JP4287082B2 - Optical pickup device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device having a semiconductor laser light source.
[0002]
[Prior art]
An optical pickup mounted on an optical disc apparatus guides laser light emitted from a semiconductor laser light source to an objective lens using an optical component such as a reflection mirror, and focuses a light beam on the optical disc to form a spot. This semiconductor laser generally has an astigmatic difference.
[0003]
An example of an optical pickup mounted on an optical disc apparatus is described in Japanese Patent Laid-Open No. 8-55363.
[0004]
FIG. 2 is a diagram showing a schematic configuration of a semiconductor laser and a state of laser light emitted therefrom. The intensity distribution 12 of the light beam emitted from the semiconductor laser 8 has a direction perpendicular to the joining surface of the active layer 13 (hereinafter, this direction is referred to as θ⊥) and a direction perpendicular to θ⊥, that is, the junction. It differs depending on the direction parallel to the surface (hereinafter this direction is referred to as θ //). That is, the intensity distribution 12 has a substantially elliptical shape in which θ⊥ is the longitudinal direction. The cause of such an intensity distribution 12 is that the position of the beam waist of the emitted light is on the resonator end face of the active layer 13 at θ⊥, whereas it is in the resonator of the active layer 13 at θ //. Because there is. Such an intensity distribution appears as astigmatism on the optical disc.
[0005]
[Problems to be solved by the invention]
However, as shown in the prior art, an optical pickup that reflects a light beam by a plane reflecting mirror and guides the light beam to an objective lens cannot correct astigmatism and causes astigmatism on an optical disk. There was a problem.
[0006]
In recent years, there are various types of optical discs depending on the substrate thickness and the corresponding wavelength. For example, optical discs such as CD and CD-R have a substrate thickness of 1.2 mm and the optimum wavelength of laser light for recording / reproduction is in the 780 nm band, whereas DVD-ROM and DVD-RAM have disc substrate thicknesses. The corresponding wavelength is 650 nm band at 0.6 mm. For this reason, optical pickups for DVDs that have begun to spread in recent years are mainly equipped with semiconductor lasers having two wavelengths of 780 nm and 650 nm in consideration of compatibility with CD optical discs that are already widespread. ing.
[0007]
With the expansion of the use of these optical discs, miniaturization and cost reduction of optical disc apparatuses are being promoted, and for this purpose, technology for miniaturization and simplification of optical pickups is indispensable. In particular, when considering the correspondence to multiple types of optical discs, an optical system corresponding to each optical disc is required. However, the simplification of the optical system or the reduction in the number of components by sharing optical components can Effective for miniaturization and cost reduction.
In this regard, in the prior art, in order to enable reproduction of a plurality of types of optical discs, a technique for combining two laser beams having different wavelengths on an intermediate optical path and reproducing information with a single objective lens. Is disclosed. Here, a wavelength-selective prism is used as an optical element for synthesizing an optical path for using two light beams as a common optical system. However, since this wavelength selective prism is a bonded part, it costs parts, and is a major obstacle to further cost reduction of the optical pickup.
[0008]
The present invention has been made in view of the above-described background, and its object is to correct astigmatism caused by the astigmatism of the semiconductor laser itself and to reduce the cost without increasing the number of components. It is an object to provide an optical pickup device .
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first means of the present invention includes a semiconductor laser light source, an optical element that reflects a light beam emitted from the semiconductor laser light source, an elastic support member that fixes the optical element, In an optical pickup device comprising at least an objective lens for condensing a light beam reflected by the optical element on an optical disc, and a light receiving element for receiving reflected light from the optical disc via the optical element,
A housing for positioning and fixing at least the semiconductor laser light source, the optical element, the elastic support member, and the optical element; and a specific portion of the housing at a position near substantially both ends of the optical element in one direction. A reflecting surface of the laser beam emitted from the semiconductor laser light source or a receiving surface with which the opposite surface abuts, and the surface of the optical element opposite to the surface abutting the receiving surface is the optical surface of the elastic support member. The optical element is pressed against the housing by abutting on an element abutting portion, and the optical element is disposed in a state of being forcedly deformed in a predetermined direction into a substantially cylindrical surface or a substantially toroidal surface. It is what.
[0010]
According to a second means of the present invention, in the first means, an arbitrary part of the surface of the optical element opposite to the surface contacting the receiving surface of the housing is replaced with the optical element of the elastic support member. It is characterized by being brought into contact with the contact portion .
[0011]
According to a third means of the present invention, in the second means, the receiving surface of the casing has two on one side and one on the opposite side, and the optical element and the casing abut on three. And the inside of the three contact points of the optical element is pressed and fixed by the elastic support member .
[0012]
The fourth means of the present invention is the third means, wherein the elastic support member has two optical element contact portions, and the two optical element contact portions are located near the two receiving surfaces on one side. And it has the structure arrange | positioned in the position close | similar to the said receiving surface of one side .
[0013]
According to a fifth means of the present invention, in the third means, the elastic support member has one optical element contact portion, and one optical element contact portion is near one receiving surface on one side. And it has the structure arrange | positioned in the position close | similar to two said receiving surfaces on one side .
[0014]
The sixth means of the present invention is the third means, wherein the elastic support member has one optical element contact portion, and one optical element contact portion is located near the two receiving surfaces on one side. And it has the structure arrange | positioned in the position close | similar to the said receiving surface of one side .
[0015]
According to a seventh means of the present invention, in the first to sixth means, the thickness of the optical element is 0.3 mm or more and 0.8 mm or less .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a first embodiment of an optical pickup device according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic arrangement view of optical components of an optical pickup showing a first embodiment according to the present invention, FIG. 2 is a diagram showing an astigmatic difference in a general semiconductor laser, and FIG. 3 is a first embodiment according to the present invention. FIG. 4 is a schematic diagram showing a method for reducing astigmatism generated on an optical disk due to the astigmatic difference of the semiconductor laser of the optical pickup showing the configuration, FIG. 4 is a schematic explanatory diagram showing the positioning and fixing structure of the optical element, and FIG. 4 is a schematic view of the optical element fixing structure in FIG. 4 viewed from the A direction, and FIG. 6 is a schematic view of the optical element fixing structure in FIG.
[0019]
In FIG. 1 to FIG. 6, the laser light emitted from the semiconductor laser 8 is reflected by a wavelength selective half mirror (DH mirror) 5 that is an optical element through a diffraction grating 11, and converted into a parallel light beam by a collimator lens 4. The objective lens 2 is reached. The laser beam is narrowed down by the objective lens 2 to form a predetermined light spot on the track of the optical disk 1.
[0020]
The objective lens 2 is held by an actuator 3. By applying a predetermined current to each drive coil disposed in the actuator 3, the objective lens 1 follows the upper and lower sides of the optical disk 1 and the meandering of the track. It is driven vertically and horizontally so that the positional relationship between the light spot and the track can always be kept constant.
[0021]
The laser light beam reflected from the optical disk 1 reaches the optical element (DH mirror) 5 by following the same optical path as the outward light in the reverse direction. Thereafter, the laser beam passes through the optical element (DH mirror) 5 at a predetermined ratio, forms a spot on the light receiving element 9 via the detection lens 10, and detects a read signal from the optical disk 1.
[0022]
The semiconductor laser 8, the diffraction grating 11, the collimating lens 4, the actuator 3, the optical element (DH mirror) 5, the detection lens 10, and the light receiving element 9 are attached and fixed to the housing 6 and integrated. Further, the optical element (DH mirror) 5 has a thickness of about 0.4 mm and has a property of being elastically deformed by an appropriate pressing force. As described above, the semiconductor laser 8 generally has the astigmatic difference ΔZ shown in FIG.
[0023]
FIG. 2 shows the intensity distribution 12 of the laser beam generated by the astigmatic difference ΔZ of the semiconductor laser 8 itself. The light beam emitted from the semiconductor laser 8 has different intensity distributions in a direction (θ⊥) perpendicular to the bonding surface of the active layer 13 and a direction (θ //) perpendicular thereto. The distribution is a substantially elliptical shape in which the heel direction is the longitudinal direction. As described above, the substantially elliptical light intensity distribution caused by the astigmatic difference ΔZ appears as astigmatism on the optical disc 1 and adversely affects the optical disc system as described above.
[0024]
Therefore, if astigmatism in the opposite direction to the astigmatism caused by the astigmatism ΔZ possessed by the semiconductor laser 8 itself can be added by some means, the optical disc 1 due to the effect of the astigmatism ΔZ possessed by the semiconductor laser 8 itself. It is possible to correct the astigmatism above.
[0025]
4 to 6 show a fixing structure of the optical element (DH mirror) 5. The receiving surface 6 a of the housing 6 receives the vicinity of both ends of the reflecting surface of the optical element (DH mirror) 5 that reflects the laser light emitted from the semiconductor laser 8. As shown in FIG. 5, the receiving surface 6a disposed in the housing 6 has two points on one side and one point on the opposite side, and is configured to receive the optical element (DH mirror) 5 at a total of three points.
[0026]
Further, as shown in FIG. 6, in a state where the optical element (DH mirror) 5 is in contact with the receiving surface 6a of the housing 6, the surface opposite to the reflecting surface of the laser light emitted from the semiconductor laser 8 is provided. Is pressed by the optical element contact portion 7 a of the elastic support member 7.
[0027]
Further, the position where the elastic support member 7 presses the optical element (DH mirror) 5 is inside the receiving surface 6a at two points on one side of the housing 6 (the receiving surface side at one point on one side), and is positively thick. The thin optical element (DH mirror) 5 having a thickness of about 0.4 mm is elastically deformed. That is, the elastic support member 7 is provided between the receiving surface 6 a on the opposite side of the surface of the optical element (DH mirror) 5 that is in contact with the receiving surface 6 a of the housing 6 and between the receiving surfaces 6 a on both sides of the housing 6. , The optical element (DH mirror) 5 is elastically deformed in a convex shape when viewed from the semiconductor laser side.
[0028]
In the case of the first embodiment of the present invention shown in FIG. 1, the joint surface of the active layer 13 of the semiconductor laser 8 and the bus bar of the optical element 5 that is elastically deformed by the elastic support member 7 and deformed into a substantially cylindrical surface shape. Are arranged so as to be substantially vertical. The optical element (DH mirror) 5 is elastically deformed in a convex shape when viewed from the semiconductor laser 8. In this case, the laser light emitted from the semiconductor laser 8 has an effect of widening the light intensity distribution of the laser light in the θ // direction, as shown in FIG.
[0029]
As a result, it is possible to add astigmatism in the opposite direction to the astigmatism of the laser beam caused by the astigmatism ΔZ of the semiconductor laser 8 itself, and the optical element (DH mirror) 5 As a result, the astigmatism generated by the astigmatism ΔZ of the semiconductor laser 8 itself is corrected, resulting in a laser beam in a more ideal aberration state, equivalently a laser beam with less astigmatism. Is incident on the collimating lens 4.
[0030]
Further, by appropriately setting the rigidity and receiving surface position of the elastic support member 7, the contact position between the elastic support member 7 and the optical element (DH mirror) 5, the thickness of the optical element (DH mirror) 5, and the like, The curvature of the substantially cylindrical surface (or substantially toroidal surface) of the optical element (DH mirror) 5 can be set with a desired curvature, and as a result, laser light having a desired amount of astigmatism in a desired direction can be obtained. It becomes possible to enter the collimating lens 4.
[0031]
As described above, according to the first embodiment of the present invention, the shape of the reflecting surface of the optical element (DH mirror) 5 arranged in the divergent light beam is changed to a substantially cylindrical surface shape (or a predetermined curvature) by the elastic support member 7 (or Astigmatism caused by the astigmatism of the semiconductor laser 8 can be corrected without increasing the number of parts, using an expensive prism, and thus having an inexpensive configuration. Therefore, it is possible to realize good signal reproduction or signal recording.
[0032]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a view showing a fixing structure of the optical element (DH mirror) 5 in the second embodiment of the present invention when viewed from the A direction shown in FIG. Similarly, FIG. 8 is a view showing a fixing structure of the optical element (DH mirror) 5 viewed from the B direction shown in FIG. 4 in the second embodiment.
[0033]
Also in the second embodiment of the present invention, the receiving surface 6 a of the housing 6 receives the vicinity of both ends of the reflecting surface of the optical element (DH mirror) 5 that reflects the laser light emitted from the semiconductor laser 8. ing. As shown in FIG. 7, the receiving surface 6a disposed in the housing 6 has two points on one side and one point on the opposite side, and has a structure for receiving the optical element (DH mirror) 5 at a total of three points. Further, as shown in FIG. 8, the surface opposite to the reflection surface of the laser beam emitted from the semiconductor laser 8 with the optical element (DH mirror) 5 in contact with the receiving surface 6 a of the housing 6. Is pressed by the optical element contact portion 7 a of the elastic support member 7.
[0034]
In addition, the position where the elastic support member 7 presses the optical element (DH mirror) 5 is inside the receiving surface 6a at one point on one side of the housing 6 (on the side closer to two points on one side), and the thickness is positively about A thin optical element (DH mirror) 5 of about 0.4 mm is elastically deformed. That is, the elastic support member 7 is provided between the receiving surface 6 a on the opposite side of the surface of the optical element (DH mirror) 5 that is in contact with the receiving surface 6 a of the housing 6 and between the receiving surfaces 6 a on both sides of the housing 6. As in the first embodiment, the optical element (DH mirror) 5 is elastically deformed in a convex shape when viewed from the semiconductor laser 8 side.
[0035]
Also in the case of the second embodiment, the optical element (DH) which is elastically deformed by the joint surface of the active layer 13 of the semiconductor laser 8 and the elastic support member 7 and is deformed into a substantially cylindrical surface (or a substantially toroidal surface). Mirror) 5 is arranged so as to be substantially perpendicular to the bus. The optical element (DH mirror) 5 is elastically deformed in a convex shape when viewed from the semiconductor laser 8. In this case, the laser light emitted from the semiconductor laser 8 has an effect of widening the light intensity distribution of the laser light in the θ // direction, as shown in FIG.
[0036]
As a result, it is possible to add astigmatism in the opposite direction to the astigmatism of the laser beam caused by the astigmatism ΔZ of the semiconductor laser 8 itself, and the optical element (DH mirror) 5 As a result, the astigmatism generated by the astigmatism ΔZ of the semiconductor laser 8 itself is corrected, resulting in a laser beam in a more ideal aberration state, equivalently a laser beam with less astigmatism. Is incident on the collimating lens 4.
[0037]
As described above, also in the second embodiment of the present invention, the shape of the reflecting surface of the optical element (DH mirror) 5 arranged in the divergent light beam is changed to the substantially cylindrical surface shape (or substantially the same with the elastic support member 7). Astigmatism caused by the astigmatism of the semiconductor laser 8 can be corrected with an inexpensive configuration without increasing the number of parts and without using an expensive prism. Needless to say, good signal reproduction or signal recording can be realized.
[0038]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram showing a forced deformation state of the optical element (DH mirror) 5 according to the third embodiment of the present invention. In the case of the third embodiment, the receiving surfaces 6 a of the housing 6 receive substantially the vicinity of both ends of the surface opposite to the reflecting surface of the optical element (DH mirror) 5 that reflects the laser light emitted from the semiconductor laser 8. It has a structure. As shown in FIGS. 5 and 7, the receiving surface 6a arranged in the housing 6 has two points on one side and one point on the opposite side, and is configured to receive the optical element (DH mirror) 5 at a total of three points. ing. In addition, in the structure shown in FIG. 6 or FIG. 8, the reflecting surface of the laser beam emitted from the semiconductor laser 8 is pressed by the elastic support member 7. Further, the elastic support member 7 presses the surface of the optical element (DH mirror) 5 that is in contact with the receiving surface 6 a of the housing 6 and between the receiving surfaces 6 a on both sides of the housing 6. A thin optical element (DH mirror) 5 having a concave shape as viewed from the semiconductor laser 8 side and having a thickness of about 0.4 mm is elastically deformed so that the direction is opposite to that of the first or second embodiment.
[0039]
In the case of the third embodiment, the optical element (DH mirror) which is elastically deformed by the joint surface of the active layer 13 of the semiconductor laser 8 and the elastic support member 7 and is deformed into a substantially cylindrical surface (or a substantially toroidal surface). It is assumed that the 5 busbars are substantially horizontal. The optical element (DH mirror) 5 is elastically deformed into a concave shape when viewed from the semiconductor laser 8. In this case, the laser light emitted from the semiconductor laser 8 has an effect of narrowing the light intensity distribution of the laser light in the θ⊥ direction, as shown in FIG.
[0040]
As a result, it is possible to add astigmatism in the opposite direction to the astigmatism of the laser beam caused by the astigmatism ΔZ of the semiconductor laser 8 itself, and the optical element (DH mirror) 5 As a result, the astigmatism generated by the astigmatism ΔZ of the semiconductor laser 8 itself is corrected, resulting in a laser beam in a more ideal aberration state, equivalently a laser beam with less astigmatism. Is incident on the collimating lens 4.
[0041]
As described above, also in the third embodiment of the present invention, the shape of the reflection surface of the optical element (DH mirror) 5 arranged in the divergent light beam is changed to the substantially cylindrical surface shape (or substantially the same with the elastic support member 7). Astigmatism caused by the astigmatism of the semiconductor laser 8 can be corrected with an inexpensive configuration without increasing the number of parts and without using an expensive prism. Therefore, good signal reproduction or signal recording can be realized.
[0042]
Although not shown, it goes without saying that the same effect can be obtained by the configuration of the present invention even in an optical system in which a plurality of semiconductor lasers 8 are mounted and a part of the optical system is shared. Moreover, although the case where the reflecting surface has a substantially cylindrical surface shape has been described in the above embodiment, it goes without saying that the same effect can be obtained even when the reflecting surface has a substantially toroidal surface shape.
[0043]
Furthermore, in the said embodiment, although the said operation | movement was implement | achieved with the optical element (DH mirror) 5 of thickness about 0.4 mm, the thickness of the optical element (DH mirror) 5 is 0.3-0.8 mm. Needless to say, an object can be elastically deformed by the same principle to obtain the same effect.
[0044]
Further, the rigidity of the elastic support member 7 that presses the optical element (DH mirror) 5 can be freely set, and the receiving surface interval, position, or elastic support member 7 of the optical element (DH mirror) 5 arranged on the housing 6 side. Therefore, the laser beam having a desired amount of astigmatism in a desired direction can be realized, and the astigmatism of the semiconductor laser 8 can be realized. There is also an effect that a correction amount of astigmatism caused by the difference ΔZ can be freely set.
[0045]
【The invention's effect】
As described above, according to the present invention, the predetermined position of the optical element (DH mirror) is appropriately pressed by the elastic support member having appropriate rigidity, such as the originally existing optical element (DH mirror) fixing spring. As a result, an optical element (DH mirror) having a substantially cylindrical or toroidal reflecting surface having a desired curvature can be formed, and as a result, the astigmatism generated by the astigmatic difference of the semiconductor laser itself. Aberrations can be corrected with an inexpensive configuration, and there is an effect of realizing good signal reproduction or recording.
[Brief description of the drawings]
FIG. 1 is a schematic arrangement view of optical components of an optical pickup according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an astigmatic difference in a general semiconductor laser.
FIG. 3 is a schematic diagram showing a method for reducing astigmatism that occurs on an optical disk due to the astigmatic difference of the semiconductor laser of the optical pickup according to the first embodiment of the present invention.
FIG. 4 is a schematic explanatory view showing a positioning and fixing structure of an optical element.
5 is a schematic view of the optical element fixing structure in FIG. 4 as viewed from the direction A. FIG.
6 is a schematic view of the optical element fixing structure in FIG. 4 as viewed from the B direction.
7 is a schematic view of the optical element fixing structure shown in FIG. 4 according to the second embodiment of the present invention as viewed from the direction A. FIG.
FIG. 8 is a schematic view of the optical element fixing structure shown in FIG. 4 according to the second embodiment of the present invention, viewed from the B direction.
FIG. 9 is a diagram showing a forced deformation state of an optical element according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical disk 2 Objective lens 3 Actuator 4 Collimate lens 5 Optical element (DH mirror)
6 Case (Optical base)
6a Receiving surface 7 Elastic support member 7a Optical element contact portion 8 Semiconductor laser 9 Light receiving element 10 Detection lens 11 Diffraction grating 12 Light intensity distribution 13 Active layer

Claims (7)

A semiconductor laser light source, an optical element that reflects a light beam emitted from the semiconductor laser light source, an elastic support member that fixes the optical element, and an objective lens that focuses the light beam reflected by the optical element on an optical disk And an optical pickup device comprising at least a light receiving element that receives reflected light from the optical disc via the optical element,
A housing for positioning and fixing at least the semiconductor laser light source, the optical element, the elastic support member, and the optical element; and a specific portion of the housing at a position near substantially both ends of the optical element in one direction. A reflecting surface of the laser beam emitted from the semiconductor laser light source or a receiving surface with which the opposite surface abuts, and the surface of the optical element opposite to the surface abutting the receiving surface is the optical surface of the elastic support member. The optical element is pressed against the housing by abutting on an element abutting portion, and the optical element is disposed in a state of being forcedly deformed in a predetermined direction into a substantially cylindrical surface or a substantially toroidal surface. Optical pickup device. 2. The optical pickup device according to claim 1, wherein an arbitrary portion of the surface of the optical element opposite to the surface that contacts the receiving surface of the housing is applied to the optical element contact portion of the elastic support member. An optical pickup device that is in contact with each other . The optical pickup device according to claim 2 , wherein the receiving surface of the housing has two on one side and one on the opposite side, and the optical element and the housing are in contact with each other, and An optical pickup device having a structure in which the inside of three contact points of the optical element is pressed and fixed by the elastic support member . 4. The optical pickup device according to claim 3, wherein the elastic support member has two optical element abutting portions, and the two optical element abutting portions are located near the two receiving surfaces on one side and one on one side. An optical pickup device having a structure arranged at a position close to the receiving surface . 4. The optical pickup device according to claim 3 , wherein the elastic support member has one optical element abutting portion, and one optical element abutting portion is provided near one receiving surface on one side and two on one side. An optical pickup device having a structure arranged at a position close to the receiving surface . 4. The optical pickup device according to claim 3 , wherein the elastic support member has one optical element abutting portion, and one optical element abutting portion is located near the two receiving surfaces on one side and one on one side. An optical pickup device having a structure arranged at a position close to the receiving surface . 7. The optical pickup device according to claim 1 , wherein a thickness of the optical element is 0.3 mm or more and 0.8 mm or less .

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