength light sources to an objective lens.

[0002]

2. Description of the Related Art Hitherto, an optical pickup for recording predetermined information on an optical information recording medium such as an optical disk or reproducing an optical information signal recorded on the optical information recording medium has been known. On the other hand, diversification of optical information recording media,
In connection with the increase in density, a plurality of types of optical information recording media having different information recording methods and recording surfaces have been used, and as a result, the various types of optical information recording media have been selected by users. The optical pickup device can be used arbitrarily and selectively, so that even if an optical pickup device uses any of optical information recording media such as an optical disk having a different recording method and a recording surface, predetermined information can be recorded. It is required to have a function that enables a reproduction operation.

[0003] Therefore, as an optical pickup device which satisfies the above requirements, for example, a light source for outputting light having a wavelength suitable for the substrate thickness, pit depth, and reflection film of a disk for recording or reproducing is provided. At the same time, it is necessary to write necessary information with the same optical pickup device on the optical information recording media having different standards as described above, for example, two different types of disks, using one optical pickup device. To reproduce the specified information from
There has been proposed a method in which a single optical pickup device has a plurality of light sources that output at least two different wavelengths of light, and performs recording / reproduction in correspondence with a disc of a standard suitable for each wavelength. Such a method is generally called a two-wavelength light source pickup method, and the above method is particularly called a two-wavelength two-lens method. In the two-wavelength light source two-lens method, two kinds of light sources are used. The objective lens for condensing the light on the disk is prepared separately for each light source. Therefore, when there are two types of light sources that output lights having different wavelengths from each other,
Two such objective lenses will also be used.

The two objective lenses can be arbitrarily and selectively exchanged by using an appropriate exchange means. Therefore, in such a method, the light from each light source is suitable for each wavelength by attaching an aperture limiting function optimal for each objective lens, for example, a wavelength aperture plate or the like to the objective lens housing itself. Optimal beam diameter can be tied on a disc.

[0005] However, in such a method, since the means for exchanging the objective lens is required, the structure of the optical pickup itself becomes complicated, and the size of the optical pickup itself becomes large. It has the problem of being difficult. FIG. 8A shows another method.
The two-wavelength one-lens system as shown in FIG. 1 is also known. In such a system, the light-emitting points of two light sources 1 and 8 that output light of different wavelengths are changed to reduce the spherical aberration of the substrate thickness. An optical pickup that uses a single objective lens 4 to condense light beams of two light source wavelengths onto two or more types of disks 7a and 7b by a single objective lens 4 is used. , A light source 1 that outputs the two wavelengths,
8 need to be provided with an optimal aperture limiting function.

That is, in the example shown in FIG. 8A, for the first light source 1 that outputs light having the first wavelength,
A first wavelength aperture limiting plate 6 provided in a housing 5 of the objective lens 4 performs an aperture limiting function, and a second light source 8 that outputs light having a second wavelength is provided. The second wavelength aperture limiting plate 9 provided close to the light source 8 performs the aperture limiting function.

On the other hand, as a method of providing an optimum aperture limit for two types of wavelengths, when an aperture limit of wavelength 1 which requires a large aperture diameter is provided on the same housing as the objective lens, the required aperture diameter is set. The aperture of the wavelength 2 having a small wavelength can be limited by a method of providing an aperture at a portion that does not block the optical path of the wavelength 1 (hereinafter, referred to as a fixed aperture method), or by using the wavelength 1 on the same housing as the lens.
Having a wavelength selection filter function having a region that transmits light and blocks wavelength 2 (hereinafter referred to as a wavelength filter)
(Hereinafter referred to as a wavelength filter method) has been proposed.

The operation of the above-described conventional optical pickup device will be described in detail with reference to FIG. FIG.
In (A), when reproducing the disk 7a corresponding to the first wavelength, the light emitted from the first wavelength light source 1
After passing through the wavelength-selective prism 2, it is converged to parallel light by the collimator lens 3, and the first wavelength aperture limit 6 formed by the objective lens housing 5 holding the objective lens 4.
After the aperture is restricted by the
The light is focused on the disk 7a to be reproduced by the wavelength, and the information on the disk is reproduced.

When reproducing a disc corresponding to the second wavelength, the light emitted from the second wavelength light source 8 is limited in aperture by the second wavelength aperture limit 9 and then reflected by the wavelength selection prism 2. After changing the optical path, the light is condensed by the collimator lens 3 and condensed on the disk 7b corresponding to the second wavelength by the objective lens 4, and the information on the disk is reproduced.

In this system, at the first wavelength, the first aperture limit 6 moves in the horizontal direction (left and right direction) at the same time as the objective lens 4 and the housing 5, so that the objective lens 4 when reproducing the signal on the disk 7a is moved. No performance degradation due to movement is observed. However, at the second wavelength, the second wavelength aperture limit 9 is not synchronized with the horizontal (left-right) movement of the objective lens 4, so that
The movement of the objective lens partially blocks the optical path, and as a result, the reproduction performance during reproduction of the disc is deteriorated.

Next, an example in which a wavelength filter method is used in the optical system in the conventional optical pickup is shown in FIG.
It is shown in (B). 8B, with respect to the first light source 1, light emitted from the first wavelength light source 1 passes through the same optical path as in FIG. 8A, passes through the wavelength-selective prism 2, the collimator lens 3, and then passes through the objective lens. The light enters the wavelength filter 10 provided in the housing 5.

On the wavelength filter 10, there are a two-wavelength transmission region and a wavelength transmission selection region formed by a dielectric multilayer film. However, the first wavelength is transmitted through the wavelength transmission selection region at the first wavelength. The wavelength filter 10 does not restrict the aperture. Thereafter, the light is condensed by the objective lens 4 similarly to the first wavelength in FIG. 8A, and the information on the disk 7a can be reproduced. At this time, similarly to FIG. 8A, no deterioration in the reproduction performance due to the movement of the objective lens 4 is observed.

Regarding the second wavelength, the light emitted from the second wavelength light source 8 is incident on the wavelength selective prism 2 without limiting the aperture, and is reflected by 90 degrees, unlike the case of FIG. 8A. . After being reflected by the collimator lens 3, the reflected light is incident on the wavelength filter 10 fixed on the objective lens housing 5, where the second wavelength is the dielectric material formed on the wavelength filter 10. The aperture is limited by the action of the multilayer film, and the light is condensed by the objective lens 4 and reproduced on the second wavelength compatible disk 7b.

In this method, the second wavelength aperture limit is limited by the wavelength filter 10 and the wavelength filter 10
Is configured so as to move integrally with the objective lens 4, the optical path is not blocked by the movement of the objective lens as in the fixed aperture method of FIG. can not see. However, in such a method, since the objective lens 4 and the wavelength filter 10 are integrated into the predetermined casing 5, the structure of the optical pickup section becomes longer in the axial direction of light, and the weight and the size are reduced. The structure cannot be matched with the direction of.

FIG. 9 shows an example of the configuration of a wavelength filter used in the above-mentioned conventional example. The wavelength filter 1
The configuration 0 is composed of two regions, a two-wavelength transmission region A and a wavelength selection region B, which are manufactured by forming a dielectric multilayer film on a glass plate.

[0016]

As described above, FIG.
In the fixed aperture method which is the first conventional method shown in FIG. 1A, since the second wavelength aperture limit 9 is fixed, it is inevitable that the optical path is blocked by moving the objective lens 4 during reproduction of the optical disk. It is difficult to ensure playback performance. Further FIG.
As shown in (B), in the wavelength filter method, which is the second conventional method, the deterioration of the reproduction performance due to the movement of the objective lens 4, which is a drawback of the fixed aperture method, is small. In addition, since the optical pickup includes the wavelength filter 10, which is an optical component, it is difficult to reduce the thickness and weight of the optical pickup.

An object of the present invention is to improve the above-mentioned drawbacks of the prior art, to enable recording and reproduction of predetermined information on different optical information recording media, and to realize a structure that can be made thinner and lighter. And an optical pickup device using the objective lens.

[0018]

In order to achieve the above-mentioned object, the present invention employs the following basic technical structure. That is, as a first aspect according to the present invention, a first light source that outputs light having a first wavelength,
A second light source that outputs light having a second wavelength different from the first light source and an objective lens, and selectively outputs light output from either the first light source or the second light source to an appropriate light. In an optical pickup device comprising an optical system for condensing light on an information recording medium, the objective lens has a wavelength selection aperture limiting function. A second aspect according to the present invention is a lens, wherein the first light source outputs light having a first wavelength, and the light source outputs light having a second wavelength different from the first wavelength. Including a second light source, and an objective lens, the light output from any of the first or second light source,
An optical system for selectively focusing light on an appropriate optical information recording medium, wherein an objective lens having a wavelength selection aperture limiting function is used as the objective lens. An optical pickup device.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic technical configuration of an objective lens and an optical pickup device using the objective lens according to the present invention is based on a wavelength filter system in order to suppress deterioration of reproduction performance due to movement of the objective lens 4. The objective lens 4 is provided with a function of limiting the aperture for wavelength selection, which has been conventionally performed by a wavelength filter, in order to realize thinning and miniaturization at the same time.

In other words, in the present invention, by disposing the wavelength filter, which has been conventionally arranged separately from the objective lens, directly on the surface of the objective lens, many of the above-mentioned conventional problems are brilliantly achieved. It was something that could be solved.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an objective lens used in an optical pickup device according to the present invention. That is, FIG. 1 is a diagram showing a specific example of the configuration of the objective lens according to the present invention.
A first light source 1 for outputting light having a first wavelength, a second light source 8 for outputting light having a second wavelength different from the first wavelength, and an objective lens 4; Or second
Wavelength selecting prism 2, collimating lens 3, or first wavelength aperture limiting plate for selectively condensing light output from any one of light sources 1 and 8 on appropriate optical information recording media 7a and 7b. In the optical pickup device 30 including the optical system 10 including the optical lens 6 and the like, the objective lens 4 is used for the optical pickup device 30 having the wavelength selection aperture limiting function 15. It is shown.

That is, the objective lens 4 according to the present invention can be used in an optical pickup having two different wavelength light sources.
A single objective lens has a wavelength selection aperture limiting function 15 necessary for recording information on or reproducing information from two or more types of disks having different pit lengths, pit depths, and disk thicknesses. The objective lens is used. As an example of specific means for realizing the wavelength selection aperture limiting function 15, for example, the objective lens 4 is used.
A dielectric multilayer film similar to the above-described wavelength filter 10 having an aperture limiting function is formed on a part of the surface by vapor deposition or other known methods.

The surface on which the dielectric multilayer film is formed may be the surface of the objective lens 4 on the disk 7 side, or may be the opposite surface of the objective lens 4 on the light source 1 side. Is
It may be formed on both surfaces. A method of adding an aperture limiting function to the objective lens 4 is realized by forming a dielectric multilayer film on the objective lens 4 as in the case of the wavelength filter 10. The surface on which the dielectric multilayer film 15 is formed may be one of the surface of the objective lens 4 on the disk 7b side, the surface on the second wavelength light source 8 side, or both surfaces.

In the specific example of the objective lens 4 according to the present invention shown in FIG. 2, the optical information recording medium 7 of the objective lens 4 is used.
The dielectric multilayer film 15 is formed in an annular shape as shown in FIG. 3, which will be described later, along the surface on the opposite side, that is, along the curved surface of the objective lens 4. The wavelength filter 10 used in FIG. 8B, as shown in FIG. 8B, can be omitted.

In the present invention, since the wavelength-selecting aperture limiting function 15 is provided integrally with the objective lens 4, the wavelength-selecting aperture limiting function 15 is also integrated with the objective lens 4. The objective lens 4 does not deteriorate the reproduction performance, and the configuration of the optical head portion including the objective lens 4 is simplified.
It is possible to reduce the size and weight.

As shown in FIG. 9, the dielectric multilayer film 15 which exhibits the function of limiting the wavelength selection aperture in the present invention, for example, emits light having a first wavelength output from the first light source 1. Although it has only to have a function of preventing light having a second wavelength different from the first wavelength output from the second light source 8 from passing therethrough, the inside, that is, the region a and the external b are configured so that both the light having the first wavelength and the light having the second wavelength output from the first and second light sources can be transmitted.

The inner diameter of the annular portion of the dielectric multilayer film 15 in the objective lens 4 according to the present invention is not particularly limited. It is desirable that the power of the optical information recording medium 7 be set to a dimension such that the disk 7b having a recording surface located at a deeper position in the optical information recording medium 7 is focused on the recording surface.

The outer diameter of the annular portion of the dielectric multilayer film 15 in the objective lens 4 is not particularly limited, but the outer diameter is the inner diameter of the first wavelength aperture limiting plate 6 described above. It is desirable to set it so that it matches. FIG. 4 shows another specific example of the objective lens 4 according to the present invention, in which a dielectric multilayer film 15 for realizing the wavelength selective aperture limiting function is provided on the surface of the objective lens 4 on the disk 7 side. FIG. 5 shows an objective lens with a wavelength-selective aperture limit formed by vapor deposition of a conductive multilayer film. FIG. 5 shows still another specific example of the objective lens 4 according to the present invention. An objective lens with a wavelength-selective aperture limit, in which a dielectric multilayer film 15 for realizing the function is formed on the surface of the objective lens 4 on the disk 7 side and on both the light source side by vapor deposition of the dielectric multilayer film.

FIG. 6 shows an optical pickup device 30 using the objective lens 4 having the wavelength selection aperture limiting function 15 shown in FIG.
5 shows an optical pickup device 30 configured using the objective lens 4 having the wavelength selection aperture limiting function 15 shown in FIG. That is, as an optical pickup device according to the present invention, for example, a first light source 1 that outputs light having a first wavelength, and a second light source that outputs light having a second wavelength different from the first wavelength. An optical system 20 for selectively condensing light output from any of the first or second light sources 1 and 8 onto an appropriate optical information recording medium, including the light source 8 and the objective lens 4; The optical pickup device 30 includes an objective lens 4 having a wavelength selection aperture limiting function 15 as the objective lens 4.

Further, in the present invention, by using the above-described optical pickup device, discs having different thicknesses, different pit depths or pit lengths, and different types of discs having a reflective film can be used. It is possible to record / reproduce appropriate optical information. Therefore, as a method for recording / reproducing such optical information, for example, the first light source 1 for outputting light having the first wavelength, the first light source And a second light source 8 for outputting light having a second wavelength different from the wavelength of the second light source, and the objective lens 4. The light output from either the first or second light source is selectively and appropriately The objective lens 4 is provided with a wavelength selection aperture limiting function 15 by using an optical pickup device 30 composed of an optical system 20 for focusing light on an optical information recording medium. The output light and the second By selectively focusing the output light from the light source 8 on the position 7a or 7b different from each other by the wavelength selection aperture limiting function 15, the predetermined information is written on the optical information recording medium 7 and / or the predetermined information is written. This is an optical information recording / reproducing method configured to read out the information.

In such a case, the optical information recording medium 7
Are the same optical pickup device 30 and at least two types of optical information recording media 7 different from each other in at least one of bit length, pit depth, disk thickness and the like.
a or 7b can be selectively used.

[0032]

The first effect is that by eliminating the wavelength filter, it is possible to reduce the thickness of the wavelength filter and to reduce the thickness of the spectral pickup while ensuring the performance of the pickup during lens shift. The second effect is that by removing the wavelength filter from the lens housing, it is possible to reduce the weight of the actuator part of the optical pickup while securing the performance of the lens shift of the pickup, thereby improving the performance of the actuator. (Improve acceleration sensitivity),
The performance of the pickup can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a specific example of an optical pickup device using an objective lens according to the present invention.

FIG. 2 is a diagram showing a main part of an objective lens according to the present invention.

FIG. 3A is a cross-sectional view of a specific example according to the present invention, and FIG. 3B is a bottom view thereof.

FIG. 4A is a cross-sectional view of another specific example according to the present invention, and FIG. 4B is a bottom view thereof.

FIG. 5 (A) is a top view of still another embodiment according to the present invention, FIG. 4 (B) is a cross-sectional view thereof, and FIG. It is a bottom view.

FIG. 6 is a diagram showing another specific example of the optical pickup device using the objective lens according to the present invention.

FIG. 7 is a diagram showing still another specific example of the optical pickup device using the objective lens according to the present invention.

FIG. 8A is a diagram showing an example of a conventional optical pickup device, and FIG. 8B is a diagram showing another example of a conventional optical pickup device.

FIG. 9 is a plan view showing an example of a configuration of a conventional wavelength filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st light source 2 ... Wavelength selection prism 3 ... Collimating lens 4 ... Objective lens 5 ... Objective lens housing 6 ... 1st wavelength aperture limiting plate 7, 7a, 7b ... Optical information recording medium, disk 8 ... 2nd Light source 9 ... second wavelength aperture limiting plate 10 ... wavelength filter 15 ... wavelength selective aperture limiting function, dielectric multilayer film 20 ... optical system 30 ... optical pickup device

Claims (6)

[Claims] A first light source that outputs light having a first wavelength, a second light source that outputs light having a second wavelength different from the first wavelength, and an objective lens. An optical system configured to selectively condense light output from one of the first and second light sources onto an appropriate optical information recording medium. An objective lens used in an optical pickup device having a wavelength selection aperture limiting function. A first light source that outputs light having a first wavelength, a second light source that outputs light having a second wavelength different from the first wavelength, and an objective lens. An optical system for selectively condensing light output from one of the first and second light sources onto an appropriate optical information recording medium. An optical pickup device comprising an objective lens provided with a selective aperture limiting function. 3. The wavelength selective aperture limiting function is provided on a surface of the objective lens facing the optical information recording medium, a surface facing the light source, or both. 2. The objective lens according to 1. 4. The objective lens, wherein the wavelength selective aperture limiting function is provided on a surface of the objective lens facing the optical information recording medium, a surface facing the light source, or both. 3. The optical pickup device according to claim 2, wherein: 5. A light source for outputting light having a first wavelength, a second light source for outputting light having a second wavelength different from the first wavelength, and an objective lens. And an optical system configured to selectively condense light output from one of the first and second light sources onto an appropriate optical information recording medium. A selective aperture limiting function is provided, and the output light from the first light source and the output light from the second light source are selectively focused to different positions by the wavelength selective aperture limiting function. An optical information recording / reproducing method, wherein predetermined information is written to and / or read out from the optical information recording medium. 6. The optical information recording medium according to claim 1, wherein at least one of at least one of a bit length, a pit depth, a disk thickness, and the like is different from each other. 6. The optical information recording / reproducing method according to claim 5, wherein: