JPH10112057A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of satisfactorily recording/ reproducing an information signal against plural kinds of optical disks having the different thickness of transparent substrate and the different signal recording density. SOLUTION: A collimator lens 3 is used in common for a 1st optical path through a semiconductor leser 7 to a 1st objective lens 4 and a 2nd optical path through a laser coupler 1 to a 2nd objective lens 5, and an intermediate lens 8 is arranged on the 1st optical path. By the intermediate lens 8, the filtering condition against an entrance pupil of the collimator lens 3 of the semiconductor laser 7 is improved in the manner of changing the length of the optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an optical pickup device for writing and reading information signals on an optical recording medium such as an optical disk.

[0002]

2. Description of the Related Art Conventionally, optical recording media such as optical disks and optical cards have been proposed as recording media for information signals.
An optical pickup device for writing and reading information signals to and from such an optical recording medium has been proposed.

Such an optical recording medium has a transparent substrate made of a transparent material such as polycarbonate and a signal recording layer formed on one main surface of the transparent substrate. In order to write and read information signals on such an optical recording medium, the optical pickup device is used to condense a light beam on the surface of the signal recording layer of the optical recording medium, that is, on the signal recording surface. Irradiate. The optical pickup device includes a light source and an objective lens for condensing a light beam emitted from the light source. Further, the optical pickup device has a photodetector such as a photodiode for detecting a light beam reflected by the signal recording surface of the light beam irradiated on the signal recording surface.

[0004] In such an optical recording medium, the recording density of information signals has been increased in order to use it as a recording medium for audio signals and image signals.
In order to record and reproduce information signals on an optical recording medium with a higher recording density, the objective lens should have a larger numerical aperture (NA) (for example, 0.6), and the luminous flux should be higher. Is set to a shorter wavelength (for example, 63
(0 nm to 650 nm), it is necessary to reduce a beam spot formed by condensing the light beam on the optical recording medium.

[0005] However, when the numerical aperture of the objective lens increases, the inclination of the optical recording medium with respect to the optical axis of the objective lens, the thickness unevenness of the transparent substrate of the optical recording medium, and the light flux on the optical recording medium. Is less tolerable to defocus (defocus), and it becomes difficult to record and reproduce information signals on this optical recording medium.

For example, when an inclination (skew) of the optical recording medium with respect to the optical axis of the objective lens occurs, a wavefront aberration occurs in a light beam condensed on the signal recording surface,
The electric signal (RF output) output from the photodetector is affected. This wavefront aberration is about 1 cube of the numerical aperture of the objective lens and the tilt angle (skew angle) of the optical recording medium.
The third-order coma generated in proportion to the power is dominant. Therefore, the permissible value for the tilt of the optical recording medium is inversely proportional to the cube of the numerical aperture of the objective lens, that is, it decreases as the numerical aperture increases.

[0007] Thickness 1.2 mm, diameter 80 mm or 12
An optical disk (hereinafter referred to as a so-called “compact disk (C),” which is configured to have a transparent substrate formed of a 0 mm disc-shaped polycarbonate and is widely used at present.
D))), the inclination angle is ± 0.5.
° to ± 1 °.

In such an optical disk, if the numerical aperture of the objective lens is increased (for example, to about 0.6 or more), the above-mentioned wavefront aberration occurs in the light beam irradiated on the optical disk, and The beam spot on the signal recording surface has an asymmetric shape, causing significant intersymbol interference, making accurate signal reproduction difficult. (In the case of a "compact disc", the optical pickup device includes a light beam emitted from a light source. Of which the wavelength is 780 nm and the numerical aperture of the objective lens is 0.45).

The amount of such third-order coma is proportional to the thickness of the transparent substrate of the optical disk. Therefore, by reducing the thickness of the transparent substrate (for example, to 0.6 mm), third-order coma can be reduced by half. When the coma aberration is to be reduced in this way, as shown in FIG. 14, the optical disk has a transparent substrate having a thickness of 1.2 mm (D2) and the transparent substrate has a thickness of 0.2 mm. 6 mm (D1) will be used together. Such a transparent substrate has a thickness of 0.6 m.
m, for example, a so-called “SD”,
Alternatively, a “digital video disk (DVD)” has been proposed.

When a plane-parallel plate having a thickness t is inserted into the optical path of the convergent light beam condensed by the objective lens, t is related to the thickness t and the numerical aperture NA of the objective lens. × (NA) Spherical aberration proportional to ⁴ occurs.

The objective lens is designed so that the spherical aberration is corrected. That is, since the amount of spherical aberration that occurs when the thickness of the transparent substrate varies, the objective lens is designed to be adapted to the predetermined thickness of the transparent substrate.

Then, for example, using the first objective lens 104 designed and adapted to the first optical disc D1 having a transparent substrate having a thickness of 0.6 mm, a transparent substrate having a thickness of 1.2 mm is provided. A second optical disc D2 (for example,
When recording and reproducing information signals on a “compact disk”, a write-once optical disk, or a magneto-optical disk, the difference in thickness between these transparent substrates (0.6 m
m) significantly exceeds the allowable range of the thickness error of the transparent substrate that the optical pickup device can cope with. In this case, the first objective lens 104 cannot correct the spherical aberration generated due to the difference in the thickness of the transparent substrate, and cannot perform good recording and reproduction of the information signal.

Conventionally, as shown in FIG. 14, a first objective lens 104 adapted to the first optical disc D1 and a second objective lens 104 adapted to the second optical disc D2 are used.
The objective lens 104 and the objective lens 105 are provided according to whether the optical recording medium on which information signals are recorded or reproduced is the first or second optical disc. There has been proposed an optical pickup device in which 105 is interchangeably used.

Also, a so-called “Compact Disc-Recordable (CD-R)”
As described above, in a write-once optical disc having a signal recording layer made of an organic dye, recording and reproduction of information signals
Due to the wavelength dependency, an information signal cannot be read unless a light beam of a predetermined wavelength is used. Therefore, in order to enable reading of an information signal from such a write-once optical disc, different wavelengths (for example, 630 nm to 650 nm and 780 nm) are used as shown in FIG.
An optical pickup device having a first light source and a second light source that emits a light flux of nm (nm) has been proposed.

That is, this optical pickup device comprises:
A semiconductor laser 107 serving as a first light source, a composite light receiving / emitting device (laser coupler) 101 having a semiconductor laser chip serving as a second light source, and a light beam emitted from the semiconductor laser 107 and the composite light receiving / emitting device 101 are incident thereon. The multiplexing prism 102 for superimposing light beams, the multiplexing prism 10
The collimator lens 103 on which the light beam having passed through the second collimator lens 103 is incident, and the first light beam on which the light beam having passed through the collimator lens 103 is incident
And second objective lenses 104 and 105, and a photodetector 109.

A first laser beam having a first wavelength (for example, 630 nm to 650 nm) emitted from the semiconductor laser 107 is deflected by 90 ° by a flat beam splitter 106 and is incident on the multiplex prism 102. You. The semi-transmissive film surface of the multiplexing prism 102 has an inclination of 45 ° with respect to the optical axis of the first laser beam from the semiconductor laser 107 and the optical axis of the second laser beam from the composite light receiving / emitting element 101. It is arranged to be. The first laser beam from the semiconductor laser 107 is reflected by the semi-transmissive film surface in the multiplexing prism 102 and is deflected by 90 °.
It is injected more. The first laser beam emitted from the multiplexing prism 102 is incident on a collimator lens 103 and is converted into a parallel beam by the collimator lens 103.

On the other hand, the second laser beam of the second wavelength (for example, 780 nm) from the composite light-receiving / emitting element 101 is:
The light passes through the semi-transmissive film surface of the multiplexing prism 102, enters the collimator lens 103 via the same optical path as the first laser beam reflected by the semi-transmissive film surface, and is collimated by the collimator lens 103. A luminous flux is made.

The first optical disk D1 (so-called "S
D "or" Digital Video Disc (DV
When writing or reading an information signal for D))), only the semiconductor laser 107 is turned on, and the first laser beam passing through the collimator lens 103 is incident on the first objective lens 104. As a result, the first objective lens 104 is positioned on the optical path of the first laser beam corresponding to the collimator lens 103. At this time, the first laser beam is incident on the first objective lens 104.

The first laser light beam incident on the first objective lens 104 is condensed and irradiated on the signal recording surface of the first optical disk D1 by the first objective lens 104. At this time, the first laser beam is irradiated onto the first optical disc D1 from the transparent substrate side of the first optical disc D1, passes through the transparent substrate, and is condensed on the signal recording surface. You. The first objective lens 104 is moved together with the second objective lens 105 by being supported by a biaxial actuator (not shown), so that an information signal on the signal recording surface is always recorded ( The first laser beam is focused on a recording track).

In the first optical disc D1, the first laser light beam having passed through the first objective lens 104 is condensed and irradiated, so that information is applied to a position irradiated with the first laser light beam. The signal is recorded. Also,
The first laser beam radiated on the signal recording surface has a light quantity, a light amount, in accordance with an information signal recorded on the signal recording surface.
Alternatively, the first objective lens 1 may be used as a first reflected light beam whose polarization direction is modulated and reflected by the signal recording surface.
Return to 04.

The first signal reflected by the signal recording surface is
Is reflected by the multiplexing prism 102 through the first objective lens 104 and the collimator lens 103.
Leads to. The first reflected light beam is transmitted to the multiplexing prism 10
2 is reflected by the semi-transmissive film surface of the semiconductor laser 1
It is deflected to the path returning to 07. The first reflected light flux reaches the beam splitter 106, passes through the beam splitter 106, and travels to the photodetector 109.

The photodetector 109 is a light receiving element such as a photodiode, and the beam splitter 106
Receives the first reflected light beam that has passed through and converts it into an electric signal.
The information signal recorded on the first optical disc D1 is reproduced based on the electric signal output from the photodetector 109.

When writing or reading information signals to or from the second optical disk D2 (so-called "compact disk (CD)", "compact disk recordable (CD-R)"), Only the semiconductor laser chip of the light receiving / emitting element 101 is turned on, and the second objective lens 105 is set to the collimator so that the second laser beam passing through the collimator lens 103 is incident on the second objective lens 105. The second laser beam corresponding to the lens 103 is positioned on the optical path. At this time, the second laser beam is
Is incident on the objective lens 105.

The second laser light beam incident on the second objective lens 105 is condensed and irradiated on the signal recording surface of the second optical disc D2 by the second objective lens 105. At this time, the second laser beam is irradiated onto the second optical disc D2 from the transparent substrate side of the second optical disc D2, passes through the transparent substrate, and is focused on the signal recording surface. You. The second objective lens 105, together with the first objective lens 104, is moved and supported by the biaxial actuator, so that the information signal on the signal recording surface is always recorded (recorded). The second laser beam is focused on a track).

In the second optical disk D2, the second laser light beam having passed through the second objective lens 105 is condensed and irradiated, so that information is applied to a position irradiated with the second laser light beam. The signal is recorded. Also,
The second laser beam radiated on the signal recording surface has a light amount, a light amount, in accordance with an information signal recorded on the signal recording surface.
Alternatively, the second objective lens 1 may be used as a second reflected light beam whose polarization direction is modulated and reflected by the signal recording surface.
Return to 05.

The second signal reflected by the signal recording surface
Is reflected by the multiplexing prism 102 through the second objective lens 105 and the collimator lens 103.
Leads to. The second reflected light flux is applied to the multiplex prism 10
2 through the semi-transmissive film surface, and
Return to In the composite light receiving and emitting element 101, the second reflected light beam is detected by a photodetector of the light receiving and emitting element 101. That is, the photodetector receives the second reflected light flux and converts it into an electric signal. The information signal recorded on the second optical disc D2 is reproduced based on the electric signal output from the photodetector.

[0027]

By the way, like the optical pickup device described above, the first optical disk D1
The optical path from the semiconductor laser 107 serving as the first light source to the first objective lens 104, and the optical path for the second optical disc D2, that is, the light path serving as the second light source. In an apparatus using the same collimator lens 103 in the optical path from the semiconductor laser chip of the light emitting element 101 to the second objective lens 105, in any one of the optical paths, the fill condition is not optimal. There is.

The fill condition is determined by the divergence angle of the light beam emitted from the light source, the optical path length from the light source to the entrance pupil of the collimator lens, and the diameter of the entrance pupil. That is,
When a divergent light beam having a Gaussian distribution emitted from a light source at a certain divergence angle enters a collimator lens having a constant entrance pupil diameter through a sufficiently long optical path length than the light source,
The ratio of the amount of light incident on the collimator lens and actually illuminating the optical recording medium with respect to the total amount of light emitted from the light source is reduced. At this time, since the ratio of the light intensity at the outermost periphery of the entrance pupil to the light intensity at the center of the entrance pupil of the collimator lens is increased, as shown in FIG. 11 and FIG. The light spot becomes smaller (shown by EFL 25 mm in FIGS. 11 and 12). Conversely, when the optical path length from the light source to the collimator lens is short, the ratio of the amount of light incident on the collimator lens and actually illuminating the optical recording medium with respect to the total amount of light emitted by the light source increases. As shown in FIGS. 11 and 12, the ratio of the light intensity at the outermost periphery of the entrance pupil to the light intensity at the center of the entrance pupil of the collimator lens is reduced.
The condensed spot after passing through the objective lens becomes large (in FIG. 11 and FIG. 12, indicated by EFL 17 mm).

In the above-mentioned optical disk, the light intensity (board power) of the light beam irradiated on the signal recording surface is required to be higher than a predetermined intensity. Therefore, the light emission output of the light source and the light intensity of the light beam emitted from this light source are required. When the divergence angle is determined, the optical path length from the light source to the entrance pupil of the collimator lens, that is, the focal length of the collimator lens needs to be shorter than a predetermined optical path length.

For example, in the case of the "digital video disk (DVD)" which is the first optical disk D1, the light intensity of the light beam irradiated on the signal recording surface is as follows.
0.2 mW or more is required. Considering the characteristics of the semiconductor laser used as the light source for this “digital video disk (DVD)”, FIGS.
As shown in Table 1 below, the optical path length from this semiconductor laser to the entrance pupil of the collimator lens is 28
mm or less.

[0031]

[Table 1]

However, in the optical system for this "digital video disk (DVD)", since the recording density of the information signal on the signal recording surface is high, the diameter of the condensed spot formed by the objective lens is large. Needs to be as small as possible. In this sense, it is desirable to make the optical path length from the semiconductor laser to the entrance pupil of the collimator lens as long as possible. Therefore, this "digital
In the optical system for "video disk (DVD)",
The optical path length from the semiconductor laser to the entrance pupil of the collimator lens must be near 28 mm.

On the other hand, in the "compact disc (CD)" and the "compact disc recordable (CD-R)" which are the second optical discs D2, the light of the luminous flux irradiated on the signal recording surface is used. As strength
0.3 mW or more is required. 9 and 10 in consideration of the characteristics of the semiconductor laser used as a light source for these “compact disk (CD)” and “compact disk recordable (CD-R)”.
As shown in [Table 1], the optical path length from this semiconductor laser to the entrance pupil of the collimator lens is 19 m.
m or less.

As described above, the optical system for the “digital video disk (DVD)” and the “compact
Disc (CD) "and the above" Compact Disc
When the collimator lens is shared with the optical system for "recordable (CD-R)", the optimum fill condition cannot be satisfied for each optical system.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and has been proposed for optimally filling conditions for a plurality of types of optical recording media having different transparent substrate thicknesses and information signal recording densities. Is satisfied, and the light intensity of the light beam irradiated on the signal recording surface of the optical recording medium and the condensing spot diameter of the light beam formed on the signal recording surface are required and sufficient, and the information signal An object of the present invention is to solve the problem of providing an optical pickup device capable of performing recording and reproduction satisfactorily.

[0036]

In order to solve the above-mentioned problems, an optical pickup device according to the present invention comprises a first light source and a second light source which emit light beams having different wavelengths, and a light source which emits light beams from the first light source. And a first collimator lens corresponding to a first optical recording medium to which a light beam from the first light source passing through the collimator lens is incident. An objective lens, a second objective lens corresponding to a second optical recording medium on which a light beam from the second light source passing through the collimator lens is incident, and any one of the first and second light sources An intermediate lens disposed on an optical path between one of the collimator lenses and the first or second intermediate lens.
And a lens for changing the optical path length between the light source and the collimator lens.

In the optical pickup device according to the present invention, the first and second light sources emitting light beams having different wavelengths, the light beam emitted from the first light source, and the light beam emitted from the second light source are provided. An objective lens to which a light beam is incident; and an intermediate lens disposed on an optical path between one of the first and second light sources and the objective lens. Alternatively, it is a lens that changes the optical path length between the second light source and the objective lens.

Therefore, in the optical pickup apparatus according to the present invention, the focal length of the collimator lens or the objective lens shared in the respective optical paths corresponding to the first and second light sources and the characteristics of the respective light sources ( The fill condition determined by the light emission output and the divergence angle of the emitted light beam can be different for each optical path by the intermediate lens.

[0039]

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, an optical pickup device according to the present invention is used as a first optical recording medium in which a transparent substrate is an optical recording medium having a thickness of 0.6 mm and a second optical recording medium. The thickness of the transparent substrate is 1.
This is configured as an optical pickup device capable of recording and reproducing information signals on and from both a 2 mm optical recording medium and a second optical disk. This optical pickup device will be described in the following order.

[1] Configuration of First and Second Optical Disks [2] Configuration of Optical Pickup Device [3] Configuration of Biaxial Actuator [4] Adjustment Method of Optical Pickup Device [5] Configuration of Recording / Reproducing Device [6] ] Configuration without a collimator lens (finite objective lens)

[1] Configuration of First and Second Optical Disks As shown in FIGS. 1 and 2, the first optical disk D1 is made of a disc-shaped polycarbonate (Polycarbonate) having a thickness of 0.6 mm and a diameter of 120 mm. It has a transparent substrate formed and a signal recording layer formed on one main surface of the transparent substrate. The interface between the transparent substrate and the signal recording layer is a signal recording surface. The first optical disc D1 has a wavelength of 630 nm to 650 nm.
The information signal is recorded and reproduced by an m-laser beam through an objective lens having a numerical aperture (NA) of 0.6.

As the first optical disk D1, for example, a so-called “SD” or
"Digital Video Disc:
DVD) has been proposed.

As shown in FIGS. 1 and 2, the second optical disk D2 has a transparent substrate formed of a disc-like polycarbonate having a thickness of 1.2 mm and a diameter of 80 mm or 120 mm, and a main substrate of the transparent substrate. And a signal recording layer formed on the surface portion. The interface between the transparent substrate and the signal recording layer is a signal recording surface. The second optical disk D2 is configured to record and reproduce information signals by a laser beam having a wavelength of 780 nm via an objective lens having a numerical aperture of 0.45.

Examples of such a second optical disk D2 include a so-called “Compact Disc (CD)” and a “Compact Disc-Recordable (CD)”.
R) "has been proposed.

[2] Configuration of Optical Pickup Device The optical pickup device according to the present invention has an optical system block 39 as shown in FIG.
Various optical devices and electronic devices constituting an optical path are built in the device 9. The optical system block 39 has a shaft insertion hole that is movably supported in a recording / reproducing device described later. Thrust bearings 40 and 41 are provided at one end and the other end of the shaft insertion hole, respectively.

This optical pickup device has a semiconductor laser 7 as a first light source, as shown in FIGS. The semiconductor laser 7 emits a first laser beam which is linearly polarized coherent light. This first laser beam is a divergent beam having a Gaussian distribution. The wavelength of the first laser beam is 630
nm to 650 nm (for example, 635 nm).

The first laser beam passes through the intermediate lens 8 and reaches the flat beam splitter 6. As shown in FIG. 4, the intermediate lens 8 is a lens whose surface 1 (incident surface) is an aspheric concave surface and whose surface 2 (exit surface) is an aspheric convex surface, and is made of an acrylic synthetic resin material or glass. It is formed by a mold. The intermediate lens 8 functions to change the optical path length of the first laser beam to the collimator lens 3 described later. This intermediate lens 8
Is mounted in a cylindrical lens holder 43,
Along with the lens holder 43, movement adjustment in the direction of the optical axis is enabled (after the movement adjustment is completed, the lens holder 43 is adhered and fixed to the optical system block 39).

The beam splitter 6 is formed in the shape of a flat plate, and has a main surface arranged at an angle of 45 ° with respect to the optical axis of the first laser beam from the semiconductor laser 7. The beam splitter 6 reflects the first laser beam from the semiconductor laser 7 by the main surface on the semiconductor laser 7 side and deflects it by 90 °.

The laser beam reflected by the beam splitter 6 enters the multiplexing prism 2. In the multiplexing prism 2, the first laser beam is reflected by the semi-transmissive film surface of the multiplexing prism 2,
The light is deflected by 0 ° and emitted from the multiplexing prism 2.
The first laser light beam emitted from the multiplexing prism 2 is incident on a collimator lens 3 and is converted into a parallel light beam by the collimator lens 3 to form a first objective lens 4.
Is incident on. The multiplexing prism 2 and the collimator lens 3 have two wavelengths (630 nm to 650 nm).
And 780 nm).

The first objective lens 4 is shown in FIGS.
As shown in the figure, together with a second objective lens 5 described later,
It is movably supported by a biaxial actuator 38. One of these first and second objective lenses 4 and 5 is interchangeable with each other, and one of them is the collimator lens 3.
, That is, the position where the laser beam emitted through the collimator lens 3 is incident.

The first objective lens 4 focuses the first laser beam emitted from the semiconductor laser 7 on the signal recording surface of the first optical disc D1. That is, the first laser light beam incident on the first objective lens 4 is condensed and irradiated on the signal recording surface of the first optical disc D1 by the first objective lens 4.

At this time, the first laser beam is irradiated onto the first optical disc D1 from the transparent substrate side of the first optical disc D1, passes through the transparent substrate, and passes through the surface of the signal recording layer. The light is condensed on the signal recording surface as a portion. The first objective lens 4 is always moved on the signal recording surface by being moved in an optical axis direction indicated by an arrow F in FIG. 1 and a direction orthogonal to the optical axis indicated by an arrow T in FIG. The first (recording track) where the information signal is recorded
Is focused.

The first objective lens 4 has a numerical aperture (N
A) is 0.6. The first objective lens 4
Is generated in proportion to t × (NA) ⁴ when a parallel flat plate having a thickness of t = 0.6 mm is inserted into the optical path of the convergent light beam condensed by the first objective lens 4. It is designed so that spherical aberration is corrected. That is, the first objective lens 4 is designed so as to be adapted to the first optical disk D1 having a thickness of the transparent substrate of 0.6 mm.

In the first optical disc D1, the first laser light beam having passed through the first objective lens 4 is condensed and irradiated, so that the first laser light beam is irradiated on the first laser light beam. The signal is recorded. Further, the first laser beam irradiated on the signal recording surface is reflected by the signal recording surface after modulating the amount of light or the polarization direction according to the information signal recorded on the signal recording surface. The first reflected light flux returns to the first objective lens 4.

The first reflected light returning to the first objective lens 4 returns to the beam splitter 6 via the first objective lens 4, the collimator lens 3, and the multiplexing prism 2. Here, the first reflected light flux passes through the beam splitter 6 and is incident on the photodetector 9. The photodetector 9 includes a plurality of light receiving units, and outputs an electric signal having a level corresponding to the light intensity of the incident first reflected light beam.

As shown in FIGS. 1 and 3, the optical pickup device has a light receiving / emitting composite element (laser coupler) having a semiconductor laser chip 12 serving as a second light source.
1 is provided. The composite light-receiving / emitting device 1 is configured such that a semiconductor laser chip 12 serving as a light source and a plurality of photodetectors 15 and 16 are arranged and formed on a silicon substrate 10. The semiconductor laser chip 12 is provided on a heat sink 11 provided on the semiconductor substrate 10. Then, on the plurality of light detection units 15 and 16,
A beam splitter prism 13 is provided.

In the composite light receiving and emitting device 1, the second laser beam emitted from the semiconductor laser chip 12 is reflected by the inclined surface portion 14 having an inclination of 45 °, which is one end of the beam splitter prism 13, and The light is emitted in a direction perpendicular to the silicon substrate 10. This second
Is a divergent light beam having a Gaussian distribution. The wavelength of the second laser beam is 780 nm.
It is. The second laser beam emitted from the composite light-receiving / emitting element 1 in this manner passes through the multiplexing prism 2 and enters the collimator lens 3. That is,
The second laser light flux transmitted through the multiplexing prism 2 travels on the same optical path as the first laser light flux emitted from the multiplexing prism 2. Then, the second laser beam converted into a parallel light beam by the collimator lens 3 is incident on the second objective lens 5.

The second objective lens 5 is shown in FIGS.
As shown in the figure, the first objective lens 4 and the first objective lens 4 are movably supported by the biaxial actuator 38. As described above, one of the first and second objective lenses 4 and 5 is interchangeable with each other at a position corresponding to the collimator lens 3, that is, a laser emitted through the collimator lens 3. The position where the light beam is incident is set.

The second objective lens 5 converts the second laser beam emitted from the light emitting / receiving composite element 1 into the second laser beam.
On the signal recording surface of the optical disc D2. That is, the second laser light beam incident on the second objective lens 5 is condensed and irradiated on the signal recording surface of the second optical disc D2 by the second objective lens 5.

At this time, the second laser beam is irradiated onto the second optical disc D2 from the transparent substrate side of the second optical disc D2, passes through the transparent substrate, and passes through the surface of the signal recording layer. The light is condensed on the signal recording surface as a portion. By moving the second objective lens 5 in the optical axis direction and in a direction orthogonal to the optical axis, the second objective lens 5 is always moved to a position (recording track) where an information signal is recorded on the signal recording surface. Is focused.

The second objective lens 5 has a numerical aperture (N
A) is 0.45. The second objective lens 5
Is generated in proportion to t × (NA) ⁴ when a parallel plane plate having a thickness of t = 1.2 mm is inserted into the optical path of the convergent light beam condensed by the second objective lens 5. It is designed so that spherical aberration is corrected. That is, the second objective lens 5 is designed to be adapted to the second optical disc D2 having a transparent substrate having a thickness of 1.2 mm.

In the second optical disk D2, the second laser light beam having passed through the second objective lens 5 is condensed and irradiated, so that information is applied to the position irradiated with the second laser light beam. The signal is recorded. Further, the second laser beam radiated onto the signal recording surface is modulated in light amount in accordance with the information signal recorded on the signal recording surface, and is reflected by the signal recording surface. The light returns to the second objective lens 5 as a light beam.

The second reflected light flux returning to the second objective lens 5 returns to the inclined surface section 14 via the collimator lens 3 and the multiplexing prism 2. This inclined surface 1
The second reflected light flux returning to 4 enters the beam splitter prism 13 while being refracted by the inclined surface portion 14. A part of the second reflected light flux that has entered the beam splitter prism 13 is emitted to the lower surface of the beam splitter prism 13, and the rest is reflected by the top surface of the beam splitter prism 13, and then is returned again. When the light is emitted to the lower surface of the prism 13, the light is radiated onto each of the photodetectors 15 and 16. Each of the light detectors 15 and 16 outputs an electric signal corresponding to the emitted light beam.

In this optical pickup device, a first optical path from the semiconductor laser 7 to the collimator lens 3 and a second optical path from the semiconductor laser chip 12 of the composite light receiving and emitting element 1 to the collimator lens 3 In each of the cases, the fill condition is in a favorable state.

The fill conditions include the divergence angle of each laser beam emitted from the semiconductor laser 7 and the semiconductor laser chip 12, the optical path length from the semiconductor laser 7 and the semiconductor laser chip 12 to the entrance pupil of the collimator lens 3, And the diameter of the entrance pupil. In this optical pickup device, the focal length of the collimator lens 3, that is, the semiconductor laser chip 12
Further, the optical path length up to the entrance pupil of the collimator lens 3 is set so as to satisfy the optimum fill condition for recording and reproduction with respect to the second optical disc D2.

For example, as shown in Table 1 above,
3. The emission output (maximum) of the semiconductor laser chip 12 is 4.
5 mW, the divergence angle of the emitted light beam is the second optical disc D2
12 ° (deg) in the radial direction (rad) and 24 ° (deg) in the tangential direction (tan),
Assuming that the diameter of the entrance pupil of the collimator lens 3 is 4.5 mm, the light intensity (board surface power) of the second laser beam radiated onto the signal recording surface of the second optical disc D2.
Assuming that 0.3 mW or more is required, the optical path length from the semiconductor laser chip 12 to the entrance pupil of the collimator lens 3 is 19, as shown in FIGS.
mm or less, for example, 17 mm.

In this optical pickup device, the collimator lens 3 is provided by the semiconductor laser 7.
The optical path length up to the entrance pupil is extended by the provision of the intermediate lens 8 so that the optimum fill condition for recording and reproduction with respect to the first optical disc D1 is satisfied.

For example, as shown in Table 1 above,
The emission output (maximum) of the semiconductor laser 7 is 3.5 mW,
The divergence angle of the emitted light beam is 33 ° (deg) in the radial direction (rad) and 8 ° (deg) in the tangential direction (tan) of the first optical disc D1, and the diameter of the entrance pupil of the collimator lens 3 is Assuming that it is 4.5 mm,
The light intensity (board surface power) of the first laser beam radiated onto the signal recording surface of the first optical disk D1 is as follows:
Assuming that 0.2 mW or more is required, as shown in FIGS. 7 and 8, the optical path length from the semiconductor laser 7 to the entrance pupil of the collimator lens 3 needs to be 28 mm or less, for example, 25 mm. It has become. In this optical pickup device, the optical path length of the first optical path from the semiconductor laser 7 to the collimator lens 3 is set as long as possible within a range where a sufficient board surface power can be secured. 3, the ratio of the light intensity at the outermost periphery of the entrance pupil to the light intensity at the center of the entrance pupil is increased.
L25 mm), the condensed spot after passing through the first objective lens 4 is smaller than the case where the intermediate lens 8 is not provided (indicated by EFL 17 mm in FIGS. 11 and 12). Has been made smaller.

As described above, in this optical pickup device, the digital video disk (DV
D) ”(D1) and the optical system for the“ compact disc (CD) ”and the“ compact disc recordable (CD-R) ”(D2). , The optimum fill condition is satisfied for each optical system.

In this optical pickup device, when the tracking error signal is detected for the first optical disk D1 by the so-called three-beam method, the beam splitter 6 is used by the semiconductor laser 7.
A grating (diffraction grating) is provided on the optical path leading to.
In this optical pickup device, when a focus error signal is detected for the first optical disc D1 by the so-called astigmatism method, a cylindrical lens is provided on the optical path from the beam splitter 6 to the photodetector 9. Is provided.

Further, the optical pickup device may be configured by disposing the intermediate lens only on the second optical path from the semiconductor laser chip 12 of the composite light-receiving / emitting element 1 to the collimator lens 3. . In this case, the collimator lens 3 is connected to the semiconductor laser 7
Has a focal length (for example, 25 mm) that satisfies the fill condition for the first optical path from. In this case, the intermediate lens is used as one having an action of shortening the optical path length (for example, to 17 mm) of the second optical path.

[3] Configuration of Biaxial Actuator The biaxial actuator 38 has a biaxial base 17 as shown in FIGS. 5 and 6, and the biaxial base 17 is connected to the optical system block 39. It is fixed and arranged above. The support shaft 2 is provided on the biaxial base 17.
Nine are planted. A pair of arc-shaped focusing yokes 18 and 19 and a pair of arc-shaped tracking yokes 20 and 21 are provided upright on the biaxial base 17 so as to surround the support shaft 29. A pair of focusing magnets 23, 24 are attached to the focusing yokes 18, 19, respectively. Each of the tracking yokes 20, 21 has a pair of tracking magnets 25, 26, 2 respectively.
7, 28 are attached.

A lens holder 30 is attached to the support shaft 29 so that the support shaft 29 can slide in the axial direction and rotate around the axis. That is, the lens holder 30 has a shaft insertion hole through which the support shaft 29 is inserted at a central portion, and the support shaft 29 is inserted through the shaft insertion hole and is supported by the support shaft 29. .

The first and second objective lenses 4 and 5 are mounted on the lens holder 30. These objective lenses 4 and 5 are mounted in parallel with the optical axis being parallel to the axis of the support shaft 29. The objective lenses 4 and 5 receive a laser beam from the biaxial base 17 side, and emit the laser beam to the opposite side of the biaxial base 17 (ie, toward the distal end of the support shaft 29). It is installed to be able to do.

A focusing coil 31 is attached to the lens holder 30 at a position corresponding to the focusing magnets 23 and 24. A pair of tracking coils 32 and 33 are attached to the lens holder 30 at positions corresponding to the respective tracking magnets 25, 26, 27 and 28.

When the focus driving current is supplied to the focusing coil 31, the focusing coil 31 receives an electromagnetic force from the magnetic field formed by the focusing magnets 23 and 24. 5, as indicated by the arrow F in the middle, the moving operation is performed in the focus direction parallel to the axis of the support shaft 29. The lens holder 30 is provided with the tracking coils 32, 3
When a tracking drive current is supplied to the tracking coil 3, the tracking coils 32 and 33 receive an electromagnetic force from the magnetic field formed by the tracking magnets 25, 26, 27 and 28, as shown by an arrow T in FIG. Then, it is rotated around the axis of the support shaft 29. At this time, the objective lenses 4 and 5 are moved in a tracking direction orthogonal to the optical axis.

Further, the lens bobbin 30 is provided with a pair of first neutral position holding iron pieces 35 and 37 which are symmetrical about the support shaft insertion hole and form a pair. These first iron pieces 35, 3 for holding a neutral position
7 is the tracking magnets 25, 26, 27,
When the lens bobbin 30 is located at a neutral point of a magnetic field formed by the lens 28, the lens bobbin 30 is moved to a first neutral position where the first objective lens 4 is a position where a light beam emitted from the collimator lens 3 is incident. It is held by the force of the magnetic field.
At this time, when a tracking drive current is supplied to each of the tracking coils 32 and 33, the lens bobbin 30 moves the first objective lens 4 in the tracking direction with the first neutral position as a center position. Move operation.

The lens bobbin 30 is provided with a pair of second neutral position holding iron pieces 34 and 36 which are symmetrical with respect to the support shaft insertion hole and form a pair. These second neutral position holding iron pieces 34, 36
Are the tracking magnets 25, 26, 27, 2
When the lens bobbin 30 is located at the neutral point of the magnetic field formed by the lens 8, the lens bobbin 30 is moved to the second neutral position where the second objective lens 5 is positioned to receive the light beam emitted from the collimator lens 3. It is held by the force of the magnetic field. At this time, when a tracking drive current is supplied to the tracking coils 32 and 33, the lens bobbin 3
0 is the second neutral position with the second neutral position as the center position.
Is moved in the tracking direction.

To switch between the first and second neutral positions, a current is supplied to the tracking coils 32 and 33 to rotate the lens bobbin 30 about the axis of the support shaft 29, When the bobbin 30 reaches a desired position (first or second neutral position), supply of current to each of the tracking coils 32 and 33 may be stopped.

The light beam emitted from the collimator lens 3 is incident on the support shaft 29 along the main surface of the biaxial base 17 through a through hole 22 provided in one of the tracking yokes 21. , The biaxial base 1
The light is reflected by the reflecting prism 42 attached to the main surface of the lens 7 and deflected by 90 °, and is incident on the first or second objective lens 4 or 5.

In the biaxial actuator 38, a through hole is provided in the biaxial base 17, and a light beam emitted from the collimator lens 3 is incident on the support shaft 29 through the through hole in parallel to the support shaft 29. It may be configured to be incident on the first or second objective lens 4, 5.

[4] Adjustment Method of Optical Pickup Apparatus In manufacturing this optical pickup apparatus, the above-described optical device and electronic device are built in the optical system block 39, and then the optical device and electronic device are connected to each other. It is necessary to adjust the relative position to be a predetermined relative position.

In this adjustment, first, the semiconductor laser 7 as the first light source is turned on, and the first laser beam emitted from the semiconductor laser 7 is incident on the first objective lens 4. I do. Then, in this state, the position of the biaxial actuator 38 with respect to the optical system block 39 is adjusted. In this adjustment, the objective lenses 4 and 5 are used.
Is adjusted in a plane (hereinafter, referred to as “XY plane”) orthogonal to the optical axis direction (hereinafter, referred to as “Z axis”).

Next, the semiconductor laser 7 is turned on, and while the first laser beam emitted from the semiconductor laser 7 is incident on the first objective lens 4, the two-axis actuator 38 The inclination with respect to the optical system block 39 (rotational positions around the X axis and the Y axis) is adjusted.

The adjustment of these two-axis actuators 38 is performed by observing a read signal (RF signal) while looking for an information signal from the first optical disc D1 and searching for a state where a good read signal can be obtained. Performed by

Then, the semiconductor laser chip 12 of the composite light-receiving / emitting device 1 as the second light source is turned on, and the light beam emitted from the composite light-receiving / emitting device 1 is incident on the second objective lens 5. And In this state, the position of the composite light receiving and emitting element 1 with respect to the optical system block 39 is adjusted. In this adjustment, the position of the second laser beam emitted from the light receiving / emitting composite element 1 in a plane (XY plane) orthogonal to the optical axis direction (Z axis) is adjusted. Here, if necessary, the position of the collimator lens 3 in the optical axis direction (Z-axis direction) is adjusted.

Next, the semiconductor laser 7 is turned on again, and the first laser beam emitted from the semiconductor laser 7 is made incident on the first objective lens 4 so that the light from the photodetector 9 is The position of the light beam incident on the detector 9 in a plane (XY plane) orthogonal to the optical axis is adjusted.
Then, the position of the intermediate lens 8 in the optical axis direction (Z-axis direction) is adjusted.

The adjustment of the light receiving / emitting composite element 1, the collimator lens 3, the photodetector 9, and the intermediate lens 8 is performed by reading the information signal from the first or second optical disk D1, D2. Signal (RF
Signal) while looking for a state in which a good read signal can be obtained.

[5] Configuration of Recording / Reproducing Apparatus In the recording / reproducing apparatus constructed using this optical pickup apparatus, the optical pickup apparatus is rotated by a spindle motor 45 as shown in FIG. The objective lenses 4 and 5 are arranged to face the signal recording surfaces of the optical discs D1 and D2. The optical pickup device 46 extends over the inner and outer peripheries of the optical discs D1 and D2.
The optical disk D is moved along a guide shaft (not shown) inserted through the shaft insertion hole of the optical disk D.
Information signals can be written and read over the entire signal recording surface of D1 and D2.

The drive shaft of the spindle motor 45 includes:
A substantially disk-shaped disk table 50 is mounted. The optical disks D1 and D2 are rotated by the spindle motor 45 while the center portion is held by the disk table 50.

From the optical pickup device 46, a read signal (RF signal) of an information signal from the first or second optical disk D1, D2 is output and sent to the signal demodulator 52. The signal demodulator 52 demodulates the read signal and sends it to the error correction circuit 53. The error correction circuit 53 sends out the error-corrected signal to an external computer (or audio circuit) via an interface (SCSI) 54.

The signal demodulator 52 and the error correction circuit 5
3 and the interface (SCSI) 54 operate under the control of the optical disk drive controller 49. The optical disk drive controller 49 controls the head access control circuit 47 according to a read signal sent from the signal demodulator 52 and a control signal sent from a RAM (random access memory) 51. The position of the optical pickup device 46 is controlled via 47.

Further, the optical disk drive controller 49 controls the focus and tracking servo circuit 48 on the basis of the focus error signal and the tracking error signal obtained from the read signal, and through the focus and tracking servo circuit 48, The focus servo operation and the tracking servo operation of the biaxial actuator 38 are controlled. By performing such a focus servo operation and a tracking servo operation, the first or the second
The objective lenses 4 and 5 always have the first or second objective lens.
The first or second laser beam is focused on a portion (recording track) where an information signal is recorded on the signal recording surfaces of the optical discs D1 and D2. The optical disk drive controller 49 controls the rotation speed of the spindle motor 45 based on a clock signal obtained from the read signal.

When the first optical disk D1 is mounted on the disk table 50, the semiconductor laser 7, which is the first light source, is turned on.
It is assumed that the first laser beam emitted from the first objective lens 4 is incident on the first objective lens 4.

In this case, the first optical disc D1
The recording and reproduction conditions of the information signal for the first objective lens 4 are 0.6, and the wavelength of the first laser beam is 635 nm (630 nm to 650 n).
m) is satisfied, and all signals (3T to 11T) recorded on the first optical disc D1 are satisfied.
(T is a channel bit), a sufficient spatial frequency characteristic (Modulation transfer function; MTF) is obtained. In addition, the intermediate lens 8 ensures that the semiconductor laser 7 fills the collimator lens 3 with a favorable fill condition. Therefore, good recording and reproduction on the first optical disc D1 are possible.

If the second optical disk D2 is mounted on the disk table 50, the second
The semiconductor laser chip 12 of the composite light-receiving / emitting element 1 as the light source is turned on, so that the second laser beam emitted from the semiconductor laser chip 12 is incident on the second objective lens 5.

In this case, the second optical disk D2
, The condition that the numerical aperture of the second objective lens 4 is 0.45 and the wavelength of the second laser beam is 780 nm. For all signals (3T to 11T (T is a channel bit)) recorded in D2, sufficient spatial frequency characteristics (Modulation transfer
function; MTF), and good recording and reproduction are possible.

[6] Configuration without Collimator Lens (Finite Objective Lens) In the optical pickup device according to the present invention, as shown in FIG.
The objective lens 4 is designed to correspond to the wavelength (630 nm to 650 nm and 780 nm).
And the second optical discs D1 and D2 may be used.

In this case, the first optical disk D1
The semiconductor laser 7 is turned on when writing or reading an information signal with respect to. The first laser beam emitted from the semiconductor laser 7 passes through the intermediate lens 8, the beam splitter 6, and the multiplexing prism 2, and is incident on the objective lens 4. On the signal recording surface of the optical disc D1. When writing or reading an information signal to or from the second optical disc D2, the semiconductor laser chip 12
Lights up. The first laser beam emitted from the semiconductor laser chip 12 passes through the multiplexing prism 2 and is incident on the objective lens 4.
The light is focused on the signal recording surface of the second optical disc D2.

Even when such a finite objective lens 4 is used commonly for the first and second optical discs D1 and D2, the provision of the intermediate lens 8 allows the objective laser 4 of the semiconductor laser 7 to be used. The fill condition for the lens 4 is in a good state.

[0102]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical system from the semiconductor laser 7 and the composite light-receiving / emitting element 1 to the objective lenses 4 and 5, which are essential parts of the optical pickup device according to the present invention, was specifically designed.

That is, the focal length of the collimator lens 3 is 17 mm, the diameter of the entrance pupil is 4.5 mm, and the numerical aperture of the first objective lens 4 is 0.1 mm, as shown in Table 1 above. 6, the focal length is 3 mm, the numerical aperture of the second objective lens 5 is 0.45, the focal length is 4.5 mm, the emission output (maximum) of the semiconductor laser 7 is 3.5 mW, and the divergence angle of the emitted luminous flux is The radial direction (rad) of the first optical disc D1 is set to 33 ° (deg) and the tangential direction (tan) is set to 8 ° (deg), and the emission output (maximum) of the semiconductor laser chip 12 of the light receiving / emitting composite element 1 is set. To 4.
5 mW, the divergence angle of the emitted light beam
When the radial direction (rad) is set to 12 ° (deg) and the tangential direction (tan) is set to 24 ° (deg), the shape of the intermediate lens 8 shown in Table 2 below is optimal.

[0104]

[Table 2]

The intermediate lens 8 is connected to the semiconductor laser 7
Even when the position moves within the specified tolerance on the XY plane, the reading performance of the information signal from the first optical disc D1 is not deteriorated. That is, by optimizing the surface shapes of the surface 1 (aspheric surface) and the surface 2 (aspheric surface) of the intermediate lens 8, even if the position of the semiconductor laser 7 moves on the XY plane, the collimator lens 3 is moved. The transmitted first laser beam is configured so that the wavefront aberration does not increase even though the optical axis may be inclined.

[0106]

As described above, the optical pickup device according to the present invention comprises the first light source and the second optical path constituting the first optical path for the first optical recording medium which emits light beams having different wavelengths. A second light source constituting a second optical path for a recording medium, a collimator lens into which a light beam emitted from the first light source and a light beam emitted from the second light source are incident, or the first light source. An objective lens into which a light beam emitted from the light source and a light beam emitted from the second light source are incident, and one of the first and second light sources and the collimator lens or the objective lens. An intermediate lens disposed on an optical path therebetween, the intermediate lens changing an optical path length between one of the first and second light sources and the collimator lens or the objective lens. Lens.

Therefore, in this optical pickup device, the focal length of the collimator lens or the objective lens commonly used in the first and second optical paths and the characteristics of the respective light sources (emission output and divergence angle of the emitted light flux) ) Can be made different for each optical path by the intermediate lens.

That is, the present invention satisfies the optimum fill conditions for a plurality of types of optical recording media having different transparent substrate thicknesses and information signal recording densities.
The light intensity of the light beam irradiated on the signal recording surface of the optical recording medium and the focused spot diameter of the light beam formed on the signal recording surface are required and sufficient, so that recording and reproduction of information signals can be performed. It is possible to provide an optical pickup device that can be favorably performed.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of an optical pickup device according to the present invention, with a part thereof cut away.

FIG. 2 is a side view, partially cut away, showing another example of the configuration of the optical pickup device according to the present invention.

FIG. 3 is a side view, partially broken away, showing a configuration of a composite light receiving and emitting element constituting the optical pickup device.

FIG. 4 is a longitudinal sectional view showing a shape of an intermediate lens constituting the optical pickup device.

FIG. 5 is an exploded perspective view illustrating a configuration of a biaxial actuator included in the optical pickup device.

FIG. 6 is a perspective plan view showing a configuration of the biaxial actuator.

FIG. 7 is a graph showing a relationship between an optical path length from a light source to an entrance pupil of a collimator lens and an amount of light incident on the entrance pupil in an optical path for a first optical disc.

FIG. 8 is a graph showing the relationship between the optical path length from the light source to the entrance pupil of the collimator lens in the optical path for the first optical disk and the amount of light (board surface power) irradiated onto the first optical disk.

FIG. 9 is a graph showing the relationship between the optical path length from the light source to the entrance pupil of the collimator lens in the optical path for the second optical disc and the amount of light incident on the entrance pupil.

FIG. 10 is a graph showing a relationship between an optical path length from a light source to an entrance pupil of a collimator lens in an optical path for a second optical disc and a light amount (panel power) irradiated on the second optical disc.

FIG. 11 is a graph showing the relationship between the optical path length from the light source to the entrance pupil of the collimator lens in the optical path for the second optical disc and the shape (by logarithmic scale) of the light spot formed on the second optical disc. is there.

FIG. 12 is a graph showing a relationship between an optical path length from a light source to an entrance pupil of a collimator lens in an optical path for a second optical disc and a shape of a light spot formed on the second optical disc.

FIG. 13 is a block diagram showing a configuration of a recording / reproducing apparatus using the optical pickup device.

FIG. 14 is a side view showing a configuration of a conventional optical pickup device with a part thereof cut away.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 light receiving / emitting composite element, 2 multiplexing prism, 3 collimator lens, 4 first objective lens, 5 second objective lens, 6 beam splitter, 7 semiconductor laser, 8 intermediate lens, 9 photodetector

[Procedure amendment]

[Submission date] April 8, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction contents]

For example, as shown in Table 1 above,
3. The emission output (maximum) of the semiconductor laser chip 12 is 4.
5 mW, the divergence angle of the emitted light beam is the second optical disc D2
12 ° (deg) in the radial direction (rad) and 24 ° (deg) in the tangential direction (tan),
The diameter of the entrance pupil of the collimator lens 3 is set as described in [Table 1].
Assuming that the light intensity is 4 mm and that the light intensity (board power) of the second laser light beam irradiated onto the signal recording surface of the second optical disk D2 is 0.3 mW or more, FIG. As shown in FIG. 10, the optical path length from the semiconductor laser chip 12 to the entrance pupil of the collimator lens 3 needs to be 19 mm or less.
17 mm.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction contents]

For example, as shown in Table 1 above,
The emission output (maximum) of the semiconductor laser 7 is 3.5 mW,
The divergence angle of the emitted light beam is 33 ° (deg) in the radial direction (rad) and 8 ° (deg) in the tangential direction (tan) of the first optical disc D1, and the diameter of the entrance pupil of the collimator lens 3 is According to [Table 1], 3.
Assuming that the light intensity is 6 mm and the light intensity (board power) of the first laser light flux irradiated onto the signal recording surface of the first optical disk D1 is 0.2 mW or more, FIG. As shown in FIG. 8, the optical path length from the semiconductor laser 7 to the entrance pupil of the collimator lens 3 is 28
mm or less, for example, 25 mm. And in this optical pickup device,
Since the optical path length of the first optical path from the semiconductor laser 7 to the collimator lens 3 is made as long as possible within a range where a sufficient board surface power can be secured, the light intensity at the center of the entrance pupil of the collimator lens 3 is reduced. The ratio of the light intensity at the outermost periphery of the entrance pupil is increased, and as shown by (EFL 25 mm) in FIG. 11 and FIG.
The condensed spot after passing through the objective lens 4 is smaller than the case where the intermediate lens 8 is not provided (indicated by EFL 17 mm in FIGS. 11 and 12).

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0071

[Correction method] Change

[Correction contents]

In this optical pickup device, when the tracking error signal is detected for the first optical disk D1 by the so-called three-beam method, the beam splitter 6 is used by the semiconductor laser 7.
A grating (diffraction grating) is provided on the optical path leading to.
Also, in this optical pickup device, when detecting a focus error signal by the so-called astigmatism method for the first optical disc D1, the detection is performed by the photodetector 9 by passing through the beam splitter 6. It can be carried out.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0103

[Correction method] Change

[Correction contents]

That is, the focal length of the collimator lens 3 is set to 17 mm, and as shown in Table 1 above,
The numerical aperture of the first objective lens 4 is 0.6 and the focal length is 3 m
m, the numerical aperture of the second objective lens 5 is 0.45, the focal length is 4.5 mm, the emission output (maximum) of the semiconductor laser 7 is 3.5 mW, and the divergence angle of the emitted light beam is the first optical disc. 33 ° in the radial direction (rad) of D1 (de)
g), 8 ° in tangential direction (tan) (de)
g), the emission output (maximum) of the semiconductor laser chip 12 of the combined light receiving and emitting element 1 is 4.5 mW, and the divergence angle of the emitted light beam is the radial direction (rad) of the second optical disc D2.
About 12 ° (deg), tangential direction (tan)
Is set to 24 ° (deg), the intermediate lens 8
The shape shown in the following [Table 2] is optimal. The diameter of the entrance pupil is determined by the numerical aperture of the objective lens and the focal length of the objective lens.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Michiko Yamazaki Inventor, Sony Corporation 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo

Claims (2)

[Claims] A first light source and a second light source that emit light beams having wavelengths different from each other; a collimator lens that receives a light beam emitted from the first light source and a light beam emitted from the second light source; A first objective lens corresponding to a first optical recording medium to which a light beam from the first light source passing through the collimator lens is incident, and a light beam from the second light source passing through the collimator lens is incident. A second objective lens corresponding to a second optical recording medium, and an intermediate lens disposed on an optical path between one of the first and second light sources and the collimator lens. An optical pickup device, wherein the intermediate lens is a lens that changes an optical path length between the first or second light source and the collimator lens. A first light source and a second light source that emit light beams having wavelengths different from each other; an objective lens that receives a light beam emitted from the first light source and a light beam emitted from the second light source; An intermediate lens disposed on an optical path between any one of the first and second light sources and the objective lens, wherein the intermediate lens includes the first or second light source and the intermediate light source; An optical pickup device, which is a lens that changes an optical path length between the objective lens and the objective lens.