JP2009217914A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device remarkably reducing the size of an optical system in an optical axis direction of an objective lens. <P>SOLUTION: In the objective lens 100, a reflective surface 101 is formed on a surface at the side opposite to an emission surface 102, and an aperture 101a is formed at a part thereof. A curved reflective surface 102a is arranged, which guides a laser beam incident through the aperture 101a to the reflective surface 101. The laser beam emitted from a laser diode 201 is reflected by an erection mirror 203 and directed from the aperture 101a to the reflective surface 102a. The laser beam reflected by the reflective surface 102a is uniformly guided to the reflective surface 101. The laser beam reflected by the reflective surface 101 is converged by the emission surface 102, and is focused on a disk. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical pickup device, and is particularly suitable for use in downsizing an optical system.

  In recent years, along with miniaturization of optical disk devices, miniaturization of optical pickup devices has been promoted. In general, an optical pickup device is provided with an objective lens as a configuration for converging laser light on a disk, and a rising mirror is provided to reduce the size of the optical system in the optical axis direction of the objective lens. Yes.

  FIG. 6 is a diagram illustrating the relationship between the objective lens and the raising mirror. The raising mirror is disposed immediately below the objective lens. The laser light is incident on the rising mirror from a direction orthogonal to the optical axis of the objective lens, and is reflected in the direction toward the objective lens by the rising mirror. In this case, the dimensions of the optical system in the optical axis direction of the objective lens are determined by the thickness of the objective lens, the working distance and the movable amount of the objective lens, and the height of the rising mirror shown in FIG.

  However, since the laser beam is incident on the rising mirror with a light flux width corresponding to the numerical aperture of the objective lens, the height of the rising mirror is relatively large. If the rising mirror can be reduced in size, the dimensions of the optical system in the optical axis direction of the objective lens can be reduced.

  On the other hand, Patent Document 1 discloses an optical system shown in FIG. Laser light emitted from the semiconductor laser 11 passes through the beam splitter 12 and is converged by the ball lens 13. Thereafter, the laser light is reflected by the mirror 14 and the mirror 16 in the transparent substrate 15 and converged on the disk by the objective lens 17. The reflected light from the disk travels backward along the optical path, is reflected by the beam splitter 12, and is guided to the photodetector 18 in the transparent substrate 15.

In this configuration, since the laser light is incident on the mirror 14 in a state of being converged by the ball lens 13, the mirror 14 can be reduced in size. Therefore, the dimension of the optical system in the optical axis direction of the objective lens 17 can be reduced.
JP 2002-367218 A

  However, according to the configuration of Patent Document 1, since it is necessary to arrange the mirror 16 in addition to the mirror 14 at a position directly below the objective lens 17, the dimensions of the optical system in the optical axis direction of the objective lens 17 are as follows. The size of the mirror 16 increases. Further, in this configuration, since the mirror 14 is disposed at the optical axis position of the objective lens, the laser beam reflected by the mirror 16 is blocked by the mirror 14 at a high intensity central portion. For this reason, in this configuration, there is a problem that the laser beam cannot be efficiently guided to the disk.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical pickup device capable of remarkably reducing the size of an optical system in the optical axis direction of an objective lens. It is another object of the present invention to provide an optical pickup device that can efficiently guide laser light emitted from a laser light source to a recording medium.

  An optical pickup device according to a first aspect of the present invention includes a laser light source that emits laser light, and an objective lens that converges the laser light on a recording medium. Here, the objective lens includes a first reflection surface formed on a surface opposite to an emission surface, a translucent portion formed on the first reflection surface through which the laser light can pass, A second reflecting surface that guides the laser beam incident through the light transmitting portion to the first reflecting surface. The pickup device further includes an optical element that directs laser light emitted from the laser light source from the light transmitting portion to the second reflecting surface. Then, after being reflected by the second reflecting surface, the first reflecting surface, the laser beam reflected by the first reflecting surface is converged on the recording medium by the emitting surface, The surface shapes of the second reflecting surface and the emitting surface are adjusted. The laser light source, the objective lens, and the optical element are integrally accommodated by a holder.

  According to the optical pickup device according to this aspect, it is possible to reduce the beam width of the laser light when entering the objective lens. Therefore, the optical element (for example, the rising mirror) can be made small, and the size of the optical system in the optical axis direction of the objective lens can be remarkably reduced. In addition, since the beam width of the laser beam can be reduced in this way, the light transmitting portion and the second reflecting surface can be reduced. Therefore, the light quantity loss of the laser by a translucent part and a 2nd reflective surface can be suppressed, and the utilization efficiency of a laser beam can be improved.

  Furthermore, since the laser beam is converged by utilizing the reflection action on the first reflecting surface, chromatic aberration is suppressed compared to the case where the laser beam is converged only by the refraction action at the time of passing through the interface like a normal objective lens. can do. Therefore, for example, even if the wavelength of the laser beam varies due to a change in temperature or switching of output power, the degradation of the laser beam due to the wavelength variation can be suppressed.

  According to a second aspect of the present invention, in the optical pickup device according to the first aspect, the second reflecting surface is arranged at a position shifted from the optical axis of the objective lens. According to this aspect, since the second reflecting surface is arranged at a position shifted from the central portion of the laser beam, the high-intensity laser beam central portion can be suppressed from being blocked by the second reflecting surface, and the laser Light utilization efficiency can be increased.

  According to a third aspect of the present invention, in the optical pickup device according to the first or second aspect, the light transmitting part is arranged at a position shifted from the optical axis of the objective lens. According to this aspect, since the translucent part is arranged at a position shifted from the central part of the laser light, the central part of the high-intensity laser light can be prevented from leaking out of the objective lens from the translucent part, and the laser light Can improve the efficiency of use.

  According to a fourth aspect of the present invention, in the optical pickup device according to the third aspect, the optical element is arranged so as to be included in a thickness range of the objective lens. According to this aspect, since the optical element (for example, the rising mirror) is accommodated within the thickness range of the objective lens, the size of the optical system in the optical axis direction of the objective lens is considerably reduced.

  According to a fifth aspect of the present invention, in the optical pickup device according to the fourth aspect, the laser light source is arranged such that a light beam of the laser light up to the optical element is included in a thickness range of the objective lens. It is characterized by. According to this aspect, since the light beam of the laser light from the laser light source to the optical element is contained within the thickness range of the objective lens, the size of the optical system in the optical axis direction of the objective lens can be further reduced.

  According to a sixth aspect of the present invention, in the optical pickup device according to the fourth or fifth aspect, the laser light source and the optical element are installed on a common installation surface orthogonal to the optical axis of the objective lens. It is characterized by being. In this way, since the laser light source and the optical element (for example, the rising mirror) are accommodated within the thickness range of the objective lens, the size of the optical system in the optical axis direction of the objective lens can be significantly reduced.

  As described above, according to the present invention, it is possible to provide an optical pickup device capable of significantly reducing the size of the optical system in the optical axis direction of the objective lens. Further, the laser beam emitted from the laser light source can be efficiently guided to the recording medium.

The features of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely an example when the present invention is implemented, and the present invention is not limited to what is described in the following embodiment.

  FIG. 1 shows a configuration of an optical system of the optical pickup device according to the embodiment.

  As shown in the figure, this optical system includes an objective lens 100, a laser diode 201, an optical path changing element 202, and a rising mirror 203. The objective lens 100, the laser diode 201, the optical path changing element 202, and the rising mirror 203 are accommodated in the holder 301. The holder 301 is provided with a coil 302 for focus servo and tracking servo. A magnetic field is applied to the coil 302 from a magnetic circuit (not shown). The holder 301 is supported by a suspension wire or the like so as to be displaceable in the focus direction and the tracking direction.

  A reflective surface 101 is formed on the surface of the objective lens 100 opposite to the exit surface 102 by sputtering or the like. An opening 101a without a reflective film is disposed on a part of the reflective surface 101. The opening 101a is formed, for example, by masking the region when forming a reflective film by sputtering.

  A curved surface 102b (not shown in FIG. 1) projecting inward of the objective lens 100 is formed on the exit surface 102 of the objective lens 100, and a reflecting surface 102a is formed by sputtering or the like on the curved surface 102b. Yes. The shape of the reflective surface 102a is such that the laser light incident from the opening 101a spreads uniformly on the reflective surface 101 as shown in the figure.

  FIG. 2 shows the arrangement positions of the reflecting surface 102a and the opening 101a in the objective lens 100. FIG. 2A and 2B are views of the objective lens as viewed from the exit surface 102 side, and FIGS. 2A and 2B are views of the objective lens as viewed from the reflection surface 101 side. is there. FIG. 9A shows a state before the reflecting surface 102a is formed, and FIG. 10C shows a state before the reflecting surface 101 is formed.

  Referring to FIG. 1A, a curved surface 102 b protruding in the inner direction of the objective lens 100 is formed on the exit surface 102 of the objective lens 100 at a position away from the optical axis O by a distance D1. A reflective film is formed on the curved surface 102b, and a reflective surface 102a is formed as shown in FIG.

  Referring to FIG. 8C, a mask is disposed on the surface of the objective lens 100 opposite to the exit surface 102 in the region where the opening 101a is separated from the optical axis O by a distance D2 (D2> D1). . As illustrated, the arrangement position of the opening 101a and the arrangement position of the reflecting surface 102b are aligned on the same diameter. In this state, the reflective surface 101 is formed from above the mask, and then the mask is removed. As a result, an opening 101a is formed on the reflecting surface 101 as shown in FIG.

  Returning to FIG. 1, a substrate 206 is disposed in the holder 301, and a substrate 205 is further disposed on the substrate 206. The upper surface of the substrate 205 is a surface perpendicular to the optical axis of the objective lens 100, and the laser diode 201, the optical path changing element 202, and the rising mirror 203 are mounted on this surface. In addition, a photodetector 204 is embedded in the substrate 205. Further, a pedestal 207 for mounting the objective lens 100 is disposed on the upper surface of the substrate 206. The upper surface of the pedestal 207 has a curved surface shape similar to the curved surface shape of the reflecting surface 101.

  FIG. 3 is a diagram illustrating an optical system generation process.

  FIG. 4A is a diagram showing components generated using a semiconductor manufacturing process. In this generation step, first, a substrate 206 having a recess 206a into which the base 207 is fitted is generated on the upper surface. Next, the substrate 205 is generated on the upper surface of the substrate 206. At this time, the photodetector 204 is generated at the same time, and the recess 206b for fitting the optical path changing element 202 and the rising mirror 203 is generated. Thereafter, the laser diode 201 is generated on the upper surface of the substrate 205. As a result, the components shown in FIG.

  Next, as shown in FIG. 5B, the base 207 is mounted in the recess 206a, and the optical path changing element 202 and the rising mirror 203 are mounted in the recess 206b. Note that the pedestal 207 and the rising mirror 203 may be formed using a semiconductor manufacturing process. Thereafter, the objective lens 100 is mounted on the base 207 as shown in FIG. At this time, the objective lens 100 is rotated back and forth and left and right with the reflecting surface 101 of the objective lens 100 placed on the pedestal 207, and the objective lens 100 is adjusted to a position where the laser light is properly incident from the opening 101a. . After such adjustment, the objective lens 100 is fixed to the substrate 207 with an adhesive.

  FIG. 4 is an enlarged view showing a portion from the laser diode 201 to the opening 101a. FIG. 4A is a side view, and FIG. 4B is a top view.

  The optical path changing element 202 is configured by integrating a polarization selective diffraction element 202a and a quarter wavelength plate 202b. The polarization direction of the laser light emitted from the laser diode 201 is a direction not subjected to the diffraction action by the diffraction element 202a. Therefore, this laser beam passes through the diffraction element 202a without being changed in the optical path, and enters the quarter-wave plate 202b, where it is converted into circularly polarized light. Thereafter, the laser light is reflected by the rising mirror 203 and enters the objective lens 100 through the opening 101a.

  Returning to FIG. 1, the laser light thus incident on the objective lens 100 is guided to the reflection surface 102a and reflected. The reflected laser light is uniformly guided to the mirror surface 101 by the curved surface shape of the reflecting surface 102a. Thereafter, the laser beam is reflected by the mirror surface 101 and converged. Thereafter, the laser beam is further converged by the emission surface 102 and condensed on the recording layer in the disc. The laser beam reflected by the recording layer in the disc travels back along the optical path and enters the optical path changing element 202.

  Referring to FIG. 4 again, laser light (reflected light from the disk) incident on optical path changing element 202 is converted into linearly polarized light by quarter wavelength plate 202b. At this time, the polarization direction of the laser light is a direction orthogonal to the polarization direction of the laser light emitted from the laser diode 201. For this reason, the laser light (reflected light from the disk) is diffracted by the diffraction element 202a, the optical path is changed, and is incident on the photodetector 204 as shown in FIG.

  Here, the diffraction pattern of the diffractive element 202a is adjusted to a pattern that gives an astigmatism action to the laser light in addition to the optical path changing action. Due to the action of the diffraction element 202a, the laser light (reflected light from the disk) is converged on the photodetector 204 having the four-divided sensor with astigmatism. The focus error signal and push-pull signal (tracking error) are calculated by processing the output from the quadrant sensor in accordance with a focus error signal generation method based on the astigmatism method and a push-pull signal generation method based on the push-pull method. Signal) is generated.

  FIG. 5 is a diagram showing dimensions in the optical axis direction of the objective lens 100 of the optical system according to the present embodiment. According to the present embodiment, since the laser diode 201, the optical path changing element 202, and the rising mirror 203 are disposed within the thickness range of the objective lens 100, the thickness of the optical system is the same as the thickness of the objective lens 100. Become. Therefore, the dimension of the optical system in the optical axis direction of the objective lens 100 can be significantly reduced, and the optical pickup device can be significantly downsized.

  In addition, since the laser diode 201 is disposed in the immediate vicinity of the objective lens 100, the beam width of the laser light when entering the objective lens 100 can be considerably reduced. For this reason, the opening 101a and the reflective surface 102a can be made small, and the light quantity loss of the laser by the opening 101a and the reflective surface 102a can be suppressed. That is, a part of the laser light reflected by the reflecting surface 102a is emitted to the outside from the opening 101a, and a part of the laser light reflected by the reflecting surface 101 is blocked by the reflecting surface 102a. . Therefore, if the opening 101a and the reflection surface 102a are large, the amount of laser light leaking to the outside from the opening 101a and the amount of laser light blocked by the reflection surface 102a increase, and the amount of laser light loss increases. On the other hand, in the present embodiment, since the opening 101a and the reflecting surface 102a can be made small, it is possible to suppress the light amount loss of the laser due to the opening 101a and the reflecting surface 102a, and to improve the utilization efficiency of the laser beam.

  Furthermore, according to the present embodiment, since the laser beam is converged by utilizing the reflection action on the reflection surface 101, the emission surface 102 and the incident surface (the surface on which the reflection surface 101 is formed) like a normal objective lens. The chromatic aberration can be suppressed as compared with the case where the laser beam is converged by the two refraction actions when passing through (). Therefore, according to the present embodiment, even if the wavelength of the laser beam varies due to, for example, temperature change or output power switching, it is possible to suppress degradation of the laser beam due to wavelength variation.

  In addition, according to the present embodiment, since the reflecting surface 102a is arranged at a position shifted by the distance D1 (see FIG. 2) from the central portion of the laser light (the optical axis of the objective lens 100), the high-intensity laser The central portion of the light can be prevented from being blocked by the reflecting surface 102a, and the utilization efficiency of the laser light can be increased. Note that, as the distance D1 in FIG. 2 is separated from the optical axis of the objective lens 100, the position of the reflecting surface 102a is further away from the center of the laser light, so that the utilization efficiency of the laser light can be improved.

  Furthermore, according to the present embodiment, since the opening 101a is arranged at a position shifted by the distance D2 (see FIG. 2) from the central portion of the laser beam (the optical axis of the objective lens 100), the high-intensity laser beam The central portion can be prevented from leaking out of the objective lens 100 from the opening 101a, and the utilization efficiency of laser light can be increased. Also in this case, as the distance D2 in FIG. 2 is separated from the optical axis of the objective lens 100, the position of the opening 101a is further away from the center of the laser light, so that the utilization efficiency of the laser light can be improved.

  Although the present embodiment has been described above, the present invention is not limited to the above-described embodiment, and the embodiment of the present invention can be variously modified in addition to the above.

  For example, in the above-described embodiment, the optical system including the objective lens 100, the laser diode 201, the optical path changing element 202, and the rising mirror 203 is arranged in the holder 301 in only one system. It is also possible to provide a compatible optical pickup device that can be applied to different types of disks. In this case, each system laser diode emits laser light having a different wavelength depending on the corresponding disk.

  In the above embodiment, the laser diode 201 is arranged so that the optical axis of the emitted laser light is orthogonal to the optical axis of the objective lens 100. However, the optical axis of the emitted laser light is a predetermined angle in the vertical direction from the state of FIG. The laser diode 201 may be arranged so as to be tilted only. Also in this case, since the laser diode 201 can be disposed within the thickness range of the objective lens 100 when the laser diode 201 is disposed such that the optical axis of the emitted laser light is inclined upward from the state of FIG. Can be reduced in thickness.

  Further, in the above embodiment, the reflective surface 102a is formed so as to protrude inside the objective lens 100, but conversely, the reflective surface 102a can be formed so as to protrude outside the objective lens 100. In this case, the laser light reflected by the reflecting surface 102 a once converges inside the objective lens 100 before reaching the reflecting surface 101, and then spreads and is uniformly guided to the reflecting surface 101.

  Furthermore, in the above embodiment, the opening 101a and the reflecting surface 102a are arranged at a position where the laser beam passes, but if possible in optical design, both the opening 101a and the reflecting surface 102a or a position where the laser beam does not pass or Either one may be arranged. In this way, the laser light is not subject to loss of light quantity by the opening 101a or the reflecting surface 102a, so that the utilization efficiency of the laser light can be improved. When the opening 101a is arranged at a position where the laser beam does not pass, the laser beam is not incident on the position in the first place, so that the reflecting surface 101 is not necessary. Therefore, in this case, the opening 101a is not formed in the reflecting surface 101, but rather, the laser light enters the objective lens from a region where the reflecting surface 101 is not formed. This region also corresponds to the light transmitting portion of the present invention, like the opening 101a in the above embodiment.

  Further, in the above embodiment, the opening 101a and the reflecting surface 102a are arranged so as to be aligned in the radial direction of the objective lens 100 (on one straight line perpendicular to the optical axis of the objective lens 100). Is not necessarily arranged in this manner, and the laser beam that has passed through the opening 101a is reflected by the reflecting surface 102a, so that the laser beam can be properly guided to a predetermined region on the reflecting surface 101. Just do it.

  In addition, the embodiment of the present invention can be variously modified as appropriate within the scope of the technical idea shown in the claims.

The figure which shows the structure of the optical pick-up apparatus which concerns on embodiment The figure which shows the structure of the objective lens which concerns on embodiment The figure which shows the production | generation process of the optical system which concerns on embodiment The figure which expands and shows a part of optical system which concerns on embodiment The figure which shows the dimension of the optical axis direction of the objective lens of the optical system which concerns on embodiment The figure which shows the dimension of the optical axis direction of the objective lens of the optical system which concerns on a prior art The figure which shows the structure of patent document 1

Explanation of symbols

100 objective lens 101 reflecting surface (first reflecting surface)
101a Opening (translucent part)
102 exit surface 102a reflective surface (second reflective surface)
201 Laser diode 203 Rising mirror 205 Substrate 301 Holder

Claims (6)

A laser light source for emitting laser light;
An objective lens for converging the laser beam on a recording medium,
The objective lens is
A first reflecting surface formed on a surface opposite to the exit surface;
A translucent part formed on the first reflecting surface and through which the laser beam can pass;
A second reflecting surface that guides the laser light incident through the light transmitting portion to the first reflecting surface;
And an optical element for directing laser light emitted from the laser light source from the translucent portion to the second reflecting surface,
After being reflected by the second reflecting surface, the first reflecting surface and the second reflecting surface so that the laser beam reflected by the first reflecting surface is converged on the recording medium by the emitting surface. The surface shape of the reflecting surface and the exit surface is adjusted,
The laser light source, the objective lens and the optical element are integrally accommodated by a holder,
An optical pickup device characterized by that. In claim 1,
The second reflecting surface is disposed at a position shifted from the optical axis of the objective lens.
An optical pickup device characterized by that. In claim 1 or 2,
The translucent part is arranged at a position shifted from the optical axis of the objective lens,
An optical pickup device characterized by that. In claim 3,
The optical element is disposed so as to be included in the thickness range of the objective lens,
An optical pickup device characterized by that. In claim 4,
The laser light source is arranged so that the light beam of the laser light up to the optical element is included in the thickness range of the objective lens,
An optical pickup device characterized by that. In claim 4 or 5,
The laser light source and the optical element are installed on a common installation surface orthogonal to the optical axis of the objective lens,
An optical pickup device characterized by that.

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