JP4389154B2 - Optical pickup and disk drive device - Google Patents

Description

  The present invention relates to an optical pickup and a disk drive device. More specifically, the present invention relates to a technical field in which at least part of a laser beam reflected by a layer different from a recording layer on which information is recorded or reproduced is not incident on a light receiving portion of a light receiving element, thereby preventing stray light from being generated.

  2. Description of the Related Art There is a disk drive device that records and reproduces information signals on and from a disk-shaped recording medium such as an optical disk and a magneto-optical disk. Such a disk drive apparatus moves in the radial direction of the disk-shaped recording medium and moves the disk An optical pickup for irradiating the recording medium with laser light is provided.

  In such an optical pickup, in general, laser light emitted from a light emitting element passes through a light separating element such as a beam splitter, and is condensed by an objective lens, and a spot of laser light is formed on a recording layer of a disk-shaped recording medium. It is formed. The laser beam condensed on the recording layer of the disk-shaped recording medium is reflected and incident again on the light separation element, and the optical path is converted by the light separation element and incident on the light receiving element.

  The disk-shaped recording medium includes a multi-layer type in which a plurality of recording layers are provided. The multi-layer disk-shaped recording medium includes, for example, a first recording layer (recording and reproducing information). Even when the laser beam is condensed on the layer to be formed to form a spot, the laser beam is reflected by another recording layer adjacent to the first recording layer.

  Therefore, there is a possibility that laser light reflected by another recording layer or the like enters the light receiving element as stray light.

  For example, as shown in FIGS. 54 and 55, laser light is focused on the recording layer L0 when recording or reproducing an information signal on a disk-shaped recording medium provided with two recording layers L1 and L0. In this case, the laser beam condensed on the recording layer L0 is collected and incident on the light receiving portions c, c, c of the light receiving element b by the condenser lens a, but is reflected by the recording layer L1 at this time. As shown in FIGS. 56 and 57, the laser beam thus made is incident on the light receiving element with a certain spread, and is incident on the light receiving portions c, c, and c as stray light. As shown in FIGS. 54 and 55, when the laser light is condensed on the recording layer L1, the laser light condensed on the recording layer L1 is received by the light receiving element b by the condenser lens a. At this time, the laser light reflected by the recording layer L0 has a certain spread in the light receiving element as shown in FIGS. 58 and 59. And enters the light receiving portions c, c, c as stray light.

  Such stray light causes, for example, problems such as RF (Radio Frequency) signal quality degradation and servo signal offset, and interference of laser light reflected by each layer of the disk-shaped recording medium or temperature change. It also causes a variation in device characteristics due to environmental changes such as.

  In particular, the interference between the main beam and the sub beam when the laser beam is separated is a big problem.

  For example, when the laser light emitted from the light emitting element is separated into 0th order light and ± 1st order light by a diffraction element or the like, the light intensity of the main light beam for detecting the RF signal is increased and the recording of the recording layer by the sub light beam is performed. In order to prevent the erasure of information, the light intensity of the sub-light beam is reduced to about 10% with respect to the light intensity of the main light beam. Therefore, the first recording is performed with respect to the light intensity of the laser beam of the main light beam reflected by the first recording layer (layer on which information is recorded and reproduced) on which the laser light is collected and received by the light receiving unit. If the light intensity of the main light beam reflected by the second recording layer adjacent to the layer and received by the light receiving unit is, for example, about 5%, it is reflected by the first recording layer and received by the light receiving unit. The light intensity of the laser light of the main light beam reflected by the second recording layer and received by the light receiving portion is about 50% with respect to the light intensity of the laser light of the sub light beam. This is a serious problem when performing tracking error detection, spherical aberration detection, land groove detection, and crosstalk detection.

  Therefore, the following countermeasures have been proposed for the above problems (see Patent Documents 1 to 3).

  In Patent Document 1, it has been proposed to increase the vertical magnification of the optical system and to reduce the area of the light receiving portion or the diameter of the pinhole.

  In Patent Document 2, the laser beam of the main beam reflected by the adjacent layer is not overlapped with the laser beam of the sub beam by sufficiently separating the sub beam from the main beam on the light receiving element. I have to.

  Patent Document 3 proposes a method of removing laser light from an adjacent recording layer by using a critical angle prism.

JP-A-8-185640

WO96 / 20473 JP 2002-367111 A

  However, as in Patent Document 1, when the vertical magnification is increased, a change in the spot diameter on the light receiving portion with respect to defocus increases, and there arises a problem that a servo margin for tracking error detection and the like becomes narrow. In addition, if the positional deviation of each optical component (optical element) with respect to the moving base occurs, the positional deviation of the spot on the light receiving section increases, making it difficult to adjust the position, and is also affected by subsequent changes over time and environmental changes. It becomes easy.

  Similarly, when the area of the light receiving portion is reduced or the diameter of the pinhole is reduced, it is difficult to adjust the position, and it is easy to be affected by subsequent changes over time and environmental changes. In particular, when laser light is separated into 0th order light and ± 1st order light, the difficulty of position adjustment further increases.

  When the sub-beam is sufficiently separated from the main beam as in Patent Document 2, the distance between the spot of the main beam and the spot of the sub-beam in the recording layer of the disc-shaped recording medium is also increased, resulting in the sub-beam. Asymmetry of generated light intensity and coma aberration increase. Therefore, for example, it becomes difficult to detect spherical aberration by the sub-beam, and the tracking error signal of the inner peripheral portion is caused by the difference in the curvature of the recording track between the outer peripheral portion and the inner peripheral portion of the disc-shaped recording medium. Deterioration may occur.

  When a critical angle prism is used as in Patent Document 3, if the laser light reflected by the recording layer for recording and reproducing information is parallel light, the adjacent recording layer becomes divergent light or convergent light. However, since the laser light in the vicinity of the main light flux from the adjacent recording layer cannot be removed, stray light cannot be sufficiently prevented.

  Accordingly, an object of the optical pickup and the disk drive device of the present invention is to overcome the above-described problems and to prevent stray light from entering the light receiving unit while ensuring the reliability of operation.

In order to solve the above-described problems, an optical pickup and a disk drive device according to the present invention provide a light emitting element that emits laser light toward a disk-shaped recording medium, and a laser beam emitted from the light-emitting element. An objective lens for condensing on the recording layer, a light receiving element having a light receiving portion for receiving the laser light reflected by the recording layer of the disk-shaped recording medium, a laser beam emitted from the light emitting element to the objective lens and a disk shape A light separating element for guiding the laser light reflected by the recording layer of the recording medium to the light receiving element, and a diffraction element having a diffraction part for diffracting the central part of the laser light in the optical path from the disk-shaped recording medium to the light receiving element. A light receiving portion of the light receiving element at least the central portion of the laser beam reflected by a layer different from the recording layer on which information is recorded or reproduced by the diffraction element Do not enter, the diffractive portion of the diffractive element is formed to extend to the recording track and tangential direction substantially parallel disc-shaped recording medium, divided into two light receiving portions of the photodetector in the radial direction, the diffractive portion of the diffractive element The laser light passing through the other part is divided into two with the diffraction part in between, the laser light is diffracted by the diffraction part of the diffractive element to generate ± 1st order light, and the diffraction part is sandwiched by one of the divided light receiving parts Receiving one laser beam and + 1st order light divided into two at, and receiving the other laser light and −1st order light split across the diffraction part by the other light receiving part divided and pushed. The tracking error is detected by the pull method .

  Therefore, in the optical pickup and the disk drive device of the present invention, the laser light reflected by another recording layer reaches a portion other than the light receiving portion of the light receiving element.

The optical pickup according to the present invention includes a moving base that is moved in the radial direction of a disk-shaped recording medium on which a plurality of recording layers to be mounted on a disk table is formed, and an objective lens driving device that is disposed on the moving base. A light-emitting element that emits laser light toward a disk-shaped recording medium, an objective lens that focuses the laser light emitted from the light-emitting element on a recording layer of the disk-shaped recording medium, and a disk-shaped recording medium A light receiving element having a light receiving portion for receiving the laser light reflected by the recording layer, and a light receiving element for guiding the laser light emitted from the light emitting element to the objective lens and reflecting the laser light reflected by the recording layer of the disk-shaped recording medium A diffractive element having a diffracting part for diffracting the central part of the laser beam in the optical path from the disc-shaped recording medium to the light receiving element Provided, at least the central portion of the laser beam reflected in a different layer from the recording layer where the recording or reproduction of information is performed by the diffraction element so as not to enter the light receiving portion of the light receiving element, a disk-shaped diffractive portion of the diffractive element It is formed so as to extend in a tangential direction substantially parallel to the recording track of the recording medium, the light receiving part of the light receiving element is divided into two in the radial direction, and the laser light passing through the part other than the diffractive part of the diffraction element is sandwiched between The laser beam is diffracted by the diffraction part of the diffractive element to generate ± 1st order light, and one of the laser light and the + 1st order light split by the split light receiving part with the diffraction part sandwiched therebetween And the other divided light receiving unit receives the other laser light divided into two with the diffraction part interposed therebetween and the −1st order light, and performs tracking error detection by a push-pull method. And said that there was Unishi.

  Accordingly, since the laser beam reflected by the layer on which information on the disk-shaped recording medium is not recorded or reproduced is not incident on the light receiving portion of the light receiving element, stray light is not generated, and the RF signal is deteriorated or the servo signal is offset. Does not occur. Further, the interference of the laser beam reflected by each layer of the disk-shaped recording medium does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  In addition, since there is no need to increase the vertical magnification of the optical system or reduce the area of the light receiving portion, the change in spot diameter with respect to defocus is small, and the shift in spot position due to the positional shift of each optical component is also small. It is easy to adjust the position, and is less susceptible to changes over time and environmental changes.

  Furthermore, it is possible to receive diffracted laser light by diffracting a part of the light beam including the chief ray of the laser light, and for detection methods that require more light intensity such as RF detection. Can be used.

  Furthermore, the laser beam reflected by the layer where information is not recorded or reproduced and diffracted by the diffraction part is incident on the light receiving part with a certain spread, but the light receiving part does not record or reproduce information. Since the diameter of the incident spot of the laser beam reflected by the recording layer and diffracted by the diffraction portion can be reduced, stray light can be reduced as a whole.

  In addition, by diffracting a part of the light beam including the principal light beam, it is possible to add other detection means such as focus error detection using ± first-order light.

In addition, since the diffraction element is easier to process than a prism, concerns such as scattering at the edge of the prism can be avoided. In addition, tracking error detection can be easily performed and detection accuracy of tracking error detection can be improved.

In the invention described in claim 2 , since only one spot of the laser beam is formed on the recording layer of the disk-shaped recording medium, the generation of stray light when the laser beam is used by so-called one beam is prevented. Can be prevented.

According to a third aspect of the present invention, there is provided a diffraction grating for separating the laser beam emitted from the light emitting element into a main light beam and a pair of sub light beams in an optical path from the light emitting element to the disk-shaped recording medium. Since the three spots of the laser beam composed of the main spot and the pair of sub-spots are formed on the recording layer of the recording medium, the sub-beam with respect to the laser beam when the laser beam is used by so-called three beams is formed. Generation of stray light of the main light beam can be prevented, and detection accuracy can be improved when performing tracking error detection, spherical aberration detection, land groove detection, and crosstalk detection using the sub light beam.

In the invention described in claim 4 , since the light receiving portion of the light receiving element is used to detect the wobble phase information formed on the recording track of the disk-shaped recording medium, the address signal is detected. Address signal detection can be easily performed, and detection accuracy of address signal detection can be improved.

The disc drive apparatus of the present invention is an optical pickup having a disc table on which a disc-shaped recording medium on which a plurality of recording layers are formed is mounted, and a moving base that is disposed in the radial direction of the disc-shaped recording medium. The optical pickup includes: a light emitting element that emits laser light toward the disk-shaped recording medium; and a laser beam emitted from the light emitting element on a recording layer of the disk-shaped recording medium. An objective lens for condensing, a light receiving element having a light receiving portion for receiving the laser light reflected by the recording layer of the disk-shaped recording medium, a laser beam emitted from the light emitting element to the objective lens, and a disk-shaped recording medium From a disk-shaped recording medium to a light receiving element, and a light separating element that guides the laser beam reflected by the recording layer to the light receiving element A diffractive element having a diffracting part that diffracts the central part of the laser light is provided in the optical path, and at least the central part of the laser light reflected by a layer different from the recording layer on which information is recorded or reproduced by the diffractive element is received. The diffractive portion of the diffractive element is formed so as to extend in a tangential direction substantially parallel to the recording track of the disk-shaped recording medium, the light receiving portion of the light receiving element is divided into two in the radial direction, Laser light passing through a part other than the diffraction part of the diffraction element is divided into two with the diffraction part interposed therebetween, and the laser light is diffracted by the diffraction part of the diffraction element to generate ± first order light, and one of the divided light receiving parts And receiving the one laser beam and the + 1st order light that are divided into two with the diffraction part interposed therebetween, and the other laser light and the −1st order light that are divided into two with the diffraction part being sandwiched by the other light receiving part that is divided. The It is characterized by receiving light and performing tracking error detection by a push-pull method .

  Accordingly, since the laser beam reflected by the layer on which information on the disk-shaped recording medium is not recorded or reproduced is not incident on the light receiving portion of the light receiving element, stray light is not generated, and the RF signal is deteriorated or the servo signal is offset. Does not occur. Further, the interference of the laser beam reflected by each layer of the disk-shaped recording medium does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  In addition, since there is no need to increase the vertical magnification of the optical system or reduce the area of the light receiving portion, the change in spot diameter with respect to defocus is small, and the shift in spot position due to the positional shift of each optical component is also small. It is easy to adjust the position, and is less susceptible to changes over time and environmental changes.

  Furthermore, it is possible to receive diffracted laser light by diffracting a part of the light beam including the chief ray of the laser light, and for detection methods that require more light intensity such as RF detection. Can be used.

  Furthermore, the laser beam reflected by the layer where information is not recorded or reproduced and diffracted by the diffraction part is incident on the light receiving part with a certain spread, but the light receiving part does not record or reproduce information. Since the diameter of the incident spot of the laser beam reflected by the recording layer and diffracted by the diffraction portion can be reduced, stray light can be reduced as a whole.

  In addition, by diffracting a part of the light beam including the principal light beam, it is possible to add other detection means such as focus error detection using ± first-order light.

In addition, since the diffraction element is easier to process than a prism, concerns such as scattering at the edge of the prism can be avoided. In addition, tracking error detection can be easily performed and detection accuracy of tracking error detection can be improved.

  The best mode of an optical pickup and a disk drive device according to the present invention will be described below with reference to the accompanying drawings.

  The disk drive device 1 is configured by arranging required members and mechanisms in an outer casing 2 (see FIG. 1), and the outer casing 2 has a disk insertion slot (not shown).

  A chassis (not shown) is disposed in the outer casing 2, and the disk table 3 is fixed to the motor shaft of a spindle motor attached to the chassis.

  Parallel guide shafts 4 and 4 are attached to the chassis, and a lead screw 5 that is rotated by a feed motor (not shown) is supported.

  The optical pickup 6 includes a moving base 7, required optical components provided on the moving base 7, and an objective lens driving device 8 disposed on the moving base 7, and is provided at both ends of the moving base 7. The bearing portions 7a and 7b are slidably supported by the guide shafts 4 and 4, respectively. When a nut member (not shown) provided on the moving base 7 is screwed into the lead screw 5 and the lead screw 5 is rotated by the feed motor, the nut member is sent in a direction corresponding to the rotation direction of the lead screw 5, The pickup 6 is moved in the radial direction of the disc-shaped recording medium 100 mounted on the disc table 3.

  As shown in FIG. 2, the disc-shaped recording medium 100 is a multilayer type, for example, a type having two recording layers L1 and L0, and in order from the incident side of the laser beam, a cover layer 100a, a recording layer L1, A recording layer L0 is formed. For example, the cover layer 100a has a thickness of 75 μm, and the interval between the recording layer L1 and the recording layer L0 is 25 μm.

  The disc-shaped recording medium 100 is not limited to the type having two recording layers, and may be a type having three or more recording layers. Below, two recording layers L1 and L0 are used. The case where the disc-shaped recording medium 100 having a recording layer is used will be described. Further, the thickness of the cover layer 100a and the interval between the recording layers L1 and L0 are not limited to the above values.

  Next, the optical pickup 6 will be described.

  First, the first best mode of the optical pickup will be described (see FIGS. 3 to 12).

  As shown in FIG. 3, the optical pickup 6A according to the first best mode includes a light emitting element 9, a collimator lens 10, a light separating element 11, an objective lens 12, a light blocking member 13, a condensing lens 14, and a light receiving element 15. The light emitting element 9, the collimator lens 10, the light separating element 11, the light shielding member 13, the condensing lens 14 and the light receiving element 15 are disposed on the moving base 7, and the objective lens 12 is provided on the objective lens driving device 8. Yes.

  As the light emitting element 9, for example, a semiconductor laser or a solid-state laser that emits laser light having a wavelength of about 405 nm is used. As the light separating element 11, for example, a beam splitter, prism (polarizing film prism, Wollaston prism, etc.) ), A diffraction element or the like is used, and a photodiode is used as the light receiving element 15, for example. Note that the wavelength of the laser light emitted from the light emitting element 9 is not limited to about 405 nm, and may be another wavelength such as about 650 nm or about 780 nm.

  For example, the collimator lens 10 has a numerical aperture NA of 0.15, the objective lens 12 has a numerical aperture NA of 0.85, and the condenser lens 14 has a numerical aperture NA of 0.08, for example. It is said that. The numerical aperture NA of the collimator lens 10, the objective lens 12, and the condenser lens 14 is not limited to these numerical values, and may be different from these numerical values.

  The light shielding member 13 is formed, for example, in a flat plate shape, and has, for example, a square light shielding portion 13a that shields laser light at the center (see FIG. 4). Accordingly, the portion other than the light shielding portion 13a of the light shielding member 13 is formed as a transmission portion 13b that transmits laser light. The light shielding portion 13a includes a part including the chief ray of the laser light reflected by the recording layer L0 and the recording layer L1 in the tangential direction along the recording track of the disc-shaped recording medium 100 and in the radial direction perpendicular to the recording track. It is formed to block. The light shielding part 13a is formed of, for example, an absorption film, a reflective film, a light shielding object, a reflection object, and the like.

  The shape of the light shielding member 13 is not limited to a flat plate shape. Further, the position of the light shielding member 13 is not limited between the light separating element 11 and the condensing lens 14, and can be provided integrally with the light separating element 11 or the condensing lens 14, for example. It is also possible to provide in the optical path between the optical lens 14 and the light receiving element 15.

  The light receiving element 15 is formed with a light receiving portion 15a formed in, for example, a square shape at the center thereof (see FIG. 6). Therefore, the part other than the light receiving part 15a of the light receiving element 15 is formed as a non-light receiving part 15b.

  In the optical pickup 6A, when laser light is emitted from the light emitting element 9, the emitted laser light is converted into a parallel light beam by the collimator lens 10, passes through the light separation element 11, and is condensed by the objective lens 12 to be disc. Spots are formed on the recording layer (recording layer L0 or recording layer L1) of the recording medium 100. The laser beam condensed on the recording layer of the disc-shaped recording medium 100 is reflected and incident again on the light separating element 11, the optical path is changed by the light separating element 11, and the light passes through the light shielding member 13 and the condensing lens 14. The light enters the light receiving element 15.

  At this time, for example, when the laser beam is focused on the recording layer L0, the laser beam focused on the recording layer L0 is shielded by the light shielding portion 13a as shown in FIGS. Except for the portion, the light is condensed and incident on the light receiving portion 15 a of the light receiving element 15 by the condensing lens 14.

  At the same time, the laser light reflected by the recording layer L1 is also directed to the light receiving element 15 via the light shielding member 13 and the condenser lens 14, but the laser light reflected by the recording layer L1 is as shown in FIGS. , A part is blocked by the light shielding part 13 a, and a part not blocked by the light shielding part 13 a is incident on the non-light receiving part 15 b of the light receiving element 15. Therefore, the laser beam reflected by the recording layer L1 is not incident on the light receiving portion 15a of the light receiving element 15.

  On the other hand, when the laser beam is focused on the recording layer L1, as shown in FIGS. 5 and 6, the laser beam focused on the recording layer L1 is excluded except for the portion shielded by the light shielding portion 13a. The light is condensed and incident on the light receiving portion 15 a of the light receiving element 15 by the condenser lens 14.

  At the same time, the laser light reflected by the recording layer L0 is also directed to the light receiving element 15 via the light shielding member 13 and the condenser lens 14, but the laser light reflected by the recording layer L0 is as shown in FIGS. , A part is blocked by the light shielding part 13 a, and a part not blocked by the light shielding part 13 a is incident on the non-light receiving part 15 b of the light receiving element 15. Therefore, the laser beam reflected by the recording layer L0 is not incident on the light receiving portion 15a of the light receiving element 15.

  11 and 12 show a modification of the light receiving unit.

  The light receiving unit 15 c shown in FIG. 11 is divided into two in the radial direction of the disc-shaped recording medium 100. Therefore, by using the light receiving unit 15c, for example, tracking error detection can be performed by a push-pull method. It is also possible to detect the address by detecting the phase information of the wobble formed on the recording track.

  The light receiving unit 15d shown in FIG. 12 is divided into two parts in each of the tangential direction and the radial direction of the disc-shaped recording medium 100, for example, and is divided into four parts in total. For example, tracking error detection is performed by the DPD method (phase difference detection method). Is possible. In addition, by arranging an optical element that generates astigmatism in the 45 ° direction with respect to the radial direction (the central axis direction of the disk-shaped recording medium 100) in the optical path of the laser light from the disk-shaped recording medium 100, It is also possible to detect focus error by the astigmatism method.

  As described above, in the optical pickup 6A, the laser beam reflected by the recording layer that does not record or reproduce information on the disc-shaped recording medium 100 is not incident on the light receiving portion 15a of the light receiving element 15. No stray light is generated, and no RF signal deterioration or servo signal offset occurs. Further, the interference of the laser light reflected by each layer of the disk-shaped recording medium 100 does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  Further, since there is no need to increase the vertical magnification of the optical system or to reduce the area of the light receiving portions 15a, 15c, and 15d, the change in spot diameter with respect to defocusing is small, and the spot accompanying the positional deviation of each optical component The positional deviation is small, the position adjustment is easy, and it is difficult to be affected by subsequent changes over time and environmental changes.

  Next, a second best mode of the optical pickup will be described (see FIGS. 13 to 23).

  The optical pickup 6B according to the second best mode described below differs from the optical pickup 6A described above only in that a prism is used instead of the light shielding member. In comparison, only different parts will be described in detail, and other parts will be denoted by the same reference numerals as those assigned to similar parts in the optical pickup 6A, and description thereof will be omitted.

  As shown in FIG. 13, the optical pickup 6B according to the second best mode includes a light emitting element 9, a collimator lens 10, a light separating element 11, an objective lens 12, a prism 16, a condensing lens 14, and a light receiving element 17. The prism 16 and the light receiving element 17 are disposed on the moving base 7.

  The prism 16 is formed, for example, in a substantially flat plate shape, and has, for example, a square-shaped refracting portion 16a that refracts laser light at the center (see FIG. 14). Therefore, the part other than the refraction part 16a of the prism 16 is formed as a transmission part 16b that transmits laser light. The refracting portion 16a is formed so as to spread in the tangential direction and radial direction of the disc-shaped recording medium 100.

  The shape of the prism 16 is not limited to a substantially flat plate shape. Further, the position of the prism 16 is not limited between the light separating element 11 and the condensing lens 14, and can be provided integrally with the light separating element 11 or the condensing lens 14, for example. It is also possible to provide in the optical path between the lens 14 and the light receiving element 17.

  In the light receiving element 17, for example, a first light receiving portion 17 a formed in a square shape is formed at the center, and a second light receiving portion 17 b is formed at a position separated from the first light receiving portion 17 a. (See FIG. 16). Accordingly, a portion other than the first light receiving portion 17a and the second light receiving portion 17b of the light receiving element 17 is formed as a non-light receiving portion 17c.

  In the optical pickup 6B, when laser light is emitted from the light emitting element 9, the emitted laser light is converted into a parallel light beam by the collimator lens 10, passes through the light separation element 11, and is collected by the objective lens 12 and collected. Spots are formed on the recording layer (recording layer L0 or recording layer L1) of the recording medium 100. The laser beam condensed on the recording layer of the disk-shaped recording medium 100 is reflected and incident again on the light separation element 11, and the light path is converted by the light separation element 11 and received through the prism 16 and the condenser lens 14. Incident on the element 17.

  At this time, for example, when the laser beam is focused on the recording layer L0, the laser beam focused on the recording layer L0 is refracted by the refracting portion 16a as shown in FIGS. Except for the portion, the light is condensed and incident on the first light receiving portion 17 a of the light receiving element 17 by the condensing lens 14. Of the laser light focused on the recording layer L 0, the portion refracted by the refracting portion 16 a is condensed by the condensing lens 14 and is incident on the second light receiving portion 17 b of the light receiving element 17.

  At the same time, the laser light reflected by the recording layer L1 is also directed to the light receiving element 17 through the prism 16 and the condenser lens 14, but the laser light reflected by the recording layer L1 is as shown in FIGS. A part of the light is refracted by the refracting part 16 a and a part that is not refracted by the refracting part 16 a is incident on the non-light receiving part 17 c of the light receiving element 17. Therefore, the laser beam reflected by the recording layer L1 is not incident on the first light receiving portion 17a of the light receiving element 17. Of the laser light reflected by the recording layer L1, the portion refracted by the refracting portion 16a is incident on the second light receiving portion 17b and the non-light receiving portion 17c of the light receiving element 17 with a certain spread.

  On the other hand, when the laser beam is focused on the recording layer L1, as shown in FIGS. 15 and 16, the laser beam focused on the recording layer L1 excludes the portion refracted by the refracting portion 16a. The light is condensed and incident on the first light receiving portion 17 a of the light receiving element 17 by the condenser lens 14. Of the laser light focused on the recording layer L 1, the portion refracted by the refracting portion 16 a is condensed by the condensing lens 14 and is incident on the second light receiving portion 17 b of the light receiving element 17.

  At the same time, the laser light reflected by the recording layer L0 is also directed to the light receiving element 17 through the prism 16 and the condenser lens 14, but the laser light reflected by the recording layer L0 is as shown in FIGS. A part of the light is refracted by the refracting part 16 a and a part that is not refracted by the refracting part 16 a is incident on the non-light receiving part 17 c of the light receiving element 17. Accordingly, the laser light reflected by the recording layer L0 is not incident on the first light receiving portion 17a of the light receiving element 17. Of the laser light reflected by the recording layer L0, the portion refracted by the refracting portion 16a is incident on the second light receiving portion 17b and the non-light receiving portion 17c of the light receiving element 17 with a certain spread.

  21 to 23 show modifications of the light receiving unit. Note that the second light receiving portion in FIGS. 21 to 23 receives the laser light reflected by the layer on which information is recorded or reproduced and the laser light reflected by another layer, but the information is recorded. Alternatively, the portion where the laser beam reflected by the layer being reproduced is received is shown in dark color.

  21 is divided into two in the radial direction of the disc-shaped recording medium 100. Therefore, tracking error detection can be performed by, for example, the push-pull method by using the first light receiving unit 17d. It is also possible to detect the address by detecting the phase information of the wobble formed on the recording track.

  The first light receiving portions 17f and 17h shown in FIG. 22 and FIG. 23 are divided into two parts in each of the tangential direction and the radial direction of the disc-shaped recording medium 100, for a total of four parts. For example, tracking error detection is performed by the DPD method. Is possible. In addition, an optical element that generates astigmatism in the direction of 45 ° with respect to the radial direction is disposed in the optical path of the laser beam from the disk-shaped recording medium 100, thereby performing focus error detection by the astigmatism method. Is also possible.

  Further, the first light receiving portion 17d and the second light receiving portion 17e shown in FIG. 21, the first light receiving portion 17f and the second light receiving portion 17g shown in FIG. 22, the first light receiving portion 17h shown in FIG. By using each of the two light receiving portions 17i, it is possible to perform RF detection requiring higher light intensity using the sum signal of each light receiving portion.

  The RF detection can also be performed by using the sum signal of the first light receiving unit 17a and the second light receiving unit 17b shown in FIGS.

  Furthermore, as shown in FIG. 23, when the second light receiving portion 17i divided into four in the tangential direction and the radial direction is formed, an optical element that generates astigmatism in a 45 ° direction with respect to the radial direction. It is also possible to detect spherical aberration from the difference in focus error signal by each astigmatism method.

  As described above, even in the optical pickup 6B, similarly to the optical pickup 6A, the laser light reflected by the recording layer that is not recording or reproducing information on the disc-shaped recording medium 100 is reflected by the first light receiving element 17. Since the light is not incident on the first light receiving portions 17a, 17d, 17f, and 17h, stray light is not generated, and the RF signal is not deteriorated and the servo signal is not offset. Further, the interference of the laser light reflected by each layer of the disk-shaped recording medium 100 does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  Further, since there is no need to increase the vertical magnification of the optical system or to reduce the area of each of the first light receiving portions 17a, 17d, 17f, and 17h, the change in spot diameter with respect to defocusing is small, and each optical component The positional deviation of the spot due to the positional deviation is small, the position adjustment is easy, and it is difficult to be affected by subsequent changes with time and environmental changes.

  Furthermore, it is possible to receive refracted laser light by refracting a part of the light beam including the chief ray of the laser light, and also for detection methods that require more light intensity such as RF detection. Can be used.

  In addition, the laser light reflected by the layer where information is not recorded or reproduced and refracted by the refracting portion 16a is incident on the second light receiving portions 17b, 17e, 17g, and 17i with a certain spread. However, the second light receiving portions 17b, 17e, 17g, and 17i can be made smaller in accordance with the diameter of the incident spot of the laser beam reflected by the recording layer where information is recorded and reproduced and refracted by the refracting portion 16a. Therefore, the stray light can be reduced as a whole.

  Next, a third best mode of the optical pickup will be described (see FIGS. 24 to 30).

  The optical pickup 6C according to the third best mode described below is different from the optical pickup 6A described above only in that a diffractive element is used in place of the light shielding member. Only different portions will be described in detail, and the other portions are denoted by the same reference numerals as the same portions in the optical pickup 6A, and description thereof will be omitted.

  The optical pickup 6C according to the third best mode includes a light emitting element 9, a collimator lens 10, a light separating element 11, an objective lens 12, a diffraction element 18, a condensing lens 14, and a light receiving element 19 as shown in FIG. The diffraction element 18 and the light receiving element 19 are arranged on the moving base 7.

  The diffractive element 18 is formed, for example, in a flat plate shape, and has, for example, a square diffractive portion 18a that diffracts laser light at the center (see FIG. 25). Therefore, the part other than the diffraction part 18a of the diffraction element 18 is formed as a transmission part 18b that transmits laser light. The diffractive portion 18 a is formed so as to spread in the tangential direction and radial direction of the disc-shaped recording medium 100.

  The shape of the diffraction element 18 is not limited to a flat plate shape. Further, the position of the diffractive element 18 is not limited to between the light separating element 11 and the condensing lens 14. For example, the diffraction element 18 can be provided integrally with the light separating element 11 or the condensing lens 14. It is also possible to provide in the optical path between the optical lens 14 and the light receiving element 19.

  The diffractive portion 18a may have a blazed shape that generates only + first-order light in addition to a step-shaped shape that generates ± first-order light. In the following, the case where the diffraction unit 18a that generates ± first-order light is used will be described.

  The light receiving element 19 has, for example, a first light receiving portion 19a formed in a square shape at the center, and the second light receiving portion is positioned opposite to the first light receiving portion 19a. 19b and 19b are formed (see FIG. 26). Therefore, portions other than the first light receiving portion 19a and the second light receiving portions 19b and 19b of the light receiving element 19 are formed as non-light receiving portions 19c.

  Note that the second light receiving unit in FIG. 26 receives the laser beam reflected by the layer on which information is recorded or reproduced and the laser beam reflected by another layer, but the information is recorded or reproduced. A portion where the laser beam reflected by the layer is received is shown in a dark color (the same applies to FIGS. 27, 29 and 30).

  In the optical pickup 6C, when laser light is emitted from the light emitting element 9, the emitted laser light is converted into a parallel light beam by the collimator lens 10, passes through the light separation element 11, and is condensed by the objective lens 12 to be disc. Spots are formed on the recording layer (recording layer L0 or recording layer L1) of the recording medium 100. The laser beam condensed on the recording layer of the disc-shaped recording medium 100 is reflected and incident again on the light separating element 11, the optical path is changed by the light separating element 11, and the light passes through the diffraction element 18 and the condenser lens 14. The light enters the light receiving element 19.

  At this time, for example, when the laser light is condensed on the recording layer L0, the portion of the laser light condensed on the recording layer L0 that has been transmitted through the transmission portion 18b is received by the light receiving element 19 by the condenser lens 14. The first light receiving portion 19a is condensed and incident (see FIG. 26). Of the laser light focused on the recording layer L0, the portion incident on the diffractive portion 18a is diffracted and generated as zero order light and ± first order light. The ± first-order light generated by diffracting is condensed by the condensing lens 14 and is incident on the second light receiving portions 19b and 19b of the light receiving element 19 (see FIG. 26). The 0th-order light generated by being diffracted is prevented from entering the first light receiving portion 19a and the second light receiving portions 19b and 19b of the light receiving element 19.

  At the same time, the laser light reflected by the recording layer L1 also travels toward the light receiving element 19 via the diffraction element 18 and the condenser lens 14, but the laser light reflected by the recording layer L1 is diffracted by the diffraction unit 18a, and the diffraction unit Only ± 1st order light diffracted by 18a is incident on the second light receiving portions 19b and 19b and the non-light receiving portion 19c of the light receiving element 19 with a certain spread (see FIG. 26).

  On the other hand, when the laser beam is condensed on the recording layer L1, the portion of the laser beam condensed on the recording layer L1 that has been transmitted through the transmission part 18b is the first of the light receiving element 19 by the condenser lens 14. The light is collected and incident on the light receiving portion 19a (see FIG. 26). Of the laser light focused on the recording layer L1, the portion incident on the diffractive portion 18a is diffracted and generated as 0th order light and ± 1st order light. The ± first-order light generated by diffracting is condensed by the condensing lens 14 and is incident on the second light receiving portions 19b and 19b of the light receiving element 19 (see FIG. 26). The 0th-order light generated by being diffracted is prevented from entering the first light receiving portion 19a and the second light receiving portions 19b and 19b of the light receiving element 19.

  At the same time, the laser light reflected by the recording layer L0 also travels toward the light receiving element 19 via the diffraction element 18 and the condenser lens 14, but the laser light reflected by the recording layer L0 is diffracted by the diffraction unit 18a, and the diffraction unit Only ± 1st order light diffracted by 18a is incident on the second light receiving portions 19b and 19b and the non-light receiving portion 19c of the light receiving element 19 with a certain spread (see FIG. 26).

  Even in the optical pickup 6C according to the third best mode, in the radial direction of the disc-shaped recording medium 100, like the first light receiving unit 17d (see FIG. 21) according to the second best mode. By dividing into two, for example, tracking error detection can be performed by a push-pull method. It is also possible to detect the address by detecting the phase information of the wobble formed on the recording track.

  FIG. 27 shows a modification of the light receiving unit.

  27 is divided into two parts in the tangential direction and the radial direction of the disc-shaped recording medium 100, for a total of four parts. Therefore, for example, tracking error detection can be performed by the DPD method. In addition, an optical element that generates astigmatism in the direction of 45 ° with respect to the radial direction is disposed in the optical path of the laser beam from the disk-shaped recording medium 100, thereby performing focus error detection by the astigmatism method. Is also possible.

  In addition, by using the first light receiving unit 19d and the second light receiving units 19e and 19e, it is possible to perform RF detection requiring higher light intensity using the sum signal of each light receiving unit.

  FIG. 28 shows a modification of the diffraction element.

  The diffractive element 18A according to the modified example is formed in a flat plate shape, for example, and has a diffractive portion 18c that is long in the tangential direction at the center in the radial direction. Accordingly, the part other than the diffraction part 18c of the diffraction element 18A is formed as a transmission part 18d that transmits laser light.

  The shape of the diffractive element 18A is not limited to a flat plate like the diffractive element 18. Further, the position of the diffractive element 18A is not limited between the light separating element 11 and the condensing lens 14. For example, the diffraction element 18A can be provided integrally with the light separating element 11 or the condensing lens 14. It is also possible to provide in the optical path between the optical lens 14 and the light receiving element 19.

  Similarly to the diffractive part 18a, the diffractive part 18c may have a blazed shape that generates only + 1st order light in addition to a step-like shape that generates ± first order light.

  29 and 30 show another modification of the light receiving unit. 29 and 30 is used in an optical system provided with the diffractive element 18A shown in FIG.

  29 is divided into two in the radial direction of the disc-shaped recording medium 100, and the second light receiving portions 19g and 19g are each divided into three in the tangential direction.

  Since the first light receiving portion 19f is divided into two in the radial direction, for example, tracking error detection can be performed by a push-pull method. It is also possible to detect the address by detecting the phase information of the wobble formed on the recording track.

  In the case of the first light receiving unit 19f, the zero-order light passing through the diffraction unit 18c of the diffractive element 18A is not incident on the first light receiving unit 19f, so the spot of the laser light incident on the first light receiving unit 19f is The shape is divided into two equal parts separated in the radial direction. Therefore, the signal detected by the push-pull method is calculated only with the laser beam that has passed through the transmitting portion 18d of the diffraction element 18A, and the phase shift is reduced by removing the signal in the vicinity of the principal ray, and the address Signal quality is improved.

  If the first light receiving portion 19f is also divided into two in the tangential direction, for example, tracking error detection can be performed by the DPD method.

  In addition, by using the first light receiving unit 19f and the second light receiving units 19g and 19g, it is possible to perform RF detection requiring higher light intensity using the sum signal of each light receiving unit.

  Further, since the second light receiving portions 19g and 19g are divided into three in the tangential direction, the diffractive element 18A has a lens effect to change the focusing position in the tangential direction of at least ± first-order light, respectively. By detecting the change of the spot size on the second light receiving portions 19g and 19g of ± primary light, respectively, it becomes possible to detect the focus error signal by the SSD method (spot size detection method).

  The light receiving portion 19h shown in FIG. 30 is divided into two in the radial direction of the disc-shaped recording medium 100, and is formed long in the radial direction.

  Since the light receiving portion 19h is divided into two in the radial direction, for example, tracking error detection can be performed by a push-pull method. It is also possible to detect the address by detecting the phase information of the wobble formed on the recording track.

  In the case of the light receiving part 19h, the zero-order light passing through the diffractive part 18c of the diffractive element 18A is not incident on the light receiving part 19h, so that the laser beam spot incident on the light receiving part 19h is separated into two equal parts in the radial direction. It becomes the shape made. Therefore, the signal detected by the push-pull method is calculated only with the laser beam that has passed through the transmitting portion 18d of the diffraction element 18A, and the phase shift is reduced by removing the signal in the vicinity of the principal ray, and the address Signal quality is improved.

  If the light receiving unit 19h is divided into two in the tangential direction, for example, tracking error detection can be performed by the DPD method.

  In addition, since one side half of the zero-order light and one primary light of the zero-order light are incident on the respective divided portions, the light receiving unit 19h requires higher light intensity using the sum signal of the light receiving unit 19h. It is also possible to perform RF detection.

  Furthermore, since all the laser beams can be detected by the light receiving unit 19h divided into two, the number of amplifiers that convert the current from the light receiving unit 19h into a voltage can be reduced, and amplifier noise can be reduced. Therefore, particularly when RF detection is performed, the quality of the RF signal can be improved.

  As described above, even in the optical pickup 6C, similarly to the optical pickup 6A, the laser light reflected by the recording layer that has not recorded or reproduced information on the disc-shaped recording medium 100 is reflected by the first light receiving element 19. Since the light is not incident on one light receiving portion 19a, 19d, or 19f, stray light is not generated, and the RF signal is not deteriorated and the servo signal is not offset. Further, the interference of the laser light reflected by each layer of the disk-shaped recording medium 100 does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  Further, since there is no need to increase the vertical magnification of the optical system or to reduce the area of each of the first light receiving portions 19a, 19d, and 19f, the change in spot diameter with respect to defocus is small, and the position of each optical component The deviation of the spot position due to the deviation is small, the position adjustment is easy, and it is difficult to be affected by subsequent changes with time and environmental changes.

  Furthermore, it is possible to receive diffracted laser light by diffracting a part of the light beam including the chief ray of the laser light, and for detection methods that require more light intensity such as RF detection. Can be used.

  Furthermore, the laser beam reflected by the layer where information is not recorded or reproduced and diffracted by the diffraction portions 18a and 18c has a certain spread in the second light receiving portions 19b, 19e and 19g or the light receiving portion 19h. The second light receiving portions 19b, 19e, 19g or the light receiving portion 19h are reflected by the recording layer where information is recorded or reproduced, and the diameter of the incident spot of the laser beam diffracted by the diffraction portions 18a, 18c. Therefore, it is possible to reduce stray light as a whole.

  In addition, by diffracting a part of the light beam including the principal light beam, it is possible to add other detection means such as focus error detection using ± first-order light.

  In addition, since the diffraction elements 18 and 18A are easier to process than the prism, concerns such as scattering at the edge portion of the prism can be avoided.

  In the above description, the case where the diffractive elements 18 and 18A having the diffractive portions 18a and 18c formed in a step-like shape for generating ± first-order light are used has been described. In the case of using a diffraction element having a portion, since the light is diffracted only into the 0th-order light and the + 1st-order light, the same effect as described in the second best mode is produced.

  In the above description, the diffractive element 18A (see FIG. 28) having the diffractive portion 18c long in the tangential direction has been described. However, the light shielding plate and the prism shown in the first and second best modes, respectively. In this case, the light shielding portion and the refracting portion may be formed long in the tangential direction.

  Next, a fourth best mode of the optical pickup will be described (see FIGS. 31 to 43).

  The optical pickup 6D according to the fourth best mode described below includes the optical pickup 6A according to the first best mode, the optical pickup 6B according to the second best mode, or the third best mode. Compared with the optical pickups 6A, 6B, and 6C, the optical pickup 6C according to the present invention is different from the optical pickups 6A, 6B, and 6C only in that a diffraction grating is provided and separated into three light beams of a main light beam (zero order light) and a sub light beam (± first order light) Only the different parts will be described in detail, and the other parts will be denoted by the same reference numerals as the same parts in the optical pickups 6A, 6B, 6C, and the description thereof will be omitted.

  As shown in FIG. 31, the optical pickup 6D according to the fourth best mode includes a light emitting element 9, a diffraction grating 20, a collimator lens 10, a light separating element 11, an objective lens 12, a condenser lens 14, and a light receiving element 21. For example, the light shielding member 13A, the light shielding member 13B, the prism 16A, or the diffraction element 18A described below is disposed between the light separating element 11 and the light receiving element 21, for example. The diffraction grating 20 and the light receiving element 21 are disposed on the moving base 7.

  The diffraction grating 20 is formed in a flat plate shape, for example, and diffracts the laser light emitted from the light emitting element 9 to separate it into 0th order light and ± 1st order light.

  For example, as shown in FIG. 32, the light shielding member 13A is formed in a flat plate shape, and has a light shielding portion 13c that is long in the tangential direction at the center in the radial direction. Therefore, the portion other than the light shielding portion 13c of the light shielding member 13A is formed as a transmission portion 13d that transmits laser light. Of the laser light of the main light beam and the sub light beam, a part of the laser light including the main light beam is shielded by the light shielding part 13c of the light shielding member 13A.

  For example, as shown in FIG. 33, the light shielding member 13B is formed in a flat plate shape, and has substantially circular light shielding portions 13e and 13e separated from each other in the tangential direction at the center. Therefore, the portions other than the light shielding portions 13e and 13e of the light shielding member 13B are formed as transmission portions 13f that transmit laser light. The light shielding portions 13e and 13e of the light shielding member 13B shield a part of the sub-beam including the principal ray of the laser light.

  For example, as shown in FIG. 34, the prism 16A is formed in a flat plate shape, and has a refracting portion 16c that is long in the tangential direction at the center in the radial direction. Therefore, the part other than the refraction part 16c of the prism 16A is formed as a transmission part 16d that transmits laser light.

  The light receiving element 21 receives the 0th order light and the ± 1st order light, respectively, so that the main side light receiving part 21a located at the center and the sub side light receiving part located adjacent to the opposite side across the main side light receiving part 21a 21b, 21b. Accordingly, the portion of the light receiving element 21 excluding the main side light receiving portion 21a and the sub side light receiving portions 21b and 21b is formed as a non-light receiving portion 21c.

  In the optical pickup 6D, for example, when the light shielding member 13A is used, when the laser light is emitted from the light emitting element 9, the emitted laser light is separated into zero order light and ± first order light by the diffraction grating 20. The collimator lens 10 converts the light into a parallel light beam, passes through the light separation element 11, and is collected by the objective lens 12 to form three spots on the recording layer (recording layer L 0 or recording layer L 1) of the disc-shaped recording medium 100. The The laser beam condensed on the recording layer of the disk-shaped recording medium 100 is reflected and incident again on the light separation element 11, the optical path is changed by the light separation element 11, and the light is passed through the light shielding member 13 A and the condenser lens 14. The light enters the light receiving element 21.

  At this time, for example, when the laser light is condensed on the recording layer L0, the laser light condensed on the recording layer L0 is received by the condensing lens 14 except for a portion shielded by the light shielding portion 13c. The light is condensed and incident on the main light receiving part 21a and the sub light receiving parts 21b and 21b of the element 21 in a state of being divided in the radial direction (see FIG. 35).

  At the same time, the laser light reflected by the recording layer L1 also travels toward the light receiving element 21 via the light shielding member 13A and the condensing lens 14, but part of the laser light reflected by the recording layer L1 is shielded by the light shielding portion 13c. The portion not blocked by the light blocking portion 13c is incident on the non-light receiving portion 21c of the light receiving element 21 in a state of having a certain spread and being divided in the radial direction (see FIG. 36). Accordingly, the laser light reflected by the recording layer L1 is not incident on the main-side light-receiving portion 21a and the sub-side light-receiving portions 21b and 21b of the light-receiving element 21.

  On the other hand, when the laser beam is condensed on the recording layer L1, the laser beam condensed on the recording layer L1 is not reflected by the condensing lens 14 except for the portion shielded by the light shielding portion 13c. The light is condensed and incident on the main light receiving unit 21a and the sub light receiving units 21 and 21b in a state of being divided in the radial direction (see FIG. 35).

  At the same time, the laser light reflected by the recording layer L0 also travels toward the light receiving element 21 via the light shielding member 13A and the condensing lens 14, but part of the laser light reflected by the recording layer L0 is shielded by the light shielding portion 13c. The portion not blocked by the light blocking portion 13c is incident on the non-light receiving portion 21c of the light receiving element 21 in a state of having a certain spread and being divided in the radial direction (see FIG. 37). Accordingly, the laser light reflected by the recording layer L0 is not incident on the main-side light receiving portion 21a and the sub-side light receiving portions 21b and 21b of the light receiving element 21.

  FIG. 38 shows a modification of the light receiving unit when the light shielding member 13A is used.

  The main-side light receiving unit 21d and the sub-side light receiving units 21e and 21e shown in FIG. 38 are each divided into two in the radial direction. For example, tracking error detection can be performed by the DPP method (differential push-pull method). is there. Further, by using the main light receiving portion 21d, it is possible to detect the address information by detecting the phase information of the wobble formed on the recording track.

  FIG. 39 shows another modification of the light receiving unit when the light shielding member 13A is used.

  The main side light receiving unit 21f and the sub side light receiving units 21g and 21g shown in FIG. 39 are divided into two parts in the tangential direction and the radial direction, for a total of four parts. For example, by using the main side light receiving unit 21f, the DPD The tracking error can be detected by the method. In addition, an optical element that generates astigmatism in the direction of 45 ° with respect to the radial direction is arranged in the optical path of the laser light from the disk-shaped recording medium 100, and astigmatism is obtained by using the main-side light receiving unit 21f. It is also possible to detect the focus error by the method. Furthermore, spherical aberration detection, land groove detection, and crosstalk detection can be performed by using the sub-side light receiving portions 21g and 21g.

  FIG. 40 shows an example of the light receiving unit when the prism 16A is used. Note that the second light receiving unit in FIG. 40 receives the laser light reflected by the layer where information is recorded or reproduced and the laser light reflected by another layer, but the information is recorded or reproduced. The portion where the laser beam reflected by the layer is received is shown in dark color (the same applies to FIGS. 41 to 43).

  The first light receiving unit 22 shown in FIG. 40 includes a main side light receiving unit 22a and sub side light receiving units 22b and 22b. The main side light receiving unit 22a and the sub side light receiving units 22b and 22b have a tangential direction and a radial direction, respectively. Divided into two in the direction, a total of four.

  The second light receiving unit 23 shown in FIG. 40 is composed of a main side light receiving unit 23a and sub side light receiving units 23b and 23b.

  For example, it is possible to detect tracking errors by the DPD method by using the main light receiving unit 22a. In addition, an optical element that generates astigmatism in the direction of 45 ° with respect to the radial direction is arranged in the optical path of the laser light from the disc-shaped recording medium 100, and astigmatism is obtained by using the main-side light receiving unit 22a. It is also possible to detect a focus error by the method. Furthermore, spherical aberration detection, land groove detection, and crosstalk detection can be performed by using the sub-side light receiving units 22b and 22b.

  In addition, by using the first light receiving unit 22 and the second light receiving unit 23, RF detection that requires higher light intensity using the sum signal of the first light receiving unit 22 and the second light receiving unit 23. It is also possible to perform.

  FIG. 41 shows an example of the light receiving unit when the diffraction element 18A is used.

  The first light receiving unit 24 shown in FIG. 41 includes a main side light receiving unit 24a and sub side light receiving units 24b and 24b. The main side light receiving unit 24a and the sub side light receiving units 24b and 24b are each divided into two in the radial direction. Has been.

  41 is composed of main-side light-receiving portions 25a and 25a and two sub-side light-receiving portions 25b, 25b,.

  For example, tracking error detection can be performed by the DPP method. Further, by using the main light receiving unit 24a, it is possible to detect the address information by detecting the phase information of the wobble formed on the recording track.

  Further, by using the first light receiving unit 24 and the second light receiving units 25 and 25, higher light intensity is required by using the sum signal of the first light receiving unit 24 and the second light receiving units 25 and 25. It is also possible to perform RF detection.

  FIG. 42 shows a modification of the light receiving unit when the diffraction element 18A is used.

  The first light receiving unit 26 shown in FIG. 42 includes a main side light receiving unit 26a and sub side light receiving units 26b and 26b. The main side light receiving unit 26a and the sub side light receiving units 26b and 26b are each divided into two in the radial direction. Has been.

  The second light receiving portions 27 and 27 shown in FIG. 42 are configured only by the main side light receiving portions 27a and 27a, respectively.

  For example, tracking error detection can be performed by the DPP method. In addition, by using the main-side light receiving unit 26a, it is possible to detect the address information by detecting the phase information of the wobble formed on the recording track.

  Further, by using the first light receiving unit 26 and the second light receiving units 27 and 27, higher light intensity is required by using the sum signal of the first light receiving unit 26 and the second light receiving units 27 and 27. It is also possible to perform RF detection.

  FIG. 43 shows another modification of the light receiving unit when the diffraction element 18A is used.

  The light receiving unit 28 shown in FIG. 43 includes a main side light receiving unit 28a and sub side light receiving units 28b and 28b. The main side light receiving unit 28a and the sub side light receiving units 28b and 28b are each divided into two in the radial direction. . The main side light receiving portion 28a is formed longer in the radial direction than the sub side light receiving portions 28b and 28b.

  For example, tracking error detection can be performed by the DPP method. Further, by using the main light receiving unit 28a, it is also possible to detect the address information by detecting the phase information of the wobble formed on the recording track.

  In addition, since one half of the zero-order light and one primary light are incident on the divided portions of the main-side light-receiving portion 28a of the light-receiving portion 28, the sum signal of the main-side light-receiving portion 28a is used. It is also possible to perform RF detection that requires higher light intensity.

  Furthermore, since all of the zero-order light can be detected by the main light receiving unit 28a divided into two, the number of amplifiers that convert the current from the main light receiving unit 28a into voltage can be reduced, and amplifier noise can be reduced. Can be planned. Therefore, particularly when RF detection is performed, the quality of the RF signal can be improved.

  42 and 43, the first light receiving unit 26, the second light receiving unit 27, and the light receiving unit 28 detect all the main light beams, and the sub light beams are transmitted through the transmission unit 16d of the prism 16A or diffracted. Only the portion of the element 18A that has passed through the transmission portion 18d can be detected. Accordingly, stray light is generated between the main light beams in a range where the interference is negligible, but between the sub-light beam that has passed through the transmissive portion 16d or the transmissive portion 18d where interference is not negligible and the main light beam that has passed through the prism portion 16c or the diffractive portion 18c. No stray light is generated.

  As described above, even in the optical pickup 6D, similarly to the optical pickup 6A, the laser light reflected by the recording layer that does not record or reproduce information on the disk-shaped recording medium 100 is reflected on the main light receiving unit 21a. , 21d, 21f, sub-side light receiving portions 21b, 21b, 21e, 21e, 21g, 21g, and the first light receiving portions 22, 24, 26, no stray light is generated, RF signal deterioration and servo signal deterioration There is no offset. Further, the interference of the laser light reflected by each layer of the disk-shaped recording medium 100 does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  In addition, since there is no need to increase the vertical magnification of the optical system or to reduce the area of each light receiving section, the change in spot diameter with respect to defocusing is small, and the spot position shift due to the position shift of each optical component It is small and easy to adjust the position, and is less susceptible to subsequent changes with time and environmental changes.

  Further, when the laser light is diffracted and separated into zero-order light and ± first-order light, the stray light of the main light beam is reduced or prevented from entering the sub-side light receiving unit that receives the sub-light beam having a low light intensity. Therefore, it is possible to improve the reliability of tracking error detection, spherical aberration detection, land groove detection, and crosstalk detection using sub-beams.

  Next, a fifth best mode of the optical pickup will be described (see FIGS. 44 to 52).

  The optical pickup 6E according to the fifth best mode described below includes the optical pickup 6A according to the first best mode, the optical pickup 6B according to the second best mode, and the third best mode. The optical pickup 6C according to the fourth embodiment or the optical pickup 6D according to the fourth best mode is different from the optical pickup 6A, 6B, 6C, 6D in that only a part of the laser beam is shielded by providing a pinhole or slit. Only different parts will be described in detail, and the other parts will be denoted by the same reference numerals as the same parts in the optical pickups 6A, 6B, 6C, 6D, and the description thereof will be omitted.

  As shown in FIG. 44, the optical pickup 6E according to the fifth best mode includes a light emitting element 9, a collimator lens 10, a light separating element 11, an objective lens 12, a condenser lens 14, and a light receiving element 15, for example. Between the light separation element 11 and the light receiving element 15, for example, any one of the light shielding members 13, 13A, 13B, the prisms 16, 16A, or the diffraction elements 18, 18A is disposed. Further, the diffraction grating 20 may be provided, and the light receiving element is not limited to the light receiving element 15, and any of the light receiving elements described in the first to fourth best modes ( Light receiving part).

  A light control member 29 is disposed on the light receiving element 15 (see FIG. 45). The light control member 29 is formed in, for example, a block shape, and a light shielding portion 29a is formed on the upper surface thereof. The light shielding part 29a is formed of, for example, an absorption film, a reflection film, a light shielding object, a reflection object, and the like. In the central portion of the upper surface of the light control member 29, a part of the light shielding part 29a is not formed, and this part is formed as a pinhole 29b. Portions other than the light shielding portion 29a and the pinhole 29b of the light control member 29 are formed as a transmission portion 29c.

  Hereinafter, a case where the light shielding member 13 is disposed between the light separation element 11 and the condenser lens 14 will be described as an example.

  In the optical pickup 6E, when laser light is emitted from the light emitting element 9, the emitted laser light is converted into a parallel light beam by the collimator lens 10, passes through the light separation element 11, and is condensed by the objective lens 12 to be disc. Spots are formed on the recording layer (recording layer L0 or recording layer L1) of the recording medium 100. The laser beam condensed on the recording layer of the disc-shaped recording medium 100 is reflected and incident again on the light separating element 11, the optical path is changed by the light separating element 11, and the light passes through the light shielding member 13 and the condensing lens 14. The light enters the light receiving element 15. When the diffraction grating 20 is provided, the diffraction grating 20 separates the laser light into 0th order light and ± 1st order light.

  At this time, for example, when the laser light is condensed on the recording layer L0, the laser light condensed on the recording layer L0 is received by the condensing lens 14 except for the portion shielded by the light shielding portion 13a. The light is condensed and incident on the light receiving portion 15a of the element 15 (see FIG. 46). The laser light traveling toward the light receiving element 15 passes through the pinhole 29b of the light control member 29 and enters the light receiving portion 15a to be received.

  At the same time, the laser light reflected by the recording layer L1 also travels toward the light receiving element 15 via the light shielding member 13 and the condensing lens 14, but part of the laser light reflected by the recording layer L1 is blocked by the light shielding portion 13a. The portion that is not blocked by the light blocking portion 13 a goes to the light receiving element 15. The portion that is not blocked by the laser light blocking portion 13a is directed to the light receiving element 15, but is blocked by the light blocking portion 29a of the light control member 29 and is not incident on the light receiving element 15 (see FIG. 47). Therefore, the laser beam reflected by the recording layer L1 is not incident on the light receiving element 15.

  On the other hand, in the case where the laser light is condensed on the recording layer L1, the laser light condensed on the recording layer L1 is removed from the light receiving element 15 by the condensing lens 14 except for the portion shielded by the light shielding portion 13a. The light is collected and incident on the light receiving portion 15a (see FIG. 46). The laser light traveling toward the light receiving element 15 passes through the pinhole 29b of the light control member 29 and enters the light receiving portion 15a to be received.

  At the same time, the laser light reflected by the recording layer L0 also travels toward the light receiving element 15 via the light shielding member 13 and the condenser lens 14, but part of the laser light reflected by the recording layer L0 is blocked by the light shielding portion 13a. The portion that is not blocked by the light blocking portion 13 a goes to the light receiving element 15. The portion that is not blocked by the laser light blocking portion 13a goes to the light receiving element 15, but is blocked by the light blocking portion 29a of the light control member 29 and is not incident on the light receiving element 15 (see FIG. 48). Therefore, the laser beam reflected by the recording layer L0 is not incident on the light receiving element 15.

  49 to 51 show an example in which a prism or a diffractive element is arranged instead of the light shielding member arranged between the light separating element 11 and the condensing lens 14. 49 to 51 show, as an example, a light receiving element 17 having a first light receiving portion 17a and a second light receiving portion 17b.

  When the laser beam is focused on the recording layer L0 or the recording layer L1, the portion of the laser beam focused on the recording layer L0 or the recording layer L1 that has not been refracted or diffracted is the pin of the light control member 29. The light passes through the hole 29b and enters the first light receiving portion 17a to be received (see FIG. 49). The refracted or diffracted portion of the laser light is transmitted through the transmission portion 29c of the light control member 29 and incident on the second light receiving portion 17b to be received.

  At this time, when the laser beam is focused on the recording layer L 0, the laser beam reflected by the recording layer L 1 is blocked by the light blocking portion 29 a except the refracted or diffracted portion and is incident on the light receiving element 17. First, the refracted or diffracted portion of the laser light is transmitted through the transmission portion 29c of the light control member 29 and is incident on the second light receiving portion 17b (see FIG. 50).

  On the other hand, when the laser light is focused on the recording layer L1, the laser light reflected by the recording layer L0 is shielded by the light shielding portion 29a except the refracted or diffracted portion and is not incident on the light receiving element 17. The refracted or diffracted portion of the laser light is transmitted through the transmitting portion 29c of the light control member 29 and is incident on the second light receiving portion 17b (see FIG. 51).

  FIG. 52 shows a modification of the light control member.

  The light control member 29 </ b> A according to the modified example is formed in a block shape, for example, and is disposed on the light receiving element 21. Light shielding portions 29d and 29d are formed on the upper surface of the light shielding member 29A so as to be spaced apart from each other in the radial direction. The light shielding portions 29d and 29d are formed of, for example, an absorption film, a reflection film, a light shielding object, a reflection object, and the like. A portion between the light shielding portions 29d and 29d on the upper surface of the light control member 29A is formed as a slit 29e extending in the tangential direction. The portions other than the light shielding portions 29d and 29d and the slit 29e of the light control member 29 are formed as a transmission portion 29f.

  In the optical pickup 6E, the light control member 29A may be used in place of the light control member 29. When the laser light is separated into 0th order light and ± 1st order light, the light control member 29A is used. It is desirable.

  The light shielding portions 29a, 29d, and 29d of the light control member 29 and the light control member 29A are not limited to the absorption film, the reflection film, the light shielding object, and the reflection object, and have, for example, a function of refracting or diffracting laser light. It may be a prism part or a diffraction part. Further, the light control member 29 and the light control member 29A do not necessarily have to be disposed on the light receiving elements 15, 17, 21, etc., for example, a holding part for holding the light receiving elements 15, 17, 21, etc. It may be held or fixed to.

  As described above, even in the optical pickup 6E, similarly to the optical pickup 6A, the laser light reflected by the recording layer not recording or reproducing information on the disc-shaped recording medium 100 is received by the light receiving elements 15 and 17. , 21 are not incident on the light receiving portion 15a, the first light receiving portion 17a, and the main light receiving portion 21a, so that no stray light is generated and no RF signal deterioration or servo signal offset occurs. Further, the interference of the laser light reflected by each layer of the disk-shaped recording medium 100 does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  In addition, since there is no need to increase the vertical magnification of the optical system or to reduce the area of each light receiving section, the change in spot diameter with respect to defocusing is small, and the spot position shift due to the position shift of each optical component It is small and easy to adjust the position, and is less susceptible to subsequent changes with time and environmental changes.

  Further, since the laser light reflected by the recording layer on which information on the disk-shaped recording medium 100 is not recorded or reproduced does not reach the light receiving elements 15, 17, and 21 except for the refracted or diffracted portion, stray light is reliably generated. Can be prevented.

  Next, a sixth best mode of the optical pickup will be described (see FIG. 53).

  The optical pickup 6F according to the sixth best mode described below includes the optical pickup 6A according to the first best mode, the optical pickup 6B according to the second best mode, and the third best mode. The optical pickup 6C according to the fourth embodiment, the optical pickup 6D according to the fourth best mode, or the optical pickup 6E according to the fifth best mode are applied to the integrated optical element.

  The optical pickup 6F according to the sixth best mode is formed by arranging required parts in a resin package 30.

  The package 30 is formed, for example, in a flat and substantially rectangular tube shape that opens upward and downward, and a lead frame 31 is embedded in the package 30. The lower opening of the package 30 is closed by a flat lid 32.

  The light emitting element 9 is mounted on the lower surface side of the lead frame 31 via a mount portion 33 called a submount. As the light emitting element 9, for example, a side-emitting semiconductor laser is used, and from the light emitting element 9, for example, a laser beam of about 405 nm is emitted.

  A rising mirror 35 and an output control element 36 are disposed on the lower surface side of the lead frame 31. The output control element 36 has an APC (Automatic Power Control) function for controlling the amount of laser light emitted from the light emitting element 9 to be constant.

  A light receiving element 34 is disposed on the upper surface side of the lead frame 31. The light receiving element 34 is provided with a first light receiving portion 34a and a second light receiving portion 34b. On the light receiving element 34, for example, a light control member 29A having a slit 29e is disposed.

  A half-wave plate 37 is disposed on the upper surface of the package 30.

  The opening on the upper side of the package 30 is closed by a compound lens 38. On the upper surface of the compound lens 38, for example, a first light diffracting portion 38a, a second light diffracting portion 38b, and a third light diffracting portion 38c each formed of a diffraction grating are formed. On the lower surface of the compound lens 38, a focal length changing lens portion 38d is formed at a position directly below the second light diffracting portion 38b.

  A composite element 39 is disposed on the upper surface side of the composite lens 38. The composite element 39 is formed with a polarizing prism portion 39a, a half mirror portion 39b, and a reflecting mirror portion 39c. The laser beam may be separated using a diffraction grating instead of the polarizing prism portion 39a.

  A collimator lens 10, a quarter wavelength plate 40, and an objective lens 12 are disposed above the polarizing prism portion 39 a of the composite element 39.

  In the optical pickup 6F, when laser light is emitted from the light emitting element 9, a part of the emitted laser light is reflected by the rising mirror 35 and guided to the compound lens 38 via the half-wave plate 37. The direction of polarization of the laser light is rotated in an arbitrary direction by the half-wave plate 37.

  Of the laser light emitted from the light emitting element 9, a portion that is not reflected by the raising mirror 35 is transmitted through the raising mirror 35, reflected by the lid 32, and received by the output control element 36. When the laser light is received by the output control element 36, the output of the laser light detected by the output control element 36 is fed back to the current input of the light emitting element 9, and the light quantity of the laser light emitted from the light emitting element 9 is constant. It is controlled to become.

  The laser light incident on the compound lens 38 is diffracted by the first light diffracting portion 38a, and a main light beam (zero-order light) that forms a main spot on the recording track of the disc-shaped recording medium 100 and a main recording beam. Separated into sub-beams (± first-order light) that form sub-spots at positions separated from the spot.

  The diffracted laser light is transmitted through the polarizing prism portion 39 a of the composite element 39, converted into a parallel light beam by the collimator lens 10, then circularly polarized by the quarter wavelength plate 40, and disc-shaped through the objective lens 12. The light is condensed on the recording layer of the recording medium 100.

  The laser light is reflected by the recording layer of the disc-shaped recording medium 100 and is incident on the polarizing prism portion 39a of the composite element 39 via the objective lens 12, the quarter wavelength plate 40, and the collimator lens 10, and the polarizing prism portion 39a. Therefore, the optical path is converted and is incident on the half mirror 39b.

  Part of the laser light incident on the half mirror 39b is reflected and the other part is transmitted, the reflected part is incident on the second light diffraction part 38b of the compound lens 38, and the transmitted part is reflected. The light is reflected by the mirror unit 39 c and is incident on the third light diffraction unit 38 c of the compound lens 38.

  The second light diffracting section 38b and the third light diffracting section 38c have the same function as the diffraction elements 18 and 18A, and the first light of the laser beam reflected by the layer where information is not recorded or reproduced. It has a role of preventing incidence as stray light to the light receiving part 34a and the second light receiving part 34b.

  The laser light incident on the second light diffracting unit 38b is diffracted by the second light diffracting unit 38b, the focal length is changed by the focal length changing lens unit 38d, and then the first light receiving unit of the light receiving element 34. It is incident on 34a and received.

  The laser light incident on the third light diffracting portion 38c is diffracted by the third light diffracting portion 38c and transmitted through the slit 29e or the transmitting portion 29f of the light control member 29A, and then the second light of the light receiving element 34. Incident light is received by the light receiving portion 34b.

  The first light receiving unit 34a and the second light receiving unit 34b are arbitrarily divided. For example, using the laser light received by the first light receiving unit 34a, focus error detection by the SSD method or tracking error detection by the DPP method Can be done. In addition, it is possible to perform RF detection, tracking error detection by the DPD method, address detection, spherical aberration detection, land groove detection, and crosstalk detection using the laser light received by the second light receiving unit 34b.

  As described above, even in the optical pickup 6F, similarly to the optical pickup 6A, the first light receiving portion 34a of the laser light reflected by the recording layer on which the information of the disk-shaped recording medium 100 is not recorded or reproduced, and Since the incidence on the second light receiving unit 34b is limited, no stray light is generated, and no RF signal deterioration or servo signal offset occurs. Further, the interference of the laser light reflected by each layer of the disk-shaped recording medium 100 does not occur, and the device characteristics hardly change due to environmental changes such as temperature changes.

  In addition, since there is no need to increase the vertical magnification of the optical system or to reduce the area of each light receiving section, the change in spot diameter with respect to defocusing is small, and the spot position shift due to the position shift of each optical component It is small and easy to adjust the position, and is less susceptible to subsequent changes with time and environmental changes.

  Furthermore, since an integrated optical element is used, the size can be reduced.

  The specific shapes and structures of the respective parts shown in the respective best modes for carrying out the invention described above are merely examples of the embodiments in carrying out the present invention, and the present invention is thereby limited. The technical scope of the invention should not be limitedly interpreted.

FIG. 2 to FIG. 53 show the best mode for carrying out the present invention, and this figure is a schematic perspective view of a disk drive device. It is a conceptual diagram of a disk-shaped recording medium. 4 to 12 show the first best mode of the optical pickup, and this figure is a conceptual diagram showing the overall configuration. It is a perspective view of a light shielding member. It is a conceptual diagram which shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is recorded or reproduced and the light receiving state in the light receiving unit. It is a conceptual diagram which shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is not recorded or reproduced, and the light receiving state in the light receiving unit. It is a conceptual diagram which shows another state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows another state of the laser beam reflected by the recording layer in which information is not recorded or reproduced | regenerated, and another light-receiving state in a light-receiving part. It is a conceptual diagram which shows the modification of a light-receiving part. It is a conceptual diagram which shows another modification of a light-receiving part. FIG. 14 to FIG. 23 show a second best mode of the optical pickup, and this figure is a conceptual diagram showing the overall configuration. It is a perspective view of a prism. It is a conceptual diagram which shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is recorded or reproduced and the light receiving state in the light receiving unit. It is a conceptual diagram which shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is not recorded or reproduced, and the light receiving state in the light receiving unit. It is a conceptual diagram which shows another state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed, and another light-receiving state in a light-receiving part. It is a conceptual diagram which shows the modification of a light-receiving part. It is a conceptual diagram which shows another modification of a light-receiving part. It is a conceptual diagram which shows another modification of a light-receiving part. FIG. 25 to FIG. 30 show the third best mode of the optical pickup, and this figure is a conceptual diagram showing the overall configuration. It is a perspective view of a diffraction element. It is a conceptual diagram which shows a light-receiving part. It is a conceptual diagram which shows the modification of a light-receiving part. It is a perspective view which shows the modification of a diffraction element. It is a conceptual diagram which shows another modification of a light-receiving part. It is a conceptual diagram which shows another modification of a light-receiving part. FIG. 32 to FIG. 43 show the fourth best mode of the optical pickup, and this figure is a conceptual diagram showing the overall configuration. It is a perspective view of a light shielding member. It is a perspective view which shows the modification of a light shielding member. It is a perspective view of a prism. It is a conceptual diagram which expands and shows the light reception state in the light-receiving part of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is performed. It is a conceptual diagram which expands and shows the light reception state in the light-receiving part of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows another light reception state in the light-receiving part of the laser beam reflected by the recording layer in which information is not recorded or reproduced | regenerated. It is a conceptual diagram which shows the modification of the light-receiving part at the time of using a light-shielding member. It is a conceptual diagram which shows another modification of the light-receiving part at the time of using a light-shielding member. It is a conceptual diagram which shows the example of the light-receiving part at the time of using a prism. It is a conceptual diagram which shows the example of the light-receiving part at the time of using a diffraction element. It is a conceptual diagram which shows the modification of the light-receiving part at the time of using a diffraction element. It is a conceptual diagram which shows another modification of the light-receiving part at the time of using a diffraction element. FIG. 45 to FIG. 52 show a fifth best mode of the optical pickup, and this figure is a conceptual diagram showing the overall configuration. It is a perspective view of the light control member shown in the state arrange | positioned at a light receiving element. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is not recorded or reproduced. It is a conceptual diagram which expands and shows another state of the laser beam reflected by the recording layer in which information is not recorded or reproduced | regenerated. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is performed when a prism or a diffraction element is used. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed when a prism or a diffraction element is used. It is a conceptual diagram which expands and shows another state of the laser beam reflected by the recording layer in which recording or reproduction | regeneration of information is not performed when a prism or a diffraction element is used. It is a perspective view of the light control member shown in the state arrange | positioned at a light receiving element. It is a conceptual diagram which shows the 6th best form of an optical pick-up, and shows the whole structure. FIG. 55 to FIG. 59 show the state of laser light in a conventional optical pickup, and this figure is a conceptual diagram showing the state of laser light reflected by a recording layer where information is recorded or reproduced. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is recorded or reproduced and the light receiving state in the light receiving unit. It is a conceptual diagram which shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer where information is not recorded or reproduced, and the light receiving state in the light receiving unit. It is a conceptual diagram which shows another state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed. It is a conceptual diagram which expands and shows the state of the laser beam reflected by the recording layer in which information recording or reproduction | regeneration is not performed, and another light-receiving state in a light-receiving part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Disc-shaped recording medium, L1 ... Recording layer, L0 ... Recording layer, 1 ... Disc drive apparatus, 3 ... Disc table, 6 ... Optical pick-up, 7 ... Moving base, 8 ... Objective lens drive device, 9 ... Light emitting element, DESCRIPTION OF SYMBOLS 11 ... Light separation element, 12 ... Objective lens, 13 ... Light shielding member, 13a ... Light shielding part, 15 ... Light receiving element, 16 ... Prism, 16a ... Refraction part, 17 ... Light receiving element, 18 ... Diffraction element, 18a ... Diffraction part, DESCRIPTION OF SYMBOLS 19 ... Light receiving element, 18A ... Diffraction element, 18c ... Diffraction part, 20 ... Diffraction grating, 21 ... Light receiving element, 13A ... Light shielding member, 13c ... Light shielding part, 13B ... Light shielding member, 13e ... Light shielding part, 16A ... Prism, 16c ... Refracting part, 34 ... Light receiving element

Claims (5)

An optical pickup comprising a moving base that is moved in the radial direction of a disk-shaped recording medium on which a plurality of recording layers to be mounted on a disk table is formed, and an objective lens driving device disposed on the moving base,
A light emitting element that emits laser light toward a disk-shaped recording medium;
An objective lens for condensing the laser light emitted from the light emitting element onto a recording layer of a disk-shaped recording medium;
A light receiving element having a light receiving portion for receiving the laser beam reflected by the recording layer of the disk-shaped recording medium;
A light separating element that guides the laser light emitted from the light emitting element to the objective lens and guides the laser light reflected by the recording layer of the disk-shaped recording medium to the light receiving element;
In the optical path from the disc-shaped recording medium to the light receiving element, a diffraction element having a diffraction part that diffracts the central part of the laser beam is provided,
Do not allow at least the central part of the laser beam reflected by a layer different from the recording layer where information is recorded or reproduced by the diffraction element to enter the light receiving part of the light receiving element,
The diffractive portion of the diffractive element is formed to extend in a tangential direction substantially parallel to the recording track of the disk-shaped recording medium,
The light receiving part of the light receiving element is divided into two in the radial direction,
The laser beam that passes through the part other than the diffractive part of the diffractive element is divided into two with the diffractive part in between,
The laser beam is diffracted by the diffraction part of the diffractive element to generate ± first order light
One of the divided light receiving portions receives one laser beam and + 1st order light sandwiched by the diffraction portion and the other divided light receiving portion sandwiches the diffraction portion and the other of the two divided light receiving portions. An optical pickup characterized by receiving laser light and negative primary light and performing tracking error detection by a push-pull method . 2. The optical pickup according to claim 1 , wherein only one spot of laser light is formed on the recording layer of the disk-shaped recording medium. A diffraction grating is provided in the optical path from the light emitting element to the disk-shaped recording medium to separate the laser light emitted from the light emitting element into a main light beam and a pair of sub light beams,
The optical pickup according to claim 1 , wherein three spots of laser light composed of a main spot and a pair of sub-spots are formed on a recording layer of a disk-shaped recording medium. 2. The optical pickup according to claim 1 , wherein address signals are detected by detecting phase information of wobbles formed on a recording track of a disc-shaped recording medium using a light receiving portion of the light receiving element. A disk drive apparatus comprising: a disk table on which a disk-shaped recording medium having a plurality of recording layers is mounted; and an optical pickup having an objective lens driving device and a moving base that is moved in the radial direction of the disk-shaped recording medium Because
The above optical pickup
A light emitting element that emits laser light toward a disk-shaped recording medium;
An objective lens for condensing the laser light emitted from the light emitting element onto a recording layer of a disk-shaped recording medium;
A light receiving element having a light receiving portion for receiving the laser beam reflected by the recording layer of the disk-shaped recording medium;
A light separating element that guides the laser light emitted from the light emitting element to the objective lens and guides the laser light reflected by the recording layer of the disk-shaped recording medium to the light receiving element;
In the optical path from the disc-shaped recording medium to the light receiving element, a diffraction element having a diffraction part that diffracts the central part of the laser beam is provided,
Do not allow at least the central part of the laser beam reflected by a layer different from the recording layer where information is recorded or reproduced by the diffraction element to enter the light receiving part of the light receiving element,
The diffractive portion of the diffractive element is formed to extend in a tangential direction substantially parallel to the recording track of the disk-shaped recording medium,
The light receiving part of the light receiving element is divided into two in the radial direction,
The laser beam that passes through the part other than the diffractive part of the diffractive element is divided into two with the diffractive part in between,
The laser beam is diffracted by the diffraction part of the diffractive element to generate ± first order light
One of the divided light receiving portions receives one laser beam and + 1st order light sandwiched by the diffraction portion and the other divided light receiving portion sandwiches the diffraction portion and the other of the two divided light receiving portions. A disk drive device characterized by receiving laser light and −1st order light and performing tracking error detection by a push-pull method .

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