JP2000322760A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and inexpensive optical pickup device by providing an essential optical member with an opening limiting function corresponding to different kinds of optical disk so as to reduce the weight of an actuator driving system. SOLUTION: An opening limiting means for converging first and second laser beams to first and second optical disks 1 and 2 with low aberration by an objective lens 23 is provided in a reflection mirror 22 as an essential constituting member. Thus, since two kinds of laser light are transmitted through the objective lens 23 to be optimally converged respectively on the recording surfaces of the corresponding optical disks 1 and 2, the optical disks 1 and 2 are played by suppressing the occurrence of spherical aberration. Since the opening limiting means is executed on the reflection mirror 22 as the essential constituting member, an inexpensive, compact and highly reliable actuator driving system is designed without increasing the number of part items.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for recording and reproducing optical disks having different substrate thicknesses and wavelengths.

[0002]

2. Description of the Related Art An optical pickup device reproduces information recorded on an optical disk by irradiating a recording surface of the optical disk on which information is recorded with laser light and detecting the intensity of the reflection of the laser light. . At this time, an objective lens is mounted on the optical pickup device in order to converge the laser light optimally on the recording surface. Currently used optical discs include CD (compact disc), CD-R (write-once compact disc) and
There are types such as VD (Digital Video Disk) and higher density optical disks have been developed. Therefore, it is desired that different types of optical disks can be reproduced compatible.

In order to reproduce a DVD which has been mass-produced and put into practical use as a high-density optical disc in recent years, a numerical aperture (hereinafter, referred to as “NA”) is used as an objective lens for optimally converging a laser beam onto a recording surface. ") (Hereinafter referred to as" high NA objective lens ")
Is used. However, when the NA of the objective lens is increased, aberration occurs with respect to the tilt of the optical disc, and the convergence state of the light spot is deteriorated. This aberration is mainly called coma, and is proportional to the cube of the NA of the objective lens and the thickness of the protective layer of the optical disk. Therefore, the DVD has a substrate thickness of 0.6 mm.
By solving this problem, the problem relating to coma can be solved.

[0004] An optical pickup device for reproducing a DVD is required to be able to reproduce compatible CDs that are already popular, but the substrate thickness of the CD is 1.2 mm unlike that of a DVD. When the substrate thickness of the optical disc deviates from the design value, a convergence position of light passing through the lens center portion and light passing through the peripheral portion occurs in a convergence position called spherical aberration. The designed high NA objective lens causes a spherical aberration with respect to the CD, and it is impossible to reproduce the recorded information of the CD using the high NA objective lens.

On the other hand, increasing the density of a DVD is achieved by shortening the wavelength of laser light to be irradiated in addition to increasing the NA of the above-mentioned objective lens. A laser beam having a shorter wavelength than that used is used. 650 nm which is the operating wavelength of DVD
(Or 635 nm) laser light,
Although it is possible to reproduce a CD having a working wavelength of 780 nm, it is not possible to reproduce a CD-R with laser light having a wavelength of 650 nm due to the reflectance characteristics of the recording layer. Therefore, the wavelength 7 is required for reproducing the CD-R.
Since it is necessary to irradiate 80 nm laser light, D
An optical pickup device capable of compatible reproduction of VD and CD (including CD-R) requires a laser light source of 780 nm wavelength in addition to a laser light source of 650 nm wavelength compatible with DVD.

A schematic configuration of a typical optical pickup device for compatible reproduction of DVDs and CDs (including CD-Rs) using laser light sources of two different wavelengths will be described with reference to FIG. The optical pickup device shown in FIG.
This is called a lens system, and FIG.
When reproducing D1 (substrate thickness: 0.6 mm), FIG.
(B) is a schematic diagram when reproducing CD2 (substrate thickness: 1.2 mm).

The structure of the optical pickup device will be described below with reference to FIG.
Description will be made based on (a). Wavelength 6 corresponding to DVD1
Close to the first optical system 3 on the optical path of the laser light emitted from the first optical system 3 in which a laser light source that emits a laser beam of 50 nm and a photodetector that receives the signal light from the DVD 1 are provided. A wavelength selection prism 4, a condenser lens 5, and a reflection mirror 6 are arranged in this order from the side. Here, the first optical system 3 in which the plurality of components described above are arranged.
The axis connecting the mirror 6 and the reflection mirror 6 is indicated by an alternate long and short dash line as an optical axis A.

On the optical axis B orthogonal to the wavelength selection prism 4 on the optical axis A, there are provided a laser light source for emitting laser light having a wavelength of 780 nm corresponding to CD2 and a photodetector for receiving signal light from CD2. The deployed second optical system 7 is arranged. Further, an actuator drive system 8 is disposed on the optical axis C where the laser light is reflected in the vertical direction by the reflection mirror 6. The actuator drive system 8 has a high N which is designed to correspond to the substrate thickness of the DVD 1.
An A objective lens 9 and a low NA objective lens 10 designed to correspond to the substrate thickness of the CD 2
The two objective lenses 9 and 10 are mechanically switchable by a control circuit 12.

[0009] DVD1 and CD2 are arranged at the condensing position of the laser beam transmitted through the objective lenses 9 and 10 moved on the optical axis C by the control circuit 12.

The wavelength selection prism 4 transmits the laser beam of 650 nm of the first optical system 3 which is the wavelength used for the DVD 1 and 780 n of the second optical system 7 which is the wavelength used for the CD.
m, which reflects the laser light of m.
Has a function of converting the emission angle of laser light by transmitting the light through the condenser lens 5. In the case of this device, the laser light is converted into parallel light. Further, the reflection mirror 6 reflects the laser light transmitted through the condenser lens 5 in the vertical direction to change the traveling direction, thereby entering the actuator drive system 8.

The D of the optical pickup device having such a structure is
The reproduction operation of VD1 will be described. The laser light having a wavelength of 650 nm emitted from the first optical system 3 passes through the wavelength selection prism 4 and is converted by the condenser lens 5 into parallel light having the same divergence angle, and becomes parallel light. The laser light travels along the optical axis C by the reflection mirror 6. In the actuator drive system 8, the high NA objective lens 9 is arranged on the optical axis C under the control of the control circuit 12, so that the laser light is optimally converged on the recording surface of the DVD 1 by the high NA objective lens 9. And D
The laser light reflected on the recording surface of VD1 becomes signal light,
Following the same path in reverse, the light travels to the first optical system 3, and the intensity of the signal light is detected, whereby the information recorded on the DVD 1 is reproduced.

Next, the reproduction operation of the CD 2 will be described with reference to FIG. The laser light emitted from the second optical system 7 is reflected by the wavelength selection prism 4 so as to travel along the optical axis A, converted into parallel light by the condenser lens 5, and converted into parallel light. The light travels along the optical axis C by the reflection mirror 6. In the actuator drive system 8, the low NA objective lens 10 is arranged on the optical axis C under the control of the control circuit 12, so that the laser light is optimally converged on the recording surface of the CD 2 by the low NA objective lens 10. Then, the laser light reflected by the recording surface of the CD 2 becomes signal light, and follows the same path in reverse to the second optical system 7.
And the CD is detected by detecting the intensity of the signal light.
2 is reproduced.

The optical pickup device shown in FIG. 8 is different from the two-lens type optical pickup device shown in FIG.
The DVD 1 and the CD 2 are compatiblely reproduced by one objective lens, and the configuration of the actuator drive system 13 will be described below. (Other configurations are the same as those of the two-lens type optical pickup device, and therefore, illustration and description are omitted.) ). The actuator drive system 13 includes a high NA objective lens 14 designed to correspond to the substrate thickness of the DVD 1.
Are mounted so as to be located on the optical axis C, and a movable aperture limiting plate 15 is mounted together with a driving mechanism 16, and the driving of the driving mechanism 16 is controlled by a control circuit 17. Thereby, the movable aperture limiting plate 15 can be switched so as to be located on the optical axis C (see FIG. 8B) or to be off the optical axis C (see FIG. 8A). I have.

As shown in FIG. 9, the movable opening limiting plate 15 has an opening 15a of a predetermined size formed at the center thereof, and this opening 15a is capable of transmitting laser light.
The other range is the light shielding portion 15b through which the laser light cannot pass.
It has become.

In the optical pickup device having such a configuration, D
When reproducing VD1, as shown in FIG.
The control of the control circuit 17 allows the actuator drive system 13
In this case, the movable aperture limiting plate 15 is previously positioned so as to be off the optical axis C. The laser beam having the wavelength corresponding to DVD1 travels along the optical axis C, and is converged by transmitting through the high NA objective lens 14 designed for NA corresponding to DVD1, and is optimally collected on the recording surface of DVD1. Light. Then, the laser light reflected on the recording surface of the DVD 1 becomes signal light, and the intensity of the signal light is detected.

Subsequently, when reproducing the reproduction operation of the CD2, the movable aperture limiting plate 15 is previously positioned on the optical axis C under the control of the control circuit 17, as shown in FIG. . The laser light having a wavelength corresponding to CD2 travels along the optical axis C and enters the movable aperture limiting plate 15. Since the laser light is shielded by the light-shielding portion 15b and can be transmitted only through the opening 15a, the laser light passes through only the central portion of the light beam cross-section, thereby restricting the light beam diameter and entering the high NA objective lens 14. become. Therefore, even if DV
High NA objective lens 14 designed for NA corresponding to D1
However, when reproducing the CD2, the diameter of the laser beam to be irradiated is narrowed, so that the laser beam is converged by the high NA objective lens 14 to be optimally condensed on the recording surface of the CD2. Then, the laser light reflected on the recording surface of CD2 becomes signal light, and the intensity of the signal light is detected.

[0017] Furthermore, a DVD is formed by one objective lens.
Another example of an optical pickup device configured to perform compatible playback of CD 1 and CD 2 will be described with reference to FIGS.
The actuator drive system 18 includes a high NA objective lens 19 designed to correspond to the substrate thickness of the DVD 1,
A wavelength selection filter 20, which is an aperture limiting element, is mounted on the optical axis C. The wavelength selection filter 20 utilizes the wavelength selection characteristics of the optical film, and as shown in FIG. 11, a center filter portion 20a of a predetermined size (a hatched portion indicated by a one-dot chain line in FIG. 11) is formed at the center thereof. And
A filter portion 20b (hatched portion in the figure) is formed therearound.

The filter section 20b has a characteristic of transmitting a laser beam of 650 nm, which is the wavelength used for DVD1, and reflecting a laser beam of 780nm, which is the wavelength used for CD2. Both the 650 nm and 780 nm laser beams can be transmitted, and the filter unit 20 for the laser beam corresponding to DVD1
It has the property of correcting the phase difference with the laser light transmitted through b.

With the optical pickup device having such a configuration, D
When reproducing VD 1, as shown in FIG. 10A, a laser beam having a wavelength corresponding to DVD 1 travels along optical axis C and enters wavelength selection filter 20. DV
The laser light of the wavelength corresponding to D1 is
a and the filter section 20b, the entire light beam is transmitted, converged by the high NA objective lens 19, and
The light is optimally focused on the recording surface of No. 1. Then, the laser light reflected on the recording surface of the DVD 1 becomes signal light, and the intensity of the signal light is detected.

On the other hand, when reproducing the reproduction operation of the CD2, as shown in FIG. 10B, the laser light having the wavelength corresponding to the CD2 travels along the optical axis C, and To enter. This laser light is applied to the filter unit 20.
Since the light is reflected by b, the light passes through only the center filter portion 20a and passes through only the center of the light beam cross section, whereby the light beam diameter is restricted and enters the high NA objective lens 19. For this reason, even if the high NA objective lens 19 is designed to have an NA corresponding to DVD1, when reproducing CD2,
Since the diameter of the laser beam to be irradiated is narrowed, the laser beam is converged by the high NA objective lens 19 to be optimally focused on the recording surface of the CD2. Then, the laser light reflected on the recording surface of CD2 becomes signal light, and the intensity of the signal light is detected.

As described above, the optical pickup device having one objective lens 14 and 19 described with reference to FIGS.
For a laser beam of 0 nm, the total luminous flux is converted to a wavelength of 780 nm.
By passing only the central portion of the light beam cross section through the objective lenses 14 and 19 for the laser beams of the first and second laser beams, respectively, the two types of laser beams having different wavelengths can be used.
9 can be changed. Therefore, the optimum wavelength and the NA of the objective lens can be selected for the two types of optical discs 1 and 2 having different substrate thicknesses, DVD1 and CD2, thereby reducing the occurrence of spherical aberration due to the difference in substrate thickness. Thus, both optical discs 1 and 2 can be compatiblely reproduced.

[0022]

By the way, the conventional optical pickup device shown in FIG. 7 uses a high NA objective lens 9 and a low NA objective lens 10 to reproduce different types of optical disks (ie, DVD1 and CD2). Is mounted on the actuator drive system 8, there is a problem described below.

That is, the optical pickup device shown in FIG. 7 has two objective lenses, a high NA objective lens 9 and a low NA objective lens 10, and a lens driving mechanism 11 for moving these objective lenses according to the types of the optical disks 1 and 2. Is incorporated in the actuator drive system 8, so that the weight of the actuator drive system 8 increases. When the weight of the actuator drive system 8 increases in this way, focusing and tracking performance may be degraded, and it may be a factor that hinders the speed-up of the lens following operation for the optical disks 1 and 2. Further, since a control circuit 12 for controlling the driving of the lens driving mechanism 11 is also required, it is difficult to realize a large-sized apparatus having a large number of parts and a low cost.

On the other hand, the optical pickup device having the configuration shown in FIG. 8 can reproduce different types of optical discs 1 and 2 with one objective lens 14, so that two objective lenses 9 and 10 shown in FIG. Although the weight of the actuator drive system 13 on which the objective lens 14 is mounted can be reduced as compared with the optical pickup device having the above-described configuration, the actuator drive system is required to focus laser beams on the recording layers of the optical discs 1 and 2, respectively. 13 has a movable aperture limiting plate 1
5 and a drive mechanism 16 are incorporated.
7 is also required, so that a further reduction in the number of parts is required. Also, in order to improve the focusing and tracking performance and speed of the actuator drive system 13,
It is desirable that the weight be reduced.

On the other hand, in the optical pickup device having the structure shown in FIG. 10, the wavelength selection filter 20 for limiting the aperture is used to reproduce the optical disks 1 and 2 of different types by one objective lens 14. Since the optical pickup device is fixed on C, the drive mechanism 16 and the like are not required unlike the optical pickup device shown in FIG. 8, so that the actuator drive system 18 can be reduced in weight, but the focusing and tracking performance can be improved, and the speed can be improved. Therefore, further weight reduction is demanded. When reproducing the CD2, the laser beam having a wavelength of 780 nm is reflected by the filter unit 20b of the wavelength selection filter 20 and transmitted only through the center filter unit 20a, so that only the center of the cross section of the light beam passes and the objective lens 19 Controlling the effective NA,
In this case, the reflected light from the filter unit 20b may become return light noise. In this case, the electric characteristics of the optical pickup device may be deteriorated.

Accordingly, the present invention has been made in view of the above circumstances, and limits the luminous flux diameters of two types of laser beams having different wavelengths, thereby changing the effective NA of the objective lens and changing the types of the laser beams. By providing the essential optical members with an aperture limiting function that corresponds to each optical disc,
It is an object of the present invention to provide a small and inexpensive optical pickup device in which the weight of an actuator drive system is reduced.

[0027]

In order to achieve the above object, an optical pickup device according to the present invention is characterized in that, in claim 1, first and second types of optical disks having different disk substrate thicknesses and operating wavelengths are used. In an optical pickup device for reproduction, a first laser light source that emits a first laser light having an oscillation wavelength corresponding to the first optical disc, and a first laser light that detects a first signal light reflected by the first optical disc. A first optical system including one photodetector, a second laser light source that emits a second laser beam having an oscillation wavelength corresponding to the second optical disk, and a second laser light source that reflects off the second optical disk. A second optical system including a second photodetector that detects the second signal light, and guides the first and second laser lights on the same optical path, and transmits the first signal light to the first signal light. Of the second signal Optical multiplexing / demultiplexing means for splitting the first signal light and the second signal light so as to guide light to the second photodetector, and converting the radiation angles of the first and second laser lights. A focusing lens, and an objective lens for focusing the first and second laser beams on the first and second optical discs, respectively, with respect to a recording surface of the first and second optical discs. An actuator drive system for controlling the position of the objective lens; and the condensing lens and the objective for reflecting the traveling directions of the first and second laser beams toward the first and second optical disks. A reflection mirror disposed between the first and second optical disks. The reflection mirror is configured to cause the first and second laser beams to converge on the first and second optical discs with low aberration by the objective lens. Having aperture restriction means And it features.

According to a second aspect of the present invention, in the first aspect of the present invention, the aperture limiting means includes a reflecting portion for reflecting both the first and second laser beams, and the first and second laser beams. A limiting portion that reflects one of the laser beams and transmits the other, and reflects the first and second laser beams by the reflection mirror, thereby changing the beam diameter. I do.

According to a third aspect of the present invention, in the second aspect of the present invention, the reflecting portion is formed by forming a dielectric multilayer film on a laser beam reflecting surface of the reflecting mirror.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the limiting portion is formed by forming a dielectric multilayer film on a laser beam reflecting surface of the reflection mirror.

The present invention according to claim 5 provides the invention according to claims 1 to 4
In the invention described in any one of the above, an antireflection means for suppressing reflection of the first and second laser lights is provided on a surface of the reflection mirror different from the laser light reflection surface.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the antireflection means comprises a dielectric multilayer film.

The present invention according to claim 7 provides the invention according to claims 1 to 6
In the invention described in any one of the first to third aspects, the optical path length between the second laser light source and the condenser lens is set such that the second laser light source becomes diffused light by passing through the condenser lens. It is characterized by the following.

The present invention according to claim 8 provides the invention according to claims 1 to 7
In the invention described in any one of the above, the optical multiplexing / demultiplexing means is configured by an optical path adjusting unit that transmits the first laser light and reflects the second laser light.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, the optical path adjusting section is made of a dielectric multilayer film.

The present invention according to claim 9 provides the invention according to claims 1 to 9
In the invention described in any one of the above, one of the first and second optical systems is a laser module in which a light source and a photodetector are integrally formed.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, each of the first and second optical systems is a laser in which a light source and a photodetector are integrally formed. It is a module.

According to the present invention, with the above structure, the aperture limiting means for converging the first and second laser beams on the first and second optical discs with low aberration by the objective lens, respectively, is provided.
By providing a reflection mirror, which is an essential optical member,
When the first and second laser beams are reflected by the reflecting mirror, the beam diameter is restricted by the aperture restricting means, so that the effective NA of the objective lens is reduced by the recording surface of the first and second optical disks. To reproduce the two types of optical disks having different substrate thicknesses.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical pickup device according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The same members as those of the optical pickup device described in the section of the related art are denoted by the same reference numerals, and description thereof will be omitted except for necessary parts.

The optical pickup device shown in FIG. 1 is a first embodiment of the present invention, and differs from the conventional optical pickup device in the configuration of an actuator drive system 21 and a reflection mirror 22. In FIG. 1, the optical path of the laser beam when reproducing the DVD 1 is schematically indicated by a solid line, and the optical path of the laser beam when reproducing the CD 2 is schematically indicated by a dotted line.

The actuator drive system 21 includes a DVD 1
A high NA objective lens 23 whose NA is designed to correspond to the substrate thickness is mounted on the optical axis C. Further, the actuator drive system 21 processes position detection information detected by detectors (not shown) in the first optical system 3 and the second optical system 7,
The optical discs (DVD1 and CD2) and the turntable are corrected by correcting the runout of the turntable, the tilt of the transfer mechanism, the tilt of the optical pickup device, the shift of the focal position, the shift of the track following, and the like. It is designed so that it can always follow.

The reflection mirror 22 converts the laser light traveling along the optical axis A into the optical axis C on which the optical disks 1 and 2 are arranged.
Aperture limiting means for vertically reflecting the laser light so as to travel along the axis, and for converging the two wavelengths of the laser light of different types to the optical disks 1 and 2 with the high NA objective lens 23 to have low aberrations, respectively. have. This aperture limiting means is used to reduce the effective NA of the high NA objective lens 23.
Is changed in accordance with the type of the optical discs 1 and 2 to be reproduced. For this reason, the reflection mirror 22 shown in FIG. An elliptical reflective portion 22a is formed as a film,
Further, a limiting portion 22b is formed on the outer peripheral portion of the reflecting portion 22a.

As shown in FIG. 3, the restriction unit 22b
It has the property of reflecting laser light of 650 nm, which is the wavelength used for D1, almost completely, and transmitting laser light of 780 nm, which is the wavelength used for CD2, almost completely.
The reflection part 22a does not depend on the wavelength of the laser light used,
It has the property of reflecting laser light almost completely. Further, the reflection part 22a and the restriction part 22b have a wavelength of 650n.
The film thickness is set so that the phase difference before and after the reflection of the m laser beam is within ± 8 °. As the reflection part 22a and the restriction part 22b that can obtain such characteristics, for example, those in which a dielectric multilayer film is formed using SiO ₂ or TiO ₂ are used.

At this time, an anti-reflection portion 22c is formed on a non-reflection surface of the reflection mirror 22 (hereinafter, referred to as a "back surface"), so that a wavelength of 780 nm that passes through the restriction portion 22b and travels to the back surface is formed. It is desirable to prevent the laser light from being reflected on the back surface and becoming stray light.
Further, a similar effect can be obtained by forming a light absorbing film instead of the antireflection portion 22c. In addition, the reflection part 22
The shape and area of a are designed to have optimal values such that the wavefront aberration can be kept low while adjusting the lens system and the optical path length so that the laser beam has low aberration when focused on the recording layer of CD2. ing.

Further, the first optical system 3 and the second optical system 7 shown in FIG. 1 are determined by the position of the condenser lens 5, and the first optical system 3 and the second optical system 7 The distance between the two 3 and 7 and the condenser lens 5 is set so that the emitted laser light passes through the condenser lens 5 and becomes a parallel light flux.

FIG. 4 shows a configuration of the wavelength selection prism 4 as an optical multiplexing / demultiplexing means used in the embodiment of the present invention. The wavelength selection prism 4 has a configuration in which two prisms having a triangular prism shape are fixed to each other by bonding predetermined side surfaces thereof so as to form a quadrangular prism shape.
Is formed. As shown in FIG. 5, the optical path adjusting unit 4a has a property that the transmission characteristics of the wavelength are inverted around the wavelength of 720 nm, so that the laser light of the wavelength of 650 nm corresponding to DVD1 is almost completely transmitted, and the optical path adjusting unit 4a of CD2 is Wavelength 78
The laser light of 0 nm is almost completely reflected. Such an optical path adjusting unit 4a is formed of a dielectric multilayer film using, for example, SiO ₂ or TiO ₂ .

By providing the wavelength selection prism 4 having such an optical path adjusting section 4a, the laser light having a wavelength of 650 nm emitted from the first optical system 3 along the optical axis A during the reproduction of the DVD 1 can be adjusted. The laser beam that travels straight through the portion 4a and is reflected by the recording layer of the DVD 1 is
The light passes through the optical path adjustment unit 4 a and proceeds to the first optical system 3.
On the other hand, at the time of CD2 reproduction, the laser light having a wavelength of 780 nm emitted from the second optical system 7 along the optical axis B travels along the optical axis A by being reflected by the optical path adjusting unit 4a. The laser beam reflected by the recording layer of the CD 2 is reflected by the optical path adjusting unit 4a, travels along the optical axis B, and is guided to the second optical system 7.

The operation of reproducing the DVD 1 in the optical pickup device of the present invention having such a configuration will be described. FIG.
As shown in the figure, the wavelength 65 emitted from the first optical system 3
The laser light of 0 nm is transmitted through the optical path adjusting unit 4a of the wavelength selection prism 4, and is converted by the condenser lens 5 into parallel light having an equal divergence angle, and the parallel laser light is reflected. The light travels along the optical axis C by the mirror 22. At this time, as shown in FIG. 2A, since the laser light is reflected by the reflecting portion 22a and the limiting portion 22b of the wavelength selection mirror 22, all the light beams enter the high NA objective lens 23 and are converged. Is focused on the recording layer of DVD1. Then, the laser light reflected on the recording surface of the DVD 1 becomes signal light, travels in the same path in reverse to the first optical system 3, and detects the intensity of the signal light, thereby obtaining a D signal.
The recorded information of VD1 is reproduced.

On the other hand, when reproducing CD2, the laser light having a wavelength of 780 nm emitted from the second optical system 7
The laser light reflected by the optical path adjusting unit 4a of the wavelength selection prism 4 and traveling along the optical axis A, converted into parallel light by the condenser lens 5, and converted into parallel light is reflected by the reflection mirror 22 onto the optical axis C. Proceed along. At this time, the laser light
As shown in FIG. 2B, only the laser beam transmitted through the limiting portion 22b of the wavelength selection mirror 22 and reflected by the reflecting portion 22a travels along the optical axis C. It enters the NA objective lens 23. Therefore, even if the high NA objective lens 23 corresponding to the DVD 1 is used,
At the time of reproducing the CD2, the effective NA of the high NA objective lens 23 is reduced by narrowing the beam diameter of the laser light to be irradiated.
Is changed so as to correspond to the substrate thickness of CD2.
The light is focused on the recording surface of CD2. The laser light reflected on the recording surface of the CD2 becomes signal light, travels in the same path in reverse to the second optical system 7, and the intensity of the signal light is detected. Will be played.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. The optical pickup device shown in FIG. 6 has the same components as those of the optical pickup device described in the first embodiment shown in FIG.
The arrangement distances are different. That is, the laser beam to be focused on the recording layer of CD2 is slightly diffused so as to correct the spherical aberration with respect to the substrate thickness of CD2. It is set to be slightly diffused by transmission. On the other hand, as in the first embodiment, the first optical system 3 is disposed at a distance at which the emitted light is collimated by the condenser lens 5. In the optical pickup device of the present invention, the distance from the second optical system 7 to the condenser lens 5 is arranged to be shorter than the distance from the first optical system 3 to the condenser lens 5.

With this arrangement, at the time of reproducing the CD 2, the laser light emitted from the second optical system 7 travels along the optical axis A while being transmitted through the condenser lens 5 and converted into a diffused light beam. . The laser light that has become a diffused light beam is shown in FIG.
Since only the laser beam reflected by the reflecting portion 22a of the wavelength selection mirror 22 travels along the optical axis C, the high-NA objective lens 23 has an optimum NA for the CD2 as shown in FIG. The laser beam is focused on the recording layer of CD2 by the high NA objective lens 23. At this time, since the laser light is slightly diffused, the spherical aberration is reduced.
The laser light reflected by the recording layer follows the same path and is received by the second optical system 7 to obtain recorded information.

At this time, the divergence angle of the laser light diffused by the condenser lens 5 and the reflection portion 22a of the reflection mirror 22
Is designed in consideration of the lens system and the optical path length so that the laser beam is condensed on the recording layer of the CD2 with low aberration, so that the wavefront aberration of the beam spot condensed on the recording layer of the CD2 is Can be made lower. Note that the operation of reproducing the DVD 1 is the same as in the first embodiment, and a description thereof will be omitted.

In the first and second embodiments of the present invention, the first optical system 3 and the second optical system 7 have an oscillation wavelength of 650 nm (635 nm is also possible) and 780 nm.
, And a photodetector, for example, a photodetector-integrated laser module is used.
Further, depending on the shape and cost of the optical pickup device, the optical path may be branched by a half mirror, a beam splitter, or the like, and a laser light source and a photodetector may be separately arranged.

Further, in the reflecting mirror 22, the reflecting portion 22a, the limiting portion 22b and the anti-reflection portion 22c formed of a dielectric multilayer film having a predetermined wavelength reflectance characteristic, and the dielectric multilayer of the wavelength selection prism 4 The optical path adjusting unit 4a made of a film is not particularly limited to being formed by a dielectric multilayer film, as long as it can obtain desired wavelength reflectance characteristics. It may be formed. Further, the reflection mirror 22 is not limited to a flat plate shape, and may be, for example, a triangular prism shape.

[0055]

Since the present invention has the structure of the optical pickup device constructed as described above, according to the first aspect of the present invention, the first and second laser beams are transmitted by the objective lens to the first and second laser beams. The aperture limiting means for converging each optical disc to a low aberration is provided on the reflection mirror, which is an essential component, so that the two types of laser light pass through the objective lens, and thus are recorded on the recording surface of the corresponding optical disc. Converge optimally. Therefore, the occurrence of spherical aberration caused by the difference in substrate thickness between the two types of optical discs is suppressed, so that different types of optical discs can be reproduced. Since the aperture limiting means is applied to the reflection mirror, which is an essential component, it is possible to design an actuator drive system that is inexpensive without increasing the number of parts and that is smaller and has higher performance.

According to the second aspect of the present invention, the aperture limiting means of the reflection mirror reflects the first and second laser beams, and reflects the first and second laser beams together. The first and second laser beams are made different by changing the beam diameter by reflecting the first and second laser beams with a reflection mirror.
By being reflected by the reflection mirror, the effective NA of the objective lens can be changed according to the type of the optical disk, and different types of optical disks can be reproduced.

According to the third and fourth aspects of the present invention, since the reflection part and / or the restriction part which is the aperture restriction means is formed of a dielectric multilayer film, the configuration is simple and light.

According to the fifth aspect of the present invention, antireflection means for suppressing reflection of laser light is provided on a surface of the reflection mirror different from the laser light reflection surface, so that unnecessary laser light is prevented from reentering the optical path. Therefore, the electric characteristics of the optical pickup device are not affected.

According to the sixth aspect of the present invention, since the anti-reflection means is made of a dielectric multilayer film, its structure is simple and lightweight.

According to the seventh aspect of the present invention, the optical path length between the second laser light source and the condenser lens is set so as to be diffused light when the second laser light source passes through the condenser lens. Since the laser light converged on the recording layer of the second optical disk is slightly diffused, the spherical aberration can be suppressed, and therefore, the spherical aberration caused by the difference in the substrate thickness between the first and second optical disks. Can be corrected.

According to the eighth aspect of the present invention, since the optical multiplexing / demultiplexing means is constituted by an optical path adjusting unit for transmitting the first laser light and reflecting the second laser light, the different types of laser light can be efficiently transmitted. I can guide you.

According to the ninth aspect of the present invention, since the optical path adjusting portion of the optical multiplexing / demultiplexing means is formed of a dielectric multilayer film, the configuration is simple and lightweight.

In the tenth and eleventh aspects of the present invention,
Since the first optical system and / or the second optical system is constituted by a laser module in which a light source and a photodetector are integrated, the size of the apparatus can be reduced, the number of parts can be reduced, and the adjustment thereof can be performed. The construction method is easy and the work process can be simplified.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing a configuration of a reflection mirror which is a main part of the present invention.

FIG. 3 is a table showing wavelength reflectance characteristics of a reflecting portion and a limiting portion of a reflecting mirror.

FIG. 4 is a schematic diagram showing a configuration of a wavelength selection prism which is a component of the optical pickup device of the present invention.

FIG. 5 is a table showing wavelength transmittance characteristics of an optical path adjusting film of a wavelength selection prism.

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

FIG. 7 is a schematic diagram showing a configuration of a conventional optical pickup device.

8 is a schematic diagram showing a configuration of a conventional optical pickup device different from FIG.

FIG. 9 is a perspective view showing a configuration of a movable opening limiting plate.

FIG. 10 is a schematic diagram showing a configuration of a conventional optical pickup device different from FIG.

FIG. 11 is a schematic diagram illustrating a configuration of a wavelength selection filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DVD 2 CD 3 1st optical system 7 2nd optical system 21 Actuator drive system 22 Reflection mirror 23 High NA objective lens

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D119 AA01 AA04 AA17 AA38 AA41 BA01 BB01 BB03 CA16 DA01 DA05 EA02 EA03 EB11 EB15 EC01 EC45 EC47 EC49 FA02 FA05 FA08 JA19 JA26 JA57 JA63 JA65 KA02 KA04 LB07 LB11

Claims (11)

[Claims] 1. An optical pickup device for reproducing first and second types of optical disks having different disk substrate thicknesses and operating wavelengths, wherein a first laser beam having an oscillation wavelength corresponding to the first optical disk is emitted. A first laser light source, a first optical system including a first photodetector that detects a first signal light reflected by the first optical disc, and an oscillation wavelength corresponding to the second optical disc. A second optical system including a second laser light source that emits a second laser light, and a second photodetector that detects a second signal light reflected by the second optical disc; And the second laser light on the same optical path,
Guiding the first signal light to the first photodetector, and guiding the first signal light and the second signal light so as to guide the second signal light to the second photodetector. An optical multiplexing / demultiplexing means for branching; a condenser lens for converting a radiation angle of the first and second laser lights; and a condenser for focusing the first and second laser lights on the first and second optical disks, respectively. An actuator drive system mounted with an objective lens for controlling the position of the objective lens with respect to the recording surfaces of the first and second optical discs; and In order to reflect light toward the first and second optical discs, the optical disc comprises a reflection mirror disposed between the condenser lens and the objective lens, wherein the reflection mirror includes the first and second lasers. Light is directed to the first and second optical disks by the objective lens. An optical pickup device comprising an aperture limiting means for converging to a low aberration. 2. An aperture limiting means, comprising: a reflector for reflecting both the first and second laser beams; and a limiter for reflecting one of the first and second laser beams and transmitting the other. The optical pickup device according to claim 1, further comprising: a light-reflecting unit configured to reflect the first and second laser lights by the reflection mirror so as to vary light beam diameters. 3. The optical pickup device according to claim 2, wherein the reflection section has a dielectric multilayer film formed on a laser beam reflection surface of the reflection mirror. 4. The optical pickup device according to claim 2, wherein said restricting portion has a dielectric multilayer film formed on a laser beam reflecting surface of said reflection mirror. 5. The reflection mirror according to claim 1, wherein an antireflection means for suppressing reflection of the first and second laser beams is provided on a surface of the reflection mirror different from the laser beam reflection surface. An optical pickup device as described in Crab. 6. The optical pickup device according to claim 5, wherein said antireflection means comprises a dielectric multilayer film. 7. An optical path length between the second laser light source and the condenser lens is set so as to be a diffused light when the second laser light source passes through the condenser lens. The optical pickup device according to claim 1. 8. The optical multiplexer / demultiplexer according to claim 1, wherein the optical multiplexing / demultiplexing unit includes an optical path adjusting unit that transmits the first laser light and reflects the second laser light. An optical pickup device as described in Crab. 9. The optical pickup device according to claim 8, wherein said optical path adjusting section is made of a dielectric multilayer film. 10. The apparatus according to claim 1, wherein one of the first and second optical systems is a laser module in which a light source and a photodetector are integrally formed. Optical pickup device. 11. The first and second optical systems each include:
The optical pickup device according to any one of claims 1 to 9, wherein the light source and the photodetector are a laser module integrally formed.