JP2011065698A - Optical pickup device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device for obtaining stable servo signals, such as focus error signals and tracking error signals, by preventing an influence of stray light from other layers during recording/reproduction of a multilayer optical disk. <P>SOLUTION: A reflected light from the multilayer optical disk is divided into a plurality of areas, divided light beams are focused on different positions of a photodetector, a focus error signal is detected by a spot size detection method using some of the divided light beams, and a tracking error signal is detected by using some of the divided light beams. The light beam division areas and a light-receiving part for the servo signal of the photodetector are so arranged as to prevent the stray light from other layers from entering the light-receiving part when a focus is on a target layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an optical pickup device and an optical disc device.

  As background art in this technical field, for example, there is JP-A-2006-344344 (Patent Document 1). This publication describes that “a desired signal is accurately obtained from an optical disk having a plurality of recording layers” as a problem. As a solving means, “the P-polarized light beam emitted from the light source unit 51 is reflected by the optical disk 15. Then, it becomes S-polarized light and enters the lens 61. Then, in the quarter-wave plates 62 and 63, an optical phase difference of +1/4 wavelength of the light beam incident on the + X side of the optical axis is given. An optical phase difference of -1/4 wavelength is given to the light beam incident on the X side, so that the signal light passing through the quarter wavelength plate 63 becomes S-polarized light and the stray light becomes P-polarized light. Only light is transmitted. "

  Further, for example, Non-Patent Document 1 has a problem “When recording / reproducing a dual-layer disc, an offset occurs in the TE signal when other layer stray light having light reflected from a layer different from the target layer is incident on the photodetector. For this reason, in the conventional configuration without countermeasures for stray light from other layers, the TE signal offset in a two-layer disc is larger than that in a single layer, and stable control is prevented. ” The tracking photodetector is arranged in an area where no other layer stray light is present.

  The configuration is also described in JP-A No. 2004-281026 (Patent Document 2).

JP 2006-344344 A (page 26, FIG. 3, FIG. 5) JP 2004-281026 A (page 71, FIG. 22, FIG. 24, FIG. 25)

IEICE Technical Report CPM 2005-149 (2005-10) (Page 33, FIG. 4, FIG. 5)

In general, an optical pickup device irradiates a spot correctly on a predetermined recording track in an optical disc, so that the objective lens is displaced in the focus direction by detection of the focus error signal, and the tracking error signal is adjusted. Is detected, and the objective lens is displaced in the radial direction of the disk-shaped recording medium to perform tracking adjustment. The position of the objective lens is controlled by these signals.
Among the servo signals, the tracking error signal has a big problem because it is a two-layer disc having two recording layers. In the two-layer disc, stray light reflected from a non-target recording layer is incident on the same light receiving surface in addition to the signal light reflected from the target recording layer. When signal light and stray light are incident on the light receiving surface, the two lights interfere with each other and the fluctuation component is detected in the tracking error signal.

  With respect to this problem, in Patent Document 1, a light beam reflected by an optical disk is stopped by a condensing lens, and light spread through two quarter-wave plates and a polarizing optical element is detected by a condensing lens. It is set as the structure which irradiates to. Therefore, there is a problem that the detection optical system becomes complicated and the size becomes large.

  In Non-Patent Document 1 (Patent Document 2), a tracking photodetector is arranged outside stray light from the other layer of the focusing light beam generated around the focusing photodetector, and further diffracted at the center of the hologram element. Therefore, the size of the pickup device and the cost are increased due to the increase in the size of the photodetector.

  The present invention provides an optical pickup device that can obtain a stable servo signal and can be reduced in size when an information recording medium having a plurality of information recording surfaces is recorded / reproduced, and an optical disk device equipped with the optical pickup device. With the goal.

  The above object can be achieved, for example, by the invention described in the claims.

  According to the present invention, there is provided an optical pickup device capable of obtaining a stable servo signal and capable of being miniaturized and an optical disk device equipped with the same when recording / reproducing an information recording medium having a plurality of information recording surfaces. be able to.

1 is a diagram illustrating an optical system of the present invention in Example 1. FIG. 1 is a diagram showing a diffraction grating of the present invention in Example 1. FIG. It is a figure which shows the light-receiving part of this invention in Example 1. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 1. FIG. It is a figure explaining the behavior of the stray light from the other layer of a two-layer disc. It is a figure explaining the behavior of the stray light from the other layer of a two-layer disc. 6 is a diagram showing another diffraction grating of the present invention in Example 1. FIG. It is a figure which shows the other light-receiving part of this invention in Example 1. FIG. 6 is a diagram illustrating a light receiving unit according to the present invention in Example 2. FIG. It is a figure which shows the shape (on a diffraction grating) of the stray light at the time of recording / reproducing the double layer disk in Example 2. FIG. 6 is a view showing a light receiving portion of the present invention in Example 3. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 3. FIG. It is a figure which shows the light-receiving part of this invention in Example 4. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 4. FIG. It is a figure which shows the light-receiving part of this invention in Example 5. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 5. FIG. It is a figure which shows the light-receiving part of this invention in Example 6. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 6. FIG. It is a figure which shows the light-receiving part of this invention in Example 7. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 7. FIG. It is a figure which shows the light-receiving part of this invention in Example 8. FIG. It is a figure which shows the shape (on a detector) of the stray light at the time of recording / reproducing the double layer disk in Example 8. FIG. FIG. 10 is a diagram illustrating an optical reproducing device according to a ninth embodiment. It is a figure explaining the optical recording / reproducing apparatus in Example 10. FIG.

  FIG. 1 shows an optical system of an optical pickup device according to a first embodiment of the present invention. Here, BD will be described, but it may be a DVD or another recording method. In the following description, the optical disc layer includes a recording layer in a recordable optical disc and a reproduction layer of a read-only optical disc.

  From the semiconductor laser 50, a light beam having a wavelength of about 405 nm is emitted as diverging light. The light beam emitted from the semiconductor laser 50 reflects the beam splitter 52. A part of the light beam passes through the beam splitter 52 and enters the front monitor 53. In general, when information is recorded on a recording type optical disc such as a BD-RE or BD-R, the information recording surface (recording layer) of the optical disc is irradiated with a predetermined amount of light. Need to control. Therefore, the front monitor 53 detects a change in the light amount of the semiconductor laser 50 when recording a signal on the recordable optical disk, and feeds it back to a drive circuit (not shown) of the semiconductor laser 50. As a result, the amount of light on the optical disk can be monitored.

  The light beam reflected from the beam splitter 52 is converted into a substantially parallel light beam by the collimating lens 51. The light beam that has passed through the collimating lens 51 enters the beam expander 54. The beam expander 54 is used to compensate for spherical aberration due to the thickness error of the cover layer of the optical disc 100 by changing the divergence / convergence state of the light beam. The light beam emitted from the beam expander 54 is reflected by the rising mirror 55, transmitted through the quarter wavelength plate 56, and then condensed on the optical disk 100 by the objective lens 2 mounted on the actuator 5.

  The light beam reflected from the optical disc 100 enters the diffraction grating 11 through the objective lens 2, the quarter-wave plate 56, the rising mirror 55, the beam expander 54, the collimator lens 51, and the beam splitter 52. The light beam is divided into a plurality of regions by the diffraction grating 11, travels in different directions for each region, and focuses on the photodetector 10. A plurality of light receiving portions are formed on the photodetector 10, and each light receiving portion is irradiated with the light beam divided by the diffraction grating 11. An electrical signal is output from the photodetector 10 in accordance with the amount of light applied to the light receiving unit, and these outputs are calculated to generate an RF signal, a focus error signal, and a tracking error signal that are reproduction signals.

  Here, the tracking error signal detection will be described first. A differential push-pull method is known as a general tracking error signal detection method. In this differential push-pull method (DPP: Differential Push Pull method), a light beam is divided by a diffraction grating into a main beam, a sub beam + 1st order, a sub beam-1st order, and a push pull (MPP) obtained from a radial main beam. The DC offset is reduced by performing the following operation on the push-pull (SPP) signal obtained from the signal, sub-beam + 1st order, and subbeam-1st order.

なお、ｋはメインビームとサブビームの光量比を補正する係数である。
ところが、ＤＰＰ方式は２層およびそれ以上の記録層を有するディスクの記録／再生において問題が発生する。これについて最も簡単な２層ディスクで説明を行う。

Note that k is a coefficient for correcting the light amount ratio between the main beam and the sub beam.
However, the DPP method has a problem in recording / reproduction of a disc having two and more recording layers. This will be described with the simplest two-layer disc.

  A two-layer disc is an optical disc having two recording surfaces, and reflected light is generated on each recording surface. For this reason, in a two-layer disc, the light beam is separated into two by the optical disc and enters the detector along two optical paths. For example, when focusing on one layer, the light beam forms a spot (signal light) on the detector surface, and the light beam reflected from the other layer (stray light) is blurred on the detector. Incident. At this time, on the detector, the signal light reflected from each layer and the stray light overlap on the detector surface, and interference occurs. Originally, a beam emitted from a laser having the same frequency does not change with time, but since the interval between the layers changes with the rotation of the optical disk, the phase relationship between the two lights changes with time, which is a tracking error signal. Causes fluctuations in the DPP signal. The fluctuation of the DPP signal is mainly caused by the SPP signal. This is because the light amount ratio of the main beam (0th order diffracted light), sub beam + 1st order diffracted light and sub beam-1st order diffracted light is generally 10: 1: 1 to 20: 1: 1, and the light amount of the sub beam with respect to the main beam. Therefore, the interference between the sub-beam signal light and the stray light of the main beam is greatly generated with respect to the signal light. As a result, the SPP signal greatly fluctuates, and as a result, the DPP signal that is a tracking error signal fluctuates greatly. When the tracking error signal fluctuates, the spot on the optical disc cannot follow along the track, which mainly causes a problem of deterioration of the recording / reproducing signal.

  To deal with this problem, Non-Patent Document 1 (Patent Document 2) forms a single spot on an optical disk and separates the reflected light into a plurality of areas to detect signal light and stray light separately. As a result, no stray light is incident on the light receiving portion that detects the tracking error signal, and thus a stable tracking error signal can be detected. However, a tracking photodetector is arranged outside the stray light from the other layer of the focusing light beam generated around the focusing photodetector, and the light diffracted at the center of the hologram element is further reflected by the stray light from the other layer. Since it is configured to fly outward, the size of the pickup device and the cost are increased as the size of the photodetector increases. Further, the configuration for detecting the signal light outside the stray light is further disadvantageous for the multilayer disk.

  On the other hand, in this embodiment, since the signal light is detected inside the stray light, it is possible to deal with not only two layers but also a multi-layer disc. Further, it can be made smaller than the detector of Non-Patent Document 1 (Patent Document 2).

  FIG. 2 shows the shape of the diffraction grating 11 of this embodiment. The solid line indicates the boundary line of the region, the two-dot chain line indicates the outer shape of the light beam of the laser beam, and the hatched portion indicates the interference region (push-pull pattern) between the zeroth-order diffracted light and the ± first-order diffracted light diffracted by the track Is shown. The diffraction grating 11 receives regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order light of the diffracted light enter. Regions Da, Db, Dc, Dd (region B) and regions Di1, Di2 (region C) are formed. Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, and Dh of the diffraction grating 11 are the light receiving portions a, b, c, d, e, and f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 4 shows the stray light from the other layers at the time of recording / reproducing the double-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  In actual signal detection, since the objective lens performs recording / reproduction while following the track on the disk, the objective lens is displaced in the Rad direction. When the objective lens is displaced, only the stray light component is displaced on the photodetector. For this reason, if the objective lens is displaced in the case of a light receiving portion pattern of a normal photodetector, stray light from another layer may enter the light receiving portion. On the other hand, in the present embodiment, by optimizing the photodetector 10 with respect to the pattern of the diffraction grating 11, it becomes possible to increase the allowable displacement of the objective lens. What should be considered here is how to separate the signal light and stray light in the lens displacement direction. This will be described below.

  FIG. 5 shows a light beam diffracted by the diffraction grating region Dh and incident on the light receiving portion h. FIG. 6 shows a light beam diffracted by the diffraction grating region Dd and incident on the light receiving part d. (A), (b), and (c) are classified according to the state of the light spot on the disc, (b) is in a state of focusing on the disc, and (a) and (c) are the objective lenses. It shows a defocused state. Note that (a) and (c) differ in the direction in which the objective lens is defocused. The relationship between (a), (b), and (c) hardly depends on the position of the light receiving unit. Here, the defocusing will be described because the stray light of the two-layer disc can be interpreted as defocused light reflected at a place other than the focal position.

  Comparing FIG. 5 and FIG. 6, it can be seen that the moving direction of the light beam differs depending on the defocus. The light beam diffracted by Dh in FIG. 5 moves in the disc track direction (hereinafter referred to as Tan direction) by defocusing. In contrast, the light beam diffracted by Dd in FIG. 6 moves in the Rad direction. This is blurred in point symmetry with respect to the light beam center 15 on the diffraction grating, and therefore the moving direction by defocusing is different. For this reason, it is important to divide how to avoid stray light according to the region. When the region of the diffraction grating is separated from the light beam center 15 in the Tan direction (Dh, De, Df, Dg (region A)), it is desirable to avoid stray light in the Tan direction. By avoiding stray light in this way, even if the objective lens is displaced in the Rad direction, it does not enter the detector. For this reason, it is possible to minimize the influence of stray light diffracting other regions by arranging the light receiving units that detect the light beams diffracted in the diffraction grating regions Dh, De, Df, and Dg in the Rad direction. Become.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it becomes possible to minimize the influence of stray light by arranging the light receiving parts for detecting the light beams diffracted in the areas Da, Db, Dc, and Dd in the Tan direction.

  Further, the light detectors s1 and s2 that detect the light beam diffracted by the diffraction grating Di1 and the light receivers s3 and s4 that detect the light beam diffracted by the diffraction grating Di2 are reduced in size, and the other layers are efficiently formed. Can be separated from the tracking error signal detector.

  As described above, the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 3, so that a stable tracking error signal can be detected. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device in this embodiment is configured to separate stray light to the outside, the same applies to an optical disc having two or more recording layers or reproducing layers. Needless to say, an effect can be obtained. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 3, and it goes without saying that the same effect can be obtained even when the light receiving surface is not in contact as shown in FIG. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even if only the structures of the light receiving surfaces a, b, c, and d are used. Similarly, it goes without saying that the same effect can be obtained with only the configuration of the light receiving surfaces e, f, g, and h.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 3, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 9 shows an optical detector of the optical system of the optical pickup device according to the second embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, Dh of the diffraction grating 11 are the light receiving portions a, b, c, d, e, f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 10 shows the stray light from the other layers at the time of recording / reproducing the two-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable. Therefore, stray light does not enter the light receiving surface even when the objective lens is displaced in the Rad direction by avoiding stray light in the Tan direction as in the light receiving surfaces e, f, g, and h in FIG.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it is possible to minimize the influence of stray light by avoiding stray light in the Rad direction like the light receiving surfaces a, b, c, and d in FIG.

  As described above, the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 9, and can detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 9, and it goes without saying that the same effect can be obtained even if the light receiving surfaces are not in contact with each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even if only the structures of the light receiving surfaces a, b, c, and d are used. Similarly, it goes without saying that the same effect can be obtained with only the configuration of the light receiving surfaces e, f, g, and h.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 9, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 11 shows a photodetector of the optical system of the optical pickup device according to the third embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, Dh of the diffraction grating 11 are the light receiving parts a, b, c, d, e, f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 12 shows the stray light from the other layers at the time of recording / reproducing the double-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable. For this reason, stray light does not enter the light receiving surface even when the objective lens is displaced in the Rad direction by avoiding stray light in the Tan direction as in the light receiving surfaces e, f, g, and h in FIG.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it is possible to minimize the influence of stray light by avoiding stray light in the Rad direction like the light receiving surfaces a, b, c, and d in FIG.

  As described above, the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 11, and thus can detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 11, and it goes without saying that the same effect can be obtained even if the light receiving surfaces are not in contact with each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even if only the structures of the light receiving surfaces a, b, c, and d are used. Similarly, it goes without saying that the same effect can be obtained even if only the configuration of the light receiving surfaces e and h or only the configuration of the light receiving surfaces f and g.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 11, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 13 shows an optical detector of the optical system of the optical pickup device according to the fourth embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, Dh of the diffraction grating 11 are the light receiving portions a, b, c, d, e, f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 14 shows the stray light from the other layers at the time of recording / reproducing the double-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable. Therefore, stray light does not enter the light receiving surface even when the objective lens is displaced in the Rad direction by avoiding stray light in the Tan direction like the light receiving surfaces e, f, g, and h in FIG.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it is possible to minimize the influence of stray light by avoiding stray light in the Rad direction like the light receiving surfaces a, b, c, and d in FIG.

  As described above, the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 13, so that it is possible to detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 13, and it goes without saying that the same effect can be obtained even when the light receiving surfaces are not in contact with each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even when only the light receiving surfaces a and b are configured and only the light receiving surfaces c and d are configured. Similarly, it goes without saying that the same effect can be obtained even if only the light receiving surfaces e, h, f, and g are configured.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 13, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 15 shows an optical detector of the optical system of the optical pickup device according to the fifth embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, Dh of the diffraction grating 11 are the light receiving portions a, b, c, d, e, f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 16 shows the stray light from the other layers at the time of recording / reproducing the double-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable. However, as long as the stray light is separated in the Tan direction while the objective lens is not displaced, the stray light does not enter the light receiving surface even when the objective lens is displaced. There is no problem even if the light receiving surfaces g and e are arranged in the Tan direction.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. Therefore, it is possible to minimize the influence of stray light by avoiding stray light in the Rad direction like the light receiving surfaces a, b, c, and d in FIG.

  As described above, since the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 15, it is possible to detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 15. For example, it is needless to say that the same effect can be obtained even if the light receiving surfaces g, h, e, and f are not in contact with each other. Furthermore, the light receiving surfaces a, b, c, and d arranged in the Tan direction do not need to be in contact with each other, and it goes without saying that the same effect can be obtained even if they are separated from each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even if only the light receiving surfaces a and c are configured and only the light receiving surfaces b and d are configured. Similarly, it goes without saying that the same effect can be obtained even if only the structure of the light receiving surfaces e, h, f, and g is used.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 15, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 17 shows a photodetector of the optical system of the optical pickup device according to the sixth embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, Dh of the diffraction grating 11 are the light receiving portions a, b, c, d, e, f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 18 shows the stray light from the other layers at the time of recording / reproducing the double-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable. However, as long as the stray light is separated in the Tan direction while the objective lens is not displaced, the stray light does not enter the light receiving surface even when the objective lens is displaced. There is no problem even if the light receiving surfaces g and e are arranged in the Tan direction.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it is possible to minimize the influence of stray light by avoiding stray light in the Rad direction like the light receiving surfaces a, b, c, and d in FIG.

  As described above, the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 17, so that it is possible to detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 17, and it goes without saying that the same effect can be obtained even if the light receiving surfaces g, h, e, and f are not in contact with each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even if only the configuration of the light receiving surfaces a, b, c, and d is used. Similarly, it goes without saying that the same effect can be obtained even if only the configuration of the light receiving surfaces e and h and only the configuration of the light receiving surfaces f and g.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 17, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 19 shows an optical detector of the optical system of the optical pickup device according to the seventh embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 0, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, and Dh of the diffraction grating 11 are the light receiving portions a, b, c, d, e, and f of the photodetector shown in FIG. , G, h. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A, B, C, D, E, F, G, H, S1, S2, S3 obtained from the light receiving parts a, b, c, d, e, f, g, h, s1, s2, s3, s4 , The focus error signal, tracking error signal, and RF signal are generated from the signal of S4 by the following calculation.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 20 shows the stray light from the other layers at the time of recording / reproducing the two-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable. However, as long as the stray light is separated in the Tan direction while the objective lens is not displaced, the stray light does not enter the light receiving surface even when the objective lens is displaced. There is no problem even if the light receiving surfaces g and e are arranged in the Tan direction.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it is possible to minimize the influence of stray light by avoiding stray light in the Rad direction like the light receiving surfaces a, b, c, and d in FIG.

  As described above, since the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 19, it is possible to detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 19. For example, it goes without saying that the same effect can be obtained even if the light receiving surfaces g, h, e, and f are not in contact with each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even with only the configuration of the light receiving surfaces a and b and the configuration of only the light receiving surfaces c and d. Similarly, it goes without saying that the same effect can be obtained even if only the light receiving surfaces e, f, g, and h are configured.

  Further, the focus error signal light-receiving portion is not limited to the position shown in FIG. 19, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  FIG. 21 shows an optical detector of the optical system of the optical pickup apparatus according to the eighth embodiment of the present invention. The difference from the first embodiment is that the diffraction grating 11 and the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  The diffraction grating 11 shown in FIG. 2 includes regions De, Df, Dg, and Dh (region A) where only the 0th-order diffracted light diffracted from the track on the disk is incident, and the 0th-order diffracted light and ± 1st-order diffracted light. It is formed by areas Da, Db, Dc, Dd (area B) where light enters and areas Di1, Di2 (area C). Here, the regions Di1 and Di2 of the diffraction grating 11 are hologram surfaces. The hologram surfaces of the regions Di1 and Di2 are regions where predetermined defocus aberration occurs, and the wavefront of the + 1st order light diffracted in the regions Di1 and Di2 is advanced, and the wavefront of the −1st order light is delayed.

  For example, the spectral ratio of the diffraction grating 11 other than the regions Di1 and Di2 is set to 0th order light: + 1st order light: -1st order light = 0: 1: 1, and the spectral ratio of the region Di1 is set to 0th order light: + 1st order light: −1st order light = 0: 1: 0, and the spectral ratio of the region Di2 is 0th order light: + 1st order light: −1st order light = 0: 0: 1. With such a configuration, the photodetector 10 has a pattern as shown in FIG.

  The + 1st order lights diffracted by the areas Da, Db, Dc, Dd, De, Df, Dg, and Dh of the diffraction grating 11 are the light receiving portions a1, b1, c1, d1, e1, and f1 of the photodetector shown in FIG. , G1, and h1, and the −1st order light is incident on a2, b2, c2, d2, e2, f2, g2, and h2, respectively. Further, the + first order light diffracted in the region Di1 is incident on the light receiving portions s1 and s2, and the −1st order light diffracted in the region Di2 is incident on the light receiving portions s3 and s4.

  A1, B1, C1 obtained from the light receiving parts a1, b1, c1, d1, e1, f1, g1, h1, a2, b2, c2, d2, e2, f2, g2, h2, s1, s2, s3, s4 , D1, E1, F1, G1, H1, A2, B2, C2, D2, E2, F2, G2, H2, S1, S2, S3, S4 are converted into a focus error signal, tracking error signal, RF by the following calculation: Generate a signal.

なお、ｋｔは対物レンズが変位した際にトラッキング誤差信号にＤＣ成分を発生させないようにする係数である。ここで、フォーカス誤差検出方式はスポットサイズ検出方式である。

Note that kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced. Here, the focus error detection method is a spot size detection method.

  FIG. 22 shows the stray light from the other layers at the time of recording / reproducing the double-layer disc. (A) shows the time of L0 recording / playback, and (b) shows the time of L1 recording / playback. It can be seen that stray light from other layers is not incident on the light receiving part other than the light beam diffracted in the regions Di1 and Di2 of the diffraction grating 11. However, since the signals S1, S2, S3, and S4 detected from the light receiving portions s1, s2, s3, and s4 are not used for detecting the tracking error signal but are used for the focus error signal and the reproduction signal, there is stray light. Is not a practical problem.

  As described in the first embodiment, stray light is avoided in the Tan direction when the diffraction grating region is separated in the Tan direction with respect to the light beam center 15 (Dh, De, Df, Dg (region A)). It is desirable.

  Further, when the diffraction grating region is separated from the light beam center 15 in the Rad direction (Da, Db, Dc, Dd (region B)), it is desirable to avoid stray light in the Rad direction. For this reason, it becomes possible to minimize the influence of stray light by arranging the light receiving parts for detecting the light beams diffracted in the areas Da, Db, Dc, and Dd in the Tan direction.

  As described above, the photodetector 10 can effectively separate the signal light and the stray light as shown in FIG. 21, so that it is possible to detect a stable tracking error signal. Further, unlike the non-patent document 1 (patent document 2), the optical pickup device in the present embodiment has a feature that it is easy to miniaturize because it has a configuration that separates stray light to the outside. Needless to say, the same effect can be obtained even if the diffraction grating 11 has a pattern as shown in FIGS. Furthermore, in the present embodiment, the diffraction grating 11 is disposed after passing through the beam splitter, but it goes without saying that the same effect can be obtained even if the diffraction grating 11 is a polarization diffraction grating and disposed before passing through the beam splitter. Although the description has been given here with two layers, since the optical pickup device according to the present embodiment is configured to separate stray light to the outside, the same effect can be obtained even with an optical disk having two or more layers. Needless to say. Needless to say, the spherical aberration correction method is not limited. Further, the light receiving surface is not limited to that shown in FIG. 21. For example, the same effect can be obtained even if the light receiving surfaces e, f, g, and h are not in contact with each other. Further, stray light in a region in the Rad direction with respect to the center of the diffraction grating is separated in the Rad direction, and stray light in a region in the Tan direction with respect to the center of the diffraction grating is separated in the Tan direction. Similar effects can be obtained. For this reason, for example, it goes without saying that the same effect can be obtained even with only the configuration of the light receiving surfaces a and c and the configuration of only the light receiving surfaces b and d. Similarly, it goes without saying that the same effect can be obtained even if only the light receiving surfaces e, f, g, and h are configured.

  Further, the light receiving portion for the focus error signal is not limited to the position shown in FIG. 21, and it goes without saying that the same effect can be obtained wherever it is placed. Needless to say, the same effect can be obtained by setting Di1 and Di2 in the same region and using the spot size detection method. Furthermore, it goes without saying that the focus error signal detection method is not limited to the spot size detection method. In the present embodiment, the focus error signal is detected from the area C, but it goes without saying that the same effect can be obtained by detecting the focus error signal in another area.

  In Example 9, an optical reproducing apparatus equipped with an optical pickup device will be described. FIG. 23 shows a schematic configuration of the optical reproducing apparatus. The optical pickup device is provided with a mechanism that can be driven along the Rad direction of the optical disc 100, and the position is controlled in accordance with an access control signal from the access control circuit 172.

  A predetermined laser driving current is supplied from the laser lighting circuit 177 to the semiconductor laser in the optical pickup device, and laser light is emitted from the semiconductor laser with a predetermined light amount according to reproduction. The laser lighting circuit 177 can be incorporated in the optical pickup device.

  The signal output from the photodetector 10 in the optical pickup device is sent to the servo signal generation circuit 174 and the information signal reproduction circuit 175. The servo signal generation circuit 174 generates a servo signal such as a focus error signal, a tracking error signal, and a tilt control signal based on the signal from the light detector 10, and based on this generates a servo signal such as a focus error signal, a tracking error signal, and a tilt control signal. The position of the objective lens is controlled by driving the actuator.

The information signal reproduction circuit 175 reproduces the information signal recorded on the optical disc 100 based on the signal from the photodetector 10.
Some of the signals obtained by the servo signal generation circuit 174 and the information signal reproduction circuit 175 are sent to the control circuit 176. The control circuit 176 is connected to a spindle motor drive circuit 171, an access control circuit 172, a servo signal generation circuit 174, a laser lighting circuit 177, a spherical aberration correction element drive circuit 179, and the like, and the rotation of the spindle motor 180 that rotates the optical disc 100. Control, access direction and access position control, servo control of the objective lens, control of the amount of light emitted from the semiconductor laser in the optical pickup device, correction of spherical aberration due to the difference in disk substrate thickness, and the like are performed.

  In Example 10, an optical recording / reproducing apparatus equipped with an optical pickup device will be described. FIG. 24 is a schematic configuration of an optical recording / reproducing apparatus. This apparatus is different from the optical information recording / reproducing apparatus shown in FIG. 23 in that an information signal recording circuit 178 is provided between the control circuit 176 and the laser lighting circuit 177, and a recording control signal from the information signal recording circuit 178 is provided. Based on the above, the lighting control of the laser lighting circuit 177 is performed, and a function of writing desired information to the optical disc 100 is added.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

2: objective lens, 5: actuator, 10: photodetector, 11: diffraction grating, 50: semiconductor laser, 51: collimating lens, 52: beam splitter, 53: front monitor, 54: beam expander, 55: start-up Mirror: 56: 1/4 wavelength plate, 171: Spindle motor drive circuit, 172: Access control circuit, 173: Actuator drive circuit, 174: Servo signal generation circuit, 175: Information signal reproduction circuit, 176: Control circuit, 177: Laser lighting circuit, 178: information recording circuit, 179: spherical aberration correction element driving circuit, 180: spindle motor, Da to Dh: diffraction grating area, Di1 to Di4: diffraction grating area, ah: on photodetector Light receiving part, a1 to h1: Light receiving part on photodetector, a2 to h2: Light receiving part on photodetector, s1, s2, s3 s4: light detector on the light-receiving part

Claims (9)

An optical pickup device,
A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching a light beam reflected from the optical disc;
A photodetector having a plurality of light receiving portions for receiving the light beam branched by the diffraction grating,
The diffraction grating has three regions, region A, region B, and region C;
Of the disc diffracted light diffracted by the track on the optical disc,
In the area A, 0th-order disc diffracted light is incident,
In the region B, 0th order and ± 1st order disc diffracted light is incident,
In the region C, the central light flux of the 0th-order disc diffracted light is incident,
In the photodetector, a reproduction signal is detected from grating diffracted light diffracted in the regions A, B, and C, and
An optical pickup device characterized in that at least two light receiving portions for detecting + 1st order diffracted light or −1st order diffracted light in the diffraction grating region A are arranged in a substantially straight line in a direction corresponding to a radial direction of the optical disc. An optical pickup device,
A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching a light beam reflected from the optical disc;
A photodetector having a plurality of light receiving portions for receiving the light beam branched by the diffraction grating,
The diffraction grating has three regions, region A, region B, and region C;
Of the disc diffracted light diffracted by the track on the optical disc,
In the area A, 0th-order disc diffracted light is incident,
In the region B, 0th order and ± 1st order disc diffracted light is incident,
In the region C, the central light flux of the 0th-order disc diffracted light is incident,
In the photodetector, a reproduction signal is detected from grating diffracted light diffracted in the regions A, B, and C, and
An optical pickup device, wherein at least two light receiving portions for detecting + 1st order grating diffracted light or −1st order grating diffracted light in the diffraction grating region B are arranged in a substantially straight line in a direction corresponding to a tangential direction of the optical disc. An optical pickup device,
A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching a light beam reflected from the optical disc;
A photodetector having a plurality of light receiving portions for receiving the light beam branched by the diffraction grating,
The diffraction grating has three regions, region A, region B, and region C;
Of the disc diffracted light diffracted by the track on the optical disc,
In the area A, 0th-order disc diffracted light is incident,
In the region B, 0th order and ± 1st order disc diffracted light is incident,
In the region C, the central light flux of the 0th-order disc diffracted light is incident,
In the photodetector, a reproduction signal is detected from grating diffracted light diffracted in the regions A, B, and C, and
When recording or reproducing an optical disc having a plurality of layers, a signal beam reflected from a predetermined layer of the plurality of layers of the optical disc and diffracted by the region A of the diffraction grating is at least one of the detectors. The non-signal light beam that is focused on the light receiving portion, reflected by a layer other than the predetermined layer, and diffracted by the region A of the diffraction grating is a direction corresponding to the tangential direction of the optical disc with respect to the light receiving portion of the detector An optical pickup device, wherein the diffraction grating is configured to irradiate a laser beam. An optical pickup device,
A semiconductor laser that emits laser light;
An objective lens for irradiating an optical disk with a light beam emitted from the semiconductor laser;
A diffraction grating for branching the light beam reflected from the optical disc;
A photodetector having a plurality of light receiving portions for receiving the light beam branched by the diffraction grating,
The diffraction grating has three regions, region A, region B, and region C;
Of the disc diffracted light diffracted by the track on the optical disc,
In the area A, 0th-order disc diffracted light is incident,
In the region B, 0th order and ± 1st order disc diffracted light is incident,
In the region C, the central light flux of the 0th-order disc diffracted light is incident,
In the photodetector, a reproduction signal is detected from grating diffracted light diffracted in the regions A, B, and C, and
When recording or reproducing an optical disc having a plurality of layers, a signal beam reflected from a predetermined layer and diffracted by the diffraction grating region B of the optical disc is condensed on at least one light receiving portion of the detector. The non-signal light beam reflected by the layers other than the predetermined layer and diffracted by the diffraction grating region B is irradiated to the light receiving portion of the detector in a direction corresponding to the radial direction of the optical disc. An optical pickup device comprising the diffraction grating. An optical pickup device according to any one of claims 1 to 4,
A focus error signal is detected by the diffracted light in the region C of the diffraction grating;
A tracking error signal is detected by the diffracted light diffracted in the regions A and B of the diffraction grating,
An optical pickup device that detects a reproduction signal using diffracted light of the regions A, B, and C. An optical pickup device according to any one of claims 1 to 5,
An optical pickup device, wherein a focus error signal is detected by a spot size detection method. An optical pickup device according to any one of claims 1 to 6,
The photodetector has a plurality of light receiving surfaces for detecting a tracking error signal,
An optical pickup device characterized in that the arrangement of the light receiving surface on the photodetector has a shape of "T". An optical pickup device according to any one of claims 1 to 7,
The photodetector has a plurality of light receiving surfaces for detecting a tracking error signal,
An optical pickup device characterized in that the arrangement of the light receiving surface on the photodetector is in the form of "I". An optical pickup device according to any one of claims 1 to 8,
A laser lighting circuit for driving the semiconductor laser in the optical pickup device;
A servo signal generation circuit that generates a focus error signal and a tracking error signal using a signal detected from the photodetector in the optical pickup device;
An optical disc apparatus equipped with an information signal reproducing circuit for reproducing an information signal recorded on an optical disc.

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