JP2008117445A - Optical pickup and optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical pickup compatible with a plurality of kinds of optical disks using optical beams of the same wavelength with a simple and small configuration. <P>SOLUTION: The optical pickup is provided a first light path separation means 40 and a second light path separation means 50. The first light path separation means guides the optical beam of which polarization direction is controlled according to the kind of the loaded optical disk to a first objective 41 based on the polarization direction and emits the reflected light beam from a first type optical disk to a direction opposite to the incident direction of the optical beam or transmits and emits the beam as it is. The second light path separation means guides the optical beam which has passed through the first light path separation means 40 to a second objective 51 based on its polarization direction, emits the reflected light beam from a second type optical disk to the direction opposite to the incident direction of the optical beam, and transmits and emits the reflected light beam from the first type optical disk emitted from the first light path separation means 40 as it is based on its polarization direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup and an optical disc apparatus, and is suitable for application to, for example, an optical pickup compatible with a plurality of types of optical discs.

In recent years, a Blu-ray Disc (registered trademark, hereinafter also referred to as BD) using a blue laser having a wavelength of 405 [nm] has been put into practical use. The Blu-ray disc uses a laser with a much shorter wavelength than a conventional optical disc, and therefore has a recording capacity several times that of a DVD having the same disc diameter. A three-wavelength optical disc drive that can use this Blu-ray disc together with a conventional CD (Compact Disk) or DVD (Digital Versatile Disk) has also been proposed (for example, see Patent Document 1).
JP 2006-134474 A

  Incidentally, as a large-capacity optical disk using a blue laser, a standard called HD-DVD is put into practical use in addition to the above-described Blu-ray disk. Further, if both the Blu-ray disc and the HD-DVD can be used in the optical disc apparatus, it is considered that convenience is further enhanced.

  However, although HD-DVD uses laser light having the same wavelength (405 [nm]) as Blu-ray Disc, there are differences in the thickness of the cover layer of the disc and the numerical aperture of the objective lens. It is difficult to design an objective lens. Therefore, it is necessary to provide an objective lens dedicated to the Blu-ray disc and an objective lens dedicated to the HD-DVD in the optical pickup compatible with both the Blu-ray disc and the HD-DVD.

  On the other hand, since the laser beam for Blu-ray disc and the laser beam for HD-DVD are both blue laser beams having a wavelength of 405 [nm] as described above, these two laser beams are emitted from a common laser light source. In this case, it is considered that the optical pickup can be simplified and miniaturized, and further the cost can be reduced.

  FIG. 1 shows an optical pickup 1 having such a configuration. As a light beam light source, a laser diode that emits laser light having a wavelength of 405 [nm] common to a Blu-ray disc (hereinafter also referred to as BD) and HD-DVD. 2 has.

  The laser diode 2 emits a light beam with a light amount corresponding to a drive current supplied from a control unit (not shown) and enters the grating 3. The grating 3 diffracts the light beam from the laser diode 2 and branches into a main beam composed of zero-order light for recording and reproduction and two sub-beams composed of ± first-order light for tracking control to form a collimator lens 4. Incident.

  The collimator lens 4 converts a light beam (main beam and two sub-beams) made of incident diverging light into parallel light and enters the polarization controller 5. The polarization control unit 5 is composed of, for example, a liquid crystal optical element, and is configured by enclosing a liquid crystal between two transparent covers. Transparent electrodes are provided on the inner surfaces of the two covers, respectively, and by changing the alignment direction of the liquid crystal molecules by applying a voltage between the transparent electrodes, the light passing through the polarization controller 5 is changed. The polarization direction can be changed.

  When recording or reproducing with respect to the Blu-ray disc 100A, a control unit (not shown) of the optical disc apparatus controls the voltage applied to the polarization control unit 5 so that the light transmitted through the polarization control unit 5 becomes P-polarized light. As a result, the light beam emitted from the polarization controller 5 enters the polarization beam splitter 6 in the P-polarized state.

  The polarization reflection surface of the polarization beam splitter 6 has optical characteristics determined so as to reflect P-polarized light and transmit S-polarized light. As a result, the polarization beam splitter 6 reflects the light beam (main beam and two sub beams) made of P-polarized light by 90 ° and enters the quarter-wave plate 7. The quarter-wave plate 7 converts the light beam from the polarization beam splitter 6 from P-polarized light to circularly-polarized light and enters the objective lens 8.

  The objective lens 8 has a focal length and a numerical aperture suitable for a Blu-ray disc, and focuses the incident light beam on the recording surface of the Blu-ray disc 100A and reflects it on the recording surface. The reflected light beam is received and reincident on the quarter-wave plate 7.

  The quarter-wave plate 7 converts the reflected light beam from circularly polarized light to S-polarized light that is orthogonal to the forward path, and enters the polarizing beam splitter 6.

  As described above, since the polarization reflection surface of the polarization beam splitter 6 has optical characteristics determined so as to reflect P-polarized light and transmit S-polarized light, the polarized beam splitter 6 is a reflected light beam composed of S-polarized light. , And irradiates the photodetector 13 through the condenser lens 12.

  The photodetector 13 generates various detection signals such as a reproduction signal and an error signal in accordance with the amount of the reflected light beam (main reflected beam and two sub reflected beams) from the Blu-ray disc 100A, and the signal of the optical disc apparatus. Output to a processing unit (not shown).

  On the other hand, when recording or reproducing on the HD-DVD 100B, a control unit (not shown) of the optical disc apparatus controls the voltage applied to the polarization control unit 5 so that light transmitted through the polarization control unit 5 becomes S-polarized light. To do. As a result, the light beam emitted from the polarization controller 5 enters the polarization beam splitter 6 in the S-polarized state.

  As described above, the polarization reflecting surface of the polarizing beam splitter 6 has optical characteristics determined so as to reflect P-polarized light and transmit S-polarized light. Therefore, the polarizing beam splitter 6 has a light beam composed of S-polarized light ( Main beam and two sub beams), and enters the quarter-wave plate 10 via the mirror 9. The quarter-wave plate 10 converts the light beam from the mirror 9 from S-polarized light to circularly-polarized light and enters the objective lens 11.

  The objective lens 11 has a focal length and a numerical aperture suitable for HD-DVD, and focuses the incident light beam to focus on the recording surface of the HD-DVD 100B and is reflected by the recording surface. The reflected light beam is received and reincident on the quarter-wave plate 10.

  The quarter-wave plate 10 converts the reflected light beam from circularly polarized light into P-polarized light that is orthogonal to the forward path, and enters the polarizing beam splitter 6. Since the polarization reflection surface of the polarization beam splitter 6 is optically defined so as to transmit P-polarized light and reflect S-polarized light, the polarization beam splitter 6 reflects a reflected light beam composed of P-polarized light. The light is irradiated to the photodetector 13 through the condenser lens 12.

  Thus, the optical pickup 1 controls the polarization direction of the light beam emitted from the laser diode 2 by the polarization control unit 5, thereby recording or recording using the objective lens 8 or 11 corresponding to the type of the mounted optical disk 100. Perform playback.

  In practice, rising mirrors (not shown) are interposed between the objective lens 8 and the polarizing beam splitter 6 and between the objective lens 11 and the mirror 9, respectively, and the optical path of the light beam is set by these rising mirrors. The optical path from the laser diode 2 to the mirror 9 and the optical path from the polarization beam splitter 6 to the photodetector 13 are arranged in parallel with the optical disk 100 by being incident on the objective lenses 8 and 11 after being bent by 90 °, and the optical pickup. 1 is made thinner.

  As an arrangement method of the two objective lenses 8 and 11 in the optical pickup 1 having such a configuration, as shown in FIG. 2, the objective lenses 8 and 11 are arranged in parallel in the radial direction (radial direction) of the optical disc 100 ( When this arrangement is called a radial arrangement, as shown in FIG. 3, a method of arranging the objective lenses 8 and 11 in parallel in a direction perpendicular to the radius of the optical disc 100 (tangential direction) (this arrangement is called a tangential arrangement). There are two possible ways.

  Also, with respect to the direction in which the light beams are introduced into the objective lenses 8 and 11, a method of entering from the radial direction of the optical disc 100 (this incident direction is referred to as radial incidence) and a method of entering from the tangential direction of the optical disc 100 (this There are two possible cases: the incident direction is called tangential incidence.

  By combining these two types of lens arrangements and two types of incident directions, a total of four types of optical pickup optical configurations can be considered. The configuration of the conventional optical pickup 1 shown in FIG. 1 is limited to either radial arrangement and tangential incidence or tangential arrangement and radial incidence.

  Here, when the objective lens has a radial arrangement as shown in FIG. 2, the innermost objective lens 11 is used to access the innermost circumference of the optical disc 100, or the outer peripheral objective lens 8 is used. When accessing the outermost periphery of the optical disc 100, the thread movement stroke of the optical pickup 1 becomes larger than that in the case of the tangential arrangement as shown in FIG. 3, and therefore the size of the optical pickup 1 in the radial direction is increased. There is a problem that a restriction occurs.

  In general, since the optical pickup performs tracking control by moving the objective lens in the radial direction (so-called lens shift), the above-described rising mirror causes the light beam to enter the objective lens even when the objective lens is shifted. In order to obtain, a reflective surface area enough to cover the lens shift amount of the objective lens is necessary.

  When the light beam is incident radially, the incident direction of the light beam with respect to the reflecting surface of the rising mirror is the same as the lens shift direction of the objective lens. There is also a problem that the vertical dimension of the upper mirror increases, which increases the height of the optical pickup.

  The present invention has been made in consideration of the above points, and intends to propose an optical pickup and an optical disc drive that are compatible with a plurality of types of optical discs using light beams of the same wavelength with a simple and compact configuration.

  In order to solve such a problem, in the present invention, a light source that emits a light beam, a first objective lens that corresponds to the first type of optical disk, and a second objective lens that corresponds to the second type of optical disk, Based on the polarization direction, the polarization direction control means for controlling the polarization direction of the light beam emitted from the light source according to the type of the mounted objective lens, and the light beam whose polarization direction is controlled by the polarization direction control. First reciprocating optical path separating means that guides the light to the first objective lens and emits the reflected light beam from the first type optical disc in the direction opposite to the incident direction of the light beam or transmits the light beam as it is. And guiding the light beam that has passed through the first reciprocating optical path separating means to the second objective lens based on the polarization direction, and the reflected light beam from the second type optical disc A second light beam that is emitted in the direction opposite to the incident direction of the beam and that is reflected from the first type optical disk emitted from the first reciprocating optical path separating means is transmitted and emitted as it is based on the polarization direction. The optical disc apparatus is provided with a reciprocating optical path separating means.

  Accordingly, the first and second reciprocating optical path separation units can realize the rising mirror function for raising the light beam toward the optical disc and the reciprocating optical path separating function for separating the light beam and the reflected light beam. Further, the reflected light beam can be emitted from the side opposite to the incident direction of the light beam in the reciprocating optical path separation unit, and therefore operates as a rising mirror when the first and second objective lenses are arranged in the tangential direction. The light beam can be incident on the first and second round-trip optical path separators from the tangential direction, whereby the height dimension of the first and second round-trip optical path separators can be reduced.

  According to the present invention, the rising mirror function for raising the light beam toward the optical disk and the reciprocating optical path separating function for separating the light beam and the reflected light beam can be realized by the first and second reciprocating optical path separation units. At the same time, when the first and second objective lenses are arranged in the tangential direction, the light beam is incident on the first and second reciprocating optical path separation units operating as the rising mirror from the tangential direction. The height dimension can be reduced, and thus an optical pickup and an optical disk drive corresponding to a plurality of types of optical disks using light beams having the same wavelength can be realized with a simple and small configuration.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) Overall Configuration of Optical Disc Device In FIG. 4, reference numeral 20 denotes an optical disc device to which the present invention is applied, which can play back two types of optical discs 100 of Blu-ray disc and HD-DVD.

  The optical disc device 20 is configured to be controlled by the control unit 21 as a whole, and when a reproduction instruction or the like from an external device (not shown) is received in a state in which the optical disc 100 is loaded, a drive unit from the control unit 21 is received. The information recorded on the optical disc 100 is read by controlling the signal processing unit 22 and the signal processing unit 23.

  In practice, the drive unit 22 rotates the optical disc 100 at a desired rotational speed by the spindle motor 24 based on the control of the control unit 21, and the sled motor 25 moves the optical pickup 26 in the tracking direction that is the radial direction of the optical disc 100. Further, the biaxial actuator 27 finely moves the objective lens unit 28 in two directions, ie, a focus direction and a tracking direction, which are directions in which the objective lens unit 28 approaches or separates from the optical disc 100.

  In parallel with this, the signal processing unit 23 causes the optical pickup 26 to irradiate a desired beam of the optical disc 100 with a light beam from the objective lens unit 28, generates a reproduction signal based on the detection result of the reflected light, and performs control. The reproduction signal is sent to an external device (not shown) via the unit 21.

  At this time, the optical pickup 26 condenses the emitted light beam using the objective lens 28A or 28B (FIG. 3) according to the type of the mounted optical disc 100, and irradiates the recording layer of the optical disc 100 with a focus. At the same time, the reflected light beam reflected by the focused recording layer is received by the objective lens and subjected to photoelectric conversion, and various detection signals are generated and supplied to the signal processing unit 23.

  The drive unit 22 drives the biaxial actuator 27 based on the focus error signal and tracking error signal supplied from the signal processing unit 23. The signal processing unit 23 performs predetermined signal processing on the reproduction signal supplied from the optical pickup 26 and then outputs the reproduction signal to the outside via the control unit 21.

(2) Configuration of Optical Pickup As shown in FIG. 5, the optical pickup 26 has a laser diode 31 that emits laser light having a wavelength of 405 [nm] common to Blu-ray discs and HD-DVDs as a light beam light source. is doing.

  The collimator lens 32 converts the light beam emitted from the laser diode 31 from divergent light into parallel light, and enters the polarization controller 33. The polarization controller 33 is a liquid crystal optical element, and is configured by enclosing a liquid crystal between two transparent covers. Transparent electrodes are provided on the inner surfaces of the two covers, respectively, and by changing the alignment direction of the liquid crystal molecules by applying a voltage between the transparent electrodes, the light passing through the polarization controller 33 is changed. The polarization direction can be changed.

  When recording or reproducing on the Blu-ray disc 100A, the control unit 21 of the optical disc apparatus 20 controls the voltage applied to the polarization control unit 33 so that the light transmitted through the polarization control unit 33 becomes S-polarized light. As a result, the light beam emitted from the polarization controller 33 enters the first reciprocating optical path separator 40 in the state of S polarization.

  In the polarization beam splitter 40A of the first reciprocating optical path separation unit 40, the optical characteristics of the polarization reflection surface 40B are determined so as to reflect S-polarized light and transmit P-polarized light. As a result, as shown in FIG. 6A, the first reciprocating optical path separator 40 reflects the S-polarized light beam by 90 ° and rises upward, and is provided on the upper surface of the polarizing beam splitter 40A. / 4 Enters the wavelength plate 40C. The quarter-wave plate 40CB converts the light beam from the first polarizing beam splitter 40A from S-polarized light to circularly-polarized light, and enters the objective lens 41 for the Blu-ray disc.

  The objective lens 41 has a focal length and a numerical aperture suitable for a Blu-ray disc, and condenses the incident light beam to focus on the recording surface of the Blu-ray disc 100A and is reflected by the recording surface. The reflected light beam is received and re-incident on the quarter-wave plate 40 </ b> C of the first reciprocating optical path separation unit 40.

  The quarter-wave plate 40C converts the reflected light beam from circularly polarized light into P-polarized light that is orthogonal to the forward path, and enters the first polarizing beam splitter 40A.

  As described above, the polarization reflecting surface 40B of the polarizing beam splitter 40A has optical characteristics determined so as to reflect S-polarized light and transmit P-polarized light. Therefore, the polarized reflecting surface 40B is reflected light that is P-polarized light. The beam is transmitted and incident on a quarter-wave plate 40D provided on the lower surface of the polarizing beam splitter 40A.

  A reflective surface 4OE is formed on the bottom surface of the quarter-wave plate 40D (that is, the surface opposite to the incident surface of the reflected light beam). For this reason, the light beam incident from the polarizing beam splitter 40A passes through the quarter-wave plate 40D, is reflected by the reflecting surface 40E, passes through the quarter-wave plate 40D again, and reenters the polarizing beam splitter 40A. To do. At this time, since the reflected light beam passes through the quarter-wave plate 40D before and after being reflected by the reflecting surface 40E, the reflected light beam re-entering the polarization beam splitter 40A is S-polarized light.

  As a result, the polarization beam splitter 40A reflects the reflected light beam, which is S-polarized light re-entered from the quarter-wave plate 40D, on the polarization reflection surface 40B.

  Thus, the first reciprocating optical path separation unit 40 guides the incident S-polarized light beam to the Blu-ray disc objective lens 41, and converts the reflected light beam from the Blu-ray disc 100A into the S-polarized light beam. The light exits from the direction opposite to the incident direction and enters the half-wave plate 35.

  The half-wave plate 35 converts the reflected light beam from the Blu-ray disc 100 </ b> A from S-polarized light to P-polarized light, and enters the second reciprocating optical path separating means 50.

  The second round-trip optical path separation means 50 has the same configuration as the first round-trip optical path separation means 40 described above, and its polarization beam splitter 50A is polarized light that reflects S-polarized light and transmits P-polarized light. A quarter-wave plate 50C and 50D are provided on the upper and lower surfaces of the polarizing beam splitter 50A, respectively, and a reflective surface 50E is provided on the lower surface of the quarter-wave plate 50D. Is formed.

  As a result, the second reciprocating optical path separating means 50 transmits the reflected light beam of P-polarized light reflected by the Blu-ray disc 100A as it is and irradiates the photodetector 38 via the condenser lens 37 as shown in FIG. To do.

  The photodetector 38 generates various detection signals such as a reproduction signal and an error signal in accordance with the amount of the reflected light beam from the Blu-ray disc 100A, and outputs the detection signal to the signal processing unit 23 (FIG. 4) of the optical disc device 20.

  On the other hand, when recording or reproducing on the HD-DVD 100B, the control unit 21 (FIG. 4) of the optical disc apparatus 20 sends the light transmitted through the polarization control unit 33 to the polarization control unit 33 so as to be P-polarized light. Control the applied voltage. Thereby, the light beam emitted from the polarization controller 33 enters the first reciprocating optical path separating means 40 in the state of P-polarized light.

  As described above, the polarization reflection surface 40B of the first reciprocating optical path separating means 40 has optical characteristics determined so as to reflect S-polarized light and transmit P-polarized light. As shown, the first reciprocating optical path separating means 40 transmits the light beam made of P-polarized light as it is and enters the half-wave plate 35. The half-wave plate 35 converts the light beam from the first round-trip optical path separating unit 40 from P-polarized light to S-polarized light and enters the second round-trip optical path separating unit 50.

  Further, the polarization reflection surface 50B of the polarization beam splitter 50A included in the second reciprocating optical path separation means 50 has optical characteristics determined so as to reflect S-polarized light and transmit P-polarized light. The splitter 50A reflects the light beam of S-polarized light by 90 °, rises upward, and enters the quarter-wave plate 50C provided on the upper surface thereof. The quarter-wave plate 50C converts the light beam from the polarization beam splitter 50A from S-polarized light to circularly-polarized light and enters the objective lens 51 for HD-DVD.

  The objective lens 51 has a focal length and a numerical aperture suitable for HD-DVD, and focuses the incident light beam to focus on the recording surface of the HD-DVD 100B and is reflected by the recording surface. The reflected light beam is received and reincident on the quarter-wave plate 50C.

  The quarter-wave plate 50C converts the reflected light beam from circularly polarized light into P-polarized light orthogonal to the forward path, and enters the polarizing beam splitter 50A. The polarization reflection surface 50B of the polarization beam splitter 50A transmits the reflected light beam made of P-polarized light and makes it incident on a quarter-wave plate 50D provided on the lower surface of the polarization beam splitter 50A.

  As described above, since the reflection surface 50E is formed on the bottom surface of the quarter-wave plate 50D, the reflected light beam composed of P-polarized light from the HD-DVD 100B incident on the quarter-wave plate 50D is It is converted into S-polarized light and reenters the polarizing beam splitter 50A.

  Then, the polarization reflection surface 50B of the polarization beam splitter 50A reflects the reflected light beam made of S-polarized light and irradiates the photodetector 38 via the condenser lens 37 as shown in FIG.

  The photodetector 38 generates various detection signals such as a reproduction signal and an error signal in accordance with the amount of the reflected light beam from the HD-DVD 100B, and outputs the detection signal to the signal processing unit 23 (FIG. 4) of the optical disc device 20.

  Thus, the optical pickup 26 controls the polarization direction of the light beam in accordance with the type of the optical disk 100 to be used. When the mounted optical disk 100 is a Blu-ray disc, the optical pickup 26 converts the light beam into the first reciprocating optical path separating unit. When the optical disc 100 mounted is an HD-DVD, the light beam is launched by the second reciprocating optical path separation unit 40 and passed through the objective lens 51. Irradiate.

  Here, as can be seen from FIG. 5, the optical pickup 26 introduces a light beam to the two objective lenses 41 and 51 from the same direction as the arrangement direction of the objective lenses 41 and 51 and has the same introduction direction. The reflected light beam is extracted from the opposite side of the line.

  Therefore, in the optical pickup 26, the two objective lenses 41 and 51 can be tangentially incident on the objective lenses 41 and 51 after the tangential arrangement shown in FIG.

(3) Operation and Effect In the above-described configuration, in the optical pickup 26, the first reciprocating optical path separating unit 40 and the second reciprocating optical path separating unit that raise the light beam and enter the corresponding objective lenses 41 and 51, respectively. 50 are arranged in series so that the polarization reflecting surfaces 40B and 50B face the laser diode 31 serving as the light source of the light beam.

  A polarization control unit 33 for controlling the polarization direction of the light beam is provided between the laser diode 31 serving as the light source of the light beam and the first round-trip optical path separation unit 40 at the first stage, and the first round-trip optical path. A half-wave plate 35 for changing S-polarized light into P-polarized light and changing P-polarized light into S-polarized light was provided between the separating unit 40 and the second round-trip optical path separating unit 50 in the next stage.

  As a result, the light beam converted to S-polarized light by the polarization control unit 33 is launched by the first reciprocating optical path separation unit 40 and guided to the objective lens 41 for the Blu-ray disc. The polarized light beam passes through the first round-trip optical path separation unit 40 and is then converted into S-polarized light by the half-wave plate 35 and is launched by the second round-trip optical path separation unit 50 to be used for HD-DVD. Guided to the objective lens 51.

  In addition to this, in the polarizing beam splitter 40A of the first reciprocating optical path separator 40, on the side opposite to the rising direction of the light beam, that is, on the exit surface side of the reflected light beam from the Blu-ray disc 100A, And a reflecting surface 40E that reflects the reflected light beam that has passed through the quarter-wave plate 40D, passes through the quarter-wave plate 40D, and reenters the polarization beam splitter 40A.

  As a result, the reflected light beam reflected by the Blu-ray disc 100A and converted into P-polarized light is transmitted through the polarization reflection film 40B of the polarization beam splitter 40A based on the polarization direction, and then reflected by the quarter wavelength plate 40D. By being reflected by 40E and re-passing through the quarter-wave plate 40D, it becomes P-polarized light orthogonal to the forward path and re-enters the polarization reflection film 40B of the polarization beam splitter 40A.

  The polarized reflection film 40B reflects the re-incident reflected light beam based on the polarization direction, and enters the second round-trip optical path separation unit 50 through the half-wave plate 35.

  At this time, since the reflected light beam from the Blu-ray disc 100A is changed from P-polarized light to S-polarized light by the half-wave plate 35, it passes through the second reciprocating optical path separating unit 50 as it is and passes through the condenser lens 37. Then, the light enters the photodetector 38.

  Similarly to the first round-trip optical path separation unit 40, the second round-trip optical path separation unit 50 also emits a reflected light beam from the opposite side of the light beam launch direction, that is, the HD-DVD 100B, in the polarization beam splitter 50A. A quarter-wave plate 50D is provided on the surface side, the reflected light beam that has passed through the quarter-wave plate 50D is reflected, passes through the quarter-wave plate 50D again, and reenters the polarizing beam splitter 50A. A reflecting surface 50E is provided.

  As a result, the reflected light beam reflected by the HD-DVD 100B and converted to P-polarized light is transmitted through the polarization reflection film 50B of the polarization beam splitter 50A based on the polarization direction, and after passing through the quarter-wave plate 50D, the reflection surface. By being reflected by 50E and re-passing through the quarter-wave plate 50D, it becomes P-polarized light orthogonal to the forward path, and re-enters the polarization reflection film 50B of the polarization beam splitter 50A.

  The polarized reflection film 50B reflects the re-incident reflected light beam based on the polarization direction, and enters the photodetector 38 through the condenser lens 37.

  As described above, the first round-trip optical path separation unit 40 and the second round-trip optical path separation unit 50 start up the light beams having the corresponding polarization directions toward the objective lenses 41 and 51, respectively, and reflect from the objective lenses. The light beam is emitted in the direction opposite to the incident direction of the light beam and is incident on the photodetector 38. Further, the light beam and the reflected light beam entering and exiting the other reciprocating optical path separating unit are transmitted as they are.

  As a result, the optical pickup 26 introduces the light beam from the same direction as the arrangement direction to the two objective lenses 41 and 51, and takes out the reflected light beam from the opposite side on the same line in the introduction direction. After the objective lenses 41 and 51 are arranged in a tangential arrangement perpendicular to the radial direction of the optical disk, a light beam can be tangentially incident on the objective lenses 41 and 51.

  Then, by arranging the objective lenses 41 and 51 in a tangential arrangement, the thread movement stroke of the optical pickup 26 can be made smaller than that in the radial arrangement, thereby loosening the size restriction in the radial direction of the optical pickup 26 and freeing it. Optical design is possible, and the height dimensions of the polarizing beam splitters 40A and 50A that also act as a rising mirror to the objective lenses 41 and 51 by tangentially entering the light beams with respect to the objective lenses 41 and 51. Can be set to the minimum dimension necessary for the reflection of the light beam without considering the lens shift amount of the objective lenses 41 and 51.

  According to the above configuration, the light beam from the laser diode 31 is reflected by the polarization reflection film 50A or 50B according to the polarization direction and is raised toward the optical disc 100, and the reflected light beam from the optical disc 100 is After passing through the polarization reflection film 50A or 50B according to the polarization direction, the polarization direction is changed and the polarization reflection film 50A or 50B is reincident and reflected to start up the light beam toward the optical disc 100. The rising mirror function and the reciprocating optical path separating function for emitting the reflected light beam from the side opposite to the incident direction of the light beam can be realized by the first reciprocating optical path separating unit 40 and the second reciprocating optical path separating unit 50. it can. The objective lenses 41 and 51 are arranged in a tangential manner, and a light beam is tangentially incident on the first reciprocating optical path separating unit 40 and the second reciprocating optical path separating unit 50 that operate as a rising mirror. The optical design of the optical pickup 26 can be increased and the dimensions thereof can be reduced, thus realizing an optical pickup and an optical disk drive corresponding to a plurality of types of optical disks using light beams of the same wavelength with a simple and small configuration. can do.

(4) Other Embodiments In the above-described embodiment, the light beam is guided from the first reciprocating optical path separation unit 40 in the front stage to the objective lens 41 for the Blu-ray disc, and the second reciprocating optical path separation in the rear stage. The light beam is guided from the unit 50 to the HD-DVD objective lens 51. However, the present invention is not limited to this, and the arrangement of the objective lens is reversed, and the first reciprocating optical path separation unit 40 in the previous stage is replaced with the HD. The light beam may be guided to the DVD objective lens and the light beam may be guided to the Blu-ray disc objective lens from the second reciprocating optical path separation unit 50 in the subsequent stage. Of course, in this case, when using a Blu-ray disc, the light beam exiting the polarization controller 33 is P-polarized light, and when using HD-DVD, the light beam exiting the polarization controller 33 is S-polarized light. Become.

  Further, in the above-described embodiment, the case where the liquid crystal optical element is used as the polarization control unit 33 that controls the polarization direction of the light beam according to the type of the optical disk has been described. Various other configurations of polarization control means, such as switching between two wave plates with different directions, can be used.

  In the above-described embodiment, the first round-trip optical path separation unit 40 and the second round-trip optical path separation unit 50 have the same configuration, and a ½ wavelength plate 35 is provided therebetween to change the polarization direction. Although one of the first round-trip optical path separation unit 40 or the second round-trip optical path separation unit 50 is operated, the present invention is not limited to this, and the polarizing reflection film 40B of the first round-trip optical path separation unit 40 is used. In addition, the half-wave plate 35 can be omitted by changing the optical characteristics of the polarization reflection film 50B of the second round-trip optical path separation unit 50.

  For example, the optical characteristics of the polarization reflection surface 40B of the first round-trip optical path separation unit 40 are determined so as to reflect S-polarization and P-polarization, and the polarization reflection surface 50B of the second round-trip optical path separation unit 50. If the optical characteristic is determined so as to reflect P-polarized light and transmit S-polarized light (or vice versa), even if the half-wave plate 35 is omitted, the optical path according to the type of the optical disk described above Separation can be performed.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to the optical disc apparatus 20 compatible with the Blu-ray Disc and the HD-DVD using the laser beam of the same wavelength has been described, but the present invention is not limited to this. In addition, the present invention is also applied to an optical disk apparatus corresponding to a plurality of types of optical disks using laser beams having various same wavelengths, and further to an optical disk apparatus corresponding to a plurality of types of optical disks using laser beams having different wavelengths. be able to.

  The present invention can be applied to an optical disc apparatus corresponding to a plurality of types of optical discs.

It is a basic diagram which shows the structure of the conventional optical pick-up. It is a basic diagram with which it uses for description of radial arrangement | positioning of an objective lens. It is a basic diagram with which it uses for description of the tangential arrangement | positioning of an objective lens. It is a block diagram which shows the whole structure of an optical disk device. It is a basic diagram which shows the structure of the optical pick-up by this invention. It is a basic diagram with which it uses for description of the optical path switching in an optical pick-up.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,26 ... Optical pick-up, 20 ... Optical disk apparatus, 21 ... Control part, 22 ... Drive part, 23 ... Signal processing part, 24 ... Spindle motor, 25 ... Thread motor, 27 ... 2-axis Actuator, 28 ... Objective lens unit, 31 ... Laser diode, 32 ... Collimator lens, 33 ... Polarization controller, 35 ... 1/2 wavelength plate, 37 ... Condensing lens, 38 ... Photo detector , 40... First round-trip optical path separation unit, 50... Second round-trip optical path separation unit, 41, 51... Objective lens, 100.

Claims (5)

A light source that emits a light beam;
A first objective lens corresponding to the first type of optical disc;
A second objective lens corresponding to the second type of optical disc;
Polarization direction control means for controlling the polarization direction of the light beam emitted from the light source according to the type of the mounted optical disk,
The light beam, the polarization direction of which is controlled by the polarization direction control means, is guided to the first objective lens based on the polarization direction, and the reflected light beam from the first type optical disk is the light. A first reciprocating optical path separating unit that emits in the direction opposite to the incident direction of the beam or transmits and emits the beam as it is;
The light beam that has passed through the first reciprocating optical path separating means is guided to the second objective lens based on the polarization direction thereof, and the reflected light beam from the second type of optical disk is guided to the light beam. A second light beam that is emitted in the direction opposite to the incident direction and is transmitted through the reflected light beam from the first type optical disk emitted from the first reciprocating optical path separating means as it is is emitted based on the polarization direction. An optical pickup comprising: a reciprocating optical path separating means. The first round-trip optical path separating means is
A first polarizing beam splitter that reflects or transmits the incident light beam in the direction of the first objective lens based on a polarization direction;
Provided between the first polarizing beam splitter and the first objective lens, the light beam is converted from linearly polarized light into circularly polarized light, and the reflected light beam from the first type optical disk is circularly polarized. A first quarter-wave plate for converting into linearly polarized light orthogonal to the light beam;
First reflecting means for reflecting the reflected light beam transmitted through the first polarizing beam splitter according to the polarization direction and re-entering the polarizing beam splitter;
Provided between the first polarizing beam splitter and the first reflecting means, and converts the reflected light beam from the first polarizing beam splitter from linearly polarized light to circularly polarized light, and the first reflected light. A second quarter-wave plate that converts the reflected light beam reflected by the means into linearly polarized light orthogonal to the forward path and reflects it by the first polarizing beam splitter;
The second round-trip optical path separating means is
A second polarization beam splitter that reflects the incident light beam in the direction of the second objective lens based on the polarization direction and transmits the reflected light beam from the first type optical disk based on the polarization direction. When,
Provided between the second polarizing beam splitter and the second objective lens, the light beam is converted from linearly polarized light into circularly polarized light, and the reflected light beam from the second type optical disk is circularly polarized. A third quarter-wave plate for converting into linearly polarized light orthogonal to the light beam;
Second reflection means for reflecting the reflected light beam transmitted through the second polarization beam splitter according to the polarization direction and re-entering the polarization beam splitter;
Provided between the second polarizing beam splitter and the second reflecting means, and converts the reflected light beam from the second polarizing beam splitter from linearly polarized light to circularly polarized light, and the second reflected light. 4. A fourth quarter-wave plate, wherein the reflected light beam reflected by the means is converted into linearly polarized light orthogonal to the forward path and reflected by the second polarizing beam splitter. The optical pickup according to 1. The first and second objective lenses are arranged in a tangential direction orthogonal to the radial direction of the optical disc,
The optical pickup according to claim 1, wherein the light beam from the light source is incident on the first reciprocating optical path separating unit from the tangential direction. Between the first and second reciprocating optical path separating means, a polarization direction converting means for converting the polarization direction of the light passing therethrough into a direction orthogonal to each other,
2. The optical pickup according to claim 1, wherein the first and second reciprocating optical path separating means both reflect light having the same polarization direction and transmit light having a polarization direction orthogonal thereto. A light source that emits a light beam;
A first objective lens corresponding to the first type of optical disc;
A second objective lens corresponding to the second type of optical disc;
Polarization direction control means for controlling the polarization direction of the light beam emitted from the light source according to the type of the mounted optical disk,
The light beam, the polarization direction of which is controlled by the polarization direction control means, is guided to the first objective lens based on the polarization direction, and the reflected light beam from the first type optical disk is the light. A first reciprocating optical path separating unit that emits in the direction opposite to the incident direction of the beam or transmits and emits the beam as it is;
The light beam that has passed through the first reciprocating optical path separating means is guided to the second objective lens based on the polarization direction thereof, and the reflected light beam from the second type of optical disk is guided to the light beam. A second light beam that is emitted in the direction opposite to the incident direction and is transmitted through the reflected light beam from the first type optical disk emitted from the first reciprocating optical path separating means as it is is emitted based on the polarization direction. An optical disc apparatus comprising: a reciprocating optical path separating means.

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