JP4640525B2 - Optical pickup device - Google Patents

Description

  The present invention relates to an optical pickup device used for recording / reproduction on a high-density recording disk such as a DVD or an optical disk such as a compact disk.

  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 are used to perform higher-density recording than when each of the above lasers is used. It has become like this.

JP 11-224436 A JP 2000-123394 A JP-A-10-334494

  However, in a video recorder that records and reproduces an optical disc that supports a blue laser, the device itself is very large, so even if a blue laser is used in the optical system, optical design is easy using a means such as a beam expander. In addition, even when recording / reproduction can be performed on both an optical disc compatible with a blue laser and an optical disc compatible with a red laser, the device is very large, so that separate optical systems according to wavelengths can be configured in the device. There is no particular problem.

  However, at least one of recording and reproduction can be performed on the two 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, red It is impossible to provide an optical system corresponding to each light of the outer laser and the red laser, and the blue laser has a larger spherical aberration than other lasers, and it is very difficult to process with a common optical system. In addition, the optical characteristics are deteriorated by integrating the optical system.

  The present invention solves the above-described conventional problems, and provides an optical pickup device that can realize at least one of thinning, miniaturization, and suppression of deterioration of characteristics even in response to lasers of various wavelengths including a blue laser. The purpose is that.

The present invention relates to a first optical unit that emits light for a disc corresponding to a blue laser, a second optical unit that emits light for DVD and CD, and a disc corresponding to the blue laser. Optical means for guiding the light for DVD, the light for DVD and the light for CD to substantially the same optical path, and a disc objective corresponding to the blue laser for condensing the light for disc corresponding to the blue laser A first condensing unit having a lens, a second condensing unit having a CD / DVD objective lens for condensing the DVD light and the CD light, the optical means, A first riser provided between the first condensing unit and reflecting the light for the disc corresponding to the blue laser to the first condensing unit; the optical unit; Between the second light collector Second rising means for reflecting the light for DVD and the light for CD and guiding the light to the second light converging unit, and spherical aberration of the light for the disc corresponding to the blue laser. Correction means for correcting, wherein the first raising means and the second raising means are arranged in series along an optical path, and the light for the disc corresponding to the blue laser is at least the optical Means, the correction means, and the first start-up means to be guided to the first light condensing unit, and the DVD light and the CD light are at least the optical means and the correction means. The optical pickup device is guided to the second light collecting unit via the second start-up unit.

  With the above configuration, the present invention is configured to have a condensing unit dedicated to blue light and a condensing unit for red and infrared, so that each light can be reliably condensed on the optical disc. The structure of the optical part can be simplified.

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

  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, whereby 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 an integrated element including a blue-violet laser part 81 and a light receiving element part 82, and details will be described with reference to FIG. The laser unit 81 includes a laser diode 81a that generates 405 nm laser light, and the laser diode 81a is disposed in a sealed space formed by a base 81c and a cover 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.

  In addition, a plurality of terminals 81d are erected on the base 81c, and the terminal 81d is composed of a ground terminal, a terminal for supplying current to the laser diode 81a, and the like.

  The cover 81b is provided with an opening (not shown) through which light enters and exits, and a transparent plate (not shown) such as glass is provided on the cover 81b by a method such as adhesion so as to close the opening. Yes. Reference numeral 83 denotes a prism directly attached to the cover 81b by bonding or the like on the opening of the cover 81b. The prism 83 transmits the laser beam 84 emitted from the laser diode 81a to irradiate the optical disc 1, and from the optical disc 1. This is a prism that guides the return light of the light to the light receiving element portion 82. The prism 83 is provided with a diffraction grating (not shown) for monitoring the laser beam 84, and further divides the laser beam 84 having a wavelength of 405 nm at a position led to the light receiving element portion 82 side (see FIG. (Not shown) for focus detection, tracking detection, spherical aberration detection, detection of signals recorded on the optical disc 1, and control signals. In the present embodiment, a transparent cover member 83a is provided between the prism 83 and the cover 81b. The cover member 83a is directly joined to the cover 81b using a technique such as adhesion. The prism 83 is provided with inclined surfaces 83c to 83e 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 83c to 83e. The inclined surfaces 83c to 83e correspond to joint surfaces such as transparent glass blocks and resin blocks. In this embodiment, three inclined surfaces are provided, but one or more inclined surfaces may be provided. In the present embodiment, in the laser unit 81, the opening provided in the cover 81b is closed with a transparent plate (not shown), and the space constituted by the cover 81b and the base 81c is filled with an inert gas. Although the configuration is adopted, the opening may be closed with the cover member 83a without closing the opening with a transparent plate (not shown). In addition, a diffraction grating (not shown) for forming three beams is formed on the cover member 83a as necessary on the laser unit 81 side of the prism 83. In addition to the diffraction grating, another optical component can be integrally or attached to the cover member 83a. 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). And the like that guides part of the 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. Used. Further, when the prism 83 is attached to the cover member 83a by a technique such as bonding, the adhesive protruding outward from the inclined surfaces 83c to 83e, which are bonding surfaces, or the concave portions generated in the inclined surfaces 83c to 83e can be relaxed. That is, if the light emitted from the laser diode 81a hits the concave or convex portions formed on the outer surface portions of the inclined surfaces 83c to 83c 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. Further, the cover member 83a may not be used to close the opening, and the cover member 83a may be omitted and the prism 83 may be used to directly close the opening.

  In the present embodiment, the inside of the laser unit 81 is hermetically sealed. However, the cover 81b may be provided with a hole different from the light emission port so that the inside of the laser unit 81 is not sealed. With this configuration, it is possible to prevent the optical member or the like provided at the emission port of the laser unit 81 from being fogged.

  In the light receiving element portion 82, the light receiving element 82a is covered with a case 82b including a transparent member, and a terminal 82c electrically connected to the light receiving element 82a is led out of the case 82b from the case 82b. ing.

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

  Reference numeral 10 denotes an integrated element including a red and infrared laser unit 101 and a light receiving element unit 102, and details will be described with reference to FIG. The laser unit 101 includes a laser diode 103 that emits laser light having a wavelength of approximately 660 nm and a laser diode 104 that emits laser light having a wavelength of approximately 780 nm. The laser diodes 103 and 104 include a base 101a and a cover 101b. It is arrange | positioned in the sealed space comprised by these.

  In this embodiment, the laser diodes 103 and 104 are arranged as separate light emitter blocks in the sealed space. However, a plurality of light emitting layers are provided in one light emitter block, and one light emitter block is provided. The structure which arrange | positions in a sealed 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 sealed space may be employed.

  The base 101a is provided with a plurality of terminals 101c. The terminal 101c 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. In addition, an opening (not shown) through which light enters and exits is provided in the cover 101b, and a transparent plate (not shown) such as glass is provided in the cover 101b by a technique such as adhesion so as to close the opening. Yes. 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 diffraction grating (not shown) for monitoring the laser beam 106 and further divides the laser beam 106 having a wavelength of 780 nm or 660 nm at a position led to the light receiving element 102 side. (Not shown) is provided so that focus detection, tracking detection, signals recorded on the optical disc 1, control signals, and the like 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. 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.

  Reference numeral 107 denotes a polarization hologram diffraction grating for a wavelength of 660 nm or 780 nm, which is provided apart from the prism 105, and can detect focus detection, tracking detection, signals described on the optical disc 1, and the like. Further, when the polarization hologram 107 operates at a wavelength of 660 nm, the influence is less on the laser beam having a wavelength of 780 nm. In the case of operating at a wavelength of 780 nm, the influence on the laser beam having a wavelength of 660 nm is reduced. 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. 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. The diffraction grating 109 is directly bonded to the cover 101b by a technique such as adhesion so as to close the opening of the cover 101b. In the present embodiment, the opening serving as the light emission port of the cover 101b is closed with a transparent plate, but the transparent plate is configured by closing the opening with the diffraction grating 109 itself without using this transparent plate. Becomes unnecessary, and the configuration becomes simple.

  In this embodiment, the inside of the laser unit 101 is hermetically sealed. However, a hole portion different from the light exit port may be provided in the cover 101b so that the inside of the laser unit 101 is not sealed. With this configuration, it is possible to prevent the optical member or the like provided at the emission port of the laser unit 101 from being fogged.

  The light emitted from one of the laser diodes 103 and 104 passes through the opening of the case 101 b, passes through the diffraction grating 109, the prism 105, and the polarization hologram diffraction grating 107, is guided to the optical disk 1, and is reflected by the optical disk 1. The light passes through the polarization hologram diffraction grating 107 and the prism 105 and is guided to the light receiving element unit 102. At this time, the reflected light from the optical disk 1 at the prism 105 is reflected between the inclined surfaces 105 a and 105 b and is incident on the light receiving element portion 102 located on the side of the line connecting the laser portion 101 and the polarization hologram diffraction grating 107. Incident.

  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 for separating 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 square shape, a quadrilateral 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 figure, C, C ′ and D, D ′ correspond to the positions of the outer peripheral portion of the insulating portion 26 and the cavity portion 21, respectively. The positions of D and D 'are the outer peripheral part of the cavity part 21, and since this outer peripheral part is restrained, the displacement is zero. The displacement is convex downward at the annular portion corresponding to CD, C′-D ′, and convex upward at the portion corresponding to the diameter of C-C ′ from the boundary of C, C ′. Although correction of spherical aberration generally requires an aspherical shape, the curved surface shape in C-C ′ is exactly an aspherical shape. Therefore, in the present invention, the curved surface portion in C-C ′, 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 the present 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 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.

  A beam splitter 27 is used to separate and combine the laser beam 84 and the laser beam 106 emitted from the integrated device 8 and the integrated device 10. Reference numeral 28 denotes a collimating lens for wavelengths 660 nm and 780 nm, which is used to make the diverging 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 29 denotes a concave lens having a negative power, and reference numeral 30 denotes a convex lens having a positive power. The combination of the concave lens 29 and the convex lens 30 expands the laser beams 84 and 106 to a desired beam diameter. Reference numeral 31 denotes an upright prism. A dielectric multilayer film having a function of reflecting the first surface 311 with respect to the laser light 106 having wavelengths of 660 nm and 780 nm and a function of transmitting with respect to the wavelength of 405 nm is formed. Yes. Further, the second surface 312 can reflect 405 nm. 32 is an objective lens for an optical disc (DVD) 1 corresponding to a wavelength of 660 nm, and has a function capable of focusing on a desired recording position with parallel light even on an optical disc (CD) 1 corresponding to a wavelength of 780 nm. It is an objective lens. Reference numeral 33 denotes an objective lens for an optical disc (Blu-Ray or AOD) 1 corresponding to a wavelength of 405 nm. In the embodiment, the objective lens 32 is arranged at the spindle motor center position, and the objective lens 33 is arranged on the opposite side of the objective lens 32 from the convex lens 30, that is, in the tangential direction with respect to the optical disc 1. 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, thereby facilitating 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). With such a configuration, although the size of the objective lens holding cylinder is somewhat increased, the gap between the tracking coil 39 and the tracking magnet 47 can be widened. As a result, the size of at least one of the tracking coil 39 and the tracking magnet 47 is increased. Since the driving force for driving the objective lenses 32 and 33 can be sufficiently obtained, high-speed access and the like can be realized.

  Reference numeral 34 denotes an aperture filter for realizing a numerical aperture necessary to cope with CD and DVD optical disks, and is realized by means such as a dielectric multilayer film and a hologram aperture. The aperture filter 34 is integrally formed with a λ / 4 plate corresponding to wavelengths 660 nm and 780 nm, and the polarization direction is polarized by approximately 90 degrees in the forward path and the return path. Reference numeral 35 denotes a λ / 4 plate for a wavelength of 405 nm, and the polarization direction is polarized by approximately 90 degrees in the forward path and the return path. The λ / 4 plates 34 and 35 can be arranged in a common optical path having wavelengths of 405 nm, 660 nm, and 780 nm.

  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.

  In FIG. 9, reference numeral 36 denotes an objective lens holding cylinder that can fix the objective lenses 32 and 33, the λ / 4 plate-attached aperture filter 34, and the λ / 4 plate 35 by means such as adhesion.

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 36 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 36 and the suspension holder 42. At least the objective lens holding cylinder 36 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 36 and the suspension holder 42 by insert molding, respectively. The suspension wire 40 includes focus coils 36 and 37.
Also, the tracking coil 38 and the tracking coil 39 are 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. In the following description, the objective lens holding tube 36, the focus coil 36, the focus coil 37, the tracking coil 38, the tracking coil 39, the objective lenses 32 and 33, the aperture filter 34 with a λ / 4 plate and the λ / 4 plate 35 are included. Is called an optical pickup actuator movable 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 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 beam shaping prism 12 and the critical angle prism 13. 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 by means such as a dielectric multilayer film on both surfaces of the beam shaping prism 12 and the critical angle prism 13 facing the gap. Next, the laser beam 84 emitted from the critical angle prism 13 passes through the beam splitter 27, enters the rising prism 31 through the concave lens 29 and the convex lens 30, passes through the first surface 311, and passes through the second surface. Reflected at 312. The reflected laser beam 84 passes through the λ / 4 plate and becomes circularly polarized light, and 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, so that it is polarized in a polarization direction of about 90 degrees from the forward path, and finally the beam splitter in the prism 83. And is guided to the light receiving element 82a in the light receiving element portion 82 by a diffraction grating formed between the light receiving element portion 82 and 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 correct the spherical aberration by moving at least one of the concave lens 29 or the convex lens 30 in the optical axis direction. is there.

Next, the wavelength 660 nm will be described. A laser beam 106 having a wavelength of 660 nm emitted from the laser diode 103 of the laser unit 101 passes through a beam combiner 109 and a diffraction grating forming three beams dedicated to 660 nm, and passes through a prism 105 and a polarization hologram diffraction grating 107 that separate the beams. Thus, the light beam is substantially parallel by the collimator lens 28, reflected by the beam splitter 27, changes its direction, enters the rising prism 31 through the concave lens 29 and the convex lens 30, and is reflected by the first surface 311. The reflected laser beam 106 passes through the λ / 4 plate and becomes 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 diffraction grating 107 does not act on the P wave of the forward light, but acts on the S wave 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, so that it is polarized in a polarization direction of about 90 degrees from the outward path, and is changed by the polarization hologram diffraction grating 107 as necessary. Laser light diffracted into light 1
06 is finally separated by a beam splitter in the prism 105 and guided to a photodetector in the light receiving element 102.

  Next, the wavelength 780 nm will be described. A laser beam 106 having a wavelength of 780 nm emitted from the laser diode 104 of the laser unit 101 passes through a diffraction grating that is diffracted by a beam combiner 109 and forms three beams dedicated to 780 nm, and a prism 105 and a polarization hologram diffraction grating 107 that separate the beams. Through the collimating lens 28, the light is reflected by the beam splitter 27, changes its direction, enters the rising prism 31 through the concave lens 29 and the convex lens 30, and is reflected by the first surface 311. The reflected laser beam 106 passes through the λ / 4 plate-attached aperture filter 34, becomes circularly polarized light and has a desired numerical aperture, and is condensed by the objective lens 32 to form a light spot on the optical disk 1. At this time, the polarization hologram diffraction grating 107 hardly affects the wavelength 780 nm. The laser beam 106 returning from the optical disk 1 passes in the opposite direction to the forward path and passes through the λ / 4 plate, so that it is polarized in a polarization direction of about 90 degrees from the forward path, and finally the beam splitter in the prism 105. And is guided to a photodetector in the light receiving element 102 by a diffraction grating formed between the light receiving element 102 and the light receiving element 102.

  By adopting such an optical configuration, the aberration correcting mirror 14 and the collimating lens 11 for correcting the spherical aberration are disposed between the integrated element 8 and the beam expander function configured by the concave lens 29 and the convex lens 30. Since the size of the aberration correction mirror 14 can be reduced, and the gap between the collimating lenses 11 and 28 and the integrated elements 8 and 10 can be shortened, the optical pickup 3 can be reduced in size and thickness. .

  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, the size is reduced 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.

  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 Therefore, the present invention can be applied to an optical pickup device, an optical disk device, and the like that can realize at least one of thinning, downsizing, and suppression of deterioration of characteristics even when dealing with lasers of various wavelengths including a blue laser.

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, 28 Collimating lens 12 Beam shaping prism 13 Critical angle prism 14 Aberration correction mirror 27 Beam splitter 29 Concave lens 30 Convex lens 31 Standing prism 32, 33 Objective lens

Claims (4)

A first optical unit that emits light for a disc corresponding to a blue laser;
A second optical unit that emits light for DVD and light for CD;
Optical means for guiding the light for the disc corresponding to the blue laser, the light for the DVD, and the light for the CD to substantially the same optical path;
A first condensing unit having a disc objective lens corresponding to a blue laser for condensing the disc light corresponding to the blue laser;
A second condensing unit having a CD / DVD objective lens for condensing the DVD light and the CD light;
A first start-up means provided between the optical means and the first condensing unit, which reflects the light for the disc corresponding to the blue laser and guides it to the first condensing unit;
A second start-up unit provided between the optical unit and the second light collecting unit, and reflects the light for DVD and the light for CD to guide the light to the second light collecting unit; ,
Correction means for correcting the spherical aberration of the light for the disc corresponding to the blue laser,
The first raising means and the second raising means are arranged in series along an optical path, and the light for the disc corresponding to the blue laser is at least the optical means, the correction means, and the first The light for the DVD and the light for the CD are guided to at least the optical means, the correction means, and the second startup means through the startup means. An optical pickup device that is guided to the second condensing unit via the optical pickup device. 2. The optical pickup device according to claim 1, wherein the correction means is a lens, and corrects spherical aberration by moving the lens in the optical axis direction. The second start-up means transmits the light for the disc corresponding to the blue laser, and the light for the disc corresponding to the blue laser passes through the optical means and the correction means, and then the second light Is led to the first condensing part via the first riser,
The DVD light and the CD light are guided to the second condensing unit via the optical unit and the correction unit and the second start-up unit. The optical pickup device according to claim 1. 2. The optical pickup device according to claim 1, wherein the light for the disc corresponding to the blue laser is substantially blue to substantially blue-violet light.