JP2007335000A - 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 capable of performing stable tracking control by minimizing the effect of a reflected light from an information recording surface other than a predetermined information recording surface. <P>SOLUTION: The optical pickup device is provided with a laser light source 1 for emitting a laser light to the information recording surface 2b of an optical disk 2 having information recording surfaces 2a and 2b, a hologram 3 having a tracking area 3d for converting a reflected light from the information recording surface 2a into a stray light spot 9 of a predetermined projection shape, and an optical receiver 4 having a tracking light detection surface 4a for receiving the condensing spot 5 of a light reflected from the information recording surface 2b and a partial area of the stray light spot 9, and a tracking light detection surface 4b for receiving the other partial area adjacent to the partial area of the stray light spot 9. The tracking light detection surface 4a includes tracking light detection surfaces 4b on both sides. <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, which can record and reproduce information on a plurality of information recording surfaces. The laser light source 101 emits laser light toward the optical disc 107 having a plurality of layers of information recording surfaces 107a and 107b. The reflection mirror 102 bends the optical path of the laser light emitted from the laser light source 101 to reduce the size of the optical pickup device. The collimating lens 103 makes the laser light emitted from the laser light source 101, which is divergent light, substantially parallel light. The rising mirror 104 bends the optical path of the laser light emitted from the laser light source 101 that is substantially parallel to the optical disk 107 at a substantially right angle with respect to the optical disk 107. The hologram element 105 includes a hologram 105a and a quarter-wave plate 105b, and is fixed to the lens holder together with the objective lens 106. The quarter wavelength plate 105b converts the laser light emitted from the laser light source 101, which is P-polarized light, into circularly polarized light, and converts the laser light reflected by the optical disk 107 from circularly polarized light into S-polarized light. The hologram 105a passes the P-polarized laser beam as it is, and diffracts the S-polarized laser beam. The hologram 105a separates the incident light into light used for tracking control and light used for focus control, depending on where it has passed through the hologram 105a. The objective lens 106 is a lens for converging the laser light emitted from the laser light source 101 onto the information recording surfaces 107 a and 107 b of the optical disc 107. The optical disc 107 has an information recording surface 107a on the front side and an information recording surface 107b on the back side. The light receiver 108 has a light detection surface, receives the laser light emitted from the laser light source 101, reflected by the optical disk 107, and passed through the hologram 105a, converts it into an electrical signal, and outputs it. The front light monitor 109 receives a part of the laser light emitted from the laser light source 101, converts it into an electrical signal, and outputs it. The output signal is used for output control of laser light emitted from the laser light source 101.

  FIG. 21 is a diagram showing the relationship between a conventional hologram and a light receiver. The hologram 105a is divided into tracking areas 105c and 105d and focus areas 105e and 105f. The tracking regions 105c and 105d allow a laser beam used for tracking control to pass through. The focus areas 105e and 105f allow a laser beam used for focus control to pass therethrough. The light receiver 108 includes tracking light detection surfaces 108a and 108b. Light incident on the tracking regions 108a and 108b is converted into an electric signal used for tracking control in the light receiver 108 and output. The tracking light detection surface 108 a and the tracking light detection surface 108 b are alternately arranged in a direction corresponding to the tangential direction that is the tangential direction of the circumference of the optical disc 107. When information is recorded on or reproduced from the optical disc 107, the laser light emitted from the laser light source 101 is condensed and reflected on a predetermined information recording surface 107a or information recording surface 107b of the optical disc 107. Then, the laser light that has passed through the tracking region 105c of the hologram 105a enters the tracking light detection surface 108a of the light receiver 108 as a spot 110. The laser light that has passed through the tracking region 105d enters the tracking light detection surface 108b as a spot 111. When the output from the tracking light detection surface 108a is IE and the output from the tracking light detection surface 108b is IF, the tracking error signal TES used for tracking control is expressed by TES = IE-IF.

FIG. 22 is a diagram showing a state in which reflected light from an information recording surface other than a predetermined information recording surface of an optical disc enters a conventional light receiver. When the laser light emitted from the laser light source 101 is condensed and reflected on the predetermined information recording surface 107a of the optical disc 107, the laser light is also reflected on the information recording surface 107b that is not the predetermined information recording surface 107a. Then, the light passes through the tracking regions 105 c and 105 d and enters the light receiver 108 as a stray light spot 112. Further, when the laser light emitted from the laser light source 101 is condensed and reflected on the predetermined information recording surface 107b of the optical disc 107, the laser light is also reflected on the information recording surface 107a that is not the predetermined information recording surface 107b. Then, the light passes through the tracking regions 105 c and 105 d and enters the light receiver 108 as a stray light spot 113. Such stray light spots 112 and 113 affect the tracking error signal TES as an offset component. However, a large number of tracking light detection surfaces 108a and tracking light detection surfaces 108b are arranged in a direction corresponding to the tangential direction to cancel each other, thereby minimizing the influence. The concept of offsetting the tracking error signal TES by canceling the output of the stray light spot on the light detection surface in this way is also described in (Patent Document 1).
JP 2005-346882 A

  However, when there are variations in the thickness, refractive index, etc. of the optical disk, the stray light spot caused by the light passing through a position far from the center of the hologram tends to vary in the position incident on the light receiver. In addition, when recording is performed on the information recording surface on the front side of the optical disk and recording is subsequently started on the information recording surface on the back side, the light from the information recording surface other than the predetermined information recording surface incident on the hologram is unenhanced. It may have a balanced distribution. In such a case, an offset may remain in the tracking error signal TES without completely canceling out the output due to the stray light spot.

  Accordingly, the present invention provides an optical pickup device and an optical disc device that can solve the above-described conventional problems and can perform stable tracking control by minimizing the influence of reflected light from information recording surfaces other than a predetermined information recording surface. The purpose is to provide.

  To achieve the above object, the present invention provides a laser light source that emits laser light to a predetermined information recording surface of an optical disc having a plurality of information recording surfaces, and information other than the predetermined information recording surface of the optical disc that has passed therethrough. A hologram having a tracking region that makes reflected light from the recording surface a predetermined projection shape, and a part of the reflected light that receives the reflected light from the predetermined information recording surface of the optical disc and has the predetermined projection shape A first light detection surface that receives the region and a second light detection surface that receives the other partial region that is included in the same reflected light and is adjacent to the reflected light of the partial region; The optical pickup device is characterized in that the first photodetection surface is arranged on both sides of the second photodetection surface.

  A received light amount of reflected light from an information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface is incident, and a second light detection surface disposed adjacently The amount of reflected light from the information recording surface other than the predetermined information recording surface received can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset.

  In the optical pickup device of the present invention, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

  According to a first aspect of the present invention, there is provided a laser light source that emits laser light to a predetermined information recording surface of an optical disc having a plurality of information recording surfaces, and an information recording surface other than the predetermined information recording surface of the optical disc that has passed therethrough. A hologram having a tracking region that makes the reflected light of a predetermined projection shape, and a first region that receives reflected light from a predetermined information recording surface of the optical disc and a partial region of the reflected light that has been made a predetermined projection shape A light detector having a second light detection surface for receiving another partial region that is included in the same reflected light and that is adjacent to the reflected light of the partial region. The first light detection surface is an optical pickup device in which the second light detection surfaces are arranged on both sides, respectively.

  A received light amount of reflected light from an information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface is incident, and a second light detection surface disposed adjacently The amount of reflected light from the information recording surface other than the predetermined information recording surface received can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

  A second aspect of the present invention is the optical pickup device according to the first aspect, wherein the second light detection surface does not receive reflected light from a predetermined information recording surface of the optical disk.

  Reflected light from information recording surfaces other than the predetermined information recording surface is incident on both sides of the position where the reflected light from the predetermined information recording surface of the optical disc is incident. Accordingly, by arranging the second light detection surface that does not receive the reflected light from the predetermined information recording surface, the output from the first light detection surface by the reflected light from the information recording surface other than the predetermined information recording surface and the first The output from the two-light detection surface can be canceled with certainty.

  According to a third aspect of the present invention, there is provided an optical pickup device according to the first aspect, wherein a plurality of first light detection surfaces are provided in the light receiver, and the plurality of first light detection surfaces are respectively arranged with the second light detection surfaces on both sides. is there.

  As a result, the output is canceled out between the first light detection surface and the second light detection surface. Therefore, the influence of reflected light from information recording surfaces other than the predetermined information recording surface can be minimized.

  According to a fourth aspect of the present invention, in the first aspect of the invention, the second light detection surface is disposed on both sides of the first light detection surface in a direction corresponding to the tangential direction of the circumference of the optical disc. It is.

  The light from the information recording surface other than the predetermined information recording surface has an unbalanced distribution in many directions in the direction corresponding to the radial direction of the optical disc. Even in such an unbalanced distribution, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface can be stably canceled out. Can do.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the boundary between the first light detection surface and the second light detection surface is provided substantially in the radial direction of the optical disc, and the other end of the second light detection surface is This is an optical pickup device provided substantially parallel to the border.

  Since the area of the first light detection surface that receives the reflected light from the information recording surface other than the predetermined information recording surface and the area of the second light detection surface can be set to a constant ratio, the first light detection can be performed stably. The output from the surface and the output from the second light detection surface can be offset. Further, the light from the information recording surface other than the predetermined information recording surface has an unbalanced distribution in many directions corresponding to the radial direction of the optical disc. Even in such an unbalanced distribution, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface can be stably canceled out. Can do.

  According to a sixth aspect of the present invention, in the first aspect of the invention, the width corresponding to the tangential direction of the circumference of the optical disc on the first light detection surface is a width corresponding to the tangential direction of the circumference of the optical disc on the second light detection surface. This is the optical pickup device as described above.

  The position where the reflected light from the information recording surface other than the predetermined information recording surface is incident is adjacent to the position corresponding to the tangential direction of the circumference of the optical disc from the position where the reflected light from the predetermined information recording surface is incident. To the second light detection surface. Therefore, an effect of canceling out the output from the first light detection surface and the output from the second light detection surface by the reflected light from the information recording surface other than the predetermined information recording surface can be obtained.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the width corresponding to the tangential direction of the circumference of the optical disc on the first light detection surface is a width corresponding to the tangential direction of the circumference of the optical disc on the second light detection surface. It is an optical pickup device that is almost twice as large as the above.

  The position where the reflected light from the predetermined information recording surface is incident is often the center of the first light detection surface in the direction corresponding to the tangential direction of the circumference of the optical disc. Therefore, the widths in the direction corresponding to the tangential direction of the circumference of the optical disc on which the reflected light from the information recording surface other than the predetermined information recording surface is incident on the first light detection surface and the second light detection surface can be made substantially equal. it can. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface can be substantially offset.

  The invention according to claim 8 is the optical pickup device according to claim 1, wherein the output of the light receiver from the first light detection surface and the output of the light receiver from the second light detection surface are subtracted.

  By subtracting, it is possible to cancel the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface.

  A ninth aspect of the present invention is the optical pickup device according to the first aspect of the invention, wherein a plurality of sets of the first light detection surface and the second light detection surface are arranged in a direction corresponding to the radial direction of the optical disk.

  Even if reflected light from an information recording surface other than the predetermined information recording surface is incident on a set of the other first light detection surface and the second light detection surface, it can be canceled similarly. Therefore, the set of the first light detection surface and the second light detection surface can be efficiently arranged, and the necessary area of the light receiver can be reduced.

  A tenth aspect of the invention is an optical pickup device according to the first aspect of the invention, wherein a plurality of sets of first light detection surfaces and second light detection surfaces are arranged in a direction corresponding to a tangential direction of the circumference of the optical disk.

  Even if reflected light from an information recording surface other than the predetermined information recording surface is incident on a set of the other first light detection surface and the second light detection surface, it can be canceled similarly. Therefore, the set of the first light detection surface and the second light detection surface can be efficiently arranged, and the necessary area of the light receiver can be reduced.

  According to an eleventh aspect of the present invention, in the first aspect of the invention, the tracking area at the center of the hologram is divided by a dividing line in a direction corresponding to the tangential direction of the circumference of the optical disc, and the radial width of the optical disc is substantially constant. An optical pickup device.

  The shape of the reflected light from the information recording surface other than the predetermined information recording surface incident on the first light detection surface and the second light detection surface can be rectangular. Therefore, it is possible to stably cancel the output from the first light detection surface and the output from the second light detection surface by the information recording surface other than the predetermined information recording surface.

  According to a twelfth aspect of the present invention, in the first aspect of the invention, the first light detection surface and the second light detection surface each have a first tracking light detection surface and a second tracking light detection surface, and the first light detection surface. The first tracking light detection surfaces of the first light detection surface are arranged on opposite sides of the second tracking light detection surface of the second light detection surface, and the second tracking light detection surface of the first light detection surface is the first of the second light detection surface. This is an optical pickup device in which tracking light detection surfaces are arranged on both sides.

  The arrangement of the tracking light detection surface used for tracking control can be made efficient.

  According to a thirteenth aspect of the present invention, in the twelfth aspect of the invention, the difference between the output of the light receiver from the first tracking light detection surface and the output of the light receiver from the second tracking light detection surface is the tracking control of the optical pickup device. This is an optical pickup device used.

  In tracking control, the output of the light receiver from the first tracking light detection surface and the light receiver from the second tracking light detection surface are canceled out by canceling the output from the first light detection surface and the output from the second light detection surface. This is efficient because it can be shared with the difference between the output and the output.

  The invention of claim 14 is the invention of claim 12, wherein the tracking area has a first tracking area and a second tracking area, and the reflected light from the predetermined information recording surface of the optical disk that has passed through the first tracking area is This is an optical pickup device in which reflected light from a predetermined information recording surface of the optical disk that has entered the first tracking light detection surface and passed through the second tracking region is incident on the second tracking light detection surface.

  Since the reflected light from the predetermined information recording surface of the optical disk that has passed through the predetermined area of the hologram is incident on the first tracking light detection surface and the second tracking light detection surface, a predetermined tracking control signal can be obtained. .

  According to a fifteenth aspect of the present invention, in the fourteenth aspect of the present invention, the hologram is divided into two divided regions approximately in half by a dividing line in a direction corresponding to the tangential direction of the circumference of the optical disc and in the radial direction of the optical disc. The first tracking area is substantially line symmetric with respect to a center line in a direction corresponding to a certain radial direction, and the first tracking area is a direction corresponding to the radial direction of the hologram in the direction corresponding to the radial direction of one divided area and the radial direction of the other divided area. The second tracking area is in the center of the hologram, and the second tracking area is at the periphery of the hologram in the direction corresponding to the radial direction of the other divided area and at the center of the hologram in the direction corresponding to the radial direction of the one divided area Device.

  A signal for tracking control of push-pull can be obtained.

  According to a sixteenth aspect of the present invention, in the fifteenth aspect of the invention, the hologram is further divided into four equal areas with the center line as a dividing line, and the light receiver detects the first tracking light beam every four divided areas. An optical pickup device having a surface and a second tracking light detection surface.

  It is possible to arrange a light detection surface that easily cancels the output due to the stray light spot.

  According to a seventeenth aspect of the present invention, in the first aspect, the optical receiver is used for either the + 1st order light or the −1st order light of the reflected light from the information recording surface of the optical disc that has passed through the hologram. It is.

  The area of the light receiver can be reduced.

  According to an eighteenth aspect of the present invention, in the seventeenth aspect of the invention, the hologram is substantially divided into four divided regions, with a dividing line in the direction corresponding to the tangential direction of the circumference of the optical disk and a dividing line in the direction corresponding to the radial direction of the optical disk. The second light receiver used for the other of the + 1st order light and the −1st order light reflected from the information recording surface of the optical disc that has been divided into four equal parts and passed through the hologram is the third light on which the reflected light that has passed through the hologram is incident. This is an optical pickup device having a detection surface for each divided region.

  Since both the + 1st order light and the −1st order light generated by the hologram are used, the light use efficiency is high, and optimum tracking control is easily obtained.

  According to a nineteenth aspect of the present invention, in the eighteenth aspect of the invention, the third light detection surface has a + 1st order light or a −1st order light reflected from a predetermined information recording surface of the optical disk that has passed through each divided region of the hologram. This is an optical pickup device in which almost all of the other light enters.

  A reproduction signal is obtained from the output of the third light detection surface. Since the third light detection surface captures the laser beam in almost the entire region of the hologram, the reproduction signal jitter is excellent.

  The invention of claim 20 is the invention of claim 18, wherein the light receiver has a focus light detection surface for receiving reflected light from an information recording surface of an optical disk used for focus control of the optical pickup device, This is an optical pickup device having a focus area in which either + 1st order light or −1st order light reflected from a predetermined information recording surface of an optical disc is incident on a focus light detection surface.

  A signal for focus control is also obtained from the light receiver.

  According to a twenty-first aspect of the invention, in the twentieth aspect of the invention, the other of the + 1st order light or the −1st order light reflected from the predetermined information recording surface of the optical disk that has passed through the focus area is incident on the third light detection surface. This is an optical pickup device.

  Since both the ± first-order light reflected from the predetermined information recording surface of the optical disk that has passed through the focus area are used, the light use efficiency is high. Further, the jitter of the reproduction signal is excellent.

  According to a twenty-second aspect of the present invention, in the twentieth aspect, the focus light detection surface is substantially in contact with the first focus light detection surface and the second focus light detection surface in a direction corresponding to the tangential direction of the circumference of the optical disc. This is an optical pickup device arranged in a line.

  A focus control method can be used in which the spot size on the focus light detection surface varies in the focused state of the optical disk.

  According to a twenty-third aspect of the present invention, in the twenty-second aspect of the invention, two sets of focus light detection surfaces are arranged adjacent to each other in a direction corresponding to the tangential direction of the circumference of the optical disc, and correspond to the radial direction of the optical disc of the focus light detection surface. This is an optical pickup device in which the length in the direction in which the light is picked up is equal to or greater than the distance between the centers of the two sets of focus light detection surfaces.

  Even if the spot size on the focus light detection surface fluctuates in the focused state of the optical disc, the third light detection surface is arranged so as not to enter each other's light detection surface, and the spot protrudes from the focus light detection surface. You can avoid it.

  According to a twenty-fourth aspect of the present invention, in the twentieth aspect of the present invention, the focus area is incident on the focus light detection surface before being focused on the reflected light incident on the focus light detection surface after being focused. And an area for generating reflected light.

  It is possible to generate a spot used in a focus control method in which the spot size on the focus light detection surface varies in the focused state of the optical disc.

  According to a twenty-fifth aspect of the present invention, in the twentieth aspect of the present invention, the second laser light source that emits laser light toward the information recording surface of the second optical disk is disposed between the second laser light source and the second optical disk. A diffraction grating that diffracts the laser light emitted from the second laser light source and separates it into a main beam that is zero-order light and a side beam that is ± first-order light, and an information recording surface of the second optical disc. A second hologram having a tracking region that passes through the reflected light and generates light in which at least one of the + 1st order light and the −1st order light is used for tracking control, and has passed through the tracking region of the second hologram Of the reflected light of the + 1st order light or the −1st order light, the side beam enters the fourth light detection surface of the light receiver, and the main beam of the other reflected light enters the third light detection surface. It is a pick-up device.

  Since the side beam does not affect the reproduction signal of the second optical disk, the jitter is excellent. Tracking control using the main beam is resistant to noise. Further, the tracking control signal using the main beam and the side beam is generated purely from the outputs of only the main beam and the side beam, so that it is resistant to noise. Further, since the fourth light detection surface is electrically connected to the first light detection surface and the second light detection surface, respectively, there is no need to provide a new output terminal for tracking control of the second optical disk. Wiring is easy.

  According to a twenty-sixth aspect of the present invention, in the twenty-fifth aspect, the second hologram has a dividing line in a direction corresponding to the tangential direction of the circumference of the second optical disk and a dividing line in a direction corresponding to the radial direction of the second optical disk. The optical pickup device is divided into four divided areas and is divided into approximately four equal parts, and the tracking area is two divided areas separated by a dividing line in a direction corresponding to the tangential direction of the circumference of the second optical disc in the divided area. It is.

  A signal for tracking control can be taken out.

  According to a twenty-seventh aspect of the present invention, in the twenty-sixth aspect, the second hologram passes reflected light from the information recording surface of the second optical disc, and either the + 1st order light or the −1st order light is used for focus control. The optical pickup device has a focus area that generates light to be used, and the focus area is two divided areas other than the tracking area.

  A signal for focus control can be taken out.

  According to a twenty-eighth aspect of the present invention, in the twenty-seventh aspect, the main beam is incident on the focus light detection surface out of the reflected light of either the + 1st order light or the −1st order light that has passed through the focus region of the second hologram. An optical pickup device.

  It is possible to perform focus control of the second optical disk, which is preferably performed only with the main beam.

  According to a twenty-ninth aspect of the present invention, in the twenty-eighth aspect, the focus light detection surface is substantially in contact with the first focus light detection surface and the second focus light detection surface in a direction corresponding to the tangential direction of the circumference of the optical disk. Two sets of focus light detection surfaces are arranged adjacent to each other in a direction corresponding to the tangential direction of the circumference of the optical disc, and the reflected light that has passed through one focus area of the second hologram is incident thereon. An optical pickup whose position on the light detection surface is shifted by one of the first focus light detection surface or the second focus light detection surface from the position on the focus light detection surface where the reflected light that has passed through the focus region of the hologram enters. Device.

  The focus control of both the optical disc and the second optical disc can be performed on the dual focus light detection surface.

  A thirty-third aspect of the invention is the light according to the twenty-seventh aspect, wherein the main beam of the other reflected light of the + 1st order light or the −1st order light that has passed through the focus region of the second hologram is incident on the third light detection surface. It is a pickup device.

  A reproduction signal of the second optical disk can be obtained as an output from the third light detection surface.

  The invention of claim 31 is the invention of claim 30, wherein a plurality of sets of the first light detection surface and the second light detection surface are arranged in a direction corresponding to the radial direction of the optical disk, and the set is tangent to the circumference of the optical disk. The optical pickup device is shifted in a direction corresponding to the direction.

  An information recording surface other than the predetermined information recording surface received by the first light detection surface after realizing that only the main beam of the reflected light from the information recording surface of the second optical disc is incident on the third light detection surface The amount of the reflected light from the light and the amount of the reflected light received from the information recording surface other than the predetermined information recording surface received by the second light detection surface can be set to a stable ratio.

  According to a thirty-second aspect of the present invention, there is provided a laser light source that emits laser light to a predetermined information recording surface of an optical disc having a plurality of information recording surfaces, and reflected light from an information recording surface other than the predetermined information recording surface of the optical disc that has passed therethrough. And a hologram having a tracking region that makes a predetermined projection shape, and a first light detection surface that receives reflected light from a predetermined information recording surface of the optical disc and receives a partial region of the reflected light that has a predetermined projection shape And a second photodetection surface that receives the other partial area that is included in the same reflected light and that is adjacent to the reflected light of the partial area, and a first receiver. Each of the light detection surfaces is an optical disk device including an optical pickup device having a second light detection surface arranged on both sides.

  A received light amount of reflected light from an information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface is incident, and a second light detection surface disposed adjacently The amount of reflected light from the information recording surface other than the predetermined information recording surface received can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

(Embodiment 1)
The first embodiment will be described with reference to the drawings. FIG. 1 is a configuration diagram showing the main part of the optical system of the optical pickup device according to the first embodiment. The laser light emitted from the laser light source 1 is reflected by the optical disk 2, passes through the hologram 3, and enters the light receiver 4.

  The laser light source 1 emits laser light having a predetermined wavelength toward an optical disc 2 having a plurality of information recording surfaces. For example, the laser light source 1 emits a DVD laser beam having a wavelength of about 650 nm, emits a DVD laser beam and a CD laser beam having a wavelength of about 780 nm, and Blu-, which is a next-generation DVD. Including those that emit laser light with a wavelength of about 405 nm used for ray discs and HD-DVDs.

  The optical disk 2 having a plurality of information recording surfaces includes DVDs, Blu-ray Discs that are next-generation DVDs, HD-DVD optical disks, and the like. In the first embodiment, two layers of information recording surfaces 2a and 2b are provided. It was set as the DVD which has. The surface irradiated with the laser beam on the front side was defined as the information recording surface 2a, and the surface irradiated on the far side was defined as the information recording surface 2b.

  The hologram 3 is configured as an aggregate of regions where diffraction gratings are formed. Each region where the diffraction grating is formed is divided by virtual lines called dividing lines. The diffraction grating diffracts light passing therethrough and separates it into zero-order light, ± first-order light, and the like. The amount and direction of the separated light are determined by the wavelength of the light passing therethrough, the refractive index of the diffraction grating, the grating depth, the grating spacing, the grating direction, and the like. In the first embodiment, any one of ± primary lights is used. In addition, the hologram 3 includes a type that reflects light and a type that transmits light. In the first embodiment, either one may be used.

  The hologram 3 includes a dividing line 3a in a direction corresponding to the tangential direction, which is a direction parallel to the tangential direction of the circumference of the optical disc 2, and a dividing line in a direction corresponding to the radial direction, which is a direction parallel to the radial direction of the optical disc 2. Divided into approximately four equal parts by 3b. The tangential and radial directions are based on the position at which the laser beam emitted from the laser light source 1 is incident on the optical disc 2. The dividing line 3a and the dividing line 3b pass through almost the center of the hologram 3, and the hologram 3 is divided into four equal parts into four divided regions. Here, for the sake of simplicity, one divided region 3c out of the four divided regions will be discussed. The divided area 3c includes two types of tracking areas 3d and 3e and a focus area 3f separated by a dividing line in a direction corresponding to the tangential direction. The tracking areas 3d and 3e generate light used for tracking control of the optical pickup device. The focus area 3f generates light used for focus control of the optical pickup device. The tracking region in the peripheral portion in the direction corresponding to the radial direction of the hologram 3 in the divided region 3c is defined as a tracking region 3d, and the tracking region in the central portion in the direction corresponding to the radial direction is defined as a tracking region 3e. The width of the divided region 3c in the direction corresponding to the radial direction of the tracking region 3e is substantially constant. In the divided area 3g, the tracking areas 3d and 3e are distributed symmetrically with the divided area 3c about the dividing line 3b. In the divided areas 3h and 3i, the tracking areas 3d and 3e are distributed in line symmetry with the divided areas 3g and 3c with the dividing line 3a as the axis of symmetry. However, the tracking areas 3d and 3e are switched. That is, the tracking region 3d is located at the periphery of the hologram 3 in the direction corresponding to the radial direction of the divided regions 3d and 3g and at the center of the hologram 3 in the direction corresponding to the radial direction of the divided regions 3h and 3i. The tracking area 3e is at the center of the hologram 3 in the direction corresponding to the radial direction of the divided areas 3d and 3g and at the periphery of the hologram 3 in the direction corresponding to the radial direction of the divided areas 3h and 3i. The tracking regions 3d and 3e are substantially line symmetric with respect to the dividing line 3b. Although the tracking area 3d is the first tracking area and the tracking area 3e is the second tracking area, they may be replaced.

  The light receiver 4 includes a light detection surface that is a photodiode that receives the laser light that has passed through the hologram 3, and converts the light received by the light detection surface into an electrical signal and outputs the electrical signal. The output electric signal is sent to the optical disc apparatus main body and used for tracking control, focus control of the optical pickup device, reproduction of information recorded on the optical disc, and the like. Here, for the sake of simplicity, only the tracking light detection surfaces 4a and 4b that receive light used for tracking control will be discussed. The tracking light detection surfaces 4a and 4b have light detection surfaces corresponding to the divided regions 3c, 3g, 3h and 3i. There are a plurality of tracking light detection surfaces 4a corresponding to the divided regions 3c, 3g, 3h, and 3i, and each of them is electrically connected. Similarly, there are a plurality of tracking light detection surfaces 4b, and each is electrically connected. Therefore, if light enters one of the tracking light detection surfaces 4a, it is converted into an electrical signal and output from the light receiver 4. If light enters two or more tracking light detection surfaces 4a, the total amount of received light is converted into an electrical signal and output from the light receiver 4. The same applies to the tracking light detection surface 4b. The tracking error signal TES, which is a signal for tracking control, is calculated by TES = IE−IF, where IE is the output from the tracking light detection surface 4a and IF is the output from the tracking light detection surface 4b. can get.

  Consider a case where information is recorded or reproduced by condensing laser light on a predetermined information recording surface of either the information recording surface 2a or the information recording surface 2b of the optical disc 2. The laser beam condensed and reflected by a predetermined information recording surface of the optical disc 2 and passed through the tracking region 3d of the hologram 3 is substantially condensed and incident on one of the tracking light detection surfaces 4a. This condensing spot is the condensing spot 5. Further, the laser beam condensed and reflected by a predetermined information recording surface and passing through the tracking region 3e of the hologram 3 is almost condensed and incident on one of the tracking light detection surfaces 4b. This condensing spot is the condensing spot 6. The condensing spot 5 and the condensing spot 6 may be reversed. The positions of the focused spot 5 and the focused spot 6 in the direction corresponding to the tangential direction are substantially the same. A rectangular tracking light detection surface 4b is arranged on both sides in a direction corresponding to the tangential direction of the rectangular tracking light detection surface 4a where the condensed spot 5 is located. The tracking light detection surface 4b does not have a focused spot that has passed through the tracking region 3d. In addition, rectangular tracking light detection surfaces 4a are arranged on both sides of the direction corresponding to the tangential direction of the rectangular tracking light detection surface 4b where the condensing spot 6 is located. The tracking light detection surface 4a does not have a focused spot that has passed through the tracking region 3e. The tracking light detection surface 4a with the condensing spot 5 and the tracking light detection surface 4b with the condensing spot 6 are the first light detection surfaces. The tracking light detection surface 4b on both sides of the tracking light detection surface 4a with the condensing spot 5 and the tracking light detection surface 4a on both sides of the tracking light detection surface 4b with the condensing spot 6 are the second light detection surfaces. . The tracking light detection surface 4a is a first tracking light detection surface, and the tracking light detection surface 4b is a second tracking light detection surface. The first tracking light detection surface and the second tracking light detection surface may be interchanged. However, the condensed spot 6 by the second tracking region is on the second tracking light detection surface so that the condensed spot 5 by the first tracking region is on the first tracking light detection surface. Further, the tracking light detection surface 4a with the condensing spot 5 and the tracking light detection surface 4b with the condensing spot 6 are arranged side by side in a direction corresponding to the radial direction. A set of tracking light detection surfaces on which laser light that has passed through other divided regions is incident are further arranged side by side in a direction corresponding to the radial direction. That is, the positions in the direction corresponding to the tangential direction of the condensed spots from the other divided regions are the same as those of the condensed spots 5 and 6. This configuration is a configuration in which a plurality of sets of first light detection surfaces and second light detection surfaces are arranged in a direction corresponding to the radial direction. Also, obtaining a tracking control signal results in subtraction between the output from the first light detection surface and the output from the second light detection surface.

  FIG. 2 is an enlarged view of the tracking light detection surface of the first embodiment. Each of the tracking light detection surfaces 4a and 4b has an edge portion extending in a direction corresponding to the radial direction. That is, the boundary between the tracking light detection surface 4a and the tracking light detection surface 4b is provided in a direction substantially corresponding to the radial direction, and the opposite side is provided parallel to the boundary. Further, it is desirable that the focused spots 5 and 6 are located at the center of the tracking light detection surfaces 4a and 4b. If the condensing spots 5 and 6 protrude from the predetermined tracking light detection surfaces 4a and 4b, a part of necessary information is lost, but the condensing spots 5 and 6 are in the center of the tracking light detection surfaces 4a and 4b. It is because it becomes difficult to protrude by making it exist. The width in the direction corresponding to the tangential direction of the tracking light detection surface 4a where the condensed spot 5 is located is 2A, and the width in the direction corresponding to the tangential direction of the tracking light detection surface 4b adjacent to the direction corresponding to the tangential direction. A. In this case, the distance from the center of the focused spot 5 to the edge of the tracking light detection surface 4a is substantially A. Similarly, the width of the direction corresponding to the tangential direction of the tracking light detection surface 4b where the condensed spot 6 is located is 2A, and corresponds to the tangential direction of the tracking light detection surface 4a adjacent to the direction corresponding to the tangential direction. The width in the direction to be taken was A.

  Next, when information is recorded or reproduced by condensing the laser beam on one of the information recording surface 2a and the information recording surface 2b of the optical disc 2, information other than the predetermined information recording surface is used. Consider the reflected light from the information recording surface. FIG. 3 is a diagram showing a state of reflected light from the information recording surface on the back side when focusing on the information recording surface on the near side of the optical disc of the first embodiment, and FIG. 4 is a diagram of the optical disc of the first embodiment. It is a figure which shows the mode of the reflected light from the information recording surface of the near side at the time of condensing on the information recording surface of the back side.

  In FIG. 3, the laser light emitted from the laser light source 1 is condensed and reflected on the information recording surface 2 a on the near side of the optical disc 2, passes through the hologram 3, and enters the light receiver 4. At this time, a part of the laser light incident on the optical disk 2 is transmitted through the information recording surface 2 a, reflected by the information recording surface 2 b, transmitted again through the information recording surface 2 a, passed through the hologram 3, and further received by the light receiver 4. Incident. Since the laser beam is incident on the information recording surface 2a in a focused state, the laser beam is incident on the information recording surface 2b without being focused. Therefore, the laser beam reflected by the information recording surface 2b is output as an offset component when entering the tracking light detection surfaces 4d and 4e.

  Unlike the focused spots 5 and 6, the laser beam reflected on the information recording surface 2 b in a non-focused state is incident on the light receiver 4 without being focused. Moreover, it enters the light receiver 4 as a projected stray light spot 7 reflecting the shape of the tracking region 3a of the hologram 3 and a projected stray light spot 8 reflecting the shape of the tracking region 3b. When the information recording surface 2b approaches the position of the information recording surface 2a, the stray light spot 7 approaches the position and size of the focused spot 5. Similarly, when the information recording surface 2b approaches the position of the information recording surface 2a, the stray light spot 8 also approaches the position and size of the focused spot 6. That is, when the stray light spots 7 and 8 pass near the center of the hologram 3, the positions of the stray light spots 7 and 8 are close to the positions of the condensing spots 5 and 6, and even if there are variations in the optical disc 2, the positions thereof are not easily changed. On the contrary, when the stray light spots 7 and 8 pass far from the center of the hologram 3, if there are variations in the optical disc 2 or the like, and the position of the optical disc 2 varies, the position varies greatly. In other words, the stray light spots 7 and 8 are distributed reflecting the fan-shaped shape of the divided region 3c, and the condensing spots 5 and 6 are located at the main positions of the fan-shaped. The stray light spots 7 and 8 located near the condensed spots 5 and 6 do not change much even if there are variations in the optical disk 2, but the stray light spots 7 and 8 located far from the condensed spots 5 and 6. 8 has a large variation in position. Further, the stray light spots 7 and 8 from the position close to the dividing line 3a are almost unchanged in the direction corresponding to the tangential direction, and the stray light spots 7 and 8 from the position close to the dividing line 3b correspond to the radial direction. The position in the direction is almost unchanged.

  In FIG. 3, the stray light spot 7 does not cover the tracking light detection surfaces 4a and 4b at all. The stray light spot 8 is also slightly applied to the tracking light detection surfaces 4a and 4b. In this manner, if the stray light spots 7 and 8 do not reach the tracking light detection surfaces 4a and 4b, no offset component is generated in the first place, so that a good tracking control signal can be obtained. Even when it takes a little time, since the offset component is small from the beginning, a good tracking control signal can be obtained.

  In FIG. 3, the stray light spot 7 does not cover the tracking light detection surfaces 4a and 4b at all, and the stray light spot 8 takes a little. However, when there are variations in the thickness, refractive index, etc. of the optical disk 2, both may take a little or neither. Further, depending on the design, the stray light spot 7 may be slightly applied and the stray light spot 8 may not be applied at all.

  On the other hand, in FIG. 4, the stray light spots 9 and 10 are on the tracking light detection surfaces 4a and 4b. When the laser light emitted from the laser light source 1 is collected and reflected on the information recording surface 2b on the back side of the optical disk 2 to record or reproduce information, a part of the laser light is on the information recording surface 2a on the front side. The reflected light passes through the hologram 3 and enters the light receiver 4. The stray light spot 9 is a spot formed by light that has passed through the tracking region 3 d of the hologram 3. Similarly, the stray light spot 10 is a spot formed by light that has passed through the tracking region 3e. The stray light spots 9 and 10 are point-symmetric with the stray light spots 7 and 8 with the focused spots 5 and 6 as the center. Other than that, it has the same properties as the stray light spots 7 and 8.

  The stray light spot 9 is incident on the tracking light detection surface 4a on which the condensed spot 5 from the other divided region 3i is incident and the tracking light detection surface 4b adjacent thereto. The end portion of the stray light spot 9 in the direction corresponding to the tangential direction corresponds to the dividing line 3b in the direction corresponding to the radial direction which is substantially the center line of the hologram 3, and the direction corresponding to the tangential direction of the focused spot 5 Is almost equal to the position of That is, it is substantially the center of the direction corresponding to the tangential direction of the tracking light detection surface 4a. One of the end portions of the stray light spot 9 in the direction corresponding to the radial direction corresponds to a dividing line in the direction corresponding to the tangential direction of the tracking region 3e of the hologram 3, and extends in the direction corresponding to the tangential direction. The other end of the stray light spot 9 in the direction corresponding to the radial direction is the outer edge of the end of the hologram 3 in the direction corresponding to the radial direction, and extends in a direction substantially corresponding to the tangential direction. Therefore, the shape of the stray light spot 9 on the tracking light detection surfaces 4a and 4b is almost rectangular. As described above, the length of the stray light spot 9 in the direction corresponding to the tangential direction applied to the tracking light detection surface 4a is A, and the length in the direction corresponding to the tangential direction applied to the tracking light detection surface 4b is also set. A, and the rectangular areas are equal. If the stray light spot 9 has a substantially uniform light amount distribution in the range of the tracking light detection surfaces 4a and 4b, the light amounts received by the tracking light detection surface 4a and the tracking light detection surface 4b are substantially equal. As described above, since the tracking control signal is the difference between the output from the tracking light detection surface 4a and the output from the tracking light detection surface 4b, the offset component of the tracking control signal is almost zero.

  When there is a variation in the optical disc 2 or the like, the position of the end portion in the direction corresponding to the tangential direction of the stray light spot 9 hardly moves because it is close to the dividing line 3b. Even if the position of the end portion in the direction corresponding to the radial direction of the stray light spot 9 changes, the area of the stray light spot 9 applied to the tracking light detection surface 4a and the area of the stray light spot 9 applied to the tracking light detection surface 4b remain substantially equal. It is. Therefore, the output from the tracking light detection surface 4a and the output from the tracking light detection surface 4b remain substantially equal, and the offset component of the tracking control signal also remains substantially zero.

  The same applies to the case of the stray light spot 10. The end of the stray light spot 10 in the direction corresponding to the tangential direction is substantially the same as the position of the focused spot 6 in the direction corresponding to the tangential direction, and extends in the direction corresponding to the radial direction. Further, the position hardly changes even if there are variations in the optical disk 2 or the like. The end in the direction corresponding to the radial direction corresponds to a dividing line in the direction corresponding to the tangential direction with the tracking region 3d or the focus region 3f of the hologram 3, and extends in the direction corresponding to the tangential direction. Therefore, the sum total of the rectangular areas of the stray light spot 10 on the tracking light detection surface 4a is substantially equal to the sum of the rectangular areas of the stray light spot 10 on the tracking light detection surface 4b. Since the light quantity distribution of the stray light spot 10 incident on the adjacent tracking light detection surfaces 4a and 4b is considered to be substantially uniform, the light reception amount of the tracking light detection surface 4a and the light reception amount of the tracking light detection surface 4b by the stray light spot 10 are Almost equal. Accordingly, since the tracking control signal is the difference between the output from the tracking light detection surface 4a and the output from the tracking light detection surface 4b, the offset component of the tracking control signal is almost zero. The result is the same even if there are variations in the optical disk 2.

  Even if the division specification of the hologram 3 is changed and the stray light spot 7 is applied to the tracking light detection surfaces 4a and 4b, the shape thereof is substantially rectangular when similarly considered. Further, even if the stray light spot 8 falls on the tracking light detection surfaces 4a and 4b, the shape thereof is substantially rectangular. One of the sides where the stray light spots 7, 8, 9, 10 extend in the direction corresponding to the rectangular radial direction on the tracking light detection surfaces 4 a, 4 b is the position in the direction corresponding to the tangential direction of the focused spots 5, 6. It is almost the same position. The other is an edge portion extending in a direction corresponding to the radial direction of the tracking light detection surfaces 4a and 4b. The width in the direction corresponding to the tangential direction of the rectangle formed by the stray light spots 7, 8, 9, 10 applied to the tracking light detection surface 4 a is A. Further, the width in the direction corresponding to the rectangular tangential direction formed by the stray light spots 7, 8, 9, 10 applied to the tracking light detection surfaces 4b arranged in the direction corresponding to the tangential direction is also A. Therefore, the area of the two rectangles is always equal. For this reason, the tracking control signal is the difference between the output from the tracking light detection surface 4a and the output from the tracking light detection surface 4b, and is offset to make the offset component of the tracking control signal almost zero.

  Assume that the tracking light detection surfaces 4b and 4a are not arranged on both sides of the direction corresponding to the tangential direction of the tracking light detection surfaces 4a and 4b where the focused spots 5 and 6 are located. The outputs from the tracking light detection surface 4a and the outputs from the tracking light detection surface 4b by the respective stray light spots 7, 8, 9, 10 are not canceled out. Therefore, the output from the tracking light detection surface 4a and the output from the tracking light detection surface 4b due to the stray light spots 7, 8, 9, and 10 as a whole are not necessarily offset finally.

  If the tracking light detection surface 4b disposed on both sides of the tracking light detection surface 4a where the light collection spot 5 is present has the light collection spots 6, the tracking light detection surface 4a, the tracking light detection surface 4b, Does not cancel out the output. Therefore, the focused spots 5 and 6 are prevented from entering the outermost tracking light detection surfaces 4a and 4b. That is, the reflected light from the predetermined information recording surface can be surely canceled by preventing the reflected light from entering the outermost second light detection surface.

  In addition, when there are a plurality of first light detection surfaces, the plurality of first light detection surfaces must be respectively provided with the second light detection surfaces on both sides. This is because the output of the first light detection surface on which the second light detection surface is not arranged is not canceled by the second light detection surface.

  As described above, it is important that the ratio of the areas of the stray light spots 7, 8, 9, 10 to the tracking light detection surfaces 4 a, 4 b is constant, if possible. For this purpose, the shape of the stray light spots 7, 8, 9, 10 on the tracking light detection surfaces 4a, 4b may be rectangular. For this purpose, it is effective that the tracking light detection surfaces 4a and 4b have edge portions extending in a direction corresponding to the radial direction. In addition, it is effective that the width of the tracking region 3d and the tracking region 3e in the direction corresponding to the radial direction is constant within the range where the stray light spots 7, 8, 9, and 10 are applied to the tracking regions 3d and 3e. For this purpose, it is desirable that the tracking areas 3d and 3e and the focus area 3f be separated by a dividing line in a direction corresponding to the tangential direction. In addition, the tracking region 3d and the tracking region 3e are divided in the direction corresponding to the tangential direction except for the peripheral portion in the direction corresponding to the radial direction at the central portion in the direction corresponding to the tangential direction of the hologram 3. It is desirable to separate them with

  Further, in the first embodiment, the width corresponding to the tangential direction of the tracking light detection surfaces 4a and 4b where the focused spots 5 and 6 are located is twice the width of the tracking light detection surfaces 4b and 4a arranged on both sides. It was. By making it approximately twice, the areas of the stray light spots 7, 8, 9, 10 on the tracking light detection surfaces 4a, 4b can be made substantially equal. The width of the tracking light detection surfaces 4b and 4a arranged on both sides has a width corresponding to the tangential direction of the tracking light detection surfaces 4a and 4b where the converging spots 5 and 6 are provided even if the width approximately twice is not secured. By setting it as the above, the effect which cancels is acquired.

  Further, the positions of the focused spot 5 and the focused spot 6 in the direction corresponding to the tangential direction are the same. Therefore, it becomes easy to arrange the tracking light detection surfaces 4a and 4b so that the stray light spots 7, 8, 9, and 10 have the same area on the tracking light detection surfaces 4a and 4b. Further, the positions in the direction corresponding to the tangential direction of the condensed spots from the other divided regions were also made the same as the condensed spots 5 and 6. That is, a plurality of sets of the first light detection surface and the second light detection surface are arranged in a direction corresponding to the radial direction of the optical disk. As a result, it becomes easy to arrange the tracking light detection surfaces 4a and 4b so that the stray light spots 7, 8, 9, and 10 have the same area on the tracking light detection surfaces 4a and 4b. That is, even when reflected light from an information recording surface other than a predetermined information recording surface is incident on a set of another first light detection surface and second light detection surface, it can be canceled in the same manner. Therefore, the set of the first light detection surface and the second light detection surface can be efficiently arranged, and the required area of the light receiver 4 can be reduced.

  As described above, the optical system of the optical pickup device according to the first embodiment makes the output from the tracking light detection surfaces 4a and 4b by the stray light spots 7, 8, 9, and 10 almost zero or cancels and almost zeros. Can be.

  Further, the optical system of the optical pickup device according to the first embodiment has a tracking that is likely to occur immediately after recording from the inner periphery to the outer periphery on the information recording surface 2a of the optical disc 2 and then moving to the information recording surface 2b and starting recording. The offset of the control signal can also be reduced. FIG. 5A is a diagram showing the situation of the optical disc when recording is performed on the information recording surface on the front side of the first embodiment, and FIG. 5B is an information recording surface on the front side of the first embodiment. It is a figure which shows the condition of the optical disk at the time of starting recording on the information recording surface of the back side after recording. FIG. 6A shows the reflected light of the laser beam from the near-side information recording surface immediately after recording on the near-side information recording surface after recording on the near-side information recording surface of the first embodiment. FIG. 6B is a diagram showing the situation, FIG. 6B is a diagram when a laser beam is irradiated on the information recording surface on the back side from a region slightly entering the recording area of the information recording surface on the near side, and FIG. FIG. 6 (d) shows the state of the hologram at the time of FIG. 6 (b) when the laser beam is irradiated to the information recording surface on the back side from the region completely entering the recording area of the information recording surface on the near side. FIG. FIG. 7 is a diagram showing a state of reflected light on the light receiver of the first embodiment in the case of FIG.

  Normally, when recording on the optical disc 2 having the information recording surfaces 2a and 2b, the recording proceeds from the inner periphery of the information recording surface 2a on the front side, and after recording to the outermost recordable surface, the information recording surface 2b on the back side is recorded. The focal point is jumped, and recording is advanced again from the outermost periphery side of the information recording surface 2b toward the inner periphery. While recording is proceeding to the information recording surface 2a, the reflected light from the information recording surface 2b that is not in focus is half the recording area 2c on the inner information recording surface 2a and half the unrecorded area 2d on the outer periphery side. Contains. The reflectance of the recording area 2c is different from the reflectance of the unrecorded area 2d, and its boundary line extends in a direction corresponding to the tangential direction.

  Immediately after finishing recording on the information recording surface 2a and jumping to the information recording surface 2b, as shown in FIG. 6A, the reflected light 11a from the information recording surface 2a in the out-of-focus state is the information on the inner circumference side. The distribution includes half of the reflected light 11b from the recording area 2c of the recording surface 2a and half of the reflected light 11c from the unrecorded area 2d on the outer peripheral side. The boundary line 11d is a direction in a direction corresponding to the tangential direction. Next, when recording is started to the inner peripheral side, as shown in FIG. 6B, the distribution of the reflected light 11a from the information recording surface 2a is increased by the amount of the reflected light 11b from the recording area 2c on the inner peripheral side. The amount of reflected light 11c from the unrecorded area 2d on the side decreases. Even in this case, the boundary line 11d extends in a direction corresponding to the tangential direction. When recording further proceeds toward the inner periphery, the reflected light 11a from the information recording surface 2a has a uniform distribution of only the reflected light 11b from the recording area 2c, as shown in FIG. 6C. When the laser beam 11a having the distribution shown in FIG. 6B is incident on the hologram 3, the boundary line 11d between the recording area 2c and the unrecorded area 2d shown by the broken line in FIG. 6B is shown in FIG. It becomes a broken line in a direction corresponding to the tangential direction.

  The broken line in the direction corresponding to the tangential direction of the stray light spot 10 shown in FIG. 7 corresponds to the boundary line 11d between the recording area 2c and the unrecorded area 2d. That is, the stray light spot 10 above the broken line in FIG. 7 is a spot of reflected light from the recording area 2c of the information recording surface 2a, and the stray light spot 10 below is from the unrecorded area 2d of the information recording surface 2a. It is a spot of reflected light. The area of the tracking light detection surface 4a to which the stray light spot 10 of the reflected light from the recording area 2c of the information recording surface 2a is substantially equal to the area of the tracking light detection surface 4b. Therefore, the output from the tracking light detection surface 4a by the stray light spot 10 of the reflected light from the recording area 2c of the information recording surface 2a and the output from the tracking light detection surface 4b can be made almost equal. Similarly, the areas of the tracking light detection surface 4a and the tracking light detection surface 4b to which the stray light spot 10 of the reflected light from the unrecorded area 2d of the information recording surface 2a is substantially equal. Therefore, the output from the tracking light detection surface 4a by the stray light spot 10 of the reflected light from the unrecorded area 2d of the information recording surface 2a and the output from the tracking light detection surface 4b can be made almost equal. Eventually, in this case as well, the outputs from the tracking light detection surfaces 4a and 4b by the stray light spots 9 and 10 can be canceled out to almost zero.

  As described above, in the optical pickup device according to the first embodiment, the reflected light from the information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface is incident. The amount of received light and the amount of received light reflected from information recording surfaces other than the predetermined information recording surface received by the adjacent second light detection surface can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

(Embodiment 2)
The second embodiment will be described with reference to the drawings. FIG. 8A is an enlarged view of the tracking light detection surface of the second embodiment, and FIG. 8B is a view showing the state of light that has passed through the hologram. The optical pickup device of the second embodiment is different from the optical pickup device of the first embodiment in the arrangement of the light detection surfaces of the light receiver. In addition, the arrangement of the four divided areas, the tracking area, and the focus area of the hologram is the same as that in the first embodiment, but the grating spacing of the diffraction grating in the tracking area, the grating is changed in accordance with the change in the arrangement of the light detection surface. Is different from that of the first embodiment. Since other than that is the same as Embodiment 1, the description is used.

  In the second embodiment, a case is considered where information is recorded or reproduced by condensing laser light on a predetermined information recording surface of either the information recording surface 2a or the information recording surface 2b of the optical disc 2. Reflected light from a predetermined information recording surface of the optical disk 2 that has passed through the tracking region 21a of the hologram 21 forms a condensed spot 22 on the tracking light detection surface 20a. Further, the reflected light from the predetermined information recording surface of the optical disk 2 that has passed through the tracking region 21b of the hologram 21 forms a condensed spot 23 on the tracking light detection surface 20b. The condensing spot 22 and the condensing spot 23 are arranged side by side in a direction corresponding to the tangential direction. The tracking areas 21a and 21b of the hologram 21 correspond to the tracking areas 3d and 3e of the hologram 3 of the first embodiment, respectively. That is, the tracking area 21a is a first tracking area, and the tracking area 21b is a second tracking area. The tracking light detection surfaces 20a and 20b correspond to the tracking light detection surfaces 4a and 4b of the first embodiment, respectively. That is, the tracking light detection surface 20a is a first tracking light detection surface, and the tracking light detection surface 20b is a second tracking light detection surface. In addition, the tracking light detection surfaces 20a and 20b on which the focused spots 22 and 23 are formed are arranged adjacent to each other in a direction corresponding to the tangential direction. A tracking light detection surface 20b that does not receive the condensed spot is disposed on the opposite side of the tracking light detection surface 20b that receives the condensed spot 23 of the tracking light detection surface 20a that receives the condensed spot 22. Further, a tracking light detection surface 20a that does not receive the condensing spot 22 is disposed on the opposite side of the tracking light detection surface 20a that receives the condensing spot 22 of the tracking light detection surface 20b that receives the condensing spot 23. The tracking light detection surface 20a that receives the condensed spot 22 is a first light detection surface, and the tracking light detection surfaces 20b on both sides thereof are second light detection surfaces. Further, the tracking light detection surface 20b that receives the condensed spot 23 is a first light detection surface, and the tracking light detection surfaces 20a on both sides are second light detection surfaces. Accordingly, the tracking light detection surface 20a that receives the condensed spot 22 and the tracking light detection surface 20b that receives the condensed spot 23 are both the first light detection surface and the second light detection surface. These tracking light detection surfaces 20a and 20b have edge portions extending in a direction corresponding to the radial direction. The focused spots 22 and 23 are substantially at the center in the direction corresponding to the tangential direction of the tracking light detection surfaces 20a and 20b, respectively. The width in the direction corresponding to the tangential direction of the tracking light detection surfaces 20a and 20b that receive the focused spots 22 and 23 is 2B, and the width in the direction corresponding to the tangential direction of the tracking light detection surfaces 20a and 20b on both sides is B. It was. The distance from the center of the condensing spots 22 and 23 to the edge portions of the tracking light detection surfaces 20a and 20b where the condensing spots 22 and 23 are located is approximately B. On the contrary, if the distance between the condensing spot 22 and the condensing spot 23 is 2B, which is the width in the direction corresponding to the tangential direction of the tracking light detection surfaces 20a and 20b where the condensing spots 22 and 23 are located. For example, the tracking light detection surface can be arranged.

  When condensing the laser beam on the information recording surface 2a on the front side of the optical disc 2, the light reflected by the information recording surface 2b on the back side and passing through the tracking regions 21a and 21b of the hologram 21 passes the stray light spots 24 and 25, respectively. It is formed on the light receiver 20. Since the stray light spots 24 and 25 hardly reach the tracking light detection surfaces 20a and 20b, the outputs from the tracking light detection surfaces 20a and 20b by the stray light spots 24 and 25 are almost zero, respectively.

  When condensing a laser beam on the information recording surface 2b on the back side of the optical disc 2, the light reflected by the information recording surface 2a on the near side and passing through the tracking regions 21a and 21b of the hologram 21 is caused to have stray light spots 26 and 27, respectively. It is formed on the light receiver 20. The stray light spot 27 hardly covers the tracking light detection surfaces 20a and 20b. The stray light spot 26 is applied to a pair of adjacent tracking light detection surfaces 20a and 20b that receive light that has passed through the tracking areas of other divided areas. The area of the stray light spot 26 on the tracking light detection surface 20a is substantially equal to the area of the tracking light detection surface 20b. Therefore, the output from the tracking light detection surface 20a by the stray light spots 26 and 27 and the output from the tracking light detection surface 20b are almost equal and cancel each other.

  In the second embodiment, the stray light spots 24 and 25 are hardly applied to the tracking light detection surfaces 20a and 20b, but the case where the stray light spots 24, 25, 26 and 27 are applied to the tracking light detection surfaces 20a and 20b is considered. When the stray light spot 24 is applied to the tracking light detection surfaces 20a and 20b, the stray light spot 24 is applied to the right side of the condensing spot 22 in a substantially rectangular shape. The total width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20a is 2B, and the width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20b is also 2B. Therefore, the area of the stray light spot 24 on the tracking light detection surface 20a is substantially equal to the area of the tracking light detection surface 20b. Further, when the stray light spot 25 is applied to the tracking light detection surfaces 20a and 20b, it is applied in a substantially rectangular shape to the right side of the focused spot 23 on the paper surface. The width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20a is B, and the width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20b is also B. Therefore, the area of the stray light spot 25 on the tracking light detection surface 20a is substantially equal to the area of the tracking light detection surface 20b.

  On the other hand, when the stray light spot 26 is applied to the tracking light detection surfaces 20a and 20b, it is applied in a substantially rectangular shape to the left side of the condensing spot 22 above the paper surface. The width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20a is B, and the width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20b is also B. Accordingly, the area of the stray light spot 26 on the tracking light detection surface 20a is substantially equal to the area of the tracking light detection surface 20b. Further, when the stray light spot 27 is applied to the tracking light detection surfaces 20a and 20b, it is applied in a substantially rectangular shape on the left side of the light condensing spot 23 above the paper surface. The width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20a is 2B, and the total width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20b is also 2B. Therefore, the area of the stray light spot 27 on the tracking light detection surface 20a is substantially equal to the area of the tracking light detection surface 20b.

  Let us consider a case in which there are no tracking light detection surfaces 20a, 20b that are not covered by the condensing spots 22, 23. The width of the stray light spot 24 in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20a is B, and the width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 20b is 2B. For this reason, the area of the stray light spot 24 on the tracking light detection surface 20a is not equal to the area of the tracking light detection surface 20b. Similarly, the area of the stray light spots 25, 26, 27 on the tracking light detection surface 20a is not equal to the area of the tracking light detection surface 20b. Therefore, the output from the tracking light detection surface 20a and the output from the tracking light detection surface 20b due to the stray light spots 25, 26, 27, and 28 as a whole are not necessarily offset finally.

  As described above, the optical system of the optical pickup apparatus according to the second embodiment makes the output from the tracking light detection surfaces 20a and 20b by the stray light spots 24, 25, 26, and 27 almost zero or cancels and almost zeros. Can be. That is, even when reflected light from an information recording surface other than the predetermined information recording surface is incident on a set of the other first light detection surface and the second light detection surface, it can be canceled similarly. Therefore, the set of the first light detection surface and the second light detection surface can be efficiently arranged, and the necessary area of the light receiver can be reduced.

  Therefore, in the optical pickup device of the second embodiment, the received light amount of the reflected light from the information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface enters. The amount of reflected light from the information recording surface other than the predetermined information recording surface received by the adjacent second light detection surfaces can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

(Embodiment 3)
The third embodiment will be described with reference to the drawings. FIG. 9A is an enlarged view of the tracking light detection surface of the third embodiment, and FIG. 9B is a diagram showing the state of light that has passed through the hologram. The optical pickup device of the third embodiment differs from the optical pickup devices of the first and second embodiments in the arrangement of the light detection surfaces of the light receiver. The arrangement of the four divided areas, the tracking area, and the focus area of the hologram is the same as in the first and second embodiments, but the diffraction grating in the tracking area is changed in accordance with the change in the arrangement of the light detection surface. Are different from those in the first and second embodiments. Since other than that is the same as Embodiment 1, the description is used.

  In the third embodiment, consider a case where information is recorded or reproduced by condensing laser light on a predetermined information recording surface of either the information recording surface 2a or the information recording surface 2b of the optical disc 2. Reflected light from a predetermined information recording surface of the optical disc 2 that has passed through the tracking region 31a of the hologram 31 forms a condensing spot 32 on the tracking light detection surface 30a. Further, the reflected light from the predetermined information recording surface of the optical disk 2 that has passed through the tracking region 31b of the hologram 31 forms a condensed spot 33 on the tracking light detection surface 30b. The tracking areas 31a and 31b of the hologram 31 correspond to the tracking areas 3d and 3e of the hologram 3 of the first embodiment, respectively. That is, the tracking area 31a is a first tracking area, and the tracking area 31b is a second tracking area. The tracking light detection surfaces 30a and 30b correspond to the tracking light detection surfaces 4a and 4b of the first embodiment, respectively. That is, the tracking light detection surface 4a is a first tracking light detection surface, and the tracking light detection surface 4b is a second tracking light detection surface.

  The positions of the condensing spot 32 and the condensing spot 33 on the light receiver 30 are different from each other in the direction corresponding to the radial direction and the direction corresponding to the tangential direction. The condensing spots 32 and 33 are condensing spots by one of the ± first-order lights of the diffracted light of the hologram 31. As described later in Embodiment 4, the condensing spots by the other ± first-order lights are used. This is for arranging a light detection surface for tracking control. The distance E in the direction corresponding to the tangential direction between the condensing spot 32 and the condensing spot 33 is such that the condensing spots 32 and 33 do not protrude from the tracking light detection surfaces 30a and 30b. , 30b is shorter than the width 2C in the direction corresponding to the tangential direction. If the distance E can be made equal to the width 2C, the arrangement of the light detection surfaces of the second embodiment can be obtained.

  The tracking light detection surface 30a with the condensing spot 32 has a width of 2C in the direction corresponding to the tangential direction in the G region around the condensing spot 32, and the condensing spot 32 is in the tangential direction of the tracking light detection surface 30a. It was made to be in the center of the direction corresponding to. Further, the width in the direction corresponding to the tangential direction in the F region closer to the focused spot 33 is narrowed to D, so that the focused spot 33 is next to the direction corresponding to the tangential direction of the light detection surface 2b. Arranged. On the other hand, the tracking light detection surface 30b with the condensing spot 33 has a width of 2C in the direction corresponding to the tangential direction in the F region around the condensing spot 33, and the condensing spot 33 is the center of the tracking light detection surface 30b. It was to be in. Further, the width in the direction corresponding to the tangential direction in the G region on the side close to the condensing spot 32 is narrowed to C, and adjacent to the direction corresponding to the tangential direction of the tracking light detection surface 30a where the condensing spot 32 is located. Arranged. A tracking light detection surface 30b whose width in the direction corresponding to the tangential direction is C is disposed on the opposite side of the tracking light detection surface 30b with the condensing spot 33 from the tracking light detection surface 30a with the condensing spot 32. . In addition, a tracking region 30a having a width C in a direction corresponding to the tangential direction is arranged on the opposite side of the tracking light detection surface 30b with the condensing spot 33 from the tracking light detection surface 30a with the condensing spot 32. The tracking region 30a whose width corresponding to the tangential direction is C is disposed because the width of the direction corresponding to the tangential direction in the region F of the tracking light detection surface 30b where the condensed spot 33 is located is 2C. Only. The tracking light detection surface 30a with the condensing spot 32 in the region G is the first light detection surface, and the tracking light detection surfaces 30b on both sides are the second light detection surfaces. In addition, the tracking light detection surface 30b with the condensing spot 33 in the region F is the first light detection surface, and the tracking light detection surfaces 30a on both sides are the second light detection surfaces.

  In addition, a set of tracking light detection surfaces 30a and 30b that receive light from the tracking areas of other divided areas adjacent to the direction corresponding to the radial direction of the set of tracking light detection faces 30a and 30b are arranged symmetrically. . Then, the tracking light detection surfaces 30a and 30b are interchanged in the set of the tracking light detection surfaces 30a and 30b that receive light from the tracking regions of the other divided regions. In accordance with this, the condensing spots 32 and 33 from the tracking areas of the other divided areas are received by the tracking light detection surfaces 30b and 30a.

  When information is recorded or reproduced by focusing on the information recording surface 2a on the front side, the stray light spot 34 due to the light reflected by the information recording surface 2b on the back side and passing through the tracking region 31a of the hologram 31 is detected by the tracking light. It does not cover the surfaces 30a, 30b. Further, the stray light spot 35 caused by the light that has passed through the tracking region 31b of the hologram 31 is hardly applied to the tracking light detection surfaces 30a and 30b. On the other hand, when information is recorded or reproduced by focusing on the information recording surface 2b on the back side, the stray light spot 36 caused by the light reflected by the information recording surface 2a on the near side and passing through the tracking region 31a of the hologram 31 is A substantially rectangular shape is applied to a pair of adjacent tracking light detection surfaces 30a and 30b. The width of the stray light spot 36 in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 30a is C, and the width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 30b is also C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 36 and the output from the tracking light detection surface 30b cancel each other. The stray light spot 37 caused by the light that has passed through the tracking region 31b of the hologram 31 has a substantially rectangular shape and is applied to the tracking light detection surfaces 30a and 30b. The width of the stray light spot 37 in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 30a is 2C, and the total width in the direction corresponding to the rectangular tangential direction on the tracking light detection surface 30b is 3C / 2. is there. In other words, it cannot be offset by C / 2. However, in the case where the tracking light detection surface 30b that is not covered by the condensing spots 32 and 33 is not disposed, the width in the direction corresponding to the tangential direction of the rectangle on the tracking light detection surface 30b is C / 2, which is 3C / 2. It cannot be offset by the minute. Accordingly, the tracking light detection surface 30b where the condensing spots 32 and 33 are not applied can be offset more greatly.

  In the third embodiment, the stray light spots 34 and 35 are hardly applied to the tracking light detection surfaces 30a and 30b, but the case where the stray light spots 34, 35, 36 and 37 are applied to the tracking light detection surfaces 30a and 30b is considered. When the stray light spot 34 is applied to the tracking light detection surfaces 30a and 30b, it is applied in a rectangular shape to the right side of the condensing spot 32 on the paper surface. When the rectangle is formed in the area F in FIG. 9A, the sum of the widths of the stray light spot 34 in the direction corresponding to the tangential direction on the tracking light detection surface 30a is (E−C) + C = E. The width in the direction corresponding to the tangential direction applied to the tracking light detection surface 30b is 2C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 34 and the output from the tracking light detection surface 30b cannot be offset by 2C-E. However, if there is no tracking light detection surface 30b to which the condensing spot 32 is not applied, the width in the direction corresponding to the tangential direction of the stray light spot 34 applied to the tracking light detection surface 30a is E-C. -E, greater than in some cases. When the rectangle is formed in the G region, the width of the stray light spot 34 in the direction corresponding to the tangential direction applied to the tracking light detection surface 30a is C, and the width in the direction corresponding to the tangential direction applied to the tracking light detection surface 30b. Is also C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 34 and the output from the tracking light detection surface 30b cancel each other.

  When the stray light spot 35 is applied to the tracking light detection surfaces 30a and 30b, it is applied in a rectangular shape to the right side of the condensing spot 33 on the paper surface. When the rectangle is formed by an area F, the width of the stray light spot 35 in the direction corresponding to the tangential direction applied to the tracking light detection surface 30a is C, and the direction corresponding to the tangential direction applied to the tracking light detection surface 30b. Is also C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 35 and the output from the tracking light detection surface 30b cancel each other. When the rectangle is formed in the G region, the width of the stray light spot 35 in the direction corresponding to the tangential direction applied to the tracking light detection surface 30b is C / 2 and does not cover the tracking light detection surface 30a. Therefore, the output from the tracking light detection surface 30a by the stray light spot 35 and the output from the tracking light detection surface 30b are not offset by C / 2.

  When the stray light spot 36 is applied to the tracking light detection surfaces 30 a and 30 b, the stray light spot 36 is applied to the left side of the light condensing spot 32 in a rectangular shape. Regardless of whether the rectangle is formed by the F region or the G region, the width of the stray light spot 36 in the direction corresponding to the tangential direction applied to the tracking light detection surface 30a is C, and the tracking light detection surface 30b. The width in the direction corresponding to the tangential direction is also C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 36 and the output from the tracking light detection surface 30b cancel each other. If there is no tracking light detection surface 30b on which the focused spot 33 is not applied, it is not possible to cancel by C.

  When the stray light spot 37 is applied to the tracking light detection surfaces 30a and 30b, it is applied in a rectangular shape to the left side of the condensing spot 33 on the paper surface. When the rectangle is formed in the area F, the width of the direction in which the stray light spot 37 corresponds to the tangential direction applied to the tracking light detection surface 30a is D (= E), and the tangential direction applied to the tracking light detection surface 30b. The total width in the direction corresponding to is 2C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 37 and the output from the tracking light detection surface 30b cannot be offset by 2C-E. In the case where there is no tracking light detection surface 30b to which the condensed spot 33 is not applied, the width of the direction in which the stray light spot 37 corresponds to the tangential direction applied to the tracking light detection surface 30b is C. Therefore, the output from the tracking light detection surface 30a by the stray light spot 37 and the output from the tracking light detection surface 30b cannot be offset by E−C. When E> 3C / 2, the former can be canceled more, and when E <3C / 2, the latter can be canceled more. When the rectangle is formed in the G region, the width of the direction in which the stray light spot 37 corresponds to the tangential direction applied to the tracking light detection surface 30a is 2C, and the direction corresponding to the tangential direction applied to the tracking light detection surface 30b. The total sum of the widths is 3C / 2. Therefore, the output from the tracking light detection surface 30a by the stray light spot 37 and the output from the tracking light detection surface 30b are not offset by C / 2. When the stray light spot 37 is applied to both the F region and the G region, the output from the tracking light detection surface 30a and the output from the tracking light detection surface 30b cancel each other for the F region and the G region. It is desirable to be done. Since the output from the tracking light detection surface 30a is large for the G region, it is better that the output from the tracking light detection surface 30b is large for the F region. For this purpose, it is more advantageous to dispose the tracking light detection surface 30b where the condensing spot 33 is not applied than to dispose it.

  As described above, the optical system of the optical pickup device according to the third embodiment makes the output from the tracking light detection surfaces 30a and 30b by the stray light spots 34, 35, 36, and 37 almost zero or cancels and almost zeros. Even if it cannot be completely canceled, the amount of offset can be increased.

  Therefore, in the optical pickup device of the third embodiment, the received light amount of the reflected light from the information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface enters. The amount of reflected light from the information recording surface other than the predetermined information recording surface received by the adjacent second light detection surfaces can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

(Embodiment 4)
The fourth embodiment will be described with reference to the drawings. FIG. 10 is a configuration diagram of an optical system of the optical pickup device according to the fourth embodiment, and FIG. 11 is a configuration diagram of the optical pickup device according to the fourth embodiment. The optical pickup device of the fourth embodiment includes a light receiver having the tracking light detection surface arranged as in the third embodiment.

  In the optical pickup device 57 of the fourth embodiment, the laser module 42 provided with the diffraction element 43, the reflection mirror 44, the collimating lens 45, the rising mirror 46, and the front light monitor 52 are arranged at predetermined positions on the base 55. Configured. Further, the optical pickup device 57 arranges an objective lens driving device 56 including a lens holder 56 a for arranging the objective lens 51 and the hologram element 50 at a predetermined position of the base 55. The laser module 42 includes a laser light source 40 for emitting DVD laser light, a second laser light source 40a for emitting CD laser light, a laser light emitted from the laser light source 40 and reflected by the DVD 53, and a second laser light source 40a. This is a single package including a light receiver 41 and a second light receiver 41m that receive the laser light emitted from the laser beam and reflected by the CD 54. The hologram element 50 is an element in which a DVD hologram 47, a CD hologram 48, and a quarter-wave plate 49 are integrated.

  In the fourth embodiment, the laser light source 40 and the second laser light source 40a are integrated, and laser light is emitted from the laser element. The laser element emits a laser beam having a wavelength of about 650 nm for DVD and a laser beam having a wavelength of about 780 nm for CD, a laser element that emits a laser beam for DVD, and a laser element that emits a laser beam for CD There are some that combine. The laser element is disposed on a semiconductor substrate on which the light detection surface of the light receiver 41 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 DVD 53 or CD 54. The laser beam for DVD and the laser beam for CD emitted from the laser module 42 are substantially parallel and close to each other, and are P-polarized light.

  The diffraction element 43 has a diffraction grating that does not act on the DVD laser light and diffracts only the CD laser light. 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 44 is for bending the laser light emitted from the laser light source 40, and for reducing the size of the optical pickup device 57. A polarization separation film is formed on the surface of the reflection mirror 44, and the polarization separation film reflects most of the P-polarized laser light emitted from the laser light source 40 and transmits a part thereof. The polarization separation film substantially totally reflects the laser beam reflected by the DVD 53 and CD 54 and converted to S-polarized light.

  The collimating lens 45 converts the laser light emitted from the laser light source 40, which is divergent light, into substantially parallel light. On the contrary, the laser beam reflected by the DVD 53 and the CD 54, which is parallel light, is converted into focused light. The collimating lens 45 is made of optical glass or optical plastic.

  The rising mirror 46 is a reflecting mirror that converts the laser beam, which has been in a direction substantially parallel to the DVD 53 or the CD 54 until then, into a direction at a substantially right angle.

  FIG. 12 is a configuration diagram of a DVD hologram according to the fourth embodiment. In the fourth embodiment, the DVD hologram 47 is a hologram. The DVD hologram 47 is configured to work only on an S-polarized laser beam having a wavelength of 650 nm for DVD. The DVD hologram 47 is divided by a dividing line 47a parallel to the direction corresponding to the tangential direction and a dividing line 47b parallel to the direction corresponding to the radial direction. The dividing line 47 a and the dividing line 47 b pass through almost the center of the hologram 47. The divided areas 47c, 47d, 47e, and 47f obtained by dividing the hologram 47 into four equal parts include tracking areas 47g and 47h and a focus area 47i, respectively. The laser light that has passed through the tracking regions 47g and 47h is used for tracking control. The laser beam that has passed through the focus area 47i is used for focus control. The tracking areas 47g and 47h and the focus area 47i are separated by a dividing line parallel to the direction corresponding to the tangential direction. The tracking area 47g and the tracking area 47h are separated by a dividing line parallel to the direction corresponding to the tangential direction, but the present invention is not limited to this.

  The tracking areas 47g and 47h of the divided area 47c and the tracking areas 47g and 47h of the divided area 47e are in a line-symmetric relationship with the dividing line 47b as the axis of symmetry. The tracking areas 47g and 47h of the divided area 47d and the tracking areas 47g and 47h of the divided area 47f are in a line-symmetric relationship with the dividing line 47b as the axis of symmetry. On the other hand, the tracking regions 47g and 47h of the divided region 47c and the tracking regions 47g and 47h of the divided region 47d are in a line-symmetric relationship with the dividing line 47a as the axis of symmetry, but the tracking region 47g and the tracking region 47h are interchanged. Similarly, the tracking areas 47g and 47h of the divided area 47e and the tracking areas 47g and 47h of the divided area 47f are in a line-symmetric relationship with respect to the dividing line 47a, but the tracking area 47g and the tracking area 47h are interchanged. In the divided areas 47 c and 47 e, the tracking area 47 g is arranged in the peripheral part in the direction corresponding to the radial direction of the hologram 47, and the tracking area 47 h is arranged in the central part in the direction corresponding to the radial direction of the hologram 47. In the divided regions 47 d and 47 f, the tracking region 47 g is disposed at the center portion in the direction corresponding to the radial direction of the hologram 47, and the tracking region 47 h is disposed at the peripheral portion in the direction corresponding to the radial direction of the hologram 47. The tracking area 47g is a first tracking area, and the tracking area 47h is a second tracking area.

  The focus area 47i is divided into two areas by a dividing line in a direction corresponding to the tangential direction, and the light that has passed through one enters the light receiver 41 and the second light receiver 41m after being focused, and the other is The light passing therethrough is diffracted so as to enter the light receiver 41 and the second light receiver 41m before being brought into focus.

  FIG. 13 is a configuration diagram of a CD hologram according to the fourth embodiment. In the fourth embodiment, the CD hologram 48 is the second hologram. The CD hologram 48 is configured to work only on an S-polarized laser beam having a wavelength of 780 nm for CD. The CD hologram 48 is divided by a dividing line 48 a parallel to the direction corresponding to the tangential direction of the CD 54 and a dividing line 48 b parallel to the direction corresponding to the radial direction of the CD 54. The dividing line 48a and the dividing line 48b pass through almost the center of the hologram 48 for CD. The tracking region 48c and the tracking region 48d occupy one side divided by the dividing line 48b, and the focus regions 48e, 48f, 48g, and 48h occupy the other. The tracking area 48c and the tracking area 48d are separated by a dividing line 48a. The focus area 48e and the focus area 48f are separated by a dividing line parallel to the direction corresponding to the tangential direction. The focus area 48g and the focus area 48h are separated by a dividing line parallel to the direction corresponding to the tangential direction. The focus area 48f and the focus area 48h are separated by a dividing line 48a. The light that has passed through one of the focus area 48e and the focus area 48f enters the light receiver 41 after being in focus, and the light that has passed through the other enters the light receiver 41 before being in focus. Further, the light that has passed through one of the focus region 48g and the focus region 48h is in a focused state and then enters the light receiver 41 and the second light receiver 40m, and the light that has passed through the other is received before being in a focused state. Incident on the light receiving device 41 and the second light receiving device 40m.

  In the fourth embodiment, the tracking area 48c and the tracking area 48d occupy one side divided by the dividing line 48b, and the focus areas 48e, 48f, 48g, and 48h occupy the other. However, the tracking region 48c and the focus regions 48e and 48f may be interchanged, or the tracking region 48d and the focus regions 48g and 48h may be interchanged. Thereby, the amount of stray light to the focus signal can be reduced.

  The quarter-wave plate 49 converts the P-polarized laser light emitted from the laser light source 40 into circularly polarized light and directs it to the DVD 53, and converts the P-polarized laser light emitted from the second laser light source 40a into circularly polarized light. Then turn to CD54. The circularly polarized laser beam reflected by the DVD 53 or the CD 54 is converted into S-polarized light and directed to the light receiver 41 and the second light receiver 41m. Therefore, the DVD hologram 47 does not act as a hologram because it is P-polarized light with respect to the laser light emitted from the laser light source 40. However, since the light reflected by the DVD 53 is converted to S-polarized light by the quarter-wave plate 49, it can act as a hologram. Further, the CD hologram 48 does not act as a hologram because it is P-polarized light with respect to the laser light emitted from the second laser light source 40a. However, since the light reflected by the CD 54 is converted to S-polarized light by the quarter-wave plate 49, it can act as a hologram.

  The objective lens 51 is made of optical glass, optical plastic, or the like, and can focus on both the DVD 53 and the CD 54. As the objective lens 51 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 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 52 receives a part of the laser light emitted from the light source 40 and the second light source 40a, converts the light amount into an electrical 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 DVD 53 or CD 54 to be constant.

  The DVD 53 is a DVD-ROM, DVD ± R / RW, DVD-RAM, or the like. The CD 54 is a CD, a CD-ROM, or a CD-R / RW. Both the DVD 53 and the CD 54 can be recorded and reproduced except for a reproduction-only medium. Moreover, although the information recording surface of the CD is a single layer, the DVD 53 includes an optical disc having a plurality of information recording surfaces including an optical disc having two information recording surfaces. Further, not only the combination of the DVD 53 and the CD 54 but also the combination with the next-generation DVD such as Blu-ray Disc and HD-DVD does not lose generality. In the fourth embodiment, the DVD 53 is an optical disc and the CD 54 is a second optical disc.

  The light receiver 41 and the second light receiver 41m have a configuration in which a light detection surface that is a photodiode is disposed on a semiconductor substrate. Further, a laser element constituting the laser light source 40 and the second laser light source 40a and a reflection mirror for directing the laser light emitted from the laser element to the DVD 53 or the CD 54 are arranged on the semiconductor substrate. The light incident on the light detection surface is converted into an electrical signal corresponding to the light amount and output from the light receiver 41 and the second light receiver 40a.

  FIG. 14 is a layout diagram of the light detection surfaces of the light receiver and the second light receiver according to the fourth embodiment. The provisional emission point 41k is the point where the direction of the laser beam for DVD emitted from the laser element of the laser light source 40 can be changed by the reflection mirror, and the laser beam for CD emitted from the laser element of the second laser light source 40a is the reflection mirror. The point where the direction can be changed with is designated as a temporary light emitting point 41l. Also, the focused spot by the DVD laser light reflected by the DVD 53 and passing through the tracking areas 47g and 47h of the hologram 47 is a small black circle, and the focused spot by the DVD laser light passing through the focus area 47i is a large black circle. expressed. The focused spot by the CD laser beam reflected by the CD 54 and passing through the tracking areas 48c and 48d of the hologram 48 is the focused spot by the CD laser beam passing through the small white circles and the focus areas 48e, 48f, 48g and 48h. Is represented by a large white circle. The sizes of black circles and white circles in FIG. 14 do not reflect the actual size of the focused spot.

  The same set of tracking light detection surfaces 41a and 41b as the tracking light detection surfaces 30a and 30b described in the third embodiment are arranged. Those having the same shape are arranged symmetrically adjacent to each other in the direction corresponding to the radial direction. However, the tracking light detection surface 41a and the tracking light detection surface 41b are interchanged. A pair of the two tracking light detection surfaces 41a and 41b and a pair of the tracking light detection surfaces 41a and 41b are arranged symmetrically with the axis in the direction corresponding to the radial direction passing through the provisional light emission point 41k as the axis of symmetry. All the tracking light detection surfaces 41a are electrically connected to each other. All the tracking light detection surfaces 41b are also electrically connected to each other. Focus light detection surfaces 41c and 41d are arranged inside the group of four tracking light detection surfaces 41a and 41b. The focus light detection surface 41c and the focus light detection surface 41d are each a rectangle that is long in a direction corresponding to the radial direction. The focus light detection surface 41c is a first focus light detection surface, and the focus light detection surface 41d is a second focus light detection surface. A set of focus light detection surfaces 41c and 41d arranged alternately adjacent to each other in a direction corresponding to two sets of tangential directions is arranged side by side in a direction corresponding to the tangential direction with a space therebetween. The length in the direction corresponding to the radial direction of the focus light detection surfaces 41c and 41d is equal to or greater than the distance between the centers of the two sets of focus light detection surfaces 41c and 41d. All the focus light detection surfaces 41c are electrically connected to each other, and all the focus light detection surfaces 41d are also electrically connected to each other. Two tracking light detection surfaces 41e and two tracking light detection surfaces 41f arranged in a direction corresponding to the tangential direction are arranged on the opposite side to the side where the temporary light emission point 41l is located. The tracking light detection surface 41e is electrically connected to the tracking light detection surface 41a, and the tracking light detection surface 41f is electrically connected to the tracking light detection surface 41b. The tracking light detection surface 41e and the tracking light detection surface 41f are fourth light detection surfaces.

  The arrangement of the light detection surface is for receiving one of ± first-order light diffracted by the hologram 47 for DVD and the hologram 48 for CD. A detector that receives one of the ± primary lights is referred to as a light receiver 41. The arrangement of the light detection surface that receives the other of the ± primary lights will be described below. A detector that receives the other of the ± primary lights is a second light receiver 41m. The + 1st order light and the −1st order light of the laser beam for DVD are incident on point-symmetrical positions around the temporary light emitting point 41k. Similarly, the + 1st order light and the −1st order light of the laser beam for CD are incident on point-symmetrical positions around the temporary light emitting point 41l. Therefore, the light detection surface that receives the other of the ± primary lights is disposed on the opposite side across the temporary light emitting points 41k and 41l. The tracking light detection surfaces 41g, 41h, 41i, and 41j are each composed of two light detection surfaces arranged in a direction corresponding to the tangential direction. The tracking light detection surface 41g, the tracking light detection surface 41h, the tracking light detection surface 41i, and the tracking light detection surface 41j are third light detection surfaces. The tracking light detection surface 41g and the tracking light detection surface 41h, and the tracking light detection surface 41i and the tracking light detection surface 41j are arranged in a direction corresponding to the tangential direction. The tracking light detection surface 41g and the tracking light detection surface 41i, and the tracking light detection surface 41h and the tracking light detection surface 41j are arranged in a direction corresponding to the radial direction.

  If only one of the ± primary lights is used, the area of the light receiver 41 can be reduced. If both ± first-order lights are transferred, the light use efficiency is high and optimum tracking control can be easily obtained.

  FIG. 15 is a diagram illustrating a state in which light that has passed through the hologram for DVD enters the light receiver and the second light receiver. In FIG. 15, the light that has passed through the tracking areas 47g and 47h of the divided area 47e of the DVD hologram 47 and the focus area 47i is shown. The DVD laser light that has passed through the tracking region 47g of the divided region 47e at the lower right of the paper surface enters the tracking light detection surface 41a at the upper left of the paper surface. The DVD laser light that has passed through the tracking region 47h of the divided region 47e is incident on the tracking light detection surface 41b at the upper left of the drawing. Further, the DVD laser light that has passed through the focus area 47i of the divided area 47e is incident on the upper side of the paper across the focus light detection surfaces 41c and 41d on the left side of the paper. On the other hand, the DVD laser light that has passed through the tracking areas 47g and 47h of the divided area 47e on the lower right side of the page is the tracking light detection surface 41j on the lower right side of the page among the tracking light detection surfaces 41g, 41h, 41i, and 41j. Both are incident on the right light detection surface. Further, the DVD laser light that has passed through the focus area 47i of the divided area 47e is incident on the light detection surface on the left side of the tracking light detection surface 41j on the lower right side of the drawing.

  Similarly, the laser light that has passed through the tracking regions 47g and 47h of the divided region 47c at the lower left side of the paper surface is incident on the left light detection surface of the tracking light detection surfaces 41a and 41b at the upper right side of the paper surface and the tracking light detection surface 41i at the lower left surface of the paper surface. . The laser light that has passed through the focus region 47i of the divided region 47c is incident on the right light detection surface of the tracking light detection surface 41i on the upper right side of the focus light detection surface 41c and 41d on the right side of the paper surface and the lower left side of the paper surface. Further, the laser light that has passed through the tracking regions 47g and 47h of the divided region 47d at the upper left of the paper surface is incident on the left light detection surface of the tracking light detection surfaces 41a and 41b at the lower right surface of the paper and the tracking light detection surface 41g at the upper left surface of the paper. . The laser light that has passed through the focus area 47i of the divided area 47d is incident on the right light detection surface of the focus light detection surfaces 41c and 41d on the right side of the paper and the tracking light detection surface 41g on the upper left side of the paper. The laser beams that have passed through the tracking regions 47g and 47h of the divided region 47f on the upper right side of the paper are incident on the right light detection surface of the tracking light detection surfaces 41a and 41b on the lower left side of the paper and the tracking light detection surface 41h on the upper right side of the paper. The laser light that has passed through the focus area 47i of the divided area 47f is incident on the light detection surface on the left side of the focus light detection surfaces 41c and 41d on the left side of the paper and on the left side of the tracking light detection surface 41h on the upper right side of the paper. The tracking light detection surfaces 41g, 41h, 41i, and 41j are incident on almost all of the laser beams that have passed through the divided regions 47d, 47f, 47c, and 47e, respectively. Since the size of the focused spot of the light that has passed through the focus area 47i varies depending on the focused state on the predetermined information recording surface of the DVD 53, the intervals incident on the tracking light detection surfaces 41g, 41h, 41i, and 41j are widened. Therefore, it is necessary not to enter the adjacent light detection surface. Therefore, as described above, the arrangement of the focus light detection surfaces 41c and 41d is also set so that the pair of the focus light detection surfaces 41c and 41d that are long in the direction corresponding to the radial direction is spaced apart, and the laser light used for focus control is arranged. I tried to capture everything. In particular, the length of the focus light detection surfaces 41c and 41d in the direction corresponding to the radial direction is set to be equal to or greater than the distance between the centers of the two sets of focus light detection surfaces 41c and 41d. Even if the condensing spot becomes large on the surfaces 41c and 41d, it can be prevented from protruding from the light detection surface.

  The outputs from the tracking light detection surfaces 41g, 41h, 41i, 41j, 41a and 41b are IA, IB, IC, ID, IE and IF, respectively, and the outputs from the focus light detection surfaces 41c and 41d are IG and IH. In the case of DVD-RAM, the tracking error signal TES, which is a tracking control signal, is calculated as TES = (IA + IB) − (IC + ID). Further, the tracking error signal TES in the reproduction of the DVD 53 other than the DVD-RAM is calculated as TES = ∠ (IC−ID) + ∠ (IB−IA) or TES = ∠ {(IC + IB) − (ID + IA)}. The 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 on the DVD 53 other than the DVD-RAM is calculated as TES = IE-IF. A focus error signal FES, which is a signal for focus control, is calculated as FES = IG−IH. Further, the reproduction signal RF is calculated as RF = IA + IB + IC + ID.

  Since the reproduction signal RF is reflected by the DVD 53 and captures the laser light in almost the entire region that has passed through the hologram 47 for DVD, jitter is excellent.

  FIG. 16 is a diagram illustrating a state in which light that has passed through the CD hologram enters the light receiver and the second light receiver. The CD laser beam passing through the CD hologram 48 is diffracted into a central 0th-order light called a main beam by the diffraction grating of the diffraction element 43 and ± 1st-order lights on both sides called side beams. It is. Therefore, the main beam and the side beam are incident on the light receiver 41 and the second light receiver 41m as one set. The side beam of the CD laser light that has passed through the tracking region 48c is incident on the tracking light detection surface 41f, and the main beam is incident on the tracking light detection surface 41i. Further, the side beam of the CD laser light that has passed through the tracking region 48d is incident on the tracking light detection surface 41e, and the main beam is incident on the tracking light detection surface 41j. The tracking light detection surfaces 41e and 41f are arranged so that only the side beam is incident and the main beam is not incident. Conversely, the tracking light detection surfaces 41i and 41j are arranged so that only the main beam is incident and the side beams are not incident.

  Only the main beam is incident on the focus light detection surfaces 41c and 41d on the right side of the paper and only the main beam is incident on the right light detection surface of the tracking light detection surface 41g. . It is preferable to perform the focus control of the CD 54 only with the main beam. The focus light detection surfaces 41c and 41d are incident on the adjacent light detection surface on which the DVD laser light is incident, straddling the two light detection surfaces. Further, the CD laser light that has passed through the focus regions 48g and 48h is incident only on the focus light detection surfaces 41c and 41d on the left side of the paper, and only on the light detection surface on the left side of the tracking light detection surface 41h. Incident. The CD laser light that has passed through the focus regions 48e and 48f enters the focus light detection surfaces 41c and 41d on the adjacent light detection surface on which the DVD laser light is incident. The detection surface can be shared. The hologram is configured such that one of the side beams that have passed through the focus regions 48e and 48f and one of the side beams that have passed through the focus regions 48g and 48h overlap. The shape and arrangement of the light detection surface are set so that the side beams that have passed through the focus regions 48e, 48f, 48g, and 48h do not enter the light detection surface. However, even if a side beam is incident on the focus light detection surface 41c, the influence on the focus control signal is small.

  In the fourth embodiment, the positions of the focused spots on the tracking light detection surface 41a and the tracking light detection surface 41b are shifted in the direction corresponding to the tangential direction. This is because only the main beam is incident on the third light detection surface. As a result, a plurality of sets of the first light detection surface and the second light detection surface were arranged in the direction corresponding to the radial direction, and the set was also shifted in the direction corresponding to the tangential direction.

  Since the tracking light detection surfaces 41e and 41f are electrically connected to the tracking light detection surfaces 41a and 41b, the outputs from the tracking light detection surfaces 41e and 41f are IE and IF, respectively. A tracking error signal TES that is a signal for tracking control of the CD 54 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. Alternatively, TES = ∠ {(IA + ID) − (IC + IB)} may be calculated. 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. Thus, since it is possible to perform tracking control even when reproducing a poor CD 54 that is out of the standard that cannot be tracked, it is possible to deal with a wider range of CDs 54 as an optical disk apparatus. On the other hand, a focus error signal FES, which is a signal for focus control, is calculated as FES = IG−IH. 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. Further, since the tracking light detection surfaces 41e and 41f are electrically connected to the tracking light detection surfaces 41a and 41b, respectively, it is not necessary to provide a new output terminal for CD tracking control, and electrical wiring is easy. It is.

  The base 55 forms a skeleton of the optical pickup device 57, and the components constituting the optical pickup device 57 including various optical components are attached to the base 55 directly or via other components as described above. The base 55 is made of an alloy material such as Zn alloy or Mg alloy or a hard resin material.

  In the objective lens driving device 56, a lens holder 56a to which the hologram element 50 and the objective lens 51 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 56a. A magnet is fixed to the apparatus main body. The objective lens driving device 56 generates an electromagnetic force with the magnet by passing a predetermined current through the tracking coil or the focus coil, and moves the objective lens 51 mounted on the lens holder 56a 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 electrical signal that is converted from the light amount of the laser light incident on the light receiver 41 and output.

  The optical path of the optical pickup device 57 having the above configuration will be described. In FIG. 10, the DVD laser light emitted from the laser light source 40 passes through the diffraction grating of the diffraction element 43 as it is and enters the reflection mirror 44. Most of the laser light is reflected by the polarization separation film of the reflection mirror 44 and travels to the DVD 53, but part of the laser light is transmitted and enters the front light monitor 52. The light incident on the front light monitor 52 is converted into an electrical signal and used for controlling the amount of laser light emitted from the laser light source 40. The laser light reflected by the reflection mirror 44 enters the collimator lens 45, is converted from divergent light into parallel light, and enters the rising mirror 46. The laser beam is incident on the hologram element 50 by being bent in a direction perpendicular to the DVD 53 by the rising mirror. The laser light emitted from the hologram element 50 after passing through the DVD hologram 47 and the CD hologram 48 of the hologram element 50 as it is and converted from P-polarized light to circularly-polarized light by the quarter wavelength plate 49 enters the objective lens 51. . The laser beam converted so as to be focused on the information recording surface of the DVD 53 by the objective lens 51 enters the information recording surface of the DVD 53.

  The laser light reflected by the information recording surface of the DVD 53 is converted into parallel light by the objective lens 51 and enters the hologram element 50. The laser light is converted from circularly polarized light to S polarized light by the ¼ wavelength plate 49, passes through the CD hologram 48 as it is, and passes through the DVD hologram 47. In the tracking regions 47 g and 47 h and the focus region 47 i, the laser light is transmitted. The light is diffracted and emitted from the hologram element 50. The light is converted into focused light by the collimator lens 45, reflected by the reflection mirror 44, and the laser light is incident on predetermined light detection surfaces of the light receiver 41 and the second light receiver 41m. The laser light incident on the predetermined light detection surface is converted into an electrical signal, output from the light receiver 41 and the second light receiver 41m, and sent to the optical disc apparatus main body, where a tracking control signal, a focus control signal, A reproduction signal is generated.

  The CD laser light emitted from the second laser light source 40 a is diffracted by the diffraction grating of the diffraction element 43 into a main beam that is zero-order light and a side beam that is ± first-order light and enters the reflection mirror 44. Although most of the laser light is reflected by the polarization separation film of the reflection mirror 44 and travels toward the CD 54, a part of the laser light is transmitted and enters the front light monitor 52. The light incident on the front light monitor 52 is converted into an electric signal and used for controlling the amount of laser light emitted from the second laser light source 40a. The laser light reflected by the reflection mirror 44 enters the collimator lens 45, is converted from divergent light into parallel light, and enters the rising mirror 46. The laser beam is incident on the hologram element 50 by being bent in a direction perpendicular to the CD 54 by the rising mirror. The laser light emitted from the hologram element 50 after passing through the DVD hologram 47 and the CD hologram 48 of the hologram element 50 as it is and converted from P-polarized light to circularly-polarized light by the quarter wavelength plate 49 enters the objective lens 51. . The laser beam converted so as to be focused on the information recording surface of the CD 54 by the objective lens 51 is incident on the information recording surface of the CD 54.

  The laser light reflected by the information recording surface of the CD 54 is converted into parallel light by the objective lens 51 and enters the hologram element 50. The laser light is converted from circularly polarized light to S polarized light by the quarter wavelength plate 49, and when passing through the hologram 44 for CD, it is diffracted by the tracking regions 48c and 48d, the focus regions 48e, 48f, 48g and 48h. Is transmitted through the hologram 47 as it is and emitted from the hologram element 50. The light is converted into focused light by the collimator lens 45, reflected by the reflection mirror 44, and the laser light is incident on predetermined light detection surfaces of the light receiver 41 and the second light receiver 41m. The laser light incident on the predetermined light detection surface is converted into an electrical signal, output from the light receiver 41 and the second light receiver 41m, and sent to the optical disc apparatus main body, where a tracking control signal, a focus control signal, A reproduction signal is generated.

  Some DVDs 53 have a plurality of information recording surfaces. When information is recorded or reproduced by condensing the laser light emitted from the laser light source on a predetermined information recording surface, the reflected light from the information recording surface other than the predetermined information recording surface is reflected by the light receiver 41 and the second light receiving light. It enters the container 41m. However, the light receiver 41 of the optical pickup device 57 of the fourth embodiment has the same tracking light detection surfaces 41a and 41b as the tracking light detection surfaces 30a and 30b of the light receiver 30 of the third embodiment. Therefore, the output from the tracking light detection surfaces 41a and 41b due to the reflected light from the information recording surface other than the predetermined information recording surface can be canceled efficiently, and the offset of the tracking control signal can be minimized. .

  As described above, in the optical pickup device according to the fourth embodiment, the reflected light from the information recording surface other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface is incident. The amount of received light and the amount of received light reflected from information recording surfaces other than the predetermined information recording surface received by the adjacent second light detection surface can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface.

(Embodiment 5)
The fifth embodiment will be described with reference to the drawings. FIG. 17 is a configuration diagram of the optical pickup module according to the fifth embodiment, and FIG. 18 is a configuration diagram of the optical disk device according to the fifth embodiment. The fifth embodiment is an optical disk device on which the optical pickup device described in the first to fourth embodiments is mounted.

  A drive mechanism that drives the DVD 53, the CD 54, and the optical pickup device 67 of the optical disk device 70 is referred to as an optical pickup module 60. The base 61 forms a framework of the optical pickup module 60, and each component is fixed directly or indirectly to the base 61.

  A spindle motor 62 having a turntable on which the DVD 53 and the CD 54 are placed is fixed to the base 61. The spindle motor 62 generates a rotational driving force that rotates the DVD 53 and the CD 54.

  The feed motor 63 is fixed to the base 61. The feed motor 63 generates a rotational driving force necessary for the optical pickup device 67 to move between the inner periphery and the outer periphery of the DVD 53 or CD 54. As the feed motor 63, a stepping motor, a DC motor, or the like is used. The screw shaft 64 is spirally grooved and is connected to the feed motor 63 directly or via several stages of gears. In the fifth embodiment, it is directly connected to the feed motor 63. The guide shafts 65 and 66 are fixed to the base 61 via support members at both ends. The guide shafts 65 and 66 support the optical pickup device 67 so as to be movable. The optical pickup device 67 includes a rack 68 having guide teeth that mesh with the grooves of the screw shaft 64. Since the rack 68 converts the rotational driving force of the feed motor 63 transmitted to the screw shaft 64 into a linear driving force, the optical pickup device 67 can move between the inner periphery and the outer periphery of the DVD 53 or the CD 54.

  The optical pickup device 67 is the same as that described in the first to fourth embodiments, and further includes covers 58 and 59. The optical pickup device 67 performs at least one of recording and reproduction of information with respect to the DVD 53 and the CD 54, and emits laser light toward the DVD 53 and the CD 54 for that purpose. That is, the optical pickup device 67 includes laser light sources 1 and 40, holograms 3, 21, 31, 47 and light receivers 4, 20, 30, 41. The laser light sources 1 and 40 emit laser light to a predetermined information recording surface of the optical disk 2 and DVD 53 having a plurality of information recording surfaces. Further, the holograms 3, 21, 31, and 47 make the reflected light from the information recording surface other than the predetermined information recording surface of the optical disk 2 and the DVD 53 that has passed into a predetermined projection shape. The light receivers 4, 20, 30 and 41 receive the reflected light from the predetermined information recording surface of the optical disk 2 and the DVD 53 and the first light that receives a part of the reflected light in a predetermined projection shape. The detection surface and the reflected light of the partial region include a second light detection surface that receives the other partial region that is included in the same reflected light and is adjacent to the reflected light of the partial region. The first light detection surfaces are respectively arranged on both sides with the second light detection surfaces. The inclination of the guide shafts 65 and 66 is adjusted by an adjustment mechanism that constitutes a support member so that the laser light emitted from the optical pickup device 67 is incident on the DVD 53 or CD 54 at a right angle.

  The upper casing 71a and the lower casing 71b are combined and fixed to each other using screws or the like to form the casing 71. The tray 72 is provided in the casing 71 so as to freely appear and disappear. In the tray 72, the optical pickup module 60 to which the cover 69 is attached is arranged from the lower surface side. The cover 69 has an opening to expose a part including the objective lens of the optical pickup device 67 and the turntable of the spindle motor 62. In the case of the fifth embodiment, the feed motor 63 is also exposed. A bezel 73 is provided on the front end surface of the tray 72 so that when the tray 72 is stored in the casing 71, the entrance and exit of the tray 72 is closed.

  The bezel 73 is provided with an eject switch 74, and when the eject switch 74 is pressed, the engagement between the casing 71 and the tray 72 is released, and the tray 72 can be brought into and out of the casing 71. The rails 75 are slidably attached to both sides of the tray 72 and the casing 71, respectively.

  There is a circuit board (not shown) inside the casing 71 and inside the tray 72, and a signal processing system IC, a power supply circuit, and the like are mounted. The external connector 76 is connected to a power / signal line provided in an electronic device such as a computer. Then, power is supplied into the optical disc device 70 via the external connector 76, an electric signal from the outside is guided into the optical disc device 70, or an electric signal generated by the optical disc device 70 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 67 will be described. FIG. 19 is a diagram illustrating a control flow of the optical pickup device according to the fifth embodiment. The light incident on the light receiver 67b 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 70b of the optical disc apparatus main body 70a. . The analog signal processing unit 70b performs arithmetic / band processing on the input signal and outputs the result to the servo processing unit 70c. The servo processing unit 70c generates a focus error signal and a tracking error signal based on the signal from the analog signal processing unit 70b and outputs the focus error signal and the tracking error signal to the motor driving unit 70d. The focus error signal is a defocus of the light beam condensed on the information recording surface of the DVD 53 or CD 54. The tracking error signal is a deviation in the radial direction of the DVD 53 and the CD 54 with respect to the information track of the light beam condensed on the information recording surface of the DVD 53 and the CD 54. The motor driving unit 70d generates a current for driving the objective lens driving device 67e on which the objective lens 67c is mounted based on the input focus error signal and tracking error signal. As a result, the focal point deviation of the light beam condensed on the information recording surface of the DVD 53 and the CD 54 and the deviation relative to the information track are controlled to be minimal.

  The controller 70e receives signals sent from the analog signal processing unit 70b, servo processing unit 70c, motor driving unit 70d, digital signal processing unit 70f, and laser driving unit 70g. The controller 70e performs arithmetic processing on 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 67d receives part of the laser light emitted from the laser light source 67a, converts the amount of light into an electrical signal, and outputs it. As shown in FIG. 19, this electric signal enters the analog signal processing unit 70b of the optical disc apparatus main body 70a. The analog signal processing unit 70b performs arithmetic / band processing on the input signal and outputs the result to the digital signal processing unit 70f. The digital signal processing unit 70f generates a laser modulation signal based on the signal from the analog signal processing unit 70b and the data sent from the host 80, and sends it to the laser driving unit 70g. A laser light source driving power source 67f disposed in the vicinity of the laser light source 67a of the optical pickup device 67 receives a signal from the laser driving unit 70g and supplies a driving current to the laser light source 67a. As a result, the amount of the light beam condensed on the information recording surface of the DVD 53 or CD 54 is controlled to be constant.

  As described above, the optical disk device according to the fifth embodiment is equipped with the optical pickup device according to the first to fourth embodiments. The optical pickup devices according to the first to fourth embodiments receive reflected light from information recording surfaces other than the predetermined information recording surface received by the first light detection surface on which the reflected light from the predetermined information recording surface is incident. The amount of light reflected from the information recording surface other than the predetermined information recording surface received by the adjacent second light detection surface can be set to a stable ratio. Therefore, the output from the first light detection surface and the output from the second light detection surface due to the reflected light from the information recording surface other than the predetermined information recording surface are stably offset. Therefore, stable tracking control can be performed by minimizing the influence of reflected light from information recording surfaces other than the predetermined information recording surface. Therefore, the optical disk apparatus according to the fifth embodiment can perform stable tracking control even when information is recorded or reproduced on an optical disk having a plurality of information recording surfaces.

  As described above, the optical pickup device of the present invention can record and reproduce information stably with respect to an optical disc having a plurality of information recording surfaces, and is useful as an optical pickup device used in an optical disc device. The optical disc apparatus of the present invention can stably record and reproduce with respect to an optical disc having a plurality of layers of information recording surfaces, and is useful as an optical disc device used in electronic devices such as computers and DVD recorders.

The block diagram which shows the principal part of the optical system of the optical pick-up apparatus of this Embodiment 1. Enlarged view of the tracking light detection surface of the first embodiment The figure which shows the mode of the reflected light from the information recording surface of the back side in the case of condensing on the information recording surface of the near side of the optical disk of this Embodiment 1. The figure which shows the mode of the reflected light from the information recording surface of the near side at the time of condensing on the information recording surface of the back side of the optical disk of this Embodiment 1. (A) The figure which shows the condition of the optical disk at the time of recording on the information recording surface of the near side of this Embodiment 1, (b) The back side after recording on the information recording surface of the near side of this Embodiment 1 The figure which shows the situation of the optical disk when recording is started on the information recording surface (A) The figure which showed the condition of the reflected light of the laser beam from the information recording surface of the near side immediately after recording on the information recording surface of the back side after recording on the information recording surface of the near side of this Embodiment 1 (B) The figure at the time of irradiating the information recording surface on the back side from the area slightly entering the recording area on the information recording surface on the near side, (c) Completely in the recording area on the information recording surface on the near side The figure at the time of irradiating the laser beam to the information recording surface on the back side from the entered area, (d) The figure showing the situation of the hologram at the time of FIG. 6 (b) The figure which shows the mode of the reflected light on the light receiver of this Embodiment 1 in the case of FIG.6 (d). (A) Enlarged view of the tracking light detection surface of the second embodiment, (b) Diagram showing the state of light passing through the hologram (A) An enlarged view of the tracking light detection surface of the third embodiment, (b) A view showing a state of light passing through the hologram Configuration diagram of optical system of optical pickup device according to Embodiment 4 Configuration diagram of optical pickup device according to Embodiment 4 Configuration diagram of DVD hologram of the fourth embodiment Configuration diagram of hologram for CD of Embodiment 4 Arrangement of the light detection surfaces of the light receiver and the second light receiver according to the fourth embodiment The figure which shows a mode that the light which passed the hologram for DVDs injects into a light receiver and a 2nd light receiver. The figure which shows a mode that the light which passed the hologram for CDs injects into a light receiver and a 2nd light receiver. Configuration diagram of optical pickup module according to Embodiment 5 Configuration diagram of optical disk apparatus according to Embodiment 5 The figure which shows the flow of control of the optical pick-up apparatus of this Embodiment 5. 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 a mode that the reflected light from information recording surfaces other than the predetermined information recording surface of an optical disk injects into the conventional light receiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Optical disk 2a, 2b Information recording surface 2c Recording area 2d Unrecorded area 3 Hologram 3a, 3b Dividing line 3c, 3g, 3h, 3i Divided area 3d, 3e Tracking area 3f Focus area 4 Light receiver 4a, 4b Tracking light Detection surface 5, 6 Condensing spot 7, 8, 9, 10 Stray light spot 11 Laser light 11a, 11b, 11c Reflected light 11d Boundary line 20 Light receiver 20a, 20b Tracking light detection surface 21 Hologram 21a, 21b Tracking area 22, 23 Condensing spot 24, 25, 26, 27 Stray light spot 30 Light receiver 30a, 30b Tracking light detection surface 31 Hologram 31a, 31b Tracking region 32, 33 Condensing spot 34, 35, 36, 37 Stray light spot 40 Laser light source 40a Second Les Laser light source 41 Light receiver 41a, 41b, 41e, 41f, 41g, 41h, 41i, 41j Tracking light detection surface 41c, 41d Focus light detection surface 41k, 41l Temporary light emitting point 41m Second light receiver 42 Laser module 43 Diffraction element 44 Reflection mirror 45 Collimating lens 46 Rising mirror 47 Hologram 47a, 47b Dividing line 47c, 47d, 47e, 47f Dividing area 47g, 47h Tracking area 47i Focusing area 48 Hologram 48a, 48b Dividing line 48c, 48d Tracking area 48e, 48f, 48g 48h Focus area 49 1/4 wavelength plate 50 Hologram element 51 Objective lens 52 Front light monitor 53 DVD
54 CD
55 base 56 objective lens drive device 56a lens holder 57 optical pickup device 58, 59 cover 60 optical pickup module 61 base 62 spindle motor 63 feed motor 64 screw shaft 65, 66 guide shaft 67 optical pickup device 67a laser light source 67b light receiver 67c Objective lens 67d Front light monitor 67e Objective lens driving device 67f Laser light source driving power supply 68 Rack 69 Cover 70 Optical disk device 70a Optical disk device body 70b Analog signal processing unit 70c Servo processing unit 70d Motor driving unit 70e Controller 70f Digital signal processing unit 70g Laser driving Part 71 Case 71a Upper case 71b Lower case 72 Tray 73 Bezel 74 Eject switch 75 Rail 76 External Connector 80 host

Claims (32)

A laser light source for emitting laser light to a predetermined information recording surface of an optical disc having a plurality of information recording surfaces;
A hologram having a tracking region for reflecting light from an information recording surface other than the predetermined information recording surface of the optical disc into a predetermined projection shape;
The first light detection surface that receives the reflected light from the predetermined information recording surface of the optical disc and receives the partial area of the reflected light having the predetermined projection shape is the same as the reflected light of the partial area. A second photodetecting surface that receives the other partial area that is included in the reflected light and is adjacent to the reflected light of the partial area, and
The optical pickup device, wherein the first light detection surface is arranged on both sides of the second light detection surface. The optical pickup device according to claim 1, wherein the second light detection surface does not receive reflected light from the predetermined information recording surface of the optical disc. 2. The optical pickup device according to claim 1, wherein a plurality of the first light detection surfaces are provided in the light receiver, and the plurality of first light detection surfaces are arranged with the second light detection surfaces on both sides, respectively. 2. The optical pickup device according to claim 1, wherein the second light detection surfaces are arranged on both sides of the first light detection surface in a direction corresponding to a tangential direction of a circumference of the optical disc. A boundary between the first light detection surface and the second light detection surface is provided in a radial direction of the optical disc, and the other end of the second light detection surface is provided substantially parallel to the boundary. The optical pickup device according to claim 1. The width corresponding to the tangential direction of the circumference of the optical disc on the first photodetection surface is equal to or larger than the width corresponding to the tangential direction of the circumference of the optical disc on the second photodetection surface. 1. The optical pickup device according to 1. The width corresponding to the tangential direction of the circumference of the optical disc on the first light detection surface is approximately twice the width corresponding to the tangential direction of the circumference of the optical disc on the second light detection surface. The optical pickup device according to claim 6. 2. The optical pickup device according to claim 1, wherein an output of the light receiver from the first light detection surface is subtracted from an output of the light receiver from the second light detection surface. 2. The optical pickup device according to claim 1, wherein a plurality of sets of the first light detection surface and the second light detection surface are arranged in a direction corresponding to a radial direction of the optical disc. 2. The optical pickup device according to claim 1, wherein a plurality of sets of the first light detection surface and the second light detection surface are arranged in a direction corresponding to a tangential direction of a circumference of the optical disc. 2. The tracking area in the center of the hologram is divided by a dividing line in a direction corresponding to the tangential direction of the circumference of the optical disc, and the radial width of the optical disc is substantially constant. Optical pickup device. The first light detection surface and the second light detection surface have a first tracking light detection surface and a second tracking light detection surface, respectively, and the first tracking light detection surface of the first light detection surface is respectively The second tracking light detection surface of the second light detection surface is disposed on both sides, and the second tracking light detection surface of the first light detection surface is the first tracking light detection surface of the second light detection surface, respectively. The optical pickup device according to claim 1, wherein the optical pickup device is disposed on both sides. The difference between the output of the light receiver from the first tracking light detection surface and the output of the light receiver from the second tracking light detection surface is used for tracking control of the optical pickup device. 12. The optical pickup device according to 12. The tracking area includes a first tracking area and a second tracking area, and the reflected light from the predetermined information recording surface of the optical disc that has passed through the first tracking area is incident on the first tracking light detection surface. 13. The optical pickup device according to claim 12, wherein the reflected light from the predetermined information recording surface of the optical disc that has passed through the second tracking area is incident on the second tracking light detection surface. The hologram is divided into two divided regions approximately in half by a dividing line in a direction corresponding to the tangential direction of the circumference of the optical disc, and a center line in a direction corresponding to a radial direction that is a radial direction of the optical disc. The first tracking region is substantially line-symmetric, and the first tracking region has a peripheral portion of the hologram in a direction corresponding to the radial direction of the one divided region and a center of the hologram in a direction corresponding to the radial direction of the other divided region. The second tracking region is located at a peripheral portion of the hologram in a direction corresponding to the radial direction of the other divided region and a central portion of the hologram in a direction corresponding to the radial direction of the one divided region. The optical pickup device according to claim 14, wherein the optical pickup device is provided. The hologram is further divided into four divided regions approximately in four equal parts with the center line as a dividing line, and the light receiver has the first tracking light detection surface and the second tracking light detection surface for each of the four divided regions. 16. The optical pickup device according to claim 15, further comprising: 2. The optical pickup device according to claim 1, wherein the light receiver is used for either + 1st order light or -1st order light reflected from the information recording surface of the optical disc that has passed through the hologram. The hologram is divided into approximately four equal areas by a dividing line in a direction corresponding to the tangential direction of the circumference of the optical disc and a dividing line in a direction corresponding to the radial direction of the optical disc, and passes through the hologram. The second light receiver used for the other of the + 1st order light and the -1st order light reflected from the information recording surface of the optical disc has the third light detection surface on which the reflected light that has passed through the hologram is incident as the divided region. The optical pickup device according to claim 17, wherein the optical pickup device is provided for each. Almost all of the other of the + 1st order light and the -1st order light reflected from the predetermined information recording surface of the optical disc that has passed through each divided area of the hologram is incident on the third light detection surface. The optical pickup device according to claim 18. The light receiver has a focus light detection surface that receives reflected light from an information recording surface of the optical disk used for focus control of the optical pickup device, and the hologram is formed from the predetermined information recording surface of the optical disk. 19. The optical pickup device according to claim 18, further comprising a focus region for allowing either the + 1st order light or the -1st order light of the reflected light to enter the focus light detection surface. 21. The other of the + 1st order light and the −1st order light reflected from the predetermined information recording surface of the optical disc that has passed through the focus area is incident on the third light detection surface. Optical pickup device. The focus light detection surfaces are arranged such that the first focus light detection surface and the second focus light detection surface are alternately arranged so as to be substantially in contact with each other in a direction corresponding to the tangential direction of the circumference of the optical disc. The optical pickup device according to claim 20. Two sets of the focus light detection surfaces are arranged adjacent to each other in the direction corresponding to the tangential direction of the circumference of the optical disc, and the length of the focus light detection surface in the direction corresponding to the radial direction of the optical disc is the two sets. 23. The optical pickup device according to claim 22, wherein the optical pickup device is equal to or greater than a distance between centers of the focus light detection surfaces. The focus area includes an area that generates the reflected light that is incident on the focus light detection surface after being focused and an area that generates the reflected light that is incident on the focus light detection surface before being focused. The optical pickup device according to claim 20. A second laser light source that emits laser light toward the information recording surface of the second optical disc;
A main beam that is zero-order light and a side beam that is ± first-order light, which is disposed between the second laser light source and the second optical disc and diffracts the laser light emitted from the second laser light source; A diffraction grating separated into
A second hologram having a tracking region that passes reflected light from the information recording surface of the second optical disc and generates light in which at least one of the + 1st order light and the −1st order light is used for tracking control; Prepared,
Of the reflected light of the + 1st order light or the −1st order light that has passed through the tracking region of the second hologram, the side beam is incident on a fourth light detection surface of the light receiver,
21. The optical pickup device according to claim 20, wherein the main beam of the other reflected light is incident on the third light detection surface. The second hologram is roughly divided into four divided areas by dividing lines in the direction corresponding to the tangential direction of the circumference of the second optical disk and dividing lines in the direction corresponding to the radial direction of the second optical disk. 26. The light according to claim 25, wherein the tracking area is divided into two divided areas separated by a dividing line in a direction corresponding to a tangential direction of a circumference of the second optical disc. Pickup device. The second hologram has a focus region that passes through reflected light from the information recording surface of the second optical disc and generates light in which either + 1st order light or −1st order light is used for focus control, 27. The optical pickup device according to claim 26, wherein the focus area is the two divided areas other than the tracking area. 28. The main beam of the reflected light of either the + 1st order light or the −1st order light that has passed through the focus area of the second hologram is incident on the focus light detection surface. Optical pickup device. The focus light detection surface is arranged so that the first focus light detection surface and the second focus light detection surface are alternately arranged in contact with each other in a direction corresponding to the tangential direction of the circumference of the optical disc, and the focus light detection surface Two sets of surfaces are arranged adjacent to each other in a direction corresponding to the tangential direction of the circumference of the optical disc, and the position on the focus light detection surface where the reflected light that has passed through one focus region of the second hologram is incident Is shifted from the position on the focus light detection surface where the reflected light that has passed through the focus area of the hologram is incident by one of the first focus light detection surface or the second focus light detection surface. The optical pickup device according to claim 28. 28. The main beam of the other reflected light of the + 1st order light or the −1st order light that has passed through the focus area of the second hologram is incident on the third light detection surface. Optical pickup device. A plurality of sets of the first light detection surface and the second light detection surface are arranged in a direction corresponding to the radial direction of the optical disc, and the sets are shifted in a direction corresponding to the tangential direction of the circumference of the optical disc. The optical pickup device according to claim 30, wherein: A laser light source for emitting laser light to a predetermined information recording surface of an optical disc having a plurality of information recording surfaces;
A hologram having a tracking region that makes reflected light from an information recording surface other than the predetermined information recording surface of the optical disc that has passed through a predetermined projection shape;
The first light detection surface that receives the reflected light from the predetermined information recording surface of the optical disc and receives the partial area of the reflected light having the predetermined projection shape is the same as the reflected light of the partial area. A second photodetecting surface that receives the other partial area that is included in the reflected light and is adjacent to the reflected light of the partial area, and
The optical disc apparatus, wherein each of the first light detection surfaces includes an optical pickup device having the second light detection surfaces arranged on both sides.

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