JP2001344801A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup in which good spot quality of both wavelengths can be obtain, and thinning and miniaturization can be realized even when a beam shaping prism is used in an optical system made an objective lens two-wavelength sharing using two light sources of different wavelengths. SOLUTION: In the optical system which made the objective lens 8 the two- wavelength sharing using a first module 1 at a side of a DVD, and a second module 13 for a CD with which the wavelengths differ, the CD side also obtains a good spot by providing with an AS correction prism 3 being an astigmatic correction means in an optical path only at the CD side to correct astigmatism which is generated when divergent light at the CD side passes to the beam shaping prism 6 used for the beam shaping at the DVD side. While the good spot is thereby obtained also for the DVD side and the CD side, the miniaturization and the thin shape of the optical pickup can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical pickup for optically recording information on an optical disk and / or optically reproducing information recorded on the optical disk.

[0002]

2. Description of the Related Art Hitherto, it has been desired to reduce the size of an optical disk device for recording or reproducing information using laser light, and attempts have been made to reduce the size and weight of an optical pickup. As a typical example, there is an optical disk device that records information on a disk and reproduces information recorded on the disk using a semiconductor laser. In these apparatuses, in order to increase the light use efficiency and obtain a light spot having an axially symmetric intensity distribution, it is necessary to make the isointensity line shape (hereinafter, referred to as a beam shape) of the light beam circular.

In general, the light emitted from a semiconductor laser is PN
Because the divergence angle differs between the horizontal and vertical directions of the joint surface,
When a parallel light beam is formed by using a collimating lens, the beam shape becomes elliptical. For this reason, an optical system for making the elliptical light beam circular has been conventionally proposed.

[0004] Alternatively, even if it is not necessary to enhance the light use efficiency and it is not necessary to shape the elliptical light beam into a circular shape, astigmatism occurs from the laser light source and each optical component,
The quality of the beam spot obtained by the laser light source may be degraded. Therefore, a beam shaping prism having a slight beam shaping effect is inserted into the optical system, and by slightly changing the parallelism of the light beam passing through the beam shaping prism, astigmatism for the correction is generated and the spot quality is improved. Techniques for making adjustments to improve have also been proposed.

[0005] Further, as in a digital versatile disk (DVD), in order to increase the recording density, the wavelength of a light source used is shortened, the optical resolution is improved, and the frequency band in which recording or reproduction can be performed is expanded. Can be used, but the operating wavelength of a compact disc (CD) is 780 nm.
When a conventional optical disc set to a wavelength of about 830 nm is reproduced with a shorter wavelength semiconductor laser, there arises a problem that a sufficient reproduction signal or control signal cannot be obtained due to a difference in reflectance or absorptance of a recording surface. . This is remarkably observed in, for example, a CD-R standardized as a writable CD and having a highly wavelength-dependent reflective film.

In order to solve the above two problems,
A method using two light sources as shown in FIGS. 15 and 16 and adding a beam shaping function has been considered.

FIGS. 15 and 16 are diagrams showing the structure of a conventional optical pickup using this method. FIG. 15 shows a case where a high-density optical disk 44 having a base material thickness of 0.6 mm is reproduced. This shows a case where an optical disk 50 having a base material thickness of 1.2 mm is reproduced.

In FIG. 15, a light beam 37 having a wavelength of 650 nm emitted from a semiconductor laser 60a of a first module 60 passes through a hologram 60c and a condenser lens 38.
The light becomes parallel light of an ellipse. Note that the first module 6
In the case of 0, the direction of the first module 60 is set so that the major axis direction of the ellipse of the beam pattern coincides with the thickness direction of the optical disk device. Here, since the configuration diagram of each optical pick is represented in two dimensions, the total reflection mirror 4 is actually used.
In FIG. 1, the direction in which the light beam is decentered is a direction perpendicular to the plane of the paper, but in the figure, it is represented by a figure when it is rotated by 90 ° about the optical axis on the A plane. Subsequent figures are similarly expressed.

The elliptical parallel light is beam-shaped by a beam shaping prism 39 to form a circular beam. After passing through a composite prism 40, the optical path is bent in a vertical direction by a total reflection mirror 41, and an aperture limiting means 42 is provided. Through the objective lens 43 and onto the surface of the optical disc 44,
Irradiation is performed as a minute light spot 45. The aperture limiting means 42 transmits all light having a wavelength of 650 nm,
The 80 nm light is configured to be transmitted only through the inner periphery corresponding to a numerical aperture of 0.45, and the objective lens 43 has a numerical aperture of 0.4.
In 6, the optical disk 44 is optimally designed with a substrate thickness of 0.6 mm. Therefore, the light beam 37 having a wavelength of 650 nm is used.
Is reduced with a numerical aperture of 0.6.

Next, the light beam 4 reflected by the optical disk 44
6 passes through the objective lens 43 again, the optical path is bent in the horizontal direction by the mirror 41, passes through the composite prism 40, and then enters the beam shaping prism 39 again.

Since the optical path in the beam shaping prism 39 is in the opposite direction to the above-mentioned optical path, the circular reflected light is reduced in the thickness direction of the optical pickup by the beam shaping prism 39 to become an elliptical beam.

The reflected light converted into an elliptical beam is converged by the condenser lens 38 and enters the first module 60. The light beam 46 incident on the first module 60 is diffracted by the hologram 60c and is incident on the photodetector 60b, so-called SSD (spot size detection).
It is configured to detect a focus control signal for causing the objective lens 43 to follow a recording surface by using a method and a tracking control signal for causing a track on a track surface to follow by using a phase difference method.

Further, as shown in FIG. 16, the second module 47 has a semiconductor laser 47a having a wavelength of 780 nm. Wavelength 780 emitted from the second module 47
The light beam 49 of nm passes through the hologram 47c and enters the composite prism 40. The light beam 49 condensed by the condenser lens 48 and slightly diverged enters the composite prism 40 and is reflected by the optical film 40a. Further, the light beam 49 reflected by the total reflection mirror 41 is transmitted through only the inner peripheral portion corresponding to the numerical aperture of 0.45 by the aperture limiting means 42 and is incident on the objective lens 43, and is reflected on the recording surface of the optical disk 50. A spot 51 is formed. By limiting the aperture only in the case of the wavelength of 780 nm, the numerical aperture becomes 0.45, so that the optical disc 50 such as a CD having a substrate thickness of 1.2 mm can be handled.

The light beam 52 reflected by the optical disk 50
Again passes through the objective lens 43 and the aperture limiting means 42,
The optical path is bent in the horizontal direction by the total reflection mirror 41 and enters the composite prism 40. Most of the incident light beam is reflected by the optical film 40 a, converged by the condenser lens 48, and enters the second module 47. Second module 47
Is incident on the photodetector 47b after being diffracted by the hologram 47c, and a focus control signal for causing the objective lens 43 to follow the recording surface by using the SSD method, and by using a push-pull method. It is configured to detect a tracking control signal for following a track on a track surface. In general, a tracking control signal for a CD often uses a three-beam method, but in this conventional example, a push-pull method is used to simplify the description.

By using the above optical system,
When reproducing a high-density optical disk 44 corresponding to a wavelength of 650 nm, a reproduction signal and a control signal are obtained by turning on the semiconductor laser 60a, focusing on the optical disk 44, and receiving the reflected light with the photodetector 60b. When reproducing the optical disk 50 corresponding to the wavelength of 780 nm, the semiconductor laser 47a is turned on and the optical disk 50 is turned on.
By focusing on 0 and receiving the reflected light with the photodetector 47b, a reproduction signal and a control signal can be obtained, and the optical disks 44 and 50 having different thicknesses and corresponding wavelengths are recorded and reproduced, respectively.

[0016]

In the above-mentioned prior art, the beam shaping prism 39 is inserted between the first module 60 and the composite prism 40, so that the optical path length of the entire optical system becomes longer and the optical pickup becomes longer. It is difficult to reduce the size and thickness of the device.

When a beam shaping means is added to the total reflection mirror 41 or the composite prism 40 for miniaturization, the light beam 49 emitted from the second module 47 is parallelized when passing through the beam shaping means. Since it is not light, there is a problem that astigmatism occurs and a good spot cannot be obtained.

The present invention can converge a light beam on an optical disk with a good light spot even if it has a beam shaping function for an optical pickup having a plurality of light emitting sources, and is small and inexpensive. An object is to provide an optical pickup that can be manufactured.

[0019]

In order to solve the above-mentioned problems, a first invention (corresponding to claim 1) includes a first light source for emitting a first light, and a first light source from the first light source. A substantially planar reflecting means for reflecting the first light, a condensing means for condensing the first light reflected by the reflecting means, and the first light condensed by the condensing means Beam shaping means for shaping the beam, converging means for converging the first light beam-shaped by the beam shaping means on a first optical disk corresponding to the first light, and emitting second light. A second light source; and astigmatism imparting means for imparting a predetermined astigmatism to the second light from the second light source, wherein the reflecting means passes the second light. Has a function of causing the light emitted by the second light source to pass through the reflecting means. , The light converging means and the beam shaping means being arranged at a position facing the light converging means, and the converging means converging the second light from the second light source on a second optical disk corresponding to the second light. The astigmatism imparting means is disposed between the second light source and the reflecting means, and has an incident surface and an emitting surface for light, and the emitting surface and the reflecting means are substantially In an upper parallel relationship, the relationship between the position of the second light source with respect to the reflecting means and the position of the incident surface of the astigmatism imparting means is the second.
Is in a positional relationship in which astigmatism for reducing astigmatism generated when the light passes through the beam shaping means is given to the second light after passing through the astigmatism giving means. An optical pickup characterized by the following.

According to a second aspect of the present invention (corresponding to claim 2), the reflecting means is in contact with the emission surface of the astigmatism imparting means, and the reflecting means and the astigmatism imparting means are integrated. An optical pickup according to the first aspect of the present invention, wherein

A third aspect of the present invention (corresponding to claim 3) further includes an optical element disposed between the second light source and the astigmatism imparting means, and further comprises an optical element arranged between the second light source and the astigmatism imparting means. The relationship between the position of the light source and the position of the incident surface of the astigmatism imparting unit is based on the astigmatism of the second light based on the second light source and / or the astigmatism based on the optical element. A first or second positional relationship in which astigmatism for reducing astigmatism of the second light is also given to the second light after passing through the astigmatism imparting means. 2 is an optical pickup according to the present invention.

According to a fourth aspect of the present invention (corresponding to claim 4), the first aspect
A first light source that emits light, a light condensing unit that condenses the first light from the first light source, and a function of beam shaping the first light that is condensed by the light condensing unit And a beam shaping means having a reflection surface for reflecting the first light, and the first light beam shaped and reflected by the beam shaping means is converted to a first light beam corresponding to the first light beam. Converging means for converging on the first optical disc, a second light source for emitting second light, and astigmatism imparting means for imparting predetermined astigmatism to the second light from the second light source And the reflection surface of the beam shaping means has a function of passing the second light,
The second light source is disposed at a position where the light emitted by the second light source passes through the beam shaping unit and is directed to the converging unit, and the converging unit transmits the second light from the second light source,
Converging on a second optical disk corresponding to the second light,
The astigmatism imparting unit is disposed between the second light source and the beam shaping unit, and has an incident surface and an exit surface of light, and the exit surface and the reflection of the beam shaping unit. A substantially parallel relationship with the surface, the position of the second light source with respect to the reflecting surface of the beam shaping means,
The relationship between the position of the entrance surface of the astigmatism imparting means,
A positional relationship in which astigmatism for reducing astigmatism generated when the second light passes through the beam shaping means is given to the second light after passing through the astigmatism giving means. An optical pickup characterized in that:

According to a fifth aspect of the present invention (corresponding to claim 5), the reflection surface of the beam shaping means and the emission surface of the astigmatism imparting means are in contact with each other, and the beam shaping means and the astigmatism are provided. An optical pickup according to a fourth aspect of the present invention, wherein the aberration providing means is integrated.

A sixth aspect of the present invention (corresponding to claim 6) further comprises an optical element disposed between the second light source and the astigmatism imparting means, wherein the reflection surface of the beam shaping means is provided. The relationship between the position of the second light source and the position of the incident surface of the astigmatism imparting means is astigmatism of the second light based on the second light source, and / or Wherein the positional relationship is such that astigmatism for reducing astigmatism of the second light based on the optical element is also given to the second light after passing through the astigmatism imparting means. An optical pickup according to the fourth or fifth aspect of the present invention.

According to a seventh aspect of the present invention (corresponding to claim 7), the first aspect
A first light source that emits light, a light condensing unit that condenses the first light from the first light source, and a beam shaping of the first light that is condensed by the light condensing unit. Beam shaping means for passing the first light, and beam shaping by the beam shaping means, the first light having passed the beam shaping means being converted into a first beam corresponding to the first light. Converging means for converging on an optical disc, a second light source for emitting second light, and a second light source provided on the emission surface of the first light of the beam shaping means. Reflecting means for reflecting light and passing the first light, wherein the converging means converts the second light from the second light source into a second light corresponding to the second light. An optical pickup characterized by being converged on an optical disc. .

According to an eighth aspect of the present invention (corresponding to claim 8), the first aspect
A first light source that emits light, a light condensing unit that condenses the first light from the first light source, and a beam shaping of the first light that is condensed by the light condensing unit. Beam shaping means for reflecting the first light, and convergence for converging the first light, which has been beam-shaped and reflected by the beam shaping means, to a first optical disk corresponding to the first light. Means, a second light source for emitting a second light, and an input / output surface of the first light of the beam shaping means, which reflects the second light from the second light source. And a reflecting means for transmitting the first light, wherein the converging means converges the second light from the second light source onto a second optical disk corresponding to the second light. An optical pickup characterized in that:

According to a ninth aspect of the present invention (corresponding to claim 9), the wavelength of the first light emitted from the first light source is different from the wavelength of the second light emitted from the second light source. An optical pickup according to any one of the first to eighth aspects of the present invention.

A tenth aspect of the present invention (corresponding to claim 10) is:
The beam shaping unit is configured to control the first light source from the first light source.
The optical pickup according to any one of the first to ninth aspects, wherein the optical pickup also has a function of correcting chromatic aberration of the light.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(First Embodiment) FIGS. 1 and 2 are configuration diagrams showing the configuration of an optical pickup according to a first embodiment of the present invention. FIG. When reproducing a high-density optical disk 9 of .6 mm, FIG.
Indicates a case where an optical disk 15 having a base material thickness of 1.2 mm is reproduced. Here, since the configuration diagram of each optical pick is represented two-dimensionally, the direction in which the light beam is decentered by the beam shaping prism 6 is actually a direction perpendicular to the plane of the paper, but in FIG. Is rotated by 90 °. Subsequent figures are similarly expressed.

In FIG. 1, a first module 1 for reproducing a DVD includes a semiconductor laser 1a having a wavelength of 650 nm, a hologram 1c for dispersing reflected light from an optical disk 9 to give a spatial change, and receiving the reflected light. The photodetector 1b is integrally formed, and the positions of the photodetector 1b and the hologram 1c are adjusted before assembling the module. In this embodiment, the hologram is used as the element for separating the reflected light from the optical disk. However, the same effect may be obtained by another optical component such as a prism.

The optical film 4 shown in FIG. 1 is composed of a multilayer film that totally reflects light near a wavelength of 650 nm and transmits light near a wavelength of 780 nm.

The light beam 2 enters the AS correction prism 3 at an angle of θ 1 and is reflected by the optical film 4. Then, the light beam 11 becomes parallel or substantially parallel by the condenser lens 5 and enters the beam shaping prism 6. The second surface of the beam shaping prism 6 is a total reflection film 6a. The beam shaping prism 6 is an optical element in which the first surface and the second surface have an angle of α1, as shown in FIG. That is,
This is an optical element in which the first surface and the second surface are in a non-parallel relationship.

The parallelism of the light beam 11 is changed by moving the condenser lens 5 in the direction of the "condenser lens movement direction" shown in FIG. If the focal length of the objective lens 8 is 3.0 mm, NA = 0.6, and the focal length of the condenser lens 5 is 20.0 mm, the radial direction and the tangent of the spot on the disk as shown in the graph of FIG. Fluctuation of the astigmatism in the axial direction (fluctuation of the astigmatism in the horizontal and vertical directions of the PN junction surface of the laser). Due to this aberration variation, astigmatism of each optical element with respect to the semiconductor laser 1a can be corrected.

Next, the light beam 11 transmitted and reflected by the beam shaping prism 6 enters the aperture limiting means 7. As shown in FIG. 4, the aperture limiting means 7 has an optical multilayer film having different characteristics at an inner peripheral portion and an outer peripheral portion, and has a first optical multilayer film 7a at an inner peripheral portion and a second optical multilayer film at an outer peripheral portion. Optical multilayer film 7
b are provided, each having a different thickness and number of layers.

The first optical multilayer film 7a transmits both light having a wavelength of 650 nm and 780 nm, and the second optical multilayer film 7b transmits light having a wavelength of 650 nm and reflects light having a wavelength of 780 nm. . Further, a complete shielding film 7c is provided on the outside, and blocks any wavelength. Therefore, the wavelength 65
The light beam 11 of 0 nm can pass through the aperture limiting means 7 with almost no optical loss in both the optical multilayer film 7a and the optical multilayer film 7b. The numerical aperture of the complete shielding film 7c is 0.6 to correspond to a high density optical disc such as a DVD.
It has become.

The light beam 11 transmitted through the aperture limiting means 7 and incident on the objective lens 8 is stopped down at a numerical aperture of 0.6 to form a light spot 10 on the recording surface of the optical disk 9 having a substrate thickness of 0.6 mm. . Next, the light beam 12 reflected by the optical disk 9 passes through the objective lens 8 and the aperture limiting means 7 again and enters the beam shaping prism 6. After the beam is shaped again by the beam shaping prism 6, the beam is narrowed by the condenser lens 5 and enters the AS correction prism 3.

The light beam 12 having a wavelength of 650 nm is
The light is reflected by the optical film 4 formed on the correction prism 3 and enters the first module 1. The light beam 12 incident on the first module 1 is diffracted by the hologram 1c and is incident on the photodetector 1b, so-called SSD (spot size).
A focus control signal for causing the objective lens 8 to follow the recording surface using a detection method and a tracking control signal for causing the objective lens 8 to follow a track on the track surface using a phase difference method are detected.

The second module 13 for reproducing a CD includes a semiconductor laser 13 a having a wavelength of 780 nm and an optical disk 15.
Hologram 1 that separates reflected light from light and gives spatial change
3c and a photodetector 13b for receiving the reflected light are integrally formed, and the first module 1 for DVD reproduction is
Is similar to

In the case of reproducing a CD, since the substrate thickness of the optical disk 15 is 1.2 mm, when the light beam 14 after passing through the condenser lens 5 is incident on the objective lens 8 as parallel light, The light spot 16 has a very large spherical aberration, and the spot quality deteriorates. Therefore, the light beam 14 after passing through the condenser lens 5 is made to be slightly divergent light and is incident on the objective lens 8 so that
The spherical aberration of the light spot can be corrected.

However, by transmitting the diverging light through the beam shaping prism 6, the astigmatism becomes very large, and the spot quality deteriorates. Therefore, as a light combining means of the light beam 2 emitted from the first module 1 and the light beam 14 emitted from the second module 13, as shown in FIG.
AS correction prism 3 whose first and second surfaces have an angle of α2
Is used to generate astigmatism of an inverse component, eliminate astigmatism on a light spot, and obtain good spot quality.

In FIG. 2, the light beam 14 having a wavelength of 780 nm emitted from the second module 13 is
c, and enters the AS correction prism 3 at an angle of θ2. Astigmatism is added by transmitting the light through the AS correction prism 3, and then converted into a slightly divergent light by the condenser lens 5. The light beam 14 generates astigmatism when passing through the beam shaping prism 6, but is canceled out by the astigmatism added by the AS correction prism 3 to become a light beam having almost no aberration.

The numerical aperture is controlled by the numerical aperture limiting means 7.
Only the inner peripheral portion corresponding to 45 passes through and enters the objective lens 8 to form a light spot 16 on the recording surface of the optical disk 15. Since the light beam 14 is incident on the objective lens 8 in a divergent system and the aperture is limited, a light spot 16 having almost no aberration can be obtained even on an optical disk 15 having a base material thickness of 1.2 mm such as a CD. .

Light beam 17 reflected by optical disk 15
Passes through the objective lens 8, the aperture limiting means 7, and the beam shaping prism 6 again, is converged by the condenser lens 5, and enters the AS correction prism 3. The light beam 17 having a wavelength of 780 nm is A
The light passes through the S-correction prism 3 and enters the second module 13. The light beam 17 is diffracted by the hologram 13c and is incident on the photodetector 13b. A focus control signal for causing the objective lens 8 to follow the recording surface using the SSD method, and a track control signal using the push-pull method. It is configured to detect a tracking control signal for following a track on a surface.

In this embodiment, as in the conventional example, the push-pull method is used for the sake of simplicity, but a three-beam method that is generally used may be used.

In the optical pickup according to the present embodiment, the objective lens 8 designed to have a wavelength of 650 nm, a disk base material thickness of 0.6 mm and a numerical aperture of 0.6 is used. 3mm, 20mm each
And the angle α between the first surface and the second surface of the beam shaping prism 6
1 is set to 1.15 °, and the optical system is set such that the angle α2 between the first surface and the second surface of the AS correction prism 3 is 2.13 °.

Further, by setting the distance of the condensing lens 5 from the semiconductor laser 13a to be about 6 mm shorter than the point at which the beam passing through the condensing lens 5 becomes parallel light, the light having a wavelength of 650 nm is calculated. The beam was converged on the optical disk 9 having a substrate thickness of 0.6 mm and the light beam having a wavelength of 780 nm was converged on the optical disk 15 having a substrate thickness of 1.2 mm with a wavefront aberration of 10 mλ or less.

As described above, according to the present embodiment, the prism that combines and separates the divergent light for CD and the divergent light for DVD is used as the astigmatism generated when the divergent light for CD passes through the beam shaping prism 6. By designing so as to generate astigmatism that cancels the difference, a good light spot can be obtained for both the CD light spot and the DVD light spot. Further, the beam shaping prism 6 is arranged on a common optical path,
The optical pickup can be reduced in size and thickness.

The AS correction prism 3 can make the first surface and the second surface of the AS correction prism 3 parallel by appropriately adjusting the incident angle θ2 of the light beam emitted from the second module 13. In this case, since the AS correction prism 3 is a flat plate, the entire optical system can be configured at a lower cost.

In short, the relationship between the position of the semiconductor laser 13 a with respect to the optical film 4 and the position of the surface of the AS correction prism 3 that faces the optical film 4 is that the light beam 14 from the semiconductor laser 13 a As long as astigmatism for reducing astigmatism that occurs during the passage of the light beam 14 after passing through the AS correction prism 3 is in a positional relationship, the optical film 4 of the AS correction prism 3 can be used.
And the position of the surface facing the optical film 4 may be parallel or non-parallel.

Further, in order to prevent the light beam from being blurred due to the fluctuation of the wavelength of the laser light source, even if the beam shaping prism 6 is made of a plurality of glass materials as shown in FIG. Needless to say, the same effect as in the embodiment is obtained.

The AS correction prism 3 is a semiconductor laser 13a or an AS correction prism 3 from the semiconductor laser 13a.
By correcting also the astigmatism of the optical component existing between the optical paths up to the above, a better spot can be obtained.
Note that a condenser lens corresponds to an example of the optical component.

Further, in the above-described first embodiment,
Although the optical film 4 is provided on one surface of the AS correction prism 3, the optical film 4 is not limited to the one provided on the surface of the AS correction prism 3.

(Second Embodiment) Next, a second embodiment will be described. The description of the same parts and operations as in the first embodiment will be omitted.

FIGS. 6 and 7 are configuration diagrams showing the configuration of the optical pickup according to the second embodiment of the present invention.
FIG. 7 shows a case where the high-density optical disk 9 having a substrate thickness of 0.6 mm is reproduced in this embodiment, and FIG. 7 shows a case where the optical disk 15 having a substrate thickness of 1.2 mm is reproduced.

In FIG. 6, a first module 1 for reproducing a DVD has a semiconductor laser 1a having a wavelength of 650 nm, a hologram 1c for dispersing the reflected light from the optical disk 9 to give a spatial change, and receives the reflected light. The photodetector 1b is integrally formed, and the positions of the photodetector 1b and the hologram 1c are adjusted before assembling the module. In this embodiment, the hologram is used as the element for separating the reflected light from the optical disk. However, the same effect may be obtained by an optical component such as a prism.

The light beam 18 is converted into a parallel or substantially parallel light beam by the condenser lens 19,
1 at an angle of θ3. The composite prism 21 is composed of a beam shaping prism 21a and an AS correction prism 21b, each of which is laminated with an optical film 21c.
As shown in FIG. 6, the angle of the first surface and the second surface of the beam shaping prism 21a is α3, and the angle of the AS correction prism 21b is one.
The angle between the surface and the second surface is α4.

The optical film 21c is formed of a multilayer film that totally reflects light near 650 nm and transmits light near 780 nm. Therefore, the light beam 18 is transmitted / reflected only through the beam shaping prism 21a and shaped. Thereafter, the optical path is bent by the total reflection mirror 22 and enters the aperture limiting means 7. Since the aperture limiting means 7 is the same as that described in the first embodiment, the aperture is limited at a numerical aperture of 0.6, and is incident on the objective lens 8.

The light beam 18 incident on the objective lens 8 is narrowed down with a numerical aperture of 0.6 to form a light spot 24 on the recording surface of the optical disk 9 having a substrate thickness of 0.6 mm. Next, the light beam 23 reflected by the optical disk 9 passes through the objective lens 8 and the aperture limiting means 7 again, and the optical path is bent again by the total reflection mirror 22. After that, the beam is reshaped at the beam shaping prism 21 a of the composite prism 21, then narrowed down by the condenser lens 19, and enters the first module 1.

Light beam 2 incident on first module 1
3 is diffracted by the hologram 1c and enters the photodetector 1b,
A focus control signal for causing the objective lens 8 to follow the recording surface by using the SSD method and a tracking control signal for causing to follow a track on the track surface by using the phase difference method are detected.

In FIG. 7, the 780 nm light beam 25 emitted from the second module 13 is a hologram 13c.
Through the condenser lens 20 to form a slightly divergent system, and enters the composite prism 21 at an incident angle θ4. Since the optical film 21c formed between the AS correction prism 21b and the beam shaping prism 21a transmits light having a wavelength of 780 nm, the composite prism 21 acts as a single prism.

At this time, when the installation angle of the composite prism 21 and the angle between the first surface and the second surface thereof are appropriately adjusted, almost no aberration occurs when the light passes through the composite prism 21. . Therefore, the light beam 25 transmitted through the composite prism 21 has almost no aberration, and after its optical path is bent by the total reflection mirror 22, only the inner peripheral portion corresponding to a numerical aperture of 0.45 is formed by the aperture limiting means 7. Penetrates into the objective lens 8 and forms a light spot 27 on the recording surface of the optical disc 15. Since the light beam 25 is incident on the objective lens 8 in a divergent system and the aperture is limited, the light spot 2 having almost no aberration even on the optical disk 15 having a base material thickness of 1.2 mm such as a CD.
7 is obtained.

The light beam 26 reflected by the optical disk 15
Passes through the objective lens 8 and the aperture limiting means 7 again, the optical path of which is bent by the total reflection mirror 22, and enters the composite prism 21. As in the forward path, the light beam 26 having a wavelength of 780 nm passes through the composite prism 21 with almost no change in aberration.

The light beam 26 incident on the second module 13 is diffracted by the hologram 13c and is incident on the photodetector 13b, and a focus control signal for causing the objective lens 8 to follow the recording surface using the SSD method. And a tracking control signal for following the track on the track surface using the push-pull method.

In this embodiment, as in the conventional example, the push-pull method is used for the sake of simplicity, but a three-beam method, which is generally used, may be used.

In the optical pickup of this embodiment, the objective lens 8 designed to have a wavelength of 650 nm, a disk base material thickness of 0.6 mm, and a numerical aperture of 0.6 is used. 3mm, 20mm each
An optical system is set in which the angle α3 between the first surface and the second surface of the beam shaping prism 21a is 5.35 °, and the angle α4 between the first surface and the second surface of the AS correction prism 21b is 5.9 °. .

Further, by setting the distance of the condensing lens 5 from the semiconductor laser 13a to be about 6 mm shorter than the point at which the beam passing through the condensing lens 5 becomes parallel light, the light having a wavelength of 650 nm is calculated. The beam was converged on the optical disk 9 having a substrate thickness of 0.6 mm and the light beam having a wavelength of 780 nm was converged on the optical disk 15 having a substrate thickness of 1.2 mm with a wavefront aberration of 10 mλ or less.

As described above, according to the present embodiment, the DVD
The side uses a beam shaping prism 21a for beam shaping, and the diverging light on the CD side uses an AS correction prism 21b for correcting aberrations generated when the light is transmitted through the beam shaping prism 21a, thereby providing a DVD light spot. 24
Also, good spots can be obtained for both the light spot 27 for CD and the light spot 27 for CD. Furthermore, by integrating the beam shaping prism 21a and the AS correction prism 21b with the optical film 21c interposed therebetween, the number of components can be reduced, and the size and cost of the optical pickup can be reduced.

It should be noted that the AS correction prism 21b determines the incident angle θ of the light beam 25 emitted from the second module 13.
4 can be adjusted appropriately to make the AS correction prism 21
The first surface and the second surface of b can be made parallel. In this case, since the AS correction prism 21b is a flat plate, the entire optical system can be configured at lower cost.

In short, the relationship between the position of the semiconductor laser 13a with respect to the optical film 21c and the position of the surface of the AS correction prism 21b facing the optical film 21c is that the light beam 25 from the semiconductor laser 13a is a beam shaping prism 21a.
The astigmatism for reducing astigmatism generated when the light beam 2 passes through the AS correction prism 21b
5, the optical film 21c of the AS correction prism 21b and the position of the surface facing the optical film 21c may be parallel or non-parallel.

Further, in order to prevent the light beam from being blurred due to the wavelength fluctuation of the laser light source, even if the beam shaping prism 21a is made of a plurality of glass materials as shown in FIG. Needless to say, the same effect as in the embodiment is obtained.

The AS correction prism 21b can also obtain a better spot by correcting astigmatism of the semiconductor laser 13a and optical components existing between the optical path from the semiconductor laser 13a to the condenser lens 20. it can.

Further, in the above-described second embodiment,
The AS correction prism 21b and the beam shaping prism 21a are not limited to being integrated.

(Third Embodiment) Next, a third embodiment will be described. The description of the same parts and operations as those in the first embodiment is omitted.

FIGS. 9 and 10 are diagrams showing the configuration of an optical pickup according to the third embodiment of the present invention. FIG. 9 shows a high-density optical disk 9 having a base material thickness of 0.6 mm in this embodiment. For reproduction, FIG. 2 shows a case where the optical disk 15 having a base material thickness of 1.2 mm is reproduced.

In FIG. 9, a first module 1 for reproducing a DVD has a semiconductor laser 1a having a wavelength of 650 nm, a hologram 1c for dispersing reflected light from the optical disk 9 to give a spatial change, and receives the reflected light. The photodetector 1b is integrally formed, and the positions of the photodetector 1b and the hologram 1c are adjusted before assembling the module. In this embodiment, the hologram is used as the element for separating the reflected light from the optical disk. However, a similar effect may be obtained by a prism.

Light beam 3 emitted from semiconductor laser 1a
Numeral 0 becomes a parallel or substantially parallel light beam light by the condenser lens 19, and is incident on the beam shaping prism 29 at an angle of θ5. The first and second surfaces of the beam shaping prism 29 have an angle of α5, and the second surface is covered with an optical film 29a. The optical film 29a is formed of a multilayer film that transmits light near a wavelength of 650 nm and totally reflects light near 780 nm.

Therefore, the light beam 30 is shaped by passing through the beam shaping prism 29. Thereafter, the optical path is bent by the total reflection mirror 22 and enters the aperture limiting means 7. Since the aperture limiting means 7 is the same as that described in the first embodiment, the aperture is limited at a numerical aperture of 0.6, and is incident on the objective lens 8. The light beam 30 that has entered the objective lens 8 is narrowed down with a numerical aperture of 0.6, and the substrate thickness is set to 0.
A light spot 32 is formed on the recording surface of the 6 mm optical disc 9.

Next, the light beam 3 reflected by the optical disk 9
The light path 1 passes through the objective lens 8 and the aperture limiting means 7 and the optical path is bent again by the total reflection mirror 22. Then, the optical film 2
9a, the beam is shaped again by the beam shaping prism 29, then condensed by the condenser lens 19, and the first module 1
Incident on. Light beam 3 incident on first module 1
1 is diffracted by the hologram 1c and enters the photodetector 1b,
A focus control signal for causing the objective lens 8 to follow the recording surface by using the SSD method and a tracking control signal for causing to follow a track on the track surface by using the phase difference method are detected.

Next, referring to FIG.
The light beam 33 of 780 nm emitted from the hologram 13c passes through the hologram 13c, becomes a slightly divergent system by the condenser lens 20, and enters the beam shaping prism 29 at an incident angle θ6.
Optical film 29 stretched on the second surface of beam shaping prism 29
Since a is totally reflected for light having a wavelength of 780 nm,
The beam shaping prism 29 functions as a total reflection mirror.

Thus, the light beam 33 reflected by the beam shaping prism 29 is further bent by the total reflection mirror 22 without being affected by the beam shaping prism 29 optically. Thereafter, only the inner peripheral portion corresponding to the numerical aperture of 0.45 is transmitted by the aperture limiting means 7 and is incident on the objective lens 8, and the light spot 3 is formed on the recording surface of the optical disk 15.
5 is formed. By allowing the light beam 33 to enter the objective lens 8 in a divergent system and by restricting the aperture, it is possible to cope with an optical disk 15 such as a CD having a base material thickness of 1.2 mm.

Light beam 34 reflected by optical disk 15
Passes through the objective lens 8 and the aperture limiting means 7 again, the optical path is bent by the total reflection mirror 22, and the beam shaping prism 29
Incident on. Light beam 3 having a wavelength of 780 nm as in the forward path
4 is totally reflected by the optical film 29a, and is not optically affected by the beam shaping prism 29.

Thereafter, the light beam 34 which has been converged by the condenser lens 20 and entered the second module 13 is diffracted by the hologram 13c and is incident on the photodetector 13b. A focus control signal for following a recording surface and a tracking control signal for following a track on a track surface using a push-pull method are detected.

Although the push-pull method is used in this embodiment as in the conventional example for the sake of simplicity, a three-beam method, which is commonly used, may be used.

As described above, according to the present embodiment, the DVD
The side uses a beam shaping prism 29 that performs beam shaping,
The divergent light on the CD side is totally reflected on the surface of the beam shaping prism 29, so that both the DVD light spot 32 and the DVD light spot 35 can obtain good spots. Furthermore, by configuring the beam shaping means and the light combining / separating means with one optical element, the number of parts can be reduced, and the size and cost of the optical pickup can be reduced.

Further, in order to prevent the light beam from being blurred due to the wavelength fluctuation of the laser light source, even if the beam shaping prism 29 is made of a plurality of glass materials as shown in FIG. Needless to say, the same effect as in the embodiment is obtained.

In each of the above embodiments, module elements are used for DVD recording / reproduction and CD recording / reproduction, but the same effect can be obtained even when the semiconductor laser, the optical receiver and the hologram are individual components. .

In the above-described embodiment, the configuration example using two light sources is used. However, the same effect can be obtained with a configuration using more light sources.

(Fourth Embodiment) Next, a fourth embodiment will be described.

FIGS. 12 and 13 are configuration diagrams showing the configuration of an optical pickup according to a fourth embodiment of the present invention.
FIG. 12 shows a case where the high-density optical disc 9 having a base material thickness of 0.6 mm is reproduced in this embodiment.
1 shows a case where an optical disk 15 of mm is reproduced.

The fourth embodiment differs from the third embodiment in that a beam shaping prism 36 is used instead of the beam shaping prism 29. That is, in the third embodiment, after the light beam 30 emitted from the semiconductor laser 1a is converted into parallel or substantially parallel light by the condenser lens 19, the light beam 30 is transmitted through the beam shaping prism 29 to be shaped. On the other hand, in the fourth embodiment, after the light beam 30 emitted from the semiconductor laser 1a is converted into parallel or substantially parallel light by the condenser lens 19, the light beam 30 is incident on the beam shaping prism 36, and is totally reflected. The beam is shaped by reflection at 36b, and the other parts are the same as in the third embodiment.

Therefore, according to the present embodiment, the DVD uses the beam shaping prism 36 for shaping the beam,
The divergent light on the side is totally reflected on the surface of the beam shaping prism 36, so that both the DVD light spot 32 and the DVD light spot 35 can obtain good spots. Furthermore, by configuring the beam shaping means and the light combining / separating means with one optical element, the number of parts can be reduced, and the size and cost of the optical pickup can be reduced.

Further, in order to prevent the light beam from being blurred due to the fluctuation of the wavelength of the laser light source, even if the beam shaping prism 36 is made of a plurality of glass materials as shown in FIG. Needless to say, the same effect as in the embodiment is obtained.

In each of the above embodiments, module elements are used for DVD recording or reproduction and CD recording or reproduction, but the same effect can be obtained even when the semiconductor laser, optical receiver and hologram are individual components. .

In the above-described embodiment, the configuration example using two light sources is used. However, a similar effect can be obtained with a configuration using more light sources.

Note that the condensing of light from each semiconductor laser on each optical disc and the detection of light reflected on the optical disc in the first to fourth embodiments are used for recording information on the optical disc. It can also be used for reproducing information recorded on an optical disc.
In other words, the optical pickups of the above-described first to fourth embodiments can be used not only for recording information on an optical disk but also for reproducing information. is there.

In the first to fourth embodiments described above, the wavelength of the light emitted from the semiconductor laser 1a of the first module 1 and the wavelength of the semiconductor laser 13a of the second module 13
Although it is assumed that the wavelength of light emitted by a is different, it is also possible to condense light of substantially the same wavelength on each of a plurality of optical discs having different substrate thicknesses to record information and reproduce information. Therefore, it is not limited that the wavelength of the light emitted from the semiconductor laser 1a and the wavelength of the light emitted from the semiconductor laser 13a are different. It may be substantially the same.

[0098]

As is apparent from the above description, the present invention can be applied to an optical system in which two light sources having different wavelengths are used and an objective lens is used for two wavelengths even when a beam shaping prism is used. It is possible to provide an optical pickup that can obtain good spot quality and that can be reduced in thickness and size.

That is, according to the present invention, the astigmatism generated when the CD side transmits the beam shaping prism used for the beam shaping means on the DVD side with the divergent light is provided with astigmatism correction means in the optical path only on the CD side. Thus, the CD side also obtains a good spot. Alternatively, the divergent light on the CD side reflects the surface of the beam shaping prism used for the beam shaping means on the DVD side to perform light synthesis with the DVD side, and also obtains a good spot on the CD side. As described above, the beam shaping prism is configured in the common optical system on the CD side and the DVD side, and the light combining / separating means is also provided, thereby reducing the size and thickness of the optical pickup.

[Brief description of the drawings]

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

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

FIG. 3 is a graph showing a variation in astigmatism when a condenser lens is moved according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an aperture limiting unit according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram in which chromatic aberration correcting means is added to the beam shaping prism according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram showing a configuration of an optical pickup according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a configuration of an optical pickup according to a second embodiment of the present invention.

FIG. 8 is a schematic diagram in which chromatic aberration correction means is added to a beam shaping prism according to the second embodiment of the present invention.

FIG. 9 is a configuration diagram showing a configuration of an optical pickup according to a third embodiment of the present invention.

FIG. 10 is a configuration diagram showing a configuration of an optical pickup according to a third embodiment of the present invention.

FIG. 11 is a schematic diagram in which a chromatic aberration correcting unit is added to a beam shaping prism according to the third embodiment of the present invention.

FIG. 12 is a configuration diagram showing a configuration of an optical pickup according to a fourth embodiment of the present invention.

FIG. 13 is a configuration diagram showing a configuration of an optical pickup according to a fourth embodiment of the present invention.

FIG. 14 is a schematic diagram in which a chromatic aberration correcting unit is added to a beam shaping prism according to a fourth embodiment of the present invention.

FIG. 15 is a configuration diagram showing a configuration of a conventional optical pickup.

FIG. 16 is a configuration diagram showing a configuration of a conventional optical pickup.

[Explanation of symbols]

 Reference Signs List 1 first module 1a semiconductor laser of first module 1b photodetector of first module 1c hologram of first module 2 light beam 3 AS correction prism 4 optical film 5 condenser lens 6 beam shaping prism 7 aperture limit Means 8 Objective lens 9 Optical disk 10 Light spot 11 Light beam (outgoing path) 12 Light beam (returning path) 13 Second module 13a Semiconductor laser of second module 13b Photodetector of second module 13c Hologram of second module Reference Signs List 14 light beam (outgoing path) 15 optical disk 16 light spot 17 light beam (return path) 18 light beam 19 condensing lens (DVD side) 20 condensing lens (CD side) 21 compound prism 21a beam shaping prism 21b AS correction prism 21c optical film 22 Total reflection mirror 23 Optical beam (Outbound path) 24 light spot 25 light beam (outbound path) 26 light beam (outbound path) 27 light spot 29 beam shaping prism 29a optical film 30 light beam (outbound path) 31 light beam (inbound path) 32 light spot 33 light beam (outbound path) Reference Signs List 34 light beam (return path) 35 light spot 36 beam shaping prism 36a optical film 36b total reflection film 37 light beam (outbound path) 38 condensing lens 39 beam shaping prism 40 compound prism 40a optical film 41 total reflection mirror 42 aperture limiting means 43 objective Lens 44 Optical disk 45 Light spot 46 Light beam (return path) 47 Second module 47a Semiconductor laser of second module 47b Photodetector of second module 47c Hologram of second module 48 Condensing lens 49 Light beam (outgoing path) ) 50 Optical disk 51 Light spot 52 Light beam (return path) 60 First module 60a Semiconductor laser 60b Photodetector 60c Hologram

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D119 AA04 AA41 BA01 CA09 DA01 DA05 EC02 EC03 EC45 EC47 FA08 JA07 JA09 JA14 JA16 JA17 JA63 JA64 LB07

Claims (10)

[Claims] A first light source for emitting a first light; a substantially planar reflecting means for reflecting the first light from the first light source; and the first light reflected by the reflecting means. Light condensing means for condensing the light; beam shaping means for beam shaping the first light condensed by the light condensing means; and the first beam shaped by the beam shaping means.
Converging means for converging the light on a first optical disk corresponding to the first light, a second light source for emitting a second light, and a second light source from the second light source. And an astigmatism imparting unit for imparting astigmatism, wherein the reflecting unit has a function of passing the second light, and the second light source emits light emitted by itself. The light converging means is arranged at a position passing through the reflecting means toward the light condensing means and the beam shaping means, and the converging means corresponds to the second light from the second light source corresponding to the second light Converging on a second optical disc, wherein the astigmatism imparting means is disposed between the second light source and the reflecting means, and has a light incident surface and a light exit surface; The second light beam having a substantially parallel relationship with the reflecting means, and The relationship between the position of the source and the position of the entrance surface of the astigmatism imparting means is astigmatism for reducing the astigmatism generated when the second light passes through the beam shaping means. Is in a positional relationship given to the second light after passing through the astigmatism imparting means. 2. The method according to claim 1, wherein the reflection unit is in contact with the emission surface of the astigmatism imparting unit, and the reflection unit and the astigmatism imparting unit are integrated. Optical pickup as described. 3. An optical element disposed between the second light source and the astigmatism imparting means, wherein the position of the second light source with respect to the reflection means and the astigmatism imparting means are provided. Is related to the position of the incident surface, astigmatism of the second light based on the second light source, and / or
Alternatively, the positional relationship is such that astigmatism for reducing astigmatism of the second light based on the optical element is added to the second light after passing through the astigmatism imparting means. The optical pickup according to claim 1 or 2, wherein: A first light source that emits a first light; a light condensing unit that condenses the first light from the first light source; and the first light collected by the light condensing unit. A beam shaping unit having a function of beam shaping the first light, and having a reflecting surface for reflecting the first light; and a first light beam shaped and reflected by the beam shaping unit. Converging means for converging on a first optical disk corresponding to one light, a second light source emitting a second light, and imparting a predetermined astigmatism to the second light from the second light source And a reflecting surface of the beam shaping unit has a function of passing the second light, and the second light source emits light emitted by itself. Passing through the beam shaping means and positioned toward the convergence means; The converging unit converges the second light from the second light source on a second optical disk corresponding to the second light, and the astigmatism imparting unit includes the second light source and the second light source. A beam incident surface and an exit surface, and the exit surface and the reflection surface of the beam shaping unit are substantially parallel to each other; The relationship between the position of the second light source with respect to the reflecting surface of the means and the position of the entrance surface of the astigmatism imparting means occurs when the second light passes through the beam shaping means. An optical pickup characterized in that astigmatism for reducing astigmatism is in a positional relationship given to the second light after passing through the astigmatism imparting means. 5. The method according to claim 1, wherein the reflection surface of the beam shaping unit is in contact with the emission surface of the astigmatism imparting unit, and the beam shaping unit and the astigmatism imparting unit are integrated. The optical pickup according to claim 4, wherein 6. An optical element disposed between the second light source and the astigmatism imparting means, further comprising: a position of the second light source with respect to the reflection surface of the beam shaping means; The relation between the position of the incident surface of the astigmatism imparting means and the astigmatism of the second light based on the second light source and / or the astigmatism of the second light based on the optical element The optical pickup according to claim 4, wherein astigmatism for reducing aberration is in a positional relationship given to the second light after passing through the astigmatism imparting means. 7. A first light source that emits a first light, a light condensing unit that condenses the first light from the first light source, and the first light that is condensed by the light condensing unit Beam shaping means for beam shaping the first light, and beam shaping means for passing the first light, and the first light which has been beam-shaped by the beam shaping means and has passed through the beam shaping means, Converging means for converging on a first optical disc corresponding to light; a second light source for emitting second light; and a second light source provided on an emission surface of the first light of the beam shaping means. Reflecting means for reflecting the second light from the light source and transmitting the first light, wherein the converging means converts the second light from the second light source into a second light Focusing on a second optical disc corresponding to light. Optical pickup. 8. A first light source that emits a first light, a light condensing unit that condenses the first light from the first light source, and the first light that is condensed by the light condensing unit Beam shaping means for beam shaping the first light, and a beam shaping means for reflecting the first light; and a first light beam shaped and reflected by the beam shaping means, the first light corresponding to the first light. Converging means for converging on the first optical disc; a second light source for emitting second light; and a light-emitting / receiving surface of the first light of the beam shaping means. Reflecting means for reflecting the second light and passing the first light, wherein the converging means corresponds to the second light from the second light source corresponding to the second light An optical pickup characterized by being converged on a second optical disc. 9. The apparatus according to claim 1, wherein a wavelength of said first light emitted from said first light source is different from a wavelength of said second light emitted from said second light source. , 5, 7,
9. The optical pickup according to any one of 8. 10. The apparatus according to claim 1, wherein said beam shaping means also has a function of correcting chromatic aberration of said first light from said first light source.
9. The optical pickup according to any one of 8.