JP2003123306A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device in which the RIM intensity required for laser light having respective wavelengths and made incident on an objective lens is satisfied, and the light intensity loss for any of the laser light is avoided. SOLUTION: A difference in wide and narrow widths is given also to the far field pattern (FFP) of laser light sources corresponding to the difference in the effective diameters of objective lenses necessary for a laser light source on a short wavelength side and for a laser light source on a long wavelength side, thus the RIM intensity required for the laser light on the long wavelength side is optimized to substantially satisfy the RIM intensity required for the laser light on the long wavelength side of itself in the case where the RIM intensity necessary for the laser light on the short wavelength side is assured by the effective diameter of the objective lens on the side of the short wavelength. As a result, the light quantity loss of the laser light on the long wavelength side is suppressed and the light utility efficiency is improved.

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 including a laser light source that emits laser light having different wavelengths.

[0002]

2. Description of the Related Art Generally, an optical pickup device of this kind generally records or reproduces information on an optical disc by converging laser light emitted from a laser light source onto the optical disc by an objective lens.
At this time, the reflected light from the optical disk again passes through the objective lens and reversely traces the optical axis of the illumination system, is separated from the illumination light by the polarization beam splitter, etc., and goes to the detection system, where the reproduction signal, tracking / focusing servo signal, etc. Will be obtained.

By the way, in recent years, a DVD type optical disk having a larger capacity than the conventional general CD type optical disk has come into practical use, and for the time being, the CD type and the DVD type will coexist. In this case, for example, a CD-R, which is a write-once type optical disc, uses laser light in the infrared region near 780 nm, but since the recording layer is a dye, the wavelength dependence of the recording characteristics is large, and the wavelength region of 635 nm or 650 nm in the red region is large. The wavelength used is different from that of the DVD system that uses laser light as the wavelength used. This allows, for example, CD-R (CD system) and D
An optical pickup device having two light source wavelengths is required to commonly reproduce or record two types of optical discs of VD type by one optical disc drive.

An example of a schematic configuration of a conventional general optical pickup device in which the CD system and the DVD system are shared in this way will be described with reference to FIG. For example, a semiconductor laser 1 as a laser light source for a CD system that emits laser light having a wavelength of 780 nm, a collimator lens 2 that converts the laser light emitted from the semiconductor laser 1 into parallel light, and a collimator lens 2 An objective lens 4 for converging and irradiating the optical disk 3 with light is provided. The reflected light from the optical disk 3 passes through the objective lens 4 again, and then is reflected by the beam splitter (not shown) to be received by the light receiving element (not shown) through the detection lens (not shown).
It is used for detecting a reproduction signal, a servo signal, and the like.

On the other hand, unlike the semiconductor laser 1, for example, a semiconductor laser 5 is provided as a laser light source for DVD system which emits a laser beam having a wavelength of 650 nm.

Since the laser light from the semiconductor laser 5 also shares the objective lens 4, a two-wavelength combining prism 6 as a light combining means for combining the optical paths is provided. The two-wavelength combining prism 6 is, for example, 780n
This is a prism provided with a dichroic mirror having wavelength selectivity that allows laser light in the infrared range such as m to be transmitted and reflects laser light in the red range such as 650 nm. As a result, the emission optical path on the side of the semiconductor laser 1 and the emission optical path on the side of the semiconductor laser 5 arranged orthogonal to each other are combined by the two-wavelength combining prism 6 as the same optical path toward the objective lens 4, and the objective lens 4 Sharing is possible.
The collimator lens 2 is also disposed between the objective lens 4 and the two-wavelength combining prism 6 and is commonly used for the two-wavelength laser light.

[0007]

As described above, in an optical pickup device having two laser light sources, generally,
The RIM intensity (ratio of the light intensity at the lens outer edge portion to the light intensity at the lens central portion) and the numerical aperture NA of the objective lens 4 required for the two laser light sources are different, and the respective laser beams cannot be effectively utilized. .

That is, for long wavelength 780 nm, CD recording / reproduction,
The short wavelength of 650 nm is generally used for DVD recording and reproduction, and the RIM for CD is 15% to 20% NA 0.5.
On the other hand, in the case of DVD, which is significantly different from 30% NA of 0.65, conventionally, in order to find a common solution, it is general to design an optical system on the short-wavelength laser light source side so that the light on the long-wavelength laser light source side is designed. The utilization efficiency is significantly reduced, which is a major problem in developing an optical pickup device.

This point will be further described. As described above, in the case of the optical pickup device configuration as shown in FIG. 8 in which the objective lens 4 is shared and the laser beam to the objective lens 4 is converted into parallel light by the shared collimator lens 2, as shown in FIG. Since it is necessary to make the numerical aperture NA on the short wavelength laser light side higher than the numerical aperture NA on the long wavelength laser light side, the effective diameter of the objective lens 4 on the long wavelength laser light side is limited by using the wavelength selection filter 7 or the like. It is common to do. In FIG. 9, 8 is a lens holder.

Here, the RIM intensity of the laser light incident on the objective lens is, as shown in FIG. 10, a far field pattern (FFP = Far Field Pat) of the laser light source.
tern), it is defined by the effective diameter of the objective lens (OL effective diameter).

As a result, as shown in FIG. 8, when the collimating lens 2 for collimating two laser beams into parallel light is shared, and when the FFPs of the two semiconductor lasers 1 and 5 are almost the same, the light enters the objective lens 4. The intensity distribution of the parallel light is as shown in FIG. In this case, as shown in FIG. 11, the objective lens 4 has two laser wavelengths (short wavelength and long wavelength).
Since the effective diameter of the
When trying to secure the IM intensity with the OL effective diameter on the short wavelength side, the RIM intensity of the long wavelength side laser light becomes a value considerably higher than the RIM intensity required for the long wavelength side laser light,
As a result, a light amount loss occurs as shown by hatching in FIG.

Therefore, according to the present invention, the RIM intensity required for the laser light of each wavelength incident on the objective lens can be satisfied, and the light quantity loss of the laser light of any laser light source can be avoided. An object of the present invention is to provide an optical pickup device that can be used.

[0013]

The invention according to claim 1 is
A laser light source that emits laser light of different wavelengths, a common collimator lens that converts the laser light emitted from these laser light sources into parallel light, and a laser light of each wavelength that is converted into parallel light is collected on an optical disk. An optical pickup device comprising: a common objective lens for irradiating light, wherein a far field pattern of a laser light source of a long wavelength side is a far field pattern of a laser light source of a short wavelength side among the laser light sources. It is set narrower than the pattern.

Therefore, the far field pattern of these laser light sources is related to the difference in effective diameter of the objective lens required between the short wavelength side laser light source and the long wavelength side laser light source. If the effective diameter of the short-wavelength side laser beam is used to secure the RIM intensity required for the short-wavelength side laser light by varying the width of the long-wavelength side laser light, the RIM intensity of the long-wavelength side laser light It is possible to optimize so as to satisfy the RIM intensity level required for the long wavelength side laser light, and as a result, it is possible to suppress the light amount loss of the long wavelength side laser light source and improve the light utilization efficiency. .

According to a second aspect of the present invention, in the optical pickup device according to the first aspect, there is provided light combining means for combining the optical paths of the respective laser beams emitted from the laser light source toward the objective lens. A condenser lens is provided on the optical path between the light synthesizing means and the long wavelength side laser light source.

Therefore, in realizing the optical pickup device according to the first aspect, even if a laser light source having an appropriate FFP cannot be obtained in practice, it is provided on the optical path on the long wavelength side laser light source side. The optical pickup device according to the first aspect can be easily realized by providing the condenser lens and making the FFP apparently narrow.

According to a third aspect of the present invention, in the optical pickup device according to the first aspect, there is provided optical combining means for combining the optical paths of the laser beams emitted from the laser light source toward the objective lens. A diverging lens was provided on the optical path between the light synthesizing means and the laser light source on the short wavelength side.

Therefore, in realizing the optical pickup device according to the first aspect, even if a laser light source having an appropriate FFP cannot be obtained in practice, it is on the optical path on the short wavelength side laser light source side. By providing a diverging lens and making the FFP seemingly wide, the optical pickup device according to claim 1 can be easily realized.

According to a fourth aspect of the present invention, in the optical pickup device according to the first aspect, the laser light sources are fixed in close proximity to the same base member in a chip configuration, and these laser light sources and the collimating lens are provided. A light transmission plate is provided between the light transmission plates, and a condenser lens is formed on the optical axis of the laser light source on the long wavelength side of the light transmission plate.

Therefore, even in the case where the laser light source part is integrated in one package as a laser chip structure, the optical pickup device according to claim 1 can be easily realized according to the case of claim 2. .

According to a fifth aspect of the present invention, in the optical pickup device according to the fourth aspect, the emission point position of the long wavelength side laser light source is closer to the collimator lens than the emission point position of the short wavelength side laser light source. It was set so that

Therefore, in the optical pickup device according to the fourth aspect, it is necessary to correct the light emitting point positions of the collimator lens and each laser light source to an appropriate position in order to obtain parallel light with high accuracy. By setting the emission point position of the intervening long wavelength side laser light source to a position closer to the collimator lens than the emission point position of the short wavelength side laser light source, and correcting both emission point positions by making them relatively different, It is possible to prevent displacement of the light emitting point of the laser.

According to a sixth aspect of the present invention, in the optical pickup device according to the first aspect, the laser light sources are fixed in a chip configuration close to the same base member, and these laser light sources and the collimating lens are provided. A light transmitting plate is provided between the light transmitting plates, and a diverging lens is formed on the optical axis of the laser light source on the short wavelength side of the light transmitting plate.

Therefore, even in the case where the laser light source part is integrated in one package as a laser chip structure, the optical pickup device according to claim 1 can be easily realized according to the case of claim 3. .

According to a seventh aspect of the invention, in the optical pickup device according to the sixth aspect, the light emitting point position of the short wavelength side laser light source is farther from the collimator lens than the light emitting point position of the long wavelength side laser light source. It was set so that

Therefore, in the optical pickup device according to the sixth aspect, it is necessary to correct the light emitting point positions of the collimator lens and each laser light source to an appropriate position in order to obtain parallel light with high accuracy, but the divergence lens intervenes. By setting the emission point position of the short-wavelength side laser light source to a position farther from the collimating lens than the emission point position of the long-wavelength side laser light source, and making corrections by making both emission point positions relatively different, It is possible to prevent displacement of the light emitting point position.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
And it demonstrates based on FIG. The same parts as those shown in FIGS. 8 to 11 are denoted by the same reference numerals, and the description thereof will be omitted (the same applies to the following embodiments).

FIG. 1 shows a configuration example of the optical pickup device of the present embodiment. The configuration is the same as that of the optical pickup device shown in FIG. Here, in the present embodiment, the far field of the two semiconductor lasers 1 and 5 is
The patterns (FFP = Far Field Pattern) are set to be different. Specifically, as shown in FIG.
The FFP of the long wavelength side semiconductor laser 1 is set to be narrower than the FFP of the short wavelength side semiconductor laser 5.

As a result, when the collimator lens 2 for collimating two laser beams into parallel light is shared as shown in FIG. 1, the intensity distribution of the parallel light incident on the objective lens 4 is as shown in FIG. . In this case, the effective diameter of the objective lens 4 is different between the two laser wavelengths (short wavelength and long wavelength), and the effective diameter of the long wavelength side laser light by the long wavelength side semiconductor laser 1 is limited. Laser 1 FFP
Is narrowed, the RIM intensity of the long-wavelength side laser light is also the laser of the long-wavelength side laser when the RIM intensity required for the short-wavelength side laser light is to be secured by the OL effective diameter on the short-wavelength side. It is possible to optimize so as to satisfy the RIM intensity required for light. As a result, the light amount loss of the long wavelength side semiconductor laser 1 can be suppressed and the light utilization efficiency can be improved.

A second embodiment of the present invention is shown in FIGS.
It will be described based on. In this embodiment, a convex lens 9 as a condenser lens is provided on the optical path between the two-wavelength combining prism 6 and the long wavelength side semiconductor laser 1.

In realizing the above-mentioned first embodiment,
Optimizing the FFP of the semiconductor lasers 1 and 5 is also envisaged in the case where it is difficult to obtain the desired FFP due to technical problems in laser production. Therefore, in the present embodiment, 2
By disposing the convex lens 9 on the optical path between the wavelength synthesizing prism 6 and the long-wavelength side semiconductor laser 1, as shown in FIG. Also, by making the FFP apparently narrower,
The FFP characteristics as shown in FIG. 2 can be provided.

A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, contrary to the above embodiment, a concave lens 10 as a diverging lens is provided on the optical path between the two-wavelength combining prism 6 and the short wavelength side semiconductor laser 5.

As described above, by disposing the concave lens 10 on the optical path between the two-wavelength combining prism 6 and the short wavelength side semiconductor laser 5, the FFP is more apparent than the FFP when the concave lens 10 is not arranged. By making the width wider, the FFP characteristics as shown in FIG. 2 can be provided.
That is, by expanding the FFP of the laser light on the short wavelength side,
The FFP of the laser light on the long wavelength side is relatively narrowed.

A fourth embodiment of the present invention will be described with reference to FIG. The present embodiment shows an application example to the case of using a two-wavelength laser light source device in which a plurality of laser light sources are integrated as a laser chip in one package.
That is, the laser chip 11 as a long-wavelength side laser light source with a wavelength of 780 nm and the laser chip 12 as a short-wavelength side laser light source with a wavelength of 650 nm are mounted and formed in the same laser chip mount base 13. Has been done. Then, a collimator lens (corresponding to the collimator lens 2) and these laser chips 11,
A light transmission plate 14 is provided between the light transmission plate 12 and the light transmission plate 12. In this light transmission plate 14, a convex lens 15 portion as a condenser lens is formed integrally on the optical axis of a laser chip 11 as a long wavelength side laser light source with the optical axes aligned.

According to this structure, the FFP of the long wavelength side laser light source (laser chip 11) is the short wavelength side laser light source (laser chip 1) as in the case of the second embodiment.
It can be set to be narrower than the FFP of 2).

By the way, in the case of the present embodiment, it is necessary to correct the light emitting point positions P1 and P2 of the collimator lens and the laser chips 11 and 12 to appropriate positions in order to obtain parallel light with high accuracy. In this regard, as shown in FIG. 6, the light emitting point position P1 of the long wavelength side laser light source (laser chip 11) in which the convex lens 15 is interposed is set closer to the collimating lens than the light emitting point position P2 of the short wavelength side laser light source (laser chip 12). It is possible to prevent the displacement of the emission point position of the two-wavelength laser by setting the emission point positions P1 and P2 to be relatively different from each other and performing correction by making them relatively different.

The fifth embodiment of the present invention will be described with reference to FIG. This embodiment also shows an application example to the optical pickup device using the laser chips 11 and 12 according to the fourth embodiment, and according to the third embodiment, the light transmission plate 14 has a short wavelength. A concave lens 16 portion as a diverging lens with its optical axis aligned is integrally formed on the optical axis of a laser chip 12 as a side laser light source.

According to such a configuration, the FFP of the long wavelength side laser light source (laser chip 11) is the short wavelength side laser light source (laser chip 1) in the same manner as in the second embodiment.
It can be set to be narrower than the FFP of 2).

By the way, in order to correct the light emitting point positions P1 and P2 of the laser chips 11 and 12 in the present embodiment to appropriate positions, as shown in FIG. The emission point position P2 of the side laser light source (laser chip 12) is set to the long wavelength side laser light source (laser chip 1).
By setting a position farther from the collimating lens than the light emitting point position P1 of 1) and correcting both light emitting point positions P1 and P2 by making them relatively different, it is possible to prevent the light emitting point position shift of the two-wavelength laser.

[0040]

According to the first aspect of the present invention, in accordance with the difference in effective diameter of the objective lens required between the short wavelength side laser light source and the long wavelength side laser light source, the fur of these laser light sources is dealt with.・ Field pattern (Far Field Pat)
tern), the RIM intensity of the long wavelength side laser light is to be secured when the RIM intensity required for the short wavelength side laser light is secured by the effective diameter of the short wavelength side objective lens by making the width different. The intensity can also be optimized so as to satisfy the RIM intensity level required for the laser light on the long wavelength side, and as a result, the loss of the light amount of the laser light source on the long wavelength side can be suppressed and the light utilization efficiency can be reduced. Can be improved.

According to the second aspect of the present invention, in realizing the optical pickup device of the first aspect, even if a laser light source having an appropriate FFP cannot be actually obtained, a long wavelength is obtained. The optical pickup device according to claim 1 can be easily realized by providing a condenser lens on the optical path on the side of the side laser light source to apparently narrow the width of the FFP.

According to the third aspect of the invention, in realizing the optical pickup device of the first aspect, even if a laser light source having an appropriate FFP cannot be actually obtained, a short wavelength is obtained. By providing a divergence lens on the optical path on the side of the side laser light source to make the FFP apparently wide, the optical pickup device according to claim 1 can be easily realized.

According to the invention described in claim 4, even in the case where the laser light source part is integrated in one package as a laser chip structure, according to the case of claim 2,
The described optical pickup device can be easily realized.

According to the invention described in claim 5, in the optical pickup device according to claim 4, it is necessary to correct the light emitting point positions of the collimator lens and each laser light source to appropriate positions in order to obtain parallel light with high accuracy. However, the emission point position of the long wavelength side laser light source with the condensing lens interposed is set to a position closer to the collimator lens than the emission point position of the short wavelength side laser light source so that both emission point positions are relatively different. By performing the correction in this way, it is possible to prevent the displacement of the emission point of the two-wavelength laser.

According to the sixth aspect of the present invention, even in the case where the laser light source unit is integrated in one package as a laser chip configuration, the first aspect of the present invention can be applied in accordance with the third aspect.
The described optical pickup device can be easily realized.

According to the invention described in claim 7, in the optical pickup device according to claim 6, it is necessary to correct the light emitting point positions of the collimator lens and each laser light source to appropriate positions in order to obtain parallel light with high accuracy. However, the emission point position of the short wavelength side laser light source where the divergence lens is interposed is set to a position farther from the collimator lens than the emission point position of the long wavelength side laser light source, and both emission point positions are made relatively different. By the correction, it is possible to prevent the displacement of the emission point of the two-wavelength laser.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing FFP characteristics.

FIG. 3 is a schematic configuration diagram showing an optical pickup device according to a second embodiment of the present invention.

FIG. 4 is a functional explanatory view showing the FFP diaphragm action.

FIG. 5 is a schematic configuration diagram showing an optical pickup device according to a third embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a light source unit of an optical pickup device according to a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a light source unit of an optical pickup device according to a fifth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a conventional example of a two-light source type optical pickup device.

FIG. 9 is an enlarged cross-sectional view near the objective lens.

FIG. 10 is a characteristic diagram showing a relationship between general FFP and RIM intensity.

FIG. 11 is a characteristic diagram showing a relationship between conventional FFP and RIM intensity.

[Explanation of symbols] 1 Long wavelength side laser light source 2 Collimating lens 3 optical disks 4 Objective lens 5 Short wavelength side laser light source 6 Photosynthesis means 9 Condensing lens 10 Divergence lens 11 Long wavelength side laser light source 12 Short wavelength side laser light source 13 Base member 14 Light transmission plate 15 Condensing lens 16 Divergence lens

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5D119 AA41 AA43 BA01 BB01 BB02                       BB04 EC45 EC47 FA08 JA02                       JA17 LB04 LB05                 5D789 AA41 AA43 BA01 BB01 BB02                       BB04 EC45 EC47 FA08 JA02                       JA17 LB04 LB05

Claims (7)

[Claims] 1. A laser light source that emits laser light of different wavelengths, a common collimator lens that converts the laser light emitted from these laser light sources into parallel light, and a laser of each wavelength that is converted into parallel light. An optical pickup device comprising: a common objective lens for converging and irradiating light onto an optical disc, comprising:
An optical pickup device characterized in that a field pattern (Far Field Pattern) is set narrower than a far field pattern of a laser light source on the short wavelength side. 2. A light synthesizing means for synthesizing the optical paths of the respective laser beams emitted from the laser light source toward the objective lens, and on the optical path between the light synthesizing means and the long wavelength side laser light source. The optical pickup device according to claim 1, further comprising a condenser lens. 3. A light synthesizing means for synthesizing the optical paths of the respective laser beams emitted from the laser light source toward the objective lens, and is provided on an optical path between the light synthesizing means and the short wavelength side laser light source. The optical pickup device according to claim 1, further comprising a diverging lens. 4. The laser light source having a chip structure is fixed in close proximity to the same base member, and a light transmitting plate is provided between the laser light source and the collimating lens, and the long wavelength of the light transmitting plate is provided. The optical pickup device according to claim 1, wherein a condenser lens is formed on the optical axis of the side laser light source. 5. The light emitting point position of the long wavelength side laser light source is set so as to be closer to the collimator lens than the light emitting point position of the short wavelength side laser light source. Optical pickup device. 6. The laser light source having a chip structure is fixed in close proximity to the same base member, and a light transmitting plate is provided between the laser light source and the collimating lens, and the short wavelength of the light transmitting plate is provided. The optical pickup device according to claim 1, wherein a diverging lens is formed on the optical axis of the side laser light source. 7. The light emitting point position of the short wavelength side laser light source is set to be a position farther from the collimator lens than the light emitting point position of the long wavelength side laser light source. Optical pickup device.