JPH09204684A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup for recording and/or erasing and/or reproducing information for a plurality of recording media having different thickness of substrate. SOLUTION: The optical pickup comprises light sources 2, 9 irradiating a diverging luminous flux, a coupling lens 4 for converting the diverging state of luminous flux from the light sources 2, 9, an objective lens 7 for condensing a luminous flux passed through the coupling lens 4 onto the recording surface of a recording medium 8, an optical element 5 for separating the incident light to a recording medium 1 from a light reflected on the recording media 1, 8, and light receiving element 13 receiving the light separated through the optical element 5 and reflected on the recording media 1, 8, wherein information is recorded and/or erased and/or reproduced for a plurality of recording media 1, 8 having different thickness of substrate and the light sources 2, 9 are employed selectively depending on the thickness of substrate of recording medium.

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 / or erasing and / or reproducing information on a plurality of recording media having different substrate thicknesses.

[0002]

2. Description of the Related Art An optical pickup device records and / or erases and / or reproduces information on a recording medium. The recording medium is an existing compact disc (CD: wavelength λ = 78.5 nm, objective lens). The substrate thickness of NA = 0.45) is 1.2 mm, and the substrate thickness of a digital video disc (DVD: λ = 650 nm, objective lens NA = 0.6) as a high density disc is 0.6 mm. .

In the optical pickup device, when information is reproduced by a single objective lens for such discs having different substrate thicknesses, the aberration caused by the substrate thickness of the discs becomes a problem. That is, in the optical pickup device, when the substrate thickness of the disc is 1.2 mm, the light beam from the light source is completely narrowed down as a light spot on the disc with the objective lens optimized for the DVD designed for the substrate thickness of 0.6 mm. However, there is a problem that it cannot be compatible with a CD.

Therefore, as a countermeasure against this problem, an aperture limiting method, a twin lens, and a bifocal lens have been proposed. The aperture limiting method is a method of obtaining a good light spot on a disc having a different substrate thickness by cutting an outer peripheral portion where an aberration of a light beam from a light source increases in an optical pickup device with an aperture member.

As the twin lens, in an optical pickup device, two objective lenses (objective lens for substrate thickness of 0.6 mm and objective lens for substrate thickness of 1.2 mm) are selected by a lens actuator according to the substrate thickness of CD and DVD. This is the method to be used. The bifocal lens is a hologram lens in which an objective lens and a hologram element are combined to form a light spot on the disc that always has two substrate thicknesses by the 0th order light and the 1st order light.

[0006]

In the above aperture limiting method,
It is necessary to put the aperture member in and out of the optical path depending on the type of disc (substrate thickness). For example, in an objective lens optimized for a substrate thickness of 0.6 mm designed for DVD, D
In the case of VD, the aperture member must be removed from the optical path, and in the case of CD, the aperture member must be inserted in the optical path.
Moreover, when the aperture member is inserted in the optical path, the aperture member must be inserted in the illumination optical system from the light source to the disc, so that high accuracy is required for its installation, and the insertion of the aperture member naturally causes Since the outer peripheral portion is cut off, the light utilization efficiency from the light source to the disc is extremely reduced and the writing power becomes insufficient, so that information can be recorded on a disc (for example, CD-R, CD-E) having a substrate thickness of 1.2 mm. It will be difficult.

Further, the twin lens described above has a problem that the movable portion of the lens actuator becomes heavy. Further, in the above bifocal lens, since the hologram element generates high-order diffracted light and two light spots are always formed on the disc, the power of the light reaching the recording surface of the disc becomes half or less of the normal power. It is difficult to record information on both a disc having a substrate thickness of 0.6 mm and a disc having a substrate thickness of 1.2 mm.

According to the present invention, it is possible to obtain a good light spot on a plurality of recording media having different substrate thicknesses with one objective lens, and to achieve compatibility with a plurality of recording media having different substrate thicknesses. It is possible to eliminate the variation in performance due to the wavelength of the parts, it is possible to combine and separate the optical path with less loss, and it is possible to correct the spherical aberration due to the difference in the substrate thickness of the recording medium, reducing the number of parts, downsizing, and reliability. It is an object of the present invention to provide an optical pickup device capable of improving the efficiency, simplifying the configuration, improving the utilization efficiency of illumination light, and performing isolation with higher accuracy.

[0009]

In order to achieve the above object, the invention according to claim 1 is a light source for irradiating a divergent light beam, and a coupling lens for converting the divergent condition of the light beam from the light source. One objective lens for condensing the light flux passing through the coupling lens on the recording surface of the recording medium, an optical element for separating the incident light on the recording medium and the reflected light from the recording medium, Recording and / or erasing and / or reproducing of information for a plurality of recording media having different substrate thicknesses as the recording medium, the light receiving element receiving the reflected light from the recording medium separated by an optical element. In the optical pickup device for performing the above, a plurality of light sources selectively used as the light source according to the substrate thickness of the recording medium are provided, and a plurality of recording media having different substrate thickness with one objective lens. Respect it is possible to obtain an excellent light spot can take the compatibility for different recording media substrate thickness.

According to a second aspect of the present invention, in the optical pickup device according to the first aspect, the plurality of light sources and the coupling lens have different distances from each other, and the objective lens and the substrate thickness are different from each other. The distances between the recording medium and the recording surface of the recording medium are different from each other, and a good light spot can be obtained for a plurality of recording media having different substrate thicknesses by one objective lens. Can be compatible with other recording media.

The invention according to claim 3 is the invention according to claim 1 or 2
In the optical pickup device described above, the wavelengths of the plurality of light sources are the same, and it is possible to eliminate variations in performance due to wavelengths of optical components.

[0012] The invention according to claim 4 is the invention according to claim 1 or 2.
In the optical pickup device described above, since the wavelengths of the plurality of light sources are different from each other, it is possible to combine and separate optical paths with little loss, and it is possible to record not only information on a recording medium but also recording.

The invention according to claim 5 relates to claims 1, 2, and 3.
Alternatively, in the optical pickup device described in 4, the plurality of coupling lenses that are selectively used according to the substrate thickness of the recording medium are provided as the coupling lens, which occurs due to the difference in the substrate thickness of the recording medium. A good light spot can be obtained by correcting spherical aberration.

The invention according to claim 6 relates to claim 1, 2, 3
Alternatively, in the optical pickup device described in the item 4, there is provided an optical element that is inserted between the light source and the coupling lens to correct the wavefront, and corrects spherical aberration generated due to a difference in substrate thickness of the recording medium. be able to.

The invention according to claim 7 relates to claims 1, 2 and
In the optical pickup device described in 3, 4, 5 or 6, the light source and the light receiving element are arranged in the same package, and the number of parts can be reduced, the size can be reduced, and the reliability can be improved.

The invention according to claim 8 is the optical pickup device according to claim 7, wherein a hologram element is used as an optical element for separating the light incident on the recording medium and the light reflected from the recording medium. Therefore, the structure can be simplified.

According to a ninth aspect of the present invention, in the optical pickup device according to the eighth aspect, a λ / 4 plate is arranged between the hologram element and the recording medium, and the hologram element is a polarization hologram element. Therefore, the utilization efficiency of illumination light can be improved.

According to a tenth aspect of the present invention, in the optical pickup device according to the eighth aspect, λ / 4 is provided in each optical path that does not overlap with each other between the hologram element and the recording medium.
Since a plate is arranged and the hologram element is a polarization hologram element, it is possible to reduce the deterioration of the performance of the λ / 4 plate due to the variation of the incident angle, and it is possible to perform highly accurate isolation.

According to an eleventh aspect of the present invention, in the optical pickup device according to the eighth, ninth or tenth aspect, the hologram element has a wavefront correction function, and the number of parts can be reduced by integrating functions. Miniaturization and cost reduction can be achieved.

The invention according to claim 12 is the invention as claimed in claims 8 and 9.
In the optical pickup device described in 10 or 11, the light source and the light receiving element are light emitting and receiving elements arranged in the same package, and the light emitting and receiving element and the hologram element are integrally bonded. Also, the relative positional relationship between the hologram elements can be kept constant, and the reliability can be further improved. Furthermore, the number of parts can be reduced, and the number of assembling steps can be reduced.

[0021]

FIG. 1 shows an embodiment of the invention according to the first and second aspects. This embodiment is an embodiment of an optical pickup device for recording and / or erasing and / or reproducing information on a plurality of recording media 1 and 8 having different substrate thicknesses. Disk 1 having a first substrate thickness as a recording medium
When is set, the disk 1 is rotationally driven by the spindle motor, and the light source 2 made of a semiconductor laser is turned on by the driving means. Then, the divergent light emitted from the light source 2 is transmitted through the beam splitter 3 and the divergent state is converted by the coupling lens 4, whereby the NA of the objective lens incident light is converted and transmitted through the beam splitter 5 to be deflected. It is deflected in the direction of the disk 1 by the mirror 6,
It is focused on the recording surface of the disc 1 by the objective lens 7.
At this time, the light source 9 made of a semiconductor laser is not driven by the driving means and is turned off.

When a disc 8 having a second substrate thickness different from the first substrate thickness is set as the recording medium instead of the disc 1, the disc 8 is rotationally driven by the spindle motor and the light source 9 is It is turned on by the driving means. Then, the divergent light emitted from the light source 9 is reflected by the beam splitter 3 and the divergent state is converted by the coupling lens 4, whereby N of the objective lens incident light is converted.
A is converted, transmitted through the beam splitter 5, and deflected in the direction of the disk 8 by the deflection mirror 6, and the objective lens 7
Is focused on the recording surface of the disk 8. At this time, the light source 2 is not driven by the driving means and is turned off.

The light beam reflected by the recording surface of the disk 1 or disk 8 follows the opposite path, passes through the objective lens 7 and the deflecting mirror 6, and is reflected by the beam splitter 5 to be recorded on the recording surface of the disk 1 or disk 8. It is guided to a detection optical system 10 for obtaining a position control signal for controlling the position of the upper light spot and a reproduction signal of information recorded on the recording surface thereof.

The detection optical system 10 obtains a position control signal and a reproduction signal by a known method. For example, FIG. 1 shows a detection optical system 10 employing the astigmatism method. In this detection optical system 10, the reflected light from the beam splitter 5 is given a converging tendency by a detection lens 11 and is caused by a cylindrical lens 12. Astigmatism is given and the 4-division light receiving element 1
3 is received. The known signal processing means obtains a focus signal by the astigmatism method, a track signal by the push-pull method, and a reproduction signal from the output signal of each divided portion of the 4-division light receiving element 13.

2 and 3 show an optical path in the case where the recording medium is the disk 1 having the first substrate thickness and the recording medium has the second substrate thickness 8 in the optical pickup device of this embodiment. Is a simplified drawing of the optical path. In this embodiment, when the recording medium is the disc 1 having the first substrate thickness and when the recording medium is the disc 8 having the second substrate thickness, the coupling lens 4 to the discs 1 and 8 are used. , L are equal, but the distance L1 from the light source 2 to the coupling lens 4 is
1 and the distance L2 from the light source 9 to the coupling lens 4
1 and the distance L12 from the coupling lens 4 to the recording surface of the disc 1 and the distance L22 from the coupling lens 4 to the recording surface of the disc 8 are different.

In this embodiment, these distances L11, L
By optimizing 12, L21 and L22, it is possible to correct the spherical aberration due to the difference in the substrate thickness of the disks 1 and 8 using the same lens. In this embodiment, when actually operating, the plurality of light sources 2 and 9 do not simultaneously emit light, and the light source that emits light is driven by the drive means depending on the substrate thickness of the discs 1 and 8 that are arbitrarily inserted and set. Is determined as one of the plurality of light sources 2 and 9.

As described above, this embodiment is an embodiment of the invention according to claim 1, and is a light source that emits a divergent light beam and a coupling lens that converts the divergent state of the light beam from this light source. 4, an objective lens 7 for condensing the light flux passing through the coupling lens 4 on the recording surface of the disks 1 and 8 as recording media, the incident light to the recording media 1 and 8, and the recording. A beam splitter 5 as an optical element for separating the reflected light from the media 1 and 8;
The position control signal for controlling the position of the light spot on the recording surface of the recording medium 1 or 8 and the information recorded on the recording surface are controlled by the reflected light from the recording medium 1 or 8 separated by the optical element 5. A light receiving element 13 for obtaining a reproduction signal,
In an optical pickup device for recording and / or erasing and / or reproducing information on a plurality of recording media 1 and 8 having different substrate thicknesses as the recording medium, the optical pickup device according to the substrate thickness of the recording media 1 and 8 is used. Since the plurality of light sources 2 and 9 selectively used as the light source are provided, it is possible to correct the spherical aberration generated by the plurality of recording media having different substrate thicknesses with one objective lens, and to perform the plurality of recordings having different substrate thicknesses. A good light spot can be obtained on the medium, and compatibility with a plurality of recording media having different substrate thicknesses can be achieved.

This embodiment is an embodiment of the invention according to claim 2, and in the optical pickup device according to claim 1, each of the plurality of light sources 2, 9 and the coupling lens 4 is provided. Since the distances L11 and L21 between them are different from each other and the distances L12 and L22 between the objective lens 7 and the recording surfaces of the plurality of recording media 1 and 8 having different substrate thicknesses are different from each other, one objective lens is used as the substrate. Spherical aberration generated by multiple recording media with different thicknesses can be corrected, a good light spot can be obtained for multiple recording media with different substrate thicknesses, and compatibility with multiple recording media with different substrate thicknesses can be achieved. Can be taken.

An embodiment of the invention according to claim 3 is the same as the embodiment of the invention according to claims 1 and 2, wherein the light sources 2 and 9 that emit light beams having the same wavelength are used. is there. As a result, in this embodiment, the optical components such as the lens and the beam splitter have the same performance with respect to the plurality of light sources 2 and 9.

As described above, this embodiment is an embodiment of the invention according to claim 3, and in the optical pickup device according to claim 1 or 2, the plurality of light sources 2 and 9 are provided.
Since the wavelengths are the same, it is possible to eliminate variations in performance due to the wavelengths of the optical components.

In an embodiment of the invention according to claim 4, in the embodiment of the invention according to claims 1 and 2, the light sources 2 and 9 that emit light beams having different wavelengths are used, and Instead of the splitter 3, one light source 2
A mirror (dichroic mirror) having a property of transmitting a light beam of a certain wavelength from the other side and reflecting a light beam of the other wavelength from the other light source 9 can be used to combine the optical paths without loss.

As described above, this embodiment is an embodiment of the invention according to claim 4, and in the optical pickup device according to claim 1 or 2, the plurality of light sources 2, 9 are provided.
Since the wavelengths are different from each other, it is possible to combine and separate optical paths with less loss, and it is possible to record not only information on the recording medium but also recording.

FIG. 4 shows an embodiment of the invention according to claim 5. In this embodiment, instead of providing the coupling lens 4 between the beam splitters 3 and 5 in the embodiment of the invention according to claims 1 and 2, between the light sources 2 and 9 and the coupling lens 4 is provided. Are provided with coupling lenses 4a and 4b, respectively, and the coupling lenses 4a and 4b are selectively used according to the substrate thickness of the recording media 1 and 8 set on the turntable.

As described above, this embodiment is an embodiment of the invention according to claim 5, and in the optical pickup device according to claim 1 or 2, the recording mediums 1 and 8 are used as the coupling lens 4. Since a plurality of coupling lenses 4a and 4b that are selectively used according to the substrate thickness are provided, it is possible to correct the spherical aberration generated due to the difference in the substrate thickness of the recording medium and improve the wavefront correction accuracy.
A good light spot can be obtained. Claim 5
The invention according to claim 3 can be applied to the embodiment of the invention according to claim 3 and the embodiment of the invention according to claim 4 in the same manner as the embodiment of the invention according to claim 5.

FIG. 5 shows an embodiment of the invention according to claim 6. In this embodiment, in one embodiment of the invention according to claims 1 and 2, the optical elements 14 and 1 for correcting the wavefront are provided in the optical paths between the light sources 2 and 9 and the beam splitter 3.
5 is inserted. In this embodiment, the light from the light source 2 or 9 has its wavefront corrected by the optical element 14 or 15, and passes through the beam splitter 3, the coupling lens 4, the beam splitter 5, the deflection mirror 6, and the objective lens 7 to record on the disk 8. The surface is irradiated so that a good light spot is formed on the recording surface of the disk 8. The optical elements 14 and 15 are parallel plates, spherical lenses,
An aspherical lens, a hologram lens or the like is used.

FIG. 6 shows another embodiment of the invention according to claim 6. In this embodiment, the optical element 15 for correcting the wavefront is inserted in the optical path between the light source 9 and the beam splitter 3 in the embodiment of the invention according to claims 1 and 2. In this embodiment, the optical element 15
The coupling lens 4 and the objective lens 7 are designed in accordance with the light flux of the optical path in which is not inserted, and the aberration is corrected by the optical element 15 only for the other optical paths. As the optical element 15, a parallel plate, a spherical lens, an aspherical lens, a hologram lens or the like is used.

As described above, the embodiment of the invention according to claim 6 is the optical pickup device according to claim 1 or 2, wherein the light sources 2 and 9 and the coupling lens 4 are provided.
Since the optical element 14, 15 or the optical element 15 which is inserted between the optical element 15 and the optical element 15 is provided between the coupling lens 4 and
Optical element 14, 15 or optical element 15 and objective lens 7
It is possible to correct the spherical aberration caused by the difference in the substrate thickness of the recording medium by the combination of.

Further, the optical elements 14 and 15 or the optical element 1
When 5 is a parallel plate, the cost can be reduced, and since the parallel plate does not need to worry about the positional deviation in the direction orthogonal to the optical axis, the assembling accuracy can be improved. . Optical element 14, 15 or optical element 1
When 5 is a spherical lens, the wavefront correction effect can be improved more than that of the parallel plate.

Further, the optical elements 14 and 15 or the optical element 1
When 5 is an aspherical lens, the wavefront correction effect can be further improved as compared with the spherical lens, and the disturbance of the wavefront can be suppressed even when the lens position is displaced. In addition, the optical elements 14 and 15 or the optical element 15
When a hologram element is used as a hologram element, theoretically, the hologram element can form an arbitrary wavefront, so that a high wavefront correction effect can be obtained, and the hologram element is excellent in mass productivity, so that cost reduction can be realized. .

The invention according to claim 6 is the same as the embodiment according to claim 6 in the embodiment according to claim 3 and the embodiment according to claim 4 described above. It can be applied similarly.

FIG. 7 shows an embodiment of the invention according to claim 7, and FIGS. 8 (a) to 8 (c) show the semiconductor laser (LD) thereof.
-Indicates a light receiving element (PD) unit and PD. In this embodiment, in the embodiment of the invention according to claims 1 and 2, an LD / PD unit 16 in which a light source 2 made of a semiconductor laser and a light receiving element are arranged in the same package, and a light source 9 made of a semiconductor laser are provided. The LD / PD unit 17 in which the light receiving elements are arranged in the same package is used.

In the LD / PD unit 16, FIG.
As shown in (a), the divergent light emitted from the semiconductor laser chip 2 constituting the power source is reflected and deflected by the compound prism 18 and emitted from the emission window 19. This LD / P
The light flux emitted from the emission window 19 of the D unit 16 is transmitted through the beam splitter 3 and the divergent state is converted by the coupling lens 4, whereby the NA of the objective lens incident light is changed.
Is converted, is deflected in the direction of the disc 1 by the deflection mirror 6, and is condensed on the recording surface of the disc 1 by the objective lens 7.

The luminous flux reflected on the recording surface of the disk 1 is
Follow the reverse path and pass through the objective lens 7, the deflection mirror 6, the coupling lens 4 and the beam splitter 3 to L
Return to the D / PD unit 16 from the exit window 19. This LD
The light flux returning from the exit window 19 to the PD unit 16 is refracted and incident into the composite prism 18, a part of which is received by the 6-division light receiving element 20 as shown in FIG. As shown in FIG.
The light is received by the three-division light receiving element 21 as shown in (c).

At this time, the 6-division light-receiving element 20 and the 3-division light-receiving element 21 have a front focus and a rear focus with respect to the focal point of the coupling lens 4, and the signal processing means (not shown) uses the so-called beam size method. Output signals a ₁ , b ₁ , c ₁ , a ₂ , b ₂ , c ₂ and 3 of each divided portion of the divided light receiving element 20.
From the output signals d, e, and f of the divided light receiving element 21, (a ₁ + c ₁ + a ₂ + c ₂ + e)-(b ₁ + b ₂ + d + f)
The focus signal is obtained by the following calculation. Furthermore, the signal processing means (not shown) is (a ₁ + b ₁ + c ₁ ) − (a ₂ + b ₂ +
The track signal is obtained by the well-known push-pull method by the calculation of c ₂ ), and the output signals a ₁ , b ₁ , c ₁ , a ₂ , b ₂ , c ₂ of each divided portion of the 6-divided light receiving element 20 and 3-divided light are received. A reproduction signal is obtained by calculating the sum of the output signals d, e, f of the respective divided portions of the element 21.

Similarly, in the LD / PD unit 17, the divergent light emitted from the semiconductor laser chip 9 constituting the power source similarly to the LD / PD unit 16 is reflected and deflected by the compound prism and emitted from the emission window. It The light flux emitted from the emission window 19 of the LD / PD unit 17 is reflected by the beam splitter 3 and the divergent state is changed by the coupling lens 4, whereby the NA of the objective lens incident light is changed and the deflection mirror 6 Is deflected in the direction of the disk 8 by the objective lens 7
Is focused on the recording surface of.

The luminous flux reflected on the recording surface of the disk 8 is
Follow the reverse path and pass through the objective lens 7, the deflection mirror 6, the coupling lens 4 and the beam splitter 3 to L
Return to the D / PD unit 17 from the exit window. This LD / P
The light flux returning from the exit window to the D unit 17 is refracted and incident on the compound prism, a part of which is received by the 6-division light receiving element, and the other part of which is reflected by the two bottom surfaces of the compound prism and is received by the 3 division The light is received by the element.

At this time, the 6-division light-receiving element and the 3-division light-receiving element have a front focus and a rear focus with respect to the focal point of the coupling lens 4, and the signal processing means uses the so-called beam size method. Output signal of each division and 3
The focus signal is obtained from the output signal of each divided portion of the divided light receiving element. Further, the signal processing means obtains a track signal from the output signal of each divided portion of the 6-divided light receiving element and the output signal of each divided portion of the 3-divided light receiving element by a well-known push-pull method to obtain each divided portion of the 6 divided light receiving element. And the output signal of each divided portion of the three-division light receiving element are calculated to obtain a reproduction signal.

As described above, this embodiment is an embodiment of the invention according to claim 7, and in the optical pickup device according to claim 1 or 2, the light source and the light receiving element are provided in the same package. Since they are arranged, the number of parts can be reduced and the size can be reduced, and it is possible to improve the reliability against changes with time. The invention according to claim 7 is an embodiment of the invention according to claim 3, an embodiment of the invention according to claim 4, an embodiment of the invention according to claim 5, and an embodiment according to claim 6 described above. The present invention according to claim 7 can be applied in the same manner as the embodiment according to the seventh aspect of the invention.

FIG. 9 shows an embodiment of the invention according to claim 8. In this embodiment, in one embodiment of the invention according to claim 7, the incident light to the disks 1 and 8 and the reflection from the disks 1 and 8 are respectively interposed between the LD / PD units 16 and 17 and the beam splitter 3. Hologram elements 22 and 23 are inserted as optical elements for separating light. LD / P
The illumination light from the D units 16 and 17 passes through the hologram elements 22 and 23, respectively, and enters the beam splitter 3, and the disk reflected light from the beam splitter 3 is reflected by the hologram elements 22 and 23, respectively. It is separated from the illumination light from and received by the light receiving elements in the LD / PD units 16 and 17.

As shown in FIG. 10, the hologram element 22 diffracts the disk reflected light from the beam splitter 3 by the three parts A, B and C to separate it from the illumination light from the LD / PD unit 16, and similarly to the hologram. The element 23 transmits the disc reflected light from the beam splitter 3 into three parts A,
The light is diffracted by B and C and separated from the illumination light from the LD / PD unit 17.

In the LD / PD unit 16, FIG.
As shown in FIGS. 1 (a) and 1 (b), the divergent light from the semiconductor laser 2 is emitted to the hologram element 22 and
The light diffracted by the two portions A and B of 2 is received by the two portions a and b of the four-division light receiving element 24. Further, the light diffracted by the other portion C of the hologram element 22 is condensed on the dividing line between the _two portions c ₁ and c ₂ of the four-division light receiving element 24.

The signal processing means (not shown) uses the well-known push-pull method to form two parts a and b of the four-division light receiving element 24.
The track signal is obtained from the output signal of the four-division light receiving element 2 by the well-known knife edge method, and the focus signal is obtained from the output signals of the _two parts c ₁ and c ₂ of the four-division light receiving element 24.
4 all parts a, b, c ₁ , c ₂ or two parts c ₁ ,
A reproduction signal is obtained by calculating the sum of output signals such as c ₂ .

In the LD / PD unit 17, the LD
Similarly to the PD unit 16, the divergent light from the semiconductor laser 9 is emitted to the hologram element 23, and the light diffracted by the two portions of the hologram element 23 is received by the two portions of the four-division light receiving element. In addition, the hologram element 2
The light diffracted by the other part of 3 is condensed on the dividing line of the two parts of the four-division light receiving element.

The signal processing means (not shown) obtains a track signal from the output signals of the two parts of the four-division light receiving element by the well-known push-pull method, and the output signal of the two parts of the four-division light receiving element by the well-known knife edge method. Then, a focus signal is obtained from the above, and a reproduction signal is obtained by calculating the sum of the output signals of all or two parts of the four-division light receiving element.

As described above, this embodiment is an embodiment of the invention according to claim 8, and in the optical pickup device according to claim 7, the incident light to the recording medium and the reflection from the recording medium. Since the hologram elements 22 and 23 are used as the optical elements for separating the light, the structure can be simplified.

FIG. 12 shows an embodiment of the invention according to claim 9. In this embodiment, in the embodiment of the invention according to claim 8, linearly polarized light is emitted from the semiconductor laser chip 2 in the LD / PD unit 16. This linearly polarized light is converted into circularly polarized light by passing through the polarization hologram element 25 and the beam splitter 3 and passing through the λ / 4 plate 26. The divergent state of this circularly polarized light is converted by the coupling lens 4 so that N
A is converted, is deflected in the direction of the disc 1 by the deflection mirror 6, and is condensed on the recording surface of the disc 1 by the objective lens 7.

The luminous flux reflected on the recording surface of the disk 1 is
By passing through the λ / 4 plate 26 through the objective lens 7, the deflecting mirror 6, the coupling lens 4 and the opposite path, the polarization direction of the linearly polarized light as the illumination light is 90.
It is converted into linearly polarized light that is rotated by a degree. This linearly polarized light passes through the beam splitter 3, is diffracted in a predetermined direction by the polarization hologram element 25, is separated from the illumination light, and returns to the LD / PD unit 16 from the exit window 19 and is received by the light receiving element. Received light.

Similarly, linearly polarized light is emitted from the semiconductor laser chip 9 in the LD / PD unit 17. This linearly polarized light is reflected by the polarization hologram element 27, transmitted through the beam splitter 3, and passed through the λ / 4 plate 26 to be converted into circularly polarized light. The NA of the incident light on the objective lens is converted by changing the divergent state of the circularly polarized light by the coupling lens 4, and the disk 8 by the deflecting mirror 6.
And is focused on the recording surface of the disk 8 by the objective lens 7.

The luminous flux reflected on the recording surface of the disk 8 is
By passing through the λ / 4 plate 26 through the objective lens 7, the deflecting mirror 6, the coupling lens 4 and the opposite path, the polarization direction of the linearly polarized light as the illumination light is 90.
It is converted into linearly polarized light that is rotated by a degree. This linearly polarized light is reflected by the beam splitter 3 and the polarization hologram element 27
Due to this, a predetermined portion is diffracted in a predetermined direction to be separated from the illumination light, and returns to the inside of the LD / PD unit 17 from the emission window and is received by the light receiving element. The λ / 4 plate 26 is installed at an appropriate position between the coupling lens 4 and the disks 1 and 8, whereby the angular variation of the light beam incident on the λ / 4 plate 26 can be reduced.

As described above, this embodiment is an embodiment of the invention according to claim 9, and in the optical pickup device according to claim 8, λ / 4 is provided between the hologram element and the recording medium. Since the plate 26 is arranged and the hologram elements are the polarization hologram elements 25 and 27, the utilization efficiency of illumination light can be improved, and information can be recorded on a recording medium by using a conventional high-power semiconductor laser as a light source. It becomes possible to do.

FIG. 13 shows an embodiment of the invention according to claim 10. In this embodiment, instead of inserting the λ / 4 plate 26 between the coupling lens 4 and the disks 1 and 8 in the embodiment of the invention according to claim 9, an LD
The λ / 4 plates 26a and 26b are inserted between the PD units 16 and 17 and the beam splitter 3, respectively, and operate in the same manner as the embodiment of the invention according to claim 9 above.

As described above, this embodiment is characterized by claim 10.
9. The optical pickup device according to claim 8, wherein the hologram elements 22 and 2 are
Since the λ / 4 plates 26a and 26b are arranged in the respective optical paths which do not overlap with each other between the recording medium 3 and the recording mediums 1 and 8 and the hologram elements 22 and 23 are the polarization hologram elements 25 and 27, variations in incident angle are caused. The performance deterioration of the λ / 4 plate due to can be reduced, and highly accurate isolation can be performed.

FIG. 14 shows a hologram element in an embodiment according to the eleventh aspect of the invention. In this embodiment,
In the embodiment of the invention according to claim 8 above, hologram elements 30 as shown in FIG. 14 are used instead of the hologram elements 22 and 23, respectively. This hologram element 30 has a wavefront correction hologram 31 on one side 30a.
Is formed, and the divided hologram 32 is formed on the other side 30b.

The illumination light from the LD / PD unit 16 has its wavefront corrected by the wavefront correction hologram 31 of the hologram element 30 and is incident on the beam splitter 3, and the disk reflected light from the beam splitter 3 is split hologram 32 of the hologram element 30. The light is separated from the illumination light by being diffracted by and is received by the light receiving element in the LD / PD unit 16.

Similarly, the illumination light from the LD / PD unit 17 has its wavefront corrected by the wavefront correction hologram 31 of the hologram element 30 and enters the beam splitter 3, and the disk reflected light from the beam splitter 3 is reflected by the hologram element 30. It is separated from the illumination light by being diffracted by the division hologram 32 and is received by the light receiving element in the LD / PD unit 17.

As described above, this embodiment is characterized by claim 11.
9. The optical pickup device according to claim 8, wherein the hologram elements 22 and 2 are
Since 3 has a wavefront correction function by the wavefront correction hologram 31, it is possible to reduce the number of parts by function integration, and it is possible to reduce the size and cost. In addition,
The invention according to claim 11 may be applied to an embodiment of the invention according to claim 9 and an embodiment of the invention according to claim 10 in the same manner as the embodiment according to the invention according to claim 8. You can

FIG. 15 shows an embodiment of the invention according to claim 12. In this embodiment, the LD / PD unit 16 and the hologram element 25 are bonded together, and the LD / PD unit 17 and the hologram element 27 are bonded together in the embodiment of the invention according to claim 9 above.

As described above, this embodiment is characterized by claim 12.
An optical pickup device according to claim 9, wherein the light source and the light receiving element are arranged in the same package.
A light emitting and receiving element consisting of 17
Since 7 and the hologram elements 25 and 27 are integrally bonded, the relative positional relationship between the light source, the light receiving element and the hologram element can be kept constant, and the reliability can be further improved. Furthermore, the number of parts can be reduced, and the number of assembling steps can be reduced.

The invention according to claim 12 is the same as the embodiment of the invention according to claim 8, the embodiment of the invention according to claim 10 or the embodiment of the invention according to claim 11 described above. It can be applied in the same manner as the embodiment of the invention according to.

[0070]

As described above, according to the invention of claim 1, the light source for irradiating the divergent light beam, the coupling lens for converting the divergent state of the light beam from the light source, and the coupling lens are provided. One objective lens for condensing the transmitted light flux on the recording surface of the recording medium, an optical element for separating the incident light to the recording medium and the reflected light from the recording medium, and the optical element And a light receiving element for receiving the reflected light from the recording medium, for recording and / or erasing and / or reproducing information on a plurality of recording media having different substrate thicknesses as the recording medium. In the above, since a plurality of light sources selectively used as the light source according to the substrate thickness of the recording medium is provided, spherical aberration generated by a plurality of recording media having different substrate thicknesses with one objective lens It is possible to obtain a good optical spot with respect to a plurality of different recording media substrate thickness can positively be, may take the compatibility for different recording media substrate thickness.

According to the invention of claim 2, in the optical pickup device of claim 1, the distances between the plurality of light sources and the coupling lens are different from each other,
Since the distances between the objective lens and the recording surfaces of the plurality of recording media having different substrate thicknesses are different from each other, it is possible to correct the spherical aberration generated by the plurality of recording media having different substrate thicknesses with one objective lens. As a result, a good light spot can be obtained for a plurality of recording media having different substrate thicknesses,
Compatibility with a plurality of recording media having different substrate thicknesses can be achieved.

According to the invention of claim 3, in the optical pickup device of claim 1 or 2, since the wavelengths of the plurality of light sources are the same, it is possible to eliminate variation in performance due to wavelengths of optical components. .

According to the invention of claim 4, in the optical pickup device according to claim 1 or 2, since the wavelengths of the plurality of light sources are different from each other, it is possible to combine and separate the optical paths with less loss, and On the other hand, not only the reproduction of information but also recording is possible.

According to the invention of claim 5, claim 1,
In the optical pickup device described in item 2, 3 or 4, since a plurality of coupling lenses that are selectively used according to the substrate thickness of the recording medium are provided as the coupling lens, the coupling lens is generated due to the difference in the substrate thickness of the recording medium. The spherical aberration can be corrected to improve the wavefront correction accuracy,
A good light spot can be obtained.

According to the invention of claim 6, according to claim 1,
In the optical pickup device described in item 2, 3 or 4, since an optical element that is inserted between the light source and the coupling lens to correct the wavefront is provided, a recording medium is formed by a combination of the coupling lens, the optical element, and the objective lens. It is possible to correct the spherical aberration caused by the difference in the substrate thickness.

According to the invention of claim 7, according to claim 1,
In the optical pickup device described in 2, 3, 4, 5 or 6, since the light source and the light receiving element are arranged in the same package, the number of parts can be reduced and downsizing can be achieved, and it is resistant to aging. The reliability can be improved.

According to the invention of claim 8, in the optical pickup device of claim 7, a hologram element is used as an optical element for separating the incident light on the recording medium and the reflected light from the recording medium. Therefore, the structure can be simplified.

According to the invention of claim 9, in the optical pickup device of claim 8, a λ / 4 plate is arranged between the hologram element and the recording medium, and the hologram element is a polarization hologram element. Therefore, it is possible to improve the utilization efficiency of the illumination light, and it is possible to record information on the recording medium by using a light source having a high output of the conventional level.

According to the invention of claim 10, claim 8
In the optical pickup device described above, a λ / 4 plate is arranged in each optical path that does not overlap with each other between the hologram element and the recording medium, and the hologram element is a polarization hologram element. Performance deterioration of the four plates can be reduced, and highly accurate isolation can be performed.

According to the invention of claim 11, in the optical pickup device of claim 8, 9 or 10,
Since the hologram element has the wavefront correction function, it is possible to reduce the number of parts by integrating the functions, and it is possible to reduce the size and cost.

According to a twelfth aspect of the invention, in the optical pickup device of the eighth, ninth, tenth or eleventh aspect, the light source and the light receiving element are light emitting and receiving elements arranged in the same package. Since the light receiving element and the hologram element are integrally bonded, the relative positional relationship between the light source, the light receiving element and the hologram element can be kept constant,
The reliability can be further improved. Furthermore, the number of parts can be reduced, and the number of assembling steps can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the invention according to claims 1 and 2.

FIG. 2 is a schematic view showing a simplified optical path when the recording medium is a disk having a first substrate thickness in the same embodiment.

FIG. 3 is a schematic view showing a simplified optical path when the recording medium is a disk having a second substrate thickness in the same embodiment.

FIG. 4 is a schematic view showing an embodiment of the invention according to claim 5;

FIG. 5 is a schematic view showing an embodiment of the invention according to claim 6;

FIG. 6 is a schematic view showing another embodiment of the invention according to claim 6;

FIG. 7 is a schematic view showing an embodiment of the invention according to claim 7;

FIG. 8 is a schematic view showing an LD / PD unit of the same embodiment and a plan view showing a PD of the LD / PD unit.

FIG. 9 is a schematic view showing an embodiment of the invention according to claim 8;

FIG. 10 is a plan view showing the hologram element of the same embodiment.

FIG. 11 is a schematic view showing an LD / PD unit of the same embodiment.

FIG. 12 is a schematic view showing an embodiment of the invention according to claim 9;

FIG. 13 is a schematic view showing an embodiment of the invention according to claim 10;

FIG. 14 is a plan view, a side view, and a back view showing a hologram element according to an embodiment of the invention as set forth in claim 11;

FIG. 15 is a schematic view showing an embodiment of the invention according to claim 12;

[Explanation of symbols]

 1, 8 disk 2, 9 semiconductor laser 3, 5 beam splitter 4, 4a, 4b coupling lens 6 deflection mirror 7 objective lens 10 detection optical system 14, 15 optical element for correcting wavefront 16, 17 LD / PD unit 18 composite Prism 20, 21, 24 Light receiving element 22, 23, 30 Hologram element 25, 27 Polarization hologram element 26 λ / 4 plate 31 Wavefront correction hologram

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshimichi Hagiya 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Takehide Ohno 1-3-6 Nakamagome, Ota-ku, Tokyo No./Ricoh Co., Ltd. (72) Inventor Takao Teramine 1-3-6 Nakamagome, Ota-ku, Tokyo / Ricoh Co., Ltd.

Claims (12)

[Claims] 1. A light source for irradiating a divergent light flux, a coupling lens for converting the divergent light flux from the light source, and a light flux passing through the coupling lens for condensing on a recording surface of a recording medium. An objective lens, an optical element for separating incident light to the recording medium and reflected light from the recording medium, and a light receiving element for receiving the reflected light from the recording medium separated by the optical element. In an optical pickup device for recording and / or erasing and / or reproducing information on a plurality of recording media having different substrate thicknesses as the recording medium, the light source is used as the light source according to the substrate thickness of the recording medium. An optical pickup device comprising a plurality of light sources selectively used. 2. The optical pickup device according to claim 1, wherein distances between the plurality of light sources and the coupling lens are different from each other, and the recording surfaces of the plurality of recording media having the objective lens and the substrate thickness different from each other. An optical pickup device characterized in that the distances between and are different from each other. 3. The optical pickup device according to claim 1, wherein the plurality of light sources have the same wavelength. 4. The optical pickup device according to claim 1, wherein the wavelengths of the plurality of light sources are different from each other. 5. The optical pickup device according to claim 1, comprising a plurality of coupling lenses that are selectively used according to the substrate thickness of the recording medium as the coupling lenses. Characteristic optical pickup device. 6. The optical pickup device according to claim 1, 2, 3 or 4, further comprising an optical element inserted between the light source and the coupling lens to correct a wavefront. apparatus. 7. The optical pickup device according to claim 1, 2, 3, 4, 5, or 6, wherein the light source and the light receiving element are arranged in the same package. 8. The optical pickup device according to claim 7, wherein a hologram element is used as an optical element for separating incident light to the recording medium and reflected light from the recording medium. . 9. The optical pickup device according to claim 8, wherein λ / 4 is provided between the hologram element and the recording medium.
An optical pickup device characterized in that a plate is arranged and the hologram element is a polarization hologram element. 10. The optical pickup device according to claim 8, wherein a λ / 4 plate is arranged in each optical path that does not overlap with each other between the hologram element and the recording medium, and the hologram element is a polarization hologram element. An optical pickup device characterized by the above. 11. The optical pickup device according to claim 8, 9 or 10, wherein the hologram element has a wavefront correction function. 12. An optical pickup device according to claim 8, 9, 10 or 11, wherein the light source and the light receiving element are light emitting and receiving elements arranged in the same package, and the light emitting and receiving element and the hologram element are integrated. An optical pickup device characterized by being adhered to.