JP2005196859A - Optical pickup device and optical disk device - Google Patents

Abstract

Provided are an optical pickup device and an optical disk device that can realize a reduction in thickness, size, and suppression of deterioration of characteristics even in response to lasers of various wavelengths including a blue laser.
A beam diameter enlarging means comprises a first optical lens disposed between the optical means and the first light condensing means, and a second optical lens disposed between the optical means and the first optical unit. The first optical lens is shared by the optical system having the first wavelength and the optical system having a wavelength longer than the first wavelength. For the first wavelength, The chromatic aberration for correcting the chromatic aberration of the first condensing unit is generated, and the chromatic aberration for correcting the chromatic aberration of the second condensing unit is generated for light having a wavelength longer than the first wavelength. It was done.
[Selection] Figure 1

Description

  The present invention relates to an optical pickup device and an optical disc device used for recording and reproduction on an optical disc such as a high-density recording disc such as HD-DVD and DVD, and a compact disc.

In optical disk devices, laser diodes that emit long-wavelength lasers such as infrared lasers and red lasers have been used. Recently, however, blue lasers have been used for higher-density recording than when using the above-mentioned long-wavelength lasers. Has come to do.
JP 11-224436 A JP 2000-123394 A JP-A-10-334494

  Video recorders that record and play back optical discs that use blue lasers are very large when recording and playing back both optical discs that are compatible with blue lasers and optical discs that are compatible with red lasers. Since the optical system can be configured in the apparatus, there is no particular problem.

  However, at least one of recording and reproduction can be performed on two or more optical disks having different wavelengths, and a relatively thin and small optical disk drive device incorporated in an electronic device such as a notebook personal computer has a blue laser. It is impossible to provide an optical system corresponding to each light of infrared laser, infrared laser, and red laser, and the optical system using a blue laser has a larger spherical aberration generation than other laser optical systems, and a common optical system. It is very difficult to process the optical system, and the optical characteristics are deteriorated by integrating the optical system.

  The present invention solves the above-mentioned conventional problems, and can be reduced in thickness and size even in response to lasers of various wavelengths including a blue laser, and can realize reduction of optical characteristic deterioration associated therewith. And an optical disc apparatus.

  The present invention includes a first optical unit that emits light having a first wavelength, a second optical unit that emits at least one light having a wavelength longer than the first wavelength, and the first wavelength. And optical means for guiding light having a wavelength longer than the first wavelength to substantially the same optical path, first condensing means for condensing light of the first wavelength from the optical means on the optical disc, A second condensing unit that condenses light having a wavelength longer than the first wavelength on the optical disc; and a beam diameter enlarging unit that expands a beam diameter of the light having the first wavelength. Is composed of a first optical lens disposed between the optical means and the first condensing means, and a second optical lens disposed between the optical means and the first optical unit, The first optical lens includes an optical system of light having the first wavelength and the first optical lens. The optical system is shared by an optical system having a wavelength longer than the wavelength, and generates chromatic aberration for correcting chromatic aberration of the first condensing means for the light having the first wavelength. For light having a longer wavelength, chromatic aberration for correcting the chromatic aberration of the second condensing means is generated.

  According to the present invention, the optical component is shared between the optical system having the first wavelength and the optical system having a wavelength longer than the first wavelength, thereby enabling the device to be thinned and miniaturized. By providing a means for preventing deterioration of optical characteristics caused by sharing of an optical system, at least one of recording and reproduction can be performed on two or more optical disks having different wavelengths, and electronic devices such as notebook personal computers can be used. It is possible to realize a thin and small optical disk drive device to be incorporated.

  The invention according to claim 1 is a first optical unit that emits light having a first wavelength, and a second optical unit that emits at least one light having a second wavelength longer than the first wavelength. Optical means for guiding the first wavelength light and the second wavelength light longer than the first wavelength to substantially the same optical path, and collecting the first wavelength light from the optical means on the optical disc. First condensing means for emitting light, and second condensing means for condensing light having a wavelength longer than the first wavelength on the optical disc, and at least the first condensing means in the optical path of the light having the first wavelength An optical pickup device provided with chromatic aberration correction means for generating chromatic aberration for correcting chromatic aberration of the first light collecting means with respect to light of one wavelength, which enables downsizing and thinning of the apparatus To.

  The invention according to claim 2 is the optical pickup device according to claim 1, wherein the chromatic aberration correcting means is provided in an optical path through which light of both the first wavelength and the second wavelength passes. The optical system can be shared, and the apparatus can be reduced in size and thickness.

  According to a third aspect of the present invention, the chromatic aberration correction means has high chromatic aberration performance for the first wavelength light, and the chromatic aberration correction performance for the second wavelength light is the first wavelength. The optical pickup device according to claim 2, wherein the optical system can be shared, and the device can be reduced in size and thickness.

  According to a fourth aspect of the present invention, as a chromatic aberration correcting means, a convex lens having a positive power and a concave lens having a negative power are joined together to form an outwardly convex lens and an optical lens having a total positive power The optical pickup device according to claim 2, wherein the optical system can be shared, and the device can be reduced in size and thickness.

  The invention according to claim 5 is the optical pickup device according to claim 1, wherein the chromatic aberration correcting means is provided between the optical means and the first and second light collecting means. Enables thinning.

  The invention according to claim 6 is the optical pickup device according to claim 1, wherein the chromatic aberration correcting means is arranged in an optical path constituted only by the light of the first wavelength. Make it possible.

  The invention according to claim 7 is characterized in that chromatic aberration correcting means is provided in at least one of the first light path of the first light source unit and the optical means or between the first and second light collecting means. Item 6. The optical pickup device according to Item 6, wherein the device can be reduced in size and thickness.

  The invention described in claim 8 is the optical pickup device according to claim 6, wherein a hologram element is used as the chromatic aberration correcting means, and the device can be reduced in size and thickness.

The invention according to claim 9 is a first optical unit that emits light having a first wavelength, a second optical unit that emits at least one light having a wavelength longer than the first wavelength, and Optical means for guiding light of a first wavelength and light of a wavelength longer than the first wavelength to substantially the same optical path;
First condensing means for condensing light of a first wavelength from the optical means on an optical disc, second condensing means for condensing light of a wavelength longer than the first wavelength on the optical disc, A beam diameter enlarging means for enlarging a beam diameter of light having a first wavelength, and the beam diameter enlarging means is disposed between the optical means and the first condensing means. Means and a second optical lens disposed between the first optical unit, and the first optical lens includes an optical system of the first wavelength light and the first wavelength. Is shared by the optical system having the long wavelength, and the chromatic aberration for correcting the chromatic aberration of the first condensing unit is generated for the light having the first wavelength, which is longer than the first wavelength. For light of a wavelength, chromatic aberration that corrects chromatic aberration of the second condensing means is generated. The optical pickup device is characterized in that even when the chromatic aberration characteristics of the first light collecting means and the second light collecting means are greatly different, the optical components can be shared, and the apparatus can be reduced in size and thickness. Can be realized.

  According to a tenth aspect of the present invention, the first condensing means is a refractive lens, and the second condensing means is a diffractive / refractive composite lens in which a diffraction grating is provided on the surface of the refractive lens. And the first optical lens generates chromatic aberration for correcting chromatic aberration of the first condensing means for the light of the first wavelength, and has a wavelength longer than the first wavelength. 10. The optical pickup device according to claim 9, wherein the amount of chromatic aberration generated for light is 0.1 [mu] m / nm or less, and is a refraction type lens having large chromatic aberration and diffraction / refraction having very small chromatic aberration. Even when a compound lens is used, the first optical lens of the beam expanding means that occupies a large area can be shared by optical systems having different wavelengths, and the apparatus can be reduced in size and thickness.

  According to an eleventh aspect of the present invention, the first condensing means is a refractive lens formed of a glass material, and the second condensing means is a resin in which a diffraction grating is provided on the surface of the refractive lens. It is a diffractive / refractive composite lens formed of a material, and the first optical lens is zero in the direction of correcting the chromatic aberration of the first condensing means for the light of the first wavelength. The chromatic aberration generation amount is 0.1 μm / nm or less for light having a wavelength of .3 μm / nm or more and a wavelength longer than the first wavelength. Even when a refractive lens having a large chromatic aberration and a combined diffractive / refractive lens having a very small chromatic aberration are used as an optical pickup device, the first optical lens of the beam expanding means that occupies a large place is an optical system having a different wavelength. Can be shared with The device can be made smaller / thinner.

  According to a twelfth aspect of the present invention, the first optical lens is formed by bonding a convex lens made of a glass material having a small refractive index dispersion (a large Abbe number) and a concave lens made of a glass material having a large refractive index dispersion (a small Abbe number). A doublet lens having a positive power as a whole, and designed to generate a predetermined chromatic aberration and minimize a spherical aberration with respect to the light of the first wavelength, 12. The optical pickup device according to claim 10, wherein the optical pickup device is designed to minimize the amount of chromatic aberration generated for light having a wavelength longer than one wavelength. The configuration makes it possible to implement the invention according to claim 11.

  According to a thirteenth aspect of the present invention, the first optical lens is formed by bonding a convex lens made of a glass material having a small refractive index dispersion (large Abbe number) and a concave lens made of a glass material having a large refractive index dispersion (small Abbe number). A doublet lens having a positive power as a whole, and designed to generate a predetermined chromatic aberration and minimize a spherical aberration with respect to the light of the first wavelength, For light having a wavelength longer than 1, the amount of chromatic aberration is designed to be minimized, and the spherical surface of the first optical lens is added to an optical system having a wavelength longer than the first wavelength. 13. The optical pickup device according to claim 12, wherein a coupling lens that corrects aberration is provided, and the coupling lens is provided to provide the optical pickup device according to claim 12. Design of first optical lens is facilitated.

According to a fourteenth aspect of the present invention, the laser diode mounted on the first optical unit emits substantially blue to substantially violet light, and the laser diode mounted on the second optical unit starts from approximately infrared. 6. The optical pickup device according to claim 1, wherein the optical pickup device emits substantially red light, and a small / thin optical pickup device capable of supporting three wavelengths of blue, red, and infrared can be realized. .

  According to a fifteenth aspect of the present invention, there is provided driving means for rotating an optical disk, and a carriage mounted with the optical pickup device according to any one of the first to fourteenth aspects so as to be movable with respect to the driving means. In this optical disk apparatus, a small / thin optical pickup apparatus capable of supporting three wavelengths of blue, red, and infrared can be realized.

  Hereinafter, an optical pickup device according to a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view showing an optical pickup device according to one embodiment of the present invention, and FIG. 2 is a side view of the optical pickup device according to one embodiment of the present invention.

  1 and 2, reference numeral 1 denotes an optical disk. The optical disk 1 is irradiated with light so that at least one of information reproduction and information recording can be performed. Specifically, the optical disc 1 is a CD-ROM disc, a DVD-ROM disc, etc. that can only reproduce information, and a CD-R disc, a DVD-R disc, etc. that can record information in addition to the reproduction of information. In addition to the above, a CD-RW disc, a DVD-RW disc, a DVD-RAM disc or the like capable of recording / erasing information is preferably used. The optical disk 1 includes a recording layer that can record and / or reproduce information with substantially red light, a recording layer that can record and / or reproduce information with substantially infrared light, and substantially blue to approximately. Those having a recording layer capable of recording or reproducing information with blue-violet light can be used. Furthermore, as the size of the optical disk 1, it is possible to use disk-shaped ones having various diameters, but a disk-shaped one having a diameter of 3 cm to 12 cm is preferably used.

  Reference numeral 2 denotes a spindle motor for rotating the optical disc 1. The spindle motor 2 is provided with a chucking portion (not shown) that holds the optical disc 1. The spindle motor 2 can rotate the optical disk 1 at a constant angular velocity or variably rotate the angular velocity. How to control the angular velocity constantly or variably is switched according to the situation by a spindle motor driving means and a control unit of the optical disc apparatus which are not shown. In the present embodiment, the spindle motor 2 is used as the rotation driving means of the optical disc 1, but it may be rotated by using other types of motors or other means.

  Reference numeral 3 denotes an optical pickup for recording information on the optical disc 1 and reading information from the optical disc 1 by irradiating the optical disc 1 with light.

  Reference numeral 4 denotes a carriage serving as a base of the optical pickup 3, and 5 denotes an optical pickup actuator that moves an objective lens (to be described later) in a substantially three-dimensional manner. The carriage 4 is supported by at least a support shaft 6 and a guide shaft 7 and can move between the inner periphery and the outer periphery of the optical disc 1. The carriage 4 is equipped with an optical pickup actuator 5 and an optical unit or a light source.

  Reference numeral 8 denotes a first optical unit including a blue-violet laser unit 81, a light receiving element unit 82, and a front light monitor unit 500, and details will be described with reference to FIG. The laser unit 81 includes a laser diode 81a that generates laser light having a first wavelength of about 405 nm. The laser diode 81a is disposed in a space formed by the base 81b.

  In this embodiment, the laser diode 81a that emits blue-violet light is used. However, a laser diode that emits blue to purple light may be used. As such a laser diode that emits a laser beam with a short wavelength, an active layer in which an emission center such as In is added to GaN is used as a main component, a p-type layer doped with p-type impurities as a main component, and GaN as a main component. And sandwiched between n-type layers doped with n-type impurities are preferably used. A so-called nitride semiconductor laser is preferably used.

  The base 81b is provided with a plurality of terminals 81c. The terminal 81c includes a ground terminal and a terminal for supplying current to the laser diode 81a.

  A prism 83 is directly attached to the base 81b by a technique such as adhesion on the base 81b. The prism 83 transmits the laser beam 84 emitted from the laser diode 81a to irradiate the optical disc 1 and also emits light from the optical disc 1. This is a prism that guides the return light to the light receiving element portion 82. The prism 83 is provided with a polymer film 83 c for monitoring the laser light 84, and is configured to reflect a part of the laser light 84 to the front light monitor 500 and monitor the output level of the laser light 84. . Further, a diffraction grating (not shown) for dividing the laser beam 84 having a wavelength of about 405 nm is further provided at the position led to the light receiving element portion 82 side, and focus detection, tracking detection, spherical aberration detection, and recording on the optical disc 1 are performed. The detected signal and the control signal can be taken out. In the present embodiment, a transparent cover member 83a is provided between the prism 83 and the base 81b. The cover member 83a is directly joined to the base 81b using a technique such as adhesion. The prism 83 is provided with inclined surfaces 83b to 83d that are substantially parallel and inclined to each other, and optical elements such as a beam splitter film and a hologram are disposed on the inclined surfaces 83b to 83d. The inclined surfaces 83b to 83d correspond to joint surfaces such as transparent glass blocks and resin blocks. Specifically, on the inclined surface 83b, a hologram for focus detection, tracking detection, spherical aberration detection, detection of a signal recorded on the optical disc 1, and extraction of a control signal is formed. A polarizing beam splitter film is formed on the inclined surface 83b, and a part of the P-wave light is also a film that reflects several percent to several tens of percent in order to guide it to the front light monitor 500. The inclined surface 83d is provided with a film that completely transmits light having a wavelength of 405 nm. In this embodiment, three inclined surfaces are provided, but one or more inclined surfaces may be provided. Further, as the diffraction grating provided in the cover member 83a, for example, the intensity distribution of the light emitted from the laser diode 81a is non-uniform (for example, the luminance at the center of the light spot is low and the luminance at the outer periphery is low). May be created). Moreover, you may provide in the inclined surface 83c or the inclined surface 83d, without providing in the cover member 83a. It is preferable to use a light that guides a part of light in an optical axis direction different from the optical axis direction toward the optical disc 1 and uses the guided light for monitor light, for example. Further, when the prism 83 is attached on the cover member 83a by a technique such as bonding, the adhesive protruding outward from the inclined surfaces 83b to 83d, which are bonding surfaces, or the concave portions generated in the inclined surfaces 83b to 83d can be relaxed. That is, when the light emitted from the laser diode 81a hits the concave or convex portions formed on the outer surface portions of the inclined surfaces 83b to 83d by the optical design or the like, the recording / reproducing characteristics are affected. . Therefore, by providing the cover member 83a on the laser diode 81a side of the prism 83, even if the concave portion or convex portion is formed, the concave / convex portion can be alleviated, so that deterioration of recording characteristics and the like can be prevented.

  The light receiving element portion 82 is configured to cover the light receiving element 82a and cover the surface with a transparent glass substrate 82b. In addition, a terminal (not shown) for electrical connection with the light receiving element 82a is led out from the case 82c to the surface of the case 82c. In addition, it is obvious that the light receiving element 82 in a state where the light receiving element 82a is covered with a transparent member that does not deteriorate at a wavelength of 405 nm (blue to blue-violet light) is also possible.

  A coupling member 85 is a member for determining the positions of the laser unit 81 and the light receiving element unit 82, and a member for determining the position of the front light monitor 500. A flexible substrate 86 is joined to a terminal (not shown) of the light receiving element portion 82, and the flexible substrate 86 is coupled to the laser flexible substrate 9 with solder or the like.

  Reference numeral 10 denotes a second optical unit including a red and infrared laser unit 101, a light receiving element unit 102, and a front light monitor 501, which will be described in detail with reference to FIG. The laser unit 101 includes a laser diode 103 that emits laser light having a wavelength of approximately 660 nm longer than the first wavelength and a laser diode 104 that emits laser light having a wavelength of approximately 780 nm. Are arranged in a space constituted by the base 101a.

  In this embodiment, the laser diodes 103 and 104 are arranged as separate light emitter blocks in the space. However, a plurality of light emitting layers are provided in one light emitter block, and one light emitter block is provided. The structure arrange | positioned in space may be sufficient. In this embodiment, laser diodes having two different wavelengths are mounted. However, a configuration in which three or more laser diodes having different wavelengths are provided in the space may be employed.

  The base 101a is provided with a plurality of terminals 101b. The terminal 101b includes a ground terminal, a terminal for supplying current to the laser diodes 103 and 104, an output terminal for monitor light, and the like. A prism 105 transmits the laser beam 106 and guides the return light to the light receiving element 102. The prism 105 is provided with a polymer film 105 c so that the output level of the laser beam 106 can be monitored by reflecting a part of the laser beam 106 to the front light monitor 501. Further, a diffraction grating (not shown) for dividing the laser beam 106 having a wavelength of 780 nm is provided at a position led to the light receiving element 102 side, and focus detection, tracking detection, signals recorded on the optical disc 1 and control signals are provided. Etc. can be detected. The prism 105 is provided with inclined surfaces 105a to 105c that are substantially parallel and inclined to each other, and optical elements such as a beam splitter film and a hologram are disposed on the inclined surfaces 105a to 105c. Specifically, a diffraction grating (not shown) optimally formed at a wavelength of 780 nm is applied to 105a, and P-wave light is transmitted to the inclined surface 105b by a polarizing beam splitter for a wavelength of 780nm. A film that reflects wave light and transmits light having a wavelength of 660 nm is formed. For the wavelength 780 nm, a part of the P wave light is reflected and transmitted by the beam splitter on the inclined surface 105c, and for wavelength 660 nm. A polarizing beam splitter forms a film that reflects and transmits part of the P-wave light and totally reflects the S-wave light. Part of the P-wave light having the wavelengths of 780 nm and 660 nm is guided to the front light monitor.

  The inclined surfaces 105a to 105c correspond to joint surfaces such as transparent glass blocks and resin blocks. Note that although three inclined surfaces are provided in this embodiment, one or more inclined surfaces may be provided.

  Further, if necessary, a diffraction grating (not shown) for forming three beams is formed on the laser unit 101 side of the prism 105 so that one laser wavelength is not influenced by the other wavelength. For example, a three-beam diffraction grating using polarized light is formed.

A coupling member 108 is a member for determining the positions of the laser unit 101 and the light receiving element unit 102 and for determining the position of the front light monitor 501. Reference numeral 109 denotes a diffraction grating having a beam combiner function, which does not operate at a wavelength of 660 nm but operates at a wavelength of 780 nm, so that an apparent virtual light emitting point with a wavelength of 780 nm coincides with a virtual light emitting point with a wavelength of 660 nm. It has become. Further, 109 can be optically acceptable without having the beam combiner function.

  The diffraction grating 109 has a structure in which a plurality of plate-like bodies are laminated, and at least one of the plurality of plate-like pairs is provided with a grating. Further, it is directly bonded to the base 101a by a technique such as adhesion.

  The light emitted from either one of the laser diodes 103 and 104 passes through the diffraction grating 109 and the prism 105 and is guided to the optical disc 1, and the reflected light reflected by the optical disc 1 passes through the prism 105 and receives the light receiving element 102. Led to. At this time, the reflected light from the optical disk 1 at the prism 105 is reflected between the inclined surface 105 a and the inclined surface 105 b and enters the light receiving element portion 102.

  In the light receiving element portion 102, the light receiving element 102a is covered with a case 102b including a transparent member, and a terminal 102c electrically connected to the light receiving element 102a is led out of the case 102b from the case 102b. ing.

  A flexible substrate (not shown) is connected to the terminal 102c of the light receiving element portion 102, and is coupled to the laser flexible substrate 9 with solder or the like.

  Reference numeral 11 denotes a collimating lens for a wavelength of 405 nm, which is used to make the diverged laser beam 84 output from the laser unit 81 substantially parallel. The collimating lens 11 also has a function of correcting chromatic aberration that occurs due to the influence of wavelength variation, temperature change, and the like. A beam shaping prism 12 corrects the intensity distribution of the laser beam 84 into a substantially circular shape. A critical angle prism 13 is used to separate the laser beam 84. An aberration correction mirror 14 is used to correct spherical aberration caused by a thickness error of the optical disk 1 or the like.

  Here, the aberration correction mirror will be described with reference to FIGS.

  FIGS. 5A to 5C are a schematic plan view (top surface), a sectional view taken along a broken line AB, and a plan view (top view) of the aberration correction mirror used in the optical pickup according to this embodiment. It is sectional drawing in a lower surface. A lower electrode 16, a piezoelectric body 17, upper electrodes 18 and 19, and an elastic body 20 are formed on the substrate 15. The substrate 15 has a circular cavity portion 21 on the back side (lower side in the drawing), and a reflective film 22 is formed. The lower electrode 16 is patterned and routed to the electrode pad 23. Similarly, the upper electrodes 18 and 19 are also patterned and routed to the electrode pads 24 and 25, respectively.

  FIG. 6 shows the configuration of the upper electrodes 18 and 19. The upper electrodes 18 and 19 are insulated from each other by the insulating portion 26. In this example, the upper electrode 18 is circular, and the upper electrode 18 is an annular electrode whose center is substantially the same as the upper electrode 18. Wiring is routed from the upper electrode 18 and connected to the electrode pad 24. Similarly, wiring is routed from the upper electrode 19 to the electrode pad 25. In the present embodiment, the upper electrodes 18 and 19 are divided into two parts, but may be divided into three or more, and in this embodiment, the upper electrodes 18 and 19 have a circular outer shape. However, it may be a rectangular shape, a quadrangular or more polygonal shape, or a triangular shape.

  FIG. 7 shows the configuration of the lower electrode. The lower electrode 16 sandwiches the piezoelectric body 17 together with the upper electrodes 18 and 19, and the lower electrode 16 is wired to the electrode pad 23.

In this configuration, when the lower electrode 16 is grounded, a positive voltage is applied to the upper electrode 18, and a negative voltage is applied to the upper electrode 19, the displacement contour line (a) and displacement diagram (b) of the reflective film 22 are shown. As shown in FIG. In the drawing, C, C ′, D, and D ′ correspond to the positions of the insulating portion 26 and the outer peripheral portion of the cavity portion 21, respectively. The positions of D and D ′ are the outer peripheral portion of the cavity portion 21, and since this outer peripheral portion is restrained, the displacement is zero. The displacement is convex downward at the annular portion corresponding to CD and C′-D ′, and convex upward at the portion corresponding to the diameter of CC ′ with the boundary of C and C ′ as the boundary. Although correction of spherical aberration generally requires an aspheric shape, the curved surface shape at CC ′ is exactly an aspheric shape. Therefore, in the present invention, the curved surface portion in CC ′, that is, the portion of the reflective film 22 corresponding to the shape of the upper electrode 18 or the inside thereof is used. Thus, the aberration correction mirror is a functional component that can realize aberration correction with extremely high accuracy. In this embodiment, the aberration correction mirror using the thin film-formed piezoelectric body 17 is provided. However, the aberration correction mirror may be formed of a bulk-shaped piezoelectric body, or may be corrected using other displaceable members. The mirror may be driven. Further, spherical aberration can be corrected by combining a plurality of lenses and moving at least one of the plurality of lenses without using the piezoelectric body 17.

  Next, reference numeral 27 denotes a beam splitter, which is an optical unit that guides light having the first wavelength and light having a wavelength longer than the first wavelength to substantially the same optical path, and is emitted from the integrated element 8 and the integrated element 10. The laser beam 84 and the laser beam 106 are separated and combined, and the phase of the laser beam 84 is aligned. On the integrated element 8 side, a λ / 4 plate 502 is attached to the wavelength 405 nm by means such as adhesion.

  Reference numerals 29 and 30 denote convex lenses, and the convex lenses 29 and 30 constitute beam diameter expanding means for expanding the beam diameter of the light having the first wavelength. The convex lens 30 is a first optical lens disposed between the optical unit and the first light collecting unit, and the convex lens 29 is a second optical unit disposed between the optical unit and the first optical unit. It is an optical lens. The convex lens 29 is a convex lens having positive power, and the convex lens 30 is a convex lens having positive power. The combination of the convex lens 29 and the convex lens 30 expands the laser beam 84 to a desired beam diameter. Further, the laser beam 84 is once focused between the convex lenses 29 and 30. In this way, once the focal point is formed between the convex lens 29 and the convex lens 30, and the focal length of the convex lens 29 and the distance between the convex lens 29 and the aberration correcting mirror are substantially matched, the aberration correcting mirror 14 is used for correcting spherical aberration. It is possible to suppress FFP distribution fluctuations in the objective lens unit due to the generated divergent light and convergent light. When the aberration correction mirror 14 is not used, a configuration in which the convex lens 29 is a concave lens is also possible.

  Reference numeral 28 denotes a coupling lens for wavelengths of 660 nm and 780 nm, which is used in combination with the convex lens 30 to make the divergent laser beam 106 output from the laser unit 101 substantially parallel. It is also possible to have a function of correcting chromatic aberration that occurs due to the influence of wavelength variation, temperature change, and the like.

  Reference numeral 31 denotes an upright prism, which has a function of reflecting the first surface 311 with respect to the laser light 106 having wavelengths of 660 nm and 780 nm, and forming a dielectric multilayer film having a function of transmitting and refracting the wavelength 405 nm. ing. Further, the second surface 312 can reflect 405 nm, and has a configuration in which the phases are aligned. In this way, by configuring the rising prism 31 with a single prism, it is possible to increase the rigidity of an actuator described later.

Reference numeral 32 denotes an objective lens for an optical disc (DVD) 1 corresponding to a wavelength of 660 nm. The objective lens 32 also focuses on a desired recording position with parallel light on the optical disc (CD) 1 corresponding to a wavelength of 780 nm. It is a resin-made diffractive / refractive composite objective lens having a function capable of performing. The objective lens 32 has a small chromatic aberration of 0.1 μm / nm or less because the chromatic aberration of diffraction action and the chromatic aberration of refraction action cancel each other. On the other hand, 33 is an objective lens for the optical disc 1 corresponding to a wavelength of 405 nm. In consideration of light resistance to blue light, the objective lens 33 is normally a refractive glass lens and has a large chromatic aberration of 0.3 μm / nm or more. In the embodiment, the objective lens 32 is arranged at the spindle motor center position, and the objective lens 33 is arranged on the side opposite to the first convex lens 30 with respect to the objective lens 32, that is, in the tangential direction with respect to the optical disc 1. ing. Further, the objective lens 33 is configured to be thicker than the objective lens 32. As in the present embodiment, the light emitted from the light source first raises the light having a relatively long wavelength on the first surface 311, and then passes the light having the relatively short wavelength after passing through the first surface 311. In the configuration of rising on the surface 312, that is, the configuration shown in FIG. By doing so, it is possible to lengthen the path for the light to be routed until it is relatively incident on the rising prism 31 and to facilitate the optical design.

  However, the first surface 311 surface of the rising prism 31 transmits the laser light 106 having a wavelength of 660 nm and 780 nm, reflects the laser light 84 having a wavelength of 405 nm, and the second surface 312 surface reflects the laser light 106 having a wavelength of 660 nm and 780 nm. The objective lens 33 can be configured even if it is arranged on the laser side with respect to the objective lens 32 as long as it reflects the light (see FIGS. 11 and 12).

  Reference numeral 34 denotes an aperture hologram. The aperture hologram includes at least an aperture filter for realizing a necessary numerical aperture for accommodating CD and DVD optical discs and a polarization hologram that reacts to the DVD light. Reference numeral 34 is realized by means such as a dielectric multilayer film, a hologram aperture, and the aperture hologram 34 is capable of detecting focus detection, tracking detection, signals described on the optical disc 1 and the like for DVD light. . The aperture filter 34 is integrally provided with a λ / 4 plate corresponding to wavelengths of 660 nm and 780 nm, and the polarization direction is polarized by approximately 90 degrees in the forward path and the return path.

  Next, the optical configuration of the optical pickup in the present embodiment will be described.

First, the wavelength 405 nm will be described. The divergent laser beam 84 having a wavelength of 405 nm emitted from the laser unit 81 is substantially parallel by the collimator lens 11, passes through the beam shaping prism 12, and passes through the critical angle prism 13 to have an aberration correction mirror 14 having a reflection mirror function. To reach. The laser beam 84 reflected from the aberration correction mirror 14 enters the critical angle prism 13 again. At this time, the incident light and the reflected light entering the aberration correction mirror 14 are arranged so as to have an inclination of several degrees before and after the critical angle prism 13. A gap is provided between the critical angle prisms 13a and 13b. With this configuration, it becomes possible to efficiently separate the laser beam 84 having a wavelength of 405 nm using the critical angle. Further, it is possible to improve the light transmission efficiency on both surfaces of the critical angle prisms 13a and 13b facing the gap by means such as a dielectric multilayer film. Next, the laser beam 84 emitted from the critical angle prism 13 is collected by the convex lens 29, which is a second optical lens having a positive power, and again passes through the λ / 4 plate 502 as a divergent light to be circularly polarized. It becomes. Next, the light passes through the beam splitter 27, enters the rising prism 31 through the first optical lens 30, passes through the first surface 311, is refracted by the second surface 312, and the third surface 313 is reflected. Refractive through. The reflected laser beam 84 is condensed by the objective lens 33 to form a light spot on the optical disc 1. The laser beam 84 returning from the optical disk 1 passes in the opposite direction to the forward path and passes through the λ / 4 plate 502, so that it is polarized in a polarization direction of about 90 degrees from the forward path, and finally the beam in the prism 83. The light is separated by the splitter and guided to the light receiving element 82a in the light receiving element part 82 by a diffraction grating formed between the light receiving element part 82 and generates at least a spherical aberration error signal. At the wavelength of 405 nm, since the wavelength is shorter than the conventional one, the spherical aberration generated when the thickness of the protective layer of the optical disk 1 is changed becomes large, and the recording / reproducing quality is greatly impaired. Therefore, the generated spherical aberration can be suppressed by driving the aberration correction mirror 14 in accordance with the above-described spherical aberration detection signal and slightly changing the reflecting surface into a spherical surface. In addition, the spherical aberration is corrected using the aberration correction mirror 14 this time, but it is also possible to move at least one of the second optical lens 29 or the first optical lens 30 described above in the optical axis direction. It is also possible to correct spherical aberration.

  Next, the wavelength 660 nm will be described. The laser beam 106 having a wavelength of 660 nm emitted from the laser diode 103 of the laser unit 101 passes through the beam combiner 109 and is substantially parallel between the coupling lens 28 and the first optical lens 30 via the prism 105 that separates the beam. It is supposed to become. A beam splitter 27 is disposed between the coupling lens 28 and the first optical lens 30 so as to be substantially coaxial with the laser beam 84 having a wavelength of 405 nm. The substantially parallel laser beam 106 emitted from the first optical lens 30 is reflected by the first surface 311 of the rising prism 31. The reflected laser beam 106 passes through an aperture filter constituting the aperture hologram 34, a polarization hologram, and a λ / 4 plate in this order to become circularly polarized light, and is condensed by the objective lens 32 to form a light spot on the optical disc 1. At this time, the polarization hologram does not act on the P-wave light of the forward path light, but acts on the S-wave light of the backward path. The laser beam 106 returning from the optical disk 1 passes in the opposite direction to the outward path, and passes through the λ / 4 plate in the aperture hologram 34, so that it is polarized in a polarization direction of about 90 degrees from the outward path. The laser beam 106 diffracted into light as needed by the polarization hologram inside is finally separated by the polarization beam splitter 105 c in the prism 105 and guided to a photodetector in the light receiving element 102.

  Next, the wavelength 780 nm will be described. The laser beam 106 having a wavelength of 780 nm emitted from the laser diode 104 of the laser unit 101 is diffracted by a beam combiner 109 and passes through a diffraction grating that forms three beams dedicated to 780 nm, and is coupled via a prism 105 that separates the beams. The lens 28 and the convex lens 30 that is the first optical lens are substantially parallel to each other. A beam splitter 27 is disposed between the coupling lens 28 and the convex lens 30 as the first optical lens so as to be substantially coaxial with the laser beam 84 having a wavelength of 405 nm. The substantially parallel laser beam 106 from the convex lens 30 which is the first optical lens is reflected by the first surface 311 of the rising prism 31. The reflected laser beam 106 passes through an aperture filter constituting the aperture hologram 34, a polarization hologram, and a λ / 4 plate in this order to become circularly polarized light, and is condensed by the objective lens 32 to form a light spot on the optical disc 1. At this time, the polarization hologram in the aperture hologram 34 hardly affects the wavelength 780 nm. The laser beam 106 returning from the optical disk 1 passes in the opposite direction to the outward path, and passes through the λ / 4 plate in the aperture hologram 34, so that the outward path is polarized in a polarization direction of about 90 degrees. The light beam is separated by the polarization beam splitter 105 b in the prism 105 and guided to a photodetector in the light receiving element 102 by a diffraction grating (not shown) formed between the light receiving element 102 and the light beam.

  By adopting such an optical configuration, spherical aberration is corrected between the integrated element 8 and the beam expander function configured by the convex lens 29 that is the second optical lens and the convex lens 30 that is the first optical lens. By disposing the aberration correction mirror 14 and the collimating lens 11, it is possible to reduce the component size of the aberration correction mirror 14, shorten the gap between the collimating lens 11 and the integrated element 8, and the first optical lens. Since the convex lens 30 is a part of the collimating lens of the laser diodes 103 and 104 in the integrated element 10, the optical pickup 3 can be reduced in size and thickness.

By the way, in an optical system that performs high-density recording / reproduction, the spot diameter on the recording surface of the disk 1 is very small and the focal depth is shallow. In order to prevent deterioration of the recording / reproducing characteristics due to hopping, it is important to minimize the chromatic aberration of the optical system. In the present embodiment, the objective lens 33 is a refractive glass lens as described above, and it is necessary to use a glass material having a relatively high refractive index in order to achieve a high numerical aperture lens. In general, it also exceeds 0.3 μm / nm, and the convex lens 30 which is the first optical lens of the beam diameter expanding means generates chromatic aberration of 0.3 μ / nm or more for 405 nm light, In addition, the spherical aberration is required to be small. On the other hand, the objective lens 32 has a small chromatic aberration of 0.1 μm / nm or less because the chromatic aberration of diffraction action and the chromatic aberration of refraction action cancel each other. The convex lens 30 which is the first optical lens of the beam diameter expanding means is shared by the optical system having a wavelength of 405 nm and the optical systems having a wavelength of 660 nm and 780 nm. The convex lens 30 which is the first optical lens of the beam diameter expanding means is , Chromatic aberration of 0.3 μm / nm or more is generated for 405 nm light, chromatic aberration is 0.1 μm / nm or less for light of 660 to 785 nm, and spherical aberration is 405 nm, 660 nm, and 785 nm. It needs to be small enough. In the present embodiment, the convex lens 30 which is the first optical lens of the beam diameter expanding means has a convex lens 30a made of a glass material having a small refractive index dispersion (a large Abbe number) and a large refractive index dispersion (a small Abbe number). A concave lens 30b made of a glass material is bonded, and as a doublet lens having a positive power as a whole, the spherical aberration is small and the chromatic aberration that cancels the chromatic aberration of the objective lens 33 is generated. In the present embodiment, a refractive index nd = 1.60970, an Abbe number vd = 57 is applied to a glass material having a small refractive index dispersion (a large Abbe number) constituting the convex lens 30a constituting the convex lens 30 which is the first optical lens. .8 glass material and a glass material having a large refractive index dispersion (small Abbe number) constituting the concave lens 30b, a glass material having a refractive index nd = 1.79925 and an Abbe number vd = 24.6, and spherical aberration is A lens that is sufficiently small and generates a large chromatic aberration of 0.3 μ / nm or more is designed to cancel the chromatic aberration of the objective lens 33 so that the chromatic aberration of the entire optical system is 0.1 μm / nm or less. doing. When the convex lens 30 that is the first optical lens is designed as described above at a wavelength of 405 nm, the convex lens 30 that is the first optical lens generates a large spherical aberration around 0.1 rmsλ at wavelengths of 660 nm and 785 nm, but chromatic aberration. Indicates a small value of 0.1 μm / nm or less. Therefore, by correcting the spherical aberrations at wavelengths of 660 nm and 785 nm with the coupling lens 28, optical characteristics having both small chromatic aberration and spherical aberration are realized at wavelengths of 660 nm and 785 nm. Table 1 summarizes the relationship between the chromatic aberration and spherical aberration of the convex lens 30 and the objective lenses 32 and 33, the coupling lens 28, and the entire optical system, which are the first optical lenses in the present embodiment, for each wavelength. Is. The entire optical system achieves practically small chromatic aberration and spherical aberration at all wavelengths. Since the coupling lens 28 is very small, adding this does not hinder the downsizing of the apparatus.

  Next, the actuator holding the objective lenses 32 and 33 will be described with reference to FIGS. FIG. 9 is a front view showing an actuator of the optical pickup device in one embodiment of the present invention, and FIG. 10 is a sectional view thereof.

  9 and 10, reference numeral 35 denotes an objective lens holding cylinder that can fix the objective lenses 32 and 33, the λ / 4 plate, the aperture filter, and the aperture hologram 34 including the polarization hologram that reacts to the DVD light by means such as adhesion. It is.

Reference numerals 36 and 37 denote focus coils, respectively, which are wound in a substantially ring shape. Reference numerals 38 and 39 denote tracking coils which are each wound in a substantially ring shape in the same manner as the focus coils 36 and 37. These focus coils 36 and 37 and tracking coils 38 and 39 are also fixed to the objective lens holding cylinder 35 with an adhesive or the like. Reference numerals 40 and 41 denote suspension wires. The suspension wires 40 and 41 connect the objective lens holding cylinder 35 and the suspension holder 42. At least the objective lens holding cylinder 35 is displaced with respect to the suspension holder 42 within a predetermined range. It is possible. Both end portions of the suspension wires 40 and 41 are fixed to the objective lens holding cylinder 35 and the suspension holder 42 by insert molding, respectively. The focus coils 36 and 37 are fixed to the suspension wire 40 by soldering or the like, and the tracking coil 38 and the tracking coil 39 are also electrically connected to the suspension wire 41 by soldering or the like. The suspension wire 40 is preferably composed of six or more round wires or leaf springs so that electric power can be supplied to each of the focus coils 36 and 37 and the tracking coils 38 and 39 joined in series. Yes.

  In order to fix the suspension holder 41 with solder or the like, the flexible substrate 43 is fixed by bonding or the like. Reference numerals 44 and 45 denote focus magnets which are configured to have a smaller magnet width direction (tracking direction) than the focus coils 36 and 37. The focus magnet 44 on the outer peripheral side of the optical disc 1 with respect to the coil center position of the focus coils 36 and 37 has an outer periphery. The focus magnet 45 on the inner circumference side of the optical disc 1 is arranged to face the inner circumference. Reference numerals 46 and 47 denote tracking magnets which are arranged to face the tracking coils 38 and 39. The focus magnets 44 and 45 are divided in the focus direction, and the tracking magnets 46 and 47 are each divided in the tracking direction. One pole faces the substantially ring-shaped piece of the focus coils 36 and 37 and the tracking coils 38 and 39. The other pole side is disposed so as to face the other part of the substantially ring shape in the focus coils 36 and 37 and the tracking coils 38 and 39. At this time, the focus magnets 44 and 45 and the magnetic yoke 48 constitute a focus magnetic circuit, respectively, and the tracking magnets 46 and 47 and the magnetic yoke 48 constitute a tracking magnetic circuit, respectively. The focus coils 36, 37, A configuration in which one tracking coil 38 and 39 is provided in each tracking magnetic circuit can be realized, and each coil can be controlled independently by energizing each coil. In the present embodiment, the focus coils 36 and 37 are controlled independently. However, the focus coils 36 and 37 and the tracking coils 38 and 39 may all be controlled independently. In this case, at least eight suspension wires 40 and 41 are required as a whole, but if only one of the pairs, for example, focus coils 36 and 37 is controlled independently, at least six suspension wires 40 and 41 are sufficient. .

  By the way, the focus magnets 44 and 45 and the tracking magnets 46 and 47 are formed by separating the magnets each having a single magnetic pole without bonding the magnets to multi-pole magnets when divided. A neutral zone occurring between them can be suppressed, and deterioration of magnetic circuit characteristics accompanying the focus shift and tracking shift of each coil can be suppressed to a minimum. In order to control a high-density optical disk with a narrow tilt margin, it is essential to attach a single-pole magnet in this way in order to improve accuracy.

In order to reduce the size of the suspension wires 40 and 41 and reduce the resonance in the buckling direction of the suspension wires 40 and 41, tension is applied in an inverted C shape. The magnetic yoke 48 functions as a magnetic yoke for the focus magnets 44 and 45 and the tracking magnets 46 and 47 from the magnetic surface, and holds and fixes the suspension holder 42 from the structural surface. It has a function and is also used to fix the suspension holder 42 such as an adhesive. In the suspension wires 40 and 41, the suspension holder 42 side is filled with a damper gel for performing damping. The damper gel uses a material that becomes a gel by UV or the like. Hereinafter, the objective lens holding cylinder 3
5, an optical pickup comprising a focus coil 36, a focus coil 37, a tracking coil 38, a tracking coil 39, objective lenses 32 and 33, a λ / 4 plate, an aperture filter, and a polarization hologram 34 that reacts to DVD light. It is called an actuator moving part.

  Reference numeral 49 denotes a laser driver which operates to emit a semiconductor laser having a wavelength of 780 nm and a wavelength of 660 nm built in the laser unit 101, and further has a function of superimposing each wavelength for noise reduction. . Further, the laser driver 49 is configured to be in contact with the carriage 4 or a cover metal plate (not shown) disposed above and below the carriage so as to effectively dissipate heat. Reference numeral 50 denotes a laser driver which operates to emit a semiconductor laser having a wavelength of 405 nm built in the laser unit 81 and has a function of superimposing each wavelength for noise reduction. Further, similarly to the laser driver 49, it is configured to be in contact with the carriage 4 or a cover metal plate (not shown) disposed above and below the carriage so that heat can be effectively radiated.

  Next, the operation of the optical pickup actuator movable part in the present embodiment will be described. Electric power is supplied from a power source (not shown) to the focus coils 36 and 37 and the tracking coils 38 and 39 through the flexible substrate 43 attached to the suspension holder 42 and the suspension wires 40 and 41 connected thereto. At least six suspension wires 40 and 41 are provided in total, two of which are connected to the tracking coils 38 and 39 provided in series, and two of the remaining four are connected to the focus coil A36. The remaining two are connected to the focus coil B37. As a result, the focus coils 36 and 37 can be energized independently of each other.

  When a current is passed through the focus coil 36 and the focus coil 37 in the positive direction (or negative direction), the focus direction is determined from the positional relationship between the focus coils 36 and 37 and the focus magnets 44 and 45 and the polarity of the magnetic poles divided into two. A focus magnetic circuit that can be moved is formed, and the focus direction can be controlled in accordance with the direction and amount of current flow. Next, when a current is passed through the tracking coils 38 and 39 in the positive direction (or negative direction), the tracking coil 38 and 39 and the tracking magnets 46 and 47 are arranged in the tracking direction due to the positional relationship between the tracking coils 38 and 39 and the polarity of the magnetic poles divided into two. A tracking magnetic circuit that can be moved is formed, and the tracking direction can be controlled.

  By the way, in the embodiment, as described above, the current can flow independently through the focus coil 36 and the focus coil 37. Accordingly, when the direction of the current flowing in one coil is reversed, a force in the direction approaching the optical disc 1 acts on the focus coil 36 and a force acts on the focus coil 37 in a direction away from the optical disc 1. As a result, due to the contradicting forces, a moment that rotates in the radial direction is generated in the optical pickup actuator movable portion, and tilts to a position where the forces with the torsional moments acting on the six suspension wires 40 and 41 are balanced. The tilt direction can be controlled in accordance with the direction and amount of flow through the focus coil 36 and the focus coil 37.

  The objective lenses 32 and 33 will be described below.

As shown in FIG. 10, when the maximum thickness of the objective lens 32 is t1, and the maximum thickness of the objective lens 33 is t2, it is preferable that t2 / t1 = 1.05 to 3.60. That is, if t2 / t1 is smaller than 1.05, the diameter of the objective lens 33 must be increased, the optical pickup 3 becomes larger, and the size cannot be reduced, and t2 / t1 is 3.60. If it is larger, the thickness of the objective lens 33 becomes too thick and is not suitable for thinning.

  In this way, by configuring the objective lens 33 corresponding to the short wavelength light to be thicker than the long wavelength objective lens 32, it is possible to reduce the size of the apparatus and to define the ratio of the thicknesses. In particular, it is possible to reduce the thickness and size of the apparatus.

  Next, the amount of protrusion of the objective lens 33 that protrudes closer to the optical disc 1 than the objective lens 32 will be described. When the thickness of the optical disk device is 13 mm or less, the distance between the objective lenses 32 and 33 and the mounted optical disk 1 becomes very narrow. Therefore, when the objective lens 32 is considered as a reference, it has been found that the protrusion amount t3 shown in FIG. 10 is preferably 0.05 mm to 0.62 mm. The amount of protrusion is represented by the difference between the maximum protruding portion of the objective lens 32 on the side where the optical disc 1 is mounted and the maximum protruding portion of the objective lens 33 on the side where the optical disc 1 is mounted. If t3 is smaller than 0.05 mm, the lens diameter of one of the objective lenses 32 and 33 must be increased, which is unsuitable for downsizing, and if t3 protrudes larger than 0.62 mm, the optical disk 1 The probability of contact with is increased.

  In this way, by projecting the objective lens 33 corresponding to light having a short wavelength as described above, it is possible to reduce the size or improve the reliability.

  Further, as shown in FIG. 1, the center of the objective lens 32 corresponding to the long wavelength is substantially coincided with the center line M passing through the center of the spindle motor 2 along the moving direction L of the carriage 4. It is preferable. That is, with such a configuration, it is possible to employ a 3-beam DPP (differential push-pull) system that has the most proven record in the conventional light detection system.

  The diameter of the spot of light incident on the objective lenses 32 and 33 will be described.

  As shown in FIG. 2, when the diameter of the light spot incident on the objective lens 32 is t4 and the diameter of the light spot incident on the objective lens 33 is t5, miniaturization is realized by satisfying the relationship of t5 <t4. It's easy to do. In consideration of lens design and the like, it is preferable that t5 / t4 = 0.4 to 1.0. If t5 / t4 is smaller than 0.4, the objective lens 33 is difficult to manufacture, and the objective lens 32 becomes large and unsuitable for downsizing. If t5 / t4 is larger than 1.0, the thickness of the objective lens 33 becomes too thick. Therefore, it is not suitable for downsizing.

  Next, another embodiment will be described.

  FIG. 13 is a schematic diagram showing an optical system of the optical pickup device according to the embodiment of the present invention. In FIG. 13, reference numeral 600 denotes a light source unit equipped with a light source or a light receiving element that emits a laser having a wavelength of 450 nm or less. The light source unit 600 emits a so-called blue laser, blue-violet laser, or the like, and in this embodiment, a light source unit 600 emits a laser having a wavelength of 408 nm. Further, the light source unit 600 may be provided with a monitor means for monitoring the output of the laser such as a front light monitor, or the light receiving element and the light source may be constituted by separate members.

  Reference numeral 601 denotes a collimating lens that converts laser light emitted from the light source unit 600 into substantially parallel light, 602 denotes an optical lens that converts light from the collimating lens 601 to diffused light, and 603 denotes a light source that emits light of 650 nm to 790 nm. The light source mounted with the light receiving element, sometimes the front light monitor, and the light source mounted on the light source unit 603 emits at least one light beam of a red laser corresponding to DVD and an infrared laser corresponding to CD.

In this embodiment, as the light source unit 603, the light source, the light receiving element, the front light monitor, and the like are integrally attached by a coupling member or the like, but the members may be configured by separate members. In the present embodiment, the light source unit 603 is provided with a light source that emits two laser light beams of a red laser corresponding to a DVD and an infrared laser corresponding to a CD. A two-wavelength frame laser is preferably used.

  Reference numeral 604 denotes a coupling lens that reduces the diffusion angle of light from the light source unit 603 and reduces the spherical aberration of light emitted from the light source unit 603. Reference numeral 605 denotes a wavelength-dependent beam splitter. Has an inclined portion inclined inside, and is configured by providing an optical thin film or the like on the inclined portion. The light from the light source unit 600 passes through the inclined portion in the beam splitter 605, and the light from the light source unit 603 is reflected by the inclined portion in the beam splitter 605. As described above, the beam splitter 605 guides the light from the light source units 600 and 603 to substantially the same optical path.

  Reference numeral 606 denotes an optical lens, and the optical lens 602 and the optical lens 606 have a beam expander function. That is, light from the light source unit 600 is converted into diffused light by the optical lens 602 and converted into substantially parallel light by the optical lens 606, and the light flux is extended. Furthermore, the diffusion angle of the light emitted from the light source unit 603 is converted by the coupling lens 604, and similarly converted to substantially parallel light by the optical lens 606.

  Reference numeral 607 denotes a rising portion, and the rising portion 607 is provided with a wavelength-selective optical thin film. Light emitted from the light source unit 603 is sent to the objective lens 608 by the rising portion 607, and the objective lens The light is condensed by 608 and focused on the optical disc 1. Further, the light from the light source unit 600 passes through the riser 607. Reference numeral 609 denotes a rising portion. The rising portion 609 reflects light transmitted through the rising portion 607 and is sent to the objective lens 610 to be condensed.

  Hereinafter, the characteristic part will be described.

  The optical lens 606 is configured by bonding two lenses, and is configured by bonding a convex lens 606a and a concave lens 606b with an adhesive or the like. At this time, if the refractive powers of the light of the convex lens 606a and the concave lens 606b are P1 and P2, respectively, P1> 0, P2 <0, and P1 + P2> 0. When the convex lens 606a and the concave lens 606b are combined, the whole becomes a convex lens. Further, when looking at refractive index dispersion (1 / (lens Appe number): Appe number depends on lens constituent materials), the convex lens 606a is configured to be smaller than the concave lens.

  Accordingly, the optical lens 606 having an achromatic performance with respect to the wavelength λ as shown in FIG. 14 can be obtained by making the refractive power of the light of the convex lens 606a and the concave lens 606b different, or by appropriately selecting a constituent material. Can be obtained. According to the characteristics shown in FIG. 14, it is possible to obtain an optical lens 606 that has high achromatic performance for short-wavelength light and low achromatic performance for long-wavelength light. That is, the achromatic performance of the blue laser emitted from the light source unit 600 is high, and the achromatic performance of the optical lens 606 is weak to the infrared or red laser from the light source unit 603.

The objective lens 610 that condenses short-wavelength light emitted from the light source unit 600 needs to use a glass material having a relatively high refractive index in order to achieve a high numerical aperture lens. Therefore, the chromatic aberration of the objective lens 610 generally exceeds 0.3 μm / nm. In order to reduce the chromatic aberration by the optical lens 606, the light emitted from the light source unit 600 is 0.3 μm. An optical lens 606 having an achromatic performance of / nm or more is preferably used. Further, in the objective lens 608, the chromatic aberration of diffraction action and the chromatic aberration of refraction action cancel each other out, so that the chromatic aberration is a small value of 0.1 μm / nm or less. That is, chromatic aberration does not occur so much in the objective lens 608. Therefore, in the optical lens 606, when the achromatic performance is too large with respect to the light having a relatively long wavelength from the light source unit 603, the chromatic aberration is increased in the optical lens 606 although the chromatic aberration is small in the folding objective lens 608. As a result, recording characteristics and reproduction characteristics deteriorate.

  Therefore, in the present embodiment, the achromatic performance of the optical lens 606 is reduced for light of a short wavelength so that the achromatic performance of the optical lens 606 is increased for light of a short wavelength (see FIG. 14). In addition, various characteristics and constituent materials of the convex lens 606a and the concave lens 606b were appropriately selected.

  Next, the optical path will be described.

  The light emitted from the light source unit 600 is converted into substantially parallel light by the collimator lens 601, converted to diffused light by the optical lens 602, and the diffused light passes through the beam splitter 605 and enters the optical lens 606. The light transmitted through the optical lens 606 becomes substantially parallel light, and the parallel light passes through the riser 607, is reflected by the riser 609, is guided to the objective lens, and is collected. The light reflected by the optical disk 1 is converted into substantially parallel light by the objective lens 610, reflected by the start-up unit 609, and passed through the optical lens 606, the beam splitter 605, the optical lens 602, the collimator lens 601 and the like. Sent to the element.

  Similarly, the light emitted from the light source unit 603 passes through the coupling lens 604, is reflected by the beam splitter 605, passes through the optical lens 606, is reflected by the riser 607, and is collected by the objective lens 608. The light reflected by the optical disk 1 is converted into substantially parallel light by the objective lens 608, passes through the riser 607 and the optical lens 606, is converted to convergent light, and is then reflected by the beam splitter 605 for coupling. After entering the lens 604, it enters the light receiving element or the like.

  Still another embodiment will be described with reference to FIG.

  The difference between the embodiment of FIG. 15 and the embodiment of FIG. 13 is that the optical lens 606 is simply a convex lens 611 that converts light from each light source unit into substantially parallel light, and between the optical lens 602 and the beam splitter 605. The hologram element 613 is provided, or the hologram element 612 is provided between the rising portions 607 and 609. As a matter of course, the optical lens 602 and the convex lens 611 have a function of a beam expander.

  The hologram elements 612 and 613 are provided with convex portions or concave portions at a predetermined interval, and the short wavelength chromatic aberration emitted from the light source unit 600 is corrected by adjusting the interval. Further, the hologram elements 612 and 613 are disposed in an optical path through which only a light beam having a short wavelength passes. That is, if the hologram elements 612 and 613 are arranged in the optical path of the light emitted from the light source unit 603, the aberration of the infrared or red laser is increased, which may affect the recording / reproducing characteristics.

  In this embodiment, the hologram elements 613 and 612 are arranged at two locations. However, either one may be used, and at least one member that corrects chromatic aberration is arranged in the short wavelength optical path. Thus, the same effect can be obtained.

In the present invention, by providing a condensing unit dedicated to blue light and a condensing unit for red and infrared, each light can be reliably condensed on the optical disk, and the structure of the condensing unit It can be applied to an optical pickup device, an optical disk device, and the like that can realize a reduction in thickness, size, and suppression of deterioration of characteristics even in response to lasers of various wavelengths including a blue laser.

The top view which shows the optical pick-up apparatus in one embodiment of this invention The side view which shows the optical pick-up apparatus in one embodiment of this invention The elements on larger scale which show the optical pick-up apparatus in one embodiment of this invention The elements on larger scale which show the optical pick-up apparatus in one embodiment of this invention The figure which shows the aberration correction mirror used for the optical pick-up apparatus in one embodiment of this invention The figure which shows the aberration correction mirror used for the optical pick-up apparatus in one embodiment of this invention The figure which shows the aberration correction mirror used for the optical pick-up apparatus in one embodiment of this invention The figure which shows the aberration correction mirror used for the optical pick-up apparatus in one embodiment of this invention The front view which shows the actuator of the optical pick-up apparatus in one embodiment of this invention Sectional drawing which shows the actuator of the optical pick-up apparatus in one embodiment of this invention The front view which shows the actuator of the optical pick-up apparatus in one embodiment of this invention Sectional drawing which shows the actuator of the optical pick-up apparatus in one embodiment of this invention The figure which shows the optical system of the optical pick-up apparatus in one embodiment of this invention The graph which shows the relationship between the wavelength of the optical lens of the optical pick-up apparatus in one embodiment of this invention, and achromatic performance The figure which shows the optical system of the optical pick-up apparatus in one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Spindle motor 3 Optical pick-up 4 Carriage 5 Optical pick-up actuator 8, 10 Integrated element 11 Collimating lens 12 Beam shaping prism 13 Critical angle prism 14 Aberration correction mirror 27 Beam splitter 28 Coupling lens 29 Convex lens 30 Convex lens 31 Standing prism 32 , 33 Objective lens

Claims (15)

A first optical unit that emits light of a first wavelength; a second optical unit that emits at least one light of a second wavelength longer than the first wavelength; and Optical means for guiding light and light having a second wavelength longer than the first wavelength to substantially the same optical path, and first light collecting means for condensing light having the first wavelength from the optical means on the optical disc And second condensing means for condensing light having a wavelength longer than the first wavelength onto the optical disc, and at least for the light having the first wavelength in the optical path of the light having the first wavelength. An optical pickup apparatus comprising chromatic aberration correcting means for generating chromatic aberration for correcting chromatic aberration of the first light collecting means. 2. The optical pickup device according to claim 1, wherein the chromatic aberration correcting means is provided in an optical path through which light of both the first wavelength and the second wavelength passes. The chromatic aberration correction means has high chromatic aberration performance for the first wavelength light, and the chromatic aberration correction performance for the second wavelength light is lower than the chromatic aberration performance for the first wavelength. The optical pickup device according to claim 2. As the chromatic aberration correcting means, a convex lens having a positive power and a concave lens having a negative power are joined to each other to form an upwardly convex lens and an optical lens having a total positive power is used. The optical pickup device according to claim 2. 2. The optical pickup device according to claim 1, wherein the chromatic aberration correcting means is provided between the optical means and the first and second light collecting means. 2. The optical pickup device according to claim 1, wherein the chromatic aberration correcting means is disposed in an optical path constituted only by light having the first wavelength. 7. The optical pickup device according to claim 6, wherein a chromatic aberration correcting means is provided in at least one of the first light path of the first light source unit and the optical means or between the first and second light collecting means. 7. The optical pickup device according to claim 6, wherein a hologram element is used as the chromatic aberration correcting means. A first optical unit that emits light having a first wavelength; a second optical unit that emits at least one light having a wavelength longer than the first wavelength; the light having the first wavelength; Optical means for guiding light having a wavelength longer than the first wavelength to substantially the same optical path, first condensing means for condensing light having the first wavelength from the optical means on the optical disc, and the first wavelength A second condensing means for condensing light having a longer wavelength on the optical disc, and a beam diameter enlarging means for enlarging a beam diameter of the light having the first wavelength, wherein the beam diameter enlarging means is the optical means. And a first optical lens disposed between the first condensing means and a second optical lens disposed between the optical means and the first optical unit. The optical lens includes an optical system of the first wavelength light and the first wavelength. It is shared by a long wavelength optical system, and for the light of the first wavelength, a chromatic aberration that corrects the chromatic aberration of the first condensing means is generated, and the wavelength is longer than the first wavelength. An optical pickup device that generates chromatic aberration for correcting the chromatic aberration of the second condensing means. The first condensing means is a refractive lens, and the second condensing means is a diffractive / refractive composite lens in which a diffraction grating is provided on the surface of the refractive lens, and the first optical lens. However, chromatic aberration that corrects chromatic aberration of the first condensing means is generated for the light of the first wavelength, and chromatic aberration is generated for light of a wavelength longer than the first wavelength. The optical pickup device according to claim 9, wherein the generation amount is 0.1 μm / nm or less. The first condensing means is a refraction type lens formed of a glass material, and the second condensing means is a diffraction / refraction made of a resin material provided with a diffraction grating on the surface of the refraction type lens. It is a compound lens, and the first optical lens has a chromatic aberration of 0.3 μm / nm or more in the direction of correcting the chromatic aberration of the first condensing means for the light of the first wavelength. 11. The optical pickup device according to claim 10, wherein the amount of chromatic aberration generated is 0.1 [mu] m / nm or less for light generated and having a wavelength longer than the first wavelength. The first optical lens is formed by bonding a convex lens made of a glass material having a small refractive index dispersion (large Abbe number) and a concave lens made of a glass material having a large refractive index dispersion (small Abbe number), and has a positive power as a whole. A doublet lens that is designed to generate a predetermined chromatic aberration and minimize spherical aberration with respect to light of the first wavelength, while having a wavelength longer than the first wavelength. 12. The optical pickup device according to claim 10, wherein the optical pickup device is designed to minimize the amount of chromatic aberration generated with respect to light. The first optical lens is formed by bonding a convex lens made of a glass material having a small refractive index dispersion (large Abbe number) and a concave lens made of a glass material having a large refractive index dispersion (small Abbe number), and has a positive power as a whole. A doublet lens that is designed to generate a predetermined chromatic aberration and minimize spherical aberration with respect to light of the first wavelength, while having a wavelength longer than the first wavelength. A coupling lens that is designed to minimize the amount of chromatic aberration generated for light and that corrects the spherical aberration of the first optical lens in an optical system having a wavelength longer than the first wavelength. The optical pickup device according to claim 12, wherein the optical pickup device is provided. The laser diode mounted on the first optical unit emits substantially blue to substantially blue-violet light, and the laser diode mounted on the second optical unit emits substantially infrared to substantially red light. The optical pickup device according to claim 1, wherein 15. An optical disc apparatus comprising: a driving unit that rotates an optical disc; and a carriage that is mounted with the optical pickup device according to claim 1 and is movably attached to the driving unit.

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