JP2011159361A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which uses only one one-dimensional diffraction grating having a constant grating pitch in an optical path from a light source to an optical recording medium, thereby reducing the number of steps in an assemble adjustment process and adjustment time. <P>SOLUTION: The optical pickup device includes a first laser light source 11a, a second laser light source 11b, a photodetector 30, an optical system, and a controller 10 for focus control and tracking control. The optical system includes the one-dimensional diffraction grating 12, and a diffraction element 16 which diffracts and branches light returning from an optical disk. The photodetector 30 includes a first photodetection section which detects the intensity of first laser light, and a second photodetection section which detects the intensity of second laser light. The first photodetection section includes a light receiving part which receives zeroth-order diffracted light from the diffraction element 16, and a light receiving part which receives ±first-order diffracted light from the diffraction element 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical pickup device used for reproducing or recording an optical disc such as a CD (compact disc), a DVD (digital versatile disc), and a BD (Blu-ray disc).

  2. Description of the Related Art Conventionally, there has been known a pickup equipped with a two-wavelength multi-laser and using a DPP (Differential Push Pull) method for generating a tracking error signal and an astigmatism method for generating a focus error signal. .

  For example, in Patent Document 1, in order to detect each light beam intensity of a light beam branched by a diffraction grating, three photodetectors are arranged for each wavelength of laser light, and signals from the respective photodetectors are arranged. Discloses an optical pickup device that generates a tracking error signal and a focus error signal.

  The optical pickup device uses a two-wavelength multi-laser and arranges two diffraction gratings having different pitches on a DVD or CD optical path. At this time, in order to eliminate disturbance caused by the diffracted light that is not necessary originally generated when the DVD light beam is branched by the CD diffraction grating, three rows are used so that unnecessary diffracted light does not enter the photodetector. The positions of the photodetectors arranged in two rows are optimized, and stable CD or DVD recording or reproduction is realized.

  The optical pickup device disclosed in Patent Document 1 will be described in more detail with reference to FIG.

  First, the DVD optical system will be described. In the DVD optical system, as shown in FIG. 12, a DVD light beam is emitted as divergent light from a DVD laser chip 102 provided inside a two-wavelength multi-laser unit 101 in an optical pickup device 100. The dotted line 104 in the figure indicates the optical path of the DVD light beam.

  The DVD light beam emitted from the DVD laser chip 102 enters the diffraction grating 106. The diffraction grating 106 has a function of splitting the light beam into three, and the three light beams are used for generating a tracking error signal by the three-beam DPP method and a focus error signal by the differential astigmatism method. . The diffraction grating 106 is formed by bonding together a diffraction grating dedicated to DVD and a diffraction grating dedicated to CD having different grating pitches, and is a diffraction grating dedicated to DVD which is a diffraction pattern dedicated to DVD and a diffraction grating dedicated to CD. A certain CD lattice pattern 108 is arranged.

  Due to the diffraction grating 106 having the above configuration, the DVD light beam incident on the diffraction grating 106 is optimal for generating a tracking error signal by the three-beam DPP method so as to correspond to the DVD-R and DVD-RAM by the DVD grating pattern 107. Are split into three light beams. In the case of DVD-R, it is possible to generate only a tracking error signal by the 1-beam DPP method. The DVD light beam that has passed through the DVD grating pattern 107 passes through the CD grating pattern 108.

The DVD light beam that has passed through the CD grating pattern 108 is reflected by the beam splitter 109, guided to the collimating lens 110, and converted into a substantially parallel light beam. The DVD light beam emitted from the collimator lens 110 is reflected on the rising mirror 111 in the z direction (perpendicular to the paper surface) in the figure, and condensed on an optical disk (not shown) by an objective lens 112 mounted on an actuator (not shown). Is done. The DVD optical beam is reflected by the optical disk, and reaches the photodetector 120 through the objective lens 112, the rising mirror 111, the collimator lens 110, the beam splitter 109, and the detection lens 113.

  Next, the CD optical system will be described. In the CD optical system, as shown in FIG. 12, a CD light beam is emitted as divergent light from a CD laser chip 103 provided inside a two-wavelength multi-laser unit 101 in the optical pickup device 100. An alternate long and short dash line 105 in the drawing indicates the optical path of the CD light beam. After the emission, the CD light beam incident on the diffraction grating 106 through the same path as the DVD light beam 3 is optimal for generating a tracking error signal by the three-beam DPP method of the CD by the CD grating pattern 108. It will be branched into a light beam of books. Thereafter, the CD light beam is collected on the optical disc, reflected by the optical disc, and reaches the photodetector 114.

  Here, since the arrangement position of the CD laser chip 103 is different from the arrangement position of the DVD laser chip 102, the CD light beam is condensed on the photodetector 120 at a position different from the DVD light beam. The Therefore, in the optical pickup device 100 using the two-wavelength multi-laser, it is necessary to use two rows of photodetectors, that is, a DVD photodetector 121 and a CD photodetector 122 as shown in FIG. . Further, both the DVD photodetector 121 and the CD photodetector 122 are arranged in three rows because a sub light beam is required to generate a tracking error signal by DPP for both DVD and CD. It is.

  In the DVD photodetector 121, the detection area 121a receives the DVD main light beam 131, and the detection areas 121b and 121c receive the DVD sub light beams 132 and 133, respectively. In the CD photodetector 122, the detection area 122a receives the CD main light beam 141, and the detection areas 122b and 122c receive the CD sub light beams 142 and 143, respectively.

  In Patent Document 1, the distance between the detection areas 121b and 121c at both ends of the three detection areas 121a, 121b, and 121c that receives the DVD light beam is defined as the three detection areas that receive the CD light beam. By making the distance longer than the distance between the detection areas 121b and 121c at both ends of 122a, 122b and 122c, stable CD or DVD recording or reproduction is realized.

  That is, not only a DVD light beam but also a CD light beam is incident on the DVD lattice pattern 107 dedicated to DVD, and not only a CD light beam but also a DVD light beam is incident on the CD lattice pattern 108 dedicated to CD. To do. For this reason, DVD sub-beams 132 and 133 are generated in the DVD grating pattern 107 and disturbance light beams 151 and 152 are generated in the CD grating pattern 108. Further, CD sub-beams 142 and 143 are generated by the CD grating pattern 108, and disturbance light beams 153 and 154 are generated by the DVD grating pattern 107.

  In this regard, in Patent Document 1, as described above, the positions of the photodetectors arranged in 3 rows and 2 columns are set appropriately so that the disturbance light beam, the main light beam, and the sub light beam do not overlap on the detection region. Thus, stable CD or DVD recording or reproduction is realized.

JP 2007-35109 A (released on February 8, 2007)

  However, in the conventional optical pickup device described in Patent Document 1, different diffraction gratings are used for DVD and CD. For this reason, it is necessary to adjust the diffraction grating for DVD using the light beam for DVD, while it is necessary to adjust the diffraction grating for CD using the light beam for CD. There's a problem.

  Also, in the optical pickup device described in Patent Document 1, when realizing a dual-wavelength multilaser-mounted optical pickup compatible with a super-multi compatible optical disk drive, it is divided into three regions as a diffraction grating for DVD, and 90 degrees each. A two-wavelength diffraction grating having a grating pattern with different phases is required. When this two-wavelength diffraction grating is used, the DVD light beam has to be incident on the center of the grating. For assembly adjustment, the optical axis direction, the direction perpendicular to the diffraction grating division direction, and the rotation of the diffraction grating Adjustment of direction is required, and very precise positioning accuracy is required. For example, in Patent Document 1, the intensity of the beam incident on the left and right regions of the diffraction grating for DVD must be adjusted to be equal. For this reason, it becomes a factor which obstructs shortening of assembly adjustment time.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to use only one one-dimensional diffraction grating having a constant grating pitch in the optical path from the light source to the optical recording medium. Another object of the present invention is to provide an optical pickup device capable of reducing the number of steps in the assembly adjustment process and the adjustment time.

  In order to solve the above problems, an optical pickup device of the present invention emits a first laser light source that emits first laser light and a second laser light having a wavelength different from that of the first laser light source. The second laser light source and each of the first laser light or the second laser light emitted from the first laser light source or the second laser light source is received and converted into an electrical signal corresponding to the intensity of the light beam. A photodetector for conversion, and each of the first laser light or the second laser light emitted from the first laser light source or the second laser light source is guided to the optical recording medium and returned from the optical recording medium; An optical system that guides light to the photodetector, and a control unit that generates a focus error signal and a tracking error signal from the return light from the optical recording medium, and performs focus control and tracking control. On A one-dimensional diffraction grating having a constant grating pitch for diffracting and branching each first laser light or second laser light emitted from the first laser light source or the second laser light source, and the optical recording medium Each of the first laser beams emitted from the first laser light source and branched by the one-dimensional diffraction grating. A first light detector that detects the light beam intensity of the second laser beam, and a light beam intensity of the second laser light emitted from the second laser light source and branched by the one-dimensional diffraction grating. A second light detector, wherein the first light detector receives a 0th-order diffracted light receiving portion that receives 0th-order diffracted light from the diffractive element, and ± 1st-order diffracted light from the diffractive element. Diffraction element 1st order diffracted light It is characterized by comprising a light receiving part. Note that the one-dimensional diffraction grating is a diffraction grating in which the grating is striped, and the one-dimensional diffraction grating of the present invention has a uniform grating pitch, so that the stripe spacing is uniform.

  According to the above invention, the optical system has a grating pitch that diffracts and branches each of the first laser light or the second laser light emitted from the first laser light source or the second laser light source. A fixed one-dimensional diffraction grating and a diffraction element for diffracting and branching the return light from the optical recording medium are provided.

By the way, in the conventional optical pickup device described in Patent Document 1, a DVD laser light source as a first laser light source or a CD laser as a second laser light source arranged in the optical path from the light source to the optical recording medium. The diffraction grating that diffracts and splits the DVD laser light or CD laser light emitted from the light source uses two types of diffraction gratings having different grating pitches so as to correspond to the DVD laser light source or the CD laser light source. It was. As a result, the two types of diffraction gratings need to be adjusted, so that there is a problem that assembly adjustment takes time.

  In the prior art described in Patent Document 1, when realizing a dual-wavelength multi-laser-mounted optical pickup compatible with a super-multi compatible optical disk drive, a DVD light beam is accurately incident on the center of a two-wavelength diffraction grating in a DVD. Therefore, it is necessary to adjust the optical axis direction of the two-wavelength diffraction grating, the direction perpendicular to the dividing direction of the diffraction grating, and the rotation direction of the diffraction grating, and very precise positioning accuracy is required. It was a factor that hindered shortening.

  On the other hand, in the present invention, a diffraction grating that diffracts and branches the laser light emitted from the first laser light source or the second laser light source is one-dimensional diffraction in the optical path from the light source to the optical recording medium. Since there is only one kind of grating, a one-dimensional diffraction grating using either the first laser light emitted from the first laser light source or the second laser light emitted from the second laser light source What is necessary is just to adjust the assembly adjustment. For this reason, it does not take time and effort to assemble and adjust as compared with the prior art.

  Here, in the present invention, the first laser light or the second laser light emitted from the first laser light source or the second laser light source is branched into three beams by a one-dimensional diffraction grating to be an optical recording medium. The return light from the optical recording medium is diffracted by the diffraction element.

  The first light detection unit detects the light beam intensity of the first laser light emitted from the first laser light source and branched by the one-dimensional diffraction grating. Specifically, the 0th-order diffracted light receiving portion of the diffractive element receives 0th-order diffracted light and 0th-order diffracted light from the diffractive element in the ± 1st-order diffracted light, while the diffractive element first-order diffracted light receiving portion receives. The first-order diffracted light from the diffraction element in the zero-order diffracted light of the one-dimensional diffraction grating is received.

  As a result, the control unit receives the zero-order diffracted light from the diffractive element in the one-dimensional diffraction grating from the first laser light source and the zero-order diffracted light from the diffracting element in the ± first-order diffracted light, respectively. For example, tracking control can be performed by a 3-beam DPP method in a DVD-RAM.

  The second light detection unit detects the light beam intensity of the second laser light emitted from the second laser light source and branched by the one-dimensional diffraction grating. Accordingly, the control unit receives the 0th order diffracted light from the diffraction element in the one-dimensional diffraction grating from the second laser light source and the 0th order diffracted light in the ± 1st order diffracted light from the second laser light source. For example, tracking control can be performed on a CD by the three-beam DPP method.

  On the other hand, when the control unit performs tracking control by the 1-beam DPP method, for example, the first laser light emitted from the first laser light source is converted into one beam of only the 0th-order diffracted light by the one-dimensional diffraction grating. The return light from the optical recording medium is then diffracted by the diffractive element. In the present invention, only the first-order diffracted light from the diffractive element in the diffractive element is received by the first-order diffracted light of the diffractive element. It is possible to receive light at the part. Thus, the first-order diffracted light receiving unit of the diffractive element receives ± 1st-order diffracted light from the diffractive element in the 0th-order diffracted light of the one-dimensional diffraction grating from the first laser light source. Tracking control can be performed by the DPP method.

  As described above, in the present invention, for example, the 1-beam DPP method using only the 0th-order diffracted light of the one-dimensional diffraction grating among the returned light from the optical recording medium is employed for generating the tracking error signal of DVD-R. Thus, an optical pickup device equipped with a two-wavelength multi-laser can be configured to use only one diffraction grating in the optical path from the light source to the optical recording medium. As a result, it is possible to perform recording / reproduction on a plurality of types of optical recording media only by performing assembly adjustment of the diffraction grating with either the first laser light source or the second laser light source, and the optical axis direction, etc. Therefore, it is possible to provide an optical pickup device that can reduce the man-hours for the assembly adjustment process and shorten the adjustment time.

  Therefore, by using only one one-dimensional diffraction grating having a constant grating pitch in the optical path from the light source to the optical recording medium, the optical pickup device can reduce the man-hours for the assembly adjustment process and the adjustment time. Can be provided.

  In the optical pickup device of the present invention, the first laser light source is a DVD laser light source that emits laser light for a DVD (digital versatile disk), and the second laser light source is for a CD (compact disk). The CD light source emits the laser light, and the first light detector is a DVD light receiver that receives the DVD laser light emitted from the DVD laser light source, and the second light. The detection unit is preferably a CD light receiving unit that receives the CD laser light emitted from the CD laser light source.

  As a result, when the optical recording medium is a DVD or CD, the number of man-hours in the assembly adjustment process can be reduced by using only one one-dimensional diffraction grating having a constant grating pitch in the optical path from the light source to the optical recording medium. It is possible to provide an optical pickup device that can reduce the adjustment time.

  In the optical pickup device of the present invention, when the optical recording medium is a DVD-RAM or a CD, the control unit performs tracking using ± first-order diffracted light and zero-order diffracted light branched by the one-dimensional diffraction grating. On the other hand, when the optical recording medium is a DVD-R, tracking control is preferably performed using ± first-order diffracted light from the diffraction element in the zero-order diffracted light of the one-dimensional diffraction grating.

  Thus, when the optical recording medium is a DVD-RAM or CD, tracking control is performed by the three-beam DPP method using the zero-order diffracted light of the one-dimensional diffraction grating and the ± first-order diffracted light of the one-dimensional diffraction grating. be able to.

  When the optical recording medium is a DVD-R, tracking control can be performed by the 1-beam DPP method using 0th-order diffracted light of a one-dimensional diffraction grating and ± 1st-order diffracted light of a diffraction element.

  In the optical pickup device of the present invention, it is preferable that the diffraction element diffracts the return light from the optical recording medium in different directions for each designated pattern region.

  Thereby, each light reception area | region of the diffraction element primary diffraction light light-receiving part in a 1st light detection part can be arrange | positioned in a desired position.

In the optical pickup device according to the aspect of the invention, the first light detection unit may be configured such that the diffraction element zero-order diffracted light receiving unit receives first-order diffracted light from the diffraction element in the zero-order diffracted light of the one-dimensional diffraction grating. A main main beam receiving unit for laser light, and a first sub-main beam receiving unit for laser light that receives 0th-order diffracted light from the diffractive element in ± 1st-order diffracted light of a one-dimensional diffraction grating, The first-order diffracted light receiving section includes four first laser beam main sub-beam receiving sections for receiving ± first-order diffracted light from the diffraction element in the zero-order diffracted light of the one-dimensional diffraction grating, and the second order The light detection unit includes a second main main beam receiving unit for laser light that receives zero-order diffracted light from the diffraction element in the zero-order diffracted light of the one-dimensional diffraction grating from the second laser light source, and the second laser beam. Preferably, it comprises a second laser beam sub-main beam light receiving portion for receiving 0th-order diffracted light from the diffraction element in ± 1st-order diffracted light of the one-dimensional diffraction grating from the user light source.

  Thus, for example, when tracking control is performed by the three-beam DPP method when the optical recording medium is a DVD-RAM, the 0th-order diffracted light from the diffraction element in the 0th-order diffracted light of the one-dimensional diffraction grating is The first-order diffracted light receiving section of the first main beam for laser beam of the diffractive element in FIG. 1 receives the first-order diffracted light from the diffracting element in the ± first-order diffracted light of the one-dimensional diffraction grating. The light is received by the first sub-beam receiving section for the laser beam of the diffraction element zero-order diffracted light receiving section in the detection section.

  Further, for example, when tracking control is performed by the three-beam DPP method when the optical recording medium is a CD, the 0th-order diffracted light from the diffraction element in the 0th-order diffracted light of the one-dimensional diffraction grating is the second light in the second light detection unit. On the other hand, the 0th-order diffracted light from the diffraction element in the ± 1st-order diffracted light of the one-dimensional diffraction grating is received by the second laser beam sub-main beam light-receiving unit. .

  On the other hand, for example, when tracking control is performed by the 1-beam DPP method when the optical recording medium is a DVD-R, the ± 1st-order diffracted light from the diffraction element in the 0th-order diffracted light of the one-dimensional diffraction grating is the first light detection unit. Are received by the four first laser beam main sub-beam light receiving parts of the diffraction element primary diffraction light receiving part.

  Thereby, when tracking control of DVD-RAM, CD, or DVD-R is performed by the 3-beam DPP method or the 1-beam DPP method, a specific light receiving unit is specified.

  In the optical pickup device of the present invention, a BD laser light source that emits a BD (Blu-ray Disc) laser beam different from the first laser light source and the second laser light source, the one-dimensional diffraction grating, and the optical recording medium And an optical coupling means that bends the BD laser light emitted from the BD laser light source in the direction of the optical recording medium and passes the first laser light or the second laser light. And the first-order diffracted light receiving unit of the first light detecting unit receives ± first-order diffracted light from the diffractive element in the return light from the optical recording medium in the BD laser light. When the optical recording medium is a BD, the control unit preferably performs tracking control by a one-beam DPP method.

  Thereby, even when a BD is added as an optical recording medium, an optical coupling means is added, and four BD sub-beam light receiving parts are added to the diffractive element first-order diffracted light receiving part in the first light detecting part. Thus, tracking control of the BD can be performed by the 1-beam DPP method.

As described above, the optical pickup device of the present invention has the first laser light source that emits the first laser light and the second laser light that emits the second laser light having a wavelength different from that of the first laser light source. Light that receives a laser light source and the first laser light or the second laser light emitted from the first laser light source or the second laser light source and converts them into an electrical signal corresponding to the intensity of the light beam. A detector, and each of the first laser light and the second laser light emitted from the first laser light source or the second laser light source is guided to an optical recording medium, and return light from the optical recording medium is An optical system that leads to the photodetector, and a control unit that generates a focus error signal and a tracking error signal from the return light from the optical recording medium, and performs focus control and tracking control. 1st race A one-dimensional diffraction grating having a constant grating pitch for diffracting and branching the first laser light or the second laser light emitted from the light source or the second laser light source, and the return light from the optical recording medium Each of the light beam intensities of the first laser beam emitted from the first laser light source and branched by the one-dimensional diffraction grating. And a second light for detecting the intensity of each light beam in the second laser light emitted from the second laser light source and branched by the one-dimensional diffraction grating. A first detector, and a first diffracting element that receives zero-order diffracted light from the diffractive element and a diffractive element that receives ± first-order diffracted light from the diffractive element. From the next diffracted light receiver It is configured.

  Therefore, by using only one one-dimensional diffraction grating having a constant grating pitch in the optical path from the light source to the optical recording medium, it is possible to reduce the man-hours for the assembly adjustment process and the adjustment time. The effect of providing a device is achieved.

1 shows an embodiment of an optical pickup device according to the present invention, and is a plan view showing a configuration of the optical pickup device. It is a top view which shows the division pattern of the diffraction element in the said optical pick-up apparatus, and the beam pattern of the return light from an optical disk. It is a top view which shows the structure of the photodetector in the said optical pick-up apparatus. It is a top view which shows the pending relationship of the said diffraction element and a 1st-order diffracted light light-receiving part. It is a top view which shows the grating pattern of the one-dimensional diffraction grating in the said optical pick-up apparatus. (A) is a top view which shows spot arrangement | positioning of the light beam irradiated on DVD-R, (b) is a top view which shows spot arrangement | positioning of the light beam irradiated on DVD-RAM, (c ) Is a plan view showing a spot arrangement of a light beam irradiated on a CD. It is explanatory drawing which shows arrangement | positioning of the optical component in the said optical pick-up apparatus, and the positional relationship of the spot formed on an optical disk. FIG. 7 is a plan view showing another embodiment of the optical pickup device according to the present invention and showing the configuration of the optical pickup device. It is a top view which shows the structure of the photodetector in the said optical pick-up apparatus. It is a top view which shows the suspending relationship between the diffraction element in the said optical pick-up apparatus, and the diffraction element 1st-order diffracted light light-receiving part for BD. It is a top view which shows the pending relationship of the diffraction element of the modification in the said optical pick-up apparatus, and the diffraction element 1st-order diffracted light light-receiving part for BD. It is a top view which shows the structure of the conventional optical pick-up apparatus. It is a top view which shows the structure of the photodetector in the said conventional optical pick-up apparatus.

[Embodiment 1]
One embodiment of the present invention is described below with reference to FIGS.

  The optical pickup device of the present embodiment will be described with reference to FIG. FIG. 1 is a plan view showing the configuration of the optical pickup device of the present embodiment.

  The optical pickup device 1 according to the present embodiment is applied to an optical disc 40 (to be described later) as a plurality of optical recording media such as various DVDs (digital versatile discs) [DVD-R, DVD-RAM, etc.] and CDs (compact discs). On the other hand, information can be recorded and reproduced.

  As shown in FIG. 1, the optical pickup device 1 includes a two-wavelength multilaser 11, a one-dimensional diffraction grating 12, a collimator lens 13, a light separation element 14, a rising mirror (not shown), and a lens holder 20. The objective lens 21 attached, the detection lens 15, the diffraction element 16, the photodetector 30, and the control unit 10 are provided.

  The two-wavelength multi-laser 11 as the light source includes a first laser light source 11a that is a DVD laser light source that emits a first laser light that is a laser beam for DVD having a wavelength band of 660 nm, and the first laser light source 11a. A second laser light source 11b, which is a laser beam source for CDs that emits a second laser beam, which is a laser beam for CDs whose wavelength band is 785 nm, which has a relatively long wavelength compared to the laser beam, is one unit. Is a semiconductor laser to be mounted on. For example, in the case of DVD, the light emitting light source emits the first laser light from the first laser light source 11a, while in the case of CD, the light emitting light source emits the second laser light from the second laser light source 11b. It is possible to select and use appropriately for each optical disc 40 such as ejecting.

  The laser light emitted from the two-wavelength multilaser 11 is incident on the one-dimensional diffraction grating 12 with a certain spread angle. The thin solid line in FIG. 1 indicates the optical path of the main light beam.

  The one-dimensional diffraction grating 12 has a function of diffracting an incident light beam into three parts, and the three branched light beams are incident on the optical disc 40, and each return light is DPP (Differential Push). Pull: used to generate a tracking error signal by a differential push-pull method or a focus error signal by an astigmatism method or a differential astigmatism method. The three branched beams are, for example, 0th order diffracted light at the center and ± 1st order diffracted light at both ends. A diffraction angle φ, which is an angle formed between 0th-order diffracted light and ± 1st-order diffracted light branched by the one-dimensional diffraction grating 12, is expressed by the following equation.

φ = sin ⁻¹ (λ / Λ)
Here, λ indicates the wavelength of the laser beam, and Λ indicates the grating pitch of the one-dimensional diffraction grating 12.

  The light beam that has passed through the one-dimensional diffraction grating 12 becomes parallel light at the collimator lens 13. Then, the light passes through the light separation element 14, is reflected by a rising mirror (not shown), and is condensed on the optical disk 40 through the objective lens 21.

  The light separating element 14 transmits linearly polarized light such as P-polarized light in the laser light emitted from the first laser light source 11 a or the second laser light source 11 b of the two-wavelength multilaser and is reflected by the optical disk 40. Is designed to reflect linearly polarized light such as S-polarized light. The light separation element 14 is, for example, a polarization beam splitter.

  The reflected light reflected by the optical disk 40 is reflected again by the light separating element 14 via the objective lens 21 and guided in a direction different from that of the two-wavelength multi-laser 11. Then, the light passes through the detection lens 15 and enters the diffraction element 16.

  The detection lens 15 is a lens having a concave surface on one surface and a cylindrical surface on the other surface. The cylindrical surface generates astigmatism in the light beam.

  The diffraction element 16 has a function of diffracting and splitting an incident light beam in different directions for each designated pattern region, and each branched light beam is incident on a photodetector 30 arranged at a predetermined position. To do. The diffraction element 16 is, for example, a hologram element.

  The light beam diffracted by the diffraction element 16 enters the photodetector 30 and is used by the control unit 10 to generate a tracking error signal and a focus error signal.

  As shown in FIG. 3, the photodetector 30 includes a first photodetector 31 that detects a tracking error signal and a focus error signal from laser light emitted from the first laser light source 11a, and a second laser. The second light detection unit 32 detects a tracking error signal and a focus error signal from the laser light emitted from the light source 11b.

  The first light detector 31 is diffracted by the diffractive element 16 and the diffractive element 0-order diffracted light receiving part 35 that receives the three light beams that have passed through the diffractive element 16 as the 0th-order diffracted light. In addition, each of the light receiving elements receives ± first order diffracted light.

  In this embodiment, the wavelength of the light source of the two-wavelength multilaser is set to 660 nm for the first laser light source for DVD and 785 nm for the CD of the second laser light source. It is not limited to the structure of embodiment, You may replace and use.

  Further, although a two-wavelength multi-laser light source is used for the purpose of reducing the size and weight of the optical pickup device 1, it goes without saying that there is no problem even if a DVD light source and a CD light source are provided separately.

  Although the detection lens 15 is composed of a concave surface and a cylindrical surface, the detection lens 15 is designed based on the distance from the detection lens 15 to the photodetector 30, the size of the light receiving surface, and the like. It is not limited to the content of the form, and it may be composed of a convex surface or a flat surface.

  Next, the diffraction element 16 will be described with reference to FIG. FIG. 2 shows the division pattern of the diffraction element 16 and the beam pattern 17 of the return light from the optical disk 40. The diffraction element 16 is divided into six parts in order to generate a tracking error signal by the one-beam DPP method. In the present embodiment, in order to obtain a push-pull main signal, the split diffraction element 16a and the split diffraction element 16b are divided into two. Further, in order to obtain a sub-signal for detecting the shift of the objective lens 21, the divided diffraction elements 16c to 16f are divided into four. The grating pitch of each region of the diffraction element 16 is determined from the distance to the light receiving portion of the photodetector 30 and the position of the light receiving portion pattern.

  As shown in FIG. 2, it is ideal that the return light from the optical disc 40 is incident on the central portion of the diffractive element 16, but in the configuration of the present embodiment, even if the diffractive element 16 is displaced by about 50 mm. There is no significant effect on the generation of the tracking error signal. Therefore, the positioning adjustment of the diffraction element 16 is not required to be so precise and does not hinder the shortening of the adjustment time.

  In the present embodiment, the diffractive element 16 is divided into six parts, whereby a tracking error signal can be generated efficiently. However, it is sufficient that a tracking error signal can be generated by the one-beam DPP method, and the present invention is not limited to this configuration.

  Next, the photodetector 30 will be described in detail with reference to FIG. FIG. 3 is an explanatory diagram showing the configuration of the photodetector 30.

  The photodetector 30 includes a first light detection unit 31 including a diffractive element zero-order diffracted light receiving unit 35 having three light-receiving elements and a diffractive element first-order diffracted light receiving unit 36 having four light-receiving elements. And a second light detection unit 32 having three light receiving elements. Of the three light receiving elements 35a to 35c of the diffractive element 0th order diffracted light receiving part 35 and one light receiving element 32a among the second light detecting parts 32, four light receiving elements 32a are divided. Further, the two light receiving elements 32b and 32c of the second light detection unit 32 are divided into two.

  The first light detection unit 31 receives a light beam for DVD recording / reproduction. The light receiving element 35a of the diffraction element 0th order diffracted light receiving unit 35 receives the DVD main light beam (the return light of the 0th order diffracted light branched by the one-dimensional diffraction grating 12), while the light receiving element of the diffraction element 0th order diffracted light receiving unit 35 is received. Reference numerals 35b and 35c each receive a DVD sub-light beam (return light of ± first-order diffracted light branched by the one-dimensional diffraction grating 12). The light receiving elements 36a to 36d of the diffractive element first-order diffracted light receiving unit 36 respectively receive the light beams that have passed through the diffractive element 16 as the ± first-order diffracted light. As a result, the light receiving element 35a functions as the first main light beam receiving portion for laser light of the present invention, and the light receiving elements 35b and 35c serve as the first sub main beam light receiving portion for laser light of the present invention. The light receiving elements 36a to 36d have a function as the first laser beam main sub-beam light receiving portion of the present invention.

  The second light detection unit 32 receives a CD light beam. The light receiving element 32a receives the CD main light beam, and the light receiving elements 32b and 32c respectively receive the CD sub light beam. As a result, the light receiving element 32a functions as a second main light beam receiving portion for laser light according to the present invention, and the light receiving elements 32b and 32c serve as the second sub main beam light receiving portion for laser light according to the present invention. It has a function.

  As described above, in the two-wavelength multi-laser 11, the photodetector 30 exists in a different position between the first photodetector 31 for DVD and the second photodetector 32 for CD. This is because the arrangement positions of the first laser light source 11a for CD and the second laser light source 11b for CD are different from each other.

  FIG. 4 shows the light-receiving part pattern of the diffractive element first-order diffracted light receiving part 36 and the relationship between the diffractive element 16 and the diffractive element first-order diffracted light receiving part 36 when the diffractive element 16 in this embodiment is adopted. Yes.

  The diffractive element first-order diffracted light receiving unit 36 of the present embodiment is configured to receive ± first-order diffracted light diffracted by the diffractive element 16 by the four light-receiving elements 36a to 36d. As a result, the light receiving elements 36a to 36d have a function as the first laser beam main sub-beam light receiving portion of the present invention.

  In the present embodiment, when detecting a tracking error signal, the DVD-RAM and CD employ the 3-beam DPP method, and the DVD-R employs the 1-beam DPP method while detecting the focus error signal. It is assumed that the DVD-RAM employs the differential astigmatism method and the DVD-R and CD employs the astigmatism method.

  The servo signal generation operation will be described with reference to FIG.

The tracking error signal and the focus error signal can be detected by the following arithmetic expression. The symbols used in the arithmetic expressions (A1 to A2, B1 to B2, C1 to C4, D1 to D
4, A1 ′ to A2 ′, B1 ′ to B2 ′, C1 ′ to C4 ′, D1 ′ to D4 ′, and I to L) are the light receiving elements 35a to 35c, the light receiving elements 32a to 32c shown in FIG. It is the light reception signal of each area | region in the light receiving elements 36a-36d. Α1 to α4 are coefficients that are optimally set to cancel the offset caused by the objective lens shift or the optical disc tilt.

DVD-RAM tracking error signal = {(A1 + B1) − (A2 + B2)} − α1 {(C1 + C4) − (C2 + C3) + (D1 + D4) − (D2 + D3)}
DVD-RAM focus error signal = {(A1 + A2) − (B1 + B2)} − α2 {(C1 + C3) − (C2 + C4) + (D1 + D3) − (D2 + D4)}
DVD-R tracking error signal = (I−J) −α3 (K−L)
DVD-R focus error signal = (A1 + A2)-(B1 + B2)
CD-R tracking error signal = {(A1 ′ + B1 ′) − (A2 ′ + B2 ′)} − α4 {(C1′−C2 ′) + (D1′−D2 ′)}
CD-R focus error signal = (A1 ′ + A2 ′) − (B1 ′ + B2 ′)
In this embodiment, since the differential astigmatism method is used to generate the focus error signal of the DVD-RAM, the light receiving elements 35b and 35c are divided into four. However, when the astigmatism method is used, You may just divide it up and down. When the differential astigmatism method is used to generate the CD focus error signal, the light receiving elements 32b and 32c may be divided into four.

  In the present embodiment, since the light receiving elements 35a to 35c of the diffraction element 0th-order diffracted light receiving unit 35 are divided into four, the DPD method is used to generate a tracking error signal when reproducing a DVD-R. Is also possible.

  Next, the one-dimensional diffraction grating 12 will be described with reference to FIG. FIG. 5 is a plan view showing a grating pattern of the one-dimensional diffraction grating 12.

As shown in FIG. 5, the one-dimensional diffraction grating 12 used in the present embodiment has a pattern formed with a constant grating pitch Λ. When assembled, the one-dimensional diffraction grating 12 has an inclination angle θ _Grating as shown in FIG. Tilted. This inclination angle θ _Grating is adjusted in order to properly irradiate the optical disc 40 with the three sub-light beams used when generating the tracking error signal.

  Next, the spot arrangement of the light beam irradiated on each optical disc 40 will be described with reference to FIGS. 6 (a), 6 (b), and 6 (c). 6A, 6B, and 6C show the spot arrangement of the light beam irradiated on each optical disc 40, and FIG. 6A shows the light beam irradiated on the DVD-R. FIG. 6B is a plan view showing the spot arrangement of the light beam irradiated onto the DVD-RAM, and FIG. 6C is a plan view showing the spot arrangement of the light beam irradiated onto the CD. It is a top view which shows spot arrangement | positioning. In the case of DVD-R, as in the case of DVD-RAM, three optical beams are irradiated onto the optical disc 40. However, since only the main optical beam 61 is used to generate the tracking error signal and the focus error signal, The sub light beam is omitted.

  As shown in FIGS. 6A, 6B, and 6C, the track pitch of the optical disc 40 is different for each optical disc 40. Each track pitch is 740 nm for DVD-R, 1230 nm for DVD-RAM, and 1600 nm for CD. is there.

  In the three-beam DPP method, as shown in FIGS. 6B and 6C, when the main light beams 71 and 81 are arranged in the center of the track, the sub light beams 72 and 82 are shifted by about ½ of the track pitch. Will be placed in the place.

  Next, the relationship with each optical component when the optical beam branched by the one-dimensional diffraction grating 12 is irradiated onto the optical disc 40 will be described with reference to FIG. FIG. 7 is a diagram showing optical components that are relevant until the laser beam is diffracted and branched by the one-dimensional diffraction grating 12 and irradiated onto the optical disc 40 and its positional relationship in the present embodiment. is there. For ease of explanation, the portion of the rising mirror is deleted, and the light beam is directly incident on the optical disc 40 as an optical recording medium via the objective lens 21. Further, FIG. 1 is a diagram rotated 90 degrees. The thin solid line in the figure indicates the optical path of the main light beam, and the dotted line indicates the optical path of the sub light beam. For convenience of explanation, members having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

When the distance between the two-wavelength multi-laser 11 and the one-dimensional diffraction grating 12 shown in FIG. 7 is s, the focal length of the collimator lens 13 is f ₁ , and the focal length of the objective lens 21 is f ₂ , the track on the optical disc 40 distance Y ₂ between the main light beam and the sub-light beam direction can be derived by the following expression. Y ₁ is the interval between the 0th-order diffracted light and the ± 1st-order diffracted light at the position of the two-wavelength multilaser 11 when it is considered that the ± 1st-order diffracted light travels to the two-wavelength multilaser side at the diffraction angle φ. . Also, the expression of the diffraction angle φ, which is the angle formed between the 0th-order diffracted light and the ± 1st-order diffracted light branched by the one-dimensional diffraction grating 12, is approximated by utilizing the extremely small diffraction angle φ. Further, λ represents the wavelength of the laser beam, and Λ represents the grating pitch of the one-dimensional diffraction grating 12.

φ = sin ⁻¹ (λ / Λ) ≈tan ⁻¹ (λ / Λ)
Y ₁ = s · tan φ = l · (λ / Λ)
Y ₂ = Y1 · (f2 / f1) = s · (λ / Λ) · (f2 / f1)
Thus, the beam interval Y ₂ between the main light beam and the sub-light beam in the track direction on the optical disk 40, the spacing s from the two-wavelength multi-laser 11 as a light source to the one-dimensional diffraction grating 12, the wavelength of the light source the ratio of the λ and the grating pitch lambda, can be derived by integrating the ratio of the focal length f ₁ of the focal length f ₂ and a collimator lens 13 of the objective lens 21. Therefore, the wavelength λ of the light source and the beam interval Y ₂ between the main light beam and the sub light beam.
It can be seen that and are in a proportional relationship.

  Next, the beam interval X between the main light beam and the sub light beam in the direction perpendicular to the track shown in FIG. 6B can be derived by the following arithmetic expression.

X = Y ₂ · tanθ _Grating
From the above formula, the beam interval X in the direction perpendicular to the track is equal to the beam interval Y _{2 in the} track direction.
And it found that a proportional relationship, as described above, from the relationship of beam spacing Y ₂ is proportional to the wavelength λ of the light source, with the wavelength λ of the light source can be seen that a proportional relationship.

In this embodiment, only one one-dimensional diffraction grating 12 is used to generate tracking error signals for DVD-RAM and CD. Therefore, it is difficult to accurately form the sub light beam at a position shifted by ½ of the track pitch in both the DVD light beam and the CD light beam. However, by utilizing the difference in the wavelength λ of the DVD light beam or the CD light beam, and adjusting the tilt angle θ _Grating of the one-dimensional diffraction grating 12 and the position in the optical axis direction, the main beam can be adjusted even at different track pitches. Three beams that generate a phase difference between the light beam and the sub light beam can be formed. In this embodiment, in the DVD-RAM, the tilt angle θ _Grating so that the phases of the main light beam and the sub light beam are different by 180 degrees.
Adjust when assembling. In this case, the phase difference between the main light beam and the sub light beam on the CD is about 165 degrees, which is a phase difference that can sufficiently generate a tracking error signal.

Since the one-dimensional diffraction grating 12 is disposed on the same optical path of the DVD light beam or the CD light beam, in the tracking error signal generation of the DVD-RAM or CD, for example, what kind of information is placed on the DVD-RAM optical disc 40 If it is known whether a spot should be formed, if only the DVD-RAM is adjusted, the other need not be adjusted. Of course, you can adjust it with CD.

  The one-dimensional diffraction grating 12 requires adjustment of the position in the optical axis direction and the rotation direction in order to form an appropriate spot on the DVD-RAM or CD optical disk 40. The working light beam only needs to pass through the one-dimensional diffraction grating 12, and does not need to pass through the center, for example. For this reason, space adjustment in a direction perpendicular to the optical axis direction is unnecessary, and it is possible to reduce man-hours for assembly adjustment and time.

  As described above, by using the one-beam DPP method for generating a DVD-R tracking error signal, it is possible to deal with a DVD-R, a DVD-RAM, or a CD only by providing one one-dimensional diffraction grating 12 in the forward path. The optical pickup device 1 can be configured. Thereby, in addition to reducing the member cost of the diffraction grating, precise space adjustment as conventionally performed is not required, and therefore, the number of assembly adjustments can be reduced and the work time can be reduced.

  Thus, in the optical pickup device 1 of the present embodiment, the optical system includes the first laser light or the second laser light emitted from the first laser light source 11a or the second laser light source 11b. Are diffracted and branched, a one-dimensional diffraction grating 12 having a constant grating pitch, and a diffraction element 16 that diffracts and branches the return light from the optical disk 40 are provided.

  By the way, in the conventional optical pickup device described in Patent Document 1, a DVD laser light source as a first laser light source or a CD laser as a second laser light source arranged in the optical path from the light source to the optical recording medium. The diffraction grating that diffracts and splits the DVD laser light or CD laser light emitted from the light source uses two types of diffraction gratings having different grating pitches so as to correspond to the DVD laser light source or the CD laser light source. It was. As a result, the two types of diffraction gratings need to be adjusted, so that there is a problem that assembly adjustment takes time.

  In the prior art described in Patent Document 1, when realizing a dual-wavelength multi-laser-mounted optical pickup compatible with a super-multi compatible optical disk drive, a DVD light beam is accurately incident on the center of a two-wavelength diffraction grating in a DVD. Therefore, it is necessary to adjust the optical axis direction of the two-wavelength diffraction grating, the direction perpendicular to the dividing direction of the diffraction grating, and the rotation direction of the diffraction grating, and very precise positioning accuracy is required. It was a factor that hindered shortening.

  In contrast, in the present embodiment, the laser beam emitted from the first laser light source 11a or the second laser light source 11b is diffracted and branched in the optical path from the two-wavelength multi-laser 11 to the optical disk 40. Since there is only one type of diffraction grating to be used, that is, the one-dimensional diffraction grating 12, only one of the first laser light and the second laser light of the first laser light source 11a or the second laser light source 11b is used. The assembly adjustment of the one-dimensional diffraction grating 12 may be adjusted. For this reason, it does not take time and effort to assemble and adjust as compared with the prior art.

  Here, in the present embodiment, the first laser light or the second laser light emitted from the first laser light source 11 a or the second laser light source 11 b is branched into three beams by the one-dimensional diffraction grating 12. Then, the light is condensed on the optical disk 40, and the return light from the optical disk 40 is diffracted by the diffraction element 16.

  Then, the first light detection unit 31 detects the light beam intensity of the first laser light emitted from the first laser light source 11 a and branched by the one-dimensional diffraction grating 12. More specifically, the 0th-order diffracted light receiving unit 35 receives 0th-order diffracted light from the one-dimensional diffraction grating 12 and 0th-order diffracted light from the diffraction element 16 in ± 1st-order diffracted light, while receiving the first-order diffracted light from the diffractive element. The unit 36 receives ± first-order diffracted light from the diffraction element 16 in the zero-order diffracted light of the one-dimensional diffraction grating 12.

  As a result, the 0th-order diffracted light receiving unit 35 receives the 0th-order diffracted light from the first laser light source 11a and the 0th-order diffracted light from the diffraction element 16 in the ± 1st-order diffracted light. Thus, the control unit 10 can perform tracking control by the 3-beam DPP method in, for example, a DVD-RAM.

  The second light detection unit 32 detects the light beam intensity of the second laser light emitted from the second laser light source 11 b and branched by the one-dimensional diffraction grating 12. As a result, the second light detection unit 32 receives the 0th-order diffracted light from the diffraction element 16 and the 0th-order diffracted light of the one-dimensional diffraction grating 12 from the second laser light source 11b and ± 1st-order diffracted light, respectively. The control unit 10 can perform tracking control using, for example, a three-beam DPP method for a CD.

  On the other hand, when the control unit 10 performs tracking control by the 1-beam DPP method, for example, the first laser light emitted from the first laser light source 11 a is only the 0th-order diffracted light by the one-dimensional diffraction grating 12. The return light from the optical disk 40 is condensed by the one beam and diffracted by the diffraction element 16, but in this embodiment, only ± first-order diffracted light from the diffraction element 16 in the diffraction element 16 is used. Light can be received by the diffraction element first-order diffracted light receiving unit 36.

  Accordingly, the first-order diffracted light receiving unit 36 of the diffractive element receives ± first-order diffracted light from the diffractive element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12 from the first laser light source 11a. In R, tracking control can be performed by the one-beam DPP method.

  Thus, in this embodiment, for example, a 1-beam DPP method that uses only the 0th-order diffracted light of the one-dimensional diffraction grating 12 out of the returned light from the optical disc 40 is used to generate a tracking error signal of DVD-R. By doing so, the optical pickup device 1 equipped with the two-wavelength multi-laser 11 can be configured to use only one diffraction grating in the optical path from the two-wavelength multi-laser 11 to the optical disc 40. As a result, it is possible to perform recording / reproduction on a plurality of types of optical disks 40 only by performing assembly adjustment of the diffraction grating with either the first laser light source 11a or the second laser light source 11b, and also in the optical axis direction. Therefore, it is possible to provide the optical pickup device 1 that can reduce the number of steps in the assembly adjustment process and shorten the adjustment time.

  Therefore, by using only one one-dimensional diffraction grating 12 having a constant grating pitch in the optical path from the two-wavelength multi-laser 11 to the optical disk 40, it is possible to reduce the man-hours for the assembly adjustment process and the adjustment time. An optical pickup device 1 to be obtained can be provided.

  In the optical pickup device 1 of the present embodiment, the first laser light source 11a is a DVD laser light source that emits a laser beam for DVD, and the second laser light source 11b is a laser beam for CD. The light source is a CD laser light source that emits light. The first light detector 31 is a DVD light receiver that receives the DVD laser light emitted from the DVD laser light source. The second light detector 32 is a CD light source. This is a CD light receiving unit that receives the CD laser light emitted from the laser light source.

  Thus, when the optical disc 40 is a DVD or a CD, the assembly adjustment step is performed by using only one one-dimensional diffraction grating 12 having a constant grating pitch in the optical path from the two-wavelength multi-laser 11 to the optical disc 40. Thus, it is possible to provide the optical pickup device 1 that can reduce the number of steps and the adjustment time.

  Further, in the optical pickup device 1 of the present embodiment, the control unit 10 determines the ± first-order diffracted light and the zero-order diffracted light branched by the one-dimensional diffraction grating 12 when the optical disc 40 is a DVD-RAM or CD. On the other hand, when the optical disc 40 is a DVD-R, the tracking control is performed using the ± 1st order diffracted light from the diffraction element 16 in the 0th order diffracted light of the one-dimensional diffraction grating 12.

  Thus, when the optical disc 40 is a DVD-RAM or CD, tracking control is performed by the three-beam DPP method using the zero-order diffracted light of the one-dimensional diffraction grating 12 and the ± first-order diffracted light of the one-dimensional diffraction grating 12. It can be carried out.

  When the optical disk 40 is a DVD-R, tracking control can be performed by the 1-beam DPP method using the 0th-order diffracted light of the one-dimensional diffraction grating 12 and the ± 1st-order diffracted light of the diffraction element 16.

  Further, in the optical pickup device 1 of the present embodiment, the diffractive element 16 diffracts the return light from the optical disc 40 in different directions for each designated pattern region. Thereby, each light reception area | region of the diffraction element 1st order diffracted light light-receiving part 36 in the 1st light detection part 31 can be arrange | positioned in a desired position.

  Further, in the optical pickup device 1 of the present embodiment, the first light detection unit 31 includes the diffraction element 0th-order diffracted light receiving unit 35, the 0th-order diffracted light from the diffraction element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12. A first laser beam main light beam receiving portion for receiving the first laser beam and a first laser beam sub beam for receiving the 0th-order diffracted light from the diffraction element 16 in the ± 1st-order diffracted light of the one-dimensional diffraction grating 12 The diffractive element first-order diffracted light receiver 36 receives ± first-order diffracted light from the diffractive element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12 4. It comprises light receiving elements 36a to 36d as first laser beam main sub-beam light receiving portions.

  The second light detection unit 32 receives the second main light beam for laser light that receives the 0th-order diffracted light from the diffraction element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12 from the second laser light source 11b. A second laser beam sub-main beam receiving unit that receives 0th-order diffracted light from the diffraction element 16 in ± 1st-order diffracted light of the one-dimensional diffraction grating 12 from the second laser light source 11b. Light receiving elements 32b and 32c.

  Thus, when tracking control is performed by the three-beam DPP method when the optical disk 40 is a DVD-RAM, the 0th-order diffracted light from the diffraction element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12 is the first light detection unit 31. On the other hand, the 0th-order diffracted light from the diffraction element 16 in the ± 1st-order diffracted light of the one-dimensional diffraction grating 12 is received by the light-receiving element 35a of the diffractive element 0th-order diffracted light receiver 35 in FIG. Light is received by the light receiving elements 35b and 35c of the element 0th-order diffracted light receiving unit 35.

Further, when tracking control is performed by the three-beam DPP method when the optical disk 40 is a CD, the 0th-order diffracted light from the diffractive element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12 is the light receiving element in the second light detection unit 32. While the light is received at 32a, ± 1 of the one-dimensional diffraction grating 12
The 0th-order diffracted light from the diffraction element 16 in the next-order diffracted light is received by the light receiving elements 32b and 32c.

  On the other hand, when tracking control is performed by the 1-beam DPP method when the optical disk 40 is a DVD-R, the ± 1st-order diffracted light from the diffraction element 16 in the 0th-order diffracted light of the one-dimensional diffraction grating 12 is the first light detection unit 31. Are received by the four light receiving elements 36a to 36d serving as the first laser beam main sub-beam light receiving parts.

  Thereby, when tracking control of DVD-RAM, CD, or DVD-R is performed by the 3-beam DPP method or the 1-beam DPP method, a specific light receiving unit is specified.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. Configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  In the present embodiment, an optical pickup device 2 compatible with a super-multi compatible optical disc drive capable of recording / reproducing an optical disc 40 as an optical recording medium including a BD (Blu-ray disc) will be described with reference to FIG. FIG. 8 is a configuration diagram showing the optical pickup device 2 of the present embodiment.

  As shown in FIG. 8, the optical pickup device 2 of the present embodiment includes a BD third laser light source 51 as a BD laser light source, and a third laser light emitted from the third laser light source 51. An optical coupling element 52 as an optical coupling means for bending the optical disk 40 in the direction of the optical disk 40, a driving unit 53 configured to include a stepping motor or a piezoelectric element and driving the collimator lens 13, and a BD rising mirror (not shown) A BD objective lens 22 for condensing the third laser beam on the optical disc 40, and a BD diffractive element first-order diffracted light receiving portion 37 for receiving the return light from the optical disc 40 and generating a tracking error signal. This is different from the first embodiment.

  In the optical pickup device 2 of the present embodiment, as shown in FIG. 8, the third laser light emitted from the third laser light source 51 enters the optical coupling element 52 with a certain spread angle, It is bent in the direction of the optical disc 40. Then, the light is collimated by the collimator lens 13 and condensed on the optical disk 40 through the light separation element 14, a rising mirror (not shown), and the BD objective lens 22.

  The return light reflected by the optical disk 40 passes through the BD objective lens 22 and a rising mirror (not shown), is bent by the light separation element 14, passes through the detection lens 15, and enters the diffraction element 16. The return light diffracted and branched by the diffraction element 16 is received by the diffraction element zero-order diffracted light receiving part 35 and a BD diffraction element first-order diffracted light receiving part 37 described later in the first photodetector 31 ′. The

  Next, the photodetector 30 ′ will be described in detail with reference to FIGS. 9 and 10. FIG. 9 is an explanatory diagram showing the configuration of the photodetector 30 '. FIG. 10 shows the light receiving pattern of the BD diffractive element first-order diffracted light receiving unit 37 and the diffractive element 16 and the BD diffractive element first-order diffracted light receiving unit 37 when the diffractive element 16 in the present embodiment is employed. Indicates a pending relationship.

In the present embodiment, as shown in FIG. 9, the first light detector 31 ′ receives the three light beams that have passed through the diffractive element 16 as the 0th order diffracted light by the respective light receiving elements. The folded light receiving unit 35, the diffraction element first-order diffracted light receiving unit 36 that receives ± first-order diffracted light of the DVD light diffracted by the diffraction element 16, and the light-receiving element receives ± first-order diffracted light of BD light. And a first-order diffracted light receiving portion 37 for BD receiving light.

  Further, in the present embodiment, as shown in FIG. 10, the BD diffractive element first-order diffracted light receiving unit 37 is ± 1 next time diffracted by the diffractive element 16 similarly to the diffractive element first-order diffracted light receiving unit 36. The folded light is configured to be received by the light receiving elements 37a to 37d as four BD sub-beam light receiving portions. In the present embodiment, it is assumed that the astigmatism method is used for generating the BD focus error signal, and the one-beam DPP method is used for generating the tracking error signal.

  Next, a servo signal generation operation at the time of recording / reproducing on the BD will be described with reference to FIG. First, the tracking error signal and the focus error signal are detected by the following arithmetic expression. Symbols (A1 to A2, B1 to B2, I 'to L') used in the arithmetic expressions are light reception signals in the respective regions in the light receiving elements 37a to 37d shown in FIG. Α5 is a coefficient that is optimally set to cancel an offset caused by objective lens shift or optical disc tilt.

BD tracking error signal = (I′−J ′) − α5 (K′−L ′)
DVD-R focus error signal = (A1 + A2)-(B1 + B2)
In this embodiment, it is possible to use the DPD method instead of the one-beam DPP method when reproducing the BD.

  Moreover, although the pattern which divided the area | region of the diffraction element 16 into 6 in FIG. 10 is shown, the structure of a pattern is not limited to this. For example, as shown in FIG. 11, a diffractive element 16 'having a pattern in which a gap portion is provided in the central region may be used.

  In the optical pickup device 2 equipped with the two-wavelength multi-laser 11 described above, the same one-beam DPP method as that for the BD is used for generating a DVD-R tracking error signal. Application to BD is also possible simply by adding these parts.

  As described above, in the optical pickup device 2 of the present embodiment, the third laser light source 51 that emits the BD laser light different from the first laser light source 11a and the second laser light source 11b, and the one-dimensional The BD laser beam emitted from the third laser light source 51 is arranged between the diffraction grating 12 and the optical disc 40, and is bent in the direction of the optical disc 40, and passes through the first laser beam or the second laser beam. The first light detection unit 31 receives ± first-order diffracted light from the diffraction element 16 in the return light from the optical disk 40 in the BD laser light. The light receiving elements 37a to 37d are provided, and the control unit 10 performs tracking control by the three-beam DPP method when the optical disc 40 is a BD.

  As a result, even when a BD is added as the optical disc 40, the optical coupling element 52 is added, and the four light receiving elements 37a to 37d are added to the first light detection unit 31, whereby one beam of BD is added. Tracking control can be performed by the DPP method.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of the present invention.

  The present invention can be applied to an optical pickup device used for reproducing or recording an optical disc such as a CD (compact disc), a DVD (digital versatile disc), and a BD (Blu-ray disc).

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2 Optical pick-up apparatus 10 Control part 11 Two wavelength multi laser (light source)
11a First laser light source 11b Second laser light source 12 Diffraction grating 13 Collimator lens 14 Light separation element 15 Detection lens 16 Diffraction element 20 Lens holder 21 Objective lens 22 BD objective lens 30 Photodetector 30 'Photodetector 31 1 light detector 31 '1st light detector 32 2nd light detector 32a Light receiving element (second main main beam light receiving portion for laser light)
32b / 32c light receiving element (second laser beam sub-main beam light receiving section)
35 Diffraction element 0th-order diffracted light receiving portion 35a Light receiving element (first main main beam receiving portion for laser light)
35b / 35c light receiving element (first laser beam sub-main beam receiving unit)
36 Diffraction element first-order diffracted light receiving parts 36a to 36d Light receiving element (first laser beam main sub-beam light receiving part)
37 BD Diffraction Element First Order Diffracted Light Receiving Units 37a to 37d Light Receiving Element (BD Sub-beam Receiving Unit)
40 Optical disc (optical recording medium)
51 Third Laser Light Source (BD Laser Light Source)
52 Optical coupling element (optical coupling means)
53 Drive unit Y ₂ interval X beam interval s interval Λ grating pitch λ wavelength φ diffraction angle θ _Grating inclination angle

Claims (6)

A first laser light source that emits a first laser beam;
A second laser light source that emits a second laser light having a wavelength different from that of the first laser light source;
A photodetector that receives each of the first laser light or the second laser light emitted from the first laser light source or the second laser light source and converts it into an electrical signal corresponding to the intensity of the light beam;
The first laser light or the second laser light emitted from the first laser light source or the second laser light source is guided to the optical recording medium, and the return light from the optical recording medium is sent to the photodetector. A guiding optical system;
A control unit that generates a focus error signal and a tracking error signal from return light from the optical recording medium, and performs focus control and tracking control;
The optical system is a one-dimensional diffraction grating having a constant grating pitch that diffracts and branches the first laser light or the second laser light emitted from the first laser light source or the second laser light source. And a diffraction element that diffracts and branches the return light from the optical recording medium,
The light detector includes: a first light detection unit that detects a light beam intensity of the first laser light emitted from the first laser light source and branched by the one-dimensional diffraction grating; A second light detection unit that detects each light beam intensity of the second laser light emitted from the second laser light source and branched by the one-dimensional diffraction grating,
The first light detection unit includes a diffractive element zero-order diffracted light receiving unit that receives zero-order diffracted light from the diffractive element, and a diffractive element first-order diffracted light receiving unit that receives ± first-order diffracted light from the diffractive element. An optical pickup device configured to be configured. The first laser light source is a DVD laser light source that emits a laser beam for DVD,
The second laser light source is a CD laser light source that emits a laser beam for CD,
The first light detection unit is a DVD light receiving unit that receives the DVD laser light emitted from the DVD laser light source,
2. The optical pickup device according to claim 1, wherein the second light detection unit is a CD light receiving unit that receives the CD laser light emitted from the CD laser light source. The controller is
When the optical recording medium is a DVD-RAM or CD, tracking control is performed using ± first-order diffracted light and zero-order diffracted light branched by the one-dimensional diffraction grating,
3. The optical pickup device according to claim 2, wherein when the optical recording medium is a DVD-R, tracking control is performed using ± first-order diffracted light from a diffraction element in zero-order diffracted light of the one-dimensional diffraction grating. . The diffraction element is
4. The optical pickup device according to claim 1, wherein the return light from the optical recording medium is diffracted in different directions for each designated pattern region. The first light detection unit includes:
The diffractive element zero-order diffracted light receiving unit receives a first main beam receiving unit for laser light that receives zero-order diffracted light from the diffractive element in the zero-order diffracted light of the one-dimensional diffractive grating, and ± 1 of the one-dimensional diffractive grating. The first diffracted light receiving portion receives a zeroth-order diffracted light from the diffracting element in the first-order diffracted light, and the diffractive element first-order diffracted light receiving portion is diffracted in the zeroth-order diffracted light of the one-dimensional diffraction grating. It is composed of four first laser beam main sub-beam light receiving portions for receiving ± first-order diffracted light from the element,
The second light detection unit includes:
A main main beam receiving unit for second laser light that receives zero-order diffracted light from a diffraction element in zero-order diffracted light of a one-dimensional diffraction grating from the second laser light source, and one-dimensional from the second laser light source. 5. The sub-main beam light receiving portion for second laser light that receives 0th-order diffracted light from the diffraction element in ± 1st-order diffracted light of the diffraction grating, according to any one of claims 1 to 4. The optical pickup device described. A BD laser light source that emits a BD laser light different from the first laser light source and the second laser light source;
A BD laser beam emitted between the one-dimensional diffraction grating and the optical recording medium and emitted from the BD laser light source is bent in the direction of the optical recording medium, and the first laser beam or the second laser beam An optical coupling means for allowing the laser beam to pass therethrough,
The first light detection unit is provided with four BD sub-beam light receiving units that receive ± first-order diffracted light from the diffraction element in the return light from the optical recording medium in the BD laser light,
6. The optical pickup device according to claim 1, wherein the control unit performs tracking control by a one-beam DPP method when the optical recording medium is a BD.

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