JP4437806B2 - Optical integrated unit and optical pickup device including the same - Google Patents

Description

  The present invention relates to an optical pickup that divides reflected light from an optical disk into multiple parts by an optical splitting unit and generates an information signal and various error signals, and an optical integrated unit thereof, and particularly generates an information signal and various error signals. The present invention relates to an optical integrated unit that can secure a sufficient amount of luminous flux used for the purpose and an optical pickup device including the same.

  In recent years, it has been required to increase the recording density of an optical disc as the amount of information increases. Increasing the recording density of an optical disc has been performed by increasing the linear recording density in the information recording layer of the optical disc or by reducing the track pitch. In an optical pickup device that records and reproduces an optical disc with a high recording density as described above, it is necessary to reduce the beam diameter of the light beam focused on the information recording layer of the optical disc.

  As a method of reducing the beam diameter, it is conceivable to increase the numerical aperture (NA) of an objective lens used as a condensing optical system by the optical pickup device. It is also conceivable to shorten the wavelength of the light beam used by the optical pickup device.

  Regarding the shortening of the wavelength of the light beam, a blue-violet semiconductor laser having a wavelength of 405 nm has been put into practical use. It is possible to replace the light source from the infrared semiconductor laser having a wavelength of 780 nm generally used in CD to the red semiconductor laser having a wavelength of 650 nm generally used in DVD and further to the blue-violet semiconductor laser having a wavelength of 405 nm. It is coming.

  As a method for increasing the numerical aperture of an objective lens, a method of forming an objective lens by using two lenses (two group lenses) has been proposed. At present, an objective lens having a high numerical aperture with a NA of about 0.85 is being put into practical use by improving lens design technology and lens manufacturing technology.

  In addition, there is a multilayer optical disc formed by stacking information recording layers so that the recording information can be increased in density in the thickness direction of the optical disc. For example, DVDs (Digital Versatile Discs) and BDs (Blu-ray Discs) having two information recording layers have already been commercialized.

  However, there are the following problems in increasing the recording density of the optical disc as described above.

  Generally, in an optical disc, the information recording layer is covered with a cover glass in order to protect the information recording layer from dust and scratches. The light beam that has passed through the objective lens of the optical pickup device passes through the cover glass, and is condensed on the information recording layer underneath to be focused.

  Here, when the light beam passes through the cover glass, spherical aberration (SA) occurs. The spherical aberration SA is expressed by the following equation.

SA∝ (d / λ) · NA ⁴ (1)
Where d is the thickness of the cover glass, λ is the wavelength of the light beam, and NA is the numerical aperture of the objective lens.

  As shown in Equation (1), the spherical aberration SA is proportional to the thickness d of the cover glass and the fourth power of the NA of the objective lens, and inversely proportional to the wavelength λ of the light source. Usually, the objective lens is designed to cancel out this spherical aberration. Therefore, the spherical aberration of the light beam that has passed through the objective lens and the cover glass is sufficiently small.

  However, if the thickness d of the cover glass deviates from a predetermined value, a new spherical aberration is generated in the light beam condensed on the information recording layer. As a result, the beam diameter becomes large, and there arises a problem that information cannot be read and written correctly.

  Assuming that the thickness error of the cover glass is Δd and the error of the spherical aberration is ΔSA, from equation (1), ΔSA increases as Δd increases, and information on the optical disk cannot be read and written correctly. I understand. Furthermore, it can be seen that the shorter the wavelength λ of the light source, the larger the spherical aberration SA.

  Since the NA of the objective lens of the optical pickup used for DVD recording / reproduction is as small as about 0.6, even if the cover glass thickness error Δd becomes somewhat large, the influence on the spherical aberration error ΔSA is small. Therefore, in a DVD apparatus using a conventional optical pickup apparatus having a numerical aperture NA of about 0.6, the error ΔSA of spherical aberration caused by the thickness error Δd of the DVD cover glass is small, and the light is condensed on each information recording layer. The light beam to be collected can be condensed sufficiently small.

  However, even if the cover glass thickness error Δd is equal, the larger the NA, the larger the spherical aberration SA. For example, when NA = 0.85, the spherical aberration SA is about 4 times as large as NA = 0.6. Furthermore, even when the thickness error Δd of the cover glass is the same, a larger spherical aberration SA occurs as the wavelength becomes shorter. For example, compared with λ = 650 nm, the spherical aberration SA is about 1.6 times larger at λ = 405 nm. In a BD that uses a short wavelength light source and a high NA objective lens, spherical aberration about 6.4 times that of DVD occurs.

  Further, in the optical disc on which the multilayer information recording layer is formed, the thickness from the surface of the optical disc (cover glass surface) to each information recording layer is different. For this reason, the spherical aberration that occurs when the light beam passes through the cover glass of the optical disk differs depending on each information recording layer. For example, the difference in spherical aberration (error ΔSA) that occurs between adjacent information recording layers is proportional to the interlayer distance t (corresponding to d) between the adjacent information recording layers from Equation (1).

  However, even when the interlayer distance t between adjacent information recording layers is equal, a larger spherical aberration difference (error ΔSA) occurs as the NA of the objective lens of the optical pickup device increases. For example, when NA = 0.85, the spherical aberration difference is about 4 times that of NA = 0.6. Therefore, from the above equation (1), it can be seen that the higher the NA, such as NA = 0.85, the greater the difference in spherical aberration of each information recording layer.

  As described above, in the high NA objective lens, the influence of the spherical aberration error cannot be ignored, and there arises a problem that the information reading accuracy is lowered. Therefore, in order to realize a high recording density using an objective lens with a high NA, it is necessary to correct spherical aberration.

  Here, Patent Document 1 discloses a technique for correcting spherical aberration. The optical pickup described in Patent Document 1 separates a return light beam reflected from an optical disk by a hologram element. At that time, the light beam in the return path is divided into a first light beam separated from a portion near the optical axis of the light beam and a second light beam separated from a portion near the outer periphery of the light beam. To separate. Then, spherical aberration is detected by utilizing the fact that the first light beam and the second light beam have different condensing positions, and the spherical aberration is corrected based on the detection result. Hereinafter, the optical pickup described in Patent Document 1 will be described in detail with reference to the drawings.

  FIG. 14 is a cross-sectional view illustrating a schematic configuration of the optical pickup described in Patent Document 1. In FIG. As shown in the figure, the optical pickup device 140 includes an optical integrated unit 101, a collimator lens 102, and an objective lens 103. The optical disc 104 includes a substrate 104a, a cover layer 104b through which a light beam is transmitted, and a recording layer 104c formed at the boundary between the substrate 104a and the cover layer 104b.

  FIG. 15 is an enlarged cross-sectional view showing the optical integrated unit 101. FIG. 15 is a view as seen from the y direction orthogonal to the illustrated optical axis direction (z direction). As shown in the figure, the optical integrated unit 101 includes a semiconductor laser 111 (light source), a light receiving element 112, a polarizing beam splitter 114 (light guiding means) including a polarizing beam splitter surface (PBS surface) 114a and a reflecting mirror 114b. ), A polarization diffraction element 115 (diffractive means), a quarter-wave plate 116, and a package 117. The polarization diffraction element 115 includes a polarization hologram element 131 and a polarization hologram element 132.

  The light beam 120 emitted from the semiconductor laser 111 mounted on the optical integrated unit 101 is collimated by the collimator lens 102 and then condensed on the optical disc 104 via the objective lens 103. Then, the light beam (returned light) reflected from the optical disk 104 passes through the objective lens 103 and the collimator lens 102 again and is received on the light receiving element 112 mounted on the optical integrated unit 101.

  Here, the polarization hologram element 131 is formed with a hologram pattern for generating three beams for detecting a tracking error signal (TES). The light beam 120 emitted from the semiconductor laser 111 is diffracted by the polarization hologram element 131 to become three beams 122 (main beam and two sub beams) for detecting a tracking error signal (TES). Emanates from.

  The polarization hologram element 132 is formed with a hologram pattern for separating the return light. The return light that has entered the polarization hologram element 132 is separated into zero-order diffracted light (non-diffracted light) 122 and + 1st-order diffracted light (diffracted light) 123 and is emitted. The separated return light (0th order diffracted light and + 1st order diffracted light) enters the polarization beam splitter 114, is reflected by the PBS surface 114a, is further reflected by the reflection mirror 114b, and exits from the polarization beam splitter 114. The return light emitted from the polarization beam splitter 114 is received by the light receiving element 112. Hereinafter, the hologram pattern formed on the polarization hologram element 132 and the relationship between the hologram pattern and the light receiving element 112 will be described.

  FIG. 16 is a plan view showing a hologram pattern formed on the polarization hologram element 132. As shown in the figure, the hologram pattern of the polarization hologram element 132 is composed of three regions 132a, 132b and 132c. Specifically, one semicircular region 132c divided into two by a straight line including the optical axis and extending in the radial direction, an inner peripheral region 132a in which the other semicircular region is further divided by an arc-shaped boundary line D101, and This is the outer peripheral region 132b.

  FIG. 17 is a schematic diagram showing the hologram pattern and the light receiving element 112 formed on the polarization hologram element 132. As shown in the figure, the light receiving element 112 includes 14 light receiving portions 112a to 112n.

  Three beams of zero-order diffracted light (non-diffracted light) 122 are received by the light receiving units 112a to 112h. Further, the + 1st order diffracted light 123 is received by the light receiving portions 112i to 112n. More specifically, the + 1st order diffracted light 123 diffracted in the region 132a is received by the light receiving units 112i to 112j, and the + 1st order diffracted light 123 diffracted in the region 132b is received by the light receiving units 112k to 112l and diffracted in the region 132c + 1. The folded light 123 is received by the light receiving portions 112m to 112m.

  The servo signal is generated as follows. The output signals of the light receiving units 112a to 112n are represented as Sa to Sn.

The information signal (RF) is detected using the non-diffracted light 122. That is, the information signal (RF) is
RF = Sa + Sb + Sc + Sd
Given by.

  The tracking error signal (TES1) by the DPD method (phase difference method) is detected by performing a phase comparison of Sa to Sd.

The tracking error signal (TES2) by the DPP method is
TES2 = {(Sa + Sb)-(Sc + Sd)}
−α {(Se−Sf) + (Sg−Sh)}
Given by. Here, α is set to an optimum coefficient for canceling offset due to objective lens shift or optical disc tilt.

The focus error signal (FES) is detected using a double knife edge method. That is, FES is
FES = (Sm−Sn) − {(Sk + Si) − (Sl + Sj)}
Given by.

The spherical aberration error signal (SAES) is detected using a detection signal from the light beam separated into the inner and outer circumferences. That is, SAES is
SAES = (Sk−Sl) −β (Si−Sj)
Given by. Here, β is set to an optimum coefficient for canceling the SAES offset.

  18A and 18B are diagrams for explaining the shape of the light beam on the light receiving element 112 in a state where a spherical aberration error has occurred and no defocus has occurred. That is, due to the influence of the thickness error of the cover layer 104 b of the optical disc 104, spherical aberration is generated in the focused beam of the objective lens 103, and the optical disc 4 is located at the focal point of the objective lens 3.

  As shown in FIGS. 18A and 18B, since spherical aberration remains, the inner peripheral side beam (light beam diffracted in the region 132a) and the outer peripheral side beam (light beam diffracted in the region 132b) Is larger in the opposite direction to the dividing line. This is because the generation direction of spherical aberration (sign of thickness error) is different between FIGS. 18 (a) and 18 (b). As shown in the SAES calculation formula, in the state shown in FIGS. 18A and 18B, it can be seen that SAES shows large positive and negative values, respectively.

  As described above, Patent Document 1 discloses an optical integrated module for BD in consideration of correction of a spherical aberration error of an optical disc.

  In addition to the recent demand for higher recording density of optical discs, it is strongly desired to reduce the size and weight of optical pickup devices in order to use optical discs in mobile applications. Patent Document 2 describes an optical integrated unit technology that meets the demands for reducing the size and weight of an optical pickup device.

  FIG. 19A is a cross-sectional view showing a schematic configuration of the optical integrated unit described in Patent Document 2. FIG. As shown in the figure, the light emitted from the light emitting element 144 passes through the composite diffraction element (hologram element) 143 and is condensed on the information recording surface of the optical disc 141 by the objective lens 142. The direction of the information track on the optical disc 141 is a direction perpendicular to the paper surface. The reflected light from the optical disk 141 passes through the objective lens 142 and then converges again toward the vicinity of the light emitting element 144 and enters the composite diffraction element 143. The light incident on the composite diffraction element 143 is separated into + 1st order, 0th order, and −1st order diffracted light. Of the separated light beams, + 1st order and −1st order diffracted light is diffracted toward the corresponding light receiving elements.

  FIG. 19B is a plan view showing the composite diffraction element 143. As shown in the figure, the composite diffraction element 143 has a region divided by dividing lines 143a to 143c. FIG. 19C is a diagram showing a substrate 145 provided with the light receiving element and the issuing element 144. The diffracted light in the areas 46a and 46e of the composite diffraction element 43 is received by, for example, the light receiving elements 47a and 47d, the diffracted light in the areas 46b and 46f is received by, for example, the light receiving elements 47b and 47c, The diffracted light in the region 46d enters the elements 49 and 50, for example, into the three-divided light receiving elements 48 and 51, respectively.

Here, in order to obtain the focus error signal FES, the diffraction grating pattern of the regions 46c and 46d of the composite diffraction element 43 is given, for example, the refractive power of a lens that satisfies the following conditions. First, the light beam incident on the three-divided light receiving elements 49 and 51 is focused on a position farther than the light receiving element. The light beams incident on the three-divided light receiving elements 48 and 50 are focused at a position closer to the composite diffraction element 3 than the light receiving elements. Furthermore, when the optical disc 41 is at the focal point of the objective lens 42, the length of the light beam received on the three-divided light receiving elements 48, 49, 50 and 51 is substantially equal to the direction perpendicular to the dividing line of the light receiving element. To be equal. If the composite diffractive element 43 that satisfies the above conditions is used, the size of the light flux changes on each three-divided light receiving element according to the defocusing of the objective lens 42.
FES = 49b + 51b + 48a + 48c + 50a + 50c
-(49a + 49c + 51a + 51c + 48b + 50b)
The focus error signal FES is obtained by the calculation.

Further, the signal TES1 for correcting the tracking offset generated when the objective lens 42 moves in the direction orthogonal to the information track detects the light flux that has passed through the regions outside the region dividing lines 43b and 43c of the composite diffraction element 43. And
TES1 = 47a + 47d− (47b + 47c)
Is obtained.

The push-pull signal TES2 detects the light flux that has passed through the region between the region dividing lines 43b and 43c of the composite diffraction element 43, and
TES2 = (49a + 49b + 49c + 50a + 50b + 50c)
− (48a + 48b + 48c + 51a + 51b + 51c)
Is obtained.

Therefore, the tracking error signal TES in which the offset caused by the movement of the objective lens 2 is corrected is
TES = TES2-k × TES1
It becomes. Here, k is a correction coefficient.

As described above, the optical pickup described in Patent Document 2 can generate a tracking error signal in which the tracking offset is corrected by dividing the reflected light from the optical disk into multiple parts by the hologram element. On the other hand, the optical pickup described in Patent Document 1 generates three beams by a hologram element to generate a tracking error signal. Here, according to the optical pickup described in Patent Document 2, a hologram element for generating three beams is not required, and the optical integrated unit can be reduced in size and cost.
JP 2006-65935 A (published March 9, 2006) JP 11-73658 A (published March 16, 1999)

  However, the above-described conventional technology has a common problem that the amount of light for signal detection is insufficient and a high-quality reproduction signal cannot be obtained.

  First, the optical integrated unit described in Patent Document 1 uses a differential push-pull method (DPP method) for tracking error detection. Since the DPP method generates sub-beams, the amount of light of the main beam used for reproduction signal generation decreases, and a sufficient amount of light cannot be obtained.

  In the optical integrated unit described in Patent Document 2, signal detection is performed using only the first-order diffracted light without detecting the 0th-order light of the hologram element, so that the amount of light returning from the optical disk is insufficient. This is remarkable in an optical pickup device that performs recording and reproduction at a higher speed.

  In addition, since the optical integrated unit described in Patent Document 1 uses the DPP method, a hologram element for generating three beams is required. Therefore, the structure of the optical integrated unit is complicated and expensive.

  Further, in an optical pickup that performs reproduction or recording on various optical discs including CD, DVD, BD, etc., the objective lens may be arranged at a position shifted from a straight line passing through the center of the optical disc. In this case, as will be described later, a problem occurs when the tracking error detection using the three beams as described above is performed.

Furthermore, the optical integrated unit described in Patent Document 1 includes light separating means having a hologram pattern shown in FIG. As shown in the figure, the light separating means separates the light beam with a circular arc centered on the optical axis as a boundary line. Therefore, the spherical aberration signal (SAES) can be detected with high sensitivity. However, if the center position of the hologram element and the center position of the light beam shift in the radial direction due to the movement of the objective lens during tracking control (objective lens shift), there is a problem that the detection sensitivity of SAES decreases. In the optical integrated unit described in 2, since the non-diffracted light re-enters the semiconductor laser, the oscillation state of the semiconductor laser becomes unstable, which leads to unstable operation of the optical pickup itself.

  In addition, the hologram division shape of the optical integrated unit described in Patent Document 2 cannot detect the spherical aberration error necessary for BD.

Furthermore, in the example of Patent Document 2, a mathematical expression is shown that specifies an optimal shape of a generation region of a signal (tracking error correction signal) for correcting the tracking offset of the hologram element. The present invention has been made to solve the above problems, and the purpose of the invention is to optimize the division shape of the diffraction means for separating the light beam reflected on the optical disk. Accordingly, an object of the present invention is to provide an optical integrated unit with high utilization efficiency of reflected light from an optical disc and an optical pickup device using the optical integrated unit.

  In order to solve the above problems, an optical integrated unit according to the present invention includes a light source that emits a light beam, a diffracting unit that separates reflected light of the light beam reflected by an optical disc, and non-diffracted light separated by the diffracting unit. And a light detecting means for detecting a plurality of light fluxes including the optical surface for transmitting the light flux from the light source and reflecting the reflected light from the optical disk. The diffraction means is provided on the diffraction means. A first boundary line parallel to the radial direction of the optical disc, passing through the optical axis of the incident reflected light, a second boundary line parallel to the first boundary line, and the second boundary line The first region existing outside the optical axis, the second region existing between the first boundary line and the second boundary line, and the first region with respect to the first boundary line. 1 region and a third region existing on the opposite side of the second region, and the second region It is characterized by being divided into a peripheral region that does not include an inner peripheral region and the optical axis containing the optical axis.

  According to said structure, the light beam which radiate | emitted the said light source, was reflected in the said optical disk, and was isolate | separated in the said diffraction means can be detected by a light detection means.

  At this time, the second region of the diffractive means is divided into an inner peripheral region including the optical axis and an outer peripheral region not including the optical axis. As described above, the detection of the spherical aberration error is indispensable for the recording or reproduction of the optical disk having a high recording density. However, the spherical aberration error can be stabilized by detecting the diffracted light beams in the inner peripheral area and the outer peripheral area, respectively. Thus, a spherical aberration error signal can be generated.

  Further, since the optical surface reflects only the reflected light from the optical disk and changes the path of the reflected light, it is possible to prevent the non-diffracted light of the reflected light from reentering the light source, The non-diffracted light can be detected by light detection means. As a result, non-diffracted light with a large amount of light can be used for signal detection, and the reproduction quality can be improved.

  Furthermore, the correction signal of the tracking error signal can be stably generated by detecting the light beam diffracted in the first region of the diffracting means. The correction signal refers to a signal for correcting an offset of a tracking error signal that occurs due to objective lens shift or disc tilt. Thereby, it is not necessary to use a hologram element for generating three beams for generating a tracking error signal. For this reason, it is possible to prevent a decrease in the amount of light of the main beam due to generation of the sub-beams and inconveniences when three beams are used in an optical pickup that performs reproduction or recording on various optical disks described later. Play.

  In the optical integrated unit, it is preferable that a distance between the first boundary line and the second boundary line is 70% or more of an effective radius of a light beam incident on the diffraction unit.

According to the above configuration, the first region does not include an interference region of non-diffracted light and first-order diffracted light.
Therefore, it is possible to avoid the push-pull signal from being included in the correction signal of the tracking error signal and to increase the sensitivity of the tracking error signal. That is, a push-pull signal using interference between non-diffracted light and first-order diffracted light is used to generate the tracking error signal, but signal cancellation that occurs when the correction signal includes a push-pull signal. Can be prevented.

  Further, according to the above configuration, since the second area has a sufficient width, the amount of light beams diffracted in the second area used for detecting the spherical aberration error is increased. Therefore, a spherical aberration error signal with higher sensitivity can be generated, which can contribute to the stable operation of the optical pickup using the optical integrated unit.

  In the optical integrated unit, the boundary line between the inner peripheral region and the outer peripheral region is a first line segment, a second line segment, a third line segment, a fourth line segment, and a fifth line segment. Are connected in this order, and the first line segment, the third line segment, and the fifth line segment are preferably parallel to the first boundary line. .

  According to said structure, the boundary line of the said inner periphery area | region and the said outer periphery area | region is mainly comprised by the straight line parallel to the radial direction of the said optical disk. For this reason, even when the objective lens is displaced in the radial direction during tracking control, the light beam incident on the inner peripheral region is shifted and incident on the outer peripheral region, and vice versa. Thus, a stable spherical aberration error signal can be generated.

  In the optical integrated unit, the second line segment and the fourth line segment are axisymmetric with respect to a straight line passing through the optical axis and parallel to the track direction of the optical disc, and the first boundary line and the first line segment are It is preferable that the distance from the third line segment is longer than the distance between the first boundary line and the first line segment.

  According to the above configuration, since the second line segment and the fourth line segment are line symmetric with respect to a straight line passing through the optical axis and parallel to the track direction of the optical disc, the third line segment is exactly Located at the center of the boundary line between the inner peripheral region and the outer peripheral region, the central portion has a line-symmetric shape. Moreover, since the distance between the first boundary line and the third line segment is longer than the distance between the first boundary line and the first line segment, the center portion is raised. That is, the central portion has a shape close to an arc shape. Therefore, it is possible to generate a spherical aberration error signal with high sensitivity by detecting light beams diffracted in the inner peripheral region and the outer peripheral region.

  In the optical integrated unit, it is preferable that a narrow angle formed by the second line segment and a straight line that intersects the second line segment and parallel to the track direction of the optical disc is 45 °.

  According to said structure, when the said center part has a shape close | similar to a circular arc further, there exists an effect that a highly sensitive spherical aberration error signal can be produced | generated.

  The optical integrated unit further includes tracking error correction signal generation means for generating a correction signal of a tracking error signal based on a detection result of the light beam diffracted in the first region and the non-diffracted light by the light detection means. Is preferred.

  According to said structure, the correction signal of a tracking error signal can be produced | generated using the light beam diffracted in the said 1st area | region. The light beam diffracted in the first region contains more offset signals of tracking error signals generated by objective lens shift and disc tilt than the push-pull signal. Accordingly, by correcting the tracking error signal using the detection result of the light beam diffracted in the first region, it is possible to correct the tracking error signal offset caused by the objective lens shift or the disc tilt, so that the tracking error can be stably performed. There is an effect that a signal can be generated.

  In the optical integrated unit, it is preferable that the first area is divided into two by a fourth boundary line parallel to the track direction of the optical disc passing through the optical axis.

  According to the above configuration, since the first region is divided into two by a straight line passing through the optical axis and parallel to the track direction of the optical disc, the deviation of the light beam incident on the diffracting means in the radial direction is prevented. There is an effect that it can be detected with high sensitivity.

  In the optical integrated unit, the tracking error correction signal generating means generates a tracking error signal based on the detection results of the + 1st order diffracted light and the −1st order diffracted light diffracted in the first region by the light detecting means. It is preferable.

  According to the above configuration, since both the + 1st order diffracted light and the −1st order diffracted light diffracted in the first region are used for generating the correction signal for the tracking error signal, the amount of light flux used for generating the correction signal is sufficient. Can be secured. Therefore, the tracking error signal correction signal can be generated stably.

  The optical integrated unit may further include a focus error signal generation unit that generates a focus error signal based on a detection result of the light beam diffracted in the third region by the light detection unit.

  According to the above configuration, the focus error signal can be generated by the single knife edge method. As a result, it is possible to suppress the influence of the focus offset caused by the positional deviation of the optical system due to a change over time and the like, and it is possible to provide a highly reliable optical pickup device.

  The optical integrated unit may further include a focus error signal generating unit that generates a focus error signal based on a detection result of the light beam diffracted in the third region and the outer peripheral region by the light detecting unit.

  According to the above configuration, the focus error signal can be generated by the double knife edge method. Thereby, it is possible to further suppress the influence of the focus offset resulting from the positional deviation of the optical system due to a change with time and the like, and it is possible to provide a more reliable optical pickup device.

  It is preferable that the optical integrated unit further includes the spherical aberration error signal generation unit that generates a spherical aberration error signal based on a detection result of the light detection unit by the light detection unit with respect to the light beam diffracted in the inner peripheral region and the outer peripheral region.

  According to the above configuration, the state of the light beam separated from the portion near the optical axis of the reflected light reflected from the optical disc and the peripheral portion can be detected. By comparing the two, the cover glass of the optical disc can be detected. There is an effect that it is possible to detect a spherical aberration error that occurs when the thickness changes.

  The optical integrated unit may further include the spherical aberration error signal generation unit that generates a spherical aberration error signal based on a detection result of the light beam diffracted in the outer peripheral region by the light detection unit.

  According to the above configuration, the state of the light beam separated from the peripheral portion of the reflected light reflected by the optical disc can be detected, so that the spherical aberration error can be detected in a state where no focus error has occurred. Furthermore, since the number of light beams detected by the light detection means is reduced, the number of necessary light receiving portions is reduced, which can contribute to cost reduction of the optical integrated unit.

  In the optical integrated unit, the diffractive means has a polarization characteristic whose diffraction efficiency changes depending on the polarization of the light beam, and the polarization characteristic is set so that the light beam from the light source is not diffracted by the diffractive means. It is preferable.

  According to said structure, since the said diffraction means does not isolate | separate the light beam emitted to the said optical disk from the said light source, there exists an effect that the reduction | decrease in the light quantity of the light beam irradiated to this optical disk can be avoided.

  In the optical integrated unit according to the present invention, the third region includes a fourth region including the optical axis by a third boundary line parallel to the first boundary line, and a fifth region not including the optical axis. It may be divided into regions.

  According to the above configuration, the correction signal for the tracking error signal can be generated using the light beam diffracted in the fifth region of the diffractive means in addition to the light beam diffracted in the first region of the diffractive means. . As a result, the amount of light flux used for generating the correction signal is increased, so that the correction signal of the tracking error signal can be generated stably.

  In the optical integrated unit, it is preferable that a distance between the first boundary line and the third boundary line is 70% or more of an effective radius of a light beam incident on the diffraction unit.

  According to said structure, there exists an effect that a push pull signal is not mixed in the light beam diffracted in the said 5th area | region, and the sensitivity of a tracking error signal can be improved.

  The optical integrated unit further includes tracking error correction signal generation means for generating a correction signal of a tracking error signal based on a detection result of the light beam diffracted in the first area and the fifth area by the light detection means. It is preferable.

  According to said structure, the correction signal of a tracking error signal can be produced | generated using the light beam diffracted in the said 1st area | region and the said 5th area | region. The light beams diffracted in the first region and the fifth region contain more offset signals of tracking error signals generated due to objective lens shift and disc tilt than the push-pull signals. Therefore, by correcting the tracking error signal using the detection result of the light beam diffracted in the first region and the fifth region, it is possible to correct the offset of the tracking error signal caused by the objective lens shift or the disc tilt. Furthermore, compared to the case where only the light beam diffracted in the first region is used, the amount of light to be detected is increased, so that the tracking error signal can be generated more stably.

  In the optical integrated unit, it is preferable that the fifth area is divided into two by a fourth boundary line parallel to the track direction of the optical disc passing through the optical axis.

  According to the above configuration, since the fifth region is divided into two by a straight line that passes through the optical axis and is parallel to the track direction of the optical disc, the deviation of the light beam incident on the diffraction means in the radial direction is prevented. There is an effect that it can be detected with high sensitivity.

  In the optical integrated unit, the tracking error correction signal generating means is based on detection results of the + 1st order diffracted light and −1st order diffracted light diffracted in the first region and the fifth region by the light detection means. It is preferable to generate a tracking error correction signal.

  According to the above configuration, since both the + 1st order diffracted light and the −1st order diffracted light diffracted in the first region and the fifth region are used for generating the correction signal of the tracking error signal, the correction signal is generated. A sufficient amount of luminous flux can be secured. Therefore, the tracking error signal correction signal can be generated more stably.

  The optical pickup according to the present invention preferably includes the optical integrated unit.

  According to said structure, stable operation | movement, size reduction, weight reduction, and cost reduction are realizable.

  The optical pickup according to the present invention also includes at least two objective lenses, and in the optical pickup that performs at least one of information recording and reproduction with respect to at least two types of optical discs, the optical integrated unit is at least one. It is preferable to have one.

  According to said structure, it contributes to size reduction and weight reduction of the optical pick-up corresponding to reproduction | regeneration and recording of many types of optical disks which tend to enlarge the apparatus size.

  In addition, a straight line through which a focal point where the light emitted from at least one of the optical integrated units is connected to the optical disc may cross obliquely with respect to the track of the optical disc.

  In the above configuration, when the light beam emitted to the optical disc is moved for tracking, the straight line through which the focal point where the outgoing light from the at least one optical integrated unit is connected to the optical disc passes is the track of the optical disc. Crosses diagonally. Here, if the straight line through which the focal point of the light emitted from the optical integrated unit that uses three beams for generating the tracking error signal passes on the optical disc is not orthogonal to the track of the optical disc, the tracking error signal is accurately obtained. There is a problem that it cannot be generated. According to said structure, since the optical integrated unit which uses 1 beam for the generation of a tracking error signal is used, there exists an effect that a tracking error signal can be produced | generated correctly.

  An optical integrated unit according to the present invention includes a light source, a diffracting unit that separates reflected light from an optical disc, and a light detecting unit that detects a plurality of light beams separated by the diffracting unit. Therefore, various signals necessary for reproduction / recording of the optical disc can be stably generated.

[First Embodiment]
FIG. 2 is a diagram illustrating a schematic configuration of the optical pickup 40 according to the present embodiment. As shown in the figure, the optical pickup according to the present embodiment includes an optical integrated unit 1, a collimator lens 2, and an objective lens 3. The optical disk 4 includes a substrate 4a, a cover layer 4b through which a light beam is transmitted, and a recording layer 4c formed at the boundary between the substrate 4a and the cover layer 4b.

  FIG. 3 is a diagram showing an optical integrated unit according to this embodiment. This figure is a cross-sectional view seen from the y direction perpendicular to the optical axis direction (z direction) shown. As shown in the figure, the optical integrated unit 1 includes a semiconductor laser 11 (light source), a light receiving element 12 (light detecting means), a polarization beam splitter 14 (light guiding means), and a polarization hologram element 32 (diffracting means). ), A quarter wave plate 16, and a package 17.

  The light beam 20 emitted from the light source 11 mounted on the optical integrated unit 1 is collimated by the collimator lens 2 and then condensed on the optical disk 4 via the objective lens 3. Then, the light reflected from the optical disk 4 (hereinafter referred to as “return light”) passes through the objective lens 3 and the collimator lens 2 again and is received on the light receiving element 12 mounted on the optical integrated unit 1. The

  The objective lens is driven in the focus direction (z direction) and the tracking direction (x direction) by an objective lens drive mechanism (not shown), and is focused even if there is surface deflection or eccentricity of the optical disk 4. The spot follows a predetermined position of the information recording layer 4c of the optical disc 4.

  In the present embodiment, a case will be described in which the optical integrated unit 1 is provided with a short wavelength light source having a wavelength of about 405 nm as the light source 11 and a high NA objective lens having an NA of about 0.85 is provided as the objective lens 3. Is not limited to this. However, by providing the short wavelength light source and the high NA objective lens as described above, high-density recording / reproduction becomes possible.

  Next, the arrangement of each component will be described with reference to FIG. In the following description, for convenience of explanation, the surface of the polarization beam splitter 14 on which the light beam 20 emitted from the semiconductor laser 11 is incident is the light beam incident surface of the polarization beam splitter 14, and the return light from the polarization beam splitter 14 is The incident surface is a return light incident surface of the polarization beam splitter 14.

  First, in order to ensure the optical path of the light beam emitted from the semiconductor laser 11 and the optical path of the return light received by the light receiving element 12, the light beam emitting part of the semiconductor laser 11 and the light receiving part of the light receiving element 12 are: It is arranged so as to be included in the region of the window portion 17d formed in the cap 17c of the package 17.

  The polarizing beam splitter 14 is disposed on the package 17. Specifically, the light beam incident surface of the polarizing beam splitter 14 is disposed on the package 17 so as to cover the window portion 17d.

  The polarization hologram element 32 is disposed on the optical axis of the light beam emitted from the semiconductor laser 11 so that the light beam incident surface faces the return light incident surface of the polarization beam splitter 14.

  The polarization beam splitter 14 has a polarization beam splitter (PBS) surface 14a (optical surface) and a reflection mirror 14b (reflection surface).

  The PBS surface 14a in the present embodiment transmits linearly polarized light (P-polarized light) having a polarization vibration surface in the x direction orthogonal to the illustrated optical axis direction (z direction), and polarization vibration perpendicular to the polarization vibration surface. It has a characteristic of reflecting linearly polarized light (S-polarized light) having a plane, that is, having a polarization vibration plane in the y direction perpendicular to the optical axis direction (z direction) shown in the figure. However, the present invention is not limited to this, and the above characteristics can be changed.

  The PBS surface 14a is disposed on the optical axis of the P-polarized light beam emitted from the semiconductor laser 11 so that the light beam 20 is transmitted. The reflection mirror 14b is arranged to be parallel to the PBS surface 14a.

  The polarization hologram element 32 is disposed on the optical axis of the light beam 20 and diffracts S-polarized light and transmits P-polarized light. The diffraction of polarized light is performed by the groove structure (grating) formed in the polarization hologram element 32, and the diffraction angle is defined by the pitch of the grating (hereinafter referred to as the grating pitch).

  Next, the optical path of the light beam in this embodiment will be described in detail.

  As described above, the semiconductor laser 11 that emits the light beam 20 having the wavelength λ = 405 nm is used. Further, in the present embodiment, the light beam 20 is linearly polarized light (P-polarized light) having a polarization vibration plane in the x direction orthogonal to the illustrated optical axis direction (z direction). The light beam 20 emitted from the semiconductor laser 11 enters the polarization beam splitter 14.

  The light beam 20 (P-polarized light) incident on the PBS surface 14a passes through the PBS surface 14a as it is. The light beam 20 that has passed through the PBS surface 14 a then enters the polarization hologram element 32.

  Of the incident light, the polarization hologram element 32 diffracts S-polarized light and transmits P-polarized light as it is. Specifically, the polarization hologram element 32 diffracts the incident S-polarized light into zero-order diffracted light (non-diffracted light) and first-order diffracted light (diffracted light).

  That is, the P-polarized light beam 20 emitted from the semiconductor laser 11 enters the polarization hologram element 32 and is transmitted as it is. The P-polarized light beam 20 transmitted through the polarization hologram element 32 is incident on the quarter-wave plate 16. A detailed hologram pattern of the polarization hologram element 32 will be described later.

  The quarter-wave plate 16 can receive linearly polarized light, convert it into circularly polarized light, and emit it. Therefore, the P-polarized light beam 20 (linearly polarized light) incident on the quarter-wave plate 16 is converted into a circularly-polarized light beam and emitted from the optical integrated unit 1.

  The circularly polarized light beam emitted from the optical integrated unit 1 is collimated by a collimator lens, and then condensed on an optical disk via an objective lens. Then, the light beam reflected by the optical disk, that is, the return light again passes through the objective lens and the collimator lens, and again enters the quarter wavelength plate 16 of the optical integrated unit 1.

  The return light incident on the quarter-wave plate 16 of the optical integrated unit 1 is circularly polarized light, and the quarter-wave plate 16 causes the polarization vibration plane in the y direction with respect to the illustrated optical axis direction (z direction). Is converted to linearly polarized light (S-polarized light). The S-polarized return light is incident on the polarization hologram element 32.

  As described above, the S-polarized return light that has entered the polarization hologram element 32 is diffracted into zero-order diffracted light (non-diffracted light) and first-order diffracted light (diffracted light) and is emitted. The diffracted S-polarized return light (0th-order diffracted light and 1st-order diffracted light) enters the polarization beam splitter 14, is reflected by the PBS surface 14a, is further reflected by the reflection mirror 14b, and is reflected from the polarization beam splitter 14. Exit. The S-polarized return light emitted from the polarization beam splitter 14 is received by the light receiving element 12. The light receiving part pattern of the light receiving element 12 will be described later.

  The optical integrated unit according to the present invention is not limited to the polarizing beam splitter 14, but can return the light beam 20 emitted from the semiconductor laser 11 and reflected by the optical information recording medium as described above. Any configuration is possible as long as it can guide light in a direction different from that of the semiconductor laser 11, change the optical path of the return light, and cause the light receiving element 12 to receive the return light. Therefore, in addition to the polarization beam splitter, a beam splitter having the optical surface 14a as a half mirror surface can be used.

  FIG. 4 is a schematic diagram showing a hologram pattern formed on the polarization hologram element 32. As shown in the figure, the hologram pattern of the polarization hologram element 32 includes seven regions 32a, 32b, 32c, 32d, 32e, 32f, and 32g.

  As dividing lines for dividing these regions, a straight line D1 (first boundary line) extending in the radial direction passing through the optical axis OZ, and straight lines D6 and D6 ′ (second and third boundary lines) parallel to the straight line D1. , There are straight lines D7 and D7 ′ on the straight line D8 (fourth boundary line) extending in the track direction passing through the optical axis OZ, and a dividing line D2.

  The straight lines D6 and D6 'are symmetric with respect to the straight line D1, but are not limited thereto. However, the distance h3 between the straight line D6 and the straight line D1 and the distance h3 ′ between the straight line D6 ′ and the straight line D1 are 70% or more of the radius r1 of the effective diameter of the light beam 20 (h3 ≧ 0.7r1, h3). It is preferable that “≧ 0.7r1) is set.

  Here, a region sandwiched between the straight line D1 and the straight line D6 'is a region 32c (fourth region).

  In addition, regions 32g and 32d are obtained by dividing a region outside the straight line D6 as viewed from the optical axis OZ (first region) by a line segment D7 on the straight line D8. Similarly, regions 32f and 32e are obtained by dividing a region (fifth region) outside the straight line D6 'as viewed from the optical axis OZ by a line segment D7' on the straight line D8.

  The region 32a (inner peripheral region) and the region 32b (outer peripheral region) are obtained by dividing the region (second region) surrounded by the straight line D1 and the straight line D6 by the dividing line D2. As viewed from the optical axis Oz, the region 32a is on the inner peripheral side, and the region 32b is on the outer peripheral side. The region 32a includes the optical axis Oz.

  The dividing line D2 projects (swells) toward the outer periphery of the polarization hologram element 32 at the center, and the end of the projecting part (straight line D5 (described later)) is substantially parallel to the radial direction. .

  More specifically, the dividing line D2 is a pair of line segments D3 (first line segment) and D3 ′ parallel to the radial direction and positioned at both ends of the hologram element 2 so as to be symmetrical with respect to the straight line D8. (Fifth line segment) and the straight line D3 are inclined with respect to the straight line D8 from the end point A on the optical axis OZ side, and extend in a direction away from the straight line D1 and a direction approaching the straight line D8. A pair of line segments D4 (second line segment) and D4 ′ (fourth line segment) that are axisymmetric with respect to D8, and an end point B opposite to the end point A in these line segments D4 and D4 ′ It consists of a line segment (swelling ridge) D5 (third line segment) formed by connecting each other.

  That is, the protruding portion is formed by the line segment D4 and the line segment D5. The line segment D4 is a straight line here, but is not limited to a straight line and may be a curved line segment. That is, the projecting portion swells from the center of the dividing line D2, and the shape is not particularly limited as long as the ridge (line segment D5) is parallel to the radial direction.

  Furthermore, it is preferable that the line segment D5 is located farther from the straight line D1 than the pair of line segments D3 (h2> h1).

  The inclination angle θ of the line segment D4 with respect to the straight line D8 is preferably 45 degrees (θ = 45 deg), and the inclination angle θ of the line segment D4 ′ with respect to the straight line D8 is −45 degrees (θ = −45 deg). It is preferable that

  The conditions that h2> h1, θ = ± 45 deg, and h3 ≧ 0.7r1 will be described later.

  Next, the relationship between the division pattern of the polarization hologram element 32 and the light receiving portion pattern of the light receiving element 12 will be described.

  FIGS. 1 and 5 are diagrams illustrating a light beam condensing state on the light receiving element 12. As shown in both figures, the light receiving element 12 includes 14 light receiving portions 12a to 12n. 1A also shows the relationship between the seven regions 32a to 32g of the polarization hologram element 32 and the traveling direction of the first-order diffracted light. Actually, the center position of the polarization hologram element 32 is set at a position corresponding to the center position of the light receiving portions 12a to 12d, but for the sake of explanation, it is shifted in the y direction with respect to the optical axis direction (z direction). It is shown.

  The return light from the optical disk 4 is separated into non-diffracted light (0th order diffracted light) 55 and diffracted light (first order diffracted light) in the polarization hologram element 32. The light receiving element 12 includes a light receiving unit for receiving a light beam necessary for detecting an information signal and a servo signal among the non-diffracted light 55 and the diffracted light.

  Specifically, a total of 12 beams of one non-diffracted light (0th-order diffracted light) 55 of the polarization hologram element 32 and 11 first-order diffracted lights are detected in each light receiving unit, and various signals are generated. In the present embodiment, for the TES detection by the push-pull method, the light receiving element 12 is focused on the non-diffracted light 55 so that the beam diameter of the non-diffracted light (0th order diffracted light) 55 has a certain size. It is installed at a position slightly shifted to the back with respect to the point. The present invention is not limited to this, and the light receiving element 12 may be installed at a position shifted to the near side with respect to the condensing point of the non-diffracted light 55.

  In this way, since the light beam (non-diffracted light 55) having a certain size of light beam diameter is condensed on the boundary portions of the light receiving portions 12a to 12d, these four light receiving portions (12a to 12d). Can be adjusted so that the positions of the non-diffracted light 55 and the light receiving element 12 can be adjusted.

  The + 1st order diffracted light from the regions 32a, 32b, and 32c of the polarization hologram element 32 is incident on the two-divided light receiving parts (12i and 12j), (12k and 12l), and (12m and 12n), respectively. Although the -1st order light is not shown, each light receiving portion is arranged so as not to enter the light receiving portion.

  The + 1st order diffracted light and the −1st order diffracted light from the regions 32d and 32e are incident on 12f and 12h, which are arranged at point-symmetric positions with respect to the optical axis of the non-diffracted light 55, respectively.

  The + 1st order diffracted light and the −1st order diffracted light from the regions 32f and 32g are incident on 12e and 12g disposed at point-symmetrical positions with respect to the optical axis of the non-diffracted light 55, respectively.

  The servo signal is generated as follows. The output signals of the light receiving units 12a to 12n are represented as Sa to Sn.

The information signal (RF) is detected using the non-diffracted light 55. That is,
RF = Sa + Sb + Sc + Sd
Can be given by. Those skilled in the art will readily understand that applying a well-known circuit technique based on the above formula can produce a circuit that generates RF.

  The tracking error signal (TES1) by the DPD method is detected by performing a phase comparison of Sa to Sd. Specifically, the following principle is used.

  When the light beam condensed by the objective lens 3 scans the pit row formed on the recording layer 4c of the optical disc 4, the intensity distribution pattern of the reflected beam changes depending on the positional relationship between the pit row and the light beam. Therefore, when (Sa + Sc) and (Sb + Sd) are detected, the light beam is in the same phase when scanning the center of the pit row, but the position where the light beam is shifted from the center of the pit row is scanned. In such a case, a phase difference in the opposite direction occurs depending on the direction of deviation. Therefore, a tracking error signal can be obtained by detecting the phase difference between (Sa + Sc) and (Sb + Sd).

The tracking error signal (TES2) by the PP method is obtained by calculating a main push-pull signal (MPP) and a tracking error correction signal (TES3) that corrects a tracking offset generated by an objective lens shift or an optical disc tilt. That is,
MPP = (Sa + Sb) − (Sc + Sd)
TES3 = (Se + Sg) − (Sf + Sh)
TES2 = MPP-α × TES3
Given by. Here, α is set to an optimum coefficient for canceling offset due to objective lens shift or optical disc tilt. Those skilled in the art will readily understand that a circuit (tracking error correction signal generation means) that generates TES3 can be produced by applying a well-known circuit technique based on the above formula. The same applies to circuits that generate MPP and TES2. Moreover, although the optical integrated unit 1 may be provided with the above circuit, it is not limited to this. That is, these circuits may be provided in the optical pickup 40. The same applies to a circuit for generating FES (focus error signal generating means) and a circuit for generating SAES (spherical aberration error signal generating means) described later.

  As described above, the light beams diffracted in the regions 32d and 32e (first region) or the regions 32f and 32g (fifth region) are detected by the same light receiving element. Therefore, for example, even if only the light beam diffracted in the region 32g and the region 32d is detected, a correction signal for the tracking error signal similar to that in the present embodiment can be generated. However, as in the present embodiment, using a plurality of regions increases the amount of light to be detected, and a tracking error signal correction signal can be generated more stably.

The focus error signal (FES) can be detected using a double knife edge method. That is, FES is
FES = (Sm−Sn) −β (Sk−Sl)
Given by. β is a coefficient for correcting an offset caused by a difference in light quantity.

The focus error signal (FES) can also be detected using a single knife edge method. In that case, FES is
FES = (Sm−Sn)
Given by.

  Those skilled in the art will readily understand that a circuit that generates FES (focus error signal generation means) can be manufactured by applying a well-known circuit technique based on the above formula.

  In FIG. 1A, recording is performed in a state in which the position of the collimator lens 2 in the optical axis direction is adjusted so that spherical aberration does not occur in the focused beam by the objective lens 3 depending on the thickness of the cover layer 4b of the optical disk 4. It is a figure which shows the condensing state of the light beam on the light receiving element 12 in the case of condensing to a focused state on the layer. That is, no spherical aberration error and focus error occur.

  As shown in FIG. 1A, FES is not detected in the focused state.

  FIG. 1B shows a light beam on the light receiving element 12 when the objective lens 3 approaches the optical disk 4 from the state of FIG. As the objective lens 3 approaches the optical disc 4, the beam diameter of the light beam increases. However, the light beam does not protrude from the light receiving unit 12.

  As shown in FIG. 1B, in the state where the defocus has occurred, the FES is detected by either the double knife edge method or the single knife edge method.

  Next, detection of the spherical aberration error signal (SAES) will be described.

  As described above, the optical pickup device according to the present embodiment includes the optical integrated unit 1 and the short wavelength light source 11 having a wavelength of about 405 nm and the objective lens having the high NA objective lens 3 having an NA of about 0.85. Density recording / reproduction is possible. In order to increase the recording density of the optical disk including this embodiment, it is necessary to shorten the wavelength of the laser beam and increase the numerical aperture NA of the objective lens. For example, a DVD (Digital Versatile Disc), which has a higher density than a CD (Compact Disc), has a larger capacity using an objective lens with a numerical aperture NA of 0.6 and laser light with a wavelength of 650 nm. Is realized. Further, in BD (Blu-ray Disc), further increase in capacity is realized by using an objective lens having a numerical aperture NA of 0.85 and laser light having a wavelength of 405 nm. However, in an optical disk with a large capacity, the influence of aberration becomes a problem as the numerical aperture NA of the objective lens increases.

  When the laser beam is irradiated onto the recording area of the optical disc, the cover layer between the incident surface of the laser beam and the recording layer is a distance through which the laser beam irradiated onto the recording layer on which information is recorded is transmitted. The spherical aberration caused by the error in the thickness t (hereinafter referred to as the disc substrate thickness t) increases in proportion to the fourth power of the numerical aperture NA. In order to suppress this spherical aberration, it is effective to reduce the dimensional tolerance of the disk substrate thickness t. For example, a CD disk substrate thickness t of a CD having a laser beam wavelength of 780 nm and a numerical aperture NA of 0.45 is ± 100 μm, a laser beam wavelength of 650 nm, and a numerical aperture NA of 0.6. While the dimensional tolerance of the disk substrate thickness t is ± 30 μm, the disk substrate thickness of the next-generation high-density optical disk in which the wavelength of the laser beam is 405 nm and the numerical aperture NA is 0.85, as in this embodiment. The dimensional tolerance of the length t is ± 3 μm. Thus, as the capacity is increased, the manufacturing accuracy of the disk becomes stricter in terms of acceleration.

  However, since the error of the disk substrate thickness t depends on the manufacturing method of the optical disk, there is a problem that it is very difficult to increase the dimensional accuracy of the disk substrate thickness t. Also, increasing the dimensional accuracy of the disk substrate thickness t has the disadvantage of increasing the manufacturing cost of the optical disk. Therefore, the optical pickup device is required to have a function of correcting spherical aberration that occurs when reproducing an optical disk.

  In general, spherical aberration correction is performed by mechanically moving a lens such as a beam expander. In order to perform this spherical aberration correction accurately and at high speed, it is necessary to detect a spherical aberration error signal which is a target of spherical aberration correction.

  Also in the present embodiment, in order to correct spherical aberration caused by the thickness error of the cover layer 4b, the collimator lens 2 is adjusted in the optical axis direction by a collimator lens driving mechanism (not shown), or the collimator lens 2 A beam expander driving mechanism (not shown) is adjusted for a beam expander (not shown) constituted by two lens groups arranged between the objective lens 3 and the objective lens 3.

  Various methods have been proposed for detecting a spherical aberration correction signal for controlling such a drive mechanism. For example, there is a method in which return light is separated into two light beams by a hologram element and a spherical aberration error signal is detected based on the focal positions of the two light beams (see Patent Document 1).

Also in this embodiment, the spherical aberration error signal (SAES) is detected using a detection signal from the light beam separated into the inner and outer circumferences. That is, using the detection result of the light receiving element 12 of the light beam diffracted in the region 32a and the region 32b, SAES is
SAES = (Sk−Sl) −k (Si−Sj)
Given by. Here, k is set to an optimum coefficient for canceling the SAES offset.

SAES can also be detected using only the light beam diffracted in the outer peripheral region (region 32b). In that case, SAES is
SAES = (Sk−Sl). At this time, the light receiving portions 12i and 12j are not required, the number of light receiving elements necessary for signal detection is reduced, and it is possible to contribute to cost reduction of the optical integrated unit. However, as shown in FIG. 1B, there is a problem that SAES is detected even when a spherical aberration error does not occur and only a defocus occurs.

  A person skilled in the art can easily understand that a circuit that generates SAES (spherical aberration error signal generating means) can be manufactured by applying a known circuit technique based on the above formula.

  5 (a) and 5 (b) show the optical disc positioned at the focal point of the objective lens in a state where spherical aberration is generated in the focused beam of the objective lens due to the influence of the thickness error of the cover layer of the spherical aberration optical disc. It is a figure explaining the shape of the light beam on the light receiving element 12 in the case of being. Since the spherical aberration remains, the inner peripheral beam (the light beam diffracted in the region 32a) and the outer peripheral beam (the light beam diffracted in the region 32b) are larger in the opposite directions with respect to the dividing line. This is because the generation direction of spherical aberration (sign of thickness error) is different between FIG. 5A and FIG. Further, as shown in FIGS. 5A and 5B, in the state shown in the figure, SAES can be detected using either of the above-described equations.

  As described above, by using the optical integrated unit 1, the light beam transmitted through the polarization beam splitter 14 is incident on the polarization diffraction element 16, and the light reception element 12 is incident on the polarization diffraction element 32. The return light that has been diffracted and passed through the polarization beam splitter 14 is received, and each signal is generated.

  Next, the optimum division shape of the area on the polarization hologram element 32 will be described.

  In the optical pickup 40 according to the present embodiment, by moving the objective lens 3 in the radial direction (radial direction) of the optical disk 4, the light beam is always focused on the track formed on the information recording layer 4 c of the optical disk 4. ing. That is, tracking control is performed.

  Here, when the polarization hologram element 32 and the objective lens 3 are integrally formed, the center of the light beam and the center of the polarization hologram element 32 always coincide. However, when the polarization hologram element 32 and the objective lens 3 are independently provided in the optical pickup, a situation occurs in which the center of the light beam does not coincide with the center of the polarization hologram element 32 during tracking control.

  Here, in the polarization hologram element 132 described in Patent Document 1 shown in FIG. 16, when the light beam is shifted in the radial direction, the region on the hologram element on which the light beam is incident may change. For example, a part of the light beam that should be diffracted in the region 32a of the polarization hologram element 32 is diffracted in the region 32b, or a part of the light beam that is supposed to be diffracted in the region 32b of the polarization hologram element 32 is a region. Or diffracted at 32a. Accordingly, the light beam diffracted in each region is received by a light receiving unit different from the light receiving unit that should be received.

  As described above, in the polarization hologram element 132, the deviation between the center of the light beam and the center of the hologram element affects the electrical signal from each light receiving portion of the photodetector. Therefore, even if the amount of spherical aberration is constant, SAES changes depending on the amount of deviation. Therefore, there is a problem that even if spherical aberration is corrected based on SAES, appropriate correction cannot be performed. In order to suppress the influence on the SAES due to the deviation of the center (optical axis) of the light beam in the radial direction of the optical disk, a segmented shape by straight lines parallel to the radial direction may be used.

  Here, for comparison with the polarization hologram element 132, the hologram element 32 'having a shape not having the tracking error correction signal generation region (32d to 32g) shown in FIG.

  FIG. 7A is a graph showing the relationship between SAES and the change in the thickness of the cover glass of the optical disc when the hologram element 32 'is used. FIG. 7B is a graph showing the relationship between SAES and the change in the thickness of the cover glass of the optical disk when the polarization hologram element 132 shown in FIG. 16 is used.

  The division radius r11 of the polarization hologram element 132 is set to r11 = 0.7r10 when the effective radius r10 of the light beam 20 is set. Further, the position (distance from the straight line D1) h1 of the polarization hologram element 32 and the polarization hologram element 32 according to the present embodiment is h1 = 0.3r1, and the division line (line segment D4) of the polarization hologram element 32. The distance h2 from the straight line D1 is h2 = 0.6r1, but is not limited to this.

  7 (a) and 7 (b) show the relationship between the SAES and the change in the thickness of the cover glass when the amount of deviation in the radial direction between the center of the hologram element and the center of the light beam is 0 μm and 300 μm. Yes. Note that the radius of the effective diameter of the light beam defined by the aperture of the objective lens is 1.5 mm. Therefore, 300 μm corresponds to 20% of the radius of the effective diameter. This does not limit the effective system of the light beam.

  From the graph shown in FIG. 7A, it can be seen that when the light beam is separated by the dividing line of the hologram element 32 ', even if the hologram element and the center of the light beam are shifted by 300 μm, there is almost no influence of SAES.

  However, as shown in FIG. 7B, when the light beam is divided by the dividing line of the polarization hologram element 132, the SAES is obviously affected by the deviation between the center of the hologram element and the center of the light beam. I understand that.

  The polarization hologram element 32 according to the present embodiment shown in FIG. 4 and the hologram element 32 ′ shown in FIG. 6 have a portion (both ends; straight lines D3, D3 ′) other than the protruding portion and a straight line D5 located at the top of the protruding portion. Is a straight line parallel to the radial direction, and even if the objective lens shift occurs due to tracking control and the center of the hologram element and the center of the light beam are shifted, the light beam is diffracted in another divided region. There are few, and the change of the detection sensitivity of SAES is small (refer Fig.7 (a)). Therefore, it can be seen that the hologram element shown in FIGS. 4 and 6 is excellent.

  Further, since the dividing line D2 partially includes a line segment D4 inclined with respect to the straight line D8, the polarization hologram element 32 has a dividing pattern having a shape close to a semicircle centered on the optical axis OZ. . Thereby, since it is possible to calculate a spherical aberration error close to the differential output inside and outside the semicircle having a large detection sensitivity, it is possible to detect SAES having a large absolute value of sensitivity.

  From the above, it can be seen that the hologram element 32 ′ having the shape shown in FIG. 6 satisfies the conditions that the change in SAES detection sensitivity is small and the absolute value of the SAES detection sensitivity is large even when the objective lens shift occurs. The polarization hologram element 32 shown in FIG. 4 according to the present embodiment uses the regions 32d and 32g as tracking error correction signals and not used for SAES detection as compared with the hologram element 32 ′ shown in FIG. Although the absolute value of the SAES detection sensitivity is smaller than that of the hologram element 32 ′ shown in FIG. 3, it can be seen that there is almost no change in detection sensitivity when the objective lens shift occurs because the dividing line D5 is parallel to the radial direction.

  In order to approximate the dividing line D2 of the polarization hologram element 32 to the dividing line D101 of the polarization hologram element 132 shown in FIG. 16, it is desirable that h2> h1 and θ = ± 45 deg. It is visually obvious that the division line of the polarization hologram element 32 and the division line of the polarization hologram element 132 are approximated by satisfying the above condition. Hereinafter, the reason why this relationship is desirable will be described using experimental results. To do.

  8 shows the change in the thickness of the cover glass of SAES and the optical disc when the inclination angle θ in FIG. 6 is ± 45 deg and ± 90 deg (h1 = 0.3r1, h2 = 0.6r1, l1 = 0.6r). It is a graph which shows the relationship with (micrometer). As can be seen from the figure, the absolute value of the SAES detection sensitivity is increased by setting the inclination angle θ to ± 45 deg. Therefore, it is preferable to set the inclination angle θ to ± 45 deg.

  Furthermore, the distance h3 between the straight line D6 and the straight line D1 that divides the tracking error correction signal generation regions 32d to 32g of the polarization hologram element 32 is preferably h3 ≧ 0.7r1. The reason why this condition is desirable will be described.

  The light incident on the track of the optical disk is separated from the disk track into non-diffracted light and ± first-order diffracted light. The non-diffracted light and the first-order diffracted light interfere with each other, and an interference pattern as shown in FIG. In the push push-pull method, the difference in the light intensity (push-pull signal) in the interference region between the non-diffracted light / first-order diffracted light and the non-diffracted light / first-order diffracted light is calculated by the above-described MPP calculation, and the result is calculated by the objective lens drive mechanism Feedback. The objective lens driving mechanism drives the objective lens in the radial direction so that this light amount difference becomes zero (so that the beam condensed on the optical disk is at the center of the desired track). On the other hand, the tracking error correction signal TES3 is a signal for correcting an offset generated when the beam 20 is displaced in the radial direction on the polarization hologram element 32 due to the radial shift or disc tilt of the objective lens. In addition, it is preferable that the push-pull signal that is a component of the interference region between the non-diffracted light and the ± first-order diffracted light is not mixed. As can be seen from the arithmetic expression of TES2, when a push-pull signal is mixed in the tracking error correction signal TES3, the signal amplitude of TES2 decreases, which may cause a problem in tracking error detection.

  FIG. 10 is a diagram showing the relationship of the signal amplitude of the tracking error signal TES2 when the objective lens is shifted in the radial direction when h3 = 0.4r1, 0.5r1, 0.6r1, and 0.7r1. As shown in the figure, when h3 = 0.6r1 and 0.7r1, there is no decrease in the signal amplitude, and it can be seen that the push-pull signal is not mixed in the tracking error correction signal. On the other hand, it can be seen that the signal amplitude decreases when h3 = 0.4r1 and 0.5r1. Therefore, if the distance h3 between the dividing lines D1 and D6 of the polarization hologram element 32 is h3 ≧ 0.6r1 with respect to the radius r1 of the incident light beam, a decrease in the signal amplitude of the TES2 is prevented and a stable tracking error signal is obtained. Can be obtained.

  In the optical pickup according to the present invention, the spherical aberration error signal SAES is detected using at least the diffracted light in the region 32b. When h3 is changed, since the shape of the region 32b is changed, the SAES detection sensitivity is also changed. FIG. 11 is a graph showing the results of calculating the values taken by SAES when h3 is 0.5r1, 0.6r1, 0.7r1, 0.8r1, 0.9r1 and r1. In the results shown in the figure, SAES is detected using only the diffracted light in the region 32b. As shown in the figure, when h3 ≧ 0.7r1, the detection sensitivity of SAES hardly deteriorates. On the other hand, when h3 ≦ 0.6r1, the detection sensitivity deteriorates to half or less compared to the case of h3 = r1. Therefore, in order to suppress deterioration in detection sensitivity of the spherical aberration error signal, it is desirable that h3 ≧ 0.7r1.

  From the above, by setting h3 ≧ 0.7r1, it is possible to secure the tracking error signal amplitude and the detection sensitivity of the spherical aberration error signal, and to realize a stable operation of the optical pickup.

  As described above, the optical integrated unit is configured to have high use efficiency of the return light from the optical disc and prevent re-incidence of the return light to the semiconductor laser, and the diffraction unit included in the optical integrated unit is generated when the objective lens is shifted. A tracking error correction signal for correcting an offset of the tracking error signal and a split shape capable of generating a spherical aberration error signal, and by optimizing the split shape of the diffraction means, It is possible to secure the signal light quantity and increase the absolute value of the detection sensitivity of the spherical aberration error signal (ensure the signal quality), and even if the condensing optical system moves during tracking control, the spherical aberration error An optical integrated unit that does not cause a change in signal detection sensitivity is provided.

[Second Embodiment]
Another embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the configuration of the optical integrated unit 1 is the same as that of the first embodiment. Therefore, the description of the optical integrated unit 1 is omitted, and the configuration of the optical pickup 41 on which the optical integrated unit 1 is mounted will be described.

  FIG. 12 is a schematic plan view showing the configuration of the optical pickup 41 of the present embodiment. The optical pickup 41 is an optical pickup device compatible with various types of discs (BD / DVD / CD). As shown in the figure, the optical pickup 41 includes an optical integrated unit 1, collimator lenses 3 and 35, a dichroic mirror 36, a BD rising mirror 52, a BD objective lens 53, a DVD / CD semiconductor laser 33, a polarized beam. The splitter 34 includes a DVD / CD raising mirror 37, a DVD / CD objective lens 54, a condenser lens 38, and a DVD / CD light receiving element 39. In the figure, each member is overlapped, but the optical disk 4 (not shown) is located on the foremost side of the paper, the BD objective lens 53 and the DVD / CD objective lens 54 are located on the farthest side of the paper. Other members are arranged on the back side. However, the arrangement of each member is not limited to this.

  The dichroic mirror 36 and the DVD / CD rising mirror 37 are formed so as to transmit light having a wavelength of 405 nm and reflect light having a wavelength of 650 nm and 780 nm.

  In general, in an optical pickup, an objective lens is driven in the radial direction (x direction) of an optical disc in order to read information on a desired track on the optical disc. In the optical pickup 41, the DVD / CD objective lens 54 is driven so that the center O1 of the DVD / CD objective lens 54 coincides with the radial line 60 passing through the center O of the optical disc when viewed from the y-axis direction. Is done. That is, the focus of the DVD / CD objective lens 54 is driven so as to be on the straight line 60. The BD objective lens 53 is installed at a position shifted from the DVD / CD objective lens 54 in the track direction (z direction).

  Next, the operation of the optical pickup 41 will be described. The optical integrated module 1 emits a light beam J having a wavelength of 405 nm for BD. The light beam J is collimated by the collimator lens 3 and passes through the dichroic mirror 36 and the DVD / CD rising mirror 37. Thereafter, the light is reflected by the BD rising mirror 52 in a direction (−y direction) perpendicular to the paper surface of FIG. 12 and condensed on the optical disk 4 (not shown) by the BD objective lens 53. The light beam J reflected by the optical disk 4 travels in the opposite direction to the forward path and is detected by the light receiving element 12 installed in the optical integrated unit 1. In this way, reproduction / recording on the BD is performed.

  On the other hand, the DVD / CD semiconductor laser 33 can emit a light beam having a wavelength of 650 nm for DVD and a wavelength of 780 nm for CD. The light beam K emitted from the DVD / CD semiconductor laser 33 (650 nm for DVD reproduction / recording and 780 nm for CD reproduction / recording) passes through the polarization beam splitter 34 and is collimated by the collimator lens 35. The Thereafter, the light is reflected by the dichroic mirror 36, reflected by the DVD / CD rising mirror 37 in the direction perpendicular to the paper surface (−y direction), and condensed on the optical disk 4 by the DVD / CD objective lens 54. The light beam K reflected by the optical disk 4 travels in the opposite direction to the forward path through each of the objective lens 54, DVD / CD rising mirror 37, dichroic mirror 36, and collimator lens 35, and is polarized by the polarization beam splitter 34. The light is reflected and detected by the DVD / CD light receiving element 39 via the condenser lens 38.

  Here, advantages of the optical pickup 41 according to the present embodiment will be described by comparison with the conventional technique described in Patent Document 1. Since the optical pickup 41 includes the optical integrated unit 1, tracking control during stable BD recording / reproduction can be performed.

  FIG. 13A is a diagram showing how the optical disk 4 and the DVD / CD objective lens 54 and the BD objective lens 53 are driven. FIGS. 13B, 13C, and 13D show the condensing state on the optical disc 4 when the optical integrated unit 101 described in Patent Document 1 is used instead of the optical integrated unit 1 according to the present embodiment. FIG. The optical integrated unit 101 performs tracking error detection using three beams. Therefore, as shown in the figure, the main beam Mb (non-diffracted light of the diffraction grating for three beams), the sub beam Sb1 (+ 1st order diffracted light) and the sub beam Sb2 (−1st order diffracted light) are collected on the optical disc 4. The

  As shown in FIG. 13A, the DVD / CD objective lens 54 is disposed at a position corresponding to a straight line passing through the disc center O in the optical pickup driving direction (radial direction). That is, the focal point of the DVD / CD objective lens 54 is on the straight line. Therefore, while the track for recording / reproduction of the optical pickup 41 moves from the inner periphery to the outer periphery of the optical disc 4, the direction of the track and the straight line through which the focal point of the objective lens 54 passes are always orthogonal.

  On the other hand, the BD objective lens 53 is shifted from the DVD / CD objective lens 54 in the track direction. Therefore, the angle formed by the straight line through which the focal point of the objective lens 53 passes and the track direction of the optical disk 4 increases from the inner periphery toward the outer periphery. Therefore, as shown in FIG. 13C, for example, even if the three-beam hologram element is adjusted so that the main beam Mb and the sub beams Sb1 and Sb2 are incident on the same track in the intermediate portion of the disc, the inner peripheral portion ( In FIG. 13 (b)) or the outer periphery (FIG. 13 (d)), the angle between the direction in which the three beams are arranged and the track direction changes, so that a situation occurs in which the three beams do not enter the same track.

  At this time, in each of the situations of FIGS. 13B, 13C, and 13D, the cases where the boundary passes from the information unrecorded portion to the recording portion of the optical disk are compared. In the optical disc, the reflectance is lower in the portion where information is recorded than in the unrecorded portion. That is, the amount of return light reflected by the recording unit is smaller than the amount of return light reflected by the non-recording unit. In the situation shown in FIG. 13C in which three beams are incident on the same track, each moves along the boundary between the recorded and unrecorded portions simultaneously with the movement of the optical pickup in the radial direction. Since the change in the return light quantity accompanying the recording / unrecorded part passage with the return light of the sub beam occurs at the same time, there is no problem in detecting the tracking error signal. On the other hand, in the situation shown in FIGS. 13B and 13D in which the three beams are not condensed on the same track, Sb1 and Sb2 are incident on the recording unit prior to the other beams, so that the sub beam is reflected back. The amount of light decreases first. Therefore, the tracking error signal fluctuates until the three beams pass the boundary between the recorded part and the unrecorded part, and an accurate tracking operation becomes impossible.

  On the other hand, since the optical pickup according to the present embodiment generates a tracking error signal without generating three beams, the optical disk can be used even when the objective lens passes through the center of the optical disk and is not arranged on a straight line in the pickup driving direction. The tracking error signal does not fluctuate when passing through the boundary between the recorded portion and the unrecorded portion, and a stable tracking error signal can be generated.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for an optical pickup device that performs reproduction / recording of a BD that requires spherical aberration error detection, or an optical pickup device that performs reproduction / recording of a plurality of types of optical disks including a BD.

(A) is explanatory drawing which shows the condensing state of the condensing spot on a photodetector in a state without a focus shift and a spherical aberration error, (b) is a focus shift generated in the state without a spherical aberration error. It is explanatory drawing which shows the condensing state of the condensing spot on the photodetector in the case of being. It is sectional drawing which shows the outline of the optical pick-up concerning 1st Embodiment. It is sectional drawing which shows the optical integrated unit which concerns on 1st Embodiment. It is the schematic diagram which showed the hologram pattern formed in the polarization hologram element which concerns on 1st Embodiment. It is explanatory drawing which shows the condensing state of the light spot on a light receiving element when a spherical aberration error generate | occur | produces. It is a shape figure of the hologram pattern which abbreviate | omitted the division area for tracking error correction with respect to the hologram pattern which concerns on 1st Embodiment. (A) is a graph which shows the relationship between the spherical aberration error signal of the hologram element which concerns on this invention, and the thickness change of a cover glass, (b) is the spherical aberration error signal of the hologram element which concerns on a prior art, and cover glass. It is a graph which shows the relationship with thickness change. It is a graph which shows the relationship between a dividing line spherical aberration error signal and the thickness change of a cover glass when changing the shape of the dividing line of a hologram element. It is a figure which shows the interference pattern of the non-diffracted light on a hologram element, and a 1st-order diffracted light. It is a graph showing the relationship between the distance between a 1st boundary line and a 2nd boundary line, and the magnitude | size of the push pull amplitude of a tracking error signal. It is a graph showing the relationship between the distance between a 1st boundary line and a 2nd boundary line, and a spherical aberration error signal. It is a schematic plan view of the optical pickup which concerns on 2nd Embodiment. (A) is a figure which shows the mode of the radial direction shift of the optical disk and the objective lens which concerns on 2nd Embodiment, (b) shows the relative positional relationship of the light beam and disk track | truck in an optical disk inner peripheral part. (C) is a diagram showing the relative positional relationship between the light beam and the disc track in the intermediate portion of the optical disc, and (d) is the relative positional relationship between the light beam and the disc track in the outer peripheral portion of the optical disc. FIG. It is a schematic sectional drawing of the optical pick-up concerning a prior art. It is sectional drawing which shows the optical integrated unit which concerns on a prior art. It is a schematic diagram which shows the hologram pattern of the polarization hologram element which concerns on a prior art. It is a figure which shows the condensing state of the light beam on the light receiving element which concerns on a prior art. It is a figure which shows the condensing state of the light beam at the time of the spherical aberration error generation | occurrence | production on the light receiving element based on a prior art. (A) is a figure which shows schematic structure of the optical pick-up based on a prior art, (b) is a figure which shows the hologram pattern of the hologram element which concerns on a prior art, (c) is a light receiving element based on a prior art It is a figure which shows the condensing state of the upper light spot.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical integrated unit 2 Collimator lens 3 Objective lens 4 Optical disk 11 Semiconductor laser 12 Light receiving element 14 Polarization beam splitter 16 1/4 wavelength plate 17 Package 20 Light beam 32 Polarization hologram element 33 DVD / CD semiconductor laser 34 Polarization beam splitter 35 Collimator Lens 36 Dichroic mirror 37 DVD / CD rising mirror 38 Condensing lens 39 DVD / CD light receiving element 40 Optical pickup 41 Optical pickup 52 BD rising mirror 53 BD objective lens 54 DVD / CD objective lens 55 Non-diffracting light

Claims (13)

A light source that emits a luminous flux;
Diffractive means for separating the reflected light of the light beam reflected on the optical disc;
A light detecting means having a plurality of light receiving portions for detecting the separated light flux;
An optical surface that transmits the light flux from the light source and reflects the reflected light from the optical disc, and
The diffractive means includes a first boundary line parallel to the radial direction of the optical disc and a second boundary line parallel to the first boundary line, which passes through the optical axis of the reflected light incident on the diffractive means. A first region existing outside the optical axis with respect to the second boundary line, a second region existing between the first boundary line and the second boundary line, A third region present on the opposite side of the first region and the second region with respect to the first boundary line;
The third region is divided by a third boundary line parallel to the first boundary line into a fourth region including the optical axis and a fifth region not including the optical axis;
The distance between the first boundary line and the second boundary line is 70 % or more of the effective radius of the light beam incident on the diffraction means;
The distance between the first boundary line and the third boundary line is 70 % or more of the effective radius of the light beam incident on the diffractive means, and the first boundary line and the second boundary line Equal to the distance
The first region and the fifth region are each divided into two by a fourth boundary line parallel to the track direction of the optical disc passing through the optical axis,
Among the detection result by said light detecting means, each of said first order diffracted light diffracted in the respective detection results and the area of the fifth of + 1st diffracted order diffracted light and -1 order diffracted light in the region and the -1st-order diffracted light Tracking error correction signal generating means for generating a tracking error signal correction signal based only on the detection result of
Of the detection results by the light detection means, the main push-pull signal is detected based on the detection result of the 0th-order diffracted light of the diffraction means,
An optical integrated unit characterized in that a tracking error signal is generated from the detected main push-pull signal and the tracking error signal correction signal generated by the tracking error correction signal generating means . The second region is divided into an inner peripheral region including the optical axis and an outer peripheral region not including the optical axis,
The boundary line between the inner peripheral region and the outer peripheral region is
The first line segment, the second line segment, the third line segment, the fourth line segment, and the fifth line segment are connected in this order,
And a line segment of the first, and the line segment of the third, and the line segment of the fifth optical integrated unit according to claim 1, characterized in that parallel to the first boundary line. The second line segment and the fourth line segment are line symmetric with respect to a straight line passing through the optical axis and parallel to the track direction of the optical disc;
The optical integration according to claim 2 , wherein a distance between the first boundary line and the third line segment is longer than a distance between the first boundary line and the first line segment. unit. The optical integrated unit according to claim 3 , wherein a narrow angle formed by the second line segment and a straight line that intersects the second line segment and parallel to the track direction of the optical disc is 45 °. . To any one of claim 1 to 4, further comprising a focus error signal generating means for generating a focus error signal based on a detection result by the light detecting means of the light beam diffracted at the third region The optical integrated unit described. Any claims 2 to 4, characterized in that it further comprises a focus error signal generating means for generating a focus error signal based on a detection result by the light detecting means of the light beam diffracted at the third region and the peripheral region An optical integrated unit according to claim 1. Of claims 2 to 4, further comprising a spherical aberration error signal generator generating a spherical aberration error signal based on a detection result by the light detecting means of the light beam diffracted at the inner peripheral region and the outer peripheral region The optical integrated unit according to any one of claims. To any one of claims 2 to 4, further comprising a spherical aberration error signal generator generating a spherical aberration error signal based on a detection result by the light detecting means of the light beam diffracted in the outer peripheral region The optical integrated unit described. The diffractive means has a polarization characteristic whose diffraction efficiency varies depending on the polarization of the light beam, and the polarization characteristic is set so that the light beam from the light source is not diffracted by the diffractive means. The optical integrated unit according to any one of claims 1 to 8 . An optical pickup characterized in that it comprises an integrated optical unit according to any one of claims 1-8. In an optical pickup that includes at least two objective lenses and performs at least one of recording and reproduction of information on at least two types of optical discs,
An optical pickup comprising at least one optical integrated unit according to any one of claims 1 to 8 . The optical pickup according to claim 11 , wherein a straight line through which a focal point where light emitted from at least one of the optical integrated units is connected to the optical disc passes obliquely with respect to a track of the optical disc. A light source that emits a luminous flux;
Diffractive means for separating the reflected light of the light beam reflected on the optical disc;
A light detecting means having a plurality of light receiving portions for detecting the separated light flux;
An optical surface that transmits the light flux from the light source and reflects the reflected light from the optical disc, and
The diffractive means includes a first boundary line parallel to the radial direction of the optical disc and a second boundary line parallel to the first boundary line, which passes through the optical axis of the reflected light incident on the diffractive means. A first region existing outside the optical axis with respect to the second boundary line, a second region existing between the first boundary line and the second boundary line, A third region present on the opposite side of the first region and the second region with respect to the first boundary line;
The third region is divided by a third boundary line parallel to the first boundary line into a fourth region including the optical axis and a fifth region not including the optical axis;
The distance between the first boundary line and the second boundary line is 70 % or more of the effective radius of the light beam incident on the diffraction means;
The distance between the first boundary line and the third boundary line is 70 % or more of the effective radius of the light beam incident on the diffractive means, and the first boundary line and the second boundary line Equal to the distance
The first region and the fifth region are each divided into two by a fourth boundary line parallel to the track direction of the optical disc passing through the optical axis,
Among the detection result by said light detecting means, each of said first order diffracted light diffracted in the respective detection results and the area of the fifth of + 1st diffracted order diffracted light and -1 order diffracted light in the region and the -1st-order diffracted light Tracking error correction signal generating means for generating a tracking error signal correction signal based only on the detection result of
Of the detection results by the light detection means, the main push-pull signal is detected based on the detection result of the 0th-order diffracted light of the diffraction means,
An optical pickup device that generates a tracking error signal from the detected main push-pull signal and the correction signal of the tracking error signal generated by the tracking error correction signal generation means .

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