JP2008226452A - Optical pickup device and its light source unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device for recording and reproducing a plurality of optical information recording media, which simplifies the assembly thereof and improves work efficiency and is resistant to a temperature change and change with time, and to provide its light source unit. <P>SOLUTION: The optical pickup device 10 is characterized in that a first light source 11 used for recording/reproducing a first optical information recording media, a second light source 12 used for recording/reproducing a second optical information recording media and an optical detecting means 50 for receiving and detecting a luminous flux reflected from an information recording surface are integrated into a unit 60. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system, and information is recorded on the information recording surface or information on the information recording surface is reproduced. In particular, the present invention relates to an optical pickup apparatus and a light source unit for recording / reproducing a plurality of optical information recording media having transparent substrates having different thicknesses.

  In recent years, along with the practical use of short-wavelength red semiconductor lasers, high-density DVDs with the same size and large capacity as conventional CDs (compact discs) are used as optical information recording media (hereinafter also referred to as optical discs). Digital video disc) has been commercialized. In this DVD, the numerical aperture on the optical disk side of the objective lens when using a short wavelength semiconductor laser of 635 nm or 650 nm is required to be about 0.6. Note that the DVD has a track pitch of 0.74 μm and a shortest pit length of 0.4 μm, and has a density less than half that of a CD track pitch of 1.6 μm and the shortest pit length of 0.83 μm.

  This optical pickup device for recording / reproducing DVD, which is a new optical disc, requires compatibility with a CD having a transparent substrate thickness of 1.2 mm for a DVD having a transparent substrate thickness of 0.6 mm. Various studies have been made. As one of them, an optical pickup device that reproduces a DVD and a CD with one short wavelength semiconductor laser (light source) and one condensing optical system as described in Patent Document 1 has been proposed.

  In recent years, with the widespread use of CD-R (write-once compact disc), which is a writable optical disc, compatibility with this CD-R is also required as an optical pickup device. However, an optical pickup device using one short-wavelength semiconductor laser as described in the above publication cannot record / reproduce with respect to a CD-R. This is because the reflectance of the CD-R is lowered on the short wavelength side, and required signals (reproduction signal, focus error signal, tracking error signal) cannot be obtained.

Therefore, as described in Patent Document 2, there has been proposed an optical pickup device in which two optical sources are provided for each corresponding optical disc (for DVD and for CD-R) after having one optical system.
JP 7-57271 A JP-A-8-55363

  However, the optical pickup device requires assembly with high precision. Thus, when the number of parts of the optical pickup device is increased, it becomes difficult to assemble with high precision, as well as the work required for assembly. Efficiency deteriorates and productivity decreases. Furthermore, if each of these components is fixed in a discrete state in the optical pickup device, each changes (deforms) due to temperature change (heat) and aging, resulting in an arrangement different from the predetermined arrangement and achieving the desired performance. The problem of disappearing arises.

  Therefore, in the present invention, in an optical pickup device that records / reproduces a plurality of optical information recording media, the assembly of the device is simplified, the working efficiency is improved, and an optical pickup device that is resistant to temperature change and secular change, and It is an object to provide the light source unit.

  (1) A light beam emitted from a light source is condensed on an information recording surface by a condensing optical system via a transparent substrate of an optical information recording medium, and information is recorded on the information recording surface or information on the information recording surface is reproduced. (Recording / reproducing) An optical pickup device, wherein the optical information recording medium is a first optical information recording medium having a transparent substrate thickness t1 and a transparent substrate having a thickness t2 (where t2 ≠ t1). In an optical pickup device using a two-optical information recording medium, a first light source for recording / reproducing the first optical information recording medium and a second light source for recording / reproducing the second optical information recording medium And a light detection means for receiving and detecting the light beam reflected from the information recording surface, and guiding the light beam emitted from the light source to the optical information recording medium and detecting the light beam reflected by the information recording surface of the optical information recording medium. Emanating from the light source to lead to means Changing means for changing the reflected light beam and / or the light beam reflected by the information recording surface, and the first light source, the second light source and the light detecting means are unitized. .

  (2) The optical pickup device according to (1), wherein the first light source, the second light source, and the light detection unit are arranged adjacent to each other.

  (3) According to (1) or (2), at least one of the first light source, the second light source, and the light detection means is configured to be able to adjust a position in the unit. Optical pickup device.

  (4) The optical pickup device according to any one of (1) to (3), wherein the changing unit is unitized with the first light source, the second light source, and the light detecting unit.

  (5) The optical pickup device according to any one of (1) to (4), wherein the changing unit is configured by a hologram.

  (6) The light beam emitted from one of the first light source and the second light source is incident obliquely on the condensing optical system. Any one of (1) to (5) The optical pickup device described in 1.

  (7) The obliquely incident light source performs recording / reproducing of the optical information recording medium having a smaller numerical aperture on the optical information recording medium side of the condensing optical system necessary for recording / reproducing of the optical information recording medium. (6) The optical pickup device as described in (6) above.

  (8) The optical pickup according to any one of (1) to (5), further including a combining unit that combines the light beam emitted from the first light source and the light beam emitted from the second light source. apparatus.

  (9) The optical pickup device according to (8), wherein the combining unit is unitized together with the first light source, the second light source, and the light detecting unit.

  (10) The changing means and the synthesizing means are composed of a hologram functioning as a changing means formed on one surface of one optical member and a hologram functioning as a synthesizing means formed on the other surface. The optical pickup device according to (8) or (9), which is characterized.

  (11) The optical pickup device according to any one of (8) to (10), wherein the combining unit is arranged closer to the optical information recording medium than the changing unit.

  (12) The combining means includes a light source for recording / reproducing the optical information recording medium having a smaller numerical aperture on the optical information recording medium side of the condensing optical system necessary for recording / reproducing of the optical information recording medium. The optical pickup device according to any one of (8) to (11), wherein the optical path of the emitted light beam is changed to be combined with the light beam emitted from the other light source.

  (13) In a light source unit of an optical pickup device in which a first semiconductor laser and a second semiconductor laser having a wavelength different from that of the first semiconductor laser are integrated, a light emission direction of the first semiconductor laser and the second semiconductor A light source unit of an optical pickup device, wherein a light emitting direction of a laser is the same direction, and the first semiconductor laser and the second semiconductor laser are stacked with a conductive layer interposed therebetween.

  According to the present invention, in an optical pickup device that records / reproduces a plurality of optical information recording media, the assembly of the device can be simplified, the working efficiency can be improved, and the optical pickup device can be resistant to temperature changes. .

  The present invention will be described below with reference to the drawings. In the following description, the alternate long and short dash line in the drawings represents the optical axis, the thin line represents the light beam emitted from the first light source (however, the peripheral light beam is limited by the diaphragm), and the broken line represents the second light source. (In the case where the same luminous flux emitted from the first light source out of the luminous flux emitted from the second light source is represented by a thin line).

(First embodiment)
A first embodiment will be described. FIG. 1 is a schematic configuration diagram of an optical pickup device 10.

  The pickup apparatus 10 according to the present embodiment records / reproduces a plurality of optical disks 20 having different thicknesses of the transparent substrate 21 as the optical disk 20 that is an optical information recording medium (records information on the information recording surface 22 of the optical disk 20 or records information). (Reproducing information on the recording surface 22 is also referred to as recording / reproducing). Hereinafter, the plurality of optical discs 20 will be described as a first optical disc having a transparent substrate thickness t1 and a second optical disc having a thickness t2 different from the transparent substrate thickness t1 of the first optical disc. In addition, the required numerical aperture on the optical disk side of the condensing optical system (described later) necessary for recording / reproducing the first optical disk is NA1, and the condensing optical system necessary for recording / reproducing the second optical disk is NA1. The required numerical aperture on the optical disk side is NA2. (In the following description, since the first optical disk is an information recording medium having a higher density than the second optical disk, NA1> NA2). In the following description, DVD (including DVD-RAM) refers to the first optical disk. In this case, the thickness of the transparent substrate is t1 = 0.6 mm, and CD (including CD-R) is It points to the second optical disk, and in this case, t2 = 1.2 mm (that is, t1 <t2).

  In the pickup device 10 of the present embodiment, a first semiconductor laser 11 (wavelength λ = 610 nm to 670 nm) as a first light source and a second semiconductor laser 12 (wavelength λ = 740 nm to 870 nm) as a second light source are used as light sources. have. The first semiconductor laser 11 is a light source used when recording / reproducing the first optical disk, and the second semiconductor laser 12 is a light source used when recording / reproducing the second optical disk. The first semiconductor laser 11 and the second semiconductor laser 12 are used exclusively according to the optical disk to be recorded / reproduced.

  The combining unit 30 is a unit capable of combining the light beam emitted from the first semiconductor laser 11 and the light beam emitted from the second semiconductor laser 12. That is, the synthesizing unit 30 converts the light beam emitted from the first semiconductor laser 11 or the light beam emitted from the second semiconductor laser 12 to the first optical disk or the optical disc through one condensing optical system described later, respectively. In order to collect light on the second optical disk, the optical path is the same (may be substantially the same). In the present embodiment, the synthesizing unit 30 is constituted by a polarizing prism (birefringent plate), and the light beam emitted from the first semiconductor laser 11 is passed as it is without changing the optical path as an ordinary ray, and the second semiconductor laser. The light beam emitted from 12 changes the optical path as an extraordinary ray. Note that a hologram may be used as the synthesizing means 30.

  The condensing optical system 13 condenses the light beam emitted from the first semiconductor laser 11 or the second semiconductor laser 12 on the information recording surface 22 via the transparent substrate 21 of the optical disc 20 to form a spot. It is. In the present embodiment, as the condensing optical system 13, a collimator lens 131 that converts a light beam emitted from a light source into parallel light (may be substantially parallel) and a light beam that has been converted into parallel light by the collimator lens 131 are collected. And an objective lens 132. As described above, in the present embodiment, since a plurality of optical discs are recorded / reproduced using one condensing optical system 13, the optical pickup device 10 can be realized with a low cost and a simple structure.

  In the present embodiment, the condensing optical system 13 is a so-called infinite condensing optical system 13 using a collimator lens 131 and an objective lens 132, but there is no collimator lens 131 and the light source (first semiconductor). Only the objective lens 132 that directly condenses the divergent light from the laser 11 or the second semiconductor laser 12), a so-called finite condensing optical system 13, a lens that reduces the divergence of the divergent light from the light source, or the light flux from the light source. It is also possible to use a so-called quasi-finite condensing optical system 13 using a lens that changes (coupling) the light into a convergent light and an objective lens 132 that condenses the light beam through these lenses.

  Further, a quarter wavelength plate 14 and a diaphragm 15 are provided in the optical path. The quarter-wave plate 14 changes the light transmitted through the collimator lens 131 from linearly polarized light to circularly polarized light, and the diaphragm 15 limits the light beam to a predetermined numerical aperture greater than or equal to the numerical aperture NA1. In the present embodiment, the diaphragm 15 is a diaphragm having a fixed numerical aperture, and does not require an extra mechanism and can achieve a reduction in cost. However, the numerical aperture NA2 is reduced during recording / reproduction of the second optical disk. The numerical aperture of the diaphragm 15 may be variable so as to limit to the corresponding numerical aperture.

  The changing unit 40 guides the light beam emitted from the light source (the first semiconductor laser 11 and the second semiconductor laser 12) to the optical disc 20, and the light detection unit 50 described later on the light beam reflected from the information recording surface 22 of the optical disc 20. Means for changing the optical path of the luminous flux emitted from the light source (the first semiconductor laser 11 and the second semiconductor laser 12) and / or the optical path of the luminous flux reflected from the information recording surface 22 of the optical disc 20 is there. That is, the changing means 40 is reflected between the changing means 40 and the optical disc 20 from the optical path of the light beam emitted from the light source (the first semiconductor laser 11 and the second semiconductor laser 12) and the information recording surface 22 of the optical disc 20. It is a means for making the optical path of the light beam the same. In this embodiment, the light beam is composed of a polarization hologram, and the light beam reflected from the information recording surface 22 of the optical disk 20 is diffracted without changing the optical path of the light beam emitted from the light source, and is passed to the light detection means 50 described later. Change to guide.

  Note that a polarizing hologram uses a birefringent medium (for example, lithium niobate) as a medium constituting the hologram, and the diffraction efficiency varies depending on the polarization direction of the light beam incident on the hologram. Is. By using in combination with the quarter-wave plate 14, the amount of light returning to the light detection means 50 can be increased, the S / N ratio of the signal can be improved, the return light to the light source can be suppressed, and laser noise can be reduced. .

  The light detecting means 50 is a means for receiving and detecting the light beam reflected from the information recording surface 22 via the changing means 40 (the optical path is changed by the changing means 40). The light detection means 50 detects a change in the light amount distribution of the light beam reflected from the information recording surface, and performs focus detection (focus error signal), track detection (tracking error signal), and information reading (not shown) by an arithmetic circuit (not shown). Playback signal). The focus detection and track detection can be performed by various known methods such as an astigmatism method, knife edge method, SSD method, phase difference detection (DPD) method, pushbull (PP) method, and three beam method. it can.

  The two-dimensional actuator 16 is a means for moving the objective lens 132, and includes a focusing control for moving based on the focus detection obtained by the arithmetic circuit and a tracking control for moving based on the track detection. The two-dimensional actuator (for focusing control) 16 of the present embodiment collects a beam spot (light beam emitted from the first semiconductor laser 11) on the information recording surface of the DVD during recording / reproduction of the first optical disk (DVD). The beam on the information recording surface of the CD is set so that the spot collected by the optical optical system is minimized (becomes the minimum circle of confusion) (best focus), and at the time of recording / reproduction of the second optical disc (CD). The objective lens 132 is moved to a front position closer to the objective lens 132 than the position where the spot (spot where the light beam emitted from the second semiconductor laser 12 is condensed by the condensing optical system) is the minimum circle of confusion.

  This is because when the second optical disc is recorded / reproduced, spherical aberration occurs due to the thickness t2 of the transparent substrate of the second optical disc becoming thicker than the thickness t1 of the transparent substrate of the first optical disc. At the rear position where the beam spot is the minimum circle of confusion, the spot size is large and pits (information) on the second optical disk cannot be read. However, at the front position, which is closer to the objective lens 132 than the position of the minimum circle of confusion, a spot larger than the minimum circle of confusion as a whole consisting of a nucleus in which the amount of light is concentrated in the center and flare that is unnecessary light around the nucleus. Is formed. Therefore, when recording / reproducing the second optical disk, the objective lens 132 is moved to the front side position, and this nucleus is detected by the light detection means 50, thereby performing focus detection, track detection, and information reading.

  As described above, in the optical pickup device 10, recording / reproduction of the first optical disk is performed by using the condensing optical system 13 to transmit the light beam emitted from the first semiconductor laser 11 to the information recording surface via the transparent substrate of the first optical disk. The light beam collected and reflected from the information recording surface is received by the light detection means, and recording / reproduction of the second optical disk is performed by the light collection optical system 13 using the light beam emitted from the second semiconductor laser 12. The light is condensed on the information recording surface via the transparent substrate of the second optical disk, and the light beam reflected from the information recording surface is received by the light detection means.

  Therefore, in the present embodiment, the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 are unitized. This will be described with reference to FIG. 2 which is a perspective view of the unit 60.

  The first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 are unitized as a unit 60. Here, “unit” or “unitized” in the present invention means that a unitized member or means can be integrated into the optical pickup device 10, that is, It is a state that can be assembled as one part when the apparatus is assembled.

  In the present embodiment, the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 are provided on the substrate 61 of the unit 60 to form a unit. Therefore, when assembling the optical pickup device 10, the optical pickup device 10 is not assembled while adjusting each member, but the unitized member can be assembled simply by attaching the unit 60. Can be simplified and work efficiency can be improved. Moreover, the structure is strong against aging and temperature changes. That is, by bringing individual parts close to each other, the amount of dimensional change due to mechanical stress, secular change, and temperature change is reduced, and the light sources 11 and 12 and the light detecting means 50 as viewed from the changing means 40 are close to each other. Therefore, it is easy to maintain the conjugate property.

  In the case of unitization, in the present embodiment, the light emitting point of the first semiconductor laser 11, the light emitting point of the second semiconductor laser 12, and the light receiving surface of the light detection means 50 are arranged on the same plane. However, they are not necessarily in the same plane. Further, as in the present embodiment, the emission surface (light emission point) of the first semiconductor laser 11 and the emission surface (light emission point) of the second semiconductor laser 12 are arranged close to each other in the same direction, so that A light receiving element (not shown) for detecting the rear emission light can also be used, and further cost reduction can be realized.

  Further, when configuring the unit 60, by providing at least one of the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 so that the position in the unit 60 can be adjusted. The relationship among the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 can be easily adjusted. In particular, the positional error among the first semiconductor laser 11, the second semiconductor laser 12 and the light detection means 50 can be absorbed by providing the unit 60 so as to be adjustable from the outside.

  In the present embodiment, the changing means 40 is provided in the unit 60 before the unit 60 is assembled to the optical pickup device 10. That is, the changing means 40 is unitized with the first semiconductor laser 11, the second semiconductor laser 12 and the light detecting means 50. As a result, it is possible to further simplify assembly and improve work efficiency. In particular, when the changing means 40 is provided in the unit 60, the adjustment after assembly can be easily performed by providing the changing means 40 in an adjustable manner.

  Further, in the present embodiment, the changing unit 40 is disposed on the light source side from the combining unit 30, or conversely, the combining unit 30 is disposed on the optical disc side from the changing unit 40. , The light beam emitted from the first semiconductor laser 11 and reflected from the first optical disk and the light beam emitted from the second semiconductor laser 12 and reflected from the second optical disk pass through different positions on the changing means 40. 2 (the hatched portion shown on the changing means 40 in FIG. 2), and each light beam can be changed in an arbitrary direction to the hologram as the changing means 40. In particular, in the present embodiment, the light beam reflected from the first optical disk and changed by the changing means 40 and the light beam reflected from the second optical disk and changed by the changing means 40 are at the same position on the light detection means 50. A hologram is formed so as to form an image. Therefore, in the present embodiment, the detection of the light beam reflected from the first optical disk and the detection of the light beam reflected from the second optical disk can be performed by the same light receiving element (light detection means 50), and cost reduction can be realized. .

  Instead of disposing the changing unit 40 closer to the light source than the combining unit 30 as in the present embodiment, the combining unit 30 may be disposed closer to the light source than the changing unit 40 as shown in FIG. In this case (FIG. 3), the synthesizing means 30 is composed of a polarization hologram, and for this purpose, the second semiconductor laser 12 is arranged to be inclined with respect to the first semiconductor laser 11. In this case (FIG. 3), the position where the light beam reflected from the first optical disk passes through the changing means 40 is the same as the position where the light beam reflected from the second optical disk passes through the changing means 40. The imaging positions on the light detection means 50 are different, and a light receiving element (light detection means 50) for detecting each light beam is provided. In this case (FIG. 3), in order to allow the light beam reflected from the optical disk to pass through the outer wall of the unit 60, the synthesizing means 30 is made smaller by that amount and an opening 62 is provided. In this case (FIG. 3), the first semiconductor laser 11, the second semiconductor laser 12, the light detecting means 50, and the synthesizing means 30 are provided in the unit 60 and unitized, but the changing means 40 is also unitized. Further, the quarter wavelength plate 14 may be bonded to the changing means 40 and integrated.

  Further, in the present embodiment, the first semiconductor laser 11 and the second semiconductor laser 12 are provided adjacent to each other when unitized. Therefore, when combining by the combining means 30, it is unnecessary for changing the optical path. It can be synthesized without giving a burden. Further, in the present embodiment, the optical path of the light beam emitted from the second semiconductor laser 12 used for recording / reproduction of the optical disk having the smaller required numerical aperture (that is, the second optical disk) is changed (that is, the required numerical aperture). The optical path of the light beam emitted from the first semiconductor laser 11 used for recording / reproduction of the first optical disk having a larger value is not changed), so that the recording / reproduction of the first optical disk, which requires more light condensing characteristics, can be performed satisfactorily. In addition, recording / reproduction of the second optical disk can be performed.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. 4 which is a schematic configuration diagram of the optical pickup device 10 of the second embodiment. In the first embodiment described above, the synthesizing means 30 and the changing means 40 are each constituted by separate optical members, but in this embodiment, they are constituted by one optical member. In addition, when using the same function and component as 1st Embodiment mentioned above, the same figure number is attached | subjected and it is the same as already demonstrated unless it refuses, and description is abbreviate | omitted.

  In the present embodiment, a hologram that functions as the changing means 40 is provided on the light source side surface of one optical member 70, and a hologram that functions as the combining means is provided on the optical disk side surface. Thereby, workability at the time of assembling the synthesizing unit 30 and the changing unit 40 to the optical pickup device 10 is improved. Further, in the present embodiment, the optical member 70 is provided in the unit 60 before the unit 60 is assembled to the optical pickup device 10. That is, the optical member 70 (the synthesizing unit 30 and the changing unit 40) is unitized together with the first semiconductor laser 11, the second semiconductor laser 12, and the light detecting unit 50. As a result, it is possible to further simplify assembly and improve work efficiency. In particular, by providing at least one of the first semiconductor laser 11, the second semiconductor laser 12 and the light detection means 50 so that the position in the unit 60 can be adjusted, the first semiconductor laser 11 and the second semiconductor laser are provided. The relationship between the laser 12 and the light detecting means 50 can be easily adjusted from the relationship between the synthesizing means 30 and the changing means 40. In particular, by providing the unit 60 so as to be adjustable from the outside, the unit 60 can be easily adjusted during assembly.

  In the present embodiment, since the changing means 40 is provided on the light source side surface of the optical member 70 and the combining means 30 is provided on the optical disk side surface, detection of the light beam reflected from the first optical disk and reflection from the second optical disk are performed. A light receiving element (not shown) of the light detecting means 50 that shares the light beam can be used. However, as shown in FIG. 5, the combining means 30 may be provided on the light source side surface of the optical member 70 and the changing means 40 may be provided on the optical disk side.

(Third embodiment)
Next, a third embodiment will be described based on FIG. 6 which is a schematic configuration diagram of the optical pickup device 10 of the third embodiment. In the first and second embodiments described above, the optical axis of the light beam emitted from the first semiconductor laser 11 and the optical axis of the light beam emitted from the second semiconductor laser 12 are matched by using the combining means 30. In this embodiment, the light beam emitted from one light source is configured to enter the condensing optical system 13 from an oblique direction. Is. In addition, when using the same function and component as 1st Embodiment mentioned above, the same figure number is attached | subjected and it is the same as already demonstrated unless it refuses, and description is abbreviate | omitted.

  In the present embodiment, the light beam emitted from the second semiconductor laser 12 used for recording / reproduction of the second optical disk having the smaller required numerical aperture is configured to enter from the oblique direction of the condensing optical system 13. is doing. On the other hand, the light beam emitted from the first semiconductor laser 11 used for recording / reproduction of the first optical disk having the larger required numerical aperture is not incident on the condensing optical system obliquely (in other words, the condensing optical system 13). And the optical axis of the light beam emitted from the first semiconductor laser 11 coincide with each other). Accordingly, the synthesizing means 30 is omitted.

  With this configuration, in this embodiment, the light beam emitted from one of the light sources is incident on the condensing optical system 13 from an oblique direction. Therefore, the synthesizing means required in the first and second embodiments is used. 30 is not necessary, so that not only cost reduction can be realized, but also the efficiency of assembly work can be improved. In the present embodiment, since the light beam emitted from the second semiconductor laser 12 having a small numerical aperture is incident on the condensing optical system 13 from an oblique direction, the first optical disc that requires more condensing characteristics is used. Recording / reproduction of the second optical disk with a slight margin can be performed without impairing recording / reproduction.

  In the present embodiment, since the distance from the collimator lens 131 to the stop 15 is set to be substantially equal to the focal length of the collimator lens 131, the center of the light beam of the second semiconductor laser 12 is the stop 15. The symmetry of the light quantity distribution of the light beam incident on the objective lens 132 is improved. Therefore, it is possible to reduce the light amount distribution fluctuation when the objective lens 132 is shifted, and to widen the tracking range. If the distance from the diaphragm 15 to the objective lens 132 is set to be the same as the focal length of the objective lens 132, the light beam traveling from the objective lens 132 to the second optical disk is parallel to the optical axis of the objective lens 132. preferable.

  Further, in the present embodiment, in the optical path between the changing means 40 and the optical disc, the wavelength selectivity that acts as a concave lens at the wavelength of the second semiconductor laser 12 and does not act at the wavelength of the first semiconductor laser 11. By providing the hologram element, it is possible to correct the spherical aberration in the over direction caused by the increase in the thickness of the transparent substrate. That is, by providing a hologram element that acts as a concave lens at the wavelength of the second semiconductor laser 12 in the optical path, an optical disk with a thick transparent substrate at the wavelength of the second semiconductor laser 12 and a thin transparent substrate at the wavelength of the first semiconductor laser are provided. The optical pickup device 10 corresponding to the optical disk can be obtained. In this case, the grating structure depth of the hologram element is such that the optical path length is nλ1 (where n = integer) at the wavelength λ1 of the first semiconductor laser 11 and (n + 1/2) at the wavelength λ2 of the second semiconductor laser 12. This can be done easily by selecting a depth that is a common multiple of λ2 (where n = integer).

  In the first to third embodiments described in detail above, each of the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 is provided directly on the substrate 61 of the unit 60. Will never be. For example, as shown in FIG. 7A, two semiconductor lasers 11 and 12 may be stacked. That is, a heat sink 81 for releasing heat associated with light emission is essential for the semiconductor laser, but the first semiconductor laser 11 is provided on the conductive surface on the heat sink 81. Then, aluminum as a conductive layer is vapor-deposited on the first semiconductor laser 11, and the second semiconductor laser 12 is laminated on the conductive layer (that is, on the first semiconductor laser 11). Then, aluminum as a conductive layer is deposited on the second semiconductor laser 12. On the other hand, a light detection means 50 is provided below the first semiconductor laser 11. Then, the wires 82 to 84 are bonded to the respective conductive layers, and the wires 82 to 84 for supplying a driving current are provided. That is, the first semiconductor laser 11 emits light when a drive current is passed between the wires 82 and 83, and the second semiconductor laser 12 emits light when a drive current is passed between the wires 83 and 84 (the terminal 83 serves as a common electrode). The conductive layer between the first semiconductor laser 11 and the second semiconductor laser 12 becomes a common conductive layer). In the optical pickup device, the first semiconductor laser 11 and the second semiconductor laser 12 emit light exclusively, and thus the configuration is preferable in terms of space saving and simplification.

  In this case (FIG. 7A), the light beams emitted from the first semiconductor laser 11 and the second semiconductor laser 12 are elliptical shapes having a full width at half maximum of about 10 ° and 30 °, respectively, and have a wide divergence angle. The first semiconductor laser 11 and the second semiconductor laser 12 are arranged in the direction. In addition, the spot size in the tangential direction can be reduced by making this arrangement direction the tangential direction of the optical disk as an optical pickup device. Furthermore, as in the third embodiment, even when one of the light beams is an off-axis light beam of the condensing optical system, asymmetry hardly occurs in the light amount change when the objective lens 16 is shifted by tracking. Furthermore, the astigmatism caused by oblique incidence on the condensing optical system can be canceled by the astigmatism of the semiconductor laser. In this case, the first semiconductor laser 11 is arranged on the optical axis, the second semiconductor laser 12 is arranged outside the optical axis, and the astigmatism of the second semiconductor laser 12 is selected to be larger than that of the first semiconductor laser 11. It is preferable.

  By laminating the two semiconductor lasers 11 and 12 in this way, the deviation between the light emission point 111 of the first semiconductor laser 11 and the light emission point 121 of the second semiconductor laser 12 can be set to about 100 μm. The semiconductor lasers 11 and 12 can be brought closer to each other than being arranged on the substrate 61. In addition, one of the semiconductor lasers (in this example, the first semiconductor laser 11) can provide the light emitting point 111 directly on the heat sink, which is advantageous for heat dissipation.

  Further, in this case (FIG. 7A), the light emitted from each of the stacked semiconductor lasers 11 and 12 is changed to other semiconductors by arranging the light emitting points 111 and 121 so as to be shifted in the optical axis direction. However, the present invention is not limited to this. As shown in FIG. 7B, the light emitting points 111 and 121 are on the same plane (including the light receiving surface of the light detecting means 50). It may be.

  In the example shown in FIG. 7B, not only the first semiconductor laser 11 and the second semiconductor laser 12 are provided on the same plane, but also on the side closer to the light emitting point 111 of the first semiconductor laser 11. Aluminum, which is a conductive layer, is vapor-deposited on the side surface, and laminated so that the side surface close to the light emitting point 121 of the second semiconductor laser 12 is in contact therewith, and the light emitting points 111 and 121 are laminated in close contact with each other. Thus, the light emitting points 111 and 121 are arranged close to each other within 10 μm. Therefore, in the example shown in FIG. 7B, when used in the first and second embodiments described above, the synthesizing means 30 can be omitted, and both the first semiconductor laser 11 and the second semiconductor laser are collected. Since it can be used almost on the optical axis of the optical optical system, it is preferable in terms of light collecting performance.

  In the first to third embodiments described in detail above, the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 are provided on the substrate 61 of the unit 60 so as to be aligned. Not limited to this, the light detection means 50 may be provided at a position different from the direction in which the first semiconductor laser 11 and the second semiconductor laser 12 are arranged. In addition, the light beams emitted from the first semiconductor laser 11 and the second semiconductor laser 12 are directly incident on the combining unit 30 or the changing unit 40. However, they may be incident after the optical path is changed by a mirror or the like. . An example of this is shown in FIG.

  In FIG. 8, the light receiving means 50 has a light receiving element 52 formed on a silicon substrate 51 by a semiconductor process. The silicon substrate 51 is provided with two concave portions 53 and two mirror portions 54. Then, the first semiconductor laser 11 and the second semiconductor laser 12 are mounted in the recess 53. Therefore, the light detection means 50 is disposed at a position different from the direction in which the first semiconductor laser 11 and the second semiconductor laser 12 are arranged, and the light beams emitted from the first semiconductor laser 11 and the second semiconductor laser 12 are changed. After that, the light can enter the combining means 30 or the changing means 40.

  Further, as shown in FIG. 8, a more compact unit 60 can be configured by mounting the semiconductor lasers 11 and 12 on the substrate 51 of the light receiving element 52. In addition, the number of parts can be reduced to improve precision assembly and work efficiency. Although the mirror unit 54 is formed in FIG. 8, the combining unit 30 may be mounted instead of the mirror unit 54.

  In the above description, CD (including CD-R) refers to the second optical disk, and the second semiconductor laser 12 is the light source for recording / reproducing the second optical disk. 12 may be a light source for recording / reproducing a CD-R, and recording / reproducing of the CD may be performed by the first semiconductor laser 11.

(Specific example 1)
FIG. 9 shows a specific example of the arrangement of the units 60 used in FIGS. 1, 4, and 6 in the optical pickup device 10 described above. FIG. 9A is a diagram showing the arrangement relationship of the units 60, and FIG. 9B is an enlarged schematic diagram of a hologram element that is the changing means 40 of this specific example. In this specific example, the wavelength of the first semiconductor laser 11 is λ1 = 640 nm, the wavelength of the second semiconductor laser 12 is λ2 = 790 nm, the light emitting points of the hologram element 40 as the changing means 40 and the light sources (11, 12), It is assumed that the distance from the light receiving surface of the light detection means 50 is L = 10 mm, the average pitch p of the hologram element 40 is 5 μm, and the first semiconductor laser 11 is disposed on the optical axis of the condensing optical system.

  The light beam emitted from the first semiconductor laser 11 travels straight through the hologram element 40 as zero-order light, is reflected from the information recording surface of the first optical disk, travels along the original optical path, and enters the hologram element 40 again. In this specific example, since the average pitch p of the hologram element 40 is 5 μm, the ± 1st order light is diffracted by ± λ1 / p (≈ ± 7.3 °) and d1 (= 1.28 mm) from the first semiconductor laser 11. An image is formed on the light detection means 50 at a distance. Note that, by making the hologram element 40 blazed as in this specific example, it is possible to increase the diffraction efficiency to only one of the ± first-order lights.

  Similarly to the above, the light beam emitted from the second semiconductor laser 12 travels straight through the hologram element 40 as zero-order light, is reflected from the information recording surface of the first optical disc, retraces the original optical path, and enters the hologram element 40. To do. The hologram element 40 diffracts about 9 ° at this wavelength λ2, and forms an image on the light detection means 50 at a distance d2 (= 1.58 mm) from the second semiconductor laser 12.

  Thus, the first semiconductor laser 11 and the second semiconductor laser 12 are separated by 0.3 mm, the center of the light receiving surface of the light detection means 50 is 1.28 mm from the first semiconductor laser 11, and the first semiconductor laser 12 is 1. 58mm apart and placed on the same plane.

  As a result of recording / reproducing of the optical disk using the unit 60 arranged in this way, the light beam reflected from the DVD and the light beam reflected from the CD can be detected by the same light detection means 50, and Both DVD and CD can be recorded / reproduced satisfactorily.

(Specific example 2)
Next, a specific example including a specific configuration of the light detection means 50 is shown in FIG. Since FIG. 10 is a diagram schematically showing the configuration in the unit 60, the description of the unit 60 and the like is omitted. The light receiving elements of the first semiconductor laser 11, the second semiconductor laser 12, and the light detection means 50 are arranged on the same plane. The first semiconductor laser 11 and the second semiconductor laser 12 are individually provided on the heat sink 81, and one photodetector 85 is provided on the side opposite to the light emitting points 111 and 121. . The photodetector 85 controls the current of the semiconductor lasers 11 and 12 with an APC (auto power control) circuit so that the amount of light emitted from the semiconductor lasers 11 and 12 becomes a predetermined light amount. In the present embodiment, the semiconductor lasers 11 and 12 are detected by a single photodetector 85.

  In this specific example, the focus error signal is detected by the knife edge method. For this reason, eight light receiving elements (light receiving surfaces) A1 to D2 are provided on the light receiving surface of the light detecting means 50. Is provided. Further, a hologram element is used as the changing means 40. This hologram element is divided into four parts A to D, and the division A is average pitch p so that each divided surface forms an image on the light receiving surface of the light detecting means 50. = 4.25 μm, the average pitch p of division B = 4.75 μm, the average pitch p of division C = 5.25 μm, and the average pitch p of division D = 5.75 μm.

  In this specific example, the two semiconductor lasers 11 and 12 and the light detection means 50 are fixed in a unit 60 (not shown) with a predetermined accuracy, and the hologram element 40 is connected to the optical axis. By adjusting and fixing in the direction and the rotation direction, good adjustment can be performed, and the operation becomes very simple.

In this specific example, the focus error signal FE is
FE = (A2 + B1 + C1 + D2) − (A1 + B2 + C2 + D1)
Can be obtained by: A1 to D2 are the amounts of light detected at the respective light receiving surfaces.

In this specific example, the tracking error signal TE is the phase difference detection (DPD) method,
TE = (A1 + A2 + C1 + C2) − (B1 + B2 + D1 + D2)
In the case of the push bull (PP) method,
TE = (A1 + A2 + B1 + B2) − (C1 + C2 + D1 + D2)
The information signal can be detected by the total sum A1 + A2 + B1 + B2 + C1 + C2 + D1 + D2. A1 to D2 are the amounts of light detected at the respective light receiving surfaces.

  In the case of this specific example, the light receiving surfaces A1 to D2 increase in the light receiving area as they move away from the semiconductor lasers 11 and 12 (in detail, the same as the direction in which the semiconductor lasers 11 and 12 and the light detection means 50 are arranged). By making it longer in the direction), it is possible to absorb the influence of the variation in the diffraction angle by the changing means 40 due to the difference in the wavelengths of the semiconductor lasers 11 and 12. That is, the light flux of the second semiconductor laser 12 is more in the same direction than the light flux of the first semiconductor laser 11 in the direction in which the semiconductor lasers 11 and 12 and the light detection means 50 are aligned (the light receiving surface A1). , The distance from A2 to D1, D2 is extended), so that a light receiving surface is provided so as to cover the extended range.

It is a schematic block diagram of the optical pick-up apparatus of 1st Embodiment. It is a perspective view of a unit. It is a schematic block diagram of the optical pick-up apparatus of the modification of 1st Embodiment. It is a schematic block diagram of the optical pick-up apparatus of 2nd Embodiment. It is a schematic block diagram of the optical pick-up apparatus of the modification of 2nd Embodiment. It is a schematic block diagram of the optical pick-up apparatus of 3rd Embodiment. It is a figure which shows the modification of a unit. It is a perspective view which shows the modification of a unit. It is a figure which shows the specific example 1. FIG. It is a figure which shows the specific example 2. FIG.

Explanation of symbols

  10 Optical pickup device.

11 First semiconductor laser (first light source)
12 Second semiconductor laser (second light source)
13 Condensing optical system 15 Aperture 20 Optical disc (optical information recording medium)
DESCRIPTION OF SYMBOLS 21 Transparent substrate 22 Information recording surface 30 Synthesis | combination means 40 Change means 50 Photodetection means 60 Unit 70 Optical member 81 Heat sink 111,121 Light emission point

Claims (13)

The light beam emitted from the light source is condensed on the information recording surface via the transparent substrate of the optical information recording medium by the condensing optical system, and information is recorded on the information recording surface or information on the information recording surface is reproduced (recording / recording). A reproduction) optical pickup device, wherein the optical information recording medium is a first optical information recording medium having a transparent substrate thickness of t1 and a second optical information having a thickness of the transparent substrate of t2 (where t2 ≠ t1). In an optical pickup device used with a recording medium,
A first light source for recording / reproducing the first optical information recording medium;
A second light source for recording / reproducing the second optical information recording medium;
A light detecting means for receiving and detecting a light beam reflected from the information recording surface;
The light beam emitted from the light source and / or the information recording surface is guided so that the light beam emitted from the light source is guided to the optical information recording medium and the light beam reflected by the information recording surface of the optical information recording medium is guided to the light detection means. Changing means for changing the reflected luminous flux,
An optical pickup device, wherein the first light source, the second light source, and the light detection means are unitized. The optical pickup device according to claim 1, wherein the first light source, the second light source, and the light detection unit are arranged adjacent to each other. 3. The optical pickup device according to claim 1, wherein at least one of the first light source, the second light source, and the light detection unit is configured to be able to adjust a position in the unit. The optical pickup device according to claim 1, wherein the changing unit is unitized with the first light source, the second light source, and the light detecting unit. The optical pick-up apparatus according to claim 1, wherein the changing unit includes a hologram. The light according to claim 1, wherein a light beam emitted from one of the first light source and the second light source is incident obliquely on the condensing optical system. Pickup device. The obliquely incident light source is a light source for recording / reproducing an optical information recording medium having a smaller numerical aperture on the optical information recording medium side of a condensing optical system required for recording / reproducing of the optical information recording medium. The optical pickup device according to claim 6, wherein: The optical pickup device according to claim 1, further comprising a combining unit that combines the light beam emitted from the first light source and the light beam emitted from the second light source. 9. The optical pickup apparatus according to claim 8, wherein the combining unit is unitized with the first light source, the second light source, and the light detection unit. The changing means and the synthesizing means are composed of a hologram functioning as changing means formed on one surface of one optical member and a hologram functioning as synthesizing means formed on the other surface. The optical pickup device according to claim 8 or 9. 11. The optical pickup device according to claim 8, wherein the synthesizing unit is disposed closer to the optical information recording medium than the changing unit. The combining means is emitted from a light source for recording / reproducing the optical information recording medium having a smaller numerical aperture on the optical information recording medium side of the condensing optical system necessary for recording / reproducing of the optical information recording medium. The optical pickup device according to claim 8, wherein the optical path is changed to be combined with a light beam emitted from the other light source. In the light source unit of the optical pickup device in which the first semiconductor laser and the second semiconductor laser having a wavelength different from the first semiconductor laser are integrated,
The light emitting direction of the first semiconductor laser and the light emitting direction of the second semiconductor laser are the same direction, and the first semiconductor laser and the second semiconductor laser are stacked with a conductive layer interposed therebetween. A light source unit for an optical pickup device.

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