JP2002367218A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which realizes an improvement in light utilization efficiency and a reduction in the weight of an actuator moving section. SOLUTION: The luminous flux 19 emitted from a semiconductor laser 1 is condensed by a condenser lens 5, is reflected by a first reflecting surface 7 and a second reflecting surface 10 and is condensed to the recording surface of an optical disk 18 by an objective lens 16, by which recording bits are read out. The exit luminous flux 19 from the semiconductor laser 1 is condensed by the condenser lens 5 and is changed in the diversion angle of the luminous flux and therefore the diameter of the luminous flux with which the first reflecting surface 7 is irradiated can be made smaller. The ratio at which the luminous flux reflected by the second reflecting surface 10 is shielded at the first reflecting surface can be made lower and therefore the light utilization efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device for recording or reproducing information on or from an optical recording medium such as an optical disk by light.

[0002]

2. Description of the Related Art As a conventional optical pickup device, an optical head described in Japanese Patent Application Laid-Open No. 5-101435 and an optical head device described in Japanese Patent Application Laid-Open No. 10-162413 are disclosed. An optical head described in Japanese Patent Application Laid-Open No. 5-101435 will be described as a first conventional example with reference to FIG.

At the center of the entrance surface of the objective lens 74, a prism having a slope formed at an angle of 45 degrees with the lens optical axis is bonded, and this slope becomes the first reflection surface 72. A hologram is also formed on the surface of the first reflection surface 72.

The laser beam emitted from the semiconductor laser 71 enters from a direction perpendicular to the optical axis of the objective lens 74,
The light is reflected by the first reflecting surface 72, is bent in the direction of 90 degrees, and spreads and is incident on the second reflecting surface 73.

The second reflecting surface 73 is a total reflecting surface provided substantially at right angles to the optical axis of the objective lens 74, and the light beam reflected by the second reflecting surface 73 spreads further on the objective lens 74. Incident. The light beam forms an image as a spot of a predetermined size on the recording surface 75 of the optical disk by the objective lens 74, and the information recorded as pits is read.

The light beam reflected by the optical disk recording surface 75 and containing information follows a path reverse to the outward path, and enters the first reflecting surface 72 via the objective lens 74 and the second reflecting surface 73. The first-order diffracted light diffracted by the hologram is diffracted to the multi-segment light detector 76, from which a reproduction signal and a servo signal are detected.

An optical head device described in Japanese Patent Application Laid-Open No. 10-162413 will be described as a second conventional example with reference to FIG.

In this conventional example, light emitted from a semiconductor laser 81 is reflected by a first reflecting surface 82 and a second reflecting surface 83, is refracted by an emitting surface 84, and is reflected on a recording surface of an optical disk 85. Collect light. The return light from the optical disk 85 follows a path reverse to the outward path, is guided to the first reflection surface 82, is diffracted by the hologram on the first reflection surface 82 to the photodetector 86, and outputs the reproduced signal and the servo signal. A signal is detected. Further, since the first reflection surface 82 has a convex shape and the numerical aperture of incident light is enlarged by the convex mirror,
The optical path length can be reduced, and the thickness of the optical pickup device can be reduced.

[0009]

However, in the first conventional optical pickup device called an optical head, if the thickness of the optical pickup device is reduced, the objective lens 74, the second reflection surface 73 and the second Since the distance between the reflection surface 73 and the first reflection surface 72 is reduced, the first reflection surface 7
The distance between the semiconductor laser 2 and the semiconductor laser 71 must be widened. Divergent light from the semiconductor laser 71 is applied to the first reflection surface 7.
2, the semiconductor laser 71 and the first reflecting surface 7
When the distance between the first lens and the second lens increases, the area of the first reflecting surface 72 increases, and as a result, the amount of light reflected by the second reflecting surface 73 and traveling toward the objective lens 74 increases, and the light use efficiency increases significantly. There are problems such as lowering.

Although the radiation angle of the semiconductor laser 71 differs between the vertical direction and the horizontal direction, one of them is as small as several degrees, so that a long optical path length is required to obtain a light beam with a sufficient diameter on the incidence surface of the objective lens 74. I do. Therefore, there is a limit to the reduction in thickness even when a bending optical system is used.

When the first reflecting surface 82 is formed into a convex curved surface as in the second conventional example, the light beam can be expanded with a short optical path length, but strict control of the curved surface shape is required. Generally, it is difficult to control the shape of a curved surface, and it is more difficult to suppress a shape error particularly when the area of the reflection surface is small. Therefore, the shape error of the reflection surface causes an enlargement of a condensed spot on the optical disk 85.

The optical pickup device is a system in which the semiconductor laser 71, the photodetector 76, the objective lens 74, etc. are integrated and driven by an actuator, so that the load on the actuator is high and the weight of the movable part is desired to be reduced. .

An object of the present invention is to provide an optical pickup device which improves the light use efficiency and reduces the weight of the movable portion of the actuator.

[0014]

According to the present invention, there is provided a light condensing member for condensing light on an optical recording medium, a first reflecting surface and a second reflecting surface are arranged side by side, and a side of the first reflecting surface is arranged. The light beam emitted from the light source provided in the first reflecting surface is reflected by the first reflecting surface,
An optical pickup device in which a light beam from the reflective surface is reflected in a substantially opposite direction by the second reflective surface, and a light beam from the second reflective surface is shielded by the first reflective surface and condensed on the optical recording medium. Is interposed between the light source and a first reflecting surface,
An optical pickup device comprising means for changing a divergence angle of a light beam emitted from a light source to reduce a diameter of a light beam irradiated on a first reflecting surface.

According to the present invention, the light beam emitted from the light source is once collected near the first reflection surface, and the area of the light beam irradiated on the first reflection surface is reduced, so that the second reflection surface is reduced. Since the ratio of the reflected light flux blocked by the first reflecting surface can be reduced, the light use efficiency can be improved.

Further, the present invention is characterized in that the first reflecting surface, the second reflecting surface, and the light-collecting member are integrated to constitute one light-collecting element.

According to the present invention, the first reflecting surface, the second reflecting surface, and the light-collecting member constitute one light-collecting element, so that the thickness of the light-collecting member in the optical axis direction is increased. , And the size of the optical pickup device can be reduced.

Further, the invention is characterized in that the first reflection surface is provided inside the light-collecting element.

According to the present invention, since the first reflecting surface is provided inside the light-collecting element, the size of the optical pickup device can be reduced.

Further, the invention is characterized in that the means for changing the divergence angle of the light beam emitted from the light source is a lens.

According to the present invention, the light beam emitted from the light source is once condensed by the lens and the light beam having a large divergence angle is incident on the first reflecting surface, so that the optical path length can be shortened and the optical pickup device can be shortened. Can be made thinner.

Further, the present invention is characterized in that the lens is a ball lens or a GRIN lens.

According to the present invention, the size of the optical pickup device can be reduced by using a ball lens or a GRIN lens as the lens.

According to another aspect of the present invention, a light condensing member for condensing light on an optical recording medium, a first reflecting surface and a second reflecting surface are arranged side by side, and a light source provided on a side of the first reflecting surface is provided. Is reflected by the first reflecting surface, the light beam from the first reflecting surface is reflected by the second reflecting surface in a substantially opposite direction, and the light beam from the second reflecting surface is reflected by the first reflecting surface. An optical pickup device which is shielded and condensed on an optical recording medium, comprising an optical fiber for transmitting a light beam emitted from the light source to a first reflection surface.

According to the present invention, since the light beam emitted from the light source propagates to the first reflecting surface by the optical fiber, the ratio of the light beam blocked by the first reflecting surface is small, and the light use efficiency is improved. In addition to the above, the weight of the movable part can be reduced, so that the servo following performance and the access speed can be improved.

Further, the present invention is characterized in that the first reflection surface, the second reflection surface and the light condensing member are integrated to constitute one light condensing element.

According to the present invention, since the first reflecting surface, the second reflecting surface, and the light-collecting member constitute one light-collecting element, the thickness of the light-collecting member in the optical axis direction is increased. , And the size of the optical pickup device can be reduced.

Further, the present invention is characterized in that one end face of the optical fiber is on the optical axis of the light-collecting element, and the end face functions as a first reflecting surface.

According to the present invention, one end face of the optical fiber is on the optical axis of the light condensing element, and the end face functions as the first reflecting surface, so that the light propagated through the optical fiber is perpendicular to the optical axis. Can be injected.

Further, the present invention is characterized in that the optical fiber is a single mode fiber.

According to the present invention, since the optical fiber is a single mode fiber, the light beam emitted from the optical fiber becomes a Gaussian beam, and can be treated in the same manner as the light beam emitted from the light source.

Further, the present invention is characterized in that a light beam emitted from the light source is coupled to an optical fiber by a ball lens or a GRIN lens.

According to the present invention, the light beam emitted from the light source is converted into a light beam having a small divergence angle by the ball lens or the GRIN lens and is coupled to the optical fiber, so that the size of the optical pickup device can be reduced.

Further, the present invention is characterized in that the diameter of the light-shielding region shielded by the first reflecting surface is 40% or less of the diameter of the light beam reflected by the second reflecting surface.

According to the present invention, since the diameter of the light-shielding region shielded by the first reflecting surface is 40% or less of the diameter of the light beam reflected by the second reflecting surface, the light use efficiency is further improved. be able to.

Further, the present invention is characterized in that the light collecting member is an objective lens. According to the present invention, since the surface shape of the objective lens can be designed in advance so as to cancel the aberration generated by the incident light of the objective lens, it is possible to prevent the focal spot from expanding.

The present invention is characterized in that the light collecting member is a diffraction lens. According to the present invention, since sufficient light-collecting performance can be secured by using a diffraction lens, the thickness of the light-collecting element can be further reduced.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an optical pickup device 100 according to a first embodiment of the present invention. The optical pickup device 100 shown in FIG. 1 includes an objective lens 16 and an optical module 13.

The optical module 13 includes the semiconductor laser 1,
Submount 2, beam splitter 3, condenser lens 5,
It comprises a first reflecting surface 7, a dielectric plate 8, a photodetector 9, a second reflecting surface 10, and a silicon substrate 12. The optical module 13 is a silicon substrate 12 on which the photodetector 9 is integrated.
A dielectric plate member 8 on which the beam splitter 3, the condenser lens 5, and the first reflecting surface 7 are mounted, and a light source mounted on the submount 2 so as to be provided on the side of the first reflecting surface 7 The semiconductor laser 1 is arranged. The beam splitter 3 and the member 6 supporting the first reflecting surface 7
It is formed by processing a dielectric member on the dielectric plate 8. The lens guide 11 of the condenser lens 5 is formed by providing a recess in the dielectric plate 8. A reflection film serving as a second reflection surface 10 is provided below the dielectric plate 8 at a position where the first reflection surface 7 is located. Above the first reflection surface 7, a condensing member is provided. An objective lens 16 is provided, and the light-collecting member, the first reflection surface 7 and the second reflection surface 10 are arranged side by side. The optical module 13 and the objective lens 16 are housed in a package 21 and driven by an actuator 17 in the optical axis direction of the objective lens 16 and in a direction perpendicular to the optical axis of the objective lens 16.

The condenser lens 5 is interposed between the semiconductor laser 1 and the first reflecting surface 7 and irradiates the first reflecting surface 7 by changing the divergence angle of the light beam 19 emitted from the semiconductor laser 1. This is means for reducing the diameter of the light beam, and a minute ball lens or GRIN (Gradient Index) lens may be used. The GRIN lens has a function of condensing light by giving a refractive index distribution to the lens, and has a high refractive index at the center of the optical axis and a low refractive index at the periphery.

Next, the operation of the first embodiment configured as described above will be described. The light beam 19 emitted from the semiconductor laser 1 travels in a direction parallel to the surface of the silicon substrate 12, passes through the beam splitting surface 4 of the beam splitter 3, and is condensed by the condenser lens 5, and the divergence angle is changed. First
Is applied to the reflection surface 7 of the light source. The light beam 19 is transmitted to the first reflecting surface 7.
Then, it is bent 90 degrees in the opposite direction to the objective lens 16 and passes through the dielectric plate 8, and then in the second reflection surface 10 in a substantially opposite direction,
That is, the light is reflected in the direction of the objective lens 16 and enters the objective lens 16. The light flux 19 spreads to the effective diameter of the objective lens 16 before propagating to the objective lens 16, and is condensed by the objective lens 16 on a recording surface of an optical disk 18 as an optical recording medium.

Since the first reflecting surface 7 is located between the second reflecting surface 10 and the objective lens 16, the light beam traveling from the second reflecting surface 10 to the objective lens 16 is transmitted by the first reflecting surface 7. Some are shaded. Since the light beam traveling from the second reflection surface 10 to the objective lens 16 is shielded by the first reflection surface 7, an annular light beam lacking in the central portion is incident on the objective lens 16, and the light use efficiency is reduced. . However, in the present invention,
Beam 1 emitted from semiconductor laser 1 by condensing lens 5
9 is condensed and the divergence angle of the light beam is changed, so that the diameter of the light beam applied to the first reflecting surface 7 can be reduced, and the light beam reflected by the second reflecting surface 10 on the first reflecting surface 7 Can be reduced in light-shielding ratio, so that light use efficiency can be improved.

In order to reduce the size of the condenser lens 5 in the middle of the optical path, a ball lens or a GRIN lens must be used. However, by designing the surface shape of the objective lens 16 in advance so as to cancel this aberration, it is possible to prevent the condensing spot from expanding. Objective lens 16
Since the optical module 13 and the optical module 13 are integrated, even when servo control is performed, the optical axis of the objective lens 16 and the condenser lens 5 do not shift, and aberration compensation by the objective lens 16 becomes possible.

The condensed spot is reflected on the recording surface of the optical disk 18, and the reflected return light reflected on the recording surface travels along a path reverse to the outward path. Optical disk 18 for reflected return light
The reflected return light passes through the objective lens 16, the second reflecting surface 10, the first reflecting surface 7, and the ball lens which is the condenser lens 5, and returns to the beam splitter. It is led to 3. A part 20 of the return light is reflected by the beam splitting surface 4 and travels downward and enters the photodetector 9.

In the photodetector 9, the incident light beam is photoelectrically processed to reproduce recorded information and to output a focusing error signal F.
An ES (Focusing Error Signal) and a tracking error signal TES (Tracking Error Signal) are detected. There are various methods for detecting FES and TES. In the present embodiment, for example, the spot size method may be used for detecting FES, and the push-pull method may be used for detecting TES.

The spot size method is an FES detection method utilizing the fact that the spot diameter on the photodetector 9 changes when the focus shifts. The method of detecting FES and TES will be described in detail with reference to FIG. FIG. 2 is a configuration diagram showing the relationship between the photodetector 9 and the spot 20 on the photodetector 9, and the photodetector 9 is divided into four segments. FIG. 2B shows a state at the time of focusing, and when a focus shift occurs, the spot changes as shown in FIGS. 2A and 2C.

As shown in FIG. 2B, the position of the photodetector 9 is adjusted so that the light amount incident on the segments 9a and 9d and the light amount incident on the segments 9b and 9c coincide with each other at the time of focusing. I have. When the optical disk 18 moves away from the optical pickup device 100, the spot diameter on the photodetector 9 decreases as shown in FIG. 2A, and the amount of light incident on the inner segments 9b and 9c increases. Conversely, when the optical disk 18 approaches the optical pickup device 100, the spot diameter increases as shown in FIG. 2C, and the amount of light incident on the outer segments 9a and 9d increases. The difference between the amount of incident light on the outer segments 9a and 9d and the amount of incident light on the inner segments 9b and 9c is the FES. Further, the push-pull method is a TES detection method that utilizes the fact that the light amount distribution of the spot on the photodetector 9 changes when a tracking error occurs. FIG. 2 (b)
In the photodetector 9 shown in (1), the difference signal between the output from the upper segment 9a, 9b and the output from the lower segment 9c, 9d is TES.

Assuming that the output signals of the photodetectors 9a to 9d are Sa to Sd, respectively, FES is obtained by FES = (Sa + Sd)-(Sb + Sc) TES is obtained by TES = (Sa + Sb)-(Sc + Sd).

On the basis of the above FES and TES, focusing servo control and tracking servo control of the optical module 13 and the objective lens 16 are performed.
The reproduction signal is obtained by the sum of Sa to Sd.

Next, a method of manufacturing the optical module 13 according to the first embodiment will be described with reference to FIG. FIG.
FIG. 7 is a cross-sectional view of a manufacturing step of the optical module 13.

First, as shown in FIG. 3A, a photodetector 9 for signal detection and a signal processing circuit (not shown) for the photodetector 9 are formed on a silicon substrate 12 by a semiconductor process. Further, a second reflective surface 10 is formed by forming a reflective film.

Next, as shown in FIG. 3 (b), a first light-transmitting plastic layer and a second light-transmitting plastic layer 14, which are dielectric plates 8, are formed on the reflection film.
The material of the light transmitting plastic layer 14 is PET
(Polyethylene Terephthalate), polyether sulfone, polyimide, or the like can be used. The thickness of the first light-transmitting plastic layer is, for example, 1 mm,
Has a thickness of, for example, 600 μm.
m. When the light-transmitting plastic layer 14 is polyimide, it can be formed by applying a polyimide varnish, followed by baking and curing. Alternatively, a film-like material may be attached via an adhesive or the like.

Next, as shown in FIG. 3C, by etching the second light-transmitting plastic layer 14, the light-transmitting plastic layer 14 other than the 45-degree mirror section 6 and the beam splitter section 3b is removed. Remove. further,
A semi-transmissive film and a total reflection film are formed. Examples of the etching method include a method such as reactive ion etching and laser ablation etching.
In particular, laser application etching is suitable for processing a polymer material, and has advantages such as a high processing speed, no photolithography step, and high processing accuracy. It is preferable that the inclined surface having a slope of 45 degrees is formed by laser application etching.

As the transflective film and the total reflection film, a metal such as gold and aluminum or a dielectric multilayer film may be used. A semi-transmissive film is formed on the inclined surface of the beam splitter 3, and a total reflection film is formed on the 45-degree mirror unit 6, so that the beam splitting surface 4 and the first reflection surface 7 are formed. After the film is formed by a method such as sputtering and vacuum evaporation, photolithography and etching are performed to remove the film in an unnecessary region so that the film remains only on the slope.

Next, as shown in FIG. 3D, a third light-transmitting plastic layer is formed, and etching is further performed to remove the third light-transmitting plastic layer other than the beam splitter 3a. As a material of the third light-transmitting plastic layer, for example, an ultraviolet curable resin can be used. Further, the first light-transmitting plastic layer is also etched to remove the layer in the region where the semiconductor laser 1 is disposed, and to fix the condenser lens 5 to the lens guide 11.
To form

Finally, as shown in FIG. 3E, the semiconductor laser 1 mounted on the submount 2 is
The optical module 13 is completed by fixing the condenser lens 5 on the lens guide 11 and the lens guide 11. The position of the optical module 13 and the objective lens 16 is determined and the package 2
Fix to 1.

In the present invention, since the optical path is bent in the thickness direction of the optical pickup device 100, the height (thickness) of the optical pickup device 100 can be reduced. When the height (thickness) of the optical pickup device 100 can be reduced, the entire optical pickup device 100 also becomes lightweight, so that the following performance and access speed of each servo are improved. Further, since the optical module 13 is easily mass-produced and the optical pickup device 100 is constituted by the optical module 13 and the objective lens 16, the optical pickup device 100 can be provided with less adjustment steps and stable performance. .

In the first conventional example, as shown in FIG. 11, the distance between the semiconductor laser 71 and the first reflecting surface 72 must be longer than the radius of the objective lens 74. The fully spread luminous flux is the first
Therefore, the area required for the first reflecting surface 72 is increased. When the area of the first reflecting surface 72 increases, the light is reflected by the second reflecting surface 73 and is
Of the light beam incident on the optical disk becomes large, causing a reduction in light use efficiency and a deterioration in the shape of the condensed spot on the recording surface 75 of the optical disk.

The relationship between the area of the first reflecting surface 72 and the deterioration of the shape of the converging spot will be described with reference to FIG. FIG. 4 is a graph showing the light-collecting characteristics of the objective lens 74 having a circular light-shielding region at the center of the axis. Light incident on the objective lens 74 is a Gaussian beam, and the case where the full width at half maximum matches the effective diameter of the objective lens 74 is shown. The horizontal axis is the radius of the light-blocking area when the radius of the objective lens 74 is 1. One of the vertical axes is the peak intensity of the main lobe (normalized as 1 when there is no light-shielding area), and the other is the peak intensity ratio between the side lobe and the main lobe.

As shown in FIG. 4, when the area of the circular light-shielding region increases, the peak intensity of the main lobe decreases and the peak intensity of the side lobe increases. A decrease in the peak intensity of the main lobe and an increase in the side lobe lead to a deterioration in signal quality. In order to suppress the deterioration of the signal quality, the radius of the circular light-blocking area should be set to 4 times the effective diameter of the objective lens 74.
It is desirable to keep it at 0% or less. That is, it is desirable that the diameter of the light-shielding region shielded by the first reflection surface 72 be suppressed to 40% or less of the light beam reflected by the second reflection surface 73.

However, in the present invention, since the light is once collected near the first reflecting surface 7, the area of the first reflecting surface 7 can be reduced, and the object is reflected by the second reflecting surface 10 Since the kick of the light beam incident on the lens 16 can also be reduced, a decrease in light use efficiency and a deterioration in signal quality can be suppressed.

In the second conventional example, as shown in FIG. 12, the first reflecting surface 82 has a convex curved surface to reduce the thickness. However, in the case of a mirror having a curved surface and a small area, the surface shape is reduced. In addition, the required accuracy of the surface roughness was very severe, and the fabrication was difficult. However, in the present invention, since the light beam whose light is once condensed by the condenser lens 5 and whose divergence angle is increased is incident on the first reflection surface 7, the optical path length can be shortened, and the first reflection surface 7 In this case, the thickness of the optical pickup device 100 can be sufficiently reduced. Since the surface shape of the first reflecting surface 7 may be flat, it is easy to suppress errors in the surface shape and surface roughness of the reflecting surface, and the manufacturing is easy.

An example of a conventional example and an estimated value of the light use efficiency and the thickness of the optical pickup device 100 of the present invention will be described with reference to FIG. FIG. 5 shows an optical pickup device 10.
FIG. 2 is a sectional view of an optical system No. 0. FIG. 5A is a cross-sectional view of a main part of an optical system according to the present invention, and FIG. 5B is a cross-sectional view of a main part of an optical system in a conventional example.

In the first conventional example, the semiconductor laser 71
The numerical aperture NA (Numerical Aperture) of the emitted light is 0.1
0, assuming that the effective diameter of the objective lens 74 is φ2 mm, the distance between the semiconductor laser 71 and the objective lens 74 is 10 mm. Assuming that the distance from the semiconductor laser 71 to the first reflecting surface 72 is 6 mm, the distance between the incident surface of the objective lens 74 and the second reflecting surface 73 is about 2 mm. The diameter of the area occupied by the first reflection surface 72 when viewed from the optical axis direction is φ1.
2 mm, and the light use efficiency is required to be 64%.

On the other hand, in the present invention, assuming that the effective diameter of the objective lens 16 is φ2 mm, which is the same as that of the first conventional example, and the numerical aperture after NA conversion is 0.3, the distance from the focal point to the objective lens 16 is 3 0.3 mm. Assuming that the distance from the focal point to the first reflecting surface 7 is 1 mm, the thickness of the dielectric plate 8 is 1 mm, and the refractive index of the dielectric plate 8 is 1.5, the incident surface of the objective lens 16 and the second reflection The distance from the surface 10 is about 2 mm, which is the same thickness as the conventional example. The diameter of the area occupied by the first reflecting surface 7 when viewed from the optical axis direction is φ0.6 m.
m, and the light use efficiency is required to be 91%. Although the thickness of the optical pickup device 100 is the same as that of the conventional example, the light use efficiency can be improved, and the light condensing characteristics of the spot on the optical disk 18 can be improved. Further, since the optical module 13 is easily mass-produced and the optical pickup device 100 is composed of the optical module 13 and the objective lens 16, the optical pickup device 100 has a small number of adjustment steps and a stable performance.
Can be provided.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a sectional view of a main part of an optical system of an optical pickup device 101 according to a second embodiment of the present invention. The optical pickup device 101 shown in FIG.
It is configured to include the light converging element 25 and the optical module 13. The optical module 13 includes a semiconductor laser 1, a submount 2, a beam splitter 3, a condenser lens 5, a dielectric plate 8, a photodetector 9, and a silicon substrate 12.

The light-collecting element 25 includes a first reflecting surface 27 inclined at 45 degrees inside the light-collecting element 25, an incident surface 26 on the side of the light-collecting element 25, a second reflecting surface 28 on the lower surface of the light-collecting element 25, An emission surface 29 which is a light-collecting member is provided on the upper surface of the element 25, and the first reflection surface 27, the incident surface 26, the second reflection surface 28, and the emission surface 29 are integrated into one light-collecting element. 25. The entrance surface 26 is an optically polished plane. Further, the first reflection surface 27 bends the light beam incident from the incident surface 26 of the light-collecting element 25 by 90 degrees and reflects it in the direction of the second reflection surface 28. The second reflection surface 28 is a total reflection aspheric surface, for example, an elliptical surface or a paraboloid, which is concave with respect to the incident light beam, and the exit surface 29 is also an aspheric surface. The optical module 13 and the light-collecting element 25 are housed in the package 21, and are driven by the actuator 17 in the optical axis direction of the light-collecting element 25 and in a direction perpendicular to the optical axis of the light-collecting element 25.

Next, the operation of the second embodiment configured as described above will be described. As in the first embodiment, the light beam 19 emitted from the semiconductor laser 1 is condensed via the beam splitter 3 and the ball lens which is the condensing lens 5, and travels to the condensing element 25. The luminous flux transmits through the incident surface 26 of the light-collecting element 25 and once converges, then diverges. The divergent light is reflected by the first reflection surface 27 inside the light-collecting element 25 and turned downward by 90 degrees. , And is guided to the second reflection surface 28 which is the bottom surface of the light condensing element 25. Next, the light beam is reflected by the second reflection surface 28 in substantially the opposite direction, and the light beam spreads between two reflections on the first reflection surface 27 and the second reflection surface 28. Further, the light beam is refracted on the exit surface 29 of the light condensing element 25 and condensed on the recording surface of the optical disk 18. Light collecting element 25
The surface shapes of the second reflecting surface 28 and the exit surface 29 are designed so that aberrations generated by the ball lens, which is the condenser lens 5, are canceled and the spot diameter on the recording surface of the optical disk 18 is minimized. I have. Here, a curved mirror is required as in the second conventional example. However, in the present invention, since the diameter of the mirror is as large as several mm, a curved mirror can be manufactured with sufficient manufacturing accuracy.

The reflected return light from the optical disk 18 is
In the same manner as in the embodiment, the light enters the photodetector 9 along the optical path in the direction opposite to the outward path, and the photodetector 9 detects a servo error signal and a reproduction signal.

Next, a method for manufacturing the above-described light-collecting element 25 will be described with reference to FIG.
This will be described with reference to FIG. FIG. 7 is a cross-sectional view of the light-collecting element 25 in a manufacturing process.

First, as shown in FIG. 7A, a glass rod 30 having a high melting point is cut to obtain an end face inclined at 45 degrees, and the end face inclined at 45 degrees is polished to obtain a metal deposition film or the like. To form a total reflection surface. The total reflection surface becomes the first reflection surface 27 of the light collecting element 25.

Next, as shown in FIG.
A dielectric material 33 having transparency and good workability, such as a glass material such as a synthetic resin material such as a polycarbonate resin, is put into dies 31 and 32 together with a glass rod 30 having a high melting point, and pressed. A material is selected so that the refractive index of the glass bar 30 and the surrounding dielectric material 33 are substantially equal and the melting point of the glass bar 30 is higher than the pressing temperature of the dielectric material 33.

Thereafter, as shown in FIG. 7C, the glass bar 30 is cut to remove unnecessary portions, and the outer surface of the second reflection surface is coated with a reflection film 28. Finally, by polishing the incident surface 26 through which the incident light beam passes, the light condensing element 25 having the reflecting surface 27 inside can be formed.

The optical module 13 is manufactured by the same method as in the first embodiment. The optical pickup device 101 is completed by adjusting the positions of the optical module 13 and the light condensing element 25 and fixing them to the package 21.

The optical system of the optical pickup device 101 according to the second embodiment is different from the first embodiment in that a light beam enters from the side surface of the light-collecting element 25. In the first embodiment, since the optical module 13 and the objective lens 16 are arranged in the thickness direction of the optical pickup device 100, the thickness of the objective lens 16 is added to the thickness of the optical module 13 and the thickness of the entire optical pickup device 100. Is thicker. For example, if the effective diameter of the objective lens 16 is 2 m
Assuming that m, the thickness of the optical module 13 is about 2 mm, the thickness of the objective lens 16 is about 1 mm, and the thickness of the optical pickup device 100 is 3 mm.

On the other hand, in the configuration of this embodiment, the optical module 13 and the light condensing element 25 are arranged in a plane. Since the thickness of the optical module 13 is suppressed to about 1 to 2 mm, the thickness of the optical pickup device 101, particularly, the thickness of the objective lens in the optical axis direction can be reduced by reducing the thickness of the light condensing element 25.

As a specific design example of the light collecting element 25,
If the effective diameter is φ2 mm, the refractive index is 1.8, the radius of curvature of the exit surface 29 is 1.2 mm, and the NA of the incident light beam is converted from 0.4 to 0.17 at the second reflection surface 28. The thickness of the light condensing element 25 can be suppressed to about 2.5 mm, and the thickness of the optical pickup device 101 can be made smaller than the thickness of the optical pickup device 100 in the first embodiment.

Further, a diffractive lens which is a condensing member may be formed on the exit surface 29. By utilizing the diffraction, sufficient light-collecting performance can be ensured even if the distance between the second reflection surface 28 and the emission surface 29 is reduced, so that the thickness of the light-collecting element 25 can be further reduced.

Further, since the optical module 13 can be easily mass-produced and the optical pickup device 101 is composed of the optical module 13 and the light condensing element 25, the optical pickup device 101 having a small number of adjustment steps and a stable performance is provided. be able to.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a configuration diagram of an optical system of an optical pickup device 102 according to the third embodiment of the present invention. FIG. 8A is a front view of an optical system of the optical pickup device 102 of the present invention, and FIG. 8B is a cross-sectional view of a main part of the optical system of the optical pickup device 102. The optical pickup device 102 shown in FIG.
7 and a servo signal detecting element 49, and an optical module 13 serving as a fixed portion and an optical fiber 42 for coupling between the elements of the optical module 13. The light collecting element 47 and the servo signal detecting element 49 are housed in the package 21 and driven by the actuator 17. The optical fiber 42 has one end face on the optical axis of the light condensing element 47, and propagates the light flux 19 emitted from the semiconductor laser 1 to a reflection film 44 functioning as a first reflection surface.

The optical module 13 includes a semiconductor laser 1, a submount 2, a beam splitter 3, a condenser lens 5, a dielectric plate 8, a photodetector 9, and a silicon substrate 12, as in the second embodiment. The difference from the second embodiment is that the light beam 19 emitted from the semiconductor laser 1 is coupled to the optical fiber 42.

The other end of the optical fiber 42 is
7 is connected to the channel waveguide 43. The end face of the channel waveguide 43 opposite to the optical fiber 42 connection side is:
A reflection film 44, which is located at the center of the optical axis of the light-collecting element 47 and functions as a first reflection surface, is formed. The angle of the reflection film 44 is set at an angle inclined by 45 degrees from the optical axis of the channel waveguide 43 so that the propagation light of the optical fiber 42 is emitted toward the lower surface of the light-collecting element 47. Optical fiber 4
2. A single-mode channel waveguide 43 is used. Since the single mode is used, the light beam emitted from the optical fiber 42 and the channel waveguide 43 is a Gaussian beam, and can be handled in the same manner as the light beam 19 emitted from the semiconductor laser 1.

The condensing element 47 has a reflection type diffraction grating 46 at the center of the lower surface and a diffraction lens 45 at the upper surface. The reflection type diffraction grating 46 splits the reflected return light into two, and
Numeral 5 focuses the incident light beam on the recording surface of the optical disk 18.

Next, the operation of the third embodiment configured as described above will be described. Similarly to the second embodiment, the light beam 19 emitted from the semiconductor laser 1 is coupled to the optical fiber 42 via the beam splitter 3 and the ball lens which is the condenser lens 5. The light that has propagated in the optical fiber 42 is coupled to the channel waveguide 43 on the light-collecting element 47 and is emitted from the reflection-side end face of the channel waveguide 43.
Since the end face is inclined 45 degrees from the optical axis of the channel waveguide 43 and the reflection film 44 functioning as the first reflection surface is provided, the light beam is emitted in the direction perpendicular to the optical axis of the channel waveguide 43 and collected. Reflection type diffraction grating 46 on the lower surface of optical element 47
Head for. Next, the light beam is reflected upward by the reflection type diffraction grating 46 and is focused on the recording surface of the optical disk 18 by the diffraction lens 45 on the upper surface of the light collecting element 47.

The reflected return light from the optical disk 18 follows the optical path in the direction opposite to the outward path and is split by the reflection type diffraction grating 46. The zero-order light is directly coupled to the channel waveguide 43,
The light is guided to the optical module 13 via the optical fiber 42, and the reproduced signal is detected in the optical module 13. The other diffracted light 52 (shown by a broken line) is reflected on the upper surface of the light-collecting element 47, passes through the lower surface, and is guided to the photodetector 48 on the servo signal detecting element 49. Photodetector 4
At 8, detections such as FES and TES are made.

Next, a method of manufacturing the optical pickup device 102 will be described with reference to FIG. FIG.
FIG. 7 is a cross-sectional view in a manufacturing step of the light collecting element 47.

First, as shown in FIG. 9A, a grating is formed on the lower surface of the dielectric plate 54 by using photolithography and etching techniques, and a reflective film is formed on the grating to form a reflective film. A diffraction grating 46 is formed.

Next, as shown in FIG.
The channel waveguide 43 and the diffraction lens 4 are formed on the upper surface of the dielectric plate material 54 by using photolithography and etching techniques.
5 and the optical fiber guide 53 are formed. The end surface of the channel waveguide 43 is processed into a 45-degree inclined surface to form a reflection film 44.
Is formed.

Finally, as shown in FIG. 9C, the dielectric plate member 54 is cut to cut out the light-collecting element 47.

The optical module 13 is manufactured in the same manner as in the first embodiment, and an optical fiber guide 41 is provided at the end of the optical module 13. The optical fiber guide 53 of the light collecting element 47 and the optical fiber guide 4 of the optical module 13
The optical fiber 42 is bonded and fixed to the optical pickup 1 and the optical pickup device 102 is completed.

In the present invention, the optical module 13 and the light-collecting element 47 are connected by the optical fiber 42 which is flexible and has a strong property against bending. There is no need to drive together. That is, the optical module 13 may be fixed and only the light condensing element 47 may be servo-controlled. By using the configuration using the optical fiber 42, the movable portion can be significantly reduced in size and weight, and the following performance of each servo can be achieved. And the access speed can be improved. Further, since the optical module 13 can be easily mass-produced and the optical pickup device 102 is composed of the optical module 13 and the light condensing element 47, the optical pickup device 102 with a small number of adjustment steps and stable performance can be provided. .

Further, similarly to the second embodiment, the light-collecting element 4
7 and the optical module 13 are arranged in a plane,
The thickness of the optical pickup device 102 is substantially equal to the thickness of the light collecting element 47 and the servo signal detecting element 49. Assuming that the effective diameter of the condensing element 47 is φ2 mm and the NA of the light beam emitted from the channel waveguide 43 is 0.4, the condensing element 4
The thickness of the servo signal detecting element 4 is reduced to about 2 mm.
When the thickness of 9 is added, the thickness of the optical pickup device 102 becomes about 2.5 mm, and the thickness of the optical pickup device 102 can be reduced as compared with the first embodiment.
Further, since the optical module 13 can be arranged at any position, the size of the optical recording / reproducing apparatus can be reduced.

The light beam reflected by the reflection type diffraction grating 46 and incident on the diffraction lens 45 is scattered by the channel waveguide 43 and the reflection film 44. However, while the effective diameter of the light condensing element 47 is several mm, the diameter of the single-mode channel waveguide 43 is as small as about 10 μm, and the scattering by the waveguide is extremely small, so that the light use efficiency can be improved. .

Furthermore, since the light propagating through the optical fiber 42 is emitted while maintaining the polarization plane by using the polarization plane preserving fiber, it can be used for reproducing a magneto-optical disk.

In the structure of this embodiment, since the movable portion is only the condensing element 47 and the servo signal detecting element 49, the condensing element 47 is made smaller, so that the movable portion is mounted on the slider. It becomes possible. By using the slider mounted type, the optical recording / reproducing apparatus can be made smaller and thinner.

Here, a ball lens is used as the condenser lens 5 for coupling the light beam 19 emitted from the semiconductor laser 1 and the optical fiber 42, but a lens of another form, for example, a GRIN lens may be used. Also, the light-collecting element 47
As in the second embodiment, the upper and lower surfaces may be formed by press working with aspheric surfaces.

In this configuration, the optical fiber 42 having a large NA is used.
By using the channel waveguide 43, the divergence angle of the light beam emitted from the channel waveguide 43 to the light-collecting element 47 can be increased. If the divergence angle of the emitted light beam is increased, the thickness of the optical pickup device 102 can be reduced.

In this case, the minute beam splitter 3
Although the configuration example of the optical module 13 using the condensing lens 5 has been described, a configuration using an optical waveguide may be used.
By using the optical waveguide structure, the thickness of the optical module 13 can be reduced and the productivity can be improved, and the optical waveguide structure is suitable for connection with a single mode optical fiber.

Further, as shown in FIG.
7 may be omitted, and an optical fiber 42 having an end face inclined at 45 degrees from the optical axis may be used instead. The end face of the optical fiber 42 is cut obliquely at 45 degrees, and the reflection film 55 is provided on the end face cut at 45 degrees, so that the propagation light of the optical fiber 42 is emitted in a direction perpendicular to the optical axis. By using the optical fiber 42 in which the propagating light is emitted in a direction perpendicular to the optical axis, the step of manufacturing the channel waveguide 43 can be omitted, and the distance between the channel waveguide 43 and the optical fiber 42 can be reduced. Coupling loss can also be prevented.

[0101]

As described above, according to the present invention, the light use efficiency can be improved.

Further, according to the present invention, the thickness of the light collecting member in the optical axis direction can be reduced, and the size of the optical pickup device can be reduced.

Further, according to the present invention, the light beam emitted from the light source is once condensed by the lens and the light beam having a large divergence angle is incident on the first reflecting surface, so that the optical path length can be shortened. The thickness of the device can be reduced.

Further, according to the present invention, light propagated through an optical fiber can be emitted in a direction perpendicular to the optical axis.

Further, according to the present invention, the light beam emitted from the optical fiber can be handled in the same manner as the light beam emitted from the light source.

Further, according to the present invention, it is possible to reduce the weight of the movable portion of the actuator, and to improve the servo tracking performance and the access speed.

Further, according to the present invention, it is possible to prevent the condensing spot from expanding. Further, according to the present invention, the thickness of the light collecting element can be further reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system of an optical pickup device 100 according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a relationship between a photodetector 9 and a spot 20 on the photodetector 9.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of the optical module 13;

FIG. 4 is an objective lens 74 having a circular light-shielding area at the center of the axis.
5 is a graph showing the light-collecting characteristics of FIG.

5 is a sectional view of an optical system of the optical pickup device 100. FIG.

FIG. 6 is a sectional view of a main part of an optical system of an optical pickup device 101 according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a manufacturing step of the light-collecting element 25.

FIG. 8 is a configuration diagram of an optical system of an optical pickup device 102 according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a manufacturing step of the light-collecting element 47.

FIG. 10 is a sectional view of a main part of an optical system of the optical pickup device 102;

FIG. 11 is a sectional view of a main part of an optical system of an optical pickup device of a first conventional example.

FIG. 12 is a sectional view of a main part of an optical system of an optical pickup device according to a second conventional example.

[Explanation of symbols]

 1, 71, 81 Semiconductor laser 2 Submount 3 Beam splitter 5 Condensing lens 7, 27, 72, 82 First reflecting surface 8, 54 Dielectric plate material 9, 48, 76, 86 Photodetector 10, 28, 73 , 83 Second reflective surface 12 Silicon substrate 13 Optical module 16, 74 Objective lens 17 Actuator 18, 85 Optical disk 25, 47 Condensing element 26 Incident surface 29 Exit surface 42 Optical fiber 43 Channel waveguide 44, 55 Reflective film 45 Diffraction Lens 46 Reflective diffraction grating 49 Servo signal detecting element 75 Optical disc recording surface 100, 101, 102 Optical pickup device

Claims (13)

[Claims] A light-collecting member for converging light on an optical recording medium;
And a second reflection surface are arranged side by side, and a light beam emitted from a light source provided on a side of the first reflection surface is reflected by the first reflection surface, and a light beam from the first reflection surface Is the second
An optical pickup device, which is reflected in a substantially opposite direction by the reflection surface of (1) and the light flux from the second reflection surface is shielded by the first reflection surface and condensed on an optical recording medium, comprising: the light source and the first light source; An optical pickup device interposed between the first reflection surface and the light-reflection surface to reduce the divergence angle of the light beam emitted from the light source to reduce the diameter of the light beam irradiated on the first reflection surface. 2. The optical pickup device according to claim 1, wherein the first reflection surface, the second reflection surface, and the light condensing member are integrated to form one light condensing element. 3. The optical pickup device according to claim 2, wherein the first reflection surface is provided inside the light-collecting element. 4. The optical pickup device according to claim 1, wherein the means for changing the divergence angle of the luminous flux emitted from the light source is a lens. 5. The lens according to claim 5, wherein the lens is a ball lens or a GR.
The optical pickup device according to claim 4, wherein the optical pickup device is an IN lens. 6. A condensing member for condensing light on an optical recording medium,
And a second reflection surface are arranged side by side, and a light beam emitted from a light source provided on a side of the first reflection surface is reflected by the first reflection surface, and a light beam from the first reflection surface Is the second
An optical pickup device, which is reflected in a substantially opposite direction by the reflection surface, and in which the light flux from the second reflection surface is shielded by the first reflection surface and condensed on the optical recording medium, is emitted from the light source. An optical pickup device comprising an optical fiber that propagates the transmitted light beam to the first reflection surface. 7. The optical pickup device according to claim 6, wherein the first reflection surface, the second reflection surface, and the light condensing member constitute one light condensing element. 8. The optical pickup device according to claim 6, wherein one end face of the optical fiber is on the optical axis of the light-collecting element, and the end face functions as a first reflecting surface. 9. The optical pickup device according to claim 6, wherein the optical fiber is a single mode fiber. 10. The optical pickup device according to claim 6, wherein the light beam emitted from the light source is coupled to an optical fiber by a ball lens or a GRIN lens. 11. The method according to claim 1, wherein the diameter of the light-shielding region shielded by the first reflection surface is 40% or less of the diameter of the light beam reflected by the second reflection surface. The optical pickup device according to any one of the above. 12. The optical pickup device according to claim 1, wherein the light collecting member is an objective lens. 13. The optical pickup device according to claim 1, wherein the light collecting member is a diffraction lens.