JP2008041184A - Optical pickup device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device and an optical disk device, wherein linearlity of a focus error signal is high, even for an optical disk having a plurality of layers of information recording surfaces. <P>SOLUTION: This optical pickup device is provided with a laser light source 1, a hologram 3, having a focus region 23 and tracking region 24, an objective lens 6, and a photodetector 4 having focus and tracking photodetection parts 4a and 4b, respectively. In the hologram 3, the inside of the boundary virtual line 20 of a predetermined shape smaller than the outer periphery of the hologram 3 with O as the center of the hologram is set as a focus region 23, and the outside of the boundary virtual line 20 is set as a tracking region 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup device and an optical disk device mounted on electronic equipment such as a notebook personal computer and other computers.

  Conventionally, the optical disk technology has continued to advance from CD to DVD, to Blu-ray DISC and HD-DVD, which are referred to as next-generation DVD, to high recording density and high capacity. Among them, a technique has been developed in which a single optical disc has a plurality of information recording surfaces, and information is recorded and reproduced on each information recording surface.

  FIG. 20 is a configuration diagram of an optical system of a conventional optical pickup device. The optical pickup device can record and reproduce information on a plurality of information recording surfaces. The laser light source 501 emits laser light toward an optical disk 507 having a plurality of information recording surfaces 507a and 507b. The reflection mirror 502 bends the optical path of the laser light emitted from the laser light source 501 to reduce the size of the optical pickup device. The collimating lens 503 changes the laser light emitted from the laser light source 501 that is diverging light into substantially parallel light. The rising mirror 504 bends the optical path of the laser light emitted from the laser light source 501 that is substantially parallel to the optical disk 507 at a substantially right angle with respect to the optical disk 507. The hologram element 505 includes a hologram 505a and a quarter wavelength plate 505b, and is fixed to the lens holder together with the objective lens 506. The quarter-wave plate 505 b converts the laser light emitted from the laser light source 501 that is P-polarized light into circularly polarized light, and converts the laser light reflected by the optical disk 507 from circularly-polarized light into S-polarized light. The hologram 505a passes the P-polarized laser beam as it is, and diffracts the S-polarized laser beam. The hologram 505a separates the incident light into light used for focus control and light used for tracking control, depending on where it has passed through the hologram 505a. The objective lens 506 is a lens that converges the laser light emitted from the laser light source 501 on the information recording surfaces 507a and 507b of the optical disk 507. The optical disc 507 has an information recording surface 507a on the front side and an information recording surface 507b on the back side. The light receiver 508 includes a light detection unit, receives the laser light emitted from the laser light source 501, reflected by the optical disk 507, and passed through the hologram 505 a, converts it into an electrical signal, and outputs it. The front light monitor 509 receives a part of the laser light emitted from the laser light source 501 and converts it into an electrical signal for output. The output signal is used for output control of laser light emitted from the laser light source 501.

  FIG. 21 is a diagram showing the relationship between a conventional hologram and a light receiver. The hologram 505a is divided into focus areas 505c and 505d and a tracking area 505e. The focus areas 505c and 505d allow a laser beam used for focus control to pass therethrough. The tracking region 505e allows a laser beam used for tracking control to pass through. The focus areas 505c and 505d are in-focused spots 511 and 512 of light incident on the light receiver 508 before being in focus with the areas that generate the spots 510 and 513 of light incident on the light receiver 508, respectively. And a region for generating The light receiver 508 includes focus light detection units 508a and 508b. Light incident on the focus light detectors 508a and 508b is converted into an electric signal used for focus control in the light receiver 508 and output. The focus light detection unit 508a and the focus light detection unit 508b are alternately arranged in a direction corresponding to the track longitudinal direction of the optical disc 507. When information is recorded on or reproduced from the optical disc 507, the laser light emitted from the laser light source 501 is condensed and reflected on a predetermined information recording surface 507a or information recording surface 507b of the optical disc 507. The laser light that has passed through the focus region 505c of the hologram 505a enters the focus light detection units 508a and 508b of the light receiver 508 as spots 510 and 511. The laser light that has passed through the focus region 505d is incident on the focus light detection units 508a and 508b of the light receiver 508 as spots 512 and 513. When the output from the focus light detection unit 508a is IG and the output from the focus light detection unit 508b is IH, the focus error signal FES used for focus control is expressed by FES = IH-IG. The focus error signal FES is a signal representing the defocus of the light beam condensed on the information recording surfaces 507a and 507b of the optical disc 507.

  FIG. 22 is a diagram showing a conventional focus error signal FES by an optical disc having a two-layer information recording surface. When the objective lens 506 is far from the optical disc 507, the focus error signal FES is almost 0, but when the objective lens 506 approaches the optical disc 507, it swings in the negative direction. The focus error signal FES suddenly changes from negative to positive near the focal point of the information recording surface 507a on the near side. Further, as it approaches the optical disk 507, it swings from positive to negative through negative. Then, the focus error signal FES suddenly changes from negative to positive again near the focal point of the information recording surface 507b on the back side. When the optical disk 507 is further approached, the focus error signal FES returns to almost zero. The focus error signal FES obtained in this way is adjusted by moving the objective lens 506 so that it is maintained at almost 0 or a predetermined value within the use area of the information recording surface 507a on the front side and the information recording surface 507b on the back side. It can keep in focus.

A hologram for performing good recording and reproduction on an optical disc having a plurality of information recording surfaces as described above is also described in (Patent Document 1).
JP 2005-339697 A

  However, in an optical disc having a two-layer information recording surface, the focus error signal FES deviates from an ideal curve indicated by a dotted line in FIG. That is, the dotted line changes from negative to positive with almost linearity, whereas the solid line has broken linearity. Therefore, it is difficult to perform accurate focus control.

  The present invention solves the above-described problems and provides an optical pickup device and an optical disc apparatus that ensure the linearity of the focus error signal FES and have excellent recording and reproduction characteristics even for an optical disc having a plurality of information recording surfaces. The purpose is to do.

  In order to achieve the above object, the present invention provides a laser light source that emits light for irradiating an optical disc, a focus area that separates reflected light from the optical disc into focus control light, and tracking that separates into tracking control light. A hologram having a region, an objective lens that passes reflected light from the optical disc toward the hologram, a focus light detection unit that receives light separated in the focus region, and light separated in the tracking region A light receiving device having a tracking light detection unit for receiving light, wherein the hologram has a focus imaginary line inside a boundary imaginary line having a predetermined shape smaller than the outer periphery of the hologram centered on the hologram. An optical pin characterized in that the tracking region is outside the virtual boundary line of the shape. It was up equipment.

  The distance from the surface of the optical disc having a plurality of information recording surfaces to each information recording surface is different from the distance from the surface of the optical disc having a single layer information recording surface to the information recording surface. For this reason, laser light reflected by any information recording surface of an optical disc having a plurality of information recording surfaces is affected by spherical aberration. For this reason, the linearity of the focus error signal FES is lost. The influence of spherical aberration has the property that the vicinity of the optical axis is the smallest and the greater the distance to the periphery. Therefore, the focus area is arranged so that the tracking area occupies the periphery of the hologram so that light having a large influence of spherical aberration does not pass through the focus area.

  In the optical pickup device of the present invention, only the light having a small influence of the spherical aberration passes through the focus region, so that the linearity of the focus error signal FES is good. Therefore, the optical pickup device of the present invention can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc.

  According to the first aspect of the present invention, a laser light source that emits light for irradiating an optical disk, a focus area that separates reflected light from the optical disk into light for focus control, and a tracking area that separates light for tracking control , A objective lens that passes reflected light from the optical disk toward the hologram, a focus light detection unit that receives light separated in the focus region, and a tracking light detection unit that receives light separated in the tracking region The hologram has a focus area that is inside the boundary virtual line having a predetermined shape smaller than the outer periphery of the hologram centered on the center of the hologram, and a tracking area that is outside the boundary virtual line having the predetermined shape. This is an optical pickup device.

  Since only light having a small influence of spherical aberration passes through the focus region, the linearity of the focus error signal FES is good. Therefore, the optical pickup device of the present invention can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc.

  A second aspect of the present invention is the optical pickup device according to the first aspect of the invention, wherein the boundary virtual line having a predetermined shape is a circular shape.

  Only light that is as small as the influence of spherical aberration passes through the focus area. Therefore, the linearity of the focus error signal FES can be improved most efficiently.

  According to a third aspect of the present invention, in the first aspect of the present invention, a predetermined boundary delimited by a boundary virtual line having a predetermined shape and a boundary virtual line corresponding to the track longitudinal direction of the optical disc in the inner region of the boundary virtual line having the predetermined shape. The assigned area is an optical pickup device used as a tracking area.

  An area suitable for tracking control among the areas inside the boundary virtual line having a predetermined shape can be used as the tracking area, and the area distribution in the hologram can be optimized.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the predetermined concession area is an area defined by a boundary virtual line having a predetermined shape and at least one boundary virtual line corresponding to the track longitudinal direction of the optical disc. It is a pickup device.

  A region having a large change amount with respect to the track deviation can be set as a tracking region, and the sensitivity of tracking control can be increased.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the predetermined concession area used as the tracking area is an optical pickup device that separates reflected light from the optical disc into light mainly used for tracking control.

  The sensitivity of tracking control can be increased by mainly using light separated in a region where the amount of change with respect to the track deviation is large for tracking control.

  According to a sixth aspect of the present invention, in the third aspect of the present invention, the predetermined assigned region is a center of the hologram divided by a boundary virtual line having a predetermined shape and at least two boundary virtual lines corresponding to the track longitudinal direction of the optical disk. The optical pickup device is a region including

  The amount of reflected light from the information recording surface other than the predetermined information recording surface on which recording or reproduction is performed by irradiation with laser light from the laser light source can be reduced. Therefore, the value of the focus error signal FES in the area far from the optical disk or the area close to the optical disk can be stably set to a value close to 0.

  A seventh aspect of the invention is an optical pickup device according to the sixth aspect of the invention, wherein the predetermined concession area used as the tracking area separates the reflected light from the optical disc into light used as an auxiliary for tracking control.

  Tracking light can be stably performed by using the light separated in the region where the amount of change is not large with respect to the track deviation as an auxiliary to the tracking control.

  The invention according to claim 8 is the invention according to claim 7, wherein the focus area is divided into at least two areas, and the at least two areas are substantially lines with the center line of the hologram corresponding to the track longitudinal direction of the optical disc as an axis of symmetry. This is an optical pickup device arranged symmetrically.

  Even if there is a scratch or the like on the optical disk, it is possible to capture the information about the focus shift while avoiding the area. Therefore, it is resistant to scratches on the optical disk surface. Further, the areas from the first quadrant to the fourth quadrant of the focus area of the hologram are substantially equal. Therefore, it is possible to generate the focus error signal FES by taking in information regarding the focus shift without deviation from the first quadrant to the fourth quadrant.

  According to a ninth aspect of the present invention, in the first aspect of the present invention, the focus region includes a first focus region that separates light that is focused before entering the focus light detection unit, and a focus light detection unit before focusing. An optical pickup device having a second focus region for separating incident light.

  Focus control by the spot size method can be performed.

  According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the focus area is divided into a plurality of first focus areas and a plurality of second focus areas by boundary virtual lines corresponding to the track longitudinal direction of the optical disc, and The one tracking area and the second focus area are optical pickup devices that are alternately arranged with a boundary virtual line of the center line corresponding to the track crossing direction orthogonal to the track longitudinal direction.

  The position on the light receiver of the light separated by the first focus area and the second focus area corresponding to the center line is unlikely to fluctuate in the track longitudinal direction.

  According to an eleventh aspect of the present invention, in the tenth aspect of the present invention, the focus light detection section is composed of a first focus light detection section and a second focus light detection section that are alternately arranged corresponding to the track longitudinal direction. Device.

  Since the position on the light receiver corresponding to the center line of the light separated in the focus area is unlikely to change in the track longitudinal direction, the light corresponding to the center line is the first focus light detection unit or the second focus. It is difficult to protrude from the light detection unit.

  According to a twelfth aspect of the present invention, in the ninth aspect of the present invention, the focus area is a boundary virtual line corresponding to a track crossing direction orthogonal to the track longitudinal direction of the optical disc, and includes a plurality of first focus areas and a plurality of second focus areas. The first tracking region and the second focus region are optical pickup devices that are alternately arranged with a virtual imaginary line at the center line corresponding to the track longitudinal direction.

  The position on the light receiver of the light separated by the first focus region and the second focus region corresponding to the center line is unlikely to fluctuate in the track crossing direction orthogonal to the track longitudinal direction.

  According to a thirteenth aspect of the present invention, in the twelfth aspect of the invention, the focus light detection unit includes a first focus light detection unit and a second focus light detection unit that are alternately arranged corresponding to the track crossing direction orthogonal to the track longitudinal direction. This is an optical pickup device constituted by:

  Of the light separated in the focus area, the position of the light corresponding to the center line on the light receiver hardly fluctuates in the track crossing direction orthogonal to the track longitudinal direction, so the light corresponding to the center line is the first focus light. It is difficult to protrude from the detection unit or the second focus light detection unit.

  According to a fourteenth aspect of the present invention, in the first aspect of the invention, the tracking region existing outside the boundary virtual line having a predetermined shape is a first tracking region that separates the reflected light from the optical disc into light mainly used for tracking control. This is an optical pickup device having a second tracking region that separates reflected light from the optical disc into light that is used as an auxiliary for tracking control.

  Tracking control using mainly the light separated in the first tracking region and the light separated in the second tracking region as an auxiliary can be performed.

  According to a fifteenth aspect of the invention, in the fourteenth aspect of the invention, the tracking area existing outside the boundary imaginary line having a predetermined shape is divided into an end area and a center area along the track longitudinal direction of the optical disc. The region is an optical pickup device that is used as a first tracking region and the central region is used as a second tracking region.

  A tracking error signal TES is obtained mainly using the first tracking area having a large amount of information regarding track deviation and using the second tracking area having a small amount of information as an auxiliary.

  According to a sixteenth aspect of the invention, there is provided the optical pickup according to the fifteenth aspect, wherein the first tracking region and the second tracking region are arranged substantially symmetrically about the center line corresponding to the track longitudinal direction of the optical disk of the hologram. Device.

  Since the same effect can be obtained regardless of whether the deviation from the track is left or right, the focused spot can be stably placed at the center of the track.

  The invention of claim 17 is the invention of claim 1, wherein the light source includes a light source that emits two laser beams having different wavelengths, and the hologram includes two holograms respectively corresponding to the two laser beams having different wavelengths. The two holograms are an optical pickup device that is integrated with each other.

  Since the hologram is not shared by the two laser beams having different wavelengths but is provided separately, the degree of freedom in design increases.

  According to an eighteenth aspect of the invention, there is provided the optical pickup apparatus according to the seventeenth aspect of the invention, wherein the two integrated holograms are attached to the lens holder of the objective lens.

  Since the objective lens and the hologram do not shift in position, the light that has passed through the objective lens enters the hologram without causing a positional shift. Therefore, even if the objective lens is deviated from the track, the information on the deviation is reflected in the light incident on the hologram, so that tracking control can be performed correctly.

  According to a nineteenth aspect of the present invention, there is provided a hologram having a laser light source that emits light for irradiating an optical disk, a focus area that separates reflected light from the optical disk into light for focus control, and a tracking area that separates light for tracking control. And an objective lens that passes reflected light from the optical disk toward the hologram, a focus light detection unit that receives light separated in the focus region, and a tracking light detection unit that receives light separated in the tracking region A hologram, wherein the inside of a boundary virtual line having a predetermined shape smaller than the outer periphery of the hologram centering on the center of the hologram is set as a focus area and the outside of the boundary virtual line having a predetermined shape is set as a tracking area. This is an optical disc device.

  Since only light having a small influence of spherical aberration passes through the focus region, the linearity of the focus error signal FES is good. Therefore, the optical disc apparatus of the present invention can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc.

(Embodiment 1)
The first embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating a main configuration of the optical pickup device according to the first embodiment. The laser light emitted from the laser light source 1 is collected by the objective lens 6, enters the optical disc 2, is reflected by the optical disc 2, and passes through the objective lens 6 again. The laser light further enters the hologram 3. The hologram 3 has an inner region 21 and an outer region 22 of a boundary virtual line 20 having a predetermined shape smaller than the outer periphery of the hologram 3 around the center O of the hologram 3. In the hologram 3, the inner area 21 of the boundary virtual line 20 having a predetermined shape is used as a focus area 23 and the outer area 22 is used as a tracking area 24. In the first embodiment, the boundary virtual line 20 having a predetermined shape is circular. The laser light is separated by the hologram 3, and the light that has passed through the focus region 23 enters the focus light detection unit 4 a of the light receiver 4. The light that has passed through the tracking region 24 enters the tracking light detector 4b of the light receiver 4. The light incident on the focus light detection unit 4a is used for focus control. The light incident on the tracking light detector 4b is used for tracking control.

  The optical disc 2 is a DVD having a two-layer information recording surface in the first embodiment. However, even if the optical disc 2 has a multiple-layer information recording surface of a Blu-ray Disc or HD-DVD called a next-generation DVD. good. Further, it may be an optical disc having other plural layers of information recording surfaces.

  Normally, a DVD having a single-layer information recording surface has a distance from the surface to the information recording surface of approximately 0.6 mm. In a DVD having a two-layer information recording surface, the distance from the front surface to the front information recording surface 2a is about 0.5725 mm, and the distance to the back information recording surface 2b is about 0.6275 mm. That is, the information recording surface 2a on the near side and the information recording surface 2b on the far side are separated by about 0.055 mm.

  The laser light source 1 emits a laser beam having a wavelength of about 650 nm for DVD in the first embodiment. If it is a laser light source for the next-generation DVD, it will emit laser light having a wavelength of about 405 nm. The laser light source 1 is selected according to the optical disk 2.

  FIG. 2 is a diagram showing the configuration of the hologram according to the first embodiment. The hologram 3 is an aggregate of diffraction gratings that occupy each region. The light that has passed through each region of the hologram 3 is diffracted according to the wavelength of the light passing through the diffraction grating, the refractive index of the diffraction grating, the grating depth, the grating spacing, the grating direction, and the like. Incident on the part. The hologram 3 includes a reflection type and a transmission type. The hologram 3 according to the first embodiment is a transmission type, but it can be expressed as “passes” because it can be essentially used. The boundary line of each region is a boundary virtual line and is called a dividing line. Each area is separated by a boundary virtual line. In FIG. 2, the left-right direction on the paper surface is the direction corresponding to the track longitudinal direction. The track longitudinal direction is the direction in which marks on the optical disk 2 are arranged. When the spot on the optical disc 2 is reflected and projected onto the hologram 3, the direction corresponding to the track longitudinal direction in the spot on the optical disc 2 is the direction corresponding to the track longitudinal direction of the hologram 3. The direction perpendicular to the track longitudinal direction on the optical disc 2 is the track crossing direction. The direction corresponding to the track crossing direction on the optical disc 2 is the direction corresponding to the track crossing direction of the hologram 3.

  The hologram 3 has an inner region 21 and an outer region 22 of a boundary virtual line 20 having a predetermined shape smaller than the outer periphery of the hologram 3 centered on the center O of the hologram 3. In the hologram 3, the inner area 21 of the boundary virtual line 20 having a predetermined shape is used as a focus area 23 and the outer area 22 is used as a tracking area 24. As will be described later, the light reflected by the optical disc 2 having a plurality of information recording surfaces and passed through the objective lens 6 is more influenced by spherical aberration toward the outer peripheral portion. When the light having a large influence of the spherical aberration is separated into the focus control light in the focus area 23, the linearity of the focus error signal FES is lost in the use area. By setting the outer region 22 of the hologram 3 as the tracking region 24, it is possible to prevent light having a large influence of spherical aberration from entering the focus region 23, and to ensure the linearity of the focus error signal FES. The focus error signal FES is a signal representing the defocus of the light beam condensed on the information recording surfaces 2a and 2b of the optical disc 2.

  As described above, the boundary virtual line 20 having a predetermined shape according to the first embodiment has a circular shape. Only light that is as small as the influence of spherical aberration passes through the focus area. Therefore, the linearity of the focus error signal FES can be improved most efficiently. The boundary virtual line 20 having a predetermined shape may be elliptical. For example, if the optical axis of the reflected light from the optical disk 2 is not perpendicular to the surface of the hologram 3, the optical axis of the reflected light is perpendicular to the surface of the hologram 3 by forming an elliptical shape corresponding to the inclination. The same effect as the circular shape in the case of. The boundary virtual line 20 having a predetermined shape may be a quadrangular shape, a rounded square shape, another polygonal shape, a rounded polygonal shape, or the like.

  In the inner area 21, an allocation area 27 that is divided by the boundary virtual line 20 and a single boundary virtual line 25 corresponding to the track longitudinal direction of the optical disc 2 is used as the tracking area 24. The allocation area 27 is an area having a large amount of change with respect to the track deviation. By using the allocation area 27 as the tracking area 24, the sensitivity of tracking control can be increased. Further, a concession area 28 that is divided by the boundary virtual line 20 and the two boundary virtual lines 26 corresponding to the track longitudinal direction of the optical disc 2 and includes the center O of the hologram 3 is also used as the tracking area 24. The amount of reflected light from the information recording surfaces 2b and 2a other than the predetermined information recording surfaces 2a and 2b that are recorded and reproduced by being irradiated with laser light from the laser light source 1 may be reduced. it can. Therefore, the value of the focus error signal FES in the area far from the optical disk 2 or the area close to the optical disk 2 can be stably made close to 0.

  The two focus areas 23 are arranged substantially line-symmetrically with the boundary virtual line 29 of the center line of the hologram 3 corresponding to the track longitudinal direction of the optical disc as the symmetry axis. Even if the optical disc 2 has a scratch or the like, it is also possible to capture information on the focus shift while avoiding the area. Therefore, it is resistant to scratches on the surface of the optical disc 2. Further, the area from the first quadrant to the fourth quadrant of the focus area 23 of the hologram 3 becomes substantially equal. Therefore, it is possible to generate the focus error signal FES by taking in information regarding the focus shift without deviation from the first quadrant to the fourth quadrant.

  The hologram 3 is divided into four by a boundary virtual line 29 corresponding to the track longitudinal direction of the optical disc 2 and a boundary virtual line 30 corresponding to the track transverse direction which is a direction orthogonal to the track longitudinal direction of the optical disc 2. The boundary virtual line 29 and the boundary virtual line 30 intersect at the center O of the hologram 3. Each focus area 23 is divided into two by a boundary virtual line 30 and further divided into three by a boundary virtual line 31 corresponding to the track longitudinal direction. Among the divided focus areas 23, the areas on both sides in the first quadrant and the third quadrant and the central area in the second quadrant and the fourth quadrant of FIG. In addition, the central region in the first quadrant and the third quadrant and the regions on both sides in the second quadrant and the fourth quadrant are defined as the second focus region 33.

  The focus area 23, the first focus area 32, and the second focus area 33 are desirably arranged so as not to be biased from the first quadrant to the fourth quadrant. Therefore, the center of the focus area 23 is made to coincide with the center O of the hologram 3. The first focus area 32 and the second focus area 33 are arranged so as to be alternately arranged in the direction corresponding to the track crossing direction, and the first focus area 32 and the second focus are set in the direction corresponding to the track longitudinal direction. The regions 33 were arranged adjacent to each other. The first focus area 32 and the second focus area 33 are arranged substantially point-symmetrically with respect to the center O of the hologram 3. Therefore, the areas of the first focus area 32 and the second focus area 33 in the first quadrant and the third quadrant are approximately equal, and the areas of the first focus area 32 and the second focus area 33 in the second quadrant and the fourth quadrant are approximately equal. equal. Therefore, it is possible to generate the focus error signal FES by taking in information regarding the focus shift without deviation from the first quadrant to the fourth quadrant.

  The laser beam reflected by the information recording surfaces 2a and 2b and passing through the first focus area 32 in the focused state enters the light receiver 4 after being in the focused state. Conversely, the laser light that has passed through the second focus area 33 enters the light receiver 4 before being brought into focus. The focus state of the light that has passed through the first focus area 32 and the focus state of the light that has passed through the second focus area 33 may be interchanged. By using these two types of light beams, focus control by the spot size method can be performed.

  The tracking area 24 includes a first tracking area 34 that separates reflected light from the optical disk 2 into light mainly used for tracking control, and a second tracking area that separates reflected light from the optical disk 2 into light used as an auxiliary for tracking control. 35. The tracking region 24 in the outer region 22 of the circular boundary virtual line 20 in the tracking region 24 is divided into an end region and a central region along the track longitudinal direction of the optical disc 2. The end region is used as the first tracking region 34 and the central region is used as the second tracking region 35. Further, the tracking area 24 of the concession area 27 in the inner area 21 of the boundary virtual line 20 is used as the first tracking area 34, and the tracking area 24 of the concession area 28 is used as the second tracking area 35.

  The areas of the first tracking region 34 and the second tracking region 35 are adjusted so that the amount of light passing through the first tracking region 34 and the amount of light passing through the second tracking region 35 are substantially the same. Since information on the track deviation is included in the periphery in the track crossing direction, the first tracking area 34 contains a lot of information on the track deviation. Therefore, the tracking error signal TES used for tracking control mainly using the first tracking region 34 having a large amount of information regarding the track shift and assisting the second tracking region 35 is obtained. The tracking error signal TES is a signal representing a deviation in the track crossing direction with respect to the track of the light beam condensed on the information recording surfaces 2a and 2b of the optical disc 2.

  Further, the first tracking region 34 and the second tracking region 35 are arranged substantially line-symmetrically with the boundary virtual line 29 of the center line corresponding to the track longitudinal direction of the hologram 3 as the symmetry axis. Since the same effect can be obtained regardless of whether the deviation from the track is left or right, the focused spot on the information recording surface can be stably placed at the center of the track. The tracking area 24 is divided by boundary virtual lines 29 and 30.

  FIG. 3 is a diagram illustrating the arrangement of the light detection units of the light receiver according to the first embodiment. Two focus light detectors 4a are arranged at a predetermined interval in a direction corresponding to the track longitudinal direction. In each of the focus light detection units 4a, the first focus light detection unit 4c and the second focus light detection unit 4d, which are long in the direction corresponding to the track crossing direction, are alternately adjacently arranged in the direction corresponding to the track longitudinal direction. In the first embodiment, in each focus light detection unit 4a, three first focus light detection units 4c and two second focus light detection units 4d are arranged alternately. All the first focus light detection units 4c are electrically connected to each other, and all the second focus light detection units 4d are also electrically connected to each other. If the electrical signal converted by the light quantity received by the first focus light detection unit 4c is IG, and the electrical signal converted by the light quantity received by the second focus light detection unit 4d is IH, the focus error signal FES is FES = IG. -IH is calculated.

  The two tracking light detection units 4b are arranged outside the direction corresponding to the track longitudinal direction of the focus light detection unit 4a. The tracking light detector 4b is vertically divided by a center line corresponding to the track longitudinal direction, and the first tracking light detector 4e and the second tracking light detector 4f are alternately arranged in the direction corresponding to the track longitudinal direction. Both the first tracking light detection unit 4e and the second tracking light detection unit 4f are long in the direction corresponding to the track crossing direction.

  The portion of the tracking light detection unit 4b located above the paper surface in FIG. 3 has a second tracking light detection unit 4f, a first tracking light detection unit 4e, a second tracking light detection unit 4f, and a first tracking portion in the upper half from the outside. The tracking light detection units 4e are arranged in order. There is no innermost first tracking light detector 4e in the lower half. The portion of the tracking light detection unit 4b located below the paper surface in FIG. 3 has a first tracking light detection unit 4e, a second tracking light detection unit 4f, a first tracking light detection unit 4e, and a second tracking portion from the outside in the lower half. The tracking light detectors 4f are arranged in order. There is no innermost second tracking light detector 4f in the upper half.

  All the first tracking light detection units 4e are electrically connected to each other, and all the second tracking light detection units 4f are also electrically connected to each other. The tracking error signal TES is expressed as TES = IE−, where IE is the electrical signal converted by the first tracking light detection unit 4e and the IF converted electric signal received by the second tracking light detection unit 4f. Calculated as IF.

  As shown in FIG. 1, the light that has passed through the focus region 23 and the tracking region 24 in the fourth quadrant of the hologram 3 enters the focus light detection unit 4a and the tracking light detection unit 4b in the second quadrant. Similarly, light that has passed through the region in the first quadrant of the hologram 3 enters the light detection unit in the third quadrant, and light that has passed through the region in the second quadrant enters the light detection unit in the fourth quadrant. The light that has passed through the region in the third quadrant enters the light detection unit in the first quadrant.

  The light reflected by the predetermined information recording surfaces 2a and 2b and passing through the focus area 23 in the focused state is incident as a spot 5 on the predetermined first focus light detection unit 4c and second focus light detection unit 4d. . The light that has passed through the first tracking region 34 enters the first tracking light detection unit 4e or the second tracking light detection unit 4f that is second from the outside of the tracking light detection unit 4b as a spot 5a. The light that has passed through the second tracking region 35 enters the first tracking light detection unit 4e or the second tracking light detection unit 4f that is third from the outside of the tracking light detection unit 4b as a spot 5b.

  However, the second tracking light detection unit 4f, the first tracking light detection unit 4e, and the fourth tracking light detection unit 4e and the second tracking light detection unit 4f, which are the fourth from the outside, are in focus. Light that has been reflected by the predetermined information recording surfaces 2a and 2b and passed through the tracking region 24 does not enter. These are for canceling an offset component of the tracking error signal TES generated by reflected light from information recording surfaces 2b and 2a other than predetermined information recording surfaces 2a and 2b, which will be described later, to approach zero.

  FIG. 4 is a diagram illustrating a spot state on the focus light detection unit according to the first embodiment. The spot 5 is reflected by the predetermined information recording surfaces 2 a and 2 b in a focused state, and is a combination of light that has passed through the first focus area 32 and light that has passed through the second focus area 33. Since the light that has passed through the first focus region 32 is light that enters the focus light detection unit 4a after being in focus, it enters the focus light detection unit 4a with a slight spread. The shape of the spread is a shape reflecting the shape of the first focus area 32. Similarly, since the light that has passed through the second focus area 33 is incident on the focus light detection unit 4a before being in focus, it enters the focus light detection unit 4a with a slight spread. The shape of the spread also reflects the shape of the second focus area 33. For easy understanding in FIG. 4, the first focus area 32 and the spot 5c corresponding to the light passing through the first focus area 32 are provided with diagonal lines. In addition, the second focus area 33 and the spot 5d corresponding to the light passing through the second focus area 33 are not provided with diagonal lines. The position corresponding to the center O of the hologram 3 in the spot 5c is located on the first focus light detection unit 4c, and the spot 5c extends across the first focus light detection unit 4c and the second focus light detection unit 4d. is there. The position corresponding to the center O of the hologram 3 in the spot 5d is located on the second focus light detection unit 4d, and the spot 5d extends across the second focus light detection unit 4d and the first focus light detection unit 4c. is there.

  FIG. 5 is a diagram showing a change in the focus error signal FES with respect to the distance from the optical disc according to the first embodiment. When the optical disc 2 approaches or separates, the position where the light that has passed through the focus region 23 becomes in focus approaches or separates from the light receiver 4. When the optical disc 2 approaches from the focused state, the position where the light that has passed through the first focus region 32 becomes in the focused state approaches the focus light detection unit 4a, and the spot 5c becomes smaller. At that time, the position on the focus light detection unit 4a at the position corresponding to the center O of the hologram 3 does not change. For this reason, the amount of light incident on the first focus light detector 4c increases, the amount of light incident on the second focus light detector 4d decreases, and the focus error signal FES has an element that swings positively. In addition, the position where the light that has passed through the second focus region 33 becomes in focus is away from the focus light detection unit 4a, and the spot 5d becomes larger. Therefore, the amount of light incident on the second focus light detection unit 4d decreases, the amount of light incident on the first focus light detection unit 4c increases, and the focus error signal FES has an element that swings positively. Since both the spot 5c and the spot 5d have elements in which the focus error signal FES swings positively, the focus error signal FES swings positive when the optical disc 2 approaches from the focused state. Conversely, when the optical disc 2 moves away, the focus error signal FES swings negatively.

  On the other hand, since the light incident on the focus light detection unit 4a is blurred at a position far from the in-focus state, the amount of light received by the first focus light detection unit 4c and the amount of light received by the second focus light detection unit 4d Are substantially equal, and the focus error signal FES is substantially zero. Since the optical disc 2 of the first embodiment is a DVD having two layers of information recording surfaces 2a and 2b, the phenomenon described above exists on each of the information recording surfaces 2a and 2b. The curve has a focused state.

  The first focus area 32 and the second focus area 33 are separated by a boundary virtual line 29 corresponding to the track longitudinal direction. Therefore, the shape of the spot 5c applied to the first focus light detection unit 4c and the shape of the spot 5d applied to the second focus light detection unit 4d are substantially rectangular. Therefore, when the optical disk approaches or moves away from the use area, the area changes regularly, so that it is easy to ensure the linearity of the focus error signal FES.

  Further, the positions of the spots 5c and 5d in the track longitudinal direction corresponding to the boundary virtual line 30 which is the center line corresponding to the track crossing direction hardly change even if the spots 5c and 5d become larger or smaller. In the focus light detection unit 4a, the first focus light detection unit 4c and the second focus light detection unit 4d are alternately arranged in a direction corresponding to the track longitudinal direction. Therefore, even if the spots 5c and 5d become larger or smaller, the portions of the spots 5c and 5d corresponding to the boundary virtual line 30 are the first focus light detection unit 4c or the second focus light detection unit on which the spots 5c and 5d are incident. It is difficult to protrude from 4d.

  FIG. 6 is a diagram showing a focused state on the optical disc according to the first embodiment. The objective lens 6 is a condensing lens for focusing the laser light emitted from the laser light source 1 on the information recording surfaces 2a, 2b and 2c of the optical disc 2. In the case of the optical disc 2 having the single-layer information recording surface 2c indicated by the broken line, the distance from the surface 2d of the optical disc to the information recording surface 2c is 0.6 mm as described above. When the objective lens 6 is at the position indicated by the broken line, the laser light transmitted through the objective lens 6 is focused on the information recording surface 2c as the light beam 7 indicated by the broken line.

  In the optical disk 2 having two layers of information recording surfaces 2a and 2b indicated by solid lines, when recording or reproduction is performed on the information recording surface 2a on the near side, the objective lens 6 is divided by the corresponding amount as shown by the solid line on the left side of FIG. Arranged on the front side. At that time, the light beam 7 indicated by the solid line transmitted near the center of the objective lens 6 is almost focused on the information recording surface 2a, but the peripheral portion of the objective lens 6 is covered by the short distance from the surface 2d to the information recording surface 2a. The transmitted light beam 7 is shifted from the in-focus state and enters the information recording surface 2a. This is called spherical aberration. This spherical aberration has a property that the influence on the light transmitted near the center of the objective lens 6 is small, and the influence on the peripheral portion is large.

  When recording or reproduction is performed on the information recording surface 2b on the far side, the objective lens 6 is disposed on the far side as shown by the solid line on the right side of FIG. At that time, a light beam 7 indicated by a solid line transmitted near the center of the objective lens 6 is almost focused on the information recording surface 2b. However, the light beam 7 that has passed through the peripheral portion of the objective lens 6 by the distance from the surface 2d to the information recording surface 2a is shifted from the focus and enters the information recording surface 2b to generate spherical aberration in the opposite direction. .

  Therefore, among the light reflected in the focused state on the information recording surface 2a and the information recording surface 2b of the optical disc 2, the influence of the spherical aberration becomes larger as the light in the peripheral portion. The light having a large influence of the spherical aberration passes through the focus area 23, so that the linearity of the focus error signal FES in the use area is destroyed. In the optical pickup device according to the first embodiment, the inner area 21 of the boundary virtual line 20 having a predetermined shape is used as the focus area 23, and therefore the focus area 23 does not exist in the peripheral portion of the hologram 3. Therefore, the light that has passed through the focus region 23 is less affected by spherical aberration. Therefore, the linearity of the focus error signal FES in the use area is kept good.

  FIG. 7 is a diagram showing reflected light from an information recording surface other than the predetermined information recording surface of the first embodiment, and FIG. 8A is focused on the information recording surface on the near side of the first embodiment. FIG. 8B is a diagram showing an example of spot distribution on the light receiver when recording or reproduction is performed. FIG. 8B is a diagram showing the spot distribution on the light receiver when recording or reproduction is performed by focusing on the back information recording surface. It is a figure which shows the example of distribution.

  When recording and reproduction are performed by focusing on the information recording surface 2a on the front side as shown on the left side of FIG. 7, some of the light beams 7 pass through the information recording surface 2a and reach the information recording surface 2b on the back side. Then, it is reflected and returns to the objective lens 6. Further, FIG. 8A shows a state where a spot is formed on the light receiver through the hologram 3. The light reflected in the focused state on the information recording surface 2a passes through the focus area 23 and the tracking area 24 as described above and enters the light receiver 4 as spots 5, 5a, 5b. The spot 5 is slightly out of focus, and the spots 5a and 5b are almost in focus. At this time, of the light reflected by the information recording surface 2 b, the light that has passed through the first focus area 32 enters the light receiver 4 as the stray light spot 8, and the light that has passed through the second focus area 33 enters the light receiver 4. The light that has passed through the first tracking region 34 enters the light receiver 4 as the stray light spot 10, and the light that has passed through the second tracking region 35 enters the light receiver 4 as the stray light spot 11.

  Each of the stray light spots 8, 9, 10, 11 is not in focus. The position corresponding to the center O of the passed hologram 3 hardly moves on the light receiver 4, but the light deviated from the center O is the distance from the information recording surface 2a to the information recording surface 2b and the hologram 3 through which the light has passed. The position on the light receiver 4 changes in proportion to the distance from the center O. That is, each of the stray light spots 8, 9, 10, 11 has a shape reflecting the shape of the area of the hologram 3 that has passed through. Further, if there is a variation in the optical disk 2 such as the distance from the information recording surface 2a to the information recording surface 2b varies, the positions of the stray light spots 8, 9, 10, 11 are centered on the positions of the spots 5, 5a, 5b. Change. At that time, the position corresponding to the cross-track direction corresponding to the boundary virtual line 29 of the hologram 3 is hardly changed, and the position corresponding to the track longitudinal direction corresponding to the boundary virtual line 30 is hardly changed.

  8A, only the stray light spot 11 that has passed through the second tracking region 35 near the center of the hologram 3 among the stray light spots 8, 9, 10, and 11 is applied to the tracking light detection unit 4b. The other stray light spots 8, 9, and 10 pass through the focus region 23 and the first tracking region 34 that are not the central portion of the hologram, and are thus out of the focus light detection unit 4a and the tracking light detection unit 4b.

  The edge portions of the first tracking light detection unit 4e and the second tracking light detection unit 4f are parallel to the direction corresponding to the track longitudinal direction and the track crossing direction. Further, the edge of the stray light spot 11 on the first tracking light detection unit 4e and the second tracking light detection unit 4f is a boundary virtual line corresponding to the track longitudinal direction and the track crossing direction in which the second tracking region 35 is divided. It corresponds to 29 and 30. Therefore, the edge portion of the portion of the stray light spot 11 on the first tracking light detection unit 4e and the second tracking light detection unit 4f is parallel to the direction corresponding to the track longitudinal direction and the track crossing direction. Therefore, the shape of the stray light spot 11 applied to the first tracking light detection unit 4e and the second tracking light detection unit 4f is substantially rectangular. The area of the stray light spot 11 applied to the first tracking light detection unit 4e is substantially equal to the area of the stray light spot 11 applied to the adjacent second tracking light detection unit 4f, the amount of received light is substantially equal, and the output electric signal is also substantially the same. equal. Therefore, the offset component due to the stray light spot 11 included in the tracking error signal TES = IE-IF is canceled and becomes almost zero.

  Even if there is a variation in the optical disc 2, the area of the stray light spot 11 applied to the first tracking light detection unit 4e and the area of the stray light spot 11 applied to the adjacent second tracking light detection unit 4f remain substantially equal. The offset component is always almost zero. Even if there are variations in the optical disc 2, the area of the other stray light spots 8, 9, 10 on the focus light detection unit 4a and the tracking light detection unit 4b is small. Therefore, the offset component of the focus error signal FES and the offset component of the tracking error signal TES caused by the stray light spots 8, 9, 10, and 11 can be set to almost zero, respectively.

  As shown on the right side of FIG. 7, even when recording or reproduction is performed by focusing on the information recording surface 2 b on the back side, the light beam 7 that is not in focus is reflected by the information recording surface 2 a on the near side, and the objective lens Return to 6. Further, FIG. 8B shows a state in which spots are formed on the light receiver 4 through the hologram 3. The light reflected by the information recording surface 2b is incident on the same position as FIG. 8A as 5, 5a and 5b. The light reflected by the information recording surface 2 a enters the light receiver 4 as stray light spots 8, 9, 10, 11. The area of the stray light spots 8 and 9 applied to the first focus light detection unit 4c and the area of the stray light spots 8 and 9 applied to the second focus light detection unit 4d are determined by the first focus light detection unit 4c and the second focus light detection unit 4d. Are almost equal because they are alternately lined up alternately. Further, the stray light spots 10 and 11 are not applied. Therefore, the offset component of the focus error signal FES due to the stray light spots 8, 9, 10, and 11 is almost zero. Further, the area of the stray light spots 10 and 11 applied to the first tracking light detection unit 4e is substantially equal to the area of the stray light spots 10 and 11 applied to the second tracking light detection unit 4f. Further, the stray light spot 8 does not reach the tracking light detection unit 4b, and the area of the stray light spot 9 applied to the first tracking light detection unit 4e is substantially equal to the area of the second tracking light detection unit 4f. Therefore, the offset component of the tracking error signal TES caused by the stray light spots 8, 9, 10, and 11 is almost zero.

  As described above, the optical pickup device according to the first embodiment substantially reduces the offset components of the focus error signal FES and the tracking error signal TES caused by the reflected light from the information recording surface other than the predetermined information recording surface for recording and reproduction. It can be set to zero. Therefore, the recording and reproduction characteristics are good. In particular, when recording or reproduction is performed by focusing on the information recording surface 2a on the front side, the stray light spots 8 and 9 from the information recording surface 2b on the back side are focused light because the focus area 23 is not at the center of the hologram 3. It hardly takes the detection unit 4a or the tracking light detection unit 4b. Therefore, it is suitable for setting the offset component to zero.

  The stray light spots 8, 9, 10, and 11 may be incident as shown in FIG. 8B in the case of the left side of FIG. 7 and in the case of the right side of FIG.

  FIG. 9A is a diagram showing a configuration of a hologram of another example 1 of the first embodiment, and FIG. 9B is a diagram showing a configuration of a hologram of another example 2. FIG. 10A is a diagram showing a configuration of a hologram of another example 3 of the first embodiment, and FIG. 10B is a diagram showing a configuration of a hologram of another example 4. FIG. 11 is a diagram illustrating a hologram configuration and a focus light detection unit according to another example 5 of the first embodiment.

  In FIG. 9A, the inner region 41 of the boundary virtual line 40 having a predetermined shape which is a circular shape of the hologram 12 is a focus region 43 and the outer region 42 is a tracking region 44. Further, the allocation area 48 delimited by the boundary virtual line 40 and the boundary virtual line 45 corresponding to one track longitudinal direction is defined as the tracking area 44. A tracked region 44 is defined as a concession region 49 that is divided by the boundary virtual line 40 and the boundary virtual line 46 corresponding to the two track longitudinal directions and includes the center of the hologram 12. Further, the allocation area 50 delimited by the boundary virtual line 40 and the boundary virtual line 47 corresponding to the track longitudinal direction is defined as the tracking area 44. The four focus regions 43 are arranged symmetrically about the boundary virtual line 51 that is the center line of the hologram 12 corresponding to the track longitudinal direction.

  The hologram 12 is further divided into two by a boundary virtual line 52 which is a center line corresponding to the track crossing direction. Further, the focus area 43 closer to the periphery corresponding to the track longitudinal direction is divided into two by a boundary virtual line 53 corresponding to the track longitudinal direction. The arrangement of the first focus area 54 and the second focus area 55 is the same as that of the first focus area 32 and the second focus area 33. The tracking area 44 is substantially the same as the tracking area 24, but the first tracking area 56 is extended to the concession area 50 so as to extend the boundary virtual line 58 that separates the first tracking area 56 and the second tracking area 57 of the outer area 42. And a second tracking region 57 are disposed.

  The focus area 43 has almost the same area as the focus area 23, but is more dispersed in the hologram 12. For this reason, even if the surface 2d of the optical disk 2 is scratched, a portion of the light that avoids the damage may enter the focus light detection unit of the light receiver 4. Therefore, the hologram 12 is resistant to scratches on the surface of the optical disc 2.

  In FIG. 9B, the inner area 61 of the predetermined boundary virtual line 60 having a circular shape of the hologram 13 is the same as the inner area 41 and the outer area 62 of the hologram 12 is the same as the outer area 42. The focus area 63, the first focus area 65, and the second focus area 66 are the same as the focus area 43, the first focus area 54, and the second focus area 55. The tracking area 64 is the same as the tracking area 44. The first tracking area 67 and the second tracking area 68 are separated by a boundary virtual line 69 corresponding to the track longitudinal direction. The stray light spot reflected by the information recording surfaces 2b and 2a other than the predetermined information recording surfaces 2a and 2b and separated by the boundary virtual line 69 is applied to the focus light detection unit 4a and the tracking light detection unit 4b. In some cases, the shape is easily rectangular. Therefore, it is easy to stably remove the offset components of the focus error signal FES and the tracking error signal TES due to the stray light spot.

  Also in FIG. 10A, the inner area 71 of the predetermined boundary virtual line 70 having the circular shape of the hologram 14 is the focus area 73 and the outer area 72 is the tracking area 74. Further, the allocation area 76 divided by the boundary virtual line 70 and the boundary virtual line 75 corresponding to one track longitudinal direction is defined as the tracking area 74. By ensuring a sufficiently wide allocation area 76, an area having a large amount of information on track deviation is sufficiently set as the tracking area 74, and the stability of tracking control is improved. The focus area 73 is divided into a first focus area 79 and a second focus area 80 by a boundary virtual line 77 corresponding to the center line corresponding to the track crossing direction and a plurality of boundary virtual lines 78 corresponding to the track longitudinal direction. In addition, the tracking area 74 is divided into a first tracking area 81 and a second tracking area 82, and most of the area having a lot of information regarding track deviation can be the first tracking area 81.

  In FIG. 10B, the inner area 91 of the boundary virtual line 90 having a predetermined shape which is the circular shape of the hologram 15 is the same as the inner area 21 and the outer area 92 of the hologram 3 is the same as the outer area 22. The focus area 93, the first focus area 95, and the second focus area 96 are the same as the focus area 23, the first focus area 32, and the second focus area 33. The tracking area 94 is the same as the tracking area 24. A central portion of the hologram 15 in the assigned area 99 is defined as a first tracking area 97. Accordingly, the area of the first tracking area 97 in the outer area 92 is reduced, and the area ratio with respect to the second tracking area 98 is adjusted. In the hologram 3, the stray light spot 11 at the center of the hologram 3 is incident on the tracking light detection unit 4b along with the spot 5b. In the hologram 15, the stray light spot 10 at the center of the hologram 15 is incident on the tracking light detection unit 4b along with the spot 5a. The configuration of the hologram 15 can be anything.

  In FIG. 11, the inner region 101 and the outer region 102 of the boundary virtual line 100 having a predetermined shape which is a circular shape of the hologram 16 are the same as the inner region 21 and the outer region 22 of the hologram 3. The inner area 101 is a focus area 103 and the outer area 102 is a tracking area 104. The focus area 103 is rotated by 90 ° with respect to the focus area 23. That is, the allocation area 107 divided by the boundary virtual line 100 and the boundary virtual line 105 corresponding to one track crossing direction is set as the tracking area 104. Further, the allocation region 108 that is divided by the boundary virtual line 100 and the boundary virtual line 106 corresponding to the two track crossing directions and includes the center O of the hologram 16 is defined as the tracking region 104.

  The hologram 16 is divided into two by a boundary virtual line 109 which is a center line corresponding to the track longitudinal direction. Further, the hologram 16 is divided into two by a boundary virtual line 110 which is a center line corresponding to the track crossing direction. Further, the tracking area 104 is divided by a plurality of boundary virtual lines 111 corresponding to the track crossing direction. The first focus area 112 and the second focus area 113 are alternately arranged. In the tracking region 104, a region where the amount of change with respect to the track deviation is large can be a first tracking region 114, and a region that is not so can be a second tracking region 115, and the sensitivity of tracking control can be increased.

  In the light receiver 17, the configuration of the focus light detection unit 17 a particularly changes in accordance with the hologram 16, and the focus light detection unit 17 a rotates 90 ° with respect to the focus light detection unit 4 a. Two focus light detectors 17a are arranged at a predetermined interval in a direction corresponding to the track crossing direction. In each of the focus light detection units 17a, first focus light detection units 17b and second focus light detection units 17c that are long in a direction corresponding to the track longitudinal direction are arranged alternately adjacent to each other in a direction corresponding to the track crossing direction. In FIG. 11, in each focus light detection unit 17a, three first focus light detection units 17b and two second focus light detection units 17c are alternately arranged.

  The spot 18 is reflected by the predetermined information recording surfaces 2 a and 2 b in a focused state, and is a combination of light that has passed through the first focus area 112 and light that has passed through the second focus area 113. Since the light that has passed through the first focus region 112 is light that enters the focus light detection unit 17a after being in focus, it enters the focus light detection unit 17a with a slight spread. The shape of the spread is a shape reflecting the shape of the first focus area 112. Similarly, since the light that has passed through the second focus region 113 is incident on the focus light detection unit 17a before being brought into focus, it enters the focus light detection unit 17a with a slight spread. The shape of the spread also reflects the shape of the second focus area 113. The position corresponding to the center O of the hologram 16 in the spot 18a is located on the first focus light detection unit 17b, and the spot 18a extends over the first focus light detection unit 17b and the second focus light detection unit 17c. is there. The position corresponding to the center O of the hologram 16 in the spot 18b is set on the second focus light detection unit 17c, and the spot 18b extends over the second focus light detection unit 17c and the first focus light detection unit 17b. is there.

  The positions in the track crossing direction of the spots 18a and 18b corresponding to the boundary virtual line 109, which is the center line corresponding to the track longitudinal direction, hardly change even if the spots 18a and 18b become larger or smaller. In the focus light detection unit 17a, the first focus light detection unit 17b and the second focus light detection unit 17c are alternately arranged in a direction corresponding to the track crossing direction. Therefore, even if the spots 18a and 18b become larger or smaller, the portions of the spots 18a and 18b corresponding to the boundary virtual line 109, which is the center line, are incident on the first focus light detection unit 17b or the second focus light detection unit 17b. It is difficult to protrude from the focus light detection unit 17c.

  As described above, the optical pickup device of the first embodiment has good linearity of the focus error signal FES because only light having a small influence of spherical aberration passes through the focus region. Therefore, the optical pickup device according to the first embodiment can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc.

(Embodiment 2)
The second embodiment will be described with reference to the drawings. FIG. 12 is a configuration diagram of an optical system of the optical pickup device according to the second embodiment, and FIG. 13 is a configuration diagram of the optical pickup device according to the second embodiment. The optical pickup device of the second embodiment includes the laser light source, the hologram, and the light receiver of the first embodiment.

  In the optical pickup device 166 according to the second embodiment, a laser module 152 having a diffraction element 153, a reflection mirror 154, a collimating lens 155, a rising mirror 156, and a front light monitor 162 are arranged at predetermined positions on a base 164. Configured. Further, the optical pickup device 166 arranges an objective lens driving device 165 including a lens holder 165 a for arranging the objective lens 161 and the hologram element 160 at a predetermined position of the base 164. The laser module 152 is a single package including a laser light source 150 that emits laser light and a light receiver 151 that receives the laser light emitted from the laser light source 150 and reflected by the optical disk 163. In the second embodiment, the optical disk 163 is a DVD or a CD. The hologram element 160 is an element in which a hologram 157 for DVD, a hologram 158 for CD, and a quarter wavelength plate 159 are integrated.

  In the second embodiment, the optical disk 163 is a DVD and a CD. That is, the optical pickup device 166 according to the second embodiment can perform recording and reproduction on DVDs and CDs. The DVD is a DVD-ROM, DVD ± R / RW, DVD-RAM, or the like. CD is CD, CD-ROM, CD-R / RW. Both DVDs and CDs can be recorded and played back except for read-only media. Moreover, although the information recording surface of the CD is a single layer, the DVD includes an optical disc having a plurality of information recording surfaces including an optical disc having two information recording surfaces. Further, the optical disk 163 is not limited to the combination of DVD and CD, but also in combination with Blu-ray Disc, HD-DVD and the like.

  In the second embodiment, the laser light source 150 emits a laser beam with a wavelength of about 650 nm for DVD and a laser beam with a wavelength of about 780 nm for CD in accordance with the optical disk 163. The laser light source 150 includes a laser element that emits a DVD laser beam and a CD laser beam, or a combination of a laser element that emits a DVD laser beam and a laser element that emits a CD laser beam. . The laser element is disposed on a semiconductor substrate on which the light detection unit of the light receiver 151 is disposed. A reflection mirror is disposed on the semiconductor substrate, and the reflection mirror directs laser light emitted in a direction parallel to the surface of the semiconductor substrate to the optical disk 163. The laser beam for DVD and the laser beam for CD emitted from the laser module 152 are substantially parallel and close to each other, and are P-polarized light.

  The diffraction element 153 has a diffraction grating that does not act on the DVD laser beam and diffracts only the CD laser beam. The diffraction grating diffracts and separates the laser beam for CD into 0th order light, ± first order light, and the like. The 0th order light is called the main beam, and the ± 1st order light is called the side beam. The amount and direction of the separated light are determined by the wavelength of light passing through the diffraction grating, the refractive index of the diffraction grating, the grating depth, the grating interval, the direction of the grating, and the like.

  The reflection mirror 154 is for bending the laser light emitted from the laser light source 150, and for reducing the size of the optical pickup device 166. A polarization separation film is formed on the surface of the reflection mirror 154, and the polarization separation film reflects most of the P-polarized laser light emitted from the laser light source 150 and transmits part of it. The polarization separation film substantially totally reflects the laser beam reflected by the optical disk 163 and converted to S-polarized light.

  The collimating lens 155 converts laser light emitted from the laser light source 150 that is divergent light into substantially parallel light. Conversely, the laser light reflected by the optical disk 163, which is parallel light, is converted into focused light. The collimating lens 155 is made of optical glass or optical plastic.

  The rising mirror 156 is a reflection mirror that converts the laser light, which has been in a direction substantially parallel to the optical disk 163 so far, into a direction at a substantially right angle.

  FIG. 14 is a configuration diagram of a DVD hologram according to the second embodiment. The DVD hologram 157 is the same as the hologram 3 of the first embodiment. The same hologram 12, hologram 13, hologram 14, hologram 15, and 16 may be used. When the hologram 16 is used, a light receiver having the same focus light detection unit as the focus light detection unit 17a of the light receiver 17 is used. The description of the first embodiment is applied to the description of the hologram 157. The boundary virtual lines 20, 25, 26, 29, 30, and 31 are replaced with boundary virtual lines 180, 185, 186, 189, 190, and 191 respectively. The inner region 21 is replaced with the inner region 181, and the outer region 22 is replaced with the outer region 182. The focus area 23, the first focus area 32, and the second focus area 33 are replaced with a focus area 183, a first focus area 192, and a second focus area 193, respectively. The tracking area 24, the first tracking area 34, and the second tracking area 35 are replaced with a tracking area 184, a first tracking area 194, and a second tracking area 195, respectively. Allocation areas 27 and 28 are replaced with allocation areas 187 and 188, respectively. The hologram 157 is configured to work only on S-polarized laser light having a wavelength of 650 nm for DVD.

  FIG. 15 is a configuration diagram of a CD hologram according to the second embodiment. The CD hologram 158 is configured to work only on S-polarized laser light having a wavelength of 780 nm for CD. The hologram 158 is delimited by a boundary virtual line 158 a corresponding to the track longitudinal direction of the optical disk 163 and a boundary virtual line 158 b corresponding to the track crossing direction of the optical disk 163. The boundary virtual line 158a and the boundary virtual line 158b pass through almost the center of the hologram 158. The tracking area 158c and the tracking area 158d occupy one side delimited by the boundary virtual line 158b, and the focus areas 158e, 158f, 158g and 158h occupy the other. The tracking area 158c and the tracking area 158d are separated by a boundary virtual line 158a. The focus area 158e and the focus area 158f are separated by a boundary virtual line corresponding to the track longitudinal direction. Further, the focus area 158g and the focus area 158h are separated by a boundary virtual line corresponding to the track longitudinal direction. The focus area 158f and the focus area 158h are separated by a boundary virtual line 158a. The light that has passed through one of the focus area 158e and the focus area 158f enters the light receiver 151 after being in focus, and the light that has passed through the other enters the light receiver 151 before being in focus. In addition, the light that has passed through one of the focus area 158g and the focus area 158h enters the light receiver 151 after being in focus, and the light that has passed through the other enters the light receiver 151 before being in focus.

  In the second embodiment, the tracking area 158c and the tracking area 158d occupy one side delimited by the boundary virtual line 158b, and the focus areas 158e, 158f, 158g and 158h occupy the other. However, the tracking area 158c and the focus areas 158e and 158f may be interchanged, or the tracking area 158d and the focus areas 158g and 158h may be interchanged. Thereby, the amount of stray light to the focus error signal FES for CD can be reduced.

  The quarter-wave plate 159 converts the P-polarized laser light emitted from the laser light source 150 into circularly polarized light and directs it to the optical disk 163. The circularly polarized laser light reflected by the optical disk 163 is converted to S-polarized light and directed to the light receiver 151. Therefore, the holograms 157 and 158 do not act as holograms because they are P-polarized light with respect to the laser light emitted from the laser light source 150. However, since the light reflected by the optical disk 163 is converted to S-polarized light by the quarter-wave plate 159, it can act as a hologram.

  The objective lens 161 is made of optical glass, optical plastic, or the like, and can focus on both DVD and CD of the optical disk 163. As the objective lens 161 which is a bifocal objective lens, a combination of a condensing lens and a Fresnel lens or a hologram lens, a combination in which a condensing lens for DVD is provided with an aperture limiting means at the time of CD reproduction, etc. are used. Those that absorb the difference in number can also be used.

  The front light monitor 162 receives a part of the laser light emitted from the laser light source 150, converts the amount of light into an electric signal, and outputs it. The output electrical signal is sent to the optical disc apparatus main body and used to control the amount of light collected on a predetermined information recording surface of the optical disc 163 to be constant.

  FIG. 16 is a layout diagram of the light detection unit of the light receiver according to the second embodiment. The light receiver 151 has a configuration in which a light detection unit, which is a photodiode, is disposed on a semiconductor substrate. The light incident on the light detection unit is converted into an electric signal corresponding to the light amount and output from the light receiver 151. The focus light detection unit 4a and the tracking light detection unit 4b of the light receiver 4 of the first embodiment are the same as the focus light detection unit 151a and the tracking light detection unit 151b of the light receiver 151 of the second embodiment. The description of the focus light detection unit 151a and the tracking light detection unit 151b of the light receiver 151 of the second embodiment uses the description of the focus light detection unit 4a and the tracking light detection unit 4b of the light receiver 4 of the first embodiment. Accordingly, the focus light detection unit 4a, the first focus light detection unit 4c, and the second focus light detection unit 4d are replaced with the focus light detection unit 151a, the first focus light detection unit 151c, and the second focus light detection unit 151d, respectively. The tracking light detection unit 4b, the first tracking light detection unit 4e, and the second tracking light detection unit 4f are replaced with the tracking light detection unit 151b, the first tracking light detection unit 151e, and the second tracking light detection unit 151f, respectively.

  A laser element constituting the laser light source 150 and a reflection mirror (not shown) for directing the laser beam emitted from the laser element to the optical disk 163 are arranged on the semiconductor substrate. A point at which the laser beam for DVD emitted from the laser element of the laser light source 150 can be redirected by the reflecting mirror is a temporary light emitting point 151m, and a point at which the laser beam for CD can be redirected by the reflecting mirror is a temporary light emitting point 151n. did. CD tracking light detectors 151g and 151h are arranged on the side opposite to the temporary light emitting points 151m and 151n. The CD tracking light detector 151g is electrically connected to the first tracking light detector 151e, and the CD tracking light detector 151h is electrically connected to the second tracking light detector 151f.

  In addition, a light detection unit was provided on the opposite side across the temporary light emission points 151m and 151n. Each of the light detection units 151i, 151j, 151k, and 151l includes two light detection units that are electrically connected.

  When recording or reproducing is performed by focusing on a predetermined information recording surface of a DVD of the optical disk 163, the light that has passed through the focus region 183 among the laser light reflected by the predetermined information recording surface is the first focus as a spot 170. Incident light straddles the light detector 151c and the second focus light detector 151d. The light that has passed through the first tracking region 194 enters the first tracking light detector 151e or the second tracking light detector 151f as a spot 171. The light that has passed through the second tracking region 195 enters the second tracking light detection unit 151f or the first tracking light detection unit 151e as a spot 172.

  The above is one of the + 1st order light and the −1st order light among the lights diffracted by the hologram 157. The other of the + 1st order light and the −1st order light is incident on the light detection units 151i, 151j, 151k, and 151l. Light that has passed through the focus region 183, the first tracking region 194, and the second tracking region 195 enters the light detection units 151i, 151j, 151k, and 151l as spots 170a, 171a, and 172a, respectively.

  Further, the laser beam for CD is separated into a main beam and a side beam by the diffraction grating of the diffraction element 153, reflected by the information recording surface of the CD, passes through the tracking regions 158c and 158d, and the side beam becomes a spot 174. The light enters the CD tracking light detectors 151g and 151h. The main beam is incident on the light detectors 151k and 151l as a spot 174a. Further, the main beam of the laser beam for CD that has passed through the focus areas 158e, 158f, 158g, and 158h is incident on the focus light detector 151a as a spot 173, and is incident on the light detectors 151i and 151j as a spot 173a. Accordingly, the light detection units 151i, 151j, 151k, and 151l take in the main beam that has passed through almost the entire region of the CD hologram 158.

  The outputs from the first focus light detection unit 151c and the second focus light detection unit 151d are IG and IH, and the outputs from the first tracking light detection unit 151e and the second tracking light detection unit 151f are IE and IF. Further, the outputs from the light detection units 151i, 151j, 151k, and 151l are respectively IA, IB, IC, and ID, and the outputs from the CD tracking light detection units 151g and 151h are the same as the tracking light detection units 151e and 151f. , IF.

  A focus error signal FES, which is a focus control signal used for a DVD, is the same as in the first embodiment, and is calculated as FES = IG-IH. The tracking error signal TES for tracking control used for a DVD differs depending on the type of DVD. In the case of DVD-RAM, the tracking error signal TES is calculated as TES = (IA + IB) − (IC + ID). Further, the tracking error signal TES for reproduction other than DVD-RAM is calculated as TES = ＴＥ (IC−ID) + ∠ (IB−IA) or TES = ∠ {(IC + IB) − (ID + IA)}. Here, ∠ is a voltage obtained by converting the detected phase difference. The tracking error signal TES calculated by either arithmetic expression may be used. Further, the tracking error signal TES in the case of recording other than DVD-RAM is calculated as TES = IE-IF. Further, the reproduction signal RF is calculated as RF = IA + IB + IC + ID. Since the reproduction signal RF is reflected by the DVD and captures the laser light of almost the entire region that has passed through the hologram 157 for DVD, the jitter is excellent.

  The focus error signal FES used for the CD is the same as that for the DVD, and FES = IG−IH is calculated. The tracking error signal TES is calculated as TES = (IC−ID) −k (IE−IF). Here, k is a constant determined according to the operation setting, and is normally designed to be ideally k≈1. This method is called a differential push-pull method. The tracking error signal TES may be calculated as TES = Ｓ {(IA + ID) − (IC + IB)}. This method is called a phase difference method. Normally, a differential push-pull method that can perform tracking control more stably is used. However, for example, when reproducing a bad disk whose pit height does not fall within the standard, the tracking error signal TES may not be output successfully by the differential push-pull method. Even in such a case, the phase difference method can output the tracking error signal TES well, so that it can be used as a preliminary tracking control method. As described above, since it is possible to perform the tracking control even in the case of reproducing a poor CD that is out of the standard that cannot be completely tracked, it is possible to deal with a wider range of CDs as an optical disk apparatus. Further, the reproduction signal RF is calculated as RF = IA + IB + IC + ID. Since the side beam does not affect the reproduction signal RF, the jitter is excellent. For the same reason, tracking control by the phase difference method is resistant to noise. Further, the tracking error signal TES by the differential push-pull method is purely generated from the outputs of only the main beam and the side beam, so that it is resistant to noise.

  As described above, in the optical pickup device of the second embodiment, for a DVD having a two-layer information recording surface, only light that is less affected by spherical aberration is the same as described in the first embodiment. Passes through the focus area, the linearity of the focus error signal FES is good. Therefore, the optical pickup device according to the first embodiment can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc. Furthermore, an appropriate control method can be performed also in DVD tracking control. Good focus control and tracking control can also be realized for CD.

  As shown in FIG. 13, the base 164 forms a skeleton of the optical pickup device 166. As described above, the components constituting the optical pickup device 166 including the various optical components are directly or other than the base 164. Installed through the parts. The base 164 is formed of an alloy material such as a Zn alloy or an Mg alloy, or a hard resin material.

  In the objective lens driving device 165, a lens holder 165a to which the hologram element 160 and the objective lens 161 are fixed is elastically supported by a support member on the apparatus main body. A tracking coil and a focus coil are fixed to the lens holder 165a. A magnet is fixed to the apparatus main body. The objective lens driving device 165 generates an electromagnetic force with the magnet by flowing a predetermined current through the tracking coil or the focus coil, and moves the objective lens 161 mounted on the lens holder 165a in the tracking direction or the focus direction. . The drive current that flows through the tracking coil or the focus coil is controlled based on the tracking error signal TES or the focus error signal FES generated from the electric signal that is output by converting the amount of laser light incident on the light receiver 151.

  The hologram 157 for DVD and the hologram 158 for CD are overlapped to form an integral structure as the hologram element 160. When the DVD hologram 157 and the CD hologram 158 are shared by two laser beams having different wavelengths, if the design of the hologram is changed in order to correct one of the problems, the other characteristic is also affected. The degree of freedom in design is increased by providing the DVD hologram 157 and the CD hologram 158 separately and superimposing them. Further, the hologram element 160 is fixed to a lens holder 165a to which the objective lens 161 is fixed. Since the relative positions of the objective lens 161 and the holograms 157 and 158 are not shifted, the light passing through the objective lens 161 is incident on the holograms 157 and 158 without causing a positional shift. Therefore, even if the objective lens 161 is deviated from the track, the track deviation information is reflected in the light incident on the holograms 157 and 158, so that tracking control can be performed correctly.

  The optical path of the optical pickup device 166 having the above configuration will be described. In FIG. 12, the laser beam for DVD emitted from the laser light source 150 passes through the diffraction grating of the diffraction element 153 as it is and enters the reflection mirror 154. Most of the laser light is reflected by the polarization separation film of the reflection mirror 154 and travels toward the DVD of the optical disk 163, but part of the laser light is transmitted and enters the front light monitor 162. The light incident on the front light monitor 162 is converted into an electrical signal and used for controlling the amount of laser light emitted from the laser light source 150. The laser light reflected by the reflection mirror 154 enters the collimator lens 155, is converted from divergent light into parallel light, and enters the rising mirror 156. The laser beam is incident on the hologram element 160 after being bent in a direction perpendicular to the DVD by the rising mirror 156. The hologram element 160 passes through the DVD hologram 157 and the CD hologram 158 as they are, and is converted from P-polarized light to circularly-polarized light by the quarter-wave plate 159 and emitted from the hologram element 160 to the objective lens 161. Incident. The laser beam converted so as to be focused on the information recording surface of the DVD by the objective lens 161 is incident on the information recording surface of the DVD.

  The laser beam reflected on the information recording surface of the DVD is converted into parallel light by the objective lens 161 and enters the hologram element 160. The laser light is converted from circularly polarized light to S polarized light by the quarter wavelength plate 159, passes through the hologram 158 as it is, and is diffracted by the focus region 183 and the tracking region 184 and emitted from the hologram element 160 when passing through the hologram 157. Is done. The light is converted into focused light by the collimator lens 155, reflected by the reflection mirror 154, and the laser light is incident on a predetermined light detection unit of the light receiver 151. The laser light incident on the predetermined light detection unit is converted into an electrical signal, output from the light receiver 151, and sent to the optical disc apparatus main body to generate a focus control signal, a tracking control signal, and a reproduction signal. .

  The laser beam for CD emitted from the laser light source 150 is diffracted by the diffraction grating of the diffraction element 153 into a main beam that is zero-order light and a side beam that is ± first-order light, and enters the reflection mirror 154. Most of the laser light is reflected by the polarization separation film of the reflection mirror 154 and travels toward the CD of the optical disk 163, but part of the laser light is transmitted and enters the front light monitor 162. The light incident on the front light monitor 162 is converted into an electrical signal and used for controlling the amount of laser light emitted from the laser light source 150. The laser light reflected by the reflection mirror 154 enters the collimator lens 155, is converted from divergent light into parallel light, and enters the rising mirror 156. The laser beam is incident on the hologram element 160 after being bent in a direction perpendicular to the CD by the rising mirror 156. The laser light that passes through the hologram 157 and the hologram 158 of the hologram element 160 and is converted from P-polarized light to circularly-polarized light by the quarter wavelength plate 159 and emitted from the hologram element 160 is incident on the objective lens 161. The laser beam converted so as to be focused on the information recording surface of the CD by the objective lens 161 enters the information recording surface of the CD.

  The laser beam reflected by the information recording surface of the CD is converted into parallel light by the objective lens 161 and enters the hologram element 160. The laser light is converted from circularly polarized light to S polarized light by the quarter-wave plate 159, and when passing through the hologram 158, it is diffracted by the focus regions 158e, 158f, 158g, 158h, the tracking regions 158c, 158d, and the hologram 157 is left as it is. The light is transmitted and emitted from the hologram element 160. The light is converted into focused light by the collimator lens 155, reflected by the reflection mirror 154, and the laser light is incident on a predetermined light detection unit of the light receiver 151. The laser light incident on the predetermined light detection unit is converted into an electrical signal, output from the light receiver 151, and sent to the optical disc apparatus main body to generate a focus control signal, a tracking control signal, and a reproduction signal. .

  As described above, in the optical pickup device according to the second embodiment, only the light having a small influence of spherical aberration passes through the focus region, and thus the linearity of the focus error signal FES is good. Therefore, the optical pickup device according to the second embodiment can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc.

(Embodiment 3)
The third embodiment will be described with reference to the drawings. FIG. 17 is a configuration diagram of the optical pickup module according to the third embodiment, and FIG. 18 is a configuration diagram of the optical disk device according to the third embodiment. The third embodiment is an optical disk device on which the optical pickup device described in the second embodiment is mounted.

  A drive mechanism that drives the optical disc 163 and the optical pickup device 166 of the optical disc device 250 is referred to as an optical pickup module 200. The base 201 forms a framework of the optical pickup module 200, and each component is fixed directly or indirectly to the base 201.

  A spindle motor 202 having a turntable on which the optical disk 163 is placed is fixed to the base 201. The spindle motor 202 generates a rotational driving force that rotates the optical disk 163.

  The feed motor 203 is fixed to the base 201. The feed motor 203 generates a rotational driving force necessary for the optical pickup device 166 to move between the inner periphery and the outer periphery of the optical disc 163. As the feed motor 203, a stepping motor, a DC motor, or the like is used. The screw shaft 204 has a spiral groove and is connected to the feed motor 203 directly or through several stages of gears. In the third embodiment, it is directly connected to the feed motor 203. The guide shafts 205 and 206 are fixed to the base 201 via support members at both ends. Guide shafts 205 and 206 support the optical pickup device 166 in a movable manner. The optical pickup device 166 includes a rack 207 having guide teeth that mesh with the grooves of the screw shaft 204. The optical pickup device 166 can move between the inner periphery and the outer periphery of the optical disc 163 in order for the rack 207 to convert the rotational driving force of the feed motor 203 transmitted to the screw shaft 204 into a linear driving force.

  The optical pickup device 166 is the same as that described in Embodiment 2, and further includes a cover 167. The optical pickup device 166 performs at least one of recording and reproduction of information on the optical disc 163 and emits laser light toward the optical disc 163 for that purpose. That is, the optical pickup device 166 includes a laser light source 150, a hologram 157, and a light receiver 151. The laser light source 150 emits light that irradiates the optical disk 163. The hologram 157 has a focus region 183 that separates light emitted from the laser light source 150 and reflected by the optical disk 163 into light used for focus control, and a tracking region 184 that separates light used for tracking control. The light receiver 151 receives the light separated in the focus area 183 by the focus light detector 151a and converts it into an electric signal used for focus control, and receives the light separated in the tracking area 184 by the tracking light detector 151b. Then, it is converted into an electric signal used for tracking control.

  In the hologram 157, the inner area 181 of the boundary virtual line 180 having a predetermined shape centered on the center O of the hologram 157 is a focus area 183, and the outer area 182 of the boundary virtual line 180 is a tracking area 184. The focus area 183 has a first focus area 192 and a second focus area 193, and the tracking area 184 has a first tracking area 194 and a second tracking area 195.

  The inclination of the guide shafts 205 and 206 is adjusted by an adjustment mechanism that constitutes a support member so that the laser light emitted from the optical pickup device 166 is incident on the optical disk 163 at a right angle.

  The upper casing 251a and the lower casing 251b are combined and fixed to each other using screws or the like to form the casing 251. The tray 252 is provided in the housing 251 so as to freely appear and disappear. The tray 252 arranges the optical pickup module 200 to which the cover 208 is attached from the lower surface side. The cover 208 has an opening and exposes a part including the objective lens 161 of the optical pickup device 166 and the turntable of the spindle motor 202. In the case of the third embodiment, the feed motor 203 is also exposed. A bezel 253 is provided on the front end surface of the tray 252 so that when the tray 252 is stored in the housing 251, the entrance and exit of the tray 252 is closed.

  The bezel 253 is provided with an eject switch 254. When the eject switch 254 is pressed, the engagement between the housing 251 and the tray 252 is released, and the tray 252 can be brought into and out of the housing 251. The rails 255 are slidably attached to both sides of the tray 252 and the housing 251, respectively.

  There is a circuit board (not shown) inside the housing 251 and inside the tray 252, and a signal processing system IC, a power circuit, and the like are mounted. The external connector 256 is connected to a power / signal line provided in an electronic device such as a computer. Then, power is supplied into the optical disc apparatus 250 via the external connector 256, an external electric signal is guided into the optical disc apparatus 250, or an electric signal generated by the optical disc apparatus 250 is supplied to an external electronic device or the like. Or send it out.

  A flow of tracking control and focus control of the optical pickup device 166 will be described. FIG. 19 is a diagram illustrating a control flow of the optical pickup device according to the third embodiment. The light incident on the light receiver 151 is converted into electrical signals for DVD tracking control, DVD focus control, CD tracking control, and CD focus control, and enters the analog signal processing unit 250b of the optical disc apparatus main body 250a. . The analog signal processing unit 250b performs calculation / band processing on the input signal and outputs the result to the servo processing unit 250c. The servo processing unit 250c generates a focus error signal and a tracking error signal based on the signal from the analog signal processing unit 250b and outputs the focus error signal and the tracking error signal to the motor driving unit 250d. The focus error signal FES is a signal representing the defocus of the light beam condensed on the information recording surface of the optical disk 163. The tracking error signal TES is a signal representing a deviation in the track transverse direction, which is the radial direction of the optical disk 163, with respect to the track of the light beam condensed on the information recording surface of the optical disk 163. The motor driving unit 250d generates a current for driving the objective lens driving device 165 on which the objective lens 161 is mounted based on the input focus error signal FES and tracking error signal TES. As a result, control is performed so that the deviation of the focal point and the deviation of the light beam collected on the information recording surface of the optical disc 163 is minimized.

  The controller 250e receives signals sent from the analog signal processing unit 250b, servo processing unit 250c, motor driving unit 250d, digital signal processing unit 250f, and laser driving unit 250g. The controller 250e performs arithmetic processing of these signals, sends the result (signal) of this arithmetic processing to each unit, and controls each unit by causing each unit to drive and execute processing.

  The front light monitor 162 receives a part of the laser light emitted from the laser light source 150, converts the amount of light into an electric signal, and outputs it. As shown in FIG. 19, this electric signal enters the analog signal processing unit 250b of the optical disc apparatus main body 250a. The analog signal processing unit 250b performs calculation / band processing on the input signal and outputs it to the digital signal processing unit 250f. The digital signal processing unit 250f generates a laser modulation signal based on the signal from the analog signal processing unit 250b and the data sent from the host 260 and sends it to the laser driving unit 250g. A laser light source driving power source 166a disposed in the vicinity of the laser light source 150 of the optical pickup device 166 main body receives a signal from the laser driving unit 250g and supplies a driving current to the laser light source 150. As a result, the amount of light flux collected on the information recording surface of the optical disk 163 is controlled to be constant.

  As described above, the optical disk device according to the third embodiment includes the optical pickup device according to the second embodiment. In the optical pickup device of the second embodiment, only the light having a small influence of the spherical aberration passes through the focus region, so that the linearity of the focus error signal FES is good. Therefore, the optical pickup device according to the third embodiment can perform stable focus control, and can perform good recording and reproduction on any information recording surface of a plurality of layers of the optical disc. Therefore, the optical disk apparatus according to the third embodiment can perform stable focus control even when information is recorded or reproduced on an optical disk having a plurality of layers of information recording surfaces. Good recording and reproduction can be performed on any information recording surface.

  As described above, the optical pickup device of the present invention can record and reproduce good information on an optical disc having a plurality of information recording surfaces, and is useful as an optical pickup device used in an optical disc device. In addition, the optical disk apparatus of the present invention can perform good recording and reproduction on an optical disk having a plurality of information recording surfaces, and is useful as an optical disk apparatus used in electronic devices such as computers and DVD recorders.

The figure which shows the main structures of the optical pick-up apparatus of this Embodiment 1. The figure which shows the structure of the hologram of this Embodiment 1. The figure which shows arrangement | positioning of the photon detection part of the light receiver of this Embodiment 1. The figure which shows the mode of the spot on the focus light detection part of this Embodiment 1. FIG. The figure which shows the change of the focus error signal FES with respect to the distance with the optical disk of this Embodiment 1. FIG. The figure which shows the focusing state on the optical disk of this Embodiment 1. The figure which shows the reflected light from information recording surfaces other than the predetermined information recording surface of this Embodiment 1. (A) The figure which shows the example of the distribution of the spot on a light receiver in the case of condensing on the near-side information recording surface of this Embodiment 1, and recording and reproducing | regenerating, (b) On the back information recording surface The figure which shows the example of the distribution of the spot on a photoreceiver in the case of collecting and performing recording and reproduction (A) The figure which shows the structure of the hologram of the other example 1 of this Embodiment 1, (b) The figure which shows the structure of the hologram of the other example 2 (A) The figure which shows the structure of the hologram of the other example 3 of this Embodiment 1, (b) The figure which shows the structure of the hologram of the other example 4 The figure which shows the structure of the hologram of the other example 5 of this Embodiment 1, and a focus light detection part. Configuration diagram of the optical system of the optical pickup device of the second embodiment Configuration diagram of optical pickup device according to Embodiment 2 Configuration diagram of DVD hologram according to the second embodiment Configuration diagram of a hologram for a CD according to the second embodiment Arrangement of the light detection section of the light receiver of the second embodiment Configuration diagram of optical pickup module of Embodiment 3 Configuration diagram of optical disk apparatus according to Embodiment 3 The figure which shows the flow of control of the optical pick-up apparatus of this Embodiment 3. Configuration diagram of optical system of conventional optical pickup device The figure which shows the relationship between the conventional hologram and the light receiver The figure which shows the conventional focus error signal FES by the optical disk with a two-layer information recording surface

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Optical disk 2a, 2b, 2c Information recording surface 2d Surface 3 Hologram 4 Light receiver 4a Focus light detection part 4b Tracking light detection part 4c 1st focus light detection part 4d 2nd focus light detection part 4e 1st tracking light detection Unit 4f second tracking light detection unit 5, 5a, 5b, 5c, 5d spot 6 objective lens 7 light beam 8, 9, 10, 11 stray light spot 12, 13, 14, 15, 16 hologram 17 light receiver 17a focus light detection unit 17b 1st focus light detection part 17c 2nd focus light detection part 18, 18a, 18b Spot 20, 25, 26, 29, 30, 31, 40, 45, 46, 47, 51, 52, 53, 58, 60, 69, 70, 75, 77, 78, 90, 100, 105, 106, 109, 110, 11 Border virtual line 21, 41, 61, 71, 91, 101 Inner area 22, 42, 62, 72, 92, 102 Outer area 23, 43, 63, 73, 93, 103 Focus area 24, 44, 64, 74 , 94, 104 Tracking area 27, 28, 48, 49, 50, 76, 99, 107, 108 Allocation area 32, 54, 65, 79, 95, 112 First focus area 33, 55, 66, 80, 96, 113 Second focus region 34, 56, 67, 81, 97, 114 First tracking region 35, 57, 68, 82, 98, 115 Second tracking region 150 Laser light source 151 Light receiver 151a Focus light detection unit 151b Tracking light detection 151c First focus light detector 151d Second focus light detector 151e First focus Racking light detection unit 151f Second tracking light detection unit 151g, 151h CD tracking light detection unit 151i, 151j, 151k, 151l Photodetection unit 152 Laser module 153 Diffraction element 154 Reflection mirror 155 Collimating lens 156 Rising mirror 157 Hologram 158 Hologram 158a, 158b Boundary virtual lines 158c, 158d Tracking area 158e, 158f, 158g, 158h Focus area 159 1/4 wavelength plate 160 Hologram element 161 Objective lens 162 Front light monitor 163 Optical disk 164 Base 165 Objective lens driving device 165a Lens holder 166 Optical pickup device 166a Laser light source driving power source 167 Cover 170, 171, 172, 173, 174 Spot 17 a, 171a, 172a, 173a, 174a Spot 180, 185, 186, 189, 190, 191 Border virtual line 181 Inner area 182 Outer area 183 Focus area 184 Tracking area 187, 188 Allocation area 192 First focus area 193 Second focus Area 194 First tracking area 195 Second tracking area 200 Optical pickup module 201 Base 202 Spindle motor 203 Feed motor 204 Screw shaft 205, 206 Guide shaft 207 Rack 208 Cover 250 Optical disk apparatus 250a Optical disk apparatus body 250b Analog signal processor 250c Servo processing Unit 250d motor drive unit 250e controller 250f digital signal processing unit 250g The drive unit 251 Case 251a Upper case 251b Lower case 252 Tray 253 Bezel 254 Eject switch 255 Rail 256 External connector 260 Host

Claims (19)

A laser light source that emits light for irradiating the optical disc;
A hologram having a focus region for separating reflected light from the optical disc into focus control light and a tracking region for separating tracking control light;
An objective lens that passes reflected light from the optical disc toward the hologram;
A light receiver having a focus light detection unit that receives the light separated in the focus region and a tracking light detection unit that receives the light separated in the tracking region;
The hologram is characterized in that the inside of a boundary virtual line having a predetermined shape smaller than the outer periphery of the hologram centered on the center of the hologram is the focus region and the outside of the boundary virtual line having the predetermined shape is the tracking region. Optical pickup device. The optical pickup device according to claim 1, wherein the boundary virtual line having the predetermined shape is circular. Of the inner area of the boundary virtual line of the predetermined shape, a predetermined concession area divided by the boundary virtual line of the predetermined shape and the boundary virtual line corresponding to the track longitudinal direction of the optical disc is used as the tracking area. The optical pickup device according to claim 1. 4. The optical pickup according to claim 3, wherein the predetermined assigned area is an area divided by the boundary virtual line having the predetermined shape and at least one boundary virtual line corresponding to a track longitudinal direction of the optical disc. apparatus. 5. The optical pickup device according to claim 4, wherein the predetermined concession area used as the tracking area separates reflected light from the optical disc into light mainly used for the tracking control. The predetermined assigned area is an area including a center of the hologram divided by a boundary virtual line of the predetermined shape and at least two boundary virtual lines corresponding to a track longitudinal direction of the optical disc. The optical pickup device according to claim 3. 7. The optical pickup device according to claim 6, wherein the predetermined concession area used as the tracking area separates reflected light from the optical disk into light used as an auxiliary for the tracking control. The focus area is divided into at least two areas, and the at least two areas are arranged substantially line-symmetrically with a center line of the hologram corresponding to a track longitudinal direction of the optical disc as an axis of symmetry. The optical pickup device according to claim 7. The focus region includes a first focus region that separates light that is focused before entering the focus light detection unit, and a second focus region that separates light that is incident on the focus light detection unit before focusing. The optical pickup device according to claim 1, further comprising: The focus area is divided into a plurality of the first focus areas and a plurality of the second focus areas by boundary virtual lines corresponding to the track longitudinal direction of the optical disc, and the first focus area and the second focus area 10. The optical pickup device according to claim 9, wherein is alternately arranged with a boundary virtual line of a center line corresponding to a track transverse direction orthogonal to the track longitudinal direction. 11. The optical pickup device according to claim 10, wherein the focus light detection unit includes a first focus light detection unit and a second focus light detection unit that are alternately arranged corresponding to the track longitudinal direction. The focus area is divided into a plurality of first focus areas and a plurality of second focus areas by a boundary virtual line corresponding to a track crossing direction orthogonal to the track longitudinal direction of the optical disc, and the first focus areas 10. The optical pickup device according to claim 9, wherein the second focus area and the second focus area are alternately arranged with a boundary virtual line of a center line corresponding to the track longitudinal direction as a boundary. 13. The focus light detection unit is composed of a first focus light detection unit and a second focus light detection unit that are alternately arranged corresponding to a track crossing direction orthogonal to the track longitudinal direction. The optical pickup device described. The tracking region existing outside the boundary imaginary line of the predetermined shape includes a first tracking region that separates reflected light from the optical disc into light mainly used for the tracking control, and reflected light from the optical disc for the tracking control. The optical pickup device according to claim 1, further comprising a second tracking region that separates light used as auxiliary. The tracking region existing outside the boundary imaginary line of the predetermined shape is divided into an end region and a central region along the track longitudinal direction of the optical disc, the end region serving as a first tracking region, and The optical pickup device according to claim 14, wherein the central region is used as a second tracking region. 16. The optical pickup according to claim 15, wherein the first tracking area and the second tracking area are arranged substantially line-symmetrically with a center line corresponding to a track longitudinal direction of the optical disc of the hologram as an axis of symmetry. apparatus. The light source includes a light source that emits two laser beams having different wavelengths, the hologram includes two holograms respectively corresponding to the two laser beams having different wavelengths, and the two holograms are overlapped and integrated. The optical pickup device according to claim 1. The optical pickup device according to claim 17, wherein the two integrated holograms are attached to a lens holder of the objective lens. A laser light source that emits light for irradiating the optical disc;
A hologram having a focus region for separating reflected light from the optical disc into focus control light and a tracking region for separating tracking control light;
An objective lens that passes reflected light from the optical disc toward the hologram;
A light receiver having a focus light detection unit that receives light separated in the focus region and a tracking light detection unit that receives light separated in the tracking region;
The hologram is characterized in that the inside of a boundary virtual line having a predetermined shape smaller than the outer periphery of the hologram centered on the center of the hologram is the focus region and the outside of the boundary virtual line having the predetermined shape is the tracking region. An optical disk device.

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