JP3892449B2 - Optical pickup unit, optical pickup device including the same, and information recording / reproducing device - Google Patents

Description

  The present invention relates to an optical disc apparatus (information recording / reproducing apparatus) for optically recording or reproducing information on a recording medium such as an optical disc, and an optical pickup device and an optical pickup unit used therefor.

  In order to record a high-definition moving image, it is necessary to increase the capacity that can be recorded on one optical disk (recording medium). For this reason, it is conceivable to provide a plurality of recording layers (information recording layers) on the optical disk. ing. At present, a read-only disc such as a DVD-ROM or DVD-Video has already been commercialized and has become popular in the market. In addition, for optical discs capable of recording information, standards for single-sided dual-layer recording optical discs have been announced, and commercialization is also a time issue.

  By the way, in the case of an optical disc having a plurality of recording layers, unnecessary reflected light (stray light) from recording layers other than the recording layer on which information is recorded / reproduced (hereinafter referred to as non-target layer) becomes a problem. Specifically, when light is detected in a state where light reflected by a recording layer (hereinafter referred to as a target layer) on which information is recorded / reproduced overlaps light reflected by a non-target layer Will not be able to determine the exact amount of light.

  For such problems, for example, techniques disclosed in Patent Documents 1 and 2 have been proposed.

  In the above-mentioned Patent Document 1, an auxiliary light receiving region for receiving only the light reflected by the non-target layer is provided in the light receiving unit for receiving the light reflected by the recording layer, in addition to the main light receiving region for receiving the light reflected by the target layer. A method is disclosed that detects the influence of only the stray light component and suppresses the influence of the stray light mixed in the focus signal.

Patent Document 2 discloses a technique for suppressing crosstalk between a reproduction signal and a focus signal by providing an auxiliary light receiving unit that receives reflected light (stray light) from a non-target layer, as in Patent Document 1. Has been.
Japanese Patent No. 3372413 (Japanese Patent Laid-Open No. 9-0161282 (publication date: June 20, 1997)) JP 2002-319177 A (publication date: October 31, 2002)

  However, unlike a read-only (reproduction) disc, in the case of a recordable disc, crosstalk to the tracking signal becomes a problem.

  In the case of a recording disk, a differential push-pull method (hereinafter referred to as DPP) using three beams is generally employed as a tracking method. The DPP method is a method of obtaining a tracking signal having no offset by taking a differential between a push-pull signal of a main beam and a push-pull signal of front and rear sub-beams.

  For example, when information is recorded on a DVD ± R disk using the above three beams, the recording speed is proportional to the square of the light intensity of the main beam. It needs to be as large as possible. Therefore, when information is recorded on the DVD ± R disc, the intensity ratio of the main beam and the sub beam is set to, for example, 10: 1 or 15: 1, so that the light intensity of the sub beam becomes considerably small. . Therefore, the detector for detecting the sub beam detects a light beam having a light intensity much smaller than that of the main beam.

  On the other hand, when reproducing information or recording information on an optical disc on which a plurality of recording layers are laminated, the reflected light reflected by a non-target layer other than the information reproducing (recording) layer enters the light receiving section as stray light To do. These stray lights include main beam stray light and sub-beam stray light. Then, the stray light passes through the condensing optical system and is incident on the light receiving unit because it is defocused by the interval between the recording layers, and information is reproduced (recorded) without being reduced. Compared with the light beam irradiated from the layer, the light beam is irradiated in a considerably large light beam state. The stray light has a considerably small light density (light intensity per unit area), and does not have a great influence even if it is incident on the main beam light receiving unit that receives the main beam.

  However, the sub-beam light receiving unit that receives the sub-beam receives a light beam having a very small light intensity (light density) with respect to the main beam. Specifically, as described above, the light intensity of the sub beam is as small as 1/10 or less of the light intensity of the main beam, and the sub beam light-receiving unit receives the light beam having such light intensity. Therefore, when the sub-beam light receiving unit receives the stray light, particularly the stray light of the main beam having a high light intensity among the stray light, the light intensity is smaller than the light beam emitted from the layer for reproducing (recording) information. Even stray light has a great influence on the intensity of light received by the light receiving unit, and as a result, a large offset is generated in the DPP signal. In particular, when the stray light of the main beam having a light intensity higher than that of the sub beam is incident on the sub beam light receiving unit, there is a problem that an accurate tracking signal cannot be obtained.

  The present invention has been made in view of the above problems, and its object is to perform recording and / or reproduction of information on a recording medium in which a plurality of recording layers are laminated as compared with the conventional one. Another object of the present invention is to provide an optical pickup unit, an optical pickup device, and an information recording / reproducing device that can perform tracking control accurately and stably.

  In order to solve the above problems, an optical pickup unit according to the present invention is configured to obtain at least a focus servo signal from a main beam reflected from a recording medium on which a plurality of information recording layers are laminated and passed through a light collecting unit. A main beam for focusing and a main beam for tracking for obtaining a tracking servo signal are separated, and at least a sub beam reflected from the recording medium and having a light intensity smaller than that of the main beam that has passed through the condensing means, An optical pickup unit, comprising: a separating unit that separates a tracking sub-beam for obtaining a tracking servo signal from another sub-beam; and a tracking light-receiving unit that receives the tracking main beam and the tracking sub-beam. The stage has a sub light receiving portion that receives the tracking sub beam, and a main beam for focus reflected by an information recording layer other than the information recording layer that performs recording / reproduction of information enters the sub light receiving portion. In order to prevent this, a tracking light receiving means is arranged.

  The sub beam has a light intensity smaller than that of the main beam. The sub light receiving unit receives the sub beam with low light intensity as described above. Therefore, when the sub light receiving unit receives stray light (unnecessary light) emitted in addition to the tracking sub beam, an error of a signal generated by the sub light receiving unit is likely to occur.

  A light beam (main beam and sub beam) reflected from an information recording layer (hereinafter referred to as a non-target layer) other than the information recording layer performing information recording / reproduction (recording and / or reproduction) is an optical path. Due to the difference in length, compared with the light beam that has passed through the light collecting means and reflected from the information recording layer (hereinafter referred to as the target layer) that is recording / reproducing information (recording and / or reproducing). The area irradiated to the light receiving means increases. Accordingly, the intensity of light per unit area of the light beam reflected by the non-target layer is smaller than that of the light beam reflected by the target layer. However, the main beam has higher light intensity than the sub beam, and the main beam reflected by the non-target layer is close to the light intensity of the sub beam reflected by the target layer. When the focusing main beam reflected by the non-target layer is incident on the sub light receiving unit, the sub light receiving unit cannot obtain an accurate signal due to the intensity of the light.

  According to the above configuration, the tracking light receiving means is disposed so that the focusing main beam reflected by the non-target layer does not enter the sub light receiving portion. That is, the focusing main beam reflected by the non-target layer does not enter the sub light receiving unit. Therefore, the tracking control can be performed reliably and stably as compared with the conventional configuration in which the focus main beam is not considered to be incident on the sub light receiving unit.

  The separating means may separate the light beam into, for example, the focusing light beam, the tracking light beam, and the reproducing light beam for obtaining a reproducing signal. The separating means may obtain a reproduction signal using the focusing light beam when separating the light beam into the focusing light beam and the tracking light beam, or A reproduction signal may be obtained using a tracking light beam.

  The separating means of the optical pickup unit according to the present invention separates the sub beam into a tracking sub beam for obtaining a tracking servo signal and a sub beam other than the tracking sub beam. A configuration in which the tracking light receiving means is arranged so that the main beam for focusing and other sub beams reflected by the information recording layer other than the information recording layer being reproduced does not enter the sub light receiving unit is more preferable.

  The other sub-beams indicate sub-beams other than the tracking sub-beam used for obtaining the tracking servo signal among the sub-beams separated by the separating means.

  According to the above configuration, it is possible to prevent the sub light-receiving unit from being irradiated with light beams other than the tracking sub beam and the tracking main beam for obtaining the tracking servo signal (focusing main beam and other sub beams). More specifically, among the light beams reflected from the non-target layer, a light beam other than the tracking light beam can be prevented from irradiating the sub light receiving unit, so that more accurate and stable tracking control is performed. be able to.

  The tracking light receiving means of the optical pickup unit according to the present invention receives only the tracking main beam and / or the tracking sub beam reflected by the information recording layer other than the information recording layer for recording / reproducing the information. The structure provided with the auxiliary light-receiving part to perform is more preferable.

  The tracking main beam and / or the tracking sub-beam reflected by the non-target layer is reflected by the target layer because the area irradiated on the light receiving means is larger than the tracking sub-beam reflected by the target layer. Along with the sub beam for tracking, the light enters the sub light receiving portion. Therefore, the amount of light (light intensity) received by the sub light receiving unit is influenced by the tracking main beam and / or the tracking sub beam reflected by the non-target layer.

  According to the above configuration, the auxiliary light receiving unit that receives only the tracking main beam and / or the tracking sub beam reflected by the non-target layer is provided. As a result, the degree of influence of the tracking main beam and / or the tracking sub beam reflected by the non-target layer can be known, and the influence of this can be eliminated.

  The tracking light receiving means of the optical pickup unit according to the present invention further includes a main light receiving portion for receiving the tracking main beam, and the light receiving area of the auxiliary light receiving portion is greater than the light receiving area of the sub light receiving portion. A smaller configuration is more preferable.

  The tracking servo signal is calculated according to a differential push-pull method (a method for obtaining a tracking servo signal with three beams) according to the amount of light incident on the main light receiving unit and the sub light receiving unit.

  According to the above configuration, the light receiving area of the auxiliary light receiving unit is smaller than the light receiving area of the sub light receiving unit. As a result, when the interlayer crosstalk is removed using the differential push-pull method, the light amount detected from the auxiliary light receiving unit is used to combine the offset generated in the sub light receiving unit and the offset generated in the main light receiving unit. Interlayer crosstalk can be removed in the same manner. Therefore, since the interlayer crosstalk can be removed without providing a detector (light receiving unit) that detects an offset generated in the main light receiving unit, the optical pickup unit can be reduced in size. The light receiving area indicates a region that actually receives a light beam.

  In the tracking light receiving means of the optical pickup unit according to the present invention, the main beam for focusing and other sub beams reflected by the information recording layer other than the information recording layer for recording / reproducing the information are the auxiliary light receiving unit. It is more preferable that the structure is arranged so as not to enter the light.

  According to the above configuration, since the auxiliary light receiving unit is disposed at a position where the main beam for focusing reflected by the non-target layer and other sub beams are not incident, the auxiliary light receiving unit includes the tracking main beam and / or Only the tracking sub-beam can be received. Thereby, more accurate and stable tracking control can be performed.

  The separation means of the optical pickup unit according to the present invention collects the main beam and the sub beam reflected by the information recording layer farther than the information recording layer that is recording / reproducing information as viewed from the light collecting means. A configuration in which the main beam for tracking and the sub beam for tracking are separated in a region excluding the lighted region is more preferable.

  Of the non-target layer, the light beam reflected by the information recording layer farther from the light collecting means than the target layer is reflected by the target layer on the separating means due to the difference in the optical path length of the light beam. As compared with the region of the light beam focused on, the light is focused on a small region. According to the above configuration, the separation unit is a region other than a region where the light beam reflected by the information recording layer farther than the target layer is collected as viewed from the light collecting unit (that is, the small region). The tracking light beam is separated using a region excluding (1). Thereby, it is possible to prevent the tracking light receiving unit from being irradiated with the light beam reflected by the information recording layer farther from the light collecting unit than the target layer. Therefore, it is not necessary to provide an auxiliary light receiving portion for receiving the light beam reflected by the information recording layer farther from the light collecting means than the target layer.

  The separating means may be configured to separate the tracking light beam (tracking main beam and tracking sub beam) in a region excluding the region near the optical axis of the light beam reflected by the recording medium. .

  In addition, the tracking light receiving unit is configured to record information farther than the information recording layer in which information is recorded / reproduced as viewed from the light collecting unit in the separation region where the separation unit separates the main beam and the sub beam. A configuration may be adopted in which the main beam and the sub beam separated in the region excluding the region where the main beam and the sub beam reflected by the layer are collected by the separation unit are received.

  More preferably, the separation means of the optical pickup unit according to the present invention is a hologram.

  With the above structure, the light beam can be separated with a simple structure, and thus the apparatus can be downsized.

  An optical pickup unit according to the present invention includes the separation unit, the light receiving unit, a light source that irradiates a recording medium with a light beam, and a generation unit that generates a main beam and a sub beam from the light beam emitted from the light source. Is more preferable.

  According to the above configuration, since the separating unit, the light receiving unit, the light source, and the generating unit are integrated, the optical pickup unit can be reduced in size.

  An optical pickup device according to the present invention includes the above optical pickup unit.

  According to the above configuration, since the optical pickup unit is provided, information can be reproduced / recorded satisfactorily even with a recording medium having a plurality of information recording layers.

  An information recording / reproducing apparatus according to the present invention includes the optical pickup unit.

  According to the above configuration, since the optical pickup unit is provided, information can be reproduced / recorded satisfactorily even with a recording medium having a plurality of information recording layers.

  An optical pickup unit according to the present invention includes a main beam for focusing and a tracking servo signal for obtaining at least a focus servo signal from a main beam reflected from a recording medium in which a plurality of information recording layers are laminated and passed through a light collecting unit. And a tracking sub-beam for obtaining at least a tracking servo signal for a sub-beam reflected from the recording medium and having a light intensity smaller than that of the main beam that has passed through the light collecting means. And an optical pickup unit that receives the tracking main beam and the tracking sub beam. The tracking light receiving unit receives the tracking sub beam. The tracking light receiving means is arranged so that the main beam for focus reflected by the information recording layer other than the information recording layer that has a light receiving portion and records / reproduces information is not incident on the sub light receiving portion. It is the composition which is.

  Therefore, the focusing main beam reflected by the non-target layer does not enter the sub light receiving unit. Therefore, the tracking control can be performed reliably and stably as compared with the conventional configuration in which the focus main beam is not considered to be incident on the sub light receiving unit.

[Embodiment 1]
An embodiment of the present invention will be described as follows. The optical pickup device according to the present embodiment is an optical pickup device for recording / reproducing information with respect to an optical disc (recording medium) having a plurality of information recording layers (hereinafter referred to as recording layers). The light intensity (light density) is smaller than that of the main beam and the main beam, which is reflected from the optical disk, separated by the separating means into at least a focusing light beam and a tracking light beam after passing through the light collecting means. A focusing light beam reflected by a recording layer other than the recording layer that has a light receiving means for receiving each sub beam and that has a sub beam light receiving area and a main beam light receiving area and that records / reproduces information. The sub beam light receiving region is arranged so that the main beam is not incident on the sub light receiving unit.

  In the following description, among recording media having a plurality of recording layers, recording layers other than the recording layer on which information is recorded / reproduced by the optical pickup device are used as non-target layers, and information is recorded / reproduced. The recording layer is described as a target layer. That is, the recording layer other than the target layer is a non-target layer.

  FIG. 2 is a side view showing a schematic configuration of the optical pickup device 7 according to the present embodiment. The optical pickup device 7 includes a laser light source (light source) 1, a diffraction unit (generation unit) 2, an objective lens (condensing unit) 3, a beam splitter 10, a hologram 5 (separation unit), and a light receiving unit (light reception unit) 6. ing.

  The laser light source 1 irradiates the optical disc 4 with laser light. The laser light source 1 emits a laser beam (light beam) having a wavelength of 650 nm, for example. Note that the wavelength of the light beam emitted from the laser light source 1 is not particularly limited, and may be, for example, 405 nm.

  The diffractive portion 2 is disposed between the laser light source 1 and the optical disk 4, and from one light beam emitted from the laser light source 1, one main beam (0th order transmitted light) and two sub beams (+1). Order diffracted light, -1st order diffracted light). That is, the light beam emitted from the laser light source 1 becomes three light beams in the diffraction unit 2. In the present embodiment, the diffraction section 2 is provided between the laser light source 1 and the objective lens 3 (more specifically, between the laser light source 1 and the beam splitter 10). The diffraction unit 2 generates two types of light beams so that the main beam is larger than the light intensity of the sub beam. More specifically, the diffraction unit 2 generates the main beam and the sub beam so that the light amount of the main beam is larger than the sum of the light amounts of the + 1st order diffracted light and the −1st order diffracted light that are two sub beams. is doing. In the present embodiment, the diffracting unit 2 diffracts the light beam so that the respective light amounts are + 1st order diffracted light: 0th order transmitted light: −1st order diffracted light = 1: 10: 1. When the diffractive portion 2 is composed of a diffraction grating, the ratio of 0th-order transmitted light and ± 1st-order diffracted light can be controlled by the depth of the groove of the diffraction grating.

  The objective lens 3 focuses the three light beams diffracted by the diffraction unit 2 on the optical disk 4. Further, the light beam reflected by the optical disk 4 passes through the objective lens 3 and enters the hologram 5.

  The beam splitter 10 guides three light beams (one main light beam and two sub light beams) reflected from the optical disc 4 to the hologram 5. In the present embodiment, the three light beams that have been reflected by the optical disk 4 and passed through the objective lens 3 are guided to the hologram 5 with their traveling directions changed by the beam splitter 10.

  The hologram 5 separates the light beam reflected by the optical disk 4 and passed through the objective lens 3. The hologram 5 is divided into a plurality of regions, and the light beam that has passed through the objective lens 3 is divided by the divided regions and is incident on the light receiving unit 6. Specifically, the light beam is separated by the hologram 5 into at least a focusing light beam for obtaining a focus servo signal and a tracking light beam for obtaining a tracking servo signal. The detailed configuration of the division pattern of the hologram 5 and the light receiving unit will be described later.

  The light receiving unit 6 has a plurality of light receiving elements, and receives (detects) the light beams (focusing light beam and tracking light beam) separated by the separating means and converts them into electrical signals. The light receiving unit 6 detects the light intensity of the received light beam. The light receiving section 6 includes a focusing light receiving section 6A that receives the focusing light beam, and tracking light receiving sections (tracking light receiving means) 6B and 6C that receive the tracking light beam. The focus light receiving unit 6A generates a focus servo signal, and the tracking light receiving units 6B and 6C generate tracking servo signals.

  Next, the light beam emitted from the laser light source 1 will be described. The light beam emitted from the laser light source 1 is diffracted into three light beams by the diffraction unit 2, passes through the beam splitter 10, and is condensed on the optical disk 4 by the objective lens 3.

  The light beam reflected by the optical disk 4 again passes through the objective lens 3, is reflected by the beam splitter 10, is split into three or more light beams by the hologram 5, and enters the light receiving unit.

  Here, a detailed configuration of the hologram 5 and the light receiving unit will be described. FIG. 3 is a front view showing a separation region (separation pattern) of the hologram 5. The direction of the arrow in the figure indicates the track direction.

  As shown in FIG. 3, the hologram 5 is divided into three regions (5A, 5B and 5C). The region 5A is divided into two by a straight line including the optical axis centered on the optical axis of the light beam when the hologram 5 is irradiated with the main beam (indicated by a dotted line in the figure). On the other hand. More specifically, the area 5A is a straight line in a direction orthogonal to the track direction (hereinafter referred to as an orthogonal straight line) including the optical axis of the main beam irradiated on the hologram 5 in the separation area of the hologram 5. This is one of the divided areas.

  The region 5B and the region 5C are regions other than the region 5A among the separation regions of the hologram 5, and are straight lines including the optical axis of the light beam and parallel to the track direction (hereinafter referred to as parallel straight lines). And an area surrounded by the orthogonal straight line. That is, of the four areas divided by the orthogonal straight line and the parallel straight line with the optical axis as the center, two adjacent areas among the areas divided by the parallel straight lines are the areas 5B and 5C, and are orthogonal. One area divided by the straight line is the area 5A.

  Of the three divided areas, the light beam divided in the area 5A is a focus light beam for obtaining a focus servo signal, and the two light beams divided in the areas 5B and 5C are A tracking light beam for obtaining a tracking servo signal. The focusing light beam is applied to the focusing light receiving unit 6A, and the tracking light beam is applied to the tracking light receiving units 6B and 6C.

  The main beam divided in the area 5A is a focus main beam for obtaining a focus servo signal, and the two main beams divided in the areas 5B and 5C are tracking for obtaining a tracking servo signal. Main beam. The sub beam divided in the region 5A is another sub beam (referred to as a focus sub beam for convenience of description), and the two sub beams divided in the regions 5B and 5C are tracking for obtaining a tracking servo signal. For sub-beams. In the following description, when the main beam and the sub beam are not particularly distinguished, the light beam incident on the light receiving unit 6 will be referred to as a focusing light beam and a tracking light beam.

  FIG. 4 is a front view showing a detailed configuration of the light receiving unit 6. As shown in FIG. 4, the light receiving unit 6 includes a focusing light receiving unit 6A that receives the focusing light beam, and tracking light receiving units 6B and 6C that receive the tracking light beam. Specifically, the focusing light receiving unit 6A receives a focusing light beam (focusing main beam) separated in the region 5A of the hologram 5, and the tracking light receiving unit 6B The tracking light beam separated at 5B is received, and the tracking light receiving unit 6C receives the tracking light beam separated at the region 5C.

The tracking light receiving parts 6B and 6C include light receiving elements for receiving one main beam and two sub beams diffracted by the diffraction part 2, respectively. Specifically, the tracking light-receiving units 6B and 6C include the main light-receiving units 6B-0 and 6C-0 that receive the tracking main beam that is the 0th-order transmitted light, and two tracking light beams that are ± first-order diffracted light. Sub-light-receiving portions 6B-1, 6B-2 and 6C-1, 6C-2 that receive the sub beams are provided. The main light receiving unit 6B-0 and the sub light receiving units 6B-1 and 6B-2 (6C-0, 6C-1 and 6C-2) have the main light receiving unit 6B-0 (6C-0) in the middle. The sub light receiving portions 6B-1 and 6B-2 (6C-1 and 6C-2) are arranged so as to be adjacent to each other so as to extend in the track direction. In the above description, the main beam and the sub beam are light beams reflected by the target layer. Also,
Further, in the present embodiment, the tracking light receiving unit 6B (6C) is the main light receiving unit 6B-0 (6C-0) of the sub light receiving units 6B-1 and 6B-2 (6C-1 and 6C-2). Auxiliary light receiving portions 6B-11 and 6B-12 (6C-11 and 6C-12) disposed on the opposite side. The auxiliary light receiving sections 6B-11 and 6B-12 (6C-11 and 6C-12) receive only the light beam reflected by the non-target layer (hereinafter referred to as stray light). That is, when the optical disc 4 is a single layer, light does not enter the auxiliary light receiving units 6B-11 and 6B-12 (6C-11 and 6C-12).
Then, five light receiving units (auxiliary light receiving unit 6B-11, sub light receiving unit 6B-1, main light receiving unit 6B-0, sub light receiving unit 6B-2, auxiliary light receiving unit that receives the tracking light beam separated in region 5B. The light receiving unit 6B-22) and the five light receiving units (6C-11, 6C-1, 6C-0, 6C-2, 6C-22) that receive the tracking light beam separated in the region 5C are used for tracking. Arranged in the above order along the direction. The tracking light receiving parts 6B and 6C are arranged on the same side as viewed from the focusing light receiving part 6A. By arranging the tracking light receiving portions 6B and 6C so as to be adjacent to each other, the size of the light receiving portion 6 can be reduced. In the above description, stray light refers to the main beam and the sub beam reflected by the non-target layer.

  FIG. 5 is a diagram illustrating a light beam incident on the light receiving unit 6 when the main beam and the sub beam reflected on the target layer are incident on the hologram 5. As shown in FIG. 5, the main beam 8 that is zero-order transmitted light is incident so that the optical axis thereof is the center of the hologram 5. Further, the sub beams 8 + 1 and 8-1 which are ± 1st order diffracted lights are respectively incident so as to partially overlap the 0th order transmitted light. In addition, the dotted line in a figure has shown the straight line (an orthogonal straight line, a parallel straight line) containing an optical axis.

  The main beam 8 diffracted in the region 5A is incident on the focus light receiving unit 6A. Further, the sub-beams 8 + 1 and 8-1 diffracted in the region 5A are incident on a place where the light receiving unit 6 is not provided with the light receiving unit 6A for focusing interposed therebetween. That is, the sub beams 8 + 1 and 8-1 diffracted in the region 5A are not used for obtaining the focus servo signal and the tracking servo signal.

  On the other hand, the main beam 8 diffracted in the region 5B (5C) is incident on the main light receiving unit 6B-0 (6C-0) which is the tracking light receiving unit 6B (6C). Further, the sub beams 8 + 1 and 8-1 diffracted in the region 5B (5C) are incident on the sub light receiving units 6B-1 and 6B-2 (6C-1 and 6C-2), respectively.

Here, a method of calculating a tracking servo signal (tracking error signal, referred to as TES in the following description) using a differential push-pull method (hereinafter referred to as DPP method) when the optical disc 4 is a single layer. explain. The DPP method is often used particularly in the case of the recordable optical disk 4. In the DPP method, the light amount detected by the main light receiving unit 6B-0 is "6B-0", the light amount detected by the main light receiving unit 6C-0 is "6C-0", and the sub light receiving units 6B-1 and 6B The light amounts detected at -2 are "6B-1" and "6B-2", and the light amounts detected by the sub light receiving units 6C-1 and 6C-2 are "6C-1" and "6C-2", respectively. When the above TES is expressed by the following formula (1),
TES = (“6B-0” − “6C-0”) − K × {(“6B−1” + “6B-2”) − (“6C-1” + “6C-2”)}} ( 1)
Obtained by the following equation. Note that K is an arbitrary coefficient obtained from the difference in light quantity between the main beam and the sub beam.

  That is, the difference between the main beam and the sub beam separated in the region 5B and the region 5C is calculated, and the tracking servo signal is obtained by taking these differences.

  Next, stray light (a main beam and a sub beam reflected by a non-target layer) generated in the optical disc 4 on which a plurality of recording layers are stacked will be described. FIG. 6 is a side view showing the optical path difference between the light beam reflected from the target layer and stray light closer to the objective lens 3 than the target layer. FIG. 7 is a front view showing respective spots when the light beam reflected from the target layer and the stray light whose distance from the objective lens 3 is closer than that of the target layer are applied to the hologram 5 and the light receiving unit 6. It is. In the drawing, the light beam reflected from the target layer is indicated by a dotted line. In the following description, a two-layer disc will be described, but the number of recording layers is not particularly limited.

  As shown in FIG. 6, the light beam (hereinafter referred to as near-side stray light) 8n from the recording layer (non-target layer) on the objective lens 3 side of the target layer and the light beam 8 from the target layer The area of the light beam incident on the hologram 5 and the light receiving unit 6 varies depending on the difference in length. Specifically, as shown in FIG. 7, the near-side stray light 8 n incident on the hologram 5 and the light receiving unit 6 has an irradiation area larger than that of the light beam 8 due to the difference in optical path length and the influence of the objective lens 33. . That is, the near-side stray light 8 n is larger than the light beam 8 in the spots formed on the hologram 5 and the light receiving unit 6.

  In FIG. 7, the light beam 8 and the near-side stray light 8n have a main beam and a sub-beam, respectively, due to the diffraction unit 2, but for convenience of explanation, only the 0th order transmitted light is used for the near-side stray light 8n. Show. In the embodiment, 0th-order transmitted light >> ± 1st-order diffracted light is used, and in the following description, only 0th-order transmitted light that has a strong influence on offset (a large amount of light) will be described.

  As shown in FIG. 7, the near-side stray light 8n separated in the region 5A enters the light receiving unit 6A as the focus near-side stray light 8nA. At this time, the focus near side stray light 8nA has a larger spot size formed on the light receiving portion 6A than the light beam 8 separated in the region 5A. The near-side stray light 8n separated in the region 5B (5C) is incident on the main light receiving unit 6B-0 (6C-0) as tracking near-side stray light 8nB (8nC). At this time, the tracking near side stray light 8nB (8nC) has a larger spot size formed on the main light receiving portion 6B-0 (6C-0) than the light beam 8 separated in the region 5B (5C). Become. The tracking near-side stray light 8nB (8nC) is transmitted to the sub light receiving unit 6B-2 (6C-2) and the auxiliary light receiving unit 6B-12 (6C-2) because of the irradiation area of the light beam. Is also irradiated.

That is, since the tracking near side stray light 8nB (8nC) is incident on the sub light receiving unit 6B-2 (6C-2), the TES is expressed by the following equation (2),
TES = (“6B-0” − “6C-0”) − K × {(“6B−1” + “6B-2” + Δb2) − (“6C-1” + “6C-2” + Δc2)}} ... (2)
It becomes. The Δb2 (Δc2) indicates an offset generated when the tracking near side stray light 8nB (8nC) is incident on the sub light receiving unit 6B-2 (6C-2).

  Here, if Δb2 = Δc2, an unnecessary offset does not occur in the TES. Actually, however, tracking near side stray light 8 nB (8 nC) in the left-right direction (radial direction) in the figure due to the influence of the pickup assembly error or the like. Therefore, Δb2 ≠ Δc2, and an offset of K × (Δb2−Δc2) is generated.

  Therefore, the offset is obtained by subtracting the output of the auxiliary light receiving unit 6B-12 (6C-12) that detects only the tracking near side stray light 8nB (8nC) from the output of "6B-2" ("6C-2"). Can be canceled.

  On the other hand, FIG. 8 is a side view showing the optical path difference between the light beam reflected from the target layer and the stray light farther from the objective lens 3 than the target layer. FIG. 9 is a front view showing respective spots when the light beam reflected from the target layer and the stray light far from the objective lens 3 than the target layer are irradiated on the hologram 5 and the light receiving unit 6. It is. In the drawing, the light beam reflected from the target layer is indicated by a dotted line.

  As shown in FIG. 8, the light beam (hereinafter referred to as far-side stray light) 8f from the recording layer (non-target layer) on the side opposite to the objective lens 3 side of the target layer and the light beam 8 from the target layer are as shown in FIG. The area of the light beam incident on the hologram 5 and the light receiving unit 6 differs depending on the difference in optical path length between the two. Specifically, as shown in FIG. 9, the far-side stray light 8 f incident on the hologram 5 is in front of the light receiving unit 6 (between the light receiving unit 6 and the hologram 5 due to the difference in the optical path length and the influence of the objective lens 33. ) To focus on. Therefore, the far-side stray light 8f incident on the hologram 5 has a smaller irradiation area than the light beam 8, while the far-side stray light 8f incident on the light receiving unit 6 has a larger irradiation area than the light beam 8. Become. In other words, the far side stray light 8 f is smaller in the spot formed on the hologram 5 than the light beam 8, but the far side stray light 8 f is larger in the spot formed on the light receiving unit 6 than the light beam 8.

  Further, as shown in FIG. 9, the far-side stray light 8f separated in the region 5A enters the light receiving unit 6A as the focus far-side stray light 8fA. At this time, the size of the spot formed on the light receiving portion 6A of the focus fur side stray light 8fA is larger than that of the light beam 8 separated in the region 5A. Further, the far-side stray light 8f separated in the region 5B (5C) enters the main light receiving unit 6B-0 (6C-0) as tracking far-side stray light 8fB (8fC). At this time, the tracking fur side stray light 8fB (8fC) has a larger spot size formed on the main light receiving portion 6B-0 (6C-0) than the light beam 8 separated in the region 5B (5C). Become. The tracking far side stray light 8fB (8fC) is also transmitted to the sub light receiving unit 6B-1 (6C-1) and the auxiliary light receiving unit 6B-11 (6C-11) due to the size of the irradiation area of the beam. Irradiated.

Since the tracking far side stray light 8fB (8fC) is incident on the sub light receiving unit 6B-1 (6C-1), the TES is expressed by the following equation (3),
TES = ("6B-0"-"6C-0")-K x {("6B-1" + Δb1 + "6B-2")-("6C-1" + Δc1 + "6C-2")} ( 3)
It becomes. Δb1 (Δc1) indicates an offset generated when the tracking fur side stray light 8fB (8fC) is incident on the sub light receiving unit 6B-1 (6C-1).

  Here, if Δb1 = Δc1, an unnecessary offset does not occur in the TES, but in reality, Δb1 ≠ Δc1 due to the influence of the pickup assembly error and the like, and therefore an offset of K × (Δb1−Δc1) occurs. Will be.

  Therefore, the offset is obtained by subtracting the output of the auxiliary light receiving unit 6B-11 (6C-11) that detects only the tracking fur side stray light 8fB (8fC) from the output of “6B-1” (“6C-1”). Can be canceled.

  Here, the positional relationship between the focus light receiving unit 6A and the tracking light receiving units 6B and 6C will be described.

  The light receiving unit 6 according to the present embodiment receives the focus light so that the focus main beam reflected by the non-target layer is not incident on the sub light receiving units 6B-1 and 6B-2 (6C-1 and 6C-2). A portion 6A and tracking light receiving portions 6B and 6C are arranged.

  FIG. 1 is a front view showing the arrangement of the focus light receiving section 6A and the tracking light receiving sections 6B and 6C according to the present embodiment. The direction of the arrow in the figure indicates the track direction.

  In the present embodiment, as shown in FIG. 1, the main light receiver 6B-0 (6C-0), the sub light receivers 6B-1, 6B-2 (6C-1, 6C-2), and the auxiliary light receiver The parts 6B-11 and 6B-12 (6C-11 and 6C-12) are arranged at positions where the focus fur side stray light 8fA applied to the light receiving part 6 is not incident. More specifically, the tracking light receiving unit 6B (6C) is disposed so that the main beam for focusing and the sub beam for focusing reflected from the non-target layer do not enter.

  As a result, the focusing main beam and the focusing sub beam reflected by the non-target layer can be prevented from entering the tracking light receiving unit 6B (6C). It is possible to prevent an offset generated by entering 6B (6C). Thereby, a more accurate tracking servo signal can be obtained. Therefore, the tracking control can be performed reliably and stably as compared with the conventional configuration. That is, when information is recorded / reproduced on / from the optical disc 4 on which a plurality of recording layers are laminated, it is possible to suppress the influence of the reflected light from the non-target layer and realize tracking control that is more stable than before.

  The information recording / reproducing apparatus including the optical pickup device 7 can perform tracking control reliably and stably as compared with the conventional configuration.

In addition, by integrating the laser light source 1, the diffracting unit 2, the hologram 5 and the light receiving unit 6 into an optical pickup unit, it is possible to reduce the size of the optical pickup device. In this embodiment, the optical pickup unit is formed by integrating the laser light source 1, the diffracting unit 2, the hologram 5, and the light receiving unit 6, but it is sufficient that at least the four members are provided. And what has the said optical pick-up unit and the objective lens 3 (and the drive source which drives the objective lens 3) is an optical pick-up apparatus.
[Embodiment 2]
Another embodiment of the present invention will be described as follows. For convenience of explanation, members having the same functions as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the optical pickup device 7 according to the present embodiment, an example in which the division pattern of the hologram 5 is different will be described.

  FIG. 10 is a front view showing respective spots when the light beam reflected from the target layer and the stray light whose distance from the objective lens 3 is closer than the target layer are applied to the hologram 5 and the light receiving unit 6. . In the drawing, the light beam reflected from the target layer is indicated by a dotted line.

  In the hologram 5 according to the present embodiment, the shape of the region 5B and the region 5C for separating the light beam for obtaining the tracking servo signal is a region not including the region near the optical axis of the main beam. Specifically, the regions 5B and 5C, which are regions for separating the light beam reflected from the optical disc 4 in the hologram 5, are the main beams reflected by the non-target layer farther from the target layer as viewed from the objective lens 3. And it is an area | region except the area | region where a sub beam is condensed. More specifically, the tracking servo signal is obtained in a region excluding a portion larger than the maximum value of the stray light beam diameter farther from the objective lens 3 than the objective layer. The large portion indicates a portion where stray light farther than the target layer does not protrude even when the objective lens 3 moves during tracking.

  Specifically, for example, when the diameter of the light beam reflected from the optical disk 4 on the hologram 5 is 600 μm, tracking is performed using a region excluding a circular portion having a radius of about 130 μm (diameter 260 μm) from the optical axis. What is necessary is just to obtain | require a servo signal. The above numerical values differ depending on the configuration of the optical system (focal length / numerical aperture of the objective lens 3, division pattern of the hologram 5, etc.).

  Therefore, the tracking light beam that has passed through the region 5B and the region 5C of the hologram 5 becomes a donut-shaped hollow quarter on the light receiving unit, and becomes the main light receiving unit 6B-0 (6C-0). ), The sub light receiving unit 6B-2 (6C-2) and the auxiliary light receiving unit 6B-12 (6C-12). Therefore, as shown in FIG. 10, the tracking light beam that has passed through the region 5B (5C) of the hologram 5 and reflected from the target layer is the main light receiving unit 6B-0 (6C-0) and the sub light receiving unit 6B-. 2 (6C-2) is incident in the shape of a hollow quarter. Also, tracking near side stray light 8nB (8nC) is incident in the same manner.

  On the other hand, the region 5A of the hologram 5 is a region including the region near the optical axis. Then, the focusing light beam that has passed through the region 5A and reflected from the target layer forms a spot having a combination of a large semicircle and a small semicircle on the focusing light receiving portion 6A. At this time, stray light also enters the focus light-receiving unit 6A in the same shape as the focus light beam reflected from the target layer.

  FIG. 11 is a front view showing respective spots when the light beam reflected from the target layer and the stray light far from the objective lens 3 than the target layer are irradiated to the hologram 5 and the light receiving unit 6. . As shown in FIG. 11, stray light (both the main beam and the sub beam) is applied only to the region 5 </ b> A of the hologram 5. That is, the stray light is not applied to the regions 5B and 5C that separate the light beams in order to obtain the tracking servo signal. Further, even when the objective lens 3 is moved for tracking control, the stray light is not applied to the regions 5B and 5C.

  Accordingly, the tracking far side stray light 8f is irradiated only to the focus light receiving unit 6A, and the main light receiving unit 6B-0 (6C-0), the sub light receiving units 6B-1, 6B-2 (6C-1, 6C-2). ) And the auxiliary light receiving unit 6B-12 (6C-12) is not irradiated.

  Therefore, by making the regions 5B and 5C for obtaining the tracking servo signal of the hologram 5 into a shape in which the tracking far side stray light 8f does not enter, the offset due to the tracking far side stray light 8fB and the tracking far side stray light 8fC is detected. There is no need to provide the auxiliary light receiving portions 6B-11 and 6C-11. Therefore, the number of auxiliary light receiving units can be reduced and the apparatus can be miniaturized.

  Here, the shape of the auxiliary light receiving unit 6B-12 (6C-12) according to the present embodiment will be described.

  FIG. 12 is a front view showing the shape of the auxiliary light receiving section 6B-12 (6C-12) in the tracking light receiving section 6B (6C).

  In the present embodiment, the auxiliary light receiving unit 6B-12 (6C-12) has sub-light receiving units 6B-1, 6B-2 (6C-1, 6C-2) as shown in FIG. ) Is smaller than. This will be described.

As shown in FIG. 12, the tracking near-side stray light 8nB (8nC) is applied to the sub light receiving unit 6B-2 (6C-2), thereby causing an offset. Similarly, an offset is generated in the main light receiving unit 6B-0 (6C-0). For this reason, the TES is expressed by the following equation (4),
TES = (“6B-0” + Δb− “6C-0” + Δc) −K × {(“6B-1” + “6B-2” + Δb2) − (“6C-1” + “6C-2” + Δc2) } …… (4)
It becomes. The Δb (Δc) indicates an offset generated when the tracking near side stray light 8nB (8nC) is incident on the main light receiving unit 6B-0 (6C-0), and the Δb2 (Δc2) is the tracking near side. The offset generated by the stray light 8nB (8nC) entering the sub light receiving unit 6B-2 (6C-2) is shown.

  Here, if each offset amount by the stray light (tracking near side stray light 8nB (8nC)) is exactly the same, the offset can be canceled without providing an auxiliary light receiving unit. Δb ≠ Δc and Δb2 ≠ Δc2 due to an assembly error of the pickup device 7 and the like.

  Therefore, in the present embodiment, the light receiving area of the auxiliary light receiving unit 6B-12 (6C-12) is made smaller than that of the sub light receiving units 6B-1 and 6B-2 (6C-1 and 6C-2).

In the above equation (4), when the output signals obtained by the auxiliary light receiving unit 6B-12 and the auxiliary light receiving unit 6C-12 are x and y, respectively, the TES is expressed by the following equation (5),
TES = (“6B-0” + Δb− “6C-0” + Δc) −K × {(“6B-1” + “6B-2” + Δb2-x) − (“6C-1” + “6C-2” + Δc2-y)} (5)
It becomes.

  Here, when x and y are determined so that Δb−K × (Δb2−x) = 0 and Δc−K × (Δc2−y) = 0, the main light receiving unit 6B-0 (6C-0) and The offset generated in the sub light receiving units 6B-1 and 6B-2 (6C-1 and 6C-2) can be canceled. In the present embodiment, the light receiving areas (shapes) of the auxiliary light receiving unit 6B-12 and the auxiliary light receiving unit 6B-12 are determined so as to satisfy such x and y. In other words, the light receiving areas of the auxiliary light receiving unit 6B-12 and the auxiliary light receiving unit 6B-12 according to this embodiment are the main light receiving unit 6B-0 (6C-0) and the sub light receiving units 6B-1, 6B-2 ( 6C-1 and 6C-2) are set so as to cancel the offset generated.

  For example, when the light receiving areas of the auxiliary light receiving units 6B-12 and 6B-12 and the sub light receiving units 6B-1, 6B-2 (6C-1, 6C-2) are the same, Δb2 = X, Δc2 = y, so that it is possible to cancel the offset of K × (Δb2-x) and K × (Δc2-y), but the offset of Δb−Δc (Δb ≠ Δc) is It will remain. Therefore, in the present embodiment, in order to cancel the offset generated by the main light receiving unit 6B-0 (6C-0), that is, in order to satisfy Δb2-x> 0 and Δc2-y> 0, auxiliary light reception The light receiving area of the part 6B-12 (6C-12) is smaller than the sub light receiving parts 6B-1, 6B-2 (6C-1, 6C-2).

  By the way, in the present embodiment, the regions 5B and 5C, which are the separation regions of the hologram 5, are regions other than the region where stray light far from the target layer is collected as viewed from the objective lens 3. Accordingly, the tracking near side stray light 8nB (8nC) irradiated to the light receiving unit 6 becomes a quarter circle of a donut-shaped hollow, and therefore the tracking near side incident on the sub light receiving unit 6B-2 (6C-2). The amount of stray light 8nB (8nC) is smaller than the amount of light of the auxiliary light receiving unit 6B-12 (6C-12). Accordingly, when canceling the offset generated by the sub light receiving unit 6B-2 (6C-2), the sub light receiving unit 6B-2 (6C-2) and the auxiliary light receiving unit 6B-12 (6C-12) are irradiated. What is necessary is just to set the light-receiving area of auxiliary light-receiving part 6B-12 (6C-12) so that the light quantity of the stray light performed may become the same. Further, as described above, when the offset generated by the main light receiving unit 6B-0 (6C-0) is also canceled, the light receiving area of the auxiliary light receiving unit 6B-12 (6C-12) is sub-light-receiving. You may set smaller than the light-receiving area which light-receives the stray light irradiated to part 6B-2 (6C-2). More specifically, as shown in FIG. 12, when the lengths of the sub light receiving unit 6B-2 (6C-2) and the auxiliary light receiving units 6B-12 and 6C-12 are the same, the widths of both are set to W1. > W3, W1> W2 may be set (W1: width of sub light receiving unit 6B-2 (6C-2), W3: width of auxiliary light receiving unit 6B-12, W2: auxiliary light receiving unit 6C-12 Width). Thereby, the offset generated in the main light receiving unit 6B-0 (6C-0) and the sub light receiving unit 6B-2 (6C-2) can be canceled with only two auxiliary light receiving units.

  In the present embodiment, the light receiving area of the auxiliary light receiving unit 6C-12 that receives only the tracking near side stray light 8nC separated in the region 5C of the hologram 5 and the tracking near side stray light 8nB separated in the region 5B of the hologram 5 are used. The light receiving areas of the auxiliary light receiving portions 6B-12 that receive only light are different from each other. More specifically, the light receiving area of each of the auxiliary light receiving unit 6C-12 and the auxiliary light receiving unit 6B-12 has an area corresponding to the density of light beams incident on each of the auxiliary light receiving units 6B-12 (light quantity per unit area). . This will be described.

  In the hologram 5, when the light beam and stray light reflected by the target layer are separated and incident on each light receiving unit 6, the divided pattern of the hologram 5 or the position where the divided pattern and each light receiving unit 6 are provided. Depending on the situation, the separated light beams of the region 5B and the region 5C of the hologram 5 have different separation angles and optical path lengths from the hologram 5 to the light receiving unit 6. For example, when light beams separated from the regions 5B and 5C are incident on the light receiving units 6 at different separation angles in the hologram 5, the beam diameters of the light beams irradiated on the light receiving units 6 are used. Is different. Specifically, the larger the separation angle, the larger the beam diameter. In this case, the density of stray light (the amount of light incident per unit area) entering the main light receiving unit 6B-0 and the main light receiving unit 6C-0 is different. Further, the densities of the light beams incident on the sub light receiving units 6B-1 and 6B-2 and the sub light receiving units 6C-1 and 6C-2 are also different. And the density of the said light beam which injects into the auxiliary | assistant light-receiving part 6C-12 and auxiliary | assistant light-receiving part 6B-12 also differs. Accordingly, the light receiving areas of the auxiliary light receiving unit 6C-12 and the auxiliary light receiving unit 6B-12 are set so that the density of stray light irradiated to the auxiliary light receiving unit 6C-12 and the auxiliary light receiving unit 6B-12 is the same. is doing. Specifically, by making the light receiving areas of the auxiliary light receiving unit 6C-12 and the auxiliary light receiving unit 6B-12 different from each other, both of them are irradiated with light beams having different separation angles. Can receive the same density. The light receiving area does not indicate an area where light can be received, but indicates a region actually receiving a light beam.

  In this embodiment, only two auxiliary light receiving units are used to cancel the offset generated in the main light receiving unit 6B-0 (6C-0) and the sub light receiving unit 6B-2 (6C-2). You may provide the gain adjuster which adds a gain to each output signal output from light-receiving part 6C-12 and auxiliary | assistant light-receiving part 6B-12.

  FIG. 13 is a front view showing a configuration in which the tracking light receiving unit 6B (6C) includes a gain adjuster that adds a gain to the output signal from the auxiliary light receiving unit 6B-12 (6C-12).

  The gain adjuster can individually add gains to the output signal output from the auxiliary light receiving unit 6B-12 and the output signal output from the auxiliary light receiving unit 6C-12.

In FIG. 13, when the gain attached to the output signal output from the auxiliary light receiving unit 6B-12 is M and the gain attached to the output signal output from the auxiliary light receiving unit 6C-12 is N, the TES is as follows. Formula (6),
TES = (“6B-0” + Δb− “6C-0” + Δc) −K × {(“6B−1” + “6B-2” + Δb2−x × M) − (“6C-1” + “6C− 2 "+ [Delta] c2-y * N)} (6)
It becomes.

Here, Δb−K × (Δb2−x × M) = 0, Δc−K × (Δc2−y × N) = 0.
By setting the gains M and N so as to be generated, the main light receiving unit 6B-0 (6C-0) and the sub light receiving units 6B-1, 6B-2 (6C-1, 6C-2) are generated. Offset can be canceled.

As described above, when the density of stray light incident on the tracking light receiving parts 6B and 6C is different from each other, the gain adjuster includes the sub light receiving parts 6B-1 and 6B-2 and the sub light receiving parts. A gain different from M and N for the output signal output from 6C-1 and 6C-2 and the output signal from the auxiliary light receiving unit 6B-12 and the output signal from the auxiliary light receiving unit 6C-12. May be added. Specifically, when the gain added to the output signals output from the sub light receiving units 6B-1 and 6B-2 and the sub light receiving units 6C-1 and 6C-2 is I, the TES is expressed by the following equation: (7),
TES = (“6B-0” + Δb− “6C-0” + Δc) −K × [{(“6B−1” + “6B-2” + Δb2) × I−x × M} − {(“6C−1 “+“ 6C-2 ”+ Δc2) × I−y × N}] (7)
It becomes.

In the above formula (7), M> N, I> M, and I> N. Δb−K × (Δb2 × I−x × M) = 0, Δc−K × (Δc2 × I−y × N) = 0
By setting the gains M, N, and I so that the main light receiving unit 6B-0 (6C-0) and the sub light receiving units 6B-1, 6B-2 (6C-1, 6C-2) It is possible to cancel the offset generated in

  As a specific calculation method, as shown in FIG. 13, an output signal (A) obtained by adding a gain M to the output signal from the auxiliary light receiving unit 6B-12 and the sub light receiving units 6B-1 and 6B-2. As a result of differential operation with the output signal (A) from the output signal (A), the output signal (D) obtained by adding a gain N to the output signal from the auxiliary light receiving unit 6C-12 and the sub light receiving unit 6C -1 and 6C-2, the differential output between the result output (c) and the result output (f) A difference is made between the result output (K) with gain K and the result output (K) obtained by performing a differential calculation between the main light receiving units 6B-0 and 6C-0. The TES is obtained by performing the calculation. The TES calculation method (calculation method) is not limited to the above.

  Thus, the offset generated in the main light receiving unit 6B-0 (6C-0) and the sub light receiving unit 6B-2 (6C-2) without changing the light receiving area of the auxiliary light receiving unit 6B-12 (6C-12). Can be canceled.

  As a method for setting each gain as described above, for example, the gain may be determined so that the jitter value and error rate of the reproduction signal are minimized for each optical disk 4 read by the optical pickup device 7. As a simpler optimization method, the best gain may be determined by measuring the offset of the tracking signal, the jitter value of the reproduction signal, and the error rate using the reference multilayer optical disc 4 at the time of assembling the pickup. .

  In the above description, an example in which a gain adjuster for adding a gain to each of output signals output from the auxiliary light receiving unit 6C-12 and the auxiliary light receiving unit 6B-12 has been described. When an auxiliary light receiving unit is provided in addition to the 6C-12 and the auxiliary light receiving unit 6B-12, the gain adjuster may add gains to the output signals from these other auxiliary light receiving units. Good. Further, the gain adjuster may apply gains different from each other to output signals output from the auxiliary light receiving units.

  In the above description, the auxiliary light receiving unit 6C-12 and the auxiliary light receiving unit 6B-12 are described. However, the auxiliary light receiving unit 6B-12 is not limited to the above, and the auxiliary light receiving unit provided in the optical pickup device 7 has the above-described condition. It may be formed so as to satisfy That is, the light receiving areas of the plurality of auxiliary light receiving units provided in the light receiving unit 6 may be different from each other. The light receiving areas of the plurality of auxiliary light receiving units may be smaller than the light receiving areas of the sub light receiving units.

  Further, as shown in FIG. 14, the optical pickup device 7 according to the present embodiment includes an optical pickup unit 20 in which the laser light source 1, the diffraction unit 2, the hologram 5, and the light receiving unit 6 are integrated. And since the laser light source 1, the diffraction part 2, the hologram 5, and the light-receiving part are integrated, the unit can make the optical pick-up apparatus 7 smaller.

  Further, as the hologram 5, for example, a prism or the like may be used.

  Further, the optical pickup device 7 according to the present embodiment may have a configuration in which a gain adjuster that adds a gain to the output signal output from the auxiliary light receiving unit is provided.

In addition, the optical pickup device 7 according to the present embodiment may be configured such that the sizes of the light receiving regions that receive the light beams of the plurality of auxiliary light receiving units are different from each other. Further, the light receiving areas of the plurality of auxiliary light receiving units may be equal to each other.
[Embodiment 3]
Another embodiment of the present invention will be described as follows. For convenience of explanation, members having the same functions as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Here, another division pattern of the hologram 5 will be described. 15 and 16 are front views showing another configuration example of the division pattern of the hologram 5 and a region where the light beam that has passed through the hologram 5 is irradiated to the light receiving unit. 15 shows an example in which the near-side stray light 8n is irradiated to the hologram 5, and FIG. 16 shows an example in which the far-side stray light 8f is irradiated to the hologram 5. In the figure, the dotted spot indicates stray light.

  As shown in FIGS. 15 and 16, the hologram 5 according to the present embodiment is divided into six, and light receiving portions 6 </ b> B to 6 </ b> G corresponding to the six regions of the regions 5 </ b> B to 5 </ b> G are provided. . The four regions 5B, 5C, 5F, 5G and the like have the same shape. On the other hand, the region 5D and the region 5E have a semicircular shape including the optical axis of the main beam, and become a circle when the region 5D and the region 5E are combined. The radius of the semicircle is a region where the light beam reflected from the optical disk 4 in the hologram 5 is separated from the regions 5D and 5E. The stray light far from the target layer as viewed from the objective lens 3 is collected. It is the distance including the area to be. That is, the far side stray light 8f is irradiated to the region 5D and the region 5E.

  The light receiving sections 6B, 6C, 6F, and 6G are, respectively, main beam light receiving sections 6B-0, 6C-0, 6F-0, and 6G-2 that receive zero-order transmitted light, and ± first-order lights. Two corresponding sub-beam light-receiving units 6B-1, 6B-2 to 6G-1, 6G-2, and one auxiliary light-receiving unit 6B-12, 6C-12, 6F-12, 6G- 12 is provided.

  In this embodiment, the focus error signal is obtained from the region 5D, the tracking error signal is obtained from the regions 5B, 5C, 5F, and 5G, and the total signal is obtained from the entire region. And by setting it as said structure, the stray light from the area | regions 5B, 5C, 5F, and 5G isolate | separated in order to produce | generate a tracking error signal by making the area | regions 5D and 5E larger than the beam diameter of the far side stray light 8f. Does not occur. Further, since the irradiation area of the stray light in the light receiving parts 6D and 6E can be made constant by the above configuration, the focusing light reflected by the non-target layer is reflected between the focusing light receiving part and the tracking light receiving area. The beam can be made even closer as long as the beam does not enter the tracking light receiving portions 6B and 6C.

  Here, an information recording / reproducing apparatus including the optical pickup device 7 (optical pickup unit) according to the present embodiment will be described.

  As shown in FIG. 17, the information recording / reproducing apparatus 50 according to the present embodiment includes a spindle motor 51 that rotationally drives the optical disc 4, an optical pickup device 7 that records and reproduces information on the optical disc 4, the spindle motor 51, and the light A drive control unit 52 for driving and controlling the pickup device 7 is provided.

  The drive control unit 52 includes a spindle motor drive circuit that performs drive control of the spindle motor 51, a focus drive circuit that performs drive control of a focus actuator that moves the objective lens 3 in the focus direction, and the objective lens 3 in the radial direction. A control signal generation circuit for generating a control signal for each control circuit from a signal obtained from the optical pickup device 7, and a tracking drive circuit for controlling the driving of the tracking actuator to be moved; An information reproducing circuit for reproducing information recorded on the optical disc 4 from a signal obtained from the apparatus 7 and generating a reproduction signal is provided.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The optical pickup device according to the present invention can be suitably applied particularly to a recordable information recording / reproducing device for recording information on a multilayer optical disk.

It is a front view which shows arrangement | positioning of the light-receiving part for focus concerning this Embodiment, and the light-receiving part for tracking. It is a side view which shows the schematic structure of the optical pick-up apparatus concerning this Embodiment. It is a front view which shows the isolation | separation area | region (separation pattern) of a hologram. It is a front view which shows the detailed structure of a light-receiving part. It is a figure explaining the light beam which injects into a light-receiving part when the main beam and sub beam which were reflected in the hologram by the target layer each enter. It is a side view which shows the difference of the optical path of the light beam reflected from the target layer, and the light beam reflected from the non-target layer closer to the objective lens than the target layer. The front view which shows each spot when the light beam reflected from the target layer and the light beam reflected from the non-target layer closer to the objective lens than the target layer are irradiated to the hologram and the light receiving unit is there. It is a side view which shows the difference of the optical path of the light beam reflected from the target layer, and the light beam reflected from the non-target layer farther to the objective lens than the target layer. The front view which shows each spot when the light beam reflected from the target layer and the light beam reflected from the non-target layer far from the objective lens than the target layer are irradiated to the hologram and the light receiving unit 6 is there. The front view which shows each spot when the light beam reflected from the target layer and the light beam reflected from the non-target layer whose distance from the objective lens is closer than the target layer is irradiated to the hologram and the light receiving unit 6 is there. It is a front view which shows each spot when the light beam reflected from the target layer and the light beam reflected from the non-target layer farther away from the objective lens than the target layer are irradiated to the hologram and the light receiving unit. . It is a front view which shows the shape of the auxiliary light-receiving part in the light-receiving part for tracking. It is a front view which shows the structure provided with the gain adjuster which attaches a gain to the output signal from an auxiliary light-receiving part in the light-receiving part for tracking. It is a front view which shows the schematic structure of an optical pick-up unit. It is a front view which shows the other example of a structure of the division | segmentation pattern of a hologram, and the area | region where the light beam which passed the said hologram is irradiated to a light-receiving part. It is a front view which shows the other example of a structure of the division | segmentation pattern of a hologram, and the area | region where the light beam which passed the said hologram is irradiated to a light-receiving part. It is a block diagram which shows the schematic structure of an information recording / reproducing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Diffraction part 3 Objective lens 4 Optical disk 5 Hologram 6 Light receiving part 20 Optical pick-up unit 50 Information recording / reproducing apparatus 51 Spindle motor 52 Drive control part

Claims (9)

A main beam reflected from a recording medium on which a plurality of information recording layers are laminated and passed through a condensing means, at least a focus main beam for obtaining a focus servo signal and a tracking main beam for obtaining a tracking servo signal And separated into
Separating means for separating a sub beam reflected from the recording medium and having a light intensity smaller than that of the main beam passed through the light collecting means into at least a tracking sub beam for obtaining a tracking servo signal;
An optical pickup unit comprising a tracking light receiving means for receiving the tracking main beam and the tracking sub beam,
The tracking light receiving means has a sub light receiving portion for receiving the tracking sub beam,
Tracking light receiving means is arranged so that the main beam for focus reflected by the information recording layer other than the information recording layer performing information recording / reproducing is not incident on the sub light receiving unit,
Only the tracking main beam reflected by the information recording layer other than the information recording layer that is recording / reproducing the information and / or the tracking sub-beam reflected by the information recording layer other than the information recording layer is received. It has an auxiliary light receiving part ,
Optical pick-up unit, characterized in cancellation to Rukoto the offset of the tracking error signal based on the output from the auxiliary light receiving portion. The separating means separates the sub beam into a tracking sub beam for obtaining a tracking servo signal and a sub beam other than the tracking sub beam.
Tracking light-receiving means is arranged so that the main beam for focusing and the other sub-beams reflected by the information recording layer other than the information recording layer for recording / reproducing the information do not enter the sub-light receiving unit. The optical pickup unit according to claim 1, wherein: The tracking light receiving means further includes a main light receiving portion for receiving the tracking main beam,
3. The optical pickup unit according to claim 2, wherein a light receiving area of the auxiliary light receiving unit is smaller than a light receiving area of the sub light receiving unit.   The tracking light receiving means is disposed so that the focusing main beam and the other sub-beams reflected by the information recording layer other than the information recording layer for recording / reproducing the information do not enter the auxiliary light receiving unit. The optical pickup unit according to claim 2, wherein the optical pickup unit is provided.   The separation means is an area excluding an area where the main beam and the sub beam reflected by the information recording layer farther than the information recording layer on which information is recorded / reproduced as viewed from the light collecting means are collected. 2. The optical pickup unit according to claim 1, wherein the main beam for tracking and the sub beam for tracking are separated.   2. The optical pickup unit according to claim 1, wherein the separating means is a hologram.   The separating means, the light receiving means, a light source for irradiating the recording medium with a light beam, and a generating means for generating a main beam and a sub beam from the light beam emitted from the light source are integrated. 2. The optical pickup unit according to claim 1, wherein   An optical pickup device comprising the optical pickup unit according to claim 1.   An information recording / reproducing apparatus comprising the optical pickup unit according to any one of claims 1 to 7.

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