JPH11110806A - Optical head and optical storage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head recording/reproducing for optical storage media with different substrate thickness, track pitches and recording density by combining/using plural pieces of laser light sources with different wavelengths, a sheet of objective lens designed optimally to an optical disk with thin substrate thickness and an aperture limit element. SOLUTION: In the case of a high density optical disk, a laser beam 15 emitted from a semiconductor laser 1 of the wavelength 430 nm is reflected by a beam splitter 3, and passes through a wavelength filter 4, and is converted to parallel light by a collimate lens 5 to be converged on a track on the thin disk 21 with the substrate thickness 0.6 mm by an objective lens 7. Reflected light passes through an opposite optical path, and transmits through the beam splitter 3, and is converged on a photodetector 11 to detect a signal. In the case of a DVD, a DVD-RAM, etc., similarly the semiconductor laser 1 is used, and the numerical aperture of the objective lens is limited to 0.4-0.6 by the aperture limit element 17. In the case of a CD, etc., a near infrared laser unit 2 with the wavelength 785 nm incorporating the photodetector in the inside is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head and an optical storage device for recording or reproducing information on an optical storage medium such as an optical disk or an optical card by using a laser beam.

[0002]

2. Description of the Related Art Currently available optical disks, for example, in the case of a compact disk (CD), have a disk substrate thickness of 1.2 mm and a track pitch for recording information of 1.6 μm. On the other hand, in recent years, as a digital video disk (DVD) as a high-density, large-capacity optical storage medium, specifications have been standardized in which the disk substrate thickness is 0.6 mm, the track pitch is 0.74 μm, and the shortest pit length is 0.4 μm. ing. Wavelength 650n for the DVD
m or 635 nm laser wavelength light source and a numerical aperture (N
A) An optical head for reproducing or recording information using a 0.6 objective lens has been developed. The optical head reproduces not only high-density and large-capacity discs such as the DVD but also optical discs such as CDs, CD-Rs (recordable-CDs) and CD-RWs (rewritable-CDs) which are currently commercially available. Alternatively, various optical heads having a recording function have been proposed.

As one of the methods, there is a two objective lens and two laser light source method as shown in FIG. As shown in FIG. 6, an optical system for DVD includes a laser light source 101, a beam splitter 103, a wavelength filter 104, a collimator lens 105, a mirror 106, an objective lens 107, a concave lens 110, and a light receiving element 111. The laser light source 101 is a semiconductor laser having a wavelength of 650 nm. on the other hand,
The optical system for the CD includes a laser light source 102, a three-beam diffraction grating 120, a beam splitter 121, a wavelength filter 104, a collimator lens 105, a mirror 106,
It comprises an objective lens 122, a concave lens 123, and a light receiving element 112. The laser light source 102 is a semiconductor laser having a wavelength of 785 nm.

When a DVD disc is mounted,
The laser light source 101 emits light, the objective lens 107 is arranged on the optical axis as shown in FIG. 6, and recording or reproduction is performed. When a CD disc is mounted, the laser light source 102 emits light, and the objective lens 122 is arranged on the optical axis in place of the objective lens 107 shown in FIG. 6, and reproduction or recording is performed.

[0005]

The above-mentioned optical head is
Although DVDs, CDs, and CD-R / RWs can be recorded or reproduced, they have a problem that they cannot be used for optical discs with higher densities. The higher density optical disk is, for example, a disk having a substrate thickness of 0.6 mm, a track pitch for recording information of about 0.5 μm, and a shortest pit length of about 0.3 μm.

Further, two laser light sources and two light receiving elements are mounted for recording or reproducing DVDs, CDs, and CD-Rs, and a plurality of optical components such as a beam splitter are required. Had the problem of becoming

[0007] Therefore, the present invention has a simple configuration and can be used for an existing CD,
It is an object of the present invention to provide an optical head capable of recording or reproducing a CD-R, a CD-RW, and a DVD, and capable of recording or reproducing a DVD-RAM and a high-density large-capacity disk, and an optical drive device. I have.

[0008]

Means for Solving the Problems The structure of the present invention for solving the above problems is as follows: 1) having a plurality of laser light sources having different wavelengths, and an infinite objective lens optimally designed at the first wavelength; In an optical head for reproducing or recording a signal in a method of switching and using the laser light source according to an optical storage medium, the first wavelength is about 430 nm, and the second wavelength is about 785 nm. A near-infrared laser light source, the first wavelength laser light incident on the objective lens is incident parallel to the optical axis, the second wavelength laser light is incident on the divergent light, the divergence angle of the divergent light Is characterized in that, when an angle between a light ray passing through the effective diameter of the objective lens and the optical axis is θ (degree), 1.58 ≦ θ ≦ 1.66.

2) a plurality of laser light sources having different wavelengths;
An optical head having an objective lens optimally designed at a first wavelength, and reproducing or recording a signal in a method of switching and using the laser light source according to an optical storage medium; A blue-violet laser light source of about 430 nm, a near-infrared laser light source having the second wavelength of about 785 nm, and the aperture of the laser light of the first wavelength incident on the objective lens can be variably limited to two values. A variable aperture limiting means, and an aperture limiting means for limiting an aperture of the laser light of the second wavelength incident on the objective lens.

3) In the optical head described in 2), when a laser beam of the first wavelength is emitted, the numerical aperture of the objective lens can be switched between about 0.6 and about 0.4. A variable aperture limiting means is provided, wherein the aperture limiting means for setting the numerical aperture of the objective lens to 0.45 when the laser light of the second wavelength is emitted.

4) In the optical head described in 1) or 2), the optical system using a laser light source having a wavelength of about 785 nm comprises a light receiving element for receiving an information signal and a servo error signal from an optical storage medium, and The laser light sources are both units mounted in the same package, and the optical system using a laser light source of about 430 nm is characterized by comprising two elements, a single laser light source element and a single light receiving element.

5) An optical storage device equipped with the optical head according to the item 1), further comprising a switching means for changing a laser light source and a track error detection method according to the type of the optical storage medium.

6) An optical storage device equipped with the optical head described in 2), further comprising a switching means for changing the laser light source, the numerical aperture of the objective lens, and the track error detection method according to the type of the optical storage medium. It is characterized by.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Several embodiments of the present invention will be described below with reference to the accompanying drawings to explain the present invention in further detail. FIGS. 1, 2 and 3 are views showing a schematic configuration of an optical head according to Embodiment 1 of the present invention. In FIG. 1, a laser beam 15 emitted from a semiconductor laser 1 which is an emission source of a laser beam is reflected by a beam splitter 3, passes through a wavelength filter 4, is converted into a parallel beam by passing through a collimator lens 5, and is converted into a parallel beam. After passing through the limiting element 17, it is bent by the mirror 6 in the direction of the optical disk 21, and is condensed by the objective lens 7 on the information track of the optical disk 21 having a small substrate thickness. The light reflected by the optical disc 21 enters the beam splitter 3 again through an optical path opposite to the laser beam, generates astigmatism by transmitting through the beam splitter 3, and then transmits through the concave lens 10, The light enters the light receiving element 11 and a signal is detected. The optical disk 21 having a small substrate thickness is a high-density optical disk having a substrate thickness of 0.6 mm, a track pitch of 0.5 μm, and a shortest pit length of about 0.3 μm. The semiconductor laser 1 is a blue-violet laser light source having a wavelength of 430 nm.

The wavelength filter 4 has a structure in which a multilayer film is deposited, and functions to transmit blue-violet laser light and reflect near-infrared light. The laser beam 15 collimated by the collimator lens 5 is transmitted through the optimally designed infinite objective lens 7 while passing through the substrate thickness of 0.6 mm, and is diffracted onto the information track of the optical disk 21 having a small substrate thickness. Focused at the limit spot. The objective lens 7 has a numerical aperture of 0.6, a focal length of 3.3 mm, and a design wavelength of 430 nm.

FIG. 2 shows an optical system for recording or reproducing a DVD. DVD-ROM (DVD-read only memory) as an optical disk for DVD having a track pitch of 0.74 μm and a minimum pit length of about 0.4 mm,
Although DVD-RAM (DVD-random access memory) and the like are standardized, when reproducing or recording them, the numerical aperture of the objective lens is set to 0.4 by the aperture limiting element 17. . That is, the aperture is limited so that the effective diameter of the objective lens is about 4 mm when the numerical aperture is 0.6, and becomes about 2.6 mm. By limiting the aperture in this manner, the laser light source wavelength 65
A spot diameter equivalent to the case where 0 nm was used was obtained, and recording / reproducing characteristics were also equivalent. Higher density optical disks (ROM, R, RAM) with the track pitch of about 0.5 μm and the shortest pit length of about 0.3 μm
In the case of reproducing or recording, for example, the aperture limiting element 17 functions to transmit all the incident light, and a diffraction-limited spot is formed on the information track of the optical disk 8 with the numerical aperture of the objective lens being 0.6. You. As the aperture limiting element, a liquid crystal shutter method (Reference: JJP. Vol. 36)
Various methods have been proposed, such as (1997) p481 to 485) and a method of inserting and removing a perforated plate. Here, a liquid crystal shutter type is used. Light receiving element 1
The laser light 1 incident on the semiconductor substrate mounted on the
A cross-shaped light receiving pattern (diode element) divided into four in the radial direction and the tangential direction of the optical disk 21 or 8 with respect to the center of the optical axis 5 is formed by a semiconductor process. The reflected light 15 from the optical disk is incident on the quadrant-shaped cross-shaped light receiving pattern, and a light receiving signal in which the intensity of each light is electrically converted is obtained.
By performing an operation using the light receiving signal, a focus error signal, a track error signal, and an information signal can be obtained.

First, the focus error signal uses an astigmatism method that detects the focus error signal based on astigmatism generated by the beam splitter 3.

Next, the track error signal is provided with two types of circuits that can be obtained by a phase difference method and a push-pull method. When a ROM disk is mounted, calculations are performed by the phase difference method, and when an R or RAM disk is mounted, the push-pull method is used.

The astigmatism method, the phase difference method, and the differential push-pull method are known techniques, and there are other detailed documents and the like.

On the other hand, the optical head of the present embodiment is configured to be able to reproduce even an optical disk 9 such as a CD currently on the market. 3, a laser beam 16 emitted from a semiconductor laser 2 is transmitted through a hologram element 13, reflected by a wavelength filter 4, and then transmitted through a collimator lens 5 to be converted into substantially parallel light.
And is bent by the mirror 6 in the direction of the optical disk 9, and is condensed by the objective lens 7 on the information track of the optical disk 9 having a large substrate thickness. The light reflected by the optical disk 9 is incident on the wavelength filter 4 again through the optical path opposite to the laser light, reflected by the wavelength filter 4, transmitted through the hologram element 13, and mounted in the package of the semiconductor laser 2. The signal is detected by being incident on the selected light receiving element. Optical disk 9 having a large substrate thickness
Is a CD, CD-R or CD-RW optical disc having a substrate thickness of 1.2 mm and a track pitch of 1.6 μm.
The semiconductor laser 2 is a near infrared laser light source having a wavelength of about 785 nm.

In the optical system shown in FIG.
A fixed aperture limit 18 is provided on the surface of the third wavelength filter 4 side, so that only light inside the aperture is transmitted. The numerical aperture of the objective lens 7 can be used as 0.45 by this aperture restriction.

FIG. 4 is a diagram describing in detail the state of the laser beam 16 incident on the objective lens 7 of the optical system shown in FIG. 4, the aperture limiting element 17 and the mirror 6 shown in FIG. 3 are omitted. The laser light 16 incident on the objective lens 7 is transmitted from the collimator lens 5 to the objective lens 7.
The optical path up to this point is not parallel to the optical axis 19, and the objective lens 7 is in a state of diverging light that is widened. By transmitting through the objective lens 7 in such a state, spherical aberration caused by a difference in substrate thickness between the optical disks 21 and 8 and the optical disk 9 is corrected, and a good light spot is formed on the information track of the optical disk 9. I was able to make it.
The light beam 20 passing through the effective diameter portion of the objective lens 7 and the optical axis 19
Is set to about 1.6 degrees. That is,
The position of the semiconductor laser 2 with respect to the collimator lens 5 is adjusted in the optical axis direction so that the angle θ becomes 1.6 degrees.
By setting as described above, good recording or reproducing characteristics were obtained.

The wavelength of the semiconductor laser 1 and the objective lens 7
Is slightly different depending on the design wavelength. Wavelength 48
When using 0 nm, θ = 1.58 degrees, wavelength 460 nm
The best characteristics were obtained when θ = 1.60 degrees when using .theta., 1.61 degrees when using a wavelength of 430 nm, and .theta. = 1.66 degrees when using a wavelength of 390 nm. That is, the wavelength is from 480 nm to 3 as a blue to blue-violet laser.
In the case of 90 nm, good characteristics are obtained in the range of 1.58 ≦ θ ≦ 1.66. In particular, in the case of a blue laser, θ = 1.
The best characteristics can be obtained when the angle is about 58 degrees, and in the case of a blue-violet laser, about θ = 1.6 degrees.

The semiconductor laser 2 is a laser unit having a hologram 13 mounted on the upper surface of a cap and a hologram having a light receiving element for signal detection built therein. The primary light is detected by a built-in light receiving element. The focus error signal, the track error signal, and the information signal are obtained by performing calculations using the output signal from the light receiving element.

First, the focus error signal uses an astigmatism method which detects the focus error signal based on astigmatism generated by the hologram 13.

The track error signal is detected using a differential push-pull method. A three-beam diffraction grating is formed on the surface of the hologram 13 on the light emitting element side,
The ± first-order diffracted light (sub-beam) generated by the three-beam diffraction grating is focused on the center of the information track on both sides of the information track tracked by the zero-order light (main beam) on the CD optical disc. It has been adjusted as follows. Note that the astigmatism method and the differential push-pull method are known techniques, and there are other detailed documents and the like, and therefore, the details are omitted here.

In this embodiment, a hermetic seal type package is described as the semiconductor laser 2. However, a flat package which is becoming mainstream in recent years can be used. Recently, a hologram laser unit for a CD-R has been commercialized, and its element can be mounted as it is.

The push-pull method is used as a track error signal detecting method in the reproducing optical system for a thin optical disk substrate shown in FIGS. 1 and 2 in which the semiconductor laser 1 and the beam splitter 3 are used. By inserting a diffraction grating for three beams in between, and changing the shape of the light receiving pattern of the light receiving element 11, differential detection is performed as a track error signal detection method in the same manner as in the reproduction optical system for an optical disk having a thick substrate shown in FIG. A configuration using a push-pull method is also possible.

In the optical head, the wavelength filter 4
Are used to separate the optical paths of light sources having different wavelengths, but a polarization beam splitter is mounted instead of the wavelength filter 4,
It can also be configured by providing a 90-degree angle difference between the polarization axes of the semiconductor laser 1 and the semiconductor laser 2.

The objective lens 7 is mounted on a head holder 14 and is movable by a magnetic two-axis actuator 14a. The head holder 14 is provided with the above focus error signal and the focus error signal obtained from the intensity of light condensed on the light receiving element 11 or the light receiving element mounted in the package of the semiconductor laser 2 with respect to the surface deflection and eccentricity of the optical disk 21, 8 or 9. By the track error signal,
The optical disk 21, 8 or 9 is driven so that the recording surface is always in focus and the optical disk 21, 8 or 9 always follows a track extending in the tangential direction.

Although the CD-R, which is a writable type of CD, has become widespread, the reflectance of this dye-based medium is as low as 20% or less in the vicinity of a light source wavelength of 390 nm to 480 nm. Optical heads and devices equipped with lasers cannot reproduce signals. For this reason, a laser light source having a wavelength band of 785 nm is mounted, and is configured to be used for a CD-based disc.

On the other hand, a DVD writable type DV
With respect to DR as well, the reflectance of this dye-based medium is very low at 20% or less in the vicinity of a light source wavelength of 390 nm to 480 nm, and signals cannot be reproduced by an optical head and an apparatus equipped with a laser in these wavelength bands. For this reason, the optical head shown in the present embodiment cannot reproduce a DVD-R disc, and is now widely used for a CD-R disc.
The playback-oriented configuration is adopted.

The DVD-ROM and DVD-RAM discs are less sensitive to the light source wavelength than R, and can be reproduced using the blue-violet laser light source.

The optical head described above is equipped with one objective lens, two laser light sources, and a variable aperture limiting element, so that a CD, CD-R, CD-RW, DVD-ROM, DVD-RAM In addition, recording or reproduction of ROM, R, and RAM disks with higher density can be performed.

Further, a near-infrared laser beam is made incident on an objective lens optimized with a blue-violet laser light source at a divergence angle of about 1.6 degrees, so that a single objective lens can transmit signals from optical discs having different substrate thicknesses. Recording or reproduction becomes possible.

Further, signals can be reproduced or recorded from optical disks having different track pitches by using a blue-violet laser light source and an aperture limiting element.

Further, by using a laser unit in which a light emitting element, a light receiving element, and a light splitting element are integrated in a recording / reproducing optical system of a CD system, simplification of the optical system such as reduction of the number of optical parts and the number of assembly steps is achieved. Has been realized.

(Embodiment 2) FIG. 5 shows a schematic configuration of an optical storage device 30 equipped with the optical head 25 described in Embodiment 1. The optical storage device 30 of the present example receives a drive signal 51 modulated for recording or a signal for reproduction from an information processing device such as an external computer, and the drive signal 51 receives a laser drive circuit 52 having a wavelength of 430 nm. The laser drive signal 53 having a wavelength of 785 nm is converted into a laser drive signal 54 or 55, input to the selection circuit a 75, and one of the laser drive signals is supplied to the optical head 25. The optical head 25 outputs the laser drive signal 5
4 or 55, the optical disk 50 is irradiated with a laser beam, the reflected light is received by a light receiving element for a wavelength of 430 nm or a light receiving element for a wavelength of 785 nm, and an information signal 78 which is the total light intensity of the reflected light. Is output. The information signal 78 is subjected to processing such as signal amplification by the information output circuit 56 and is output as a data output signal 57 to an external computer or the like.

The focus error signal 58 obtained from the reflected light from the optical disk 50 in the optical head 25
Is supplied to a focus servo control circuit 59, and focus control of the optical head 25 is performed via a magnetic focus servo mechanism 60. On the other hand, the first output signal 61 for calculating the tracking error signal is converted to the first tracking error signal 62 by the differential push-pull method.
Is supplied to the first arithmetic circuit 63 which outputs The second output signal 64 is supplied to a second arithmetic circuit 66 that outputs a second tracking error signal 65 by a push-pull method. Further, the third output signal 67 is supplied to a third arithmetic circuit 69 which outputs a third tracking error signal 68 by a phase difference method. The third arithmetic circuit 69 is also supplied with an information signal 78 for generating a timing signal for sampling the third output signal 67. These first, second and third tracking error signals 62, 6
5 and 68 are input to the selection circuit b70, and one of the tracking error signals is supplied to the tracking control circuit 7
1 is supplied. This tracking servo control circuit 71
Controls the tracking servo mechanism 72 based on the supplied tracking error signal, and the tracking control of the optical head 25 is performed.

The selection circuit a75 of the storage device 30 of the present embodiment includes:
According to the selection signal 81 supplied from the determination circuit 80, the laser drive signal 54 having a wavelength of 430 nm or the wavelength 785
The laser drive signal 55 of nm is selected and supplied to the optical head 25. Further, the selection circuit b70 receives the first and second signals by the selection signal 82 supplied from the determination circuit 80.
By selecting one of the second or third track error signals 62, 65 and 68, the tracking control circuit 71
To supply. Further, a determination signal 83 is supplied from the determination circuit 80 to the aperture limiting element driving circuit 73, and the aperture limiting element driving signal 74 is transmitted by the determination signal 83 to the optical head 2.
5 is supplied. The focus error signal 58, the track error signal 76, the information signal 57
The optical head 25 determines whether the substrate thickness of the optical disc 20 is 0.6 mm or 1.2 mm, whether information due to pits has been obtained from the optical disc 20 or whether information due to land / groove has been obtained. It is possible to determine whether the track pitch is 0.74 μm or not when the substrate thickness is 0.6 mm. Since various methods have been proposed for the above three types of determination methods, they are omitted here.

Table 1 below shows the optical head parameters for currently marketed optical storage media and high density optical discs to be marketed in the future that can be reproduced or recorded with the optical head and optical storage device described herein. Is shown.

[0042]

[Table 1]

The following processing is performed on these storage media in the optical storage device 30 of this embodiment. First, when the disc is loaded, the laser drive signal 55 is selected by the selection circuit a75, a laser having a laser light source wavelength of 785 nm is emitted, and the thickness of the substrate of the optical disc 20 is determined based on the output of the focus error signal 58 detected from the 785 nm light receiving element. The determination is made in the circuit 80. Next, when the substrate thickness is 1.
In the case of 2 mm, the focus servo control circuit 59 is driven to apply focus servo. The substrate thickness is 0.6m
In the case of m, the laser drive signal 54 is selected by the selection circuit a75.
Is selected, a laser beam having a laser light source wavelength of 430 nm is emitted, and the focus servo control circuit 59 is driven to apply focus servo. Next, when the substrate thickness is 0.6 mm, the judgment circuit 80 is output by the output of the track error signal 76.
The determination of the track pitch is performed within the range. When the track pitch is 0.74 μm, the aperture limit is performed by outputting the selection signal 83 and driving the aperture limiting element drive circuit. Next, based on the output of the data output signal 57, it is determined in the determination circuit 80 whether information due to the pits has been obtained. Based on the result of the determination, a determination signal 82 is sent to the selection circuit b, a track error signal is selected, the tracking control circuit 71 is driven to perform track servo, and information recording or reproduction is started. I have.

For example, when a DVD-ROM disk is mounted, the optical disk substrate thickness is 0.6 mm and the track pitch is 0.74 μm in the determination circuit 80 by the above procedure.
m and pit information are detected, and a laser light source having a wavelength of 430 nm, driving of an aperture limiting element, and a tracking error signal by a phase difference method are selected. Thereafter, recording or reproduction of information starts.

Similarly, for a DVD-RAM disk, a laser light source having a wavelength of 430 nm, an aperture limiting element drive, and a tracking error signal by a push-pull method are selected.

Similarly, for a CD-ROM disk, a tracking error signal by the differential push-pull method, in which the laser light source having a wavelength of 785 nm and the aperture limiting element are not driven, is selected.

For a CD-R disc, a laser light source having a wavelength of 785 nm and an aperture limiting element are not driven, and a tracking error signal by a differential push-pull method is selected.

For a CD-RW disc, similarly, a tracking error signal by the differential push-pull method, in which the laser light source having a wavelength of 785 nm and the aperture limiting element are not driven, is selected.

For a high-density ROM disk, a laser light source having a wavelength of 430 nm and an aperture limiting element are not driven, and a tracking error signal by the phase difference method is selected.

For a high-density-R disc, a laser light source having a wavelength of 430 nm and a tracking error signal by a push-pull method, in which the aperture limiting element is not driven, are similarly selected.

For a high-density RAM disk, similarly, a laser light source having a wavelength of 430 nm and an aperture limiting element are not driven, and a tracking error signal by a push-pull method is selected.

When a DVD-R disc is mounted,
In addition to observing the presence or absence of pre-pits, the reflectance, and the like in the judgment circuit 80 in addition to the above judgment, when it is judged that the disc is a DVD-R disc, the emission of the laser light source is stopped and the data output signal 7
7 outputs an error message.

As described in the first embodiment, the DVD-
When the optical head using the differential push-pull method is used for the tracking error detection method of the RAM, the high density-R, and the high density-RAM, the second arithmetic circuit 66 shown in FIG. It goes without saying that the circuit system of the optical storage device 30 can be simplified, for example, by simplifying the processing of 80.

As described above, the optical storage device 30 of the present embodiment can perform stable focusing and tracking control on various optical disks having different disk thicknesses, track pitches, and information recording methods as described above. In addition, information can be reproduced or recorded stably and reliably. Therefore, the user does not need to identify the difference between a CD, a DVD, a higher-density disk, and ROM, R, and RAM, and collectively performs processing on various optical disks with one optical storage device of the present example. I can do it.

[0055]

As described above, the optical head of the present invention comprises two laser light sources, a blue-violet laser and a near-infrared laser, and one objective lens optimally designed for an optical disk having a thin substrate. CD, CD-
R, CD-RW and DVD-ROM, DVD-RA
It is possible to provide an optical head capable of reproducing or recording M, ROM, R, and RAM disks with higher density.

A signal is reproduced from an optical disc having a different substrate thickness with one objective lens by causing near-infrared laser light to enter the objective lens optimized with a blue-violet laser light source at a divergence angle of about 1.6 degrees. Or recording becomes possible.

Further, signals can be reproduced or recorded from optical disks having different track pitches by using a blue-violet laser light source and an aperture limiting element.

Further, by using a laser unit in which a light emitting element, a light receiving element, and a light splitting element are integrated in a CD recording / reproducing optical system, simplification of the optical system such as reduction of the number of optical parts and the number of assembly steps is achieved. Has been realized.

Further, in the optical drive device equipped with the optical head of the present invention, stable focusing and tracking control can be performed for various optical disks having different disk thicknesses, track pitches and information recording methods. Information can be reproduced or recorded stably and reliably. Therefore, the user can use CD, DV
D, higher density disk or ROM,
It is not necessary to discriminate the difference between R and RAM, and it is possible to provide an optical storage device that can perform collective processing on various optical disks with one optical storage device of this example.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a schematic configuration of an optical head according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a schematic configuration of an optical head according to a first embodiment of the present invention.

FIG. 4 is a detailed view of an optical head objective lens unit shown in FIG. 2 according to the first embodiment of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of an optical storage device using the optical head shown in FIGS.

FIG. 6 is a diagram showing a schematic configuration of a conventional optical head.

[Explanation of symbols]

 1, 2, 101, 102, semiconductor laser 3, 103, beam splitter 4, 104, wavelength filter 5, 105, collimator lens 6, 106, mirror 7, 107, 122, objective lens 8, 21 ··· Optical disk with substrate thickness of 0.6 mm 9 ··· Optical disk with substrate thickness of 1.2 mm 10, 110, 123 ··· Concave lens 11, 111, 112 ··· Light receiving element 13 ··· Hologram element 14 ··· Head holder 14a ··· 2 Axis actuator 15, 16 Laser beam 17 Aperture limiting element 18 Aperture limit 19 Optical axis 20 Light beam 21, 50 Optical disk 25 Optical head 30 Optical storage device 51 Drive Signals 52 and 53 Laser drive circuits 54 and 55 Laser drive signals 56 Information output circuits 57 Data output signals 8. Focus error signal 59 Focus servo control circuit 60 Focus servo mechanism 61 First output signal 62 First tracking error signal 63 First arithmetic circuit 64 Second Output signal 65 Second tracking error signal 66 Second arithmetic circuit 67 Third output signal 68 Third tracking error signal 69 Third arithmetic circuit 70 Selection circuit b 71 tracking control circuit 72 tracking servo mechanism 73 aperture restricting element driving circuit 74 aperture restricting element driving signal 75 selection circuit a 76 track error signal 77 data output signal 78 information Signal 80 judgment circuit 81 selection circuit 82 selection circuit 83 selection circuit

Claims (6)

[Claims] A plurality of laser light sources having different wavelengths and an infinite objective lens optimally designed at a first wavelength;
In an optical head for reproducing or recording a signal in a method of switching and using the laser light source according to an optical storage medium, the first wavelength is about 430 nm, and the second wavelength is about 785 nm. A near-infrared laser light source, the first wavelength laser light incident on the objective lens is incident parallel to the optical axis, the second wavelength laser light is incident on the divergent light, the divergence angle of the divergent light An optical head characterized in that 1.58 ≦ θ ≦ 1.66, where θ (degree) is an angle between a light ray passing through the effective diameter of the objective lens and the optical axis. 2. A signal reproducing method comprising: a plurality of laser light sources having different wavelengths; and an objective lens optimally designed at a first wavelength, wherein the laser light source is switched and used according to an optical storage medium. Alternatively, in an optical head that performs recording, the first wavelength is a blue-violet laser light source of about 430 nm, the second wavelength is a near-infrared laser light source of about 785 nm, and the first wavelength of the first wavelength incident on the objective lens. A variable aperture limiting means capable of variably limiting the aperture of the laser light in two values, and an aperture limiting means limiting the aperture of the second wavelength laser light incident on the objective lens are further provided. Optical head. 3. A variable aperture limiting means capable of switching a numerical aperture of an objective lens between about 0.6 and about 0.4 when emitting a laser beam of a first wavelength. 3. The optical head according to claim 2, further comprising an aperture limiting unit that sets the numerical aperture of the objective lens to 0.45 when emitting a laser beam having a wavelength of (1). 4. An optical system using a laser light source having a wavelength of about 785 nm is a unit in which a light receiving element for receiving an information signal and a servo error signal from an optical storage medium and the laser light source are both mounted in the same package. Yes, about 430
3. The optical head according to claim 1, wherein the optical system using the laser light source of about nm has two elements: a single laser light source element and a single light receiving element. 5. An optical head according to claim 1, further comprising:
An optical storage device comprising: a switching unit that changes a laser light source and a track error detection method according to a type of an optical storage medium. 6. An optical head according to claim 2, wherein:
An optical storage device comprising: a switching unit that changes a laser light source, a numerical aperture of an objective lens, and a track error detection method according to a type of an optical storage medium.