JPH09204683A - Optical pickup and optical disc drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record or reproduce a signal while removing aberration due to difference in the thickness of disc through a simple mechanism having no mechanical switching mechanism for two kinds or more of optical discs having difference thickness of substrate. SOLUTION: A laser luminous flux 2 emitted from a first light emitting element 1 is passed through a collimate lens 7 to produce a collimate luminous flux which is passed through a luminous flux multiplexing/demultiplexing element 9 and focused through an objective lens 19 onto a thin high density disc 20 formed on a disc substrate. A laser luminous flux 12 emitted from a second light emitting element 11 is passed through the luminous flux multiplexing/ demultiplexing element 9 and enters, as a diverging luminous flux, into the objective lens 19 before being focused on a conventional thick disc formed on a disc substrate 20a thus correcting spherical aberration due to difference in the thickness of disc. A signal processing circuit is switched based on the decision results of a disc type decision means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording or reproducing information signals by using two kinds of optical disks having different substrate thicknesses.

[0002]

2. Description of the Related Art An optical disk device is an information signal recording / reproducing device characterized by a large capacity and high speed access, and taking advantage of the characteristics, it has been widely used as a reproducing device for digital audio signals and an external storage device for a computer. ing. In recent years, with the increase in the capacity of computer data and the practical use of recording / reproducing of digital moving image information, it is required to increase the recording capacity of the optical disk device.

The size of the light spot focused on the recording surface of the optical disk is determined by the wavelength of the laser light source and the numerical aperture (hereinafter NA) of the objective lens. The recording capacity can be increased by increasing the NA and decreasing the diameter of the light spot. However, NA
When is increased, the coma aberration generated due to the tilt of the disk is increased, and the margin for the tilt of the disk and the error of the disk thickness is lost.

In order to solve this problem, the conventional thickness 1.
It has been considered to use a thin disk substrate of 0.6 mm or the like instead of the 2 mm disk substrate.

The problem here is the compatibility of the conventional disk having the substrate thickness with the thin disk. That is,
In the optical disk device, the recording surface is irradiated with the laser light flux through the disk substrate, so the objective lens is designed according to the disk thickness. Since a large spherical aberration occurs in a disc having a thickness different from the designed value, it becomes impossible to record or reproduce a signal at all.

On the other hand, Japanese Patent Laid-Open No. 7-18 shown in FIG.
In the conventional technique described in Japanese Patent No. 2690, a conversion lens 52 is removably provided in an optical path connecting a semiconductor laser 1 which is a light source and an objective lens 19. Then, the thickness of the disc substrate is detected, and the conversion lens 52 is inserted / removed based on the detection signal to suppress the aberration due to the difference in the disc thickness and obtain a good recording or reproducing signal.

[0007]

However, the above structure has a problem that a mechanism for inserting and removing the conversion lens 52 is required. Further, since the positional accuracy and the inclination when the conversion lens 52 is inserted directly affect the optical performance, a mechanism for inserting / removing the lens is required to have high accuracy, and the device becomes large and expensive. Had.

Further, in order to increase the recording density of the high density disc, it is premised that the high density disc is reproduced by using a laser beam having a shorter wavelength than that of the conventional type optical disc. For example, the wavelength of 780 nm in the conventional method is 650 n for a high density disc.
A laser with a wavelength of m or 635 nm is used. In the above-mentioned configuration of the prior art, a short wavelength laser for a high density disc is used as the semiconductor laser 1, and the wavelength for the high density disc is also used when recording or reproducing a conventional disc. Here, of the conventional type optical disks, there is a problem in recording / reproducing of a disk whose characteristics such as reflectance have wavelength dependence.

For example, a so-called write-once type optical disk, which uses a recording film of an organic dye and can be recorded only once and can be reproduced by a reproduction-only device after recording, has already been put into practical use. The reflectance of the recording film of the method changes greatly depending on the wavelength. Therefore, wavelength 780n
A disc for m cannot be reproduced using a wavelength of 650 nm or 635 nm. In the above-mentioned configuration of the prior art, since the conventional type optical disc must be reproduced by using the light source of the wavelength for the high density disc, it is necessary to reproduce the disc having such wavelength dependence among the conventional type optical discs. There is a problem that you cannot do it.

In view of the above problems, the present invention eliminates the occurrence of aberrations due to the difference in the thickness of the disc substrate without using a pull-out mechanism such as a conversion lens, and records two or more types of discs having different thicknesses. An object of the present invention is to provide a reproducible optical disk device and an optical pickup used therein.

[0011]

In order to solve the above problems, according to the present invention, two light emitting elements having different wavelengths or polarization directions, an objective lens, and two light emitting elements emitted from the two light emitting elements are used. A light flux combining / separating element for guiding the light flux to each objective lens by utilizing the difference in wavelength or polarization direction is provided. Then, the two light fluxes emitted from the two light emitting elements are respectively divergent light fluxes or convergent light fluxes having different divergence angles or convergence angles,
The optical system was arranged so as to enter the objective lens. Here, the divergent light beam or the convergent light beam includes a parallel light beam as a special case.

Preferably, the optical system is arranged so that one of the two light beams enters the objective lens as a parallel light beam and the other one light beam enters the objective lens as a divergent light beam. Alternatively, the optical system may be configured such that the two light beams emitted from the two light emitting elements have different divergence angles when they enter the objective lens as divergent light beams.

In addition, 2 emitted from the above two light emitting elements
An intermediate lens for setting a divergence angle or a convergence angle when the light flux enters the objective lens to a predetermined angle is provided in at least one optical path of the light flux of the book.

Further, a limiting aperture for limiting the diameter of the light beam is provided in the optical path of at least one of the two light beams emitted from the two light emitting elements. Alternatively, a limiting aperture that operates as a limiting aperture for only one light flux is integrated with the objective lens by utilizing the difference in wavelength or polarization direction of the two light fluxes emitted from the two light emitting elements. Set up in.

Further, a disc type discriminating means is provided, and the outputs of the two light emitting elements are controlled based on the outputs thereof. Further, based on the output of the disc type discriminating means, a predetermined signal is supplied to the actuator of the objective lens to perform focus and tracking control.

In the optical pickup and the optical disk device configured as described above, the two light beams emitted from the two light emitting elements are guided to the objective lens through the respective light beam combining / separating elements. The two light fluxes are condensed as light spots on the recording surface of the disk by the objective lens.

The objective lens is optimally designed for the disc thickness of one of the two types of discs. For example, when a light beam emitted from the first light emitting element is converted into a parallel light beam by using a collimator lens and then made incident on an objective lens through a light beam combining / separating element, a thickness of 0.6
A light spot with almost no aberration is focused on the recording surface of the disc through the disc substrate of mm.

When an optical spot is focused through a disc substrate having a thickness of 1.2 mm using such an objective lens, a large spherical aberration occurs due to the difference in disc thickness, so that a light spot of sufficient quality can be obtained. Cannot be recorded or played normally.

On the other hand, when the light beam from the second light emitting element is incident as a divergent light beam having a predetermined divergence angle, a spherical aberration occurs which cancels out the spherical aberration caused by the difference in the disc thickness. , Resulting in a thickness of 1.2
A good light spot can be focused through the mm disk substrate.

Further, by providing a limiting opening for limiting the diameter of the light flux from the second light emitting element, the thickness of the second light emitting element has a thickness of 1.2.
The NA at the time of focusing the light spot on the disc of mm can be set to a predetermined value. Further, by providing a limiting aperture that operates as a limiting aperture for only one light flux with the objective lens integrally, the NA at the time of focusing the light spot is set to a predetermined value and the objective lens is moved. It is possible to eliminate the eclipse of the light flux due to.

Further, the disc type discriminating means discriminates the type of the disc mounted in the apparatus, and a predetermined signal processing is executed in accordance with the discrimination result.

Further, since the structure of the present invention has two light emitting elements, it is possible to use elements having wavelengths suitable for the high density disc and the conventional disc as the first light emitting element and the second light emitting element, respectively. it can. For example, a semiconductor laser having a wavelength of 650 nm or 635 nm is used as the first light emitting element, and a wavelength of 780 nm is used as the second light emitting element.
By using a semiconductor laser in the nm band, it is possible to record or reproduce on or from an optical disk such as a write-once type which uses an organic dye and has remarkable wavelength dependence, by using a light source having an appropriate wavelength.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of an optical pickup according to the first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram of the optical pickup of the present invention. In FIG. 1, the light emitting element 1 and the light emitting element 11 which are the light sources of the optical pickup are, for example, semiconductor laser elements. In the present embodiment, light emitting element 1 and light emitting element 11 are elements having different wavelengths. Hereinafter, the wavelengths of the output lights of the light emitting element 1 and the light emitting element 11 are respectively set to λ
1 and λ2. The light emitting element 1 is for recording or reproducing on a high-density disc 20 having a thin disc substrate thickness among the two types of discs, and the light emitting element 11 is for recording or reproducing on a conventional disc (not shown) having a thick disc substrate thickness. To use. Desirably, λ1 is suitable for high density discs, eg 650.
It is preferable to use a short wavelength such as nm or 635 nm, and to use a wavelength such as 780 nm used in the conventional method for λ2. The actual emission wavelength of the laser element varies depending on the product, and the wavelength value here is a nominal value.

The objective lens 19 is designed to focus a light spot having a predetermined aberration amount or less through the substrate 20a of the high density disc 20 when a parallel light beam is incident.

The luminous flux 2 emitted from the light emitting element 1 which is the first light source passes through the first luminous flux separation element 3 and is converted into a parallel luminous flux by the collimator lens 7.

The light beam separating element 3 allows the light beam 2 to pass therethrough and guides it to the subsequent optical system, and separates the reflected light beam 4 from the high density disc 20 from the optical path connecting the light emitting element 1 and the high density disc 20. It is an optical element for guiding to the photodetector 5. For example, by using a diffraction grating or a hologram as the light beam separation element 3, the light beam 2 is guided to the collimator lens 7 as 0th-order diffracted light, that is, direct transmitted light, and the reflected light from the high-density disc 20 is used as 1st-order diffracted light. Lead to 5.

The light beam separating element 3 can be constructed by using an optical element such as a prism, a half mirror, or a waveguide, in addition to a diffraction grating or a hologram. Also,
A diffraction grating for performing tracking error detection by the three-spot method may be installed between the light emitting element 1 and the light beam separating element 3. Further, the collimating lens 7 can be arranged between the light emitting element 1 and the light beam separating element 3. Furthermore, the light emitting element 1, the light beam splitting element 3, and the photodetector 5 may be integrally mounted as the first optical block 6. The optical pickup can be miniaturized by integrally mounting these.

The light beam 8 emitted from the collimator lens 7 is
After passing through the beam combining / separating element 9, it is incident on the objective lens 19 as a parallel beam 17, and is condensed as a light spot on the recording surface 20b through the substrate 20a of the high density disc 20.

The reflected light from the recording surface 20b passes through the objective lens 19, the light beam combining / separating element 9, the collimating lens 7, and the light beam separating element 3 and enters the photodetector 5 as a light beam 4.

On the other hand, the laser light flux 12 emitted from the light emitting element 11 which is the second light source passes through the second light flux separating element 13 and enters the light flux combining and separating element 9.

The light flux combining / separating element 9 is a kind of prism, and has a wavelength filter 10 therein. The wavelength filter 10 acts as a transmission film at λ1 and as a reflection film at λ2. Therefore, the light flux that has passed through the light flux separation element 13 and is incident on the light flux synthesis separation element 9 is
The light is reflected by the wavelength filter 10, enters the objective lens 19 as a divergent light beam 18, and is condensed as a light spot 22.

Here, as described above, the objective lens 19
Is designed to collect the parallel light flux 17 through a thin disk substrate of, for example, 0.6 mm. A divergent light beam 18 is made to enter such an objective lens at a predetermined divergence angle and is condensed through a thick disk substrate of, for example, 1.2 mm. With such a configuration, the light spot 2
2 is a good light spot with little aberration, which is focused on the recording surface of a conventional disc having a thick substrate. In addition,
The disc recorded or reproduced by the light spot 22 is not shown for simplicity.

The light beam reflected by the disc of the light spot 22 passes through the objective lens 19, the light beam combining / separating element 9, and the second light beam separating element 13, and is converted into a light beam 14 by the second photodetector 15.
Incident on. The light emitting element 11, the light beam separating element 13, and the photodetector 15 may be integrally mounted as an optical block 16.

The divergence angle of the divergent light beam 18 incident on the objective lens 19 will be described below. Here, the divergence angle is
It is the angle of the ray passing through the outermost side of the divergent light beam 18, that is, the marginal ray with respect to the optical axis.

In the design by the inventor, for example, an aspherical lens having a focal length of 3.4 mm is used as the objective lens 19,
When the substrate thickness of the high density disc is 0.6 mm and the substrate thickness of the conventional disc is 1.2 mm, the objective lens 1
When the NA on the disk side of 9 is set to 0.6, 1.
It was found that the spherical aberration due to the difference in the disc thickness can be effectively corrected by setting it to 87 degrees, or 1.29 degrees when NA is 0.4. Objective lens 19
The optimum divergence angle differs depending on the design of the focal length or the aspherical surface coefficient, but the spherical aberration can be effectively corrected by setting it to 1 degree or more and 3 degrees or less, and preferably 1 degree or more and 2 degrees or less. .

According to the present embodiment, both the high density disc and the conventional disc are provided with a good light spot without using a mechanical switching mechanism such as insertion / removal of a correction lens or switching of two types of objective lenses. You can record or play with. Further, the high density disc and the conventional disc can be recorded or reproduced by using the light source of the optimum wavelength.

Further, since the structure of the present invention has two light emitting elements, it is possible to use elements having wavelengths suitable for the high density disc and the conventional disc as the first light emitting element and the second light emitting element, respectively. it can. So, for example,
As the first light emitting element, a wavelength of 650 nm band or 635
By using a semiconductor laser in the wavelength band of nm and a semiconductor laser in the wavelength of 780 nm as the second light emitting element, it is possible to cope with a high density disc and an optical disc with a remarkable wavelength dependency such as a write-once type using an organic dye. It is also possible to record or reproduce.

Next, the configuration and operation of the optical pickup according to the second embodiment of the present invention will be described with reference to FIG.

In this embodiment, the light emitting element 1 and the light emitting element 11 are installed so that the polarization directions of output light are different from each other. For example, as shown in the drawing, the polarization directions of the output light of the light emitting element 1 and the light emitting element 11 are parallel to the paper surface and perpendicular to the paper surface, respectively. The wavelengths of the light emitting element 1 and the light emitting element 11 may be different from each other or may be the same.

The light flux combining / separating element 9 of the present embodiment is a polarizing prism and has a polarizing film 30 therein. The polarizing film 30 acts as a transmissive film for polarized light parallel to the paper surface and as a reflective film for polarized light perpendicular to the paper surface. Therefore, similarly to the wavelength filter 10 in the first embodiment, the light beams emitted from the light emitting element 1 and the light emitting element 11 can be guided to the objective lens 19, respectively. The other configurations and operations are the same as those in the first embodiment, and the description thereof will be omitted.

Also according to this embodiment, it is possible to record or reproduce on both a high density disc and a conventional disc with a good light spot without using a mechanical switching mechanism.

Next, the configuration and operation of the optical pickup according to the third embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the limiting aperture 23 is inserted in the optical path connecting the light emitting element 11 and the light flux combining / separating element 9. The limiting aperture 23 determines the NA on the disc side of the light flux for the conventional disc recording or reproducing which is emitted from the light emitting element 11 and focused on the disc by the objective lens 19. Other configurations and operations are similar to those of the first embodiment. Further, the polarization prism shown in the second embodiment may be used instead of the light flux combining / separating element 9 having the wavelength filter 10.

In general, when reproducing a high density disc, since the substrate thickness of the disc is thin, a large NA such as 0.6 is used to reduce the diameter of the light spot 21 on the disc to achieve high density. be able to. However, in the conventional disc, since the substrate thickness is large, the NA is set to a value of 0.4 or 0.5,
It is desirable to prevent the deterioration of aberration due to the tilt of the disc. The limiting opening 23 is formed in the light emitting element 1 as in the present embodiment.
By inserting it in the optical path connecting 1 and the light flux combining / separating element 9, it is possible to record or reproduce the high-density disc and the conventional disc using the optimum NAs.

Next, the structures of the light beam combining / separating element 9 and the limiting aperture 23 according to the fourth embodiment of the present invention will be described with reference to FIG.

4 (a), (b), (c) and (d) are configuration diagrams showing the light flux combining / separating element 9. Light flux combining / separating element 9
The restriction opening 23 and the restriction opening 23 can be integrated as shown in FIG. Further, as shown in (b), even if the wavelength filter 10 is provided only in a part of the prism configuring the light beam combining / separating element 9 instead of providing the limiting aperture 23, the same effect as the limiting aperture is obtained. Therefore, there is an advantage that the number of parts can be reduced.

Further, as shown in (c), a flat plate-shaped light beam combining / separating element 9 may be used instead of the prism-shaped light beam combining / separating element, which is advantageous in that it is inexpensive as compared with the prism-shaped element. There is. Further, as shown in (d), the wavelength filter 10 is provided only in a part of the flat-plate light beam combining / separating element 9, and the same effect as the limiting aperture can be obtained.

In the present embodiment, the wavelength filter 10
Instead of, the polarizing film shown in the second embodiment can be used. Further, when the loss of light quantity does not pose a problem, a half mirror film is used instead of the wavelength filter or the polarizing film of the light beam combining / separating element 9 of the first, second, and third embodiments and the present embodiment. You may. Further, the light flux combining / separating element 9 is not limited to the shape described above,
Any one can be used as long as it has a function of guiding the light beams emitted from the first and second light emitting elements to the objective lens.

Next, the structures of the limiting aperture and the objective lens as the fifth and sixth embodiments of the present invention will be described with reference to FIG.

FIG. 5A is a configuration diagram showing an objective lens 19 and a wavelength selectivity limiting aperture 26 according to a fifth embodiment of the present invention, and FIG. 5B is a wavelength selectivity. FIG. 6 is a plan view of the limiting opening 26 seen from the direction of the optical axis. The objective lens 19 and the wavelength selective limiting aperture 26 are connected via a supporting member 25. The wavelength selective limiting aperture 26 is
As shown in (b), it is divided into a wavelength filter 27 provided in the peripheral portion and a central portion 28.

The wavelength filter 27 transmits the light beam having the wavelength λ1 and reflects, absorbs or scatters the light beam having the wavelength λ2 without transmitting the light beam having the wavelength λ1 in the first embodiment of the present invention. The central portion 28 is transparent to both wavelengths. Desirably, the central portion 28 is provided with an antireflection film for the wavelength λ1 and the wavelength λ2. In the present embodiment, the wavelength-selective limiting aperture 26 acts as a limiting aperture only for the light flux of the wavelength λ2.

FIG. 5C is a constitutional view showing an objective lens 19 as a sixth embodiment of the present invention.
(D) is a plan view of the objective lens 19 as seen from the direction of the optical axis. The objective lens 19 is provided with a wavelength filter 27. The wavelength filter 27 transmits the light flux of the wavelength λ1 and reflects, absorbs or scatters the light flux of the wavelength λ2 without transmitting it. The central portion 28 is transparent to both wavelengths. Desirably, the central portion 28 is provided with an antireflection film for the wavelength λ1 and the wavelength λ2. The wavelength filter 27 may be provided on the light source side surface of the objective lens 19,
It may be provided on the disc side. In the present embodiment, the objective lens 19 acts as a limiting aperture only for the light flux of wavelength λ2. In addition, in the fifth and sixth embodiments, a polarization filter may be used instead of the wavelength filter 27, and may be applied to the configuration described in the second embodiment. The fifth and sixth embodiments can be applied to all configurations of the present invention. Although the limiting aperture means is integrated with the objective lens in the fifth and sixth embodiments, the limiting aperture means may be provided in the optical path connecting the light flux combining / separating element, the objective lens and the disc.

According to the fifth and sixth embodiments, similar to the third embodiment of the present invention, it is possible to record or reproduce the high density disc and the conventional disc respectively by using the optimum NA. it can. Further, according to the fifth and sixth embodiments, since the limiting aperture is provided integrally with the objective lens, even if the objective lens moves due to the tracking operation, the reflected light flux from the disc is limited by the limiting aperture. This has the effect of not causing the problem of partial loss.

Next, a seventh embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a configuration diagram for explaining the configuration of the seventh embodiment. In FIG. 6, the optical path of the light flux emitted from the light emitting element 1 is the same as that of the above-described embodiments. In the present embodiment, the intermediate lens 24 is inserted in the optical path connecting the light emitting element 11 and the light flux combining / separating element 9.

The intermediate lens 24 changes the divergence angle of the light beam 12 emitted from the light emitting element 11 and makes it enter the objective lens 19 as a light beam 18. The purpose of this configuration is to provide the light emitting device 11
Light-emitting element 1 of the light beam emitted from the laser and entering the objective lens
By designing the divergence state on the 1st side and the objective lens 19 side to be different, the divergence state on the objective lens 19 side is designed to have the best aberration, and the light emitting element 11 side is designed to obtain the required light utilization efficiency. Is to

That is, the divergence angle on the objective lens 19 side is, for example, 1 degree or more and 3 degrees or less, or 1 degree or more and 2 degrees or less, as described in the first embodiment. At this time, by setting the divergence angle on the light emitting element 11 side to a larger value, the luminous flux emitted from the light emitting element 11 can be effectively used, and the optical path length from the light emitting element 11 to the objective lens 19 can be further increased. It can be shortened and the device can be downsized.

The intermediate lens 24 may be a convex lens, a concave lens, or any other lens as long as it meets the purpose of this embodiment. Further, the intermediate lens 24 can be applied to any configuration of the present invention. Further, by forming the intermediate lens 24 integrally with the beam combining / separating element 9, the beam separating element 13, the optical block 16, or the like, it is possible to downsize the optical pickup and reduce the number of parts.

Next, an eighth embodiment of the present invention will be described with reference to FIG.

FIG. 7 is a block diagram for explaining the configuration of the eighth embodiment of the present invention. In FIG. 7, the luminous fluxes emitted from the light emitting element 1 and the light emitting element 11 enter the objective lens 19 as divergent luminous fluxes. Also in the configuration of the present embodiment, the light spots 21 and 22 formed by the light flux 17 and the light flux 18 can perform recording or reproduction on a high density disc and a conventional disc, respectively.

Next, an embodiment of the optical disk device of the present invention will be described with reference to FIG.

FIG. 8 is a block diagram showing the configuration of the optical disk device of the present invention. In FIG. 8, the optical pickup 30
Can use the optical pickups of the respective embodiments described so far.

The light emitting element 1 and the light emitting element 11 of the optical pickup 30 are turned on and off by the laser drive circuit 31 and the laser drive circuit 36, respectively, and the emission output is controlled. The outputs of the photodetectors 5 and 15 are supplied to signal processing circuits 33 and 38 via current-voltage conversion circuits 32 and 37, respectively, and signals such as a focus error signal, a tracking error signal, and a main signal are generated. These signals are supplied to the system control circuit 34.

In FIG. 8, the disc type discriminating means 35.
Discriminates the type of disc mounted in the optical disc device and outputs the result to the system control circuit 34. As the disc type determining means 35, a method of detecting the substrate thickness of the disc by an optical or mechanical method,
A method of detecting an identification mark previously recorded on the disc or the cartridge of the disc may be considered.
Alternatively, a method of reproducing the signal of the disk on the assumption of the type of the disk and determining that the disk is another type if a normal signal is not obtained may be used.

The system control circuit 34 turns on the light emitting element 1 or the light emitting element 11 based on the discrimination result received from the disc type discriminating means 35, and forms the light spot suitable for recording or reproducing of the mounted disc. Let
At the same time, the signal processing circuit 33 or the signal processing circuit 3
A suitable output of 8 is selected and the focus error signal and the tracking error signal are supplied to the focus actuator drive circuit 39 and the tracking actuator drive circuit 40, respectively. The outputs of the focus actuator drive circuit 39 and the tracking actuator drive circuit 40 are respectively supplied to the focus coil 41 and the tracking coil 42 of the objective lens actuator in the optical pickup 30, and the focus and tracking servo operations are performed to record or reproduce the disc 20. Is executed.

According to the present embodiment, by using the optical pickup of the present invention, a light emitting element, a photodetector, and a signal processing circuit suitable for the type of the optical disc mounted in the optical disc device are selected, and a correction lens or the like is selected. It is possible to record or reproduce at least two kinds of optical disks without performing mechanical switching of the above. By not performing mechanical switching, an optical disc device having a small size, high reliability, and a simple structure can be realized.

[0068]

According to the present invention, for two types of optical discs having different disc substrate thicknesses, the spherical aberration caused by the difference in the substrate thicknesses can be corrected, and good recording or reproduction can be performed. Further, the diameter of the light beam condensed on the disc can be limited according to the thickness of the disc substrate to set the NA to a predetermined value.

Further, by providing a limiting aperture, which operates as a limiting aperture for only one light flux, integrally with the objective lens, the NA of the light spot is set to a predetermined value and the movement of the objective lens causes The eclipse of the luminous flux can be eliminated.

Further, it is possible to discriminate the type of the optical disc mounted in the optical disc device and electrically switch the light source and the signal processing according to the discrimination result.

Further, the above effects can be realized without providing a mechanical switching mechanism such as a correction lens, and a compact and highly reliable optical pickup and optical disk device can be provided.

Further, by using as the two light-emitting elements the elements having the optimum wavelengths for the high-density disc and the conventional disc, respectively, there is no problem even for the disc whose reflectance greatly changes depending on the wavelength such as the organic dye system. It can be recorded or played without.

[Brief description of drawings]

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

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

FIG. 3 is a configuration diagram of an optical pickup according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a configuration of a light flux combining / separating element according to a fourth embodiment of the present invention.

5A and 5B are a configuration diagram and a plan view showing an objective lens and a limiting aperture as fifth and sixth embodiments of the present invention.

FIG. 6 is a configuration diagram illustrating a configuration of a seventh embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating a configuration of an eighth embodiment of the present invention.

FIG. 8 is a configuration diagram showing an embodiment of an optical disk device of the present invention.

FIG. 9 is a configuration diagram showing a configuration of a conventional technique.

[Explanation of symbols]

1 ... Light emitting element, 5 ... Photodetector, 6 ... Optical block, 7 ...
Collimator lens, 9 ... Light flux combining / separating element, 11 ... Light emitting element, 15 ... Photodetector, 16 ... Optical block, 19 ... Objective lens, 23 ... Limiting aperture, 24 ... Intermediate lens, 26 ...
Wavelength selective limiting aperture, 27 ... Wavelength filter, 30 ... Optical pickup, 35 ... Disc type discriminating means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Sugi 1410 Inada, Hitachinaka City, Ibaraki Prefecture Hitachi, Ltd. Video Information Media Division (72) Hidenori Shinohara 1410 Inada, Hitachinaka City, Ibaraki Hitachi Ltd. Video Information Media Division (72) Inventor Toshio Sugiyama 1 Kitano, Mizuki-shi, Iwate Prefecture Kitano Media Electronics Co., Ltd. (72) Inventor Yukio Fukui 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Multimedia System development headquarters

Claims (18)

[Claims] 1. A first light emitting element, a second light emitting element, and an objective lens for condensing light fluxes emitted from the first and second light emitting elements on a signal recording surface of an optical information recording medium. ,
In an optical pickup having a light flux combining / separating element that guides two light fluxes emitted from the first and second light emitting elements to the objective lens, the light flux is emitted from the first light emitting element and enters the objective lens. The divergence angle or the convergence angle of the light flux and the divergence angle or the convergence angle of the light flux emitted from the second light emitting element and incident on the objective lens are set to different predetermined values from each other. Yes, an optical pickup. 2. A first light emitting element, a second light emitting element, and an objective lens for condensing light fluxes emitted from the first and second light emitting elements on a signal recording surface of an optical information recording medium. ,
In an optical pickup having a light flux combining / separating element that guides two light fluxes emitted from the first and second light emitting elements to the objective lens, the light flux emitted from the first light emitting element is a parallel light flux. An optical pickup, wherein a light beam incident on a lens and emitted from the second light emitting element is incident on the objective lens as a divergent light beam having a divergence angle of 1 degree or more and 3 degrees or less. 3. A first light emitting element, a second light emitting element, and an objective lens for condensing the light beams emitted from the first and second light emitting elements on a signal recording surface of an optical information recording medium. ,
In an optical pickup having a light flux combining / separating element that guides two light fluxes emitted from the first and second light emitting elements to the objective lens, the light flux emitted from the first light emitting element is a parallel light flux. An optical pickup, characterized in that a light beam incident on a lens and emitted from the second light emitting element is incident on the objective lens as a divergent light beam having a divergence angle of 1 degree or more and 2 degrees or less. 4. A first light emitting element, a second light emitting element, and an objective lens for condensing light fluxes emitted from the first and second light emitting elements on a signal recording surface of an optical information recording medium. ,
In an optical pickup having a light flux combining / separating element for guiding two light fluxes emitted from the first and second light emitting elements to the objective lens, an optical path connecting the first light emitting element and the light flux combining / separating element. A first optical element for collimating the light beam emitted from the first light emitting element into a parallel light beam, and the second optical element in the optical path connecting the second light emitting element and the light beam combining / separating element. An optical pickup having a second optical element for converting a light beam emitted from a light emitting element into a predetermined divergent light beam. 5. The emission wavelength of the first light emitting element and the second wavelength
Different from the light emitting wavelength of the light emitting element, the light flux combining / separating element transmits or reflects the light flux emitted from the first light emitting element due to the difference in the wavelength of the incident light flux, and
5. The optical pickup according to claim 2, 3 or 4, wherein the light flux emitted from the light emitting element is guided to the objective lens by being reflected or transmitted. 6. The light according to claim 5, wherein an annular wavelength filter that reflects, absorbs, or scatters a luminous flux having an emission wavelength of the second light emitting element is provided integrally with the objective lens. pick up. 7. The light flux emitted from the first light emitting element and the light flux emitted from the second light emitting element have different polarization directions when entering the light flux combining / separating element, and the light flux combining / separating is performed. The element transmits or reflects the luminous flux emitted from the first light emitting element and reflects or transmits the luminous flux emitted from the second light emitting element due to the difference in the polarization direction, and guides the luminous flux to the objective lens, respectively. The optical pickup according to claim 2, claim 3, or claim 4. 8. The optical pickup according to claim 7, wherein an annular polarization filter that reflects, absorbs, or scatters the luminous flux emitted from the second light emitting element is provided integrally with the objective lens. . 9. A limiting aperture for limiting a diameter of a light beam emitted from the second light emitting element to a predetermined value in an optical path connecting the second light emitting element and the light beam combining / separating element. The optical pickup according to claim 2, claim 3, claim 4, claim 5, or claim 7. 10. A first light emitting element, a second light emitting element,
An objective lens for condensing the light flux on the signal recording surface of the optical information recording medium, and a light flux synthesis separation for guiding the first and second light fluxes emitted from the first and second light emitting elements to the objective lens, respectively. An element, a first light receiving element that receives the reflected light of the first light flux from the optical information recording medium, and a second light receiving element that receives the reflected light of the second light flux from the optical information recording medium And a detection output of the first light receiving element and a detection output of the second light receiving element based on a determination result by the medium determination means. An optical disk device, wherein any one of the above is selected and predetermined signal processing is executed. 11. A first light emitting element, a second light emitting element,
Objective lens for condensing the light flux on the signal recording surface of the optical information recording medium, and light flux synthesis separation for guiding the first and second light fluxes emitted from the first and second light emitting elements to the objective lens, respectively. An element, a first light receiving element that receives the reflected light of the first light flux from the optical information recording medium, and a second light receiving element that receives the reflected light of the second light flux from the optical information recording medium A medium discriminating means for discriminating the type of the optical information recording medium, and selecting one of the first light emitting element and the second light emitting element based on a discrimination result by the medium discriminating means. It lights up,
Optical disk device. 12. A second optical element for converting a light beam emitted from the second light emitting element into a predetermined divergent light beam in an optical path connecting the second light emitting element and the light beam combining / separating element. The optical disk device according to claim 10 or 11, characterized in that. 13. A first light emitting element, a second light emitting element,
In an optical pickup having an objective lens for condensing the light fluxes emitted from the first and second light emitting elements on a signal recording surface of an optical information recording medium, the objective lens is emitted from the first light emitting element. The divergence angle or converging angle of the light beam incident on and the divergence angle or the converging angle of the light beam emitted from the second light emitting element and incident on the objective lens are set to predetermined values different from each other. An optical pickup characterized by. 14. A first light emitting element, a second light emitting element,
An objective lens for focusing the light beams emitted from the first and second light emitting elements on the signal recording surface of the optical information recording medium, and two light beams emitted from the first and second light emitting elements, respectively. In an optical pickup having a light flux combining / separating element for guiding to the objective lens, in order to make a light flux emitted from the first light emitting element into a parallel light flux in an optical path connecting the first light emitting element and the light flux combining / separating element. An optical pickup having the optical element of. 15. A wavelength filter that reflects, absorbs, or scatters a luminous flux of the emission wavelength of the second light emitting element is provided in an optical path connecting the luminous flux combining / separating element, the objective lens, and the signal recording surface of the optical information recording medium. The optical pickup according to claim 5, wherein 16. A polarizing filter for reflecting, absorbing or scattering a light beam emitted from the second light emitting element is provided in an optical path connecting a light beam combining / separating element, an objective lens and a signal recording surface of an optical information recording medium. The optical pickup according to claim 7, characterized in that: 17. The light emitting wavelength of the first light emitting element and the light emitting wavelength of the second light emitting element are different from each other, and the light flux combining / separating element has the first light emitting element due to a difference in wavelength of an incident light flux. 12. The light flux emitted from the light-emitting element is transmitted or reflected, and the light flux emitted from the second light-emitting element is reflected or transmitted to be guided to the objective lens, respectively. Optical disk device. 18. The medium discriminating means discriminates at least an optical information recording medium having an optical substrate thickness of 0.6 mm and 1.2 mm, and the emission wavelength of the first light emitting element is 650.
The optical disk device according to claim 10 or 11, wherein the second light emitting element has an emission wavelength of 780 nm.