JP2012123883A - Optical pickup device and optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of obtaining a stable tracking error signal for a plurality of optical disks differing in track groove cycle, and an optical disk drive mounted therewith.SOLUTION: For an optical disk which has large track groove cycles on the optical disk between two optical disks which are substantially equal in wavelength of laser light and numerical aperture, a tracking error signal is detected from a plurality of light beams reflected by the disk. For the optical disk having small track groove cycles on the optical disk, on the other hand, a tracking error signal is obtained from one of the plurality of light beams reflected by the disk.

Description

  The present invention relates to an optical pickup device and an optical disc device, and more particularly to an optical pickup device that obtains a stable servo signal for a plurality of optical discs having different track groove periods and an optical disc device equipped with the optical pickup device.

  As background art of this technical field, there is, for example, Patent Document 1. This publication states that the conventional optical pickup device moves the spot on the photodetector when the objective lens is moved in order to correct the misalignment between the track and the focused spot. There is a problem that an offset occurs in the signal and stable information cannot be written and reproduced. ”As a means for solving the problem,“ the optical pickup device according to the present invention is divided into two in the first invention of the present application. The photodetector is divided into four in the left-right direction using the second and third boundary lines parallel to the first boundary line, and the tracking error signal is corrected using the differential signal of the outer detection element. There is a description.

  Further, in Patent Document 2, the problem is that “the optical system is simple, the offset generated by the translation of the objective lens and the inclination of the information recording medium can be suppressed, and the tracking error signal of the tracking error signal is changed even if the track interval of the information recording medium changes. A tracking error signal detection apparatus capable of maintaining the amplitude at the maximum is obtained. "As a solving means, two beams including one light beam having a phase difference of about 180 degrees on a half surface are used as an objective lens. The information recording medium is condensed and irradiated through the optical recording medium, and the interval in the direction perpendicular to the track on the information recording medium of the condensing spot formed by the two light beams is approximately an integral multiple of the track interval. A condensing spot is arranged on the information recording medium, and a tracking error signal is obtained from the difference in output between the pair of two-divided photodetectors. It was to obtain a. "And is described.

Japanese Patent Laid-Open No. 4-119531 Japanese Patent Laid-Open No. 9-81942

  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 disk radial direction (Rad direction) to perform tracking adjustment. The position of the objective lens is controlled by these signals.

  Regarding the tracking error signal, there is a big problem when an optical disk having a different track groove period of the disk is compatible with one pickup device. For example, DVD-R and DVD-RAMII represented by DVD correspond to it. Since DVD-R has a track groove period of 0.74 μm and DVD-RAM II has a track groove period of 1.23 μm, the diffraction angle due to the disk groove is greatly different between DVD-R and DVD-RAM II. For this reason, the relationship between the 0th-order diffracted light and the ± 1st-order diffracted light shown in Patent Document 1 differs depending on the recording / reproducing disk. In Patent Document 1, stable tracking error signals can be detected for a plurality of disks. There is a problem that cannot be done.

  On the other hand, in Patent Document 2, it is possible to detect a stable tracking error signal for a disk having a different track groove period by giving a phase difference of about 180 degrees to a substantially half surface of the diffraction grating. However, the configuration of Patent Document 2 has a big problem in the case of a disc having two or more layers. In Patent Document 2, two sub beams are generated in addition to a main beam by a diffraction grating, and three light beams are condensed on a disk. Then, the three light beams reflected from the disk are respectively incident on the two-divided light receiving unit as in Patent Document 2 (FIG. 7), and the tracking error signal is calculated by calculating the differential signal of the two-divided light receiving unit between the three beams. Is generated. With a configuration such as that of Patent Document 2, a stable tracking error signal can be generated in a single-layer disc. However, in the case of a two-layer disc, there is a problem that a stable tracking error signal cannot be obtained. Here, in the case of a two-layer disc, stray light from other layers is blurred and incident in addition to the signal light. At this time, the main problem is that the main beam is incident on the light receiving portion of the sub beam. In general, the light amount ratio between the main beam and the sub beam is 10 to 20: 1, and the light amount of the sub beam is very small with respect to the main beam. This is because the mark on the disk may be erased by the sub beam when the light amount of the sub beam increases. For this reason, when the light with a large amount of light from the main beam is incident on the light receiving portion of the sub beam with a small amount of light, two or more light beams interfere with each other, and the fluctuation component is detected in the tracking error signal. is there. When the tracking error signal fluctuates due to such factors, there is a problem that not only stable recording / reproduction cannot be performed but also the track cannot be tracked depending on conditions.

Also, if a part of the main beam is missing due to dust or scratches on the optical parts, the stray light amount of the main beam is larger than the signal amount of the sub beam, so an offset occurs in the tracking error signal, resulting in failure to follow the track. Is a problem.
Accordingly, an object of the present invention is to provide an optical pickup device that obtains a stable tracking error signal for a plurality of optical discs having different track groove periods, and an optical disc device equipped with the optical pickup device.

  In order to achieve the above object, the present invention provides an optical pickup device for reading a signal written on an optical disc by irradiating the optical disc with a laser beam, the laser light source for generating the laser beam, and the laser An objective lens for irradiating the optical disk with laser light generated by a light source, an actuator for displacing the relative position of the objective lens with respect to the optical disk, and detecting the laser light reflected from the optical disk A tracking error signal for at least two recording or rewritable optical discs using substantially the same wavelength of the laser beam and the numerical aperture of the objective lens. Are different.

  The present invention also provides an optical pickup device that reads a signal written on the optical disk by irradiating the optical disk with laser light, the laser light source generating the laser light, and the laser light generated by the laser light source. Is incident on the optical disk, and the objective lens is configured to irradiate the optical disk with the plurality of beams of the laser light branched by the diffraction grating, and the objective lens relative to the optical disk. And an optical detector that detects the laser beam reflected from the optical disk and converts it into an electrical signal, and sets the wavelength of the laser beam and the numerical aperture of the objective lens substantially equal to each other. In contrast to at least two types of recordable or rewritable optical discs used, at least one type of recordable or rewritable optical discs The optical signal obtained by detecting the reflected light from the optical disk of the plurality of light beams irradiated on the optical disk with the photodetector is output as a tracking error signal for other types of recording type or rewriting For a possible optical disc, an electrical signal obtained by detecting the reflected light from the optical disc of one optical beam included in a plurality of optical beams applied to the optical disc with the photodetector is used as a signal for a tracking error signal. It is characterized by output.

  The present invention also provides an optical pickup device that reads a signal written on the optical disk by irradiating the optical disk with laser light, the laser light source generating the laser light, and the laser light generated by the laser light source. Is incident on the optical disk, and the objective lens is configured to irradiate the optical disk with the plurality of beams of the laser light branched by the diffraction grating, and the objective lens relative to the optical disk. And an optical detector that detects the laser beam reflected from the optical disk and converts it into an electrical signal, and sets the wavelength of the laser beam and the numerical aperture of the objective lens substantially equal to each other. With respect to at least two types of recording type or rewritable type optical discs used, an optical disc having the longest track groove period having the recording track is used. In this case, an electrical signal obtained by detecting the reflected light from the optical disk of the plurality of light beams applied to the optical disk with the photodetector is output as a tracking error signal, and the recording track An optical signal obtained by detecting the reflected light from the optical disk of one optical beam included in a plurality of light beams applied to the optical disk with the photodetector. Is output as a tracking error signal.

  The present invention also provides an optical pickup device that reads a signal written on the optical disk by irradiating the optical disk with laser light, the laser light source generating the laser light, and the laser light generated by the laser light source. Is incident on the optical disc, and the optical lens is irradiated with an objective lens, an actuator for displacing the relative position of the objective lens with respect to the optical disc, and the laser beam reflected from the optical disc is detected and converted into an electrical signal. The optical detection unit generates a tracking error signal in accordance with information on the type of optical disc being recorded / reproduced by the optical disc apparatus on which the optical pickup device is mounted. Therefore, it is characterized in that the signal for switching is output after switching.

  The present invention also provides an optical pickup device that reads a signal written on the optical disk by irradiating the optical disk with laser light, the laser light source generating the laser light, and the laser light generated by the laser light source. Is incident on the optical disk, and the objective lens is configured to irradiate the optical disk with the plurality of beams of the laser light branched by the diffraction grating, and the objective lens relative to the optical disk. And an optical detector that detects the laser beam reflected from the optical disk and converts it into an electrical signal, and sets the wavelength of the laser beam and the numerical aperture of the objective lens substantially equal to each other. In contrast to at least two types of recording type or rewritable type optical discs used, the optical disc type corresponding to only a single layer disc The electrical signal obtained by detecting the reflected light from the optical disk of a plurality of light beams irradiated on the disk with the photodetector is output as a tracking error signal, and for an optical disk of a type corresponding to a multilayer disk. Is characterized in that an electrical signal obtained by detecting the reflected light from the optical disc of one optical beam included in a plurality of optical beams irradiated on the optical disc by the photodetector is output as a tracking error signal. Yes.

  The present invention also provides an optical disc apparatus for reading a signal written on the optical disc by irradiating the optical disc with a laser beam, the laser light source generating the laser light, and the laser light generated by the laser light source An objective lens that irradiates the optical disk with the laser light incident thereon, an actuator that displaces the relative position of the objective lens with respect to the optical disk, and the laser light reflected from the optical disk is detected and converted into an electrical signal. An optical pickup device for switching the signal output for the tracking error signal according to information on the type of optical disc that is output and recorded / reproduced by the optical disc device, a laser lighting circuit for driving the laser light source, A track on the optical disc of the objective lens is obtained from the electrical signal generated by the light detection unit. A servo signal generator for generating a tracking error signal for controlling a relative position in the radial direction and a focus error signal for controlling a relative position in the vertical direction, and the electric signal generated by the photodetector. An information signal reproducing circuit for reproducing an information signal recorded on an optical disk is provided.

  According to the present invention, it is possible to provide an optical pickup device that obtains a stable servo signal for a plurality of optical discs having different track groove periods, and an optical disc device equipped with the optical pickup device, which can contribute to improvement of the basic performance of the optical disc device. effective.

1 is a diagram illustrating an optical system of an optical pickup device in Embodiment 1. FIG. FIG. 3 is a diagram illustrating an arrangement of light receiving parts of the photodetector in the first embodiment. It is a 1st figure which shows the conventional photodetector. It is a 2nd figure which shows the conventional photodetector. It is a 1st signal waveform diagram for demonstrating the subject of a prior art. It is a 2nd signal waveform diagram for demonstrating the subject of a prior art. It is a characteristic view for demonstrating the subject of a prior art. FIG. 6 is a characteristic diagram showing effects in the first embodiment. FIG. 6 is a diagram illustrating another arrangement of the light receiving portions of the photodetector in the first embodiment. FIG. 6 is a diagram illustrating still another light receiving unit arrangement of the photodetector in the first embodiment. It is a figure which shows the signal connection method in Example 1. FIG. 5 is a diagram illustrating an optical system of an optical pickup device in Embodiment 2. FIG. 6 is a diagram illustrating another optical system of the optical pickup device in Embodiment 2. FIG. FIG. 10 is a diagram showing the arrangement of light receiving parts of a photodetector in Example 3. 6 is a diagram illustrating a hologram element in Example 3. FIG. It is a figure which shows the relationship between the light-receiving part arrangement | positioning of the photodetector at the time of recording / reproducing a signal in DVD in Example 4, and a light beam. It is a figure which shows the relationship between the light-receiving part arrangement | positioning of the photodetector at the time of recording / reproducing a signal in CD in Example 4, and a light beam. It is a figure which shows the other light-receiving part arrangement | positioning of the photodetector in Example 4. FIG. FIG. 10 is a diagram showing the relationship between the arrangement of light receiving parts of a photodetector and a light beam when a signal is recorded on and reproduced from a DVD in Example 5. FIG. 10 is a diagram showing the relationship between the arrangement of light receiving parts of a photodetector and a light beam when a signal is recorded on and reproduced from a CD in Example 5. It is a figure which shows the other light-receiving part arrangement | positioning of the photodetector in Example 5. FIG. FIG. 10 is a diagram illustrating a relationship between a light receiving portion arrangement of a photodetector and a light beam when a signal is recorded on and reproduced from a DVD in Embodiment 6. FIG. 10 is a diagram illustrating a relationship between a light receiving portion arrangement of a photodetector and a light beam when a signal is recorded on and reproduced from a CD according to a sixth embodiment. FIG. 10 is a diagram illustrating the relationship between the arrangement of light receiving parts of a photodetector and a light beam when a signal is recorded on and reproduced from a DVD in Example 7. FIG. 10 is a diagram showing the relationship between the arrangement of light receiving portions of a photodetector and a light beam when a signal is recorded on and reproduced from a CD in Example 7. FIG. 10 is a block diagram illustrating an optical reproducing device according to an eighth embodiment. FIG. 10 is a block diagram showing an optical recording / reproducing apparatus in Example 9.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an optical system of an optical pickup device according to the first embodiment. In this embodiment, DVD-R and DVD-RAM II will be described. However, the track groove period on the disk may be an optical disk such as DVD + R or DVD ± RW having the same track groove period as that of DVD-R. A plurality of different optical disks may be used.

  From the semiconductor laser 50, a light beam having a wavelength of about 650 nm is emitted as diverging light. The light beam emitted from the semiconductor laser 50 enters the diffraction grating 9. The incident light beam is separated into at least a main beam and two sub beams by the diffraction grating 9. At this time, it is assumed that the diffraction efficiency of the main beam and the two sub beams is 10: 1: 1.

  The light beam emitted from the diffraction grating 9 is reflected by 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 recording information on a recordable optical disk such as DVD ± R, DVD ± RW, or DVD-RAM, the recording surface of the optical disk is irradiated with a predetermined amount of light. Need to control. For this reason, the front monitor 53 detects a change in the amount of light of the semiconductor laser 50 and feeds it back to a drive circuit (not shown) of the semiconductor laser 50 when recording a signal on the recordable optical disk. This makes it possible to monitor the amount of light on the optical disc to be a predetermined amount.

  The light beam reflected by the beam splitter 52 is converted into a substantially parallel light beam by the collimator lens 51. The light beam that has passed through the collimator lens 51 is reflected by the rising mirror 55, passes through the quarter-wave plate 56, and is then focused on the optical disk by the objective lens 2 mounted on the actuator 5. Here, the rising mirror 55 and the quarter-wave plate 56 are shown to overlap the objective lens 2 mounted on the actuator 5, but the rising mirror 55 and the quarter-wave plate 56 from the back side of the figure. The objective lenses 2 are arranged in this order. The position of the sub beam spot in the Rad direction relative to the main beam spot is 0.615 μm, which is half the track groove period of the DVD-RAM II.

  The light beam reflected from the optical disk enters the hologram element 11 through the objective lens 2, the quarter wavelength plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The diffraction efficiency of the hologram element 11 is, for example, 0th order diffracted light: + 1st order diffracted light: −1st order diffracted light = 5: 2: 2, and the opposite defocus aberrations are given to ± 1st order diffracted lights. For example, + 1st order diffracted light converges at a position closer to the 0th order diffracted light than the collimating lens 51, and −1st order diffracted light has a defocus aberration that converges at a position farther from the collimating lens 51 than the 0th order diffracted light. Suppose that Here, the photodetector 10 has a light receiving portion arrangement as shown in FIG.

  FIG. 2 is a diagram illustrating the arrangement of the light receiving parts of the photodetector in the first embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam. The spots on the photodetector 10 are spots 1a to 3c, and 1, 2, and 3 in the symbols indicate 0th-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light by the diffraction grating 9, respectively. , B, and c indicate 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light by the hologram element 11, respectively. Specifically, the spot 1a is the 0th-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, the spot 2a is the + 1st-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, and the spot 3a is diffracted The -1st order diffracted light of the grating 9 and the 0th order diffracted light of the hologram element 11, the spot 1b is the 0th order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the hologram element 11, and the spot 2b is the + 1st order diffracted light of the diffraction grating 9 and the hologram element 11 is the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the hologram element 11, and the spot 1c is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light of the hologram element 11 and the spot 2c. Is the + 1st order diffracted light of the diffraction grating 9 and the -1st order diffracted light of the hologram element 11, and the spot 3c is the -1st order diffracted light of the diffraction grating 9. It shows the -1st-order diffracted light of the hologram element 11. The photodetector 10 is adjusted so that the spot 1a is condensed.

  Here, the signals A, B, and C obtained from the light receiving portions a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, and p shown in FIG. , D, E, F, G, H, I, J, K, L, M, N, O, P signals, and the following calculation, the focus error signal (FES), tracking error signal (TES), An RF signal (RF) is generated.

  Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.

In this embodiment, in contrast to at least two optical discs (DVD-R, DVD-RAM II, etc.) having substantially the same laser wavelength and numerical aperture, at least in the case of a disc (DVD-RAM II) having the longest track groove period on the disc. A tracking error signal is generated from at least two beams reflected from the disk, and at least in the case of a disk (DVD-R) having the smallest track groove period on the disk, a tracking error is generated from one beam reflected from the disk. It is characterized by generating a signal. Another feature of the present embodiment is that at least two tracking error signals are generated for a DVD-RAM II in which only a single-layer disc exists, and 1 for a DVD-R in which a single-layer disc and a dual-layer disc exist. It is characterized by detecting from one beam.
Here, in order to explain the effect of the present embodiment, a problem about Patent Document 1 will be described.

  3A and 3B are diagrams showing a conventional photodetector, and show the relationship between a light receiving portion and a spot when DVD-R and DVD-RAM II are recorded / reproduced in Patent Document 1 (FIG. 6). . Here, the region width v of the light receiving portion is matched to that of the DVD-R. FIG. 3A shows a case where a DVD-R is recorded / reproduced, and FIG. 3B shows a case where a DVD-RAM II is recorded / reproduced. 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 shaded portion indicates the interference region (push-pull pattern) between the zeroth-order diffracted light and the ± first-order diffracted light diffracted by the optical disk track Is shown. The arrows in the figure indicate the direction in which the outer shape of the light beam moves on the diffraction grating as the objective lens is displaced.

4A and 4B are signal waveform diagrams for explaining the problems of the prior art, and show the signal components of DVD-R and DVD-RAMII in the case of the configuration of Patent Document 1 shown in FIGS. 3A and 3B. It is a figure. FIG. 4A shows the case of DVD-R, and FIG. 4B shows the case of DVD-RAMII. Here, the signals detected by the light receiving units 10a to 10f are assumed to be I10a to I10f. At this time, when the DVD-R is recorded / reproduced with the configuration of Patent Document 1, the push-pull signal obtained by I10a-I10b and the DC offset obtained by kt ((I10c + I10d)-(I10e + I10f)) are calculated. Thus, a stable tracking error signal can be obtained even when the objective lens is displaced. Here, kt is a coefficient that prevents a DC component from being generated in the tracking error signal when the objective lens is displaced.
However, in the case of DVD-RAMII, the 0th-order diffracted light and the ± 1st-order diffracted light diffracted by the track of the optical disc largely intersect, so that the interference region is incident on the light receiving units 10c, 10d, 10e, and 10f that detect the DC offset. Resulting in. For this reason, the push-pull signal is included in the offset signal obtained by kt ((I10c + I10d) − (I10e + I10f)).

  As a result, the push-pull signal component obtained by I10a-I10b is subtracted, and the tracking error signal amplitude becomes very small as shown in FIG. 4B. For example, in order to solve this problem, it is possible to reduce the push-pull signal component of ((I10c + I10d) − (I10e + I10f)) by increasing the region width v of the light receiving unit, but the kt increases accordingly. There is a problem that becomes.

FIG. 5 is a characteristic diagram for explaining the problem of the prior art. The tracking error signal (I10a-I10b) -kt ((I10c + I10d)-(I10e + I10f)), DC offset signal when the region width v is changed. The simulation results of the push-pull signal amplitude and kt of ((I10c + I10d)-(I10e + I10f)) are shown. Here, the push-pull signal amplitude is normalized by the push-pull signal amplitude of (I10a-I10b). The parameters of the pickup device used for the simulation are shown below.

* Parameter wavelength of this example: 650 nm
Objective lens NA: 0.65
Objective lens focal length: 2.0mm
Collimating lens focal length: 12.0mm

From this figure, in order not to generate an amplitude in the DC offset signal ((I10c + I10d) − (I10e + I10f)), the region width v needs to be 90% or more with respect to the effective diameter ratio (the right side attached to the horizontal axis in the figure). See the triangle). However, in this case, kt is about 18, and for example, when a minute offset occurs in the DC offset signal ((I10c + I10d) − (I10e + I10f)) when passing through scratches or dust on the disk, the offset The signal is multiplied by 18 and calculated as a tracking error signal. For this reason, when kt increases, the tracking error signal greatly fluctuates due to disturbance, and stable tracking control cannot be performed. In consideration of practical use, it is desirable that kt is about 1 to 3. However, for example, when kt is set to 3, the tracking error signal amplitude is only about 25% of the push-pull signal amplitude of (I10a-I10b) from FIG. 5 (the left triangle on the horizontal axis in the figure). The DVD-RAMII cannot perform stable tracking control. For this reason, it is difficult to realize compatibility of DVD-R and DVD-RAM II with the configuration of Patent Document 1 from the viewpoint of tracking error signal detection.

Furthermore, there is a problem in the case of supporting a DVD-ROM. In a DVD-ROM or the like, there is a DPD detection method in which one beam is detected by being divided into four, and a tracking error signal is detected from a signal phase difference. In order to support the DPD detection method in Patent Document 2, it is necessary to divide the light receiving portions 10a and 10b in the disk tangential direction (Tan direction). However, if the light beam is divided in the Tan direction, the number of light receiving portions is eight, so that there is a problem that amplifier noise when converting from a light beam to an electric signal becomes large, and a satisfactory reproduction signal performance cannot be obtained.
The above problem is not described in Patent Document 1, and therefore no solution is described at all.

  On the other hand, in Patent Document 2, it is possible to detect a stable tracking error signal for a disk having a different track groove period by giving a phase difference of about 180 degrees to a substantially half surface of the diffraction grating. However, the configuration of Patent Document 2 has a big problem in the case of a disc having two or more layers. In Patent Document 2, two sub beams are generated in addition to a main beam by a diffraction grating, and three light beams are condensed on a disk. Then, the three light beams reflected from the disk are respectively incident on the two-divided light receiving unit as in Patent Document 2 (FIG. 7), and tracking is performed by calculating between the differential signal of the two-divided light receiving unit and the three beams. An error signal is generated. With a configuration such as that of Patent Document 2, a stable tracking error signal can be generated in a single-layer disc. However, a stable tracking error signal cannot be obtained in the case of a two-layer disc. In the case of a two-layer disc, stray light from other layers is incident in addition to the signal light, so that it becomes a big problem that the main beam is incident on the light receiving portion of the sub beam. In general, the light amount ratio between the main beam and the sub beam is 10 to 20: 1, and the light amount of the sub beam is very small with respect to the main beam. This is because the mark on the disk is erased by the sub beam when the light amount of the sub beam increases, and therefore the light amount of the sub beam is reduced. For this reason, if a light beam with a large amount of light on the light detector 10 is incident on a light-receiving portion of a sub-beam with a small amount of light, two or more light beams interfere with each other, and the fluctuation component thereof becomes a tracking error. It will be detected as a signal. In particular, since the sub beam is smaller than the main beam, it is necessary to amplify the sub beam signal in order to obtain the tracking error signal, and even a small fluctuation component causes a large offset fluctuation.

When the tracking error signal fluctuates due to such factors, there is a problem that not only stable recording / reproduction cannot be performed but also the light beam cannot follow the track depending on conditions.
In addition, if a part of the light beam is missing due to dust or scratches on the disk, the stray light amount of the main beam is larger than the signal light amount of the sub beam, so an offset occurs in the tracking error signal and consequently the track cannot be tracked. Is a problem.
The above problem is not described in Patent Document 2, and therefore no solution is described at all.

In the present embodiment, these problems can be solved. First, a description will be given of recording / reproducing of the DVD-R of the present embodiment. In the configuration of this embodiment using the signals A to F detected by the light receiving units a to f shown in FIG. 2, when recording / reproducing a DVD-R, the push-pull obtained by ((A + B)-(C + D)) By calculating the signal and the DC offset obtained by kt1 ((E + F) − (G + H)), a stable tracking error signal can be obtained even when the objective lens moves in the Rad direction. Here, kt1 is a coefficient for preventing a DC offset from being generated in the tracking error signal when the objective lens is displaced.
FIG. 6 is a characteristic diagram showing the effect in the first embodiment. The tracking error signal ((A + B) − (C + D)) − kt1 ((E + F) − (G + H)), DC when the region width v is changed. The push-pull signal amplitude of ((E + F) − (G + H)) of the offset signal and the simulation result of kt1 are shown. Here, the push-pull signal amplitude is normalized by the push-pull signal amplitude of ((A + B) − (C + D)). The calculation parameters are the same as those in FIG.

  From FIG. 6, for example, when kt is set to 3, the tracking error signal amplitude is obtained about 80% of the push-pull signal amplitude of ((A + B)-(C + D)) (refer to the triangular part attached to the horizontal axis in the figure). . This is practically satisfactory and stable tracking servo control is possible. Here, in the case of a two-layer disc, stray light from, for example, the spot 1a or the spot 1c enters the light receiving portions a to h that detect the tracking error signal shown in FIG. When the light amount ratio of the main and sub beams is 10 to 20: 1 as in Patent Document 2, an interference signal or an offset signal such as a scratch or dust is generated for a sub beam having a small light amount. In this case, the light quantity ratio of the spot 1a, the spot 1b, and the spot 1c is 5: 2: 2, and the light quantity difference is small, so that it is hardly affected by signal fluctuations, scratches, dust, and the like due to interference.

  In addition, since the DPD signal that is a tracking error signal of the DVD-ROM is detected from the light receiving portions a to h, the RF signal is not affected at all. In particular, in the case of the present embodiment, the amplifier noise is reduced by detecting the RF signal by one light receiving unit, and it is possible to improve the signal deterioration due to the separation of the light amount.

  Next, the recording / reproducing time of DVD-RAM II will be described. In the case of DVD-RAMII, a tracking error signal is generated from the main beam diffracted by the diffraction grating 9 and two sub-spots. On the disc, the position in the Rad direction of the sub beam spot relative to the main beam spot is 0.615 μm, which is half of the track groove period of DVD-RAMII, so that (A + B + E + F) − (C + D + G + H) detected from the main beam The (IJ) and (KL) push-pull signals detected from the sub-beams are 180 degrees out of phase. On the other hand, since the DC offset accompanying the movement of the objective lens is generated in the same direction, a stable tracking error signal without a DC offset can be detected by calculating the differential signal of the main beam output signal and the sub beam output signal.

  As described above, in this embodiment, the disc having the longest track groove period on the disc (DVD-RAMII) is compared to at least two optical discs (DVD-R, DVD-RAMII, etc.) having substantially the same laser wavelength and numerical aperture. In this case, a tracking error signal is generated from at least two beams reflected from the disk. At least in the case of a disk (DVD-R) having the smallest track groove period on the disk, a single beam reflected from the disk is used. A tracking error signal is generated. As another feature of the present embodiment, with respect to DVD-RAM II in which only a single layer disc exists, a tracking error signal is generated from at least two beams reflected from the disc, and a DVD- in which a single layer disc and a dual layer disc exist. R is detected from one beam reflected from the disk.

FIG. 7 is a diagram illustrating another arrangement of the light receiving portions of the photodetector in the first embodiment. In the present embodiment, the photodetector 10 has been described with reference to FIG. 2. For example, as shown in FIG. 7, the first-order diffracted light (1c, 2c, 3c) of the hologram element may be divided and detected by the photodetector 10. The signal may be calculated and used as a tracking error signal. Further, the diffraction efficiencies of the diffraction grating 9 and the hologram element 11 are not limited, and the same effect can be obtained even if different from the present embodiment. In this embodiment, the 0th-order diffracted light of the hologram element 11 is detected as an RF signal. However, the present invention is not limited to this. For example, the diffraction efficiency of the hologram element is 0th-order diffracted light: + 1st-order diffracted light: -1st-order diffracted light = As 0: 1: 1, it may be detected by the arrangement of the light receiving parts as shown in FIG. Similarly, the diffraction efficiency of the hologram element may be detected by arranging the light receiving portions as shown in FIG. 8, assuming that the diffraction efficiency of the hologram element is 0th order diffracted light: + 1st order diffracted light: -1st order diffracted light = 1: 1: 0. When a hologram element is used as in this embodiment, the diffraction angle (light receiving portion condensing position) may slightly change as the laser wavelength changes with temperature and laser output. In response to this problem, the diffraction efficiency of the hologram element is assumed to be 0th order diffracted light: + 1st order diffracted light: −1st order diffracted light = 1: 1: 0, and light receiving part a, light receiving part b, light receiving part c, light receiving part d, light receiving part e When the 0th-order diffracted light is detected by the light receiving part f and the light receiving part g, the spot 1b does not move even if the wavelength is displaced. For this reason, there is a feature that a stable tracking error signal can be obtained even if the wavelength is displaced. Further, with respect to the light receiving part m, the light receiving part n, and the light receiving part o of the focus error signal light receiving part, the moving direction of the spot 1c accompanying the wavelength displacement is the Rad direction, and the light receiving part m, the light receiving part n, and the light receiving part o There is no problem because it extends in the Rad direction. Further, the light receiving part m, the light receiving part n, and the light receiving part o may be further expanded in the Rad direction. Here, although the minus first-order light of the hologram element is not detected, an RF signal, a tracking error signal, or the like may be generated by arranging and detecting a light receiving unit.
Further, for example, when the diffraction efficiency of the hologram element is 0th order diffracted light: + 1st order diffracted light: −1st order diffracted light = 1: 0: 1, the focus error signal is detected by the 0th order diffracted light and the −1st order light. good.

  FIG. 8 is a diagram illustrating still another light receiving unit arrangement of the photodetector in the first embodiment. In this case, the same effect can be obtained by performing the following calculation.

  Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted. At this time, there are three RF signal light receiving parts, but there is no problem in practical use. Further, it is possible to reduce noise by connecting the light receiving part m and the light receiving part o.

  The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of discs and does not depend on the focus error signal detection method. For example, even in the spot size detection method as in the present embodiment, The astigmatism method or the knife edge method may be used. Furthermore, the diffraction grating 9 is not limited to the diffraction grating of the present embodiment. For example, the diffraction grating 9 as disclosed in JP-A-2007-234175 and JP-A-2005-122869 is similar. The effect is obtained.

  Further, although the signal output method has not been described in the present embodiment, for example, the optical pickup device may output each signal of DVD-R and DVD-RAMII, or a signal calculated in the optical pickup device. May be output. Further, a disc may be inserted into the optical disc device, and the signal output of the photodetector 11 or the optical pickup device may be changed based on the disc discrimination result in the optical disc device. However, if the number of signal output pins is increased, it is difficult to reduce the size. Therefore, the number of signal output pins of the optical pickup may be reduced by outputting as shown in FIG.

  FIG. 9 is a diagram illustrating a signal connection method according to the first embodiment. Here, the switches SW1 and SW2 are switches for switching between DVD-R, DVD-RAMII, and DVD-ROM. A tracking error signal is obtained by performing the following calculation on the signals I1 to I6 in the figure.

Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves.
Here, the signal connection is characterized in that when a DVD-R is recorded / reproduced, a light receiving unit output for detecting 0th-order diffracted light and ± 1st-order diffracted light diffracted by a track, and when recording / reproducing a DVD-RAMII are recorded. By switching the light receiving unit output for detecting the main beam of the diffraction grating 9 with a switch, a stable tracking error signal of DVD-R and DVD-RAMII can be obtained on the drive side without any change other than kt1 and kt2. Yes. In addition, the light receiving unit output for mainly detecting the 0th-order diffracted light diffracted by the track when recording / reproducing the DVD-R and the light receiving unit output for detecting the sub beam when recording / reproducing the DVD-RAM II are switched by a switch. It is possible as well.
By reducing the number of signal output pins of the optical pickup device in this way, the size can be reduced. Note that the switches SW1 and SW2 do not turn ON or OFF at the same time, and may be one input.

FIG. 10 is a diagram illustrating an optical system of the optical pickup device according to the second embodiment. In the first embodiment, the hologram element 11 is used to defocus the light beam as an aberration. However, in this embodiment, the compound prism is used and the light beam is branched to give the defocus. . Other than that, the configuration is the same as that of the first embodiment.
In the present embodiment, a configuration different from that of the first embodiment will be described. As in the first embodiment, the light beam reflected from the disk is incident on the composite prism 15 through the objective lens 2, the quarter-wave plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The composite prism 15 has at least reflecting surfaces 15a, 15b, and 15c. The light beam incident on the composite prism 15 is reflected and transmitted by the reflecting surfaces 15 a and 15 b and reflected by the reflecting surface 15 c, and each light beam enters the photodetector 10.

  Here, the photodetector 10 has a light receiving portion arrangement as shown in FIG. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam. The spots on the photodetector 10 are spots 1a to 3c, and 1, 2, and 3 in the symbols indicate the 0th-order diffracted light, the + 1st-order diffracted light, and the -1st-order diffracted light, respectively. , B, c are reflected light from the reflecting surface 15b, transmitted light from the reflecting surface 15a, and reflected light from the reflecting surface 15c, respectively. Specifically, the spot 1a is the 0th order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15b, the spot 2a is the + 1st order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15b, and the spot 3a is the reflected light of the diffraction grating 9. -1st order diffracted light and reflection on reflecting surface 15b, spot 1b is 0th order diffracted light on diffraction grating 9 and transmitted light on reflecting surface 15a, spot 2b is + 1st order diffracted light on diffraction grating 9 and transmitted light on reflecting surface 15a, spot 3b is the −1st order diffracted light of the diffraction grating 9 and the transmitted light of the reflecting surface 15a, the spot 1c is the + 1st order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15c, and the spot 2c is the + 1st order diffracted light of the diffraction grating 9 and The reflected light of the reflecting surface 15c and the spot 3c indicate the -1st order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15c. The photodetector 10 is adjusted so that the spot 1a is condensed. Here, the light quantity ratio of the spot a, the spot b, and the spot c incident on the photodetector 10 is 5: 1: 1.

  Here, the signals A, B, and C obtained from the light receiving portions a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, and p shown in FIG. , D, E, F, G, H, I, J, K, L, M, N, O, and P, and the focus error signal (FES) and tracking error by the above-described calculation (Equation 1). A signal (TES) and an RF signal (RF) are generated.

  Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.

  Since the tracking error detection method of the present embodiment and the tracking error signal detection method of Embodiment 1 are the same, the same effect as in Embodiment 1 can be obtained. In addition, when using a hologram element, the diffraction angle (light receiving portion condensing position) changes slightly as the laser wavelength changes with temperature and laser output, but a composite prism is used as in this embodiment. It becomes possible to suppress it.

  In the present embodiment, the photodetector 10 has been described with reference to FIG. 2. For example, as shown in FIG. 7, the reflected light (1c, 2c, 3c) of the reflecting surface 15c may be divided and detected by the photodetector 10. The signal may be calculated and used as a tracking error signal. Further, the diffraction efficiency of the diffraction grating 9 is not limited, and the same effect can be obtained even if different from the present embodiment. In this embodiment, the light quantity ratio of the spot a, the spot b, and the spot c incident on the photodetector 10 is 5: 1: 1, but the same effect can be obtained even if it is different from this embodiment. It is done.

  Furthermore, in this embodiment, the reflected light of the reflecting surface 15b of the composite prism is detected as an RF signal. However, the present invention is not limited to this. For example, the reflecting surfaces of the composite prism are only 15a and 15c, and light reception as shown in FIG. You may detect by partial arrangement. In this case, the same effect can be obtained by performing the above-described calculation (Equation 2).

  Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted. At this time, there are three RF signal light receiving parts, but there is no problem in practical use. Further, it is possible to reduce noise by connecting the light receiving part m and the light receiving part o.

The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of discs and does not depend on the focus error signal detection method. For example, even in the spot size detection method as in the present embodiment, The astigmatism method or the knife edge method may be used. Further, the diffraction grating 9 is further limited to that of the present embodiment, and the diffraction grating 9 is not limited to the diffraction grating of the present embodiment. For example, Japanese Patent Laid-Open No. 2007-234175 and Japanese Patent Laid-Open No. 2005-122869. Even with such a diffraction grating, the same effect can be obtained. The optical system is not limited to that shown in FIG. 10. For example, an optical system in which the semiconductor laser 50 and the photodetector 10 are arranged in the same direction as shown in FIG. 11 may be used.
FIG. 11 is a diagram illustrating another optical system of the optical pickup device according to the second embodiment. In this way, the optical pickup device can be reduced in size.

  FIG. 12 is a diagram illustrating the arrangement of the light receiving portions of the photodetector 10 of the optical pickup device according to the third embodiment. The difference from the first embodiment is that the pattern of the hologram element 11 and the light receiving portion of the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  In the present embodiment, a configuration different from that of the first embodiment will be described. As in the first embodiment, the light beam reflected from the disk enters the hologram element 11 through the objective lens 2, the quarter-wave plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The hologram element 11 is divided into a plurality of regions and at the same time is an optical element having a characteristic that gives a predetermined defocus aberration to the outgoing diffracted light. The light beams separated by the hologram element 11 travel in different directions for each region and enter the photodetector 10. A plurality of light receiving portions are formed on the photodetector 10, and each light receiving portion is irradiated with a light beam divided by the hologram element 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.

  FIG. 13 is a diagram illustrating the shape of the hologram element 11 according to the third embodiment. The solid line indicates the boundary line of the region, and the alternate long and short dash line indicates the outer shape of the light beam. The hologram element 11 is divided into two regions, a region I and a region II, in the Tan direction by a dividing line passing through the approximate center of the light beam. Further, the diffraction efficiency of the 0th-order diffracted light, the + 1st-order diffracted light, and the −1st-order diffracted light of the hologram element 11 is, for example, 5: 2: 2. Then, opposite defocus aberrations are given to the ± first-order diffracted lights. For example, + 1st order diffracted light converges at a position closer to the 0th order diffracted light than the collimating lens 51, and −1st order diffracted light has a defocus aberration that converges at a position farther from the collimating lens 51 than the 0th order diffracted light. Suppose that

  Here, the photodetector 10 has a light receiving portion arrangement as shown in FIG. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam. The spots on the photodetector 10 are spots 10a to 30e, and 10, 20, and 30 in the symbols indicate the 0th-order diffracted light, the + 1st-order diffracted light, and the -1st-order diffracted light, respectively. , B, c, d, and e are the 0th order diffracted light of region I and region II of the hologram element 11, the + 1st order diffracted light of region I, the −1st order diffracted light of region I, the + 1st order diffracted light of region II, and − of the region II, respectively. 1st order diffracted light is shown. Specifically, the spot 10a is the 0th-order diffracted light of the diffraction grating 9 and the region I of the hologram element 11 and the 0th-order diffracted light of the region II, and the spot 20a is the + first-order diffracted light of the diffraction grating 9 and the region I of the hologram element 11. The second order diffracted light of the region II, the spot 30 a is the −1st order diffracted light of the diffraction grating 9 and the region I of the hologram element 11, and the zeroth order diffracted light of the region II and the spot 10 b are the 0th order diffracted light of the diffraction grating 9 and the hologram element 11. The + 1st order diffracted light of the region I, the spot 20b is the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the region I of the hologram element 11, and the spot 30b is the −1st order diffracted light of the diffraction grating 9 and the region I of the hologram element 11. The + 1st order diffracted light, the spot 10c is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light in the region I of the hologram element 11, and the spot 20c is the diffraction grating 9 The + 1st order diffracted light and the −1st order diffracted light in the region I of the hologram element 11, the spot 30 c are the −1st order diffracted light in the diffraction grating 9 and the −1st order diffracted light in the region I of the hologram element 11, and the spot 10 d is 0% of the diffraction grating 9. The first order diffracted light and the + 1st order diffracted light of the region II of the hologram element 11, the spot 20 d are the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the region II of the hologram element 11, and the spot 30 d is the −1st order diffracted light of the diffraction grating 9 The + 1st order diffracted light of the region II of the hologram element 11, the spot 10 e is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light of the region II of the hologram element 11, and the spot 20 e is the + 1st order diffracted light of the diffraction grating 9 and the hologram element 11. The -1st order diffracted light in the region II of FIG. 2A is the spot 30e. Shows. The photodetector 10 is adjusted so that the spots 10c and 10e are condensed.

  Here, the light receiving units ma, mb, mc, md, me, mf, mg, mh, ia, ib, ja, jb, ka, kb, la, lb, p, ua, ub, wa, wb shown in FIG. Using signals MA, MB, MC, MD, ME, MF, MG, MH, IA, IB, JA, JB, KA, KB, LA, LB, P, UA, UB, WA, WB obtained from Thus, a focus error signal (FES), a tracking error signal (TES), and an RF signal (RF) are generated by the following calculation.

  Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a knife edge detection method, and since this method is known, the description thereof is omitted.

  In this embodiment, the focus aberration given by the hologram element 11 is absorbed by the diffracted light on one side, and the spot diameter of the other diffracted light on the photodetector 10 is increased. Although the hologram element 11 is divided into two in the vertical direction, the tracking error signal detection is the same as that of the first embodiment in consideration of the spot light receiving method and calculation, and therefore the same effect as that of the first embodiment can be obtained. it can. In Example 1, from the viewpoint of detecting the focus error signal by the spot size method using the ± first-order diffracted light of the hologram element 11, the effective diameter of the spot on the photodetector could not be increased. In this embodiment, since the focus error signal is detected by converging the −1st order diffracted light of the hologram element, the amount of defocus aberration of the hologram element can be greatly given to the configuration of the first embodiment. It is also possible to increase the effective diameter of the + 1st order diffracted light on the photodetector. For this reason, by increasing the effective diameter of the + 1st order diffracted light, it is possible to make it more resistant to positional deviation of the light receiving unit. Further, with respect to the focus error signal, a double knife edge in which two knife edge type light receiving parts are arranged as in the present embodiment can be configured to be resistant to positional deviation of the light receiving part. By adopting such a configuration, it is possible to provide a configuration that is resistant to the positional deviation of the photodetector. Further, in the present embodiment, it is needless to say that the same effect can be obtained even if the hologram element is changed to a composite prism from the viewpoint of providing defocus. In this case, the hologram element is a normal diffraction grating having two or more divisions. The diffraction efficiencies of the diffraction grating 9 and the hologram element of this embodiment are not limited, and similar effects can be obtained even if they are different from those of this embodiment. In this embodiment, the hologram element is divided into two parts, but the present invention is not limited to this.

  The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of disks, and does not depend on the focus error signal detection method. For example, the knife edge method may be used as in this embodiment. However, an astigmatism method or a spot size detection method may be used. Furthermore, the diffraction grating 9 is not limited to the diffraction grating of the present embodiment. For example, the diffraction grating 9 as disclosed in JP-A-2007-234175 and JP-A-2005-122869 is similar. The effect is obtained.

  FIG. 14 shows the arrangement of the light receiving parts of the photodetector 10 of the optical pickup device according to the fourth embodiment. The difference from the first embodiment is that the semiconductor laser 50 is a two-wavelength laser, and the light receiving part of the photodetector 10 is different. The other configuration is the same as that of the first embodiment.

  A two-wavelength semiconductor laser is a laser capable of emitting lasers of two wavelengths. Here, it is assumed that the laser can emit a wavelength of 650 nm corresponding to DVD and a wavelength of 785 nm corresponding to CD. However, the wavelength is not limited, and for example, the wavelength corresponding to BD may be 405 nm. This embodiment will be described with reference to the optical system of FIG.

  First, the case of recording / reproducing a DVD will be described. From the semiconductor laser 50, a light beam having a wavelength of about 650 nm is emitted as diverging light. The light beam emitted from the semiconductor laser 50 enters the diffraction grating 9. The incident light beam is separated by the diffraction grating 9 into at least a main beam and two sub beams. At this time, it is assumed that the diffraction efficiency of the main beam and the two sub beams is 10: 1: 1.

  The light beam emitted from the diffraction grating 9 is reflected by 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 recording information on a recordable optical disk such as DVD ± R, DVD ± RW, or DVD-RAM, the recording surface of the optical disk is irradiated with a predetermined amount of light. Need to control. For this reason, the front monitor 53 detects a change in the amount of light of the semiconductor laser 50 and feeds it back to a drive circuit (not shown) of the semiconductor laser 50 when recording a signal on the recordable optical disk. This makes it possible to monitor the amount of light on the optical disc to be a predetermined amount.

  The light beam reflected by the beam splitter 52 is converted into a substantially parallel light beam by the collimator lens 51. The light beam that has passed through the collimator lens 51 is reflected by the rising mirror 55, passes through the quarter-wave plate 56, and is then focused on the optical disk by the objective lens 2 mounted on the actuator 5. Here, the position in the Rad direction of the sub beam spot with respect to the main beam spot is 0.615 μm, which is half the track groove period of the DVD-RAM II.

  The light beam reflected from the optical disk enters the hologram element 11 through the objective lens 2, the quarter wavelength plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The diffraction efficiency of the hologram element 11 is, for example, 0th order diffracted light: + 1st order diffracted light: −1st order diffracted light = 5: 2: 2, and the opposite defocus aberrations are given to ± 1st order diffracted lights. For example, + 1st order diffracted light converges at a position closer to the 0th order diffracted light than the collimating lens 51, and −1st order diffracted light has a defocus aberration that converges at a position farther from the collimating lens 51 than the 0th order diffracted light. Suppose that

  FIG. 14 is a diagram showing the relationship between the arrangement of the light receiving portions of the photodetector 10 and the light beam when recording and reproducing signals on a DVD in the fourth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the DVD is recorded / reproduced. The spots on the photodetector 10 are spots 1aa to 3ac, and 1, 2, and 3 in the symbols indicate the 0th-order diffracted light, the + 1st-order diffracted light, and the -1st-order diffracted light, respectively. , Ab, and ac represent 0th-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light of the hologram element 11, respectively. Specifically, the spot 1aa is the 0th-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, the spot 2aa is the + 1st-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, and the spot 3aa is diffracted The -1st order diffracted light of the grating 9 and the 0th order diffracted light of the hologram element 11, the spot 1ab is the 0th order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the hologram element 11, and the spot 2ab is the + 1st order diffracted light of the diffraction grating 9 and the hologram element 11 is the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the hologram element 11, and the spot 1ac is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light of the hologram element 11 and the spot 2ac. Are the + 1st order diffracted light of the diffraction grating 9 and the -1st order diffracted light of the hologram element 11, and the spot 3ac is the diffraction grating And the -1st-order diffracted light indicates the -1-order diffracted light of the hologram element 11. The photodetector 10 is adjusted so that the spot 1aa is condensed.

  Here, the signals A1, B1, C1 obtained from the light receiving portions a1, b1, c1, d1, e1, f1, g1, h1, i1, j1, k1, l1, m1, n1, o1, n2 shown in FIG. , D1, E1, F1, G1, H1, I1, J1, K1, L1, M1, N1, O1, and N2 signals, the focus error signal (FES), tracking error signal (TES), An RF signal (RF) is generated.

  Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.

Since the tracking error detection method of the present embodiment and the tracking error signal detection method of Embodiment 1 are the same, the same effect as in Embodiment 1 can be obtained.
Next, a case where a CD is recorded / reproduced will be described. From the semiconductor laser 50, a light beam having a wavelength of about 785 nm is emitted as diverging light. The light beam emitted from the semiconductor laser 50 enters the diffraction grating 9. The incident light beam is separated into at least a main beam and two sub beams by the diffraction grating 9.

  The light beam emitted from the diffraction grating 9 is reflected by 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 recording information on a recordable optical disk such as a CD-R or CD-RW, it is necessary to control the light quantity of the semiconductor laser with high accuracy in order to irradiate the recording surface of the optical disk with a predetermined light quantity. is there. For this reason, the front monitor 53 detects a change in the amount of light of the semiconductor laser 50 and feeds it back to a drive circuit (not shown) of the semiconductor laser 50 when recording a signal on the recordable optical disk. This makes it possible to monitor the amount of light on the optical disc to be a predetermined amount.

  The light beam reflected by the beam splitter 52 is converted into a substantially parallel light beam by the collimator lens 51. The light beam that has passed through the collimator lens 51 is reflected by the rising mirror 55, passes through the quarter-wave plate 56, and is then focused on the optical disk by the objective lens 2 mounted on the actuator 5. Here, the position in the Rad direction of the spot of the sub beam with respect to the spot of the main beam is 0.743 μm. This is 0.615 μm in the case of the wavelength of DVD, whereas it is 0.743 μm in the case of CD because it is diffracted by the diffraction grating 9 by the wavelength.

  The light beam reflected from the optical disk enters the hologram element 11 through the objective lens 2, the quarter wavelength plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. Similar to DVD recording / reproduction, the ± first-order diffracted light of the hologram element 11 is given opposite defocus aberrations. Here, for example, + 1st order diffracted light converges at a position closer to the 0th order diffracted light than the collimating lens 51, and −1st order diffracted light converges at a position farther from the collimating lens 51 than the 0th order diffracted light. Is given.

  FIG. 15 is a diagram illustrating the relationship between the arrangement of the light receiving unit of the photodetector 10 and the light beam when a signal is recorded on and reproduced from the CD in the fourth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the CD is recorded / reproduced. The spots on the photodetector 10 are spots 1ba to 3bc, and 1, 2, and 3 in the symbols indicate 0th-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light of the diffraction grating 9, respectively. , Bb, and bc respectively indicate 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light of the hologram element 11. Specifically, the spot 1ba is the 0th-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, the spot 2ba is the + 1st-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, and the spot 3ba is diffracted The -1st order diffracted light of the grating 9 and the 0th order diffracted light of the hologram element 11, the spot 1bb is the 0th order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the hologram element 11, and the spot 2bb is the + 1st order diffracted light of the diffraction grating 9 and the hologram element 11 is the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the hologram element 11, and the spot 1bc is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light of the hologram element 11 and the spot 2bc. Are the + 1st order diffracted light of the diffraction grating 9 and the -1st order diffracted light of the hologram element 11, and the spot 3bc is the diffraction grating And the -1st-order diffracted light indicates the -1-order diffracted light of the hologram element 11.

From FIG. 14 and FIG. 15, it can be seen that the position of the spot 1aa when the DVD is recorded / reproduced is different from the position of the spot 1ba when the CD is recorded / reproduced. This is because the emission points of the DVD and CD of the two-wavelength laser are different, and such emission point shift is a problem when the DVD and CD are compatible with the two-wavelength laser.
Here, the signals A2, B2, C2 obtained from the light receiving parts a2, b2, c2, d2, e2, f2, g2, h2, i2, j2, k2, l2, m2, n2, o2, n1 shown in FIG. , D2, E2, F2, G2, H2, I2, J2, K2, L2, M2, N2, O2, and N1 signals, the focus error signal (FES), tracking error signal (TES), An RF signal (RF) is generated.

Note that kt3 in the equation is a coefficient for preventing a DC offset from being generated in the tracking error signal when the objective lens moves. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.
Here, in the case of a CD, a tracking error signal is generated from the main beam diffracted by the diffraction grating 9 and two sub spots. The position in the Rad direction of the sub beam spot relative to the main beam spot on the disc is slightly deviated from half the CD track groove period, but (A2 + B2 + E2 + F2) − (C2 + D2 + G2 + H2) detected from the main beam. The detected push-pull signal of (I2-J2) + (K2-L2) is 180 degrees out of phase. On the other hand, since the DC offset accompanying the movement of the objective lens is generated in the same direction, a stable tracking error signal without a DC offset can be detected by calculating the differential signal of the main beam output signal and the sub beam output signal. Here, the Rad direction position of the sub beam spot with respect to the main beam spot on the disk is slightly deviated from the half track groove period of the CD, so that the eccentricity characteristic of the disk is slightly deteriorated. Since the track groove period of CD is larger than that of DVD, there is no practical problem. Further, the diffraction grating 9 may be a diffraction grating as disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2008-176899, 2007-234175, and 2005-122869 in order to improve the eccentricity characteristics of the disk. . Further, the position of the sub spot may be optimized on the CD side so that the DVD-RAM II is shifted, or the sub spot may be arranged so as to be intermediate between the CD and the DVD-RAM.

As described above, in this embodiment, the disc having the longest track groove period on the disc (DVD-RAMII) is compared to at least two optical discs (DVD-R, DVD-RAMII, etc.) having substantially the same laser wavelength and numerical aperture. In this case, a tracking error signal is generated from at least two beams reflected from the disk, and at least in the case of a disk (DVD-R) having the smallest track groove period on the disk, at least one reflected from the disk. A tracking error signal is generated from two beams. Another feature of the present embodiment is that for DVD-RAMII and CD-R in which only a single-layer disc exists, tracking error signals are generated from at least two beams, and single-layer and double-layer discs exist. DVD-R is characterized by detection from one beam. Further, in the present embodiment, DVD and CD compatibility are realized by sharing the light receiving portions n1 and n2 for DVD and CD.
FIG. 16 is a diagram illustrating another arrangement of the light receiving portions of the photodetector in the fourth embodiment. As shown in FIG. 16, the light receiving unit may be divided so that the light receiving units nb <b> 1 and nb <b> 2 that receive the RF signal are reduced in order to reduce the noise of the RF signal.
Further, the diffraction efficiencies of the diffraction grating 9 and the hologram element 11 are not limited, and the same effect can be obtained even if different from the present embodiment. In this embodiment, the 0th-order diffracted light of the hologram element 11 is detected as an RF signal. However, the present invention is not limited to this. For example, the diffraction efficiency of the hologram element is 0th-order diffracted light: + 1st-order diffracted light: -1st-order diffracted light = As 0: 1: 1, detection may be performed by the same photodetector as in FIGS. In this case, the same effect can be obtained by performing the following calculation.

  DVD

  CD

  Note that kt1, kt2, and kt3 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted. At this time, there are three RF signal light receiving parts, but there is no problem in practical use. Further, it is possible to reduce noise by connecting the light receiving unit m1 and the light receiving unit o1, and the light receiving unit m2 and the light receiving unit o2.

In the present embodiment, the number of light receiving units corresponding to the CD is increased compared to the first embodiment. However, the output signals of the DVD and the CD may be shared and output as shown in FIG.
The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of discs and does not depend on the focus error signal detection method. Alternatively, an astigmatism method or a knife edge method may be used.

  FIG. 17 shows the arrangement of the light receiving portions of the photodetector 10 of the optical pickup device according to the fifth embodiment. In the fourth embodiment, the hologram element 11 is used to defocus the light beam as an aberration. However, in this embodiment, a composite prism is used as shown in FIG. 10 to defocus the light beam by branching. That is, the light receiving part of the photodetector 10 is different, and the other configuration is the same as that of the fourth embodiment.

  In the present embodiment, a configuration different from that of the fourth embodiment will be described. Similarly to the fourth embodiment, the light beam reflected from the disk enters the composite prism 15 through the objective lens 2, the quarter-wave plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The composite prism has at least reflecting surfaces 15a, 15b, and 15c. The light beam incident on the composite prism 15 is reflected and transmitted by the reflecting surfaces 15 a and 15 b and reflected by the reflecting surface 15 c, and each light beam enters the photodetector 10.

First, the case of recording / reproducing a DVD will be described.
FIG. 17 is a diagram illustrating the relationship between the arrangement of the light receiving unit of the photodetector 10 and the light beam when a signal is recorded on and reproduced from the DVD in the fifth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the DVD is recorded / reproduced. The spots on the photodetector 10 are spots 1aa to 3ac, and 1, 2, and 3 in the symbols indicate the 0th-order diffracted light, the + 1st-order diffracted light, and the -1st-order diffracted light, respectively. , Ab, and ac are reflected light from the reflecting surface 15b, transmitted light from the reflecting surface 15a, and reflected light from the reflecting surface 15c, respectively.

  Specifically, the spot 1aa is the 0th-order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15b, the spot 2aa is the + 1st-order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15b, and the spot 3aa is the diffraction grating 9 The -1st order diffracted light and the reflected light of the reflecting surface 15b, the spot 1ab is the 0th order diffracted light of the diffraction grating 9 and the transmitted light of the reflecting surface 15a, and the spot 2ab is the + 1st order diffracted light of the diffraction grating 9 and the transmitted light of the reflecting surface 15a. , Spot 3ab is -1st order diffracted light of diffraction grating 9 and transmitted light of reflecting surface 15a, spot 1ac is 0th order diffracted light of diffraction grating 9 and reflected light of reflecting surface 15c, and spot 2ac is +1 next time of diffraction grating 9. The folded light and the reflected light of the reflecting surface 15c, and the spot 3ac indicate the -1st order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15c. The photodetector 10 is adjusted so that the spot 1aa is condensed. Here, the light quantity ratio of the spot a, the spot b, and the spot c incident on the photodetector 10 is 5: 1: 1.

  Here, the signals A1, B1, C1 obtained from the light receiving portions a1, b1, c1, d1, e1, f1, g1, h1, i1, j1, k1, l1, m1, n1, o1, p1 shown in FIG. , D1, E1, F1, G1, H1, I1, J1, K1, L1, M1, N1, O1, and P1 signals, the focus error signal (FES), tracking error signal (TES), and RF are calculated as follows. A signal (RF) is generated.

Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.
Since the tracking error detection method of the present embodiment and the tracking error signal detection method of Embodiment 1 are the same, the same effect as in Embodiment 1 can be obtained.

Next, a case where a CD is recorded / reproduced will be described.
FIG. 18 is a diagram showing the relationship between the arrangement of the light receiving portions of the photodetector and the light beam when signals are recorded on and reproduced from the CD in the fifth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the CD is recorded / reproduced.
The spots on the photodetector 10 are spots 1ba to 3bc, and 1, 2, and 3 in the symbols indicate 0th-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light of the diffraction grating 9, respectively. , Bb, and bc are reflected light from the reflecting surface 15b, transmitted light from the reflecting surface 15a, and reflected light from the reflecting surface 15c, respectively.

  Specifically, the spot 1ba is the 0th-order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15b, the spot 2ba is the + 1st-order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15b, and the spot 3ba is the diffraction grating 9 The -1st order diffracted light and the reflected light of the reflecting surface 15b, the spot 1bb is the 0th order diffracted light of the diffraction grating 9 and the transmitted light of the reflecting surface 15a, and the spot 2bb is the + 1st order diffracted light of the diffraction grating 9 and the transmitted light of the reflecting surface 15a. , Spot 3bb is the -1st order diffracted light of the diffraction grating 9 and the transmitted light of the reflecting surface 15a, spot 1bc is the 0th order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15c, and the spot 2bc is +1 next time of the diffraction grating 9. The folded light and the reflected light of the reflecting surface 15c, and the spot 3bc indicate the -1st order diffracted light of the diffraction grating 9 and the reflected light of the reflecting surface 15c.

17 and 18, it can be seen that the position of the spot 1aa when the DVD is recorded / reproduced is different from the position of the spot 1ba when the CD is recorded / reproduced. This is because the emission points of the DVD and CD of the two-wavelength laser are different, and such emission point shift is a problem when the DVD and CD are compatible with the two-wavelength laser.
Here, the signals A2, B2, and C2 obtained from the light receiving portions a2, b2, c2, d2, e2, f2, g2, h2, i2, j2, k2, l2, m2, n2, o2, and p2 shown in FIG. , D2, E2, F2, G2, H2, I2, J2, K2, L2, M2, N2, O2, P2, and using the following calculation, the focus error signal (FES), tracking error signal (TES), RF A signal (RF) is generated.

  Note that kt3 in the equation is a coefficient for preventing a DC offset from being generated in the tracking error signal when the objective lens moves. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.

The main difference between the present embodiment and the fourth embodiment is the arrangement of the light receiving parts. The light receiving unit of the present embodiment has substantially the same spot interval in the Rad direction of DVD and CD, whereas the light receiving unit of Example 4 has different spot intervals in the Rad direction of DVD and CD. This is because a long wavelength CD is more diffracted because the hologram element depends on the wavelength. However, since the tracking error detection method of the present embodiment and the tracking error signal detection method of the fourth embodiment are the same, the same effects as those of the first embodiment can be obtained. In addition, when using a hologram element, the diffraction angle (light receiving portion condensing position) changes slightly as the laser wavelength changes with temperature and laser output, but a composite prism is used as in this embodiment. It becomes possible to suppress it.
Further, in this embodiment, the reflected light from the reflecting surface 15b of the composite prism is detected as an RF signal. However, the present invention is not limited to this. For example, only the reflecting surfaces of the composite prism are 15a and 15c, and the light detection shown in FIG. You may detect with a container. In this case, the same effect can be obtained by performing the above-described (Expression 7) for a DVD and the above-described (Expression 8) for a CD.

  Note that kt1, kt2, and kt3 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted. At this time, there are three RF signal light receiving parts, but there is no problem in practical use. Further, it is possible to reduce noise by connecting the light receiving unit m1 and the light receiving unit o1, and the light receiving unit m2 and the light receiving unit o2.

  In the present embodiment, the number of light receiving units corresponding to the CD is increased compared to the first embodiment. However, the output signals of the DVD and the CD may be shared and output as shown in FIG.

  The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of discs and does not depend on the focus error signal detection method. For example, even in the spot size detection method as in the present embodiment, The astigmatism method or the knife edge method may be used. The optical system is not limited to that shown in FIG. 10. For example, an optical system in which the semiconductor laser 50 and the photodetector 10 are arranged in the same direction as shown in FIG. 11 may be used. In this way, the optical pickup device can be reduced in size.

FIG. 20 shows the arrangement of the light receiving portions of the photodetector 10 of the optical pickup device according to the sixth embodiment. The difference from the fourth embodiment is that the diffraction angle of the hologram element 11 and the light receiving portion of the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

In the present embodiment, a configuration different from that of the fourth embodiment will be described. Similarly to the fourth embodiment, the light beam reflected by the disk enters the hologram element 11 through the objective lens 2, the quarter wavelength plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The diffraction efficiency of the hologram element 11 is, for example, 0th order diffracted light: + 1st order diffracted light: -1st order diffracted light = 5: 0: 5, and defocus aberration is given to the −1st order diffracted light. For example, it is assumed that the -1st order diffracted light is given a defocus aberration that converges at a position farther from the collimating lens 51 than the 0th order diffracted light.
Here, FIG. 20 is a diagram showing the relationship between the arrangement of the light receiving portions of the photodetector 10 and the light beams when signals are recorded on and reproduced from the DVD in the sixth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the DVD is recorded / reproduced. The spots on the photodetector 10 are spots 1aa to 3ac, and 1, 2, and 3 in the symbols indicate the 0th-order diffracted light, the + 1st-order diffracted light, and the -1st-order diffracted light, respectively. , Ac indicate 0th-order diffracted light and -1st-order diffracted light of the hologram element 11, respectively. Specifically, the spot 1aa is the 0th-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, the spot 2aa is the + 1st-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, and the spot 3aa is diffracted The -1st order diffracted light of the grating 9 and the 0th order diffracted light of the hologram element 11, the spot 1ac is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light of the hologram element 11, and the spot 2ac is the + 1st order diffracted light of the diffraction grating 9 and the hologram The -1st order diffracted light of the element 11 and the spot 3ac indicate the -1st order diffracted light of the diffraction grating 9 and the -1st order diffracted light of the hologram element 11, respectively. The photodetector 10 is adjusted so that the spot 1aa and the spot 1ac are given substantially the same defocus.
Here, the signals A1, B1, C1, and D1 obtained from the light receiving portions a1, b1, c1, d1, e1, f1, g1, h1, i1, j1, k1, l1, m1, n1, and o1 shown in FIG. , E1, F1, G1, H1, I1, J1, K1, L1, M1, N1, and O1, and using the calculation of the above (Equation 7), the focus error signal (FES) and tracking error signal (TES) , An RF signal (RF) is generated.

Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.
Since the tracking error detection method of the present embodiment and the tracking error signal detection method of Embodiment 1 are the same, the same effect as in Embodiment 1 can be obtained.

Next, a case where a CD is recorded / reproduced will be described.
FIG. 21 is a diagram showing the relationship between the arrangement of the light receiving portions of the photodetector and the light beam when a signal is recorded on and reproduced from the CD in the sixth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the CD is recorded / reproduced. The spots on the photodetector 10 are spots 1ba to 3bc, and 1, 2, and 3 in the symbols indicate 0th-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light of the diffraction grating 9, respectively. , Bc indicate the 0th-order diffracted light and the −1st-order diffracted light of the hologram element 11, respectively. Specifically, the spot 1ba is the 0th-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, the spot 2ba is the + 1st-order diffracted light of the diffraction grating 9 and the 0th-order diffracted light of the hologram element 11, and the spot 3ba is diffracted The -1st order diffracted light of the grating 9 and the 0th order diffracted light of the hologram element 11 and the spot 1bc are the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light of the hologram element 11, and the spot 2bc is the + 1st order diffracted light and hologram of the diffraction grating 9 The -1st order diffracted light of the element 11 and the spot 3bc indicate the -1st order diffracted light of the diffraction grating 9 and the -1st order diffracted light of the hologram element 11, respectively.

20 and 21, it can be seen that the position of the spot 1aa when the DVD is recorded / reproduced is different from the position of the spot 1ba when the CD is recorded / reproduced. This is because the emission points of the DVD and CD of the two-wavelength laser are different, and such emission point shift is a problem when the DVD and CD are compatible with the two-wavelength laser.
Here, the signals A2, B2, C2, D2 obtained from the light receiving portions a2, b2, c2, d2, e2, f2, g2, h2, i2, j2, k2, l2, m2, n2, o2 shown in FIG. , E2, F2, G2, H2, I2, J2, K2, L2, M2, N2, and O2, and the focus error signal (FES) and tracking error signal (TES) by the above-described calculation (Equation 8). , An RF signal (RF) is generated.

  Note that kt3 in the equation is a coefficient for preventing a DC offset from being generated in the tracking error signal when the objective lens moves. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted. At this time, there are three RF signal light receiving parts, but there is no problem in practical use. Further, it is possible to reduce noise by connecting the light receiving unit m1 and the light receiving unit o1, and the light receiving unit m2 and the light receiving unit o2.

  In the case of Example 4, the focus error signal was detected using ± first-order diffracted light from the hologram element. On the other hand, in the case of the present embodiment, the focus error signal is detected using the 0th order diffracted light and the −1st order diffracted light of the hologram element. In the fourth embodiment, the focus error signal is detected using the + 1st order diffracted light of the hologram element. In the present embodiment, the tracking error signal is detected using the 0th order diffracted light. By adopting such a configuration, in addition to the effects of the fourth embodiment, the configuration can be made strong against the optical axis direction shift and the wavelength shift of the hologram element. Specifically, even if the wavelength is displaced, the spot 1aa (spot 1ba) does not move because it is the zero-order diffracted light of the hologram. For this reason, there is a feature that a stable tracking error signal can be obtained even if the wavelength is displaced. In addition, regarding the light receiving unit m1, the light receiving unit n1, and the light receiving unit o1 (the light receiving unit m2, the light receiving unit n2, and the light receiving unit o2) of the focus error signal receiving unit, the moving direction of the spot 1ac (spot 1bc) accompanying the wavelength displacement is There is no problem because the light receiving part m1, the light receiving part n1, and the light receiving part o1 (light receiving part m2, light receiving part n2, and light receiving part o2) are extended in the Rad direction. Since the tracking error detection method according to the present embodiment and the tracking error signal detection method according to the fourth embodiment are the same, the same effects as those of the first embodiment can be obtained. However, in the case of this embodiment, there is a problem that the focus does not match between the DVD and the CD from the viewpoint of detecting the focus error signal from the 0th-order diffracted light and the −1st-order diffracted light. For this, for example, the light receiving parts a1, b1, c1, d1, e1, f1, g1, h1 (light receiving parts a2, b2, c2, d2, e2, f2, g2, h2) and the light receiving parts m1, n1, This can be dealt with by optimizing the width of the light receiving portion in the Tan direction of o1 (light receiving portions m2, n2, o2). Further, the optical disc apparatus may be controlled by adding a predetermined offset.

  Furthermore, the diffraction efficiencies of the diffraction grating 9 and the hologram element 11 of this embodiment are not limited. For example, there is no problem even if + 1st order diffracted light from the hologram element is generated. Further, + 1st order diffracted light may be detected and used as a signal. In this embodiment, the focus error signal is detected from the 0th order diffracted light and the −1st order diffracted light. However, the present invention is not limited to this, and the focus error signal may be detected from the 0th order diffracted light and the + 1st order diffracted light. The CD focus error signal light receiving unit may be shared.

  In the present embodiment, the number of light receiving units corresponding to the CD is increased compared to the first embodiment. However, the output signals of the DVD and the CD may be shared and output as shown in FIG.

  The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of discs and does not depend on the focus error signal detection method. For example, even in the spot size detection method as in the present embodiment, The astigmatism method or the knife edge method may be used.

  FIG. 22 shows the arrangement of the light receiving portions of the photodetector 10 of the optical pickup device according to the seventh embodiment. The difference from the fourth embodiment is that the pattern of the hologram element 11 and the light receiving portion of the photodetector 10 are different, and the other configuration is the same as that of the first embodiment.

  In the present embodiment, a configuration different from that of the fourth embodiment will be described. Similarly to the fourth embodiment, the light beam reflected by the disk enters the hologram element 11 through the objective lens 2, the quarter wavelength plate 56, the rising mirror 55, the collimator lens 51, and the beam splitter 52. The hologram element is divided into a plurality of regions, and at the same time, the hologram element is an optical element having a characteristic that gives a predetermined defocus aberration to the outgoing diffracted light. The light beams separated by the hologram element 11 signal in different directions for each region and enter the photodetector 10. A plurality of light receiving portions are formed on the photodetector 10, and each light receiving portion is irradiated with a light beam divided by the hologram element 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.

  FIG. 13 shows the shape of the hologram element 11. The solid line indicates the boundary line of the region, and the alternate long and short dash line indicates the outer shape of the DVD light beam. The hologram element 11 is divided into two regions, a region I and a region II, in the Tan direction by a dividing line passing through the approximate center of the DVD and CD light beams. Although the external shape of the CD light beam is not shown in FIG. 13, the light emission point of the DVD of the two-wavelength laser is different from that of the CD, so the CD light beam is shifted in the Rad direction with respect to the DVD. Further, the opposite defocus aberrations are given to the ± first-order diffracted lights of the hologram element 11. For example, + 1st order diffracted light converges at a position closer to the 0th order diffracted light than the collimating lens 51, and −1st order diffracted light has a defocus aberration that converges at a position farther from the collimating lens 51 than the 0th order diffracted light. Suppose that

First, the case of recording / reproducing a DVD will be described.
FIG. 22 is a diagram illustrating the relationship between the arrangement of the light receiving unit of the photodetector 10 and the light beam when a signal is recorded on and reproduced from the DVD in the sixth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the DVD is recorded / reproduced. The spots on the photodetector 10 are spots 40a to 60e, and 40, 50, and 60 in the symbols indicate the 0th-order diffracted light, the + 1st-order diffracted light, and the -1st-order diffracted light, respectively. , B, c, d, and e are the 0th order diffracted light of region I and region II of the hologram element 11, the + 1st order diffracted light of region I, the −1st order diffracted light of region I, the + 1st order diffracted light of region II, and − of the region II, respectively. 1st order diffracted light is shown. Specifically, the spot 40a is the 0th-order diffracted light of the diffraction grating 9 and the region I of the hologram element 11, and the 0th-order diffracted light of the region II, and the spot 50a is the + 1st-order diffracted light of the diffraction grating 9 and the region I of the hologram element 11. The second order diffracted light of the region II, the spot 60a is the −1st order diffracted light of the diffraction grating 9 and the region I of the hologram element 11, and the zeroth order diffracted light of the region II, the spot 40b is the 0th order diffracted light of the diffraction grating 9 and the hologram element 11. The + 1st order diffracted light of the region I, the spot 50 b is the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the region I of the hologram element 11, and the spot 60 b is the −1st order diffracted light of the diffraction grating 9 and the region I of the hologram element 11. The + 1st order diffracted light and the spot 40c are the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light in the region I of the hologram element 11 and the spot 50c are the diffraction grating 9 The + 1st order diffracted light and the −1st order diffracted light in the region I of the hologram element 11, the spot 60 c is the −1st order diffracted light of the diffraction grating 9 and the −1st order diffracted light in the region I of the hologram element 11, and the spot 40 d is 0% of the diffraction grating 9. The first-order diffracted light and the + 1st-order diffracted light of the region II of the hologram element 11 and the spot 50d are the + 1st-order diffracted light of the diffraction grating 9 and the + 1st-order diffracted light of the region II of the hologram element 11 and the spot 60d The + 1st order diffracted light and the spot 40e in the region II of the hologram element 11 are the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light and the spot 50e in the region II of the hologram element 11 are the + 1st order diffracted light and the hologram element 11 of the diffraction grating 9. The -1st order diffracted light in the region II of FIG. 1 is a spot 60e, which is the -1st order diffracted light of the diffraction grating 9 and the -1st order diffracted light in the region II of the hologram element 11 Shows. The photodetector 10 is adjusted so that the spots 40c and 40e are condensed.

  Here, the light receiving portions na, nb, nc, nd, ne, nf, ng, nh, nad, neh, nia, nib, nic, nid, niad, nja, njb, njc, njd, njad, uc shown in FIG. , Ud, wc, wd, signals obtained from p1, NA, NB, NC, ND, NE, NF, NG, NH, NAD, NEH, NIA, NIB, NIC, NID, NIAD, NJA, NJB, NJC, NJD , NJAD, UC, UD, WC, WD, and P1 signals are used to generate a focus error signal (FES), tracking error signal (TES), and RF signal (RF) by the following calculation.

Note that kt1 and kt2 in the equation are coefficients that prevent a DC offset from being generated in the tracking error signal when the objective lens moves. Also, φ in the equation indicates the phase difference of each signal in the DPD method. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.
Since the tracking error detection method of the present embodiment and the tracking error signal detection method of Embodiment 3 are the same, the same effect as in Embodiment 3 can be obtained.

Next, a case where a CD is recorded / reproduced will be described.
FIG. 23 is a diagram showing the relationship between the arrangement of the light receiving portions of the photodetector 10 and the light beams when signals are recorded on and reproduced from the CD in the sixth embodiment. The solid line in the figure indicates the light receiving portion, and the hatched area indicates the light beam when the DVD is recorded / reproduced.

  Note that the spots on the photodetector 10 are spots 70a to 90e, and 70, 80, and 90 in the symbols indicate 0th-order diffracted light, + 1st-order diffracted light, and -1st-order diffracted light, respectively, of the diffraction grating 9, and a , B, c, d, and e are the 0th order diffracted light of region I and region II of the hologram element 11, the + 1st order diffracted light of region I, the −1st order diffracted light of region I, the + 1st order diffracted light of region II, and − of the region II, respectively. 1st order diffracted light is shown. Specifically, the spot 70a is the 0th-order diffracted light of the diffraction grating 9 and the region I of the hologram element 11, and the 0th-order diffracted light of the region II, and the spot 80a is the + first-order diffracted light of the diffraction grating 9 and the region I of the hologram element 11. The second order diffracted light of the region II, the spot 90a is the −1st order diffracted light of the diffraction grating 9 and the region I of the hologram element 11, and the zeroth order diffracted light of the region II, the spot 70b is the zeroth order diffracted light of the diffraction grating 9 and the hologram element 11. The + 1st order diffracted light of the region I, the spot 80b is the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light of the region I of the hologram element 11, and the spot 90b is the −1st order diffracted light of the diffraction grating 9 and the region I of the hologram element 11. The + 1st order diffracted light, the spot 70c is the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light in the region I of the hologram element 11, and the spot 80c is the diffraction grating 9 The + 1st order diffracted light and the −1st order diffracted light in the region I of the hologram element 11, the spot 90 c are the −1st order diffracted light in the diffraction grating 9 and the −1st order diffracted light in the region I of the hologram element 11, and the spot 70 d is 0% of the diffraction grating 9. The first order diffracted light and the + 1st order diffracted light in the region II of the hologram element 11 and the spot 80d are the + 1st order diffracted light of the diffraction grating 9 and the + 1st order diffracted light in the area II of the hologram element 11 and the spot 90d are the −1st order diffracted light of the diffraction grating 9 and The + 1st order diffracted light and the spot 70e in the region II of the hologram element 11 are the 0th order diffracted light of the diffraction grating 9 and the −1st order diffracted light and the spot 80e in the region II of the hologram element 11 are the + 1st order diffracted light and the hologram element 11 of the diffraction grating 9. The -1st order diffracted light in the region II of FIG. 2A is the spot 90e. Shows.

From FIG. 22 and FIG. 23, it can be seen that the position of the spot 40a when the DVD is recorded / reproduced is different from the position of the spot 70a when the CD is recorded / reproduced. This is because the emission points of the DVD and CD of the two-wavelength laser are different, and such emission point shift is a problem when the DVD and CD are compatible with the two-wavelength laser.
Here, the light-receiving portions na, nb, nc, nd, ne, nf, ng, nh, nad, neh, nia, nib, nic, nid, niad, nja, njb, njc, njd, njad, ud shown in FIG. , Ue, wd, we, p2 obtained signals NA, NB, NC, ND, NE, NF, NG, NH, NAD, NEH, NIA, NIB, NIC, NID, NIAD, NJA, NJB, NJC, NJD , NJAD, UD, UE, WD, WE, and P2 signals are used to generate a focus error signal (FES), tracking error signal (TES), and RF signal (RF) by the following calculation.

Note that kt3 in the equation is a coefficient for preventing a DC offset from being generated in the tracking error signal when the objective lens moves. Here, the focus error detection method is a spot size detection method, and since this method is publicly known, description thereof is omitted.
In this embodiment, the focus aberration given by the hologram element is absorbed by the diffracted light on one side, and the spot diameter of the other diffracted light on the photodetector 10 is increased. Although the hologram element 11 is vertically divided into two, the tracking error signal detection is the same as that in the fourth embodiment (CD) in consideration of the spot division method and calculation, so that the same effect as in the fourth embodiment is obtained. be able to.

  Compared with the third embodiment, the present embodiment realizes DVD-CD compatibility by sharing the light-receiving portions nad, neh, niad, and njad for the DVD and the CD. However, in the present embodiment, the compatibility between DVD and CD has been described. However, for example, DVD and BD may be used, or compatibility with other optical disks may be used. Needless to say, in this embodiment, the same effect can be obtained even if the hologram element is changed to a composite prism from the viewpoint of providing defocus. The diffraction efficiencies of the diffraction grating 9 and the hologram element of this embodiment are not limited, and similar effects can be obtained even if they are different from those of this embodiment. In this embodiment, the RD-direction dividing lines of the DVD and CD light beams coincide on the light receiving portions nc, nd, nf, ng, nib, nic, njb, and njc. However, the present invention is not limited to this. The same effect can be obtained even if detection is performed separately without aligning the axes.

  The present embodiment is characterized in that the tracking error signal detection method is changed for a plurality of discs and does not depend on the focus error signal detection method. For example, even in the spot size detection method as in the present embodiment, The astigmatism method or the knife edge method may be used.

  In this embodiment, the focus aberration given by the hologram element is absorbed by the diffracted light on one side, and the spot diameter of the other diffracted light on the photodetector 10 is increased. For this reason, in this embodiment, the focus aberration given by the hologram element is absorbed by the diffracted light on one side, and the spot diameter of the other diffracted light on the photodetector 10 is increased. Although the hologram element 11 is divided into two parts in the vertical direction, the tracking error signal detection is the same as that of the fourth embodiment in consideration of the spot light receiving method and calculation, so that the same effect as that of the fourth embodiment can be obtained. it can. Further, in Example 4, from the viewpoint of detecting the focus error signal by the spot size method using the ± first-order diffracted light of the hologram element 11, the effective diameter of the spot on the photodetector could not be increased. In this embodiment, since the focus error signal is detected by converging the −1st order diffracted light of the hologram element, the amount of defocus aberration of the hologram element can be greatly given to the configuration of the embodiment 4. It is also possible to increase the effective diameter of the + 1st order diffracted light on the photodetector. For this reason, by increasing the effective diameter of the + 1st order diffracted light, it is possible to make it more resistant to positional deviation of the light receiving unit.

  Further, with respect to the focus error signal, a double knife edge in which two knife edge type light receiving parts are arranged as in the present embodiment can be configured to be resistant to positional deviation of the light receiving part. By adopting such a configuration, it is possible to provide a configuration that is resistant to the positional deviation of the photodetector. Further, in the present embodiment, it is needless to say that the same effect can be obtained even if the hologram element is changed to a composite prism from the viewpoint of providing defocus. In this case, the hologram element is a normal diffraction grating having two or more divisions. The diffraction efficiencies of the diffraction grating 9 and the hologram element of this embodiment are not limited, and similar effects can be obtained even if they are different from those of this embodiment. Further, the diffraction grating 9 is not limited to the diffraction grating of the present embodiment, and the same applies to diffraction gratings such as those disclosed in Japanese Patent Application Laid-Open Nos. 2008-176899, 2007-234175, and 2005-122869. The effect is obtained.

In the eighth embodiment, an optical reproducing apparatus equipped with the optical pickup device 170 will be described.
FIG. 24 is a block diagram illustrating an optical reproducing device according to the seventh embodiment. The optical pickup device 170 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 170, and laser light is emitted from the semiconductor laser with a predetermined light amount in response to a reproduction command. The laser lighting circuit 177 can be incorporated in the optical pickup device 170.

  A signal output from the photodetector 10 in the optical pickup device 170 is sent to the servo signal generation circuit 174 and the information signal reproduction circuit 175. The servo signal generation circuit 174 generates servo signals such as a focus error signal, a tracking error signal, and a tilt control signal based on the signal from the photodetector 10, and based on this generates an optical pickup device 170 via an actuator drive circuit 173. The actuator is driven to control the position of the objective lens. 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, etc., and controls the rotation of the spindle motor 180 that rotates the optical disc 100, the access direction and the 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 170, and the like are performed. Also, for example, the output signal of the optical pickup device can be changed based on a signal from a control circuit corresponding to the optical disk to be reproduced.

In the ninth embodiment, an optical recording / reproducing apparatus equipped with the optical pickup device 170 will be described.
FIG. 25 is a block diagram showing an optical recording / reproducing apparatus in the eighth embodiment. 24 is different from the optical information recording / reproducing apparatus described in FIG. 24 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. The laser lighting circuit 177 is controlled based on the above, and a function for 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. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
Thus, although the Example which added the change to the above-mentioned Example can be considered, all are in the category of this invention.

  2: objective lens, 5: actuator, 9: diffraction grating, 10: photodetector, 11: hologram element, 15: compound prism, 50: semiconductor laser, 51: collimating lens, 52: beam splitter, 55: rising mirror 56: 1/4 wavelength plate, 170: optical pickup device, 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, 180: spindle motor.

Claims (22)

An optical pickup device,
A laser light source for generating laser light;
An objective lens that receives the laser beam generated by the laser light source and irradiates the optical disc with the laser beam;
An actuator for displacing a relative position of the objective lens with respect to the optical disc;
A light detection unit that detects the laser light reflected from the optical disc and converts it into an electrical signal;
An optical pickup device characterized in that the signal output for tracking error signals for at least two types of recording or rewritable optical discs using substantially the same wavelength of the laser beam and the numerical aperture of the objective lens is different. An optical pickup device,
A laser light source for generating laser light;
A diffraction grating that receives the laser beam generated by the laser light source and splits the laser beam into a plurality of beams;
An objective lens for irradiating the optical disc with a plurality of beams of the laser beam branched by the diffraction grating;
An actuator for displacing a relative position of the objective lens with respect to the optical disc;
A light detection unit that detects the laser light reflected from the optical disc and converts it into an electrical signal;
For at least two types of recordable or rewritable optical discs using substantially the same wavelength of the laser beam and the numerical aperture of the objective lens,
For at least one recording type or rewritable optical disc, an electrical signal obtained by detecting reflected light from the optical disc of a plurality of light beams irradiated on the optical disc with the photodetector is used for a tracking error signal. Signal output as
For other types of recordable or rewritable optical discs, the electric light obtained by detecting the reflected light from the optical disc of one light beam included in a plurality of light beams applied to the optical disc with the photodetector. An optical pickup device that outputs a signal for a tracking error signal. An optical pickup device,
A laser light source for generating laser light;
A diffraction grating that receives the laser beam generated by the laser light source and splits the laser beam into a plurality of beams;
An objective lens for irradiating the optical disc with a plurality of beams of the laser beam branched by the diffraction grating;
An actuator for displacing a relative position of the objective lens with respect to the optical disc;
A light detection unit that detects the laser light reflected from the optical disc and converts it into an electrical signal;
For at least two types of recordable or rewritable optical discs using substantially the same wavelength of the laser beam and the numerical aperture of the objective lens,
In the case of an optical disc having the longest track groove period having the recording track, an electric signal obtained by detecting reflected light from the optical disc of a plurality of light beams irradiated on the optical disc with the photodetector. Output signal for tracking error signal,
For an optical disc having the smallest track groove period having the recording track, the reflected light from the optical disc of one light beam included in a plurality of light beams irradiated on the optical disc is detected by the photodetector. An optical pickup device that outputs an electrical signal as a tracking error signal. An optical pickup device,
A laser light source for generating laser light;
A diffraction grating that receives the laser beam generated by the laser light source and splits the laser beam into a plurality of beams;
An objective lens for irradiating the optical disc with a plurality of beams of the laser beam branched by the diffraction grating;
An actuator for displacing a relative position of the objective lens with respect to the optical disc;
A light detection unit that detects the laser light reflected from the optical disc and converts it into an electrical signal;
For at least two types of recordable or rewritable optical discs using substantially the same wavelength of the laser beam and the numerical aperture of the objective lens,
For an optical disc of a type corresponding to only a single-layer disc, an electrical signal obtained by detecting reflected light from the optical disc of a plurality of light beams irradiated on the optical disc with the photodetector is used for a tracking error signal. Signal output,
For an optical disc of a type that also supports a multi-layer disc, an electrical signal obtained by detecting the reflected light from the optical disc of one light beam included in a plurality of light beams applied to the optical disc with the photodetector. An optical pickup device that outputs a signal for a tracking error signal. The optical pickup device according to claim 2,
An optical pickup device comprising an optical branching element for branching a light beam reflected from the optical disk. The optical pickup device according to claim 5,
The light branching element is a hologram element;
The hologram element is
An optical pickup device that branches a light beam into at least zero-order diffracted light and positive / negative or positive / negative order diffracted light and gives defocus aberration to positive / negative or positive / negative order diffracted light. The optical pickup device according to claim 6,
The light detection unit is
An optical pickup device that generates a reproduction signal from zero-order diffracted light of the hologram element. The optical pickup device according to claim 5,
The optical branching element is:
An optical pickup device which is a composite prism having at least two reflecting surfaces. The optical pickup device according to claim 6 or 8,
The focus error signal detection method is a spot size detection method,
Of the electrical signals obtained by detection with the photodetector,
An optical pickup device characterized by sharing an output signal for a focus error signal and an output signal for the tracking error signal. The optical pickup device according to claim 6,
The focus error signal detection method is a knife edge method,
An electrical signal detected from either the positive or negative order diffracted light in the hologram element by the photodetector is output for a focus error signal,
An optical pickup device characterized in that an electrical signal detected from the remaining diffracted light in the hologram element is output for the tracking error signal by the photodetector. The optical pickup device according to claim 10,
The hologram element is
An optical pickup device, wherein the optical pickup device is divided into at least two by a dividing line passing through a substantially center of a light beam on the hologram element and substantially parallel to a radial direction of the optical disc. The optical pickup device according to claim 1,
The optical pickup apparatus, wherein the tracking error signal is a signal generated from a signal obtained by detecting the diffracted light by the track groove of the optical disc by the photodetector. The optical pickup device according to claim 1,
An optical pickup device, wherein an output signal for a tracking error signal is switched in accordance with information on a type of an optical disc recorded / reproduced by an optical disc device on which the optical pickup device is mounted. An optical pickup device,
A laser light source for generating laser light;
An objective lens that receives the laser beam generated by the laser light source and irradiates the optical disc with the laser beam;
An actuator for displacing a relative position of the objective lens with respect to the optical disc;
A light detection unit that detects the laser light reflected from the optical disc, converts the laser light into an electrical signal, and outputs the electrical signal;
The optical detection unit switches and outputs a signal for generating a tracking error signal by the optical disc device according to information on the type of the optical disc being recorded / reproduced by the optical disc device on which the optical pickup device is mounted. A characteristic optical pickup device. The optical pickup device according to claim 2,
The photodetector is
A light receiving unit output for detecting zero-order diffracted light in the diffraction grating of a plurality of light beams irradiated on the optical disc;
A light receiving unit output for detecting an interference region of zero-order diffracted light and ± first-order diffracted light in the diffraction grating diffracted by a track groove of one optical beam included in the plurality of optical beams irradiated on the optical disc, An optical pickup device that switches an output signal for a tracking error signal according to information on a type of the optical disc. The optical pickup device according to claim 2,
The photodetector is
A light receiving unit output for detecting ± first-order diffracted light in the diffraction grating of a plurality of light beams irradiated on the optical disc;
According to information on the type of the optical disk, the light receiving unit output of the photodetector for detecting the 0th-order diffracted light diffracted by the track groove of the optical disk of one light beam included in the plurality of light beams applied to the optical disk An optical pickup device that switches an output signal for a tracking error signal. The optical pickup device according to claim 1,
When DVD-RAMII was recorded / reproduced on the optical disk device equipped with the optical pickup device, the light reflected from the optical disk was detected by the photodetector. Output electrical signal for tracking error signal,
When a DVD-R is recorded / reproduced, an electrical signal obtained by detecting the reflected light from the optical disc of one optical beam included in a plurality of optical beams irradiated on the optical disc by the photodetector is used as a tracking error. An optical pickup device that outputs a signal for signal use. The optical pickup device according to claim 1,
2. The optical pickup device according to claim 1, wherein the laser light source selects and emits one of light beams having at least two wavelengths including a first wavelength and a second wavelength. The optical pickup device according to claim 9, wherein
The laser light source is a laser light source that selects and emits one of light beams having at least two wavelengths including a first wavelength and a second wavelength,
A light receiving unit for generating a focus error signal irradiated with the light beam of the first wavelength, which the photodetector has, is recorded on the optical disc irradiated with the light beam of the second wavelength. An optical pickup device which is a light receiving unit for generating a reproduction signal of an information signal. The optical pickup device according to claim 18 or 19,
The first wavelength is a wavelength of about 650 nm corresponding to DVD,
The second wavelength is a wavelength of approximately 785 nm corresponding to CD,
The distance in the radial direction of the optical disk of at least three spots branched from the diffraction grating when recording and reproducing information signals on the DVD is approximately half of the track groove period of the DVD-RAMII. An optical pickup device. The optical pickup device according to claim 15, wherein
The first wavelength is a wavelength of about 650 nm corresponding to DVD,
The second wavelength is a wavelength of approximately 785 nm corresponding to CD,
The distance in the radial direction of the optical disc of at least three spots branched from the diffraction grating when recording / reproducing information signals with respect to the CD is substantially half of the track groove period of the CD-R. An optical pickup device. An optical disk device,
A laser light source for generating laser light;
An objective lens that receives the laser beam generated by the laser light source and irradiates the optical disc with the laser beam;
An actuator for displacing a relative position of the objective lens with respect to the optical disc;
The laser beam reflected from the optical disc is detected, converted into an electrical signal and output, and the optical disc device outputs a signal for a tracking error signal according to information on the type of optical disc that is being recorded / reproduced by the optical disc device. An optical pickup device for switching between
A laser lighting circuit for driving the laser light source;
A tracking error signal for controlling the relative position in the radial direction of the objective lens with respect to the track on the optical disk and a focus error signal for controlling the relative position in the vertical direction from the electrical signal generated by the light detection unit. A servo signal generator to generate;
An optical disc apparatus comprising: an information signal reproducing circuit for reproducing an information signal recorded on the optical disc from the electrical signal generated by the photodetector.

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