JPH10247333A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record/reproduce optical disks having information recording surfaces different in the thickness direction with the same optical pickup, by reflecting or passing, on the same optical path, luminous flux from a light emitting element on the optical path, on which the luminous flux passes, and reflecting a returning light reflected by an information recording surface toward the light emitting element. SOLUTION: A laser luminous flux 11 emitted from a laser diode 1 is reflected by a polarizing beam splitter 2, made a roughly parallel luminous flux by a collimator lens 3, made incident on an objective lens 4 and converged on the information recording surface 7' of a high density optical disk 7. A luminous flux emitted from a laser diode 1' is intercepted in its peripheral part by a luminous flux intercepting part 5b, made a luminous flux to pass through a circular opening 5a, transmitted through the polarizing beam splitter 2, similarly made incident on the objective lens 4 and then converged on the information recording surface of a conventional optical disk. On the other hand, a returning light from the optical disk 7 is reflected toward a photodiode 6 by a half mirror prism 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc in which the position of an information recording surface of an information recording medium is different in a thickness direction, and an optical pickup device for recording or reproducing information on an optical disc having a wavelength dependency.

[0002]

2. Description of the Related Art A conventional optical pickup device used for an optical disk device uses a single laser diode, and an optical system is also designed for a specific optical disk. The recording surface was limited to a certain distance from the optical disk surface. In recent years, DVDs (digital versatile disks, digital video disks), which are high-density optical disks, have been proposed, and the position of the information recording surface is different from that of conventional optical disks (eg, CD: compact disk, CD-R). Optical disks have appeared. When such a high-density optical disk and a conventional optical disk are to be recorded or reproduced by a conventional optical pickup device, a light spot converged on the information recording surface of one of the optical disks contains aberrations on the other optical disk, and the information is read. I couldn't do that.

In order to solve the above problems, Nikkei Mechanical 1995.8.7 no. As described in 460, a wavelength of 650 nm is set on the same optical pickup device.
There is an example of an optical pickup device equipped with a laser diode of about m and a dedicated objective lens corresponding to CD and DVD, but not only the optical system becomes complicated, but also a wavelength of about 650 nm corresponding to the optical system. Since a laser diode is used, there is a problem that, among the conventional optical disks, recording / reproduction of an optical disk having a wavelength dependency, for example, a CD-R cannot be performed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an optical disc in which the position of an information recording surface differs from one another in a thickness direction and a wavelength-dependent optical disc. It is possible to record or reproduce multiple types of optical disks such as an optical disk with the same optical pickup,
An object of the present invention is to provide an optical pickup device whose structure can be simplified and the manufacturing cost of the optical pickup device can be reduced.

[0005]

An optical pickup device according to the present invention is an optical pickup device for recording or reproducing a plurality of types of optical disks having different positions of an information recording surface in a thickness direction, comprising two or more light emitting elements; Aperture limiting means for regulating a beam diameter of a light beam emitted from at least one of the light emitting elements, a light receiving element for converting a return light from the information recording surface of the optical disc into a signal, and the light emitting element A collimator lens that converts the light beam emitted from the light beam into a substantially parallel light beam; an objective lens that converges the substantially parallel light beam onto the information recording surface; A synthetic optical element that reflects or transmits on the same optical path, and a reflective optical element that reflects the return light reflected on the information recording surface toward the light receiving element,
It is provided with.

In the above optical pickup device,
The aperture limiting means is arranged in a circular aperture centered on an optical axis or in a long dimension direction in a tracking direction (radial direction of the optical disk) for causing a convergent light beam of the objective lens to follow a pit on the information recording surface. It has a configuration having an elongated hole opening.

In each of the optical pickup devices, the circular aperture has a numerical aperture of the objective lens of 0.1 mm.
It is provided so as to be three or more.

In each of the optical pickup devices,
The short hole direction of the long hole is arranged such that the numerical aperture of the objective lens becomes 0.3 or more.

In each of the optical pickup devices and the optical pickup device, a light beam that has passed through the end of the long hole in the longitudinal direction passes through the effective diameter end when the objective lens is shifted to the maximum in the tracking direction. It is configured as follows.

In each of the optical pickup devices, the aperture limiting means is configured to move in synchronization with the movement of the objective lens in the tracking direction.

In each of the optical pickup devices, the aperture limiting means is arranged between the light emitting element and the reflective optical element.

In each of the optical pickup devices, the combining optical element is a polarization beam splitter.

Further, in each of the optical pickup devices, instead of the light emitting element and the light receiving element, an integrated module in which the light emitting element and the light receiving element are integrated is used.

Further, according to the optical pickup device of the present invention, there is provided an optical pickup device for recording or reproducing a plurality of types of optical disks in which the position of an information recording surface is different in a thickness direction, wherein two or more light emitting elements having different emission wavelengths; Among the light-emitting elements, an aperture limiting unit that regulates a light beam diameter of a light beam emitted from a light-emitting element having a long emission wavelength, and a light-receiving element for converting a return light from the information recording surface of the optical disc into a signal. A collimator lens that converts the light beam emitted from the light emitting element into a substantially parallel light beam, an objective lens that converges the substantially parallel light beam on the signal recording surface, and a light beam emitted from the light emitting element on an optical path through which the light beam passes. A combined optical element that reflects or transmits the light beam on the same optical path, and a reflective optical element that reflects return light reflected on the information recording surface toward the light receiving element It is those with a.

In the above optical pickup device,
Among the at least two light emitting elements having different emission wavelengths,
The emission wavelength of at least one light emitting element is less than 680 nm, and the emission wavelength of at least another light emitting element is 68 nm.
The thickness is set to be 0 nm or more.

In each of the optical pickup devices, the aperture limiting means may have a circular aperture centered on the optical axis, or a tracking direction (the optical axis) for causing a convergent light beam of the objective lens to follow a pit on the signal recording surface. It has a long hole opening in which the long dimension direction is arranged (substantially radial direction of the optical disc).

In each of the optical pickup devices, the circular aperture is set to a numerical aperture of the objective lens of 0.1.
It is provided so as to be three or more.

In each of the optical pickup devices,
The short hole direction of the long hole is arranged such that the numerical aperture of the objective lens is 0.3 or more.

In each of the optical pickup devices,
The light beam passing through the long dimension end of the long hole opening passes through the effective diameter end at the time of the maximum shift of the objective lens in the tracking direction.

In each of the optical pickup devices, the aperture limiting means is configured to move in synchronization with the movement of the objective lens in the tracking direction.

In each of the optical pickup devices, the aperture limiting means is arranged between the light emitting element having a wavelength of 680 nm or more and the reflective optical element.

Further, in each of the optical pickup devices, the combining optical element is a polarizing beam splitter or a dichroic coding beam splitter.

Further, in each of the optical pickup devices, a light-emitting element and a light-receiving element are integrated, and an integrated module is used instead of the light-emitting element and the light-receiving element.

[0024]

Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are optical path diagrams showing an optical pickup device according to a first embodiment of the present invention. FIG. 1 shows a state when recording / reproducing a high-density optical disk 7 (for example, DVD), and FIG. Conventional optical disk 8 (for example, CD,
(CD-R) when recording / reproducing.
1 and 2, reference numeral 1 denotes a laser diode for emitting a laser beam bundle 11 having a wavelength of 650 nm;
A laser diode for emitting a laser beam bundle 12 'of 0 nm, a dichroic beam splitter 2 for reflecting or transmitting the laser beam bundles 11 and 12, respectively, and a substantially parallel laser beam bundle 11 and 12 for passing through the dichroic beam splitter 2 A collimator lens 4 for forming the light beams 13 and 14 is an objective lens having a focal length f, and condenses the laser light beams 13 and 14 and converges them on the information recording surfaces 7 'and 8' of the optical disks 7 and 8, respectively. Reference numeral 5 denotes an aperture limiting element, which is constituted by a light beam blocking unit 5b having a circular opening 5a around the optical axis.

As shown in FIG. 1, a light beam 11 emitted from a laser diode 1 is reflected by a dichroic beam splitter 2 having characteristics as shown in FIG. 4 and converge on the information recording surface 7 ′ of the high-density optical disk 7.

As shown in FIG. 2, the laser diode 1 '
Beam 12 'emitted from the light source is blocked around its optical axis by a light beam blocking unit 5b, becomes a laser beam bundle 12 passing through a circular opening 5a, passes through a dichroic beam splitter 2, and is substantially parallel by a collimator lens 3. Ray bundle 14
Then, the light enters the objective lens 4 and converges on the information recording surface 8 ′ of the conventional optical disk 8.

The numerical aperture NA 'of the optical system using the parallel light beam 14 shown in FIG. 2 is NA>NA' with respect to the numerical aperture NA of the optical system using the parallel light beam 13 shown in FIG. That is, the aperture limiting element 5 has an action of limiting the laser beam so that the numerical aperture of the laser beam 12 whose light beam is blocked is NA ′. NA ′ is set to be 0.3 or more, and is determined so as to obtain a sufficient resolution for recording and reproduction of the conventional optical disk 8 in the present embodiment. Further, among the conventional optical disks, an optical disk having a wavelength dependency, for example, a CD-R, can record / reproduce at a sufficient signal level because the wavelength of the laser diode 1 'is 780 nm.

On the other hand, the half-mirror prisms 15 and 15 serve to prevent the convergent light emitted from the objective
And 8 are reflected toward the photodiodes 6 and 6 ', respectively, from the information recording surfaces 7' and 8 '. The photodiodes 6 and 6 'convert the laser beam bundle of the return light into an electric signal. The information recording surface 7 'of the high-density optical disk 7 is located substantially at the center in the thickness direction of the optical disk, and is different from the information recording surface 8' of the conventional optical disk 8.

FIG. 3 shows a first embodiment of the present invention, in which a conventional optical disk 8 (for example, a CD or CD-R) is recorded / reproduced when the objective lens 4 is moved in the tracking direction. The state where the element 5 has moved in synchronization with the objective lens 4 is shown. When the objective lens 4 scans so as to follow the spiral pit row or track constituting the information recording surface, the objective lens has moved from the position of the optical axis shown in FIG. 1 in the direction of the arrow in FIG. In case,
The aperture limiting element 5 moves so that the incident position of the parallel light beam 18 with respect to the lens center of the objective lens 4 due to this movement does not change from the incident position of the parallel light beam 14 in FIG. Aperture limiting element 5
Also make continuous movements.

FIG. 4 shows an optical pickup device according to a second embodiment of the present invention. In this embodiment, the dichroic beam splitter 2 in the first embodiment shown in FIGS. 1, 2 and 3 is replaced by a dichroic coating mirror 19, and the half mirror prism 15 is replaced by a half mirror 17 respectively. With this configuration, it is possible to reduce the number of components, reduce the weight, and further reduce the cost of the optical pickup device.

In the above description, the coating applied to the surface of the dichroic coating mirror 19 is a dichroic coating. However, the coating is not limited to this, and any coating having the same characteristics may be used. Further, the present embodiment can be realized by using a half mirror instead of the dichroic coating, or by replacing it with a deflection beam splitter.

FIG. 5 shows an optical pickup device according to a third embodiment of the present invention. This embodiment is a laser in which the half mirror 17 is eliminated and the laser diodes 1, 1 'and the photodiodes 6, 6' are integrated together with the hologram element in the optical system constituted by the second embodiment shown in FIG. It is replaced by diode modules 20, 20 '.

Laser diode modules 20, 20 '
A hologram element (not shown) inside transmits the laser beam bundles 11 and 12 from the laser diode toward the optical disk, and diffracts the reflected light from the information recording surface of the optical disk toward the photodiode. Details of the laser diode module are disclosed in JP-A-8-1111039.

With the configuration as in the third embodiment, the assembly can be simplified, the number of components can be reduced, the adjustment time can be shortened, and the cost of the optical pickup device can be reduced accordingly.

FIG. 6 shows an optical pickup device according to a fourth embodiment of the present invention. This embodiment is an embodiment in which the collimator lens 3 in the third embodiment shown in FIG. 5 is removed and the optical system is a finite system. With this configuration, the number of components can be further reduced as compared with the third embodiment, and the optical pickup device can be further downsized.

The wavelength of the laser beam in the first to fourth embodiments shown in FIGS.
nm, but is not limited to this as long as it is within the range defined by the DVD standard. For example, 635 nm or 680 nm
m.

Although the opening of the aperture limiting element 5 in the first to fourth embodiments is a circular opening 5a,
The long dimension direction may be arranged in the tracking direction, and the short dimension direction may be an elliptical opening that limits the numerical aperture of the laser beam to 0.3 or more. In this case, since the shift of the optical axis due to the movement of the objective lens 4 during tracking can be absorbed in the long dimension direction, there is no need to synchronize the aperture limiting element 5 with the objective lens 4 as described with reference to FIG. In each case of the optical disk 8 and the high-density optical disk 7, it is only necessary to put the aperture limiting element 5 in and out. Therefore, there is an effect that the mechanism for inserting and removing the aperture limiting element 5 can be further simplified as compared with the first to fourth examples.

[0038]

The optical pickup device according to the present invention can be manufactured with a simple configuration, and can be used for a conventional optical disk such as a CD and a high-density optical disk such as a DVD in which the position of the information recording surface differs in the thickness direction. Recording or reproduction can be performed by the optical pickup device. Also, recording or reproduction of an optical disk having a wavelength dependency, for example, a CD-R, is possible.

Even in an optical pickup device having two optical systems such as a CD system and a DVD system, each optical system can be adjusted independently in the assembling process, so that the assembling accuracy is improved and the assembling time is shortened. And the accompanying cost reduction.

Further, the optical pickup device according to the present invention comprises:
Since it can be composed of inexpensive parts, the manufacturing cost of the optical pickup device can be reduced.

[Brief description of the drawings]

FIG. 1 is an optical path diagram for explaining an operation of an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is an optical path diagram for explaining the operation of the optical pickup device according to the first embodiment of the present invention.

FIG. 3 is an optical path diagram for explaining an operation of the optical pickup device according to the first embodiment of the present invention.

FIG. 4 is an optical path diagram for explaining an operation of the optical pickup device according to the second embodiment of the present invention.

FIG. 5 is an optical path diagram for explaining the operation of an optical pickup device according to a third embodiment of the present invention.

FIG. 6 is an optical path diagram for explaining an operation of an optical pickup device according to a fourth embodiment of the present invention.

FIG. 7 is a graph showing optical characteristics of a dichroic beam splitter used in an example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 laser diode (650 nm) 1 'laser diode (780 nm) 2 polarizing beam splitter 3 collimator lens 4 objective lens 5 aperture limiting element 5a circular aperture 5b light beam shielding section 6 7) High-density optical disk (DVD, etc.) 7 'Information recording surface of high-density optical disk (DVD, etc.) 8' Conventional optical disk (CD, etc.) 8 'Information recording of conventional optical disk (CD, etc.) Surface 11 Laser beam bundle (during reproduction of high-density optical disk) 12 Laser beam bundle (during reproduction of conventional optical disk) 13 Substantially parallel light beam (during reproduction of high-density optical disk) 14 Substantially parallel light beam (during reproduction of conventional optical disk) Bundle 15 Half mirror prism 17 Half mirror 18 Substantially parallel ray bundle 19 Lee black dichroic coating mirror 20 the laser diode module (650 nm) 20' laser diode module (780 nm)

Claims (19)

[Claims] 1. An optical pickup device for recording or reproducing a plurality of types of optical discs in which the position of an information recording surface differs in the thickness direction, two or more light emitting elements and at least one of the light emitting elements. Aperture limiting means for regulating the beam diameter of the light beam, a light receiving element for converting the return light from the information recording surface of the optical disc to a signal, and a light beam emitted from the light emitting element as a substantially parallel light beam. A collimating lens, an objective lens for converging the substantially parallel light beam on the information recording surface, and a combining optical element for reflecting or transmitting the light beam emitted from the light emitting element on the same light path on the light path through which the light beam passes An optical pickup device, comprising: a reflection optical element configured to reflect return light reflected by the information recording surface toward the light receiving element. 2. The apparatus according to claim 1, wherein the aperture limiting means is a circular aperture centered on an optical axis or a tracking direction (radial direction of the optical disk) for causing a convergent light beam of the objective lens to follow a pit on the information recording surface. 2. The optical pickup device according to claim 1, wherein the optical pickup device has an elongated hole opening arranged in a dimensional direction. 3. The optical pickup device according to claim 1, wherein the circular aperture is provided so that the numerical aperture of the objective lens is 0.3 or more. 4. The optical pickup according to claim 1, wherein a numerical value of the numerical aperture of the objective lens is 0.3 or more in a short dimension direction of the long hole opening. apparatus. 5. A light beam which has passed through an end in the long dimension direction of the elongated hole opening passes through an effective diameter end at the time of a maximum shift of the objective lens in a tracking direction. 4. The optical pickup device described in 4. 6. The optical pickup device according to claim 1, wherein the aperture limiter moves in synchronization with a movement of the objective lens in a tracking direction. 7. The optical pickup device according to claim 1, wherein said aperture limiting means is arranged between said light emitting element and said reflection optical element. 8. The optical pickup device according to claim 1, wherein the combining optical element is a polarization beam splitter. 9. Instead of the light emitting element and the light receiving element,
9. The optical pickup device according to claim 1, wherein a light-emitting element and a light-receiving element are integrated into an integrated module. 10. An optical pickup device for recording or reproducing a plurality of types of optical discs having different information recording surface positions in a thickness direction, wherein two or more light emitting elements having different emission wavelengths, and an emission wavelength among the light emitting elements. Aperture restricting means for regulating the beam diameter of the light beam emitted from the long light emitting element, a light receiving element for converting the return light from the information recording surface of the optical disc into a signal, and the light emitted from the light emitting element. A collimator lens that converts the light beam into a substantially parallel light beam; an objective lens that converges the substantially parallel light beam onto the signal recording surface; and a light beam emitted from the light emitting element on the light path through which the light beam passes. An optical pick-up, comprising: a synthetic optical element that reflects or transmits light through the optical recording medium; and a reflective optical element that reflects return light reflected by the information recording surface toward the light receiving element. -Up apparatus. 11. The light emitting device, wherein at least one of the at least two light emitting elements having different emission wavelengths has an emission wavelength of less than 680 nm, and at least another light emitting element has an emission wavelength of 680 nm or more. Item 11. An optical pickup device according to item 10. 12. The aperture limiting means in a circular aperture centered on an optical axis or in a tracking direction (substantially radial direction of the optical disk) for causing a convergent light beam of the objective lens to follow a pit on the signal recording surface. 11. An elongated hole opening arranged in a longitudinal direction.
Or the optical pickup device described in 11. 13. The optical pickup device according to claim 10, wherein the circular aperture is provided so that the numerical aperture of the objective lens is 0.3 or more. 14. The optical pickup device according to claim 10, wherein a numerical value of the numerical aperture of the objective lens is 0.3 or more in a short dimension direction of the long hole opening. . 15. The optical system according to claim 10, wherein the light beam passing through the long-dimension end of the elongated hole passes through the effective diameter end at the time of the maximum shift of the objective lens in the tracking direction. 15. The optical pickup device described in 14. 16. The optical pickup device according to claim 10, wherein said aperture limiting means moves in synchronization with a movement of said objective lens in a tracking direction. 17. The optical pickup device according to claim 10, wherein said aperture limiting means is disposed between said light emitting element having a wavelength of 680 nm or more and said reflection optical element. 18. The optical pickup device according to claim 10, wherein said combining optical element is a polarization beam splitter or a dichroic coding beam splitter. 19. The optical pickup device according to claim 10, wherein a light-emitting element and a light-receiving element are integrated in a module instead of the light-emitting element and the light-receiving element. .