JPH10247332A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record/reproduce optical disks having information recording surface positions 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 returning light reflected by the information recording surface toward a light receiving element. SOLUTION: A laser luminous flux 11 emitted from a laser diode 1 is intercepted in its peripheral part around an optical axis by a luminous flux intercepting part 5b, a laser luminous flux 12 passing through a circular opening part 5a is transmitted through a beam splitter 2m, becoming a roughly parallel luminous flux 13 by a collimator lens 3, then made incident on an objective lens 4 and converged on the information recording surface 8' of a conventional optical disk 8. When an opening control limit element 5 is moved to a position for not intercepting the luminous flux 11 emitted from the laser diode 1, the luminous flux 11 is transmitted through the beam splitter 2, made a roughly parallel luminous flux 13 by the collimator lens 3, then made incident on the objective lens 4 and converged on the information recording surface of a high density optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk in which the position of an information recording surface of an information medium differs in the thickness direction, and an optical pickup device for recording or reproducing information on an optical disk having 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 those at a certain distance from the optical disk reading surface. By the way, in recent years, DVD (digital versatile disk,
Digital video discs) have been proposed, and optical discs having a different information recording surface position from conventional optical discs (eg, CD: compact disc) have emerged. When recording or reproducing such a high-density optical disc and a conventional optical disc with the same optical pickup device, the light spot converging on the information recording surface of one of the optical discs contains aberrations on the other optical disc, and the information is read. I couldn't do that.

In order to solve the above problems, as described in Nikkei Mechanical 1995.8.7 no.460, a laser diode having a wavelength of about 650 nm is mounted on the same optical pickup device to support CD and DVD. Although there is an example of an optical pickup device having a dedicated objective lens as described above, however, there are many problems such as a complicated optical system, a switching mechanism for the objective lens is required, and miniaturization of the optical pickup becomes difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to use a plurality of types of optical discs in which the position of an information recording surface is different from each other in the thickness direction. It is an object of the present invention to provide an optical pickup device which can record or reproduce with the above optical pickup, can simplify the structure, and can reduce the manufacturing cost.

[0005]

An optical pickup device according to the present invention is a light pickup device for recording or reproducing a plurality of types of optical discs having different information recording surface positions in the thickness direction. Aperture limiting means for regulating the beam diameter of the emitted light beam, a collimator lens for converting the light beam emitted from the light emitting element into a parallel light beam, and an objective lens for converging the parallel light beam on an information recording surface. A light receiving element for converting a return light from the information recording surface of the optical disk to a convergent light beam emitted from the objective lens, and a light beam emitted from the light emitting element on an optical path through which the light beam passes. A reflection optical element for reflecting return light reflected or transmitted on the same optical path and reflected on the information recording surface toward the light receiving element.

In the above optical pickup device,
The aperture limiting means has a circular aperture or an elongated aperture centered on the optical axis.

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 above-described optical pickup devices, the short dimension direction of the long hole opening is set to a track scanning direction (tangential direction) when reading a signal from the information recording surface of the optical disk, and the objective lens is moved. It is provided so that the numerical aperture value is 0.3 or more.

In each of the optical pickup devices described above, the longitudinal direction of the long hole opening is set to be substantially 90 ° (in the radial direction of the optical disc) with respect to the track scanning direction. The light beam passing through the end in the dimensional direction is provided so as to pass through the effective diameter end at the time of the maximum shift of the objective lens in the tracking direction.

Further, 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 described above, the aperture limiting means is disposed between the light emitting element and the collimator lens.

Further, in each of the optical pickup devices, the aperture limiting means is provided on a mechanism which is separated from the optical path.
The light beam emitted from the light emitting element can be moved to a position where it is not regulated.

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

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, and a light emitting element and a light beam emitted from the light emitting element Aperture limiting means for regulating the beam diameter of the bundle, an objective lens for converging the beam onto the information recording surface, and returning light from the information recording surface of the disc to the convergent beam emitted from the objective lens. A light receiving element for signal conversion, and a light beam emitted from the light emitting element is reflected or transmitted on the same optical path on an optical path through which the light beam passes, and return light reflected on the information recording surface is directed to the light receiving element. And a reflection optical element for reflecting the light from the light-emitting element, the light-receiving element, and the reflection optical element.

Further, in the optical pickup device,
The aperture limiting means has a circular aperture centered on the optical axis or an elongated aperture.

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 above-described optical pickup devices, the short dimension direction of the long hole opening is set to a track scanning direction (tangential direction) when reading a signal from the information recording surface of the optical disc, and the objective lens is driven by the tangential direction. It is provided so that the numerical aperture value is 0.3 or more.

In each of the above-described optical pickup devices, the long dimension direction of the long hole opening is set to be substantially 90 ° with respect to the track scanning direction (in the radial direction of the optical disk). The light beam passing through the end in the dimensional direction is provided so as to pass 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 and the objective lens.

In each of the optical pickup devices, the aperture limiting means is moved off the optical path by a mechanism.
The light beam emitted from the light emitting element can be moved to a position where it is not regulated.

[0023]

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 conventional optical disk 8 (for example, a CD), and FIG. The state when recording / reproducing a high density optical disk 7 (for example, DVD) is shown. Figures 1 and 2
Numeral 1 denotes a laser diode 2 that emits a laser beam having a wavelength of 650 nm, a beam splitter that transmits and reflects a light beam emitted from the laser diode 1, and 3 denotes a substantially parallel light beam that emits a laser beam emitted from the laser diode 1. A collimator lens 4 for forming a bundle and an objective lens 4 having a focal length f are provided for condensing a laser beam bundle to form
Are converged on the respective information recording surfaces 7 'and 8'. 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.

In the state shown in FIG.
The light beam 11 emitted from the light beam blocking portion 5b is blocked around its optical axis at the periphery thereof, and the light beam 12 passing through the circular opening 5a is transmitted through the beam splitter 2 and substantially collimated light beam 13 by the collimator lens 3. Then, the light enters the objective lens 4 and converges on the information recording surface 8 ′ of the conventional optical disc 8.

In the state shown in FIG. 2, the aperture limiting element 5 has moved to a position where the light beam 11 emitted from the laser diode 1 is not interrupted, and the light beam 11 passes through the beam splitter 2 and is substantially collimated by the collimator lens 3. It becomes a parallel light beam 14, enters the objective lens 4, and converges on the information recording surface 7 ′ of the high-density optical disk 7.

The numerical aperture NA 'of the optical system based on the parallel light beam 13 in FIG. 1 is larger than the numerical aperture NA of the optical system based on the parallel light beam 14 in FIG. That is, the aperture limiting element 5 has the function of limiting the laser beam so that the numerical aperture of the laser beam whose light beam has been 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.

On the other hand, reference numeral 2 denotes a beam splitter for reflecting the return light from the information recording surfaces 7 'and 8' of the optical disks 7 and 8 with respect to the convergent light emitted from the objective lens 4 toward the photodiode 6. The photodiode 6 converts 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 the objective lens 4 tracks the information recording surface 8 'of the conventional optical disk 8 when recording and reproducing the conventional optical disk 8 (for example, a CD). Direction (radial direction of optical disk)
(Indicated by an arrow in the figure) indicates a state in which the aperture limiting element 5 moves in synchronization with the objective lens 4 (an arrow in the figure). During tracking, the objective lens 4 moves from the optical axis shown in FIG. 1 as shown by the arrow in FIG. Due to this movement, a substantially parallel ray bundle 18 with respect to the lens center of the objective lens 4
The aperture limiting element 5 moves in the direction of the arrow in the figure so that the incident position of the aperture beam does not change from the incident position of the parallel light beam 13 in FIG. 5 also moves continuously.

FIG. 4 shows an optical pickup device according to a second embodiment of the present invention. In the present embodiment, the beam splitter 2 in the first embodiment shown in FIGS.
5 is replaced. With such a configuration, it is possible to reduce the number of components, reduce the weight, and thereby reduce the cost of the optical pickup device.

FIG. 5 shows an optical pickup device according to a third embodiment of the present invention. In the present embodiment, a laser diode module 16 in which the beam splitter 2 is omitted and the laser diode 1 and the photodiode 6 are integrated together with the hologram element in the optical system constituted by the first embodiment shown in FIGS. It has been replaced. A hologram element (not shown) in the laser diode module 16 transmits the laser beam bundle 17 from the laser diode toward the optical disc, and diffracts the reflected light from the information recording surface of the optical disc toward the photodiode. For details on the laser diode module, see Japanese Patent Application Laid-Open No. H08-111039.
No. 6,086,045.

With the configuration as in the third embodiment, the assembly can be simplified, the number of parts 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 example 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 such a configuration, the number of parts 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. 1 to 6 is 650 nm.
Is used, but the present invention is not limited to this as long as it is within the range defined by the DVD standard.

Although the opening of the aperture limiting element 5 in the first to fourth embodiments is a circular opening 5a, the long dimension direction is arranged in the tracking direction, and the laser beam bundle is arranged in the short dimension direction. An elliptical opening that limits the numerical aperture to 0.3 or more may be used. 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 in FIG.
In the case of each of the conventional 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 taking in and out the aperture limiting element 5 can be further simplified as compared with the first to fourth embodiments.

[0035]

The optical pickup device of the present invention can be manufactured with a simple structure, and the position of the information recording surface differs in the thickness direction.
A conventional optical disc such as D and a high-density optical disc such as DVD can be recorded or reproduced by one optical pickup device.

Further, since the optical pickup device of the present invention can be constituted by 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 the 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 pick-up device according to the first embodiment of the present invention.

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

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

FIG. 4 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 the operation of an optical pickup device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser diode (650 nm) 2 Beam splitter 3 Collimator lens 4 Objective lens 5 Aperture limiting element 5a Circular aperture 5b Light beam shielding part 6 Photodiode 7 High-density optical disk (DVD etc.) 7 'Information recording of high-density optical disk (DVD etc.) Surface 8 Conventional optical disk (CD, etc.) 8 ′ Information recording surface of conventional optical disk (CD, etc.) 11 Laser beam bundle (during reproduction of high-density optical disk) 12 Laser beam bundle (during conventional optical disk reproduction) 13 (conventional Substantially parallel ray bundle (during optical disk reproduction) 14 Substantially parallel ray bundle (during high-density optical disk reproduction) 15 Half mirror 16 Laser diode module 17 Ray bundle 18 Substantially parallel ray bundle

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[Procedure amendment]

[Submission date] May 20, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is an optical path diagram for explaining the 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 pick-up device according to the first embodiment of the present invention.

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

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

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

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

[Description of Signs] 1 Laser diode (650 nm) 2 Beam splitter 3 Collimator lens 4 Objective lens 5 Aperture limiting element 5a Circular aperture 5b Light flux shielding part 6 Photodiode 7 High density optical disc (DVD etc.) 7 ′ High density optical disc (DVD) 8) Information recording surface of conventional optical disk (CD, etc.) 8 'Information recording surface of conventional optical disk (CD, etc.) 11 Laser beam bundle (for reproduction of high-density optical disk) 12 Laser beam (for reproduction of conventional optical disk) Bundle 13 Substantially parallel ray bundle (during conventional optical disc reproduction) 14 Substantially parallel ray bundle (during high-density optical disc reproduction) 15 Half mirror 16 Laser diode module 17 Ray bundle 18 Almost parallel ray bundle

Claims (18)

[Claims] 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 a thickness direction, wherein a light emitting element and a light beam diameter of a light beam emitted from the light emitting element are regulated. An aperture limiting unit, a collimator lens that converts the light beam emitted from the light emitting element into a parallel light beam, an objective lens that converges the parallel light beam on an information recording surface, and a convergent light beam that is emitted from the objective lens. A light receiving element for converting a return light from the information recording surface of the optical disc into a signal, and a light beam emitted from the light emitting element on an optical path through which the light beam passes is reflected or transmitted on the same optical path, and the information recording surface An optical pickup device, comprising: a reflection optical element for reflecting the return light reflected by the device toward the light receiving element. 2. The optical pickup device according to claim 1, wherein said aperture limiting means has a circular opening or an elongated hole opening centered on an optical axis. 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. A short dimension direction of the elongated hole opening is set in a track scanning direction (tangential direction) at the time of reading a signal from the information recording surface of the optical disk, and a value of a numerical aperture of the objective lens is 0.3. The optical pickup device according to claim 1, wherein the optical pickup device is provided as described above. 5. A long dimension direction of said elongated hole opening is set to be substantially 90 ° with respect to said track scanning direction (in a radial direction of said optical disk), and a light beam passing through an end of said long dimension direction is formed. 5. The optical pickup device according to claim 1, wherein the optical pickup device is provided so as to pass through an effective diameter end of the objective lens at the time of a maximum shift in a tracking direction. 6. An optical pickup device according to claim 1, wherein said aperture limiting means moves in synchronization with a movement of said objective lens in a tracking direction. 7. The apparatus according to claim 1, wherein said aperture limiting means is disposed between said light emitting element and said reflection optical element.
Item 7. An optical pickup device according to item 6. 8. The optical pickup device according to claim 1, wherein said aperture limiting means is disposed between said light emitting element and said collimator lens. 9. The apparatus according to claim 1, wherein said aperture restricting means can be moved to a position where the light beam emitted from said light emitting element is not restricted by a mechanism deviating from the optical path.
9. The optical pickup device described in any one of items 1 to 8. 10. The light-emitting element and the light-receiving element,
10. The optical pickup device according to claim 1, wherein an integrated module in which a light emitting element and a light receiving element are integrated is used. 11. An optical pickup device for recording or reproducing a plurality of types of optical disks in which the position of an information recording surface differs in a thickness direction, wherein a light emitting element and a light beam diameter of a light beam emitted from the light emitting element are regulated. An aperture limiting unit, an objective lens for converging a light beam on the information recording surface, and a light receiving element for converting a return light from the information recording surface of the disc to a convergent light beam emitted from the objective lens, A reflective optical element that reflects or transmits the light beam emitted from the light emitting element on the same optical path on the optical path through which the light beam passes, and reflects the return light reflected on the information recording surface toward the light receiving element. An optical pickup device comprising: an integrated module including the light emitting element, the light receiving element, and the reflection optical element. 12. The optical pickup device according to claim 11, wherein said aperture limiting means has a circular aperture centered on an optical axis or an elongated aperture. 13. The optical pickup device according to claim 11, wherein the circular aperture is provided so that the numerical aperture of the objective lens is 0.3 or more. 14. The apparatus according to claim 1, wherein a short dimension direction of said elongated hole opening is set in a track scanning direction (tangential direction) when a signal is read from said information recording surface of said optical disc, and a numerical aperture value of said objective lens is 0.3. 13. The optical pickup device according to claim 11, wherein the optical pickup device is provided as described above. 15. A long dimension direction of the long hole opening is set to be substantially 90 ° with respect to the track scanning direction (in a radial direction of the optical disc), and a light beam passing through an end in the long dimension direction is formed. 15. The optical pickup device according to claim 11, wherein the optical pickup device is provided so as to pass through an effective diameter end of the objective lens at the time of a maximum shift in a tracking direction. 16. An optical pickup device according to claim 11, wherein said aperture limiting means moves in synchronization with a movement of said objective lens in a tracking direction. 17. The apparatus according to claim 1, wherein said aperture limiting means is disposed between said light emitting element and said objective lens.
The optical pickup device described in any one of 1 to 16. 18. An optical pickup according to claim 11, wherein said aperture restricting means can be moved to a position where the light beam emitted from said light emitting element is not restricted by a mechanism deviating from the optical path. apparatus.