JP2014157636A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of smoothly reducing influence of stray light and also suppressing the deterioration of a detection signal due to shift of an objective lens.SOLUTION: A spectroscopic element H2 has diffraction regions H2a to H2g. Laser beams incident on the diffraction regions H2a to H2f are diffracted in directions Da, Vb, Vc, Dd, Vf, Vg, respectively. A laser beam incident on the diffraction region H2g is diffracted so as not to be incident on a sensor portion of a photo-detector. The diffraction region H2g is configured such that the length y3 thereof in the vertical direction is larger than the length x thereof in the lateral direction. Thus, in a light receiving surface of the photo-detector, a region irradiated with reflection light from a focused recording layer and a region irradiated with reflection light from recording layers other than the focused recording layer are less likely to overlap each other. Accordingly, interference between signal light and stray light becomes difficult to occur, and thereby the deterioration of a detection signal of the sensor portion can be suppressed.

Description

  The present invention relates to an optical pickup device, and is particularly suitable for use in irradiating a recording medium on which a plurality of recording layers are laminated with laser light.

  In recent years, with the increase in capacity of optical discs, the number of recording layers has been increasing. By including a plurality of recording layers in one disc, the data capacity of the disc can be remarkably increased. In the past, when recording layers were stacked, two single-sided layers were common, but recently, in order to further increase the capacity, a disc having three or more recording layers on one side has been put to practical use. ing. Here, when the number of recording layers is increased, the capacity of the disk can be increased. However, on the other hand, the interval between the recording layers is narrowed, and signal deterioration due to interlayer crosstalk increases.

  When the recording layer is multilayered, the reflected light from the recording layer (target recording layer) to be recorded / reproduced becomes weak. For this reason, when unnecessary reflected light (stray light) is incident on the photodetector from the recording layers above and below the target recording layer, the detection signal may be deteriorated, which may adversely affect the focus servo and tracking servo. Therefore, when a large number of recording layers are arranged in this way, it is necessary to properly remove stray light and stabilize the signal from the photodetector.

  Patent Document 1 below discloses a new configuration of an optical pickup device that can appropriately remove stray light when a large number of recording layers are arranged. According to this configuration, a rectangular region (signal light region) where only signal light exists can be formed on the light receiving surface of the photodetector. The reflected light from the recording medium is irradiated near the apex angle of the signal light region. By arranging the sensor of the photodetector near the apex angle of the signal light region, the influence of stray light on the detection signal can be suppressed.

JP 2009-2111770 A

  In the optical pickup device, although an area where only signal light exists can be formed on the light receiving surface of the photodetector, the area irradiated with the signal light and the area irradiated with the stray light are adjacent to each other. For this reason, if the objective lens is shifted with respect to the laser optical axis, the region irradiated with the signal light and the region irradiated with the stray light may overlap and the detection signal may be deteriorated.

  The present invention has been made in view of the above points, and provides an optical pickup device capable of smoothly suppressing the influence of stray light and suppressing deterioration of a detection signal due to shift of an objective lens. Objective.

A main aspect of the present invention relates to an optical pickup device. The optical pickup device according to this aspect is configured to receive a laser light source, an objective lens that converges the laser light emitted from the laser light source on the recording medium, and the laser light reflected by the recording medium. The laser beam is converged in a direction 1 to generate a first focal line, and the laser beam is converged in a second direction perpendicular to the first direction to generate a second focal line. An astigmatism element; a photodetector that receives the laser light that has passed through the astigmatism element; and the first light beam that is reflected by the recording medium and that is not adjacent to each other. The laser light incident on the region and the two second regions sandwiched between the first region are each of four apex angles having different rectangular shapes on the light receiving surface of the photodetector. A spectroscopic element leading to the position and Equipped with a. Here, the photodetector has a sensor unit that receives the laser beam at each of the four apex angles, and the recording medium is projected onto the laser beam incident on the astigmatism element. The direction of the track image forms an angle of 45 degrees with the first and second directions, and the first region is arranged in the direction of the track image across the center of the spectroscopic element. The second region is arranged in a direction perpendicular to the direction of the track image across the center, and a third region that does not guide the laser light to the sensor unit is arranged in the central portion of the spectroscopic element, The length of the third region in the direction perpendicular to the direction of the track image is longer than the length of the third region in the direction of the track image.

  According to the present invention, it is possible to provide an optical pickup device that can smoothly suppress the influence of stray light and suppress the deterioration of the detection signal due to the shift of the objective lens.

  The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely an example for carrying out the present invention, and the present invention is not limited by the following embodiment.

It is a figure explaining the technical principle (convergence state of a light ray) which concerns on embodiment. It is a figure explaining the technical principle (distribution state of a light beam) which concerns on embodiment. It is a figure explaining the technical principle (distribution state of signal light and stray light) concerning an embodiment. It is a figure explaining the technical principle (separation method of a light beam) which concerns on embodiment. It is a figure which shows the arrangement | positioning method of the sensor part which concerns on embodiment. It is a figure which shows the preferable application range of the technical principle which concerns on embodiment. It is a figure explaining the structure of the spectroscopic element (comparative example) based on the technical principle which concerns on embodiment. It is a schematic diagram which shows the irradiation area | region by the spectroscopic element (comparative example) based on the technical principle which concerns on embodiment. It is a figure which shows the simulation result of the irradiation area | region by the spectroscopic element (comparative example) based on the technical principle which concerns on embodiment. It is a figure explaining the structure of the spectroscopic element based on the technical principle which concerns on embodiment. It is a schematic diagram which shows the irradiation area | region by the spectroscopic element based on the technical principle which concerns on embodiment. It is a figure which shows the simulation result of the irradiation area | region by the spectroscopic element based on the technical principle which concerns on embodiment. It is a figure explaining the structure of the spectroscopic element based on the technical principle which concerns on embodiment. It is a schematic diagram which shows the irradiation area | region by the spectroscopic element based on the technical principle which concerns on embodiment. It is a figure which shows the simulation result of the irradiation area | region by the spectroscopic element based on the technical principle which concerns on embodiment. It is a figure which shows the optical system of the optical pick-up apparatus which concerns on an Example. It is a figure which shows the sensor layout of the photodetector which concerns on an Example. It is a figure which shows the example of a change of the spectroscopic element which concerns on an Example. It is a figure which shows the example of a change of the diffraction area formed in the center part of the spectroscopic element which concerns on an Example.

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

<Technical principle>
First, the technical principle applied to this embodiment will be described with reference to FIGS.

  FIGS. 1A and 1B are diagrams for explaining the convergence state of light rays. FIG. 1A shows a laser beam (signal light) reflected by the target recording layer, a laser beam (stray light 1) reflected by a layer deeper than the target recording layer, and a layer shallower than the target recording layer. It is a figure which shows the convergence state of a laser beam (stray light 2). FIG. 1B is a diagram showing a configuration of an anamorphic lens used in the present principle.

  Referring to FIG. 1B, the anamorphic lens imparts a converging action in the curved surface direction and the planar direction to the laser light incident in parallel to the lens optical axis. Here, the curved surface direction and the planar direction are orthogonal to each other. Further, the curved surface direction has a smaller radius of curvature than the planar direction, and has a large effect of converging the laser light incident on the anamorphic lens.

  Here, in order to simply explain the astigmatism action in the anamorphic lens, for the sake of convenience, they are expressed as “curved surface direction” and “planar direction”, but in reality, the action of connecting the focal lines to different positions. However, the shape of the anamorphic lens in the “planar direction” in FIG. 1B is not limited to a plane. When laser light is incident on the anamorphic lens in a convergent state, the shape of the anamorphic lens in the “plane direction” can be a straight line (curvature radius = ∞).

  Referring to FIG. 1A, the signal light converged by the anamorphic lens forms focal lines at different positions due to convergence in the curved surface direction and the planar direction. The focal line position (S1) due to the convergence in the curved surface direction is closer to the anamorphic lens than the focal line position (S2) due to the convergence in the planar direction, and the convergence position (S0) of the signal light is the focal position in the curved surface direction and the planar direction. This is an intermediate position between the line positions (S1) and (S2).

  Similarly, for the stray light 1 converged by the anamorphic lens, the focal line position (M11) due to convergence in the curved surface direction is closer to the anamorphic lens than the focal line position (M12) due to convergence in the planar direction. The anamorphic lens is designed such that the focal line position (M12) due to the convergence of the stray light 1 in the plane direction is closer to the anamorphic lens than the focal line position (S1) due to the convergence of the signal light in the curved surface direction.

  Similarly, for the stray light 2 converged by the anamorphic lens, the focal line position (M21) due to convergence in the curved surface direction is closer to the anamorphic lens than the focal line position (M22) due to convergence in the plane direction. The anamorphic lens is designed such that the focal line position (M21) due to convergence of the stray light 2 in the curved surface direction is farther from the anamorphic lens than the focal line position (S2) due to convergence of the signal light in the planar direction.

  Further, at the convergence position (S0) between the focal line position (S1) and the focal line position (S2), the beam of signal light becomes a minimum circle of confusion.

  Considering the above, the relationship between the irradiation area of the signal light and the stray lights 1 and 2 on the surface S0 will be examined.

Here, as shown in FIG. 2A, the anamorphic lens is divided into four regions A to D. In this case, the signal light incident on the areas A to D is distributed as shown in FIG. 2B on the surface S0. Further, the stray light 1 incident on the regions A to D is distributed on the surface S0 as shown in FIG. The stray light 2 incident on the areas A to D is distributed on the surface S0 as shown in FIG.

  Here, when the signal light and the stray lights 1 and 2 on the surface S0 are extracted for each light flux region, the distribution of each light is as shown in FIGS. In this case, the stray light 1 and the stray light 2 in the same light flux region do not overlap with the signal light in each light flux region. For this reason, when the light beams (signal light, stray light 1 and 2) in each light beam region are dispersed in different directions and then only the signal light is received by the sensor unit, the corresponding sensor unit receives the signal light. Only incident light can be input, and the incidence of stray light can be suppressed. Thereby, degradation of the detection signal due to stray light can be avoided.

  Thus, only the signal light can be extracted by dispersing the light passing through the regions A to D and separating them on the surface S0. The present embodiment is based on this principle.

  4 (a) and 4 (b) show the traveling directions of the light beams (signal light, stray light 1 and 2) passing through the four regions A to D shown in FIG. 2 (a) in different directions by the same angle. It is a figure which shows the distribution state of the signal light and the stray lights 1 and 2 on the surface S0 when it is changed. 4A is a view of the anamorphic lens viewed from the optical axis direction of the anamorphic lens (the traveling direction of the laser light when the anamorphic lens is incident), and FIG. 4B is a distribution state of the signal light and stray light 1 and 2 on the surface S0. FIG.

  In FIG. 4A, the traveling directions of the light beams (signal light, stray light 1 and 2) that have passed through the regions A to D are the directions Da, Db, Dc, Dd changes by the same angular amount α (not shown). The directions Da, Db, Dc, and Dd have an inclination of 45 degrees with respect to the plane direction and the curved surface direction, respectively.

  In this case, by adjusting the angle amount α in the directions Da, Db, Dc, and Dd, the signal light and the stray lights 1 and 2 in each light flux region are distributed on the surface S0 as shown in FIG. Can do. As a result, as shown in the figure, it is possible to set a signal light region where only signal light exists on the surface S0. By arranging a plurality of sensor portions of the photodetector in this signal light region, only the signal light in each region can be received by the corresponding sensor portion.

  FIGS. 5A to 5D are diagrams illustrating a method for arranging the sensor units. FIG. 5A is a diagram showing a light flux region of the reflected light (signal light) from the disk, and FIG. 5B shows the arrangement position of the anamorphic lens and the surface S0 in the configuration of FIG. It is a figure which shows the distribution state of the signal beam | light on a photodetector when each arrange | positions the anamorphic lens and the photodetector (4-part dividing sensor) based on the conventional astigmatism method. FIGS. 5C and 5D are diagrams showing a signal light distribution state and a sensor layout based on the above-described principle on the surface S0.

  The direction of the signal light diffraction image (track image) by the track groove has an inclination of 45 degrees with respect to the plane direction and the curved surface direction. In FIG. 5A, assuming that the direction of the track image is the left-right direction, in FIG. 5B to FIG. 5D, the direction of the track image in the signal light is the vertical direction. In FIG. 5A, for convenience of explanation, the light beam is divided into eight light beam regions a to h. FIGS. 5B and 5D correspond to the light beam regions a to h, respectively. Illumination areas a to h on the sensor unit are shown. Further, the track image is indicated by a solid line, and the beam shape at the time of off-focus is indicated by a dotted line.

It is known that the overlapping state of the 0th-order diffraction image and the first-order diffraction image of the signal light by the track groove is obtained by wavelength / (track pitch × objective lens NA), and FIGS. 5 (a) and 5 (b). , (D), the condition that the first-order diffraction image fits in the four light flux regions a, d, e, and h is the wavelength /
(Track pitch × objective lens NA)> √2.

In the conventional astigmatism method, the sensor portions P1 to P4 (four-divided sensors) of the photodetector are set as shown in FIG. In this case, when the detection signal components based on the light intensity of the light flux areas a to h are represented by A to H, the focus error signal FE and the push-pull signal PP are
FE = (A + B + E + F) − (C + D + G + H) (1)
PP = (A + B + G + H)-(C + D + E + F) (2)
It is obtained by the operation of

  On the other hand, in the distribution state of FIG. 4B, the signal light is distributed in the state of FIG. 5C in the signal light region as described above. In this case, the signal light passing through the light flux areas a to h shown in FIG. 5A is as shown in FIG. That is, the signal light passing through the light flux areas a to h in FIG. 5A is guided to the irradiation areas a to h shown in FIG. 5D on the surface S0 on which the sensor unit of the photodetector is placed.

  Therefore, if the sensor parts P11 to P18 are arranged at the positions of the irradiation areas a to h shown in FIG. 5D so as to overlap with each other in FIG. 5D, the same arithmetic processing as in the case of FIG. Thus, a focus error signal and a push-pull signal can be generated. That is, also in this case, when the detection signals from the sensor units that receive the light beams in the light beam regions a to h are represented by A to H, the focus error signal FE and the push-pull signal PP are expressed as in FIG. , And can be obtained by the calculations of the above formulas (1) and (2).

  As described above, according to the present principle, the focus error signal and the push-pull signal (tracking error signal) in which the influence of stray light is suppressed are generated by the same arithmetic processing based on the conventional astigmatism method. be able to.

  As shown in FIG. 6, the effect of the above principle is that the focal line position of the stray light 1 in the plane direction is closer to the anamorphic lens than the surface S0 (the surface where the spot of the signal light is the minimum circle of confusion) In addition, this can be achieved when the focal line position of the stray light 2 in the curved surface direction is farther from the anamorphic lens than the surface S0. That is, if this relationship is satisfied, the distribution of the signal light and the stray lights 1 and 2 is in the state shown in FIG. 4B, and the signal light and the stray lights 1 and 2 are not overlapped on the plane S0. Can do. In other words, as long as this relationship is satisfied, the focal line position in the plane direction of the stray light 1 is closer to the plane S0 than the focal line position in the curved surface direction of the signal light, or the focal line in the plane direction of the signal light is Even if the focal line position in the curved surface direction of the stray light 2 rather than the position approaches the surface S0, the effect based on the above principle can be achieved.

<Spectroscopic element H0>
When the areas A to D are configured as shown in FIG. 4A, ideally, an area where only signal light is generated (signal light area) can be generated. However, in the configuration of FIG. 4A, since the signal light and the stray light are close to each other as shown in FIG. 4B, a part of the stray light is actually applied to the signal light. Can interfere with each other. Further, in the configuration of FIG. 4A, it is possible that the signal light is not properly incident on each sensor unit when a positional deviation occurs in the photodetector. Such a problem can be suppressed by adjusting the shape of the regions A to D and the traveling direction of light incident on each region.

  FIGS. 7A to 7C are diagrams illustrating the configuration of a spectroscopic element H0 (comparative example) for suppressing the above problem.

FIG. 7A is a plan view when the spectroscopic element H0 is viewed from the anamorphic lens side shown in FIGS. 1A and 1B. FIG. 7A shows the planar direction and curved surface direction of the anamorphic lens in FIG. 1B and the direction of the track image of the laser light incident on the spectroscopic element H0. FIG. 7B is an enlarged view of the diffraction region H0i. FIG. 7C is a diagram showing light beam regions a0 to i0 obtained by dividing the laser light incident on the spectroscopic element H0 so as to correspond to the boundary lines of the diffraction regions of the spectroscopic element H0.

  Details of the configuration, operation, and effect of the spectroscopic element H0 are described in Japanese Patent Application No. 2011-038890 filed earlier by the present applicant.

  The spectroscopic element H0 is formed of a square-shaped transparent plate, and a diffraction pattern (diffraction hologram) is formed on the light incident surface. As shown in FIG. 7A, the light incident surface of the spectroscopic element H0 is divided into nine diffraction regions H0a to H0i. The diffraction regions H0a, H0d, H0e, and H0h have the same area, and the diffraction regions H0b, H0c, H0f, and H0g have the same area. The diffraction region H0i is formed in the central portion of the spectroscopic element H0. The direction of the track image forms an angle of 45 degrees with the plane direction and the curved surface direction of the anamorphic lens.

  The diffraction regions H0a to H0h diffract the incident laser light in directions Va to Vh, respectively, by a diffraction action. In the directions Va and Vh, components in the downward direction and the upward direction are slightly added from the direction Da in FIG. Similarly, in the directions Vf and Vg, components in the left direction and the right direction are slightly added from the direction Db in FIG. Further, in the directions Vb and Vc, components in the right direction and the left direction are slightly added from the direction Dc in FIG. Further, in the directions Vd and Ve, the components in the downward direction and the upward direction are slightly added from the direction Dd in FIG.

  The boundary lines of the diffraction regions H0a, H0d, H0e, H0h and the diffraction regions H0b, H0c, H0f, H0g have a straight line portion p1 extending in the vertical direction, and the boundary lines other than the straight line portion p1 are as shown in the figure. It is a straight line having an angle of 45 degrees with respect to the vertical and horizontal directions.

  The diffraction region H0i is set so that the laser beam incident on this region does not irradiate the sensor parts P11 to P18 and irradiates a place away from the sensor parts P11 to P18 by the diffraction action.

  Further, as shown in FIG. 7B, the diffraction region H0i has a straight line portion k1 at the boundary lines with the diffraction regions H0b and H0c and the boundary lines with the diffraction regions H0f and H0g, and the diffraction regions H0a and H0h. And the boundary lines with the diffraction regions H0d and H0e have a straight line portion k2. Further, the lengths of the diffraction region H0i in the horizontal direction and the vertical direction are x and y1, respectively. The diffraction region H0i is configured such that the aspect ratio (y1 / x) is smaller than 1.

  The thus configured spectroscopic element H0 is arranged so that the optical axis of the laser beam passes through the center, and the light beams in the light beam areas a0 to i0 shown in FIG. 7C respectively enter the diffraction areas H0a to H0i. Incident.

  FIG. 8A is a schematic diagram illustrating an irradiation region when signal light passing through the light beam regions a0 to h0 in FIG. 7C is irradiated to the sensor units P11 to P18 via the spectroscopic element H0. Note that the irradiation areas of the signal light passing through the light flux areas a0 to h0 are indicated as irradiation areas a0 to h0.

  As shown in FIG. 8A, the signal light passing through the light flux areas a0 to h0 is irradiated to the sensor portions P11, P16, P14, P17, P18, P13, P15, and P12, respectively. Further, the signal light passing through the light beam region i0 is irradiated to a position (not shown) that is greatly separated from the signal light region.

  Further, as shown in FIG. 8A, two irradiation areas (for example, irradiation areas a0 and h0) in the apex portion of the signal light area are separated from each other by a certain distance. Furthermore, a predetermined gap exists between two sensor portions (for example, P11 and P12) arranged at each apex angle portion. The gap between the two irradiation areas at the apex angle portion is larger than the gap between the two corresponding sensor parts. As described above, the gap between the irradiation regions is set by slightly including components in the vertical direction or the horizontal direction in the directions Va to Vh.

  Even when the sensor portions P11 to P18 are displaced in the vertical and horizontal directions within the surface S0 (see FIG. 1A) due to such a gap, the irradiation areas a0 to h0 are positioned in the sensor portions P11 to P18. It becomes easy to be done.

  8B and 8C show the irradiation areas when the stray lights 1 and 2 passing through the light beam areas a0 to h0 in FIG. 7C are irradiated to the sensor parts P11 to P18 via the spectroscopic element H0. It is a schematic diagram shown.

  As shown in FIGS. 8B and 8C, the stray lights 1 and 2 passing through the light flux areas a0 to h0 are irradiated outside the signal light area. Further, the stray lights 1 and 2 passing through the light beam area i0 are irradiated to a position (not shown) that is far away from the signal light area. Note that a part of the irradiation areas b0 and f0 in FIG. 8B and a part of the irradiation areas c0 and g0 in FIG. 8C overlap the sensor unit. By setting the size of the sensor layout, the size of the diffraction region H0i, and the like, the stray light that overlaps the sensor portion can be reduced.

  Further, as described above, the signal light and stray light 1 and 2 incident near the center of the spectroscopic element H0 are not irradiated in the vicinity of the signal light region by the diffraction region H0i. As a result, both the signal light and the stray light are irradiated near the left end of the sensor units P11 and P12, near the lower end of the sensor units P13 and P15, near the upper end of the sensor units P14 and P16, and near the right end of the sensor units P17 and P18. Disappear. Therefore, since it becomes difficult for signal light and stray light to mutually overlap, it can control that signal light and stray light interfere with each other.

  As described above, by using the spectroscopic element H0 (comparative example), interference between the signal light and the stray light is suppressed, and the sensor parts P11 to P18 are within the plane S0 (see FIG. 1A). Even when positional deviation occurs vertically and horizontally, the irradiation areas a0 to h0 are easily positioned in the sensor portions P11 to P18.

  However, according to the spectroscopic element H0 (comparative example), the following problems further occur.

  FIGS. 9A to 9C are diagrams illustrating simulation results of the irradiation area of the signal light and stray light on the sensor layout when the spectroscopic element H0 is used.

  FIG. 9A shows an irradiation area when there is no deviation between the optical axis of the laser beam toward the recording layer and the optical axis of the objective lens (no lens shift), and FIGS. 9B and 9C. These show irradiation regions when there is a shift in the tracking direction (with lens shift) between the optical axis of the laser beam toward the recording layer and the optical axis of the objective lens. FIG. 9C is an enlarged view of two sensor units corresponding to the sensor units P17 and P18 in FIG. 9B. In this simulation, the aspect ratio (y1 / x) of the diffraction region H0i is set to 0.64.

9 (a) to 9 (c), as shown in FIG. 9 (d), a laser beam is incident from the surface side to a disk having a recording layer of L0 to L3 layers, and the L2 layer is formed by an objective lens. The case where the focus of the laser beam is positioned is shown. In FIGS. 9A to 9C, symbols indicating the irradiation areas of the reflected light from the L0 layer to the L3 layer are also shown, as shown in FIG. 9D. In addition,
In FIGS. 9A to 9C, since the symbol indicating the irradiation region of the L2 layer is small and overlaps with each other, the irradiation region of the L2 layer is marked with “signal light” by an arrow.

  When there is no lens shift, the signal light (reflected light from the L2 layer) and stray light (reflected light from the L0, L1, and L3 layers) do not substantially overlap as shown in FIG. However, when there is a lens shift, as shown in FIG. 9B, the irradiation areas of the signal light and the stray light overlap each other. Referring to FIG. 9C, in the two sensor units corresponding to the sensor units P17 and P18, the signal light (reflected light from the L2 layer) is stray light (reflected light from the L0, L1, and L3 layers). You can see that they overlap.

  Thus, when there is a lens shift, the signal light and the stray light interfere with each other because the irradiation areas of the signal light and the stray light overlap each other. Such interference between the signal light and the stray light causes the detection signal of the sensor unit to deteriorate, and there is a possibility that various signals generated based on the detection signal of the sensor unit may fluctuate. Such fluctuation has a great influence especially on a tracking error signal (push-pull signal), and there is a possibility that it may prevent proper detection of a track.

<Spectroscopic element H1>
In the spectroscopic element H0, when there is a lens shift, the signal light and the stray light interfere with each other, causing the detection signal to deteriorate. In order to solve this problem, the following configuration can be used. This configuration is one embodiment of the present invention.

  FIG. 10A is a plan view when the spectroscopic element H1 is viewed from the anamorphic lens side shown in FIGS. 1A and 1B. FIG. 10B is an enlarged view of the diffraction region H1g. FIG. 10C is a diagram showing light beam regions a1 to g1 obtained by dividing the laser light incident on the spectroscopic element H1 so as to correspond to the boundary lines of the diffraction regions of the spectroscopic element H1.

  As shown in FIG. 10A, the light incident surface of the spectroscopic element H1 is divided into seven diffraction regions H1a to H1g. The spectroscopic element H1 has a configuration in which the diffraction areas H0a and H0h are integrated from the spectroscopic element H0, and the diffraction areas H0d and H0e are integrated. The diffraction regions H1a and H1d diffract the incident laser light in directions Da and Dd (see FIG. 4A), respectively, by diffraction. The diffraction region H1g has a configuration in which the shape of the straight line portion k2 is different from the diffraction region H0i of the spectroscopic element H0.

  As shown in FIG. 10B, the diffraction region H1g has a straight line portion k1 at the boundary lines with the diffraction regions H1b and H1c and the boundary lines with the diffraction regions H1e and H1f, as with the spectroscopic element H0. A curved line k3 is provided at the boundary line with the diffraction regions H1a and H1d. Thereby, protrusions H1ga and H1gb are formed at the upper and lower portions of the diffraction region H1g. The lengths of the diffraction region H1g in the left-right direction and the up-down direction are x and y2, respectively. The diffraction region H1g is configured such that y2> x and the aspect ratio (y2 / x) is greater than 1.

  Fig.11 (a) is a schematic diagram which shows an irradiation area | region when the signal light which passes the light beam area | region a1-f1 of FIG.10 (c) is irradiated to the sensor parts P11-P18 via the spectroscopic element H1. In addition, the irradiation area | region of the signal light which passes light beam area | region a1-f1 is shown as irradiation area | region a1-f1.

  As shown in FIG. 11A, the signal light passing through the light flux region a1 is applied to the sensor portions P11 and P12, and the signal light passing through the light flux region d1 is applied to the sensor portions P17 and P18, and the light flux regions b1 and c1. , E1, and f1 are irradiated to P16, P14, P13, and P15, respectively. Further, the signal light passing through the light flux region g1 is irradiated to a position (not shown) that is greatly separated from the signal light region.

  In this case, the areas irradiated with the sensor parts P11 and P12 and the sensor parts P17 and P18 (irradiation areas a1 and d1) are different from the case where the spectroscopic element H0 is used, at the boundary between the two sensor parts arranged vertically. There is no corresponding gap. For this reason, when the sensor units P11 to P18 are displaced in the vertical direction within the surface S0 (see FIG. 1A), the detection signals of the sensor units P11, P12, P17, and P18 change. However, in the calculation of the push-pull signal PP shown in the above equation (1), the detection signals of the sensor units P11 and P12 and the detection signals of the sensor units P17 and P18 are added, so that the sensor units P11 to P18 move up and down. Even if the direction is shifted, the calculation result of the push-pull signal PP is not substantially affected. Therefore, a good push-pull signal PP can be obtained without dividing the diffraction regions H1a and H1d into two parts on the left and right as in the spectroscopic element H0.

  FIGS. 11B and 11C show irradiation areas when stray lights 1 and 2 passing through the light beam areas a1 to f1 in FIG. 10C are irradiated to the sensor portions P11 to P18 through the spectroscopic element H1. It is a schematic diagram shown. As shown in the figure, the stray lights 1 and 2 are irradiated outside the signal light region in the same manner as the spectral element H0. Thereby, it becomes difficult for signal light and stray light to overlap each other.

  Further, as shown in FIG. 11B, indentations corresponding to the curved portion k3 shown in FIG. 10B are formed in the upper portion of the stray light 1 irradiation region a1 and the lower portion of the stray light 1 irradiation region d1. ing. Similarly, as shown in FIG. 11C, indentations corresponding to the curved portion k3 shown in FIG. 10B are formed in the lower portion of the irradiation region a1 of the stray light 2 and the upper portion of the irradiation region d1 of the stray light 2. Has been.

  FIGS. 12A to 12C are diagrams showing simulation results of the signal light and stray light irradiation areas on the sensor layout when the spectroscopic element H1 is used.

  FIG. 12A shows an irradiation area when there is no objective lens shift (no lens shift), and FIGS. 12B and 12C show irradiation when there is an objective lens shift (with a lens shift). Indicates the area. FIG.12 (c) is the figure which expanded the two sensor parts corresponding to sensor part P17, P18 in FIG.12 (b). Also in this case, as in the case of using the spectroscopic element H0, as shown in FIG. 12 (d), a disk is formed, and the focal point of the laser beam is positioned on the L2 layer. In this simulation, the aspect ratio (y2 / x) of the diffraction region H1g is set to 1.2.

  Referring to FIGS. 12A and 12B, signal light (reflected light from the L2 layer) and stray light (reflected light from the L0, L1, and L3 layers) are substantially overlapped regardless of the presence or absence of lens shift. Don't be. Further, since the diffraction region H1g of the spectroscopic element H1 is larger than the diffraction region H0i of the spectroscopic element H0, as shown in the drawing, the stray light irradiation region in the vicinity of the sensor layout is compared with FIGS. 9 (a) and 9 (b). It is getting smaller.

  Referring to FIG. 12C, in the two sensor units corresponding to the sensor units P17 and P18, the signal light (reflected light from the L2 layer) is stray light (reflected light from the L0, L1, and L3 layers). It can be seen that there is almost no overlap. Here, a depression corresponding to the curved portion k3 shown in FIG. 10B is formed along the line L1 above the irradiation region d1 of the stray light 2 (reflected light from the L0 layer). The signal light and the stray light 2 are not easily overlapped by the depression corresponding to the curved portion k3. Similarly, referring to FIG. 12B, a depression corresponding to the curved portion k3 is formed along the line L2 below the stray light 1 (reflected light from the L0 and L1 layers) irradiation region d1. Yes. Also in this case, the signal light and the stray light 1 are not easily overlapped by the depression corresponding to the curved portion k3.

As described above, when the spectroscopic element H1 is used, the signal light irradiation region and the stray light irradiation region hardly overlap each other regardless of the presence or absence of the lens shift, so that the signal light and the stray light hardly interfere with each other. Deterioration of the detection signal can be suppressed.

<Spectroscopic element H2>
The spectroscopic element H2 is obtained by changing the shape of the diffraction region H1g at the center of the spectroscopic element H1. This configuration is also one embodiment of the present invention.

  FIG. 13A is a plan view of the spectroscopic element H2 when viewed from the anamorphic lens side shown in FIGS. 1A and 1B. FIG. 13B is an enlarged view of the diffraction region H2g. FIG. 13C is a diagram showing light beam regions a2 to g2 obtained by dividing the laser light incident on the spectroscopic element H2 so as to correspond to the boundary lines of the diffraction regions of the spectroscopic element H1.

  As shown in FIG. 13A, the light incident surface of the spectroscopic element H2 is divided into seven diffraction regions H2a to H2i, similar to the spectroscopic element H1. As shown in FIG. 13 (b), the diffraction region H2g has a straight line portion k1 at the boundary line with the diffraction regions H2b and H2c and the boundary line with the diffraction regions H2e and H2f, as in the spectral element H1. A straight line portion k4 and a curved line portion k5 are provided at the boundary line between the diffraction regions H2a and H2d. Thereby, protrusions H2ga and H2gb are formed at the upper and lower portions of the diffraction region H2g. Moreover, the length of the diffraction area H2g in the left-right direction and the up-down direction is x and y3, respectively. The diffraction region H2g is configured such that y3> x and the aspect ratio (y3 / x) is greater than 1.

  FIG. 14A is a schematic diagram illustrating an irradiation region when signal light passing through the light beam regions a2 to f2 of FIG. 13C is irradiated to the sensor units P11 to P18 via the spectroscopic element H2. In addition, the irradiation area | region of the signal light which passes light beam area | region a2-f2 is shown as irradiation area | region a2-f2.

  As shown in the figure, the signal light passing through the light flux regions a2 to f2 is applied to the sensor portions P11 to P18 as in the case of the spectroscopic element H1. Further, the signal light passing through the light flux region g2 is irradiated to a position (not shown) that is greatly separated from the signal light region.

  FIGS. 14B and 14C show irradiation areas when stray lights 1 and 2 passing through the light beam areas a2 to f2 of FIG. 13C are irradiated to the sensor portions P11 to P18 via the spectroscopic element H2. It is a schematic diagram shown. As shown in the figure, the stray lights 1 and 2 are irradiated to the outside of the signal light region in the same manner as the spectral element H1.

  Similarly to the spectroscopic element H1, depressions corresponding to the curved portion k5 shown in FIG. 13B are formed in the upper portion of the stray light 1 irradiation region a2 and the lower portion of the stray light 1 irradiation region d2. Similarly, indentations corresponding to the curved portion k5 shown in FIG. 13B are formed below the stray light 2 irradiation region a2 and above the stray light 2 irradiation region d2.

  FIGS. 15A to 15C are diagrams showing simulation results of the signal light and stray light irradiation areas on the sensor layout when the spectroscopic element H2 is used. Also in this case, as in the case where the spectroscopic element H1 is used, as shown in FIG. 15D, a disk is formed, and the focal point of the laser beam is positioned on the L2 layer. In this simulation, the aspect ratio (y3 / x) of the diffraction region H2g is set to 1.6.

Referring to FIGS. 15A and 15B, similarly to the spectroscopic element H1, signal light (reflected light from the L2 layer) and stray light (from the L0, L1, and L3 layers) regardless of the presence or absence of lens shift. (Reflected light) does not substantially overlap. Further, since the diffraction region H2g of the spectroscopic element H1 is larger than the diffraction region H0i of the spectroscopic element H0, as shown in the drawing, the stray light irradiation region in the vicinity of the sensor layout is compared with FIGS. 9 (a) and 9 (b). It is getting smaller.

  Referring to FIG. 15C, in the two sensor units corresponding to the sensor units P17 and P18, the signal light (reflected light from the L2 layer) is stray light (reflected light from the L0, L1, and L3 layers). It can be seen that there is almost no overlap. Here, a depression corresponding to the curved portion k5 shown in FIG. 13B is formed along the line L3 above the irradiation region d1 of the stray light 2 (reflected light from the L0 layer). Similarly, referring to FIG. 15B, a depression corresponding to the curved portion k5 is formed along the line L4 below the stray light 1 (reflected light from the L0 and L1 layers) irradiation region d1. Yes. Also in this case, similarly to the spectroscopic element H1, the signal light irradiation region and the stray light irradiation region hardly overlap each other regardless of the presence or absence of the lens shift, so that the signal light and the stray light hardly interfere with each other. Deterioration of the detection signal can be suppressed.

  Further, the depression corresponding to the curved portion k5 formed in the irradiation region of the stray light 1 and 2 is shown in the lines L3 and L4 as compared with the case of the spectral element H1 (see FIGS. 12B and 12C). As shown, the shape is in accordance with the shape of the signal light irradiation region. Thereby, compared with the said spectroscopic element H1, signal light and stray light become difficult to overlap further. Further, since the curved portion k5 is formed along the signal light irradiation region, the signal light diffracted outside the signal light region by the diffraction region H2g is reduced as compared with the spectroscopic element H1, and the sensor unit P11. The signal light is easily collected at ~ P18.

  In the following examples, specific configuration examples of an optical pickup device using the spectral element H2 are shown.

<Example>
In this embodiment, the present invention is applied to a compatible optical pickup device that can handle BD, DVD, and CD. The above principle is applied only to the optical system for BD, and the focus adjustment technique by the conventional astigmatism method and the tracking adjustment technique by the three-beam method (in-line method) are applied to the optical system for CD and the optical system for DVD. Has been applied.

  FIGS. 16A and 16B are diagrams illustrating an optical system of the optical pickup device according to the present embodiment. FIG. 16A is a plan view of the optical system in which the configuration on the disk side of the rising mirrors 114 and 115 is omitted, and FIG. 16B is a perspective view of the optical system after the rising mirrors 114 and 115 from the side. FIG.

  As illustrated, the optical pickup device includes a semiconductor laser 101, a half-wave plate 102, a diverging lens 103, a two-wavelength laser 104, a diffraction grating 105, a diverging lens 106, a composite prism 107, Front monitor 108, collimator lens 109, drive mechanism 110, reflection mirrors 111 and 112, quarter-wave plate 113, rising mirrors 114 and 115, two-wavelength objective lens 116, and BD objective lens 117 , A spectroscopic element H3, an anamorphic lens 118, and a photodetector 119.

  The semiconductor laser 101 emits BD laser light (hereinafter referred to as “BD light”) having a wavelength of about 405 nm. The half-wave plate 102 adjusts the polarization direction of the BD light. The diverging lens 103 adjusts the focal length of the BD light so as to shorten the distance between the semiconductor laser 101 and the composite prism 107.

  The two-wavelength laser 104 has two laser elements that respectively emit a laser beam for CD having a wavelength of about 785 nm (hereinafter referred to as “CD light”) and a laser beam for DVD having a wavelength of about 660 nm (hereinafter referred to as “DVD light”). Are accommodated in the same CAN.

  FIG. 16C is a diagram showing an arrangement pattern of laser elements (laser light sources) in the two-wavelength laser 104. FIG. 16C shows the two-wavelength laser 104 viewed from the beam emission side. In FIG. 16C, CE and DE indicate the emission points of CD light and DVD light, respectively. The gap between the emission points of CD light and DVD light is G.

  Note that the gap G between the light emission point CE of the CD light and the light emission point DE of the DVD light is set so that the DVD light is appropriately applied to the four-divided sensor for DVD light, as will be described later. Thus, by accommodating two light sources in the same CAN, the optical system can be simplified as compared with the configuration of a plurality of CAN.

  Returning to FIG. 16A, the diffraction grating 105 divides CD light and DVD light into a main beam and two sub beams, respectively. The diffraction grating 105 is a two-step step type diffraction grating. The diffraction grating 105 is integrated with a half-wave plate. The polarization direction of the CD light and the DVD light is adjusted by the integrated half-wave plate. The diverging lens 106 adjusts the focal lengths of the CD light and the DVD light so as to shorten the distance between the two-wavelength laser 104 and the composite prism 107.

The composite prism 107 has a dichroic surface 107a and a PBS (Polarizing Beam Splitter) surface 107b inside. The dichroic surface 107a reflects BD light and transmits CD light and DVD light. The semiconductor laser 101, the two-wavelength laser 104, and the composite prism 107 are arranged so that the optical axis of the BD light reflected by the dichroic surface 107a and the optical axis of the CD light transmitted through the dichroic surface 107a are aligned with each other. The optical axis of the DVD light transmitted through the dichroic surface 107a is shifted from the optical axis of the BD light and the CD light by a gap G shown in FIG.

  Each of the BD light, the CD light, and the DVD light is reflected by the PBS surface 107b, and most of the light passes through the PBS surface 107b. In this way, the half-wave plate 102 and the diffraction grating 105 (integrated half-wave plate) are arranged so that a part of the BD light, CD light, and DVD light is reflected by the PBS surface 107b. .

  When the diffraction grating 105 is arranged in this way, the main beam and two sub beams of the CD light, and the main beam and two sub beams of the DVD light are along the tracks of the CD and DVD, respectively. The main beam and the two sub beams of the CD light reflected by the CD are applied to a four-divided sensor for CD on a photodetector 119 described later. The DVD main beam and the two sub-beams reflected by the DVD are applied to a DVD quadrant sensor on a photodetector 119 described later.

  The front monitor 108 is irradiated with the BD light, CD light, and DVD light reflected by the PBS surface 107b. The front monitor 108 outputs a signal corresponding to the amount of received light. A signal from the front monitor 108 is used for output power control of the semiconductor laser 101 and the two-wavelength laser 104.

  The collimator lens 109 converts BD light, CD light, and DVD light incident from the side of the composite prism 107 into parallel light. The drive mechanism 110 moves the collimating lens 109 in the optical axis direction according to the control signal when correcting the aberration. The driving mechanism 110 includes a holder 110a that holds the collimating lens 109, and a gear 110b that sends the holder 110a in the optical axis direction of the collimating lens 109. The gear 110b is connected to a driving shaft of the motor 110c.

The BD light, CD light, and DVD light that have been converted into parallel light by the collimator lens 109 are reflected by the two reflecting mirrors 111 and 112 and enter the quarter-wave plate 113. The quarter-wave plate 113 converts BD light, CD light, and DVD light incident from the reflection mirror 112 side into circularly polarized light, and reflects BD light, CD light, and DVD light incident from the rising mirror 114 side. The light is converted into linearly polarized light orthogonal to the polarization direction when entering from the mirror 112 side. Thereby, the reflected light from the disk is reflected by the PBS surface 107b.

  The rising mirror 114 is a dichroic mirror that transmits BD light and reflects CD light and DVD light in a direction toward the two-wavelength objective lens 116. The rising mirror 115 reflects BD light in a direction toward the BD objective lens 117.

  The two-wavelength objective lens 116 is configured to properly converge the CD light and the DVD light with respect to the CD and the DVD, respectively. The BD objective lens 117 is configured to properly converge the BD light onto the BD. The two-wavelength objective lens 116 and the BD objective lens 117 are driven in the focus direction and the tracking direction by the objective lens actuator 132 while being held by the holder 131.

  The spectroscopic element H2 is the spectroscopic element shown in FIG. Of the BD light, CD light, and DVD light incident on the spectroscopic element H2, the BD light is divided into seven light fluxes, and the traveling direction of each light flux is changed by the diffractive action of the spectroscopic element H2. Most of the CD light and the DVD light are transmitted through the spectroscopic element H2 without being diffracted by the spectroscopic element H2.

  The spectroscopic element H2 is formed of a square-shaped transparent plate, and a step-type diffraction pattern (diffraction hologram) is formed on the light incident surface. The number of steps and the step height of the diffraction pattern are set so that the + 1st order diffraction efficiency with respect to the wavelength of the BD light is increased and the 0th order diffraction efficiency with respect to the wavelengths of the CD light and the DVD light is increased. The diffraction angle is adjusted by the pitch of the diffraction pattern.

  The diffraction regions H2a to H2g of the spectroscopic element H2 are, for example, 8-step diffraction patterns. In this case, the step per step is set to 7.35 μm. Thereby, the diffraction efficiency of the 0th-order diffracted light of the CD light and the DVD light can be set to 99% and 92%, respectively, while the diffraction efficiency of the + 1st-order diffracted light of the BD light is 81%. In this case, the 0th-order diffraction efficiency of BD light is 7%. The CD light and the DVD light are applied to a quadrant sensor, which will be described later, on the photodetector 119 without being substantially diffracted by the diffraction regions H2a to H2g.

  Note that the number of steps of the diffraction pattern arranged in the diffraction regions H2a to H2g can be set to other steps. In addition, the diffraction regions H2a to H2g can be configured by using a technique described in JP-A-2006-73042, for example. If this technique is used, the diffraction efficiency with respect to BD light, CD light, and DVD light can be adjusted further finely.

  The anamorphic lens 118 introduces astigmatism into the BD light, CD light, and DVD light incident from the spectroscopic element H3 side. The anamorphic lens 118 corresponds to the anamorphic lens shown in FIGS. The BD light, CD light, and DVD light transmitted through the anamorphic lens 118 enter the photodetector 119. The photodetector 119 has a sensor layout for receiving each light.

  FIG. 17 is a diagram illustrating a sensor layout of the photodetector 119.

The photodetector 119 is a BD sensor unit B1 to B8 that receives the BD light separated by the spectroscopic element H2, and a CD that receives the CD light that is not separated by the spectroscopic element H2 and passes through the spectroscopic element H2. There are four-divided sensors C01 to C03, and four-divided sensors D01 to D03 for DVD that receive DVD light transmitted through the spectroscopic element H2 without being separated by the spectroscopic element H2. The signal light of the BD light separated by the spectroscopic element H2 is applied to the apex angle portion of the signal light region.

  In addition, although the shape of sensor part B1-B8 is comprised a little different from the shape of sensor part P11-P18 used by the said principle, the effect by sensor part B1-B8 is substantially the same as sensor part P11-P18. The same.

  As shown in the figure, sensor parts B1, B2, sensor parts B3, B5, and sensor part B4 are respectively provided near the four apex angles of the signal light area so that the signal light of the BD light passing through each light beam area can be received. , B6, sensor parts B7, B8 are arranged. The irradiation area of the signal light of the BD light on the sensor parts B1 to B8 is substantially the same as the irradiation area on the sensor parts P11 to P18 shown in FIG.

  Since the optical axes of the BD light and the CD light are aligned by the dichroic surface 107a as described above, the main beam (0th order diffracted light) of the CD light is a signal of the BD light on the light receiving surface of the photodetector 119. Irradiates the center of the light region. The quadrant sensor C01 is arranged at the center position of the main beam of CD light. The quadrant sensors C02 and C03 are arranged on the light receiving surface of the photodetector 119 in the direction of the track image with respect to the main beam so as to receive the sub beam of CD light.

  Since the optical axis of the DVD light is deviated from the optical axis of the CD light as described above, the main beam of the DVD light and the two sub beams are separated from the main beam of the CD light on the light receiving surface of the photodetector 119. Irradiated to a position deviated from one sub-beam. The four-divided sensors D01 to D03 are respectively arranged at the irradiation positions of the main beam and two sub beams of DVD light. The distance between the main beam of CD light and the main beam of DVD light is determined by the gap G between the light emission points of CD light and DVD light shown in FIG.

  As described above, according to the present embodiment, the signal light irradiation area of the BD light is distributed inside the four apex portions of the signal light area as shown in FIG. As shown in FIGS. 14B and 14C, the second irradiation region is distributed outside the signal light region. Therefore, only the signal light of the BD light can be received by the sensor parts B1 to B8 shown in FIG. Thereby, deterioration of the detection signal due to stray light can be suppressed.

  Further, according to the present embodiment, the diffraction region H2g of the spectroscopic element H2 has the curved portion k5 at the boundary between the diffraction regions H2a and H2d, so that the signal light irradiation region and the stray light 1 and 2 irradiation regions do not easily overlap. Become. Thereby, it becomes difficult for signal light and stray light to interfere, and deterioration of the detection signal of the sensor unit is suppressed. Therefore, fluctuations that occur in various signals generated based on the detection signal of the sensor unit can be suppressed. In particular, by suppressing fluctuations in the tracking error signal (push-pull signal), it becomes possible to detect the track properly.

  In the present embodiment, the spectroscopic element H2 is used, but the spectroscopic element H1 may be used instead of the spectroscopic element H2. In this case as well, the same effects as in the present embodiment are achieved.

  As mentioned above, although the Example of this invention was described, this invention is not restrict | limited to the said Example at all, Moreover, a various change is possible for the Example of this invention besides the above.

For example, in the above-described embodiment, the BD light is dispersed using the spectroscopic element H2 having a diffraction pattern formed on the light incident surface. Instead, the BD light is separated using a spectroscopic element composed of a prism having a plurality of surfaces. The light may be dispersed. On the incident surface of such a prism, six surfaces corresponding to the diffraction regions H2a to H2f of the spectroscopic element H2 and one surface corresponding to the diffraction region H2g are formed. Light incident on the surfaces corresponding to the diffraction regions H2a to H2f is refracted in the directions of Da, Vb, Vc, Dd, Vf, and Vg in FIG. Light incident on the surface corresponding to the diffraction region H2g does not enter the sensor portions B1 to B8. As a result, as in the case of using the spectral element H2, the signal light of the BD light and the stray lights 1 and 2 are irradiated on the light receiving surface as shown in FIGS.

  In the case of using the spectroscopic element composed of the prism, the optical system for receiving BD light and the optical system for receiving CD light and DVD light can be configured separately. That is, the BD light is guided to the BD objective lens 117 shown in FIG. 16B by the optical system for BD, and the two-wavelength objective lens 116 is for CD / DVD different from the optical system for BD. CD light and DVD light are guided by the optical system. The optical system for BD has a laser light source that emits BD light and one photodetector that receives the BD light reflected by the BD, and the optical system for CD / DVD emits CD light and DVD light. A laser light source and a photodetector different from the photodetector for BD light that receives CD light and DVD light reflected by the CD and DVD are included. The photodetector for CD / DVD has two sensor groups that individually receive CD light and DVD light. The BD optical system includes an anamorphic lens that introduces astigmatism into the BD light reflected by the BD, as in the above embodiment. The spectroscopic element comprising the prism is disposed, for example, in the front stage of the anamorphic lens.

  In the above-described embodiment, the spectroscopic element H2 is disposed at the front stage of the anamorphic lens 118. However, the spectroscopic element H2 may be disposed at the rear stage of the anamorphic lens 118, or the spectroscopic element is disposed on the incident surface or the output surface of the anamorphic lens 118. A diffraction pattern that imparts the same diffractive action as that of H2 to the laser light may be integrally arranged.

  In the above embodiment, the diffraction region H2g is formed at the center of the spectroscopic element H2. However, instead of this, a light shielding region for shielding incident laser light may be formed. In this case, the optical system for receiving BD light and the optical system for receiving CD light and DVD light can be configured separately.

  Further, in place of the spectroscopic element H2 of the above embodiment, spectroscopic elements H3 to H5 shown in FIGS. 18A to 18C may be used. The plane direction and curved surface direction of the anamorphic lens in each figure and the direction of the track image of the BD light incident on each spectroscopic element are the same as those shown in FIG.

  Referring to FIG. 18A, the spectroscopic element H3 has a configuration in which H2a and H2d in the spectroscopic element H2 are each divided into two regions in the same manner as the spectroscopic element H0 in FIG. Yes. The diffraction directions of the diffraction regions H3a, H3h, H3d, and H3e are adjusted to be the same as those of the diffraction regions H0a, H0h, H0d, and H0e in FIG. According to this configuration, the irradiation areas a2 and d2 in FIG. 14A are each divided into two in the vertical direction, and a gap is created between the divided irradiation areas. Even if a positional deviation occurs, the divided irradiation areas can be easily stored in the sensor units P11, P12, P17, and P18. This configuration can also be applied to the spectroscopic element H1 shown in FIG.

In addition, the spectroscopic element H4 of FIG. 18B has a configuration in which the diffraction areas H2b and H2c are integrated from the spectroscopic element H2, and the diffraction areas H2e and H2f are integrated. The diffraction regions H4b and H4c diffract the incident laser light in directions Db and Dc (see FIG. 4A), respectively, by a diffraction action. Further, the spectroscopic element H5 in FIG. 18C is separated from the spectroscopic element H4 by the boundary lines of the diffraction regions H4a and H4b, the boundary lines of the diffraction regions H4a and H4c, the boundary lines of the diffraction regions H4b and H4d, and the diffraction regions H4c and H4d. The boundary line is configured to form an angle of 45 degrees with the vertical and horizontal directions. In these cases as well, the effect that the signal light and the stray light are less likely to overlap at the time of lens shift can be achieved as in the case of the spectral element H2. 18B and 18C.
This configuration can also be applied to the spectral element H1 shown in FIG.

  Further, in the spectroscopic element H2 of the above embodiment, the upper and lower boundary lines of the diffraction region H2g are constituted by the straight line portion k4 and the curved portion k5 as shown in FIG. , Other straight lines or the like may be used.

  For example, as shown in FIG. 19 (a), the upper and lower boundary lines of the diffraction region formed in the central portion of the spectroscopic element are configured in a step shape by straight portions parallel to the vertical and horizontal directions. The shapes of the protrusions H2ga and H2gb formed on the upper and lower parts of the diffraction region may be changed as shown in the figure. Further, as shown in FIG. 19 (b), the boundary line between the upper part and the lower part of the diffractive region is constituted by a trapezoidal straight portion, whereby the protrusions H2ga formed at the upper and lower parts of the diffractive region, The shape of H2gb may be changed as shown. Further, as shown in FIG. 19 (c), the boundary line between the upper and lower parts of the diffraction region is constituted by a straight line portion in an oblique direction, whereby a protrusion H2ga formed on the upper and lower parts of the diffraction region, The shape of H2gb may be changed as shown. Further, as shown in FIG. 19 (d), the upper and lower boundary lines of the diffraction region are composed of straight lines in the left-right direction, and the left and right boundary lines of the diffraction region are straight lines k1 (long The straight portion k6 (length y4) may be longer than the length y3). 19A to 19D can also be applied to the spectroscopic element H1 shown in FIG.

  Thus, the shape of the diffraction region formed at the center of the spectroscopic element is such that the length in the direction perpendicular to the track image direction (vertical direction) is the length in the direction parallel to the track image direction (horizontal direction). What is necessary is just to be comprised so that it may become larger than this. In this case, the upper and lower shapes of the diffraction region are reflected on the size and contour of the portion from which the stray light is removed on the sensor unit, so that the stray light is considered in consideration of the relationship between the stray light and the signal light. It is adjusted so that it is not covered with signal light. The upper and lower shapes of the diffraction region may be configured such that the length of the diffraction region in the vertical direction is the longest at least in the vicinity of the central portion in the left-right direction.

  In addition, the embodiment of the present invention can be variously modified as appropriate within the scope of the technical idea shown in the claims.

101 ... Semiconductor laser (laser light source)
117 ... BD objective lens (objective lens)
118 ... Anamo lens (astigmatism element)
119 ... Photodetector B1 to B8 ... Sensor part H1 to H5 ... Spectroscopic element H1b, H1c, H1e, H1f ... Diffraction region (first region)
H1a, H1d: Diffraction region (second region)
H1g: Diffraction region (third region)
H1ga, H1gb ... Protrusion H2b, H2c, H2e, H2f ... Diffraction region (first region)
H2a, H2d ... Diffraction region (second region)
H2g ... Diffraction region (third region)
H2ga, H2gb ... Projection part H3b, H3c, H3f, H3g ... Diffraction region (first region)
H3a, H3d, H3e, H3h ... Diffraction region (second region)
H3i ... Diffraction region (third region)
H4b, H4c ... Diffraction region (first region)
H4a, H4d ... Diffraction region (second region)
H4e: Diffraction region (third region)
H5b, H5c ... Diffraction region (first region)
H5a, H5d ... Diffraction region (second region)
H5e: Diffraction region (third region)
k3, k5 ... Curve part (curve part)

Claims (6)

A laser light source;
An objective lens for converging the laser light emitted from the laser light source onto a recording medium;
The laser light reflected by the recording medium is incident, the laser light is converged in a first direction to generate a first focal line, and a second perpendicular to the first direction is generated. An astigmatism element that converges the laser beam in a direction to generate a second focal line;
A photodetector for receiving the laser beam that has passed through the astigmatism element;
The laser beam reflected by the recording medium is incident, and is incident on two first regions that are not adjacent to each other and two second regions sandwiched between the first regions. A spectroscopic element that guides laser light to four apex angle positions different from each other on the light receiving surface of the photodetector,
Each of the photodetectors has a sensor unit that receives the laser beam at each of the four vertex angles.
The direction of the track image of the recording medium projected onto the laser light incident on the astigmatism element forms an angle of 45 degrees with the first and second directions,
The first region is arranged in the direction of the track image with the center of the spectroscopic element interposed therebetween, and the second region is arranged in a direction perpendicular to the direction of the track image with the center of the spectroscopic element interposed therebetween,
A third region that does not guide the laser light to the sensor unit is disposed at a central portion of the spectroscopic element, and the length of the third region in a direction perpendicular to the direction of the track image is the track image. Is longer than the length of the third region in the direction of
An optical pickup device characterized by that. The optical pickup device according to claim 1,
The third region has a protrusion that protrudes in a direction perpendicular to the direction of the track image.
An optical pickup device characterized by that. The optical pickup device according to claim 2,
The protrusion includes an arcuate curved portion,
An optical pickup device characterized by that. The optical pickup device according to claim 2 or 3,
The top of the protrusion is disposed at the center position of the third region in the direction of the track image.
An optical pickup device characterized by that. The optical pickup device according to any one of claims 1 to 4,
The boundary between the third region and the first region is a straight line perpendicular to the direction of the track image.
An optical pickup device characterized by that. The optical pickup device according to any one of claims 1 to 5,
The first region is divided into two by a straight line passing through the center of the spectroscopic element and parallel to the direction of the track image, and the laser beam incident on the divided first region is on the photodetector. The first region divided into two is configured so that a predetermined gap is generated in the irradiation region,
An optical pickup device characterized by that.

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