JP2009289330A - Optical pickup device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide such an optical pickup device and optical disk device in which a fraction defective decreases in a process using an optical disk having a plurality of recording layers to operate an objective lens in a tracking direction and evaluate a characteristic. <P>SOLUTION: The optical pickup device includes: a light source 11; an objective lens 19 for converging an outgoing light 25 on a L0 layer 21; a photodetector 23 for receiving a reflected light 26 from the L0 layer 21; and an astigmatism generation element 18 which is arranged between the objective lens 19 and the photodetector 23 and generates light for focus control from the converged reflected light 26. The astigmatism generation element 18 is formed on a slope 16, and has a plurality of ring sections 29, and a level difference part 30 connecting adjacent ring sections 29, wherein the reflected light 27 from an L1 layer 22 is made incident only on the ring sections 29 in the astigmatism generation element 18 regardless of the operation of the objective lens 19 in the tracking direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup device and an optical disk device mounted on an electronic device such as a personal computer or a notebook computer.

  Conventionally, the cost of optical pickup devices has been reduced, and a simple configuration is desired. FIG. 19 is a diagram showing an optical system configuration of a conventional optical pickup device. The light source 201 generates outgoing light 214 directed toward the recording layer 211 of the optical disc 210. The diffraction element 202 has a diffraction grating 203. The diffraction grating 203 diffracts the outgoing light 214 and separates it into zero-order light of the main beam and ± first-order light of the side beams. The light separated by the diffraction grating 203 is used for tracking control. The integrated prism 204 has inclined surfaces 205 and 206 inside. A beam splitter 207 is formed on the inclined surface 205. The beam splitter 207 separates the reflected light 215 of the outgoing light 214 reflected by the recording layer 211 from the outgoing light 214 and directs it to the light receiver 214. A Fresnel mirror 208 as an astigmatism generation element is formed on the inclined surface 206.

  20A is a sectional view of a normal reflecting mirror, and FIG. 20B is a sectional view of a Fresnel mirror. A Fresnel mirror 222 is a reflecting mirror in which a normal reflecting mirror 221 is cut in contour lines at predetermined depths d and packed in the thickness direction. Therefore, the Fresnel mirror 222 has a plurality of annular portions 223 and a step portion 224 that connects the adjacent annular portions 223. In the case of the Fresnel mirror 222, the annular zone 223 is a reflecting mirror.

  FIG. 21 is a plan view of an astigmatism generation element configured with a Fresnel mirror. In FIG. 21, the line portion corresponds to the step portion 233, and the space between the line portion and the line portion corresponds to the annular zone portion 232. In the astigmatism generation element 231, the step portion 233 is formed in an inclined concentric ellipse shape. The angle formed by the major axis and the minor axis of the concentric ellipse is 90 degrees. Therefore, the astigmatism generation element 231 can set the focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light 215 to the front side and the rear side of the light receiver 212, respectively. The light generated in this way is used for focus control by the astigmatism method.

  In FIG. 19, the objective lens 209 focuses the emitted light 214 on the recording layer 211. The optical disc 210 has a recording layer 211. Some optical discs 210 have a single recording layer 211, and some optical discs 210 have a plurality of recording layers 211. The light receiver 212 includes a light receiving unit 213, and the light receiving unit 213 receives the reflected light 215. The light receiver 212 converts the received light into an electrical signal used for focus control and tracking control and outputs the electrical signal.

Even if a Fresnel lens is used for the Fresnel mirror 222, the optical system of the optical pickup device as described above can be configured. As an example using a Fresnel lens as an astigmatism generation element (Patent Document 1), there is an example using a Fresnel mirror (Patent Document 2).
JP-A-63-046402 JP 2008-090990 A

  However, when manufacturing an optical disc apparatus equipped with an optical pickup device using a Fresnel mirror as an astigmatism generation element, the objective lens is operated in the tracking direction using an optical disc having two recording layers, and the characteristics are evaluated. The defect rate in the process is high. That is, when the objective lens operates in the tracking direction, the reflected light from the recording layer on the back side is reflected from other than the annular portion of the astigmatism generation element, and as a result, the step of the astigmatism generation element in the light receiving portion of the light receiver The state where the reflected light disappears due to the portion occurs, which increases the defect rate.

  The present invention solves the above-described problems, and an optical pickup device and an optical disc apparatus in which a defect rate is reduced in a process of evaluating characteristics by operating an objective lens in a tracking direction using an optical disc having a plurality of recording layers. The purpose is to provide.

  In order to solve the above problems, an optical pickup device of the present invention includes a light source that generates outgoing light toward a predetermined recording layer of an optical disc, an objective lens that focuses the outgoing light on the predetermined recording layer, and A light receiver that reflects the reflected light that has passed through the objective lens after being reflected by the predetermined recording layer, and is disposed between the objective lens and the light receiver, and converges toward the light receiver. An astigmatism generation element that generates focus control light with the focal positions in two cross-sections including the optical axis of the reflected light orthogonal to each other, respectively, on the front side and the rear side of the light receiver. The point aberration generating element is formed on the surface, and has a plurality of annular portions and a step portion connecting the adjacent annular portions, and the predetermined recording is performed regardless of the movement of the objective lens in the tracking direction. Note on the back side of the layer Wherein the reflected light from the layer was constituted only incident on the astigmatism said annular portion in the generating element.

  Since the reflected light from the recording layer on the back side of the predetermined recording layer is incident only on the annular zone, the reflected light from the recording layer on the back side is caused by the step portion of the astigmatism generation element in the light receiving part of the light receiver. It is possible to prevent the reflected light from being lost.

  In the present invention, even if the objective lens is operated in the tracking direction, the degree of influence by the recording layer other than the predetermined recording layer is small. Therefore, it is possible to reduce the defect rate in the process of evaluating the characteristics by operating the objective lens in the tracking direction using an optical disk having a plurality of recording layers. That is, according to the present invention, even when the objective lens is operated in the tracking direction, the reflected light from the recording layer on the back side is incident only on the annular portion of the astigmatism generation element, so that the reflected light disappearance state does not occur. As a result, the defect rate can be lowered.

  According to a first aspect of the present invention, there is provided a light source that generates outgoing light toward a predetermined recording layer of an optical disc, an objective lens that focuses the outgoing light on the predetermined recording layer, and the outgoing light is reflected by the predetermined recording layer. A light receiver that receives the reflected light that has passed through the objective lens, and two cross sections that are arranged between the objective lens and the light receiver and that are orthogonal to each other, including the optical axis of the reflected light that is focused toward the light receiver. An astigmatism generation element that generates focus control light with the focal position at the front side and the rear side of the photoreceiver, respectively, and the astigmatism generation element is formed on the surface and includes a plurality of annular portions And a stepped portion connecting adjacent ring zones, and the reflected light from the recording layer on the back side of the predetermined recording layer regardless of the movement of the objective lens in the tracking direction is reflected in the astigmatism generation element. Optical pickup configured to enter only the band It was the location.

  The focal position of reflected light from the recording layer on the back side of the predetermined recording layer is closer to the optical disc than the focal position of reflected light from the predetermined recording layer. Therefore, the reflected light from the recording layer on the back side is incident on the astigmatism generation element in a state of being focused more than the reflected light from the predetermined recording layer. On the other hand, when the objective lens operates in the tracking direction, the position of the reflected light incident on the astigmatism generation element also changes. When the reflected light hits the step portion of the astigmatism generation element, the light reflected by the step portion does not enter the light receiver correctly. The degree of influence is greater as the incident reflected light is collected. In the present invention, the reflected light from the recording layer on the back side is configured to be incident only on the annular portion of the astigmatism generation element, so that the degree of influence by the step portion is small. Therefore, it is possible to reduce the defect rate in the process of evaluating the characteristics by operating the objective lens in the tracking direction using an optical disk having a plurality of recording layers. That is, according to the present invention, even when the objective lens is operated in the tracking direction, the reflected light from the recording layer on the back side is incident only on the annular portion of the astigmatism generation element, so that the reflected light disappearance state does not occur. As a result, the defect rate can be lowered.

  According to a second aspect of the present invention, in the first aspect of the present invention, the astigmatism generation element is an optical pickup device having a Fresnel mirror whose ring zone is a reflecting mirror.

  Since the Fresnel mirror can suppress the generation of multi-order diffracted light as compared with the diffractive mirror, the reflected light from the optical disk can be efficiently used as focus control light.

  A third aspect of the present invention is the optical pickup device according to the first aspect, wherein the astigmatism generation element is a Fresnel lens having an annular portion as a lens portion.

  Since the Fresnel lens can suppress the generation of multi-order diffracted light as compared with the diffractive lens, the reflected light from the optical disk can be efficiently used as focus control light.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the annular zone is formed in a concentric elliptical shape, and the reflected light from the recording layer on the back side is the innermost annular zone regardless of the movement of the objective lens in the tracking direction. The optical pickup device is incident only on the part.

  The innermost annular zone is long in the direction corresponding to the tracking direction, and the reflected light from the inner recording layer hardly protrudes from the innermost annular zone even if the position of the objective lens changes greatly. Therefore, even when the objective lens is operated in the tracking direction, the reflected light from the recording layer on the back side is incident only on the zonal part of the astigmatism generating element, so the reflected light disappearing state does not occur, and this effect is poor. The rate can be lowered.

  According to a fifth aspect of the present invention, there is provided an optical pickup device according to the fourth aspect of the invention, wherein reflected light from a predetermined recording layer is incident on the central portion of the innermost annular zone.

  Regardless of the direction in which the objective lens moves in the tracking direction, the reflected light from the inner recording layer hardly protrudes from the annular zone. Therefore, even when the objective lens is operated in the tracking direction, the reflected light from the recording layer on the back side is incident only on the zonal part of the astigmatism generating element, so the reflected light disappearing state does not occur, and this effect is poor. The rate can be lowered.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the light source generates the second outgoing light toward the second optical disc having only one recording layer in the vicinity of the outgoing light, and the second outgoing light. However, an optical pickup device in which the reflected light reflected by the second optical disk is incident on a position shifted from the center of the innermost ring part.

  Since the second optical disc has only one recording layer, there is essentially no reflected light from other than the recording layer. For this reason, there is no light incident on the astigmatism generation element in a focused state, so that no reflected light disappears. Therefore, even if the reflected light reflected by the second optical disk is incident on the stepped portion, the influence is small, so that it can be incident on a position shifted from the center of the innermost annular zone. Therefore, an optical pickup device using a light source that generates two types of outgoing light can be configured.

  The invention according to claim 7 is the optical pickup device according to claim 1, wherein the height difference of the innermost ring zone portion of the ring zone portions is made larger than the height difference of the step portion.

  By increasing the height difference of the innermost annular zone, the distance from the center of the innermost annular zone to the innermost stepped portion can be increased. Therefore, even if the position of the objective lens changes greatly, the reflected light from the inner recording layer is unlikely to protrude from the innermost annular zone. Therefore, even when the objective lens is operated in the tracking direction, the reflected light from the recording layer on the back side is incident only on the zonal part of the astigmatism generating element, so the reflected light disappearing state does not occur, and this effect is poor. The rate can be lowered.

  According to an eighth aspect of the present invention, there is provided a light source that generates outgoing light directed to a predetermined recording layer of an optical disc, an objective lens that focuses the outgoing light on the predetermined recording layer, and an objective lens that reflects the outgoing light on the predetermined recording layer. The focal position in two cross sections orthogonal to each other, including the optical axis of the reflected light that is disposed between the objective lens and the light receiver and is focused between the objective lens and the light receiver. And an astigmatism generation element that generates light for focus control on the front side and the rear side of the light receiver, respectively, and the astigmatism generation element is formed on the surface and is adjacent to a plurality of annular zones. A step portion that connects the annular zone to be reflected, and the reflected light from the recording layer farther than the predetermined recording layer is incident on the annular zone in the astigmatism generation element regardless of the movement of the objective lens in the tracking direction. The optical disk apparatus is configured to be only incident.

  The focal position of reflected light from the recording layer on the back side of the predetermined recording layer is closer to the optical disc than the focal position of reflected light from the predetermined recording layer. Therefore, the reflected light from the recording layer on the back side is incident on the astigmatism generation element in a state of being focused more than the reflected light from the predetermined recording layer. On the other hand, when the objective lens operates in the tracking direction, the position of the reflected light incident on the astigmatism generation element also changes. When the reflected light hits the step portion of the astigmatism generation element, the light reflected by the step portion does not enter the light receiver correctly. The degree of influence is greater as the incident reflected light is collected. In the present invention, the reflected light from the recording layer on the back side is configured to be incident only on the annular portion of the astigmatism generation element, so that the degree of influence by the step portion is small. Therefore, it is possible to reduce the defect rate in the process of evaluating the characteristics by operating the objective lens in the tracking direction using an optical disk having a plurality of recording layers. That is, according to the present invention, even when the objective lens is operated in the tracking direction, the reflected light from the recording layer on the back side is incident only on the annular portion of the astigmatism generation element, so that the reflected light disappearance state does not occur. As a result, the defect rate can be lowered.

(Embodiment 1)
The first embodiment will be described with reference to the drawings. First, the outline of the present invention will be briefly described.

  1A is a diagram illustrating a path of reflected light from the L0 layer in the optical pickup device according to the first embodiment, FIG. 1B is a diagram illustrating a path of reflected light from the L1 layer, and FIG. ) Is a configuration diagram of the integrated prism in the first embodiment. FIG. 2A shows a spot of reflected light from the L0 layer incident on the astigmatism generation element in the first embodiment, and FIG. 2B shows astigmatism generation in the first embodiment. FIG. 2C shows a spot of reflected light from the L1 layer incident on the element, FIG. 2C shows a spot of reflected light from the L0 layer incident on the conventional astigmatism generating element, and FIG. It is a figure which shows the spot of the reflected light from the L1 layer which injects into the conventional astigmatism production | generation element. 3A shows a spot of reflected light from the L1 layer on the light receiver in the first embodiment, and FIG. 3B shows a spot of reflected light from the L1 layer on the conventional light receiver. FIG.

  The light source 11 generates emitted light 25 toward the L0 layer 21 that is a predetermined recording layer of the optical disc 20. The objective lens 19 focuses the outgoing light 25 on the L0 layer 21. The light receiver 23 receives the reflected light 26, which is obtained by reflecting the outgoing light 25 on the L0 layer 21 and passing through the objective lens 19. The astigmatism generation element 18 is disposed between the objective lens 19 and the light receiver 23 and has focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light 26 focused toward the light receiver 23. Light for focus control is generated on the front side and the rear side of the light receiver 23, respectively. The astigmatism generation element 18 is formed on the slope 16 and has a plurality of annular portions 29 and step portions 30 that connect the adjacent annular portions 29. In the optical pickup device of the present invention, the reflected light 27 from the L1 layer 22, which is the recording layer on the back side of the L0 layer 21, in the astigmatism generation element 18 regardless of the movement of the objective lens 19 in the tracking direction. The light is incident only on the portion 29. Here, the astigmatism generation element 18 is a Fresnel mirror 30, and the annular zone 29 is a reflecting mirror.

  The focal position of the reflected light 26 from the L0 layer 21 shown in FIG. Therefore, the reflected light 26 is incident on the astigmatism generation element 18 in a spread state. On the other hand, a part of the outgoing light 25 incident on the L0 layer 21 is transmitted as it is, is incident on the L1 layer 22 and is reflected, and reaches the light receiver 23 as shown in FIG. The focal position of the reflected light 27 from the L1 layer 22 is not near the light receiver 23 but closer to the optical disc 20. Therefore, the reflected light 27 from the L1 layer 22 is incident on the astigmatism generation element 18 in a more focused state than the reflected light 26 from the L0 layer 21. Therefore, the spot 52 by the reflected light 27 from the L1 layer 22 shown in FIG. 2B is smaller than the spot 50 by the reflected light 26 from the L0 layer 21 shown in FIG. On the other hand, when the objective lens 29 operates in the tracking direction, the position of the spot 52 of the reflected light 27 incident on the astigmatism generation element 18 also changes to positions such as the spot 53 and the spot 54 with the operation of the objective lens 29. To do. For example, when the spot 53 hits the step portion 30 of the astigmatism generation element 18 as shown in FIG. 2 (d), the light reflected by the step portion 30 is reflected as shown in FIG. 3 (b). An extinction state occurs and does not enter the light receiver 212 correctly. The degree of influence is greater as the incident reflected light 27 is collected.

  In the present invention, the reflected light 27 from the L1 layer 22 is configured to be incident only on the annular portion 29 of the astigmatism generation element 18, and thus the degree of influence by the step portion 30 is small. Therefore, the defect rate in the process of evaluating the characteristics by operating the objective lens 19 in the tracking direction using the optical disk 20 having a plurality of recording layers can be reduced. That is, according to the present invention, the reflected light 27 from the L1 layer 22 is incident only on the annular zone 29 of the astigmatism generation element 18 even during the operation of the objective lens 19 in the tracking direction. As a result, the defect rate can be lowered.

  Next, the first embodiment will be described in more detail. In FIG. 1, the outgoing light 25 generated by the light source 11 has a wavelength λ1 of about 650 nm. The light source 11 generates second emitted light having a wavelength λ2 of about 780 nm in the vicinity of the emitted light 25. The emission position of the emitted light 25 and the emission position of the second emitted light are a distance of about 110 μm. The emitted light 25 is used for DVD recording and reproduction. The second outgoing light is used for CD recording and reproduction.

  4A is a perspective configuration diagram of the diffractive element in the first embodiment, FIG. 4B is a perspective view from the upper surface of the diffractive element, and FIG. 4C is a cross-sectional view from the side of the diffractive element. . The diffraction element 12 has a configuration in which a diffraction grating 13 is sandwiched between two substrates 12a and 12b. The diffraction grating 13 has a configuration in which a DVD diffraction grating 13a that diffracts DVD light and a CD diffraction grating 13b that diffracts CD light are arranged in series. A substrate 12c is sandwiched between the DVD diffraction grating 13a and the CD diffraction grating 13b. Optical glass such as BK7 is used for the substrates 12a, 12b, and 12c. The substrate 12c may be omitted, and the DVD diffraction grating 13a formed on the substrate 12a and the CD diffraction grating 13b formed on the substrate 12b may be directly bonded together.

  The DVD diffraction grating 13a includes a first concavo-convex portion 13c formed in stripes having a predetermined depth, interval, and direction, and a first filling portion 13d formed so as to fill the first concavo-convex portion 13c. The Usually, both the first uneven portion 13c and the first filling portion 13d are formed of a transparent resin. In addition, at least one of the first uneven portion 13c or the first filling portion 13d includes a coloring matter such as a dye or a pigment having light absorption in a predetermined wavelength region. The refractive index of the transparent resin when the pigment is included is larger as the wavelength is closer to a predetermined wavelength range than the refractive index of the transparent resin when the pigment is not included. As such, the refractive index of the first uneven portion 13c and the refractive index of the first filling portion 13d are adjusted to be different at the wavelength λ1 and equal at the wavelength λ2. For this reason, the first diffraction grating 13a diffracts the DVD light, separates it into zero-order light and ± first-order light, and transmits the CD light as it is.

  Similarly, the CD diffraction grating 13b includes a second concavo-convex portion 13e formed in a stripe shape having a predetermined depth, interval, and direction, and a second filling portion 13f formed so as to fill the second concavo-convex portion 13e. Consists of. Usually, both the 2nd uneven | corrugated | grooved part 13e and the 2nd filling part 13f are formed with transparent resin. And at least one of the 2nd uneven | corrugated | grooved part 13e or the 2nd filling part 13f is made to contain the pigment | dye which has light absorption in a predetermined wavelength range. In this way, the refractive index of the second uneven portion 13e and the refractive index of the second filling portion 13f are adjusted to be equal at the wavelength λ1 and different at the wavelength λ2. For this reason, the second diffraction grating 13b transmits the DVD light as it is, diffracts the CD light, and separates the light into zero-order light and ± first-order light. The diffracted light thus obtained is used for DVD tracking control and CD tracking control, respectively.

  In FIG. 1, the integrated prism 14 on which the astigmatism generation element 18 is formed is formed of optical glass such as BK7. The integrated prism 14 has inclined surfaces 15 and 16 having an inclination of 45 degrees with respect to the outer shape. The slope 15 and the slope 16 are parallel. A beam splitter 17 is formed on the slope 15, and an astigmatism generation element 18 is formed on the slope 16.

  The beam splitter 17 transmits the emitted light 25 from the light source 11 and reflects the reflected lights 26 and 27 so as to enter the astigmatism generation element 18. The beam splitter 17 includes a polarization separation film, for example.

  The astigmatism generation element 18 includes a Fresnel mirror 28. FIG. 5A is a sectional view of a normal mirror, and FIG. 5B is a sectional view of a Fresnel mirror. The Fresnel mirror 32 is a mirror in which the height difference is reduced by turning the normal mirror 31 into a ring for each predetermined step depth d. The Fresnel mirror 32 has a plurality of annular zones 33 and a stepped portion 34 that connects the adjacent annular zones 33, and the annular zone 33 serves as a reflecting mirror portion. The Fresnel mirror 32 can be made thin and is formed on the surface. The annular zone 33 is a portion where the inclination is relatively gentle as a whole and light is actually incident and reflected. Further, the stepped portion 34 has a steep slope and is a portion that hardly contributes to the original function as the astigmatism generating element 18 shown below. Since the Fresnel mirror 32 can suppress the generation of multi-order diffracted light as compared with the diffractive mirror, the reflected light 26 from the optical disk 20 can be efficiently used as focus control light.

  In the first embodiment, the astigmatism generation element 18 is the Fresnel mirror 28, but a diffractive mirror may be used. Moreover, although the ring zone part 33 has desirable smooth surface shape, a step-shaped surface shape may be sufficient.

  6A is an operation diagram of the astigmatism generation element, FIG. 6B is a diagram showing a light spot shape when the optical disc is close, and FIG. 6C is a diagram showing a light spot shape when the optical disc is far away. It is. The astigmatism generation element 40 varies the focal length at two cross sections 42 and 43 that are orthogonal to each other including the optical axis 41. The astigmatism generation element 40 includes a so-called cylindrical lens, a cylindrical lens and a combination thereof, and a cylindrical reflection mirror, a cylindrical reflection mirror and a combination thereof. In FIG. 6A, the astigmatism generation element 40 is a cylindrical lens for simplicity.

  In the present invention, the reflected light from the optical disk enters the astigmatism generation element 40 so as to be focused in the vicinity of the light receiver 47. Incident light in the direction of the cross section 42 in the vertical direction passes through the astigmatism generation element 40 as it is, converges on the focal point 44 on the front side of the light receiver 47 and then enters the light receiver 47. On the other hand, the incident light in the cross-sectional direction 43 in the left-right direction enters the light receiver 47 so as to be focused on the focal point 45 on the rear side of the light receiver 47 because the astigmatism generation element 40 functions as a concave lens. That is, the incident light in the direction of the cross section 42 enters the light receiver 47 in a state where it is once converged at the focal point 44 and then slightly spread. Incident light in the direction of the cross-section 43 is incident on the light receiver 47 in a state of being slightly expanded so as to be focused at the focal point 45. Therefore, the spot 46 on the light receiver 47 has a substantially circular shape in a slightly expanded state.

  The light receiver 47 includes A to D light receiving portions 48 that receive light that has passed through the astigmatism generation element 40. The light receiving unit 48 is arranged in a square shape and rotated by 45 ° with respect to the cross sections 42 and 43. The light receiving portions 48 for A and C are arranged in the left-right direction, and the light receiving portions 48 for B and D are arranged in the vertical direction. The light receiving units 48 of A to D convert the received light quantity into an electrical signal. The electrical signal converted by the A light receiving unit 48 is converted to A, the electric signal converted by the B light receiving unit 48 is converted to B, and the electric signal converted by the C light receiving unit 48 is converted by the C and D light receiving units 48. Let D be the electrical signal. A focus error signal FES which is a signal for focus control can be obtained by calculating FES = (A + C) − (B + D).

  As shown in FIG. 6B, when the optical disk is close to the optical pickup device, the focal points 44 and 45 are away from the optical disk, so that the focal point 44 approaches the light receiver 47 and the focal point 45 moves away from the light receiver 47. Therefore, the upper and lower dimensions of the spot 46 are shortened, and the left and right dimensions are lengthened. Therefore, the focus error signal FES> 0. Conversely, as shown in FIG. 6C, when the optical disk is far from the optical pickup device, the focal points 44 and 45 are closer to the optical disk, so that the focal point 44 is farther from the light receiver 47 and the focal point 45 is closer to the light receiver 47. Therefore, the upper and lower dimensions of the spot 46 become longer, and the left and right dimensions become shorter. Therefore, the focus error signal FES <0. As described above, the focus error signal FES is a focus control signal indicating a positional deviation of the optical disc in the focus direction. Focus control is performed so that the focus error signal FES = 0 or a predetermined value.

  In the first embodiment, the annular zone 29 of the Fresnel mirror 28 that is the astigmatism generation element 18 has a concentric elliptical shape as shown in FIG. The major axis direction of the concentric ellipse corresponds to either the direction of the cross section 42 or the direction of the cross section 43 in FIG. 6, and the minor axis direction corresponds to the other. The reflected light 26 from the L0 layer 21 is incident on the innermost annular zone 29 of the concentric ellipse shape. Since the center position of the spot 52 of the reflected light 27 from the L1 layer 22 substantially coincides with the center position of the spot 50, the spot 52 of the reflected light 27 from the L1 layer 22 is located in the innermost annular zone 29. The innermost annular zone 29 is long in the direction corresponding to the tracking direction, and the reflected light 27 from the L1 layer 22 protrudes from the innermost annular zone 29 even if the position of the objective lens 19 changes greatly. Hateful. Therefore, even when the objective lens 19 is operated in the tracking direction, the reflected light from the L1 layer 22 is incident only on the annular zone 29 of the astigmatism generation element 18, so that no reflected light disappears. As a result, the defect rate can be lowered. Furthermore, the light spot 50 for DVD is positioned substantially at the center of the innermost annular zone 29. Accordingly, the light spot 51 for CD is displaced from the center of the innermost annular zone 29.

  The objective lens 19 is a lens that focuses the emitted light 25 for DVD onto the L0 layer 21 of the DVD. Further, the objective lens 19 can focus the emitted light 25 for DVD on the L1 layer 22 of DVD. Furthermore, the objective lens 19 can also focus the second emitted light for CD onto the recording layer of the CD.

  In FIG. 3A, the light receiver 23 receives the reflected lights 26 and 27 reflected by the emitted light 25 from the L0 layer 21 and the L1 layer 22 which are predetermined recording layers of the DVD and passed through the objective lens 19. Further, the reflected light that has been reflected by the recording layer of the CD and passed through the objective lens 19 is also received. The light receiver 23 converts the amount of light detected by the light receiving unit 24 into an electrical signal and outputs it. The output signal is used for focus control, tracking control, reproduction of information recorded on the optical disc, and the like.

  The light receiver 23 includes light receiving portions 24 of A to L and a to h. Light having a wavelength λ1 for DVD is incident on the light receiving portions 24 of A to L. The light having the wavelength λ2 for CD is incident on the light receiving portions 24 of a to h. The 0th order light generated by the first diffraction grating 13a is incident on the light receiving parts 24 of A to D, and any one of ± 1st order light is incident on the light receiving parts 24 of E to G and I to L. The 0th order light generated by the second diffraction grating 13b is incident on the light receiving portions 24a to d, and either ± 1st order light is incident on the light receiving portions 18a for e · g and f · h. . 6 correspond to the light receiving units 24 of A to D and the light receiving units 24 of a to d in FIG.

  In the first embodiment, the astigmatism generation element 18 is rotated 45 degrees in the direction perpendicular to the optical axis 41 with respect to the astigmatism generation element 40. Accordingly, the light receiving unit 24 of the light receiver 23 is rotated 45 degrees in the plane of the light receiving unit 48 of the light receiver 47. Therefore, the boundary between the light receiving portions A to D in the light receiving device 23 is horizontal and vertical, and the design of the arrangement of the light receiving portions 24 including the other light receiving portions 24 becomes easy.

  In the light receiver 23, the electric signals for DVD that are incident on the light receiving portions 24 of A, B, C, D, E, F, G, H, I, J, K, and L and converted are A, B, C, Let D, E, F, G, H, I, J, K, L. The electrical signals for CD that have entered and converted to the a, b, c, d, e, f, g, and h light receiving portions 24 are a, b, c, d, e, f, g, and h.

  The focus error signal FES for DVD is DVD-ROM, DVD ± R / RW: FES = (A + C) − (B + D), DVD-RAM: FES = {(A + C) − (B + D)} + Kt × {(E + I + G + K) − (H + L + F + J)}. Here, Kt is a constant determined according to the operation setting. The focus error signal FES is a signal indicating a spot defocus.

  The focus error signal FES for CD is CD-R / RW / ROM: FES = (a + c)-(b + d).

  The tracking error signal TES for DVD includes DVD-ROM: TES = ph (A, D) -ph (B, C), DVD ± R / RW, −RAM: TES = {(A + B) − (C + D)} −. Kt × {(E + I + F + J) − (G + K + H + L)}. Here, ph (X, Y) is a voltage obtained by converting the detected phase difference between X and Y. The tracking error signal TES is a signal indicating the track position deviation of the spot.

  The tracking error signal TES for CD is CD-R / RW / ROM: TES = {(a + b) − (c + d)} − Kt × {(e + f) − (g + h)}, CD-ROM: TES = ph (a , D) -ph (b, c). Usually, the former method is used which allows more stable tracking control. However, for example, when reproducing a bad disk whose CD-ROM pit height does not fall within the standard, the tracking error signal TES may not be output well by the former method. Even in such a case, the latter method can output the tracking error signal TES well, so that it can be used as a preliminary tracking control method. Thus, since it is possible to perform the tracking control even when reproducing a bad disk that is out of the standard that cannot be tracked, it is possible to deal with a wider range of optical disks 20 as an optical disk apparatus.

  In FIG. 3, the arrangements of the light receiving portions 24 for E to H, A to D, and I to L, and the light receiving portions 24 for e · g, a to d, and f · h are slightly shifted from the vertical direction on the paper surface. This is because when the zero-order light is focused on the track of the recording layer of the optical disc, the ± first-order light is shifted from the track and focused. Therefore, when the zero-order light and the ± first-order light are focused on the same track, the light receiving portions 24 of E to H, A to D, and I to L, and the light reception of e · g, a to d, and f · h The sections 24 are arranged in the vertical direction on the paper surface.

  The optical disc 20 having a plurality of recording layers is a DVD. The recording layer on the front side of the optical disc 20 is referred to as L0 layer 21, and the recording layer on the back side is referred to as L1 layer 22. Some DVDs have a single recording layer. The CD has a single recording layer. In the first embodiment, the recording layers of the optical disc 20 are the L0 layer 21 and the L1 layer 22, but the optical disc 20 may have a larger number of recording layers.

  In FIG. 1, the emitted light 25 having the wavelength λ 1 generated by the light source 11 is diffracted by the diffraction grating 13. The outgoing light 25 passes through the beam splitter 17 and enters the objective lens 19. The objective lens 19 focuses the outgoing light 25 on the L0 layer 21. The outgoing light 25 is reflected by the L0 layer 21, and the reflected light 26 passes through the objective lens 19, is reflected by the beam splitter 17, and enters the astigmatism generation element 18. At that time, the reflected light 26 is focused toward the light receiver 23. The astigmatism generation element 18 converts the focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light 26 so as to be on the front side and the rear side of the light receiver 23, respectively, and enters the light receiver 23.

  At this time, part of the emitted light 25 is transmitted through the L0 layer 21 and reflected by the L1 layer 22. The reflected light 27 behaves as if it is emitted from one point deeper in the L1 layer 22. Therefore, the reflected light 26 is focused in the vicinity of the light receiver 23, but the reflected light 27 is focused closer to the optical disc 20 than that. Therefore, as shown in FIG. 2, the spot 52 is substantially the same position as the spot 50, but the spot 52 is smaller than the spot 50. On the contrary, the reflected light 26 is almost focused by the light receiver 23, but as shown in FIG.

  As shown in FIG. 2 (c), the center of the annular portion 232 of the conventional astigmatism generation element 231 is arranged between the spot 50 and the spot 51. As a result, as shown in FIG. 2D, when the objective lens 209 is moved in the tracking direction, the spot 52 moves like a spot 53 or a spot 54. When the stepped portion 233 is crossed like the spot 53, the portion of the stepped portion 233 is not correctly reflected, so that the spot 55 has a strip-like reflected light disappearance state as shown in FIG. 3B. The position of the reflected light disappearing state changes with the movement of the objective lens 209 in the tracking direction, and when the reflected light disappearing portion hits the light receiving unit 213, the amount of received light is unbalanced, leading to deterioration of characteristics. In particular, the E, F, H, G, I, J, K, and L light receiving portions 213 to which ± 1st order light is incident have a higher amplification factor than the A, B, C, and D light receiving portions 213, so that reflection When the light-disappearing state is applied to these light-receiving portions 213, the influence is greater, and the tracking control characteristics are deteriorated. This is a cause of defects in the manufacturing process.

  In the first embodiment, like the spot 52 in FIG. 2B, the reflected light 27 from the L1 layer 22 is incident only on the annular zone 29 even when the objective lens 19 operates in the tracking direction. Therefore, unlike the spot 55 in FIG. 3A, the reflected light 27 from the L1 layer 22 does not cause the reflected light disappearing state in the light receiver 23. For this reason, it is difficult for an unbalance of the received light amount of each light receiving unit 24 due to the light amount distribution of the spot 55 incident on the light receiving unit 24. Therefore, stable tracking control can be performed even if the objective lens 19 operates in the tracking direction, and defects in the manufacturing process can be suppressed.

  FIG. 1 shows an optical system of an optical pickup device related to the first embodiment, but the optical pickup device has more optical components. FIG. 7 is a configuration diagram of an optical system in the optical pickup device of the first embodiment. FIG. 8 is a block diagram of the optical pickup device of the first embodiment.

  In FIG. 7, the wave plate 60, the collimating lens 61, the rising mirror 62, and the light receiver 63 are increased from the configuration of FIG. A CD recording layer 64 is also displayed.

  The wave plate 60 converts the outgoing light 25 for DVD that is P-polarized light into circularly polarized light, and converts the reflected light 26 that is circularly polarized light into S-polarized light. At that time, the reflected light 27 is also converted to S-polarized light. The wave plate 60 converts the second emitted light for CD from P-polarized light to circularly-polarized light, and converts reflected light that is circularly polarized light into S-polarized light. The beam splitter 17 is a polarization separation film as described above. The polarization separation film has, for example, a characteristic of transmitting P-polarized light and reflecting S-polarized light. In this way, the wave plate 60 causes the beam splitter 17 to separate the reflected light for DVD 26 and the reflected light for CD from the emitted light 25 for DVD and the second emitted light for CD.

  The collimating lens 61 converts the outgoing light 25 from diffused light to substantially parallel light, and converts the reflected light 26 that is substantially parallel light into focused light that is focused near the light receiver 23. As shown in FIG. 1, the collimating lens 61 is not disposed, and the outgoing light 25 that is diffused light is incident on the objective lens 19, and the objective lens 19 converts the reflected light 26 into focused light that converges in the vicinity of the light receiver 23. It doesn't matter.

  The rising mirror 62 is a reflecting mirror for raising the directions of the outgoing light 25 and the second outgoing light, which have been substantially parallel to the optical disk 20 until then, to rise substantially perpendicular to the optical disk 20 and to enter the objective lens 19. A rising prism may be used. In the first embodiment, the rising mirror 62 transmits part of the outgoing light 25 and part of the second outgoing light.

  The light receiver 63 detects light transmitted through the rising mirror 62. The detected light is converted into an electrical signal by the light receiver 63 and output, and is used for output control of the emitted light 25 and the second emitted light.

  In FIG. 8, an optical pickup device 70 is configured by attaching each component of the optical system to a base 71 directly or via other components. The base 71 is a framework of the optical pickup device 70. The base 71 is made of an alloy material such as a Zn alloy or Mg alloy or a hard resin material, but an alloy material that can easily ensure rigidity is desirable. The base 71 is provided with mounting portions for arranging various components at predetermined locations.

  The light source 11, the diffraction element 12, the integrated prism 14, and the light receiver 23 are fixed to the coupling base 72 to constitute a laser module 73, and the coupling base 72 is fixed to the base 71. The coupling base 72 is formed of, for example, an alloy material having high thermal conductivity and high rigidity. The objective lens 19 is mounted on an objective lens driving unit 74 that drives the objective lens 19, and the objective lens driving unit 74 is fixed to the base 71. The objective lens 19 is moved in the focus direction and the tracking direction by the objective lens driving unit 74. The wave plate 60, the collimating lens 61, the rising mirror 62, and the light receiver 63 are fixed to the base 71 directly or via another mounting member.

  FIG. 9A is a diagram showing a spot of reflected light from the L0 layer incident on the astigmatism generation element of another example 1 in the first embodiment, and FIG. 9B is another diagram in the first embodiment. FIG. 9C is a diagram showing a spot of reflected light from the L1 layer incident on the astigmatism generation element of Example 1 of FIG. 9, and FIG. 9C shows L0 incident on the astigmatism generation element of another example 2 of Embodiment 1. FIG. 9D is a diagram showing spots of reflected light from the layer, and FIG. 9D is a diagram showing spots of reflected light from the L1 layer incident on the astigmatism generating element of the other example 2 in the first embodiment.

  In the first embodiment, the shape drawn by the annular zone 29 of the Fresnel mirror 28 as the astigmatism generation element 18 is a concentric ellipse, but is not limited thereto. 9A and 9B, the Fresnel mirror 80 as the astigmatism generation element 83 includes an annular portion 81 that is divided by a plurality of linear step portions 82. One of the direction of the linear step portion 82 and the direction orthogonal thereto corresponds to the direction of the cross section 42 in FIG. 6, and the other corresponds to the direction of the cross section 43. Since the direction of the linear stepped portion 82 is the direction of the planar reflecting mirror, the degree of freedom in design is small. However, the innermost annular zone 81 can be secured most widely. Therefore, when the objective lens 19 operates in the tracking direction, the spot 53 and the spot 54 are unlikely to hit the step portion 83. Therefore, tracking control is stabilized.

  9C and 9D, the Fresnel mirror 84 as the astigmatism generation element 87 has a shape such that the innermost annular zone 85 has a substantially cross shape. The array of the annular zone portions 85 in one diagonal direction is a convex mirror, and the array of the annular zone portions 85 in the other diagonal direction is a concave mirror. One of the directions orthogonal to the respective step portions 86 in the diagonal direction is the direction of the cross section 42, and the other is the direction of the cross section 43. Although the area of the innermost annular zone 85 is small, the position where the reflected light 26 is focused in the vicinity of the light receiving portion 23 is close to the case where the astigmatism generation element 87 is not arranged, so that the design is easy.

  When the emitted light 25 is focused on the L1 layer 22, a part of the reflected light is reflected by the L0 layer 21, and the reflected light enters the Fresnel mirror 28 as the astigmatism generation element 18 and further enters the light receiver 23. To do. At that time, the size of the reflected light from the L1 layer 22 on the astigmatism generation element 18 is substantially equal to the spot 50. On the other hand, the spot of the reflected light from the L0 layer 21 is larger than the spot 50, and even if this spot hits the stepped portion 30, it is hardly affected by the stepped portion 30. In addition, the spot of the reflected light from the L0 layer 21 on the light receiver 23 is more blurred than the spot 55. Therefore, the spot of the reflected light from the L0 layer 21 on the light receiver 23 is unlikely to have a light amount distribution that affects the tracking control. Therefore, when the emitted light 25 is focused on the L1 layer 22, the defect rate in the process of evaluating the characteristics by operating the objective lens 19 in the tracking direction is unlikely to be high.

(Embodiment 2)
The second embodiment will be described with reference to the drawings. 10A is a cross-sectional view of a normal mirror, FIG. 10B is a cross-sectional view of the Fresnel mirror in the first embodiment, and FIG. 10C is a cross-sectional view of the Fresnel mirror in the second embodiment. FIG. 11A shows a spot of reflected light from the L0 layer incident on the astigmatism generation element in the second embodiment, and FIG. 11B shows astigmatism generation in the second embodiment. It is a figure which shows the spot of the reflected light from the L1 layer which injects into an element. 10 (a) and 10 (b) are the same as FIGS. 5 (a) and 5 (b), and the description thereof is incorporated. Further, components other than the Fresnel mirror 90 as the astigmatism generation element 93 of the optical pickup device of the second embodiment are the same as the components of the first embodiment, and the description thereof is cited.

  As shown in FIG. 10, the Fresnel mirror 90 as the astigmatism generation element 93 according to the second embodiment has a height difference d1 of the innermost annular zone 91 among the annular zones 91 and an elevation difference d of the stepped portion 92. Bigger than. By increasing the height difference d1 of the innermost annular zone 91, the distance W2 from the center of the innermost annular zone 91 to the innermost stepped portion 92 is changed to the height difference of the innermost annular zone 33. Can be made larger than the distance W1 when the height difference d of the step portion 34 is made equal. Therefore, as shown in FIG. 11, even if the position of the objective lens 19 changes greatly and the spot 52 of the reflected light 27 from the L1 layer 22 changes greatly as spots 53 and 54, the innermost ring zone It is difficult to protrude from the portion 91. For this reason, even when the objective lens 19 is operated in the tracking direction, the reflected light 27 from the L1 layer 22 is incident only on the annular zone 91 of the astigmatism generation element 93, so that no reflected light disappears. As an effect, the defect rate can be lowered.

  Conversely, the astigmatism generation element 93 shown in the second embodiment reflects from the L1 layer 22 even during the operation of the objective lens 19 in the tracking direction more than the astigmatism generation element 18 shown in the first embodiment. The spot 52 of the light 27 is difficult to protrude from the annular zone 91. For this reason, the spot 50 of the reflected light 26 from the DVD can be shifted from the center of the astigmatism generating element 93, and the spot 51 of the reflected light from the CD can be brought close to the vicinity of the center of the astigmatism generating element 93. Therefore, CD characteristics can be improved.

  The height difference d of the stepped portion 92 is not equal to the height difference d1 of the innermost annular zone 91 for the following reason. That is, the height difference d of the stepped portion 92 determines the respective phases of the DVD and the CD, and as a result, determines the relative light quantity of the DVD and the CD toward the light receiving portion 23. For this reason, there is an optimum height difference d of the optimum step portion 92.

(Embodiment 3)
The third embodiment will be described with reference to the drawings. FIG. 12 is a configuration diagram of an integrated prism in the optical pickup device according to the third embodiment. In the first and second embodiments, the astigmatism generation elements 18 and 93 are the Fresnel mirrors 28 and 90. In the third embodiment, the astigmatism generation element 105 is a Fresnel mirror 106. Components other than the integrated prism 101 having the astigmatism generation element 105 are the same as those in the first embodiment, and the description thereof is cited.

  That is, the light source 11 generates the emitted light 25 toward the L0 layer 21 that is a predetermined recording layer of the optical disc 20. The objective lens 19 focuses the outgoing light 25 on the L0 layer 21. The light receiver 23 receives the reflected light 26, which is obtained by reflecting the outgoing light 25 on the L0 layer 21 and passing through the objective lens 19. The astigmatism generation element 105 is disposed between the objective lens 19 and the light receiver 23 and has focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light 26 focused toward the light receiver 23. Light for focus control is generated on the front side and the rear side of the light receiver 23, respectively. Here, the astigmatism generation element 105 is formed on the sensor surface 104, and includes a plurality of annular zones 107 and step portions 108 that connect the adjacent annular zones 107. Here, the astigmatism generation element 105 is a Fresnel lens 106, and the annular zone 107 is a lens portion. In the optical pickup device of the present invention, the reflected light 27 from the L1 layer 22, which is the recording layer behind the L0 layer 21, is incident on the annular zone 107 in the Fresnel lens 106 regardless of the movement of the objective lens 19 in the tracking direction. Only incident.

  In the present invention, since the reflected light 27 from the L1 layer 22 is configured to be incident only on the annular zone 107 of the Fresnel lens 106, the degree of influence by the stepped portion 108 is small. Therefore, the defect rate in the process of evaluating the characteristics by operating the objective lens 19 in the tracking direction using the optical disk 20 having a plurality of recording layers can be reduced. That is, according to the present invention, the reflected light 27 from the L1 layer is incident only on the annular zone 107 of the Fresnel lens 106 even during the operation of the objective lens 19 in the tracking direction, so that the reflected light disappearance state does not occur. As a result, the defect rate can be lowered.

  Next, the third embodiment will be described in more detail. The integrated prism 101 is made of optical glass such as BK7. The integrated prism 101 has a slope 102 inside, and a beam splitter 103 is formed on the slope 102. Similar to the beam splitter 17, the beam splitter 103 transmits the emitted light 25 from the light source 11 and reflects the reflected lights 26 and 27 from the optical disk 20. The beam splitter 103 includes a polarization separation film, for example.

  A Fresnel lens 106 as an astigmatism generation element 105 is formed on the sensor surface 104 facing the light receiver 23 of the integrated prism 101. Similar to the astigmatism generation elements 18 and 93, the astigmatism generation element 105 is formed on the sensor surface 104 and has a plurality of annular zones 107 and a step portion 108 that connects the adjacent annular zones 107. The annular zone 107 is a lens portion. As in the first and second embodiments, the reflected light 27 from the L1 layer 22 on the back side of the L0 layer 21 is only incident on the annular zone 107 in the astigmatism generation element 105 regardless of the movement of the objective lens 19 in the tracking direction. It was set as the structure which injects. The annular zone 107 is a portion where the inclination is relatively gentle as a whole and light is actually incident and transmitted. Further, the step portion 108 has a steep slope and is a portion that hardly contributes to the original function as the astigmatism generation element 105. Since the Fresnel lens 106 can suppress the generation of multi-order diffracted light as compared with a diffractive lens, the reflected light 26 from the optical disk 20 can be efficiently used as focus control light.

  In the third embodiment, the astigmatism generation element 105 is the Fresnel lens 106, but may be a diffractive lens. Further, the ring zone portion 107 desirably has a smooth surface shape, but may have a stepped surface shape.

  Therefore, as in the case of the astigmatism generation elements 18 and 93, the reflected light 27 from the L1 layer 22 is configured to be incident only on the annular zone 107 of the astigmatism generation element 105. The degree of receiving is small. Therefore, the defect rate in the process of evaluating the characteristics by operating the objective lens 19 in the tracking direction using the optical disk 20 having a plurality of recording layers can be reduced. That is, according to the present invention, the reflected light 27 from the L1 layer is incident only on the annular portion 107 of the astigmatism generation element 105 even during the operation of the objective lens 19 in the tracking direction. The defect rate can be lowered as an effect.

  FIG. 13 is a configuration diagram of another example of the integrated prism in the optical pickup device according to the third embodiment. In the third embodiment, the integrated prism 101 may be configured like the integrated prism 111.

  The integrated prism 111 has a slope 112 inside, and a beam splitter 113 is provided on the slope 112. The beam splitter 113 is the same as the beam splitter 103.

  A substrate 115 on which a Fresnel lens 117 as an astigmatism generation element 116 is previously formed is attached to the sensor surface 114 of the integrated prism 111 facing the light receiver 23. Similar to the astigmatism generation element 105, the astigmatism generation element 116 is formed on the surface of the substrate 115, and has a plurality of annular portions 118 and a step portion 119 that connects the adjacent annular portions 118. The annular zone 118 is a lens part. Similar to the astigmatism generation element 105, the reflected light 27 from the L1 layer 22 on the back side of the L0 layer 21 is reflected only on the annular portion 118 in the astigmatism generation element 116 regardless of the movement of the objective lens 19 in the tracking direction. It was set as the structure which injects. Therefore, the astigmatism generation element 116 can obtain the same effect as the astigmatism generation element 105.

(Embodiment 4)
The fourth embodiment will be described with reference to the drawings. FIG. 14 is a configuration diagram of an optical system in the optical pickup device of the fourth embodiment. The optical pickup apparatus according to the first to third embodiments performs recording and reproduction for DVD and CD. The optical pickup apparatus according to the fourth embodiment performs recording and reproduction for BD (Blu-ray disc) in addition to recording and reproduction for DVD and CD. Also play.

  The light source 121, the diffraction element 122, the diffraction grating 123, the integrated prism 124, the astigmatism generation element 125, and the light receiver 126 are the light source 11, the diffraction element 12, the diffraction grating 13, the integrated prism 14, the astigmatism generation element 18, respectively. The same as the light receiver 23. Further, the coupling base 127 is the same as the coupling base 72, and the laser module 128 in which they are assembled is the same as the laser module 73. The astigmatism generation element 125 is configured by a Fresnel mirror 130. The astigmatism generation element 125 is the same as the astigmatism generation element 18 and is formed on the slope, and has a plurality of annular zones and stepped portions connecting adjacent annular zones. The reflector part.

  On the other hand, the light source 131 generates outgoing light having a wavelength λ3 of about 405 nm. This emitted light is used for BD recording and reproduction. A slope is formed inside the integrated prism 132, and a beam splitter is provided. The light receiver 134 detects the reflected light emitted from the light source 131 and reflected by the recording layer of the BD 151, converts it into an electrical signal, and outputs it. The output electric signal is used for focus control, tracking control, reproduction of information recorded on the BD, and the like. An astigmatism generation element 133 is disposed between the integrated prism 132 and the light receiver 134. The astigmatism generation element 133 is a so-called cylindrical lens, cylindrical lens, or a combination thereof. The astigmatism generation element 133 generates light used for BD focus control. The light source 131, integrated prism 132, astigmatism generation element 133, and light receiver 134 are integrally attached to the coupling base 135 as a laser module 136.

  The hologram 140 generates light used for BD tracking control by diffraction.

  The beam splitter 141 transmits the DVD light and the CD light, reflects the BD light, and separates the DVD light, the CD light, and the BD light. The beam splitter 141 includes a wavelength separation film.

  The collimating lens 142 converts light emitted from the light sources 121 and 131 that are divergent light into substantially parallel light. Conversely, the reflected light reflected by the DVD 150, CD 149, and BD 151, which is substantially parallel light, is converted into focused light.

  The rising mirror 143 reflects the emitted light for DVD and the emitted light for CD, which is substantially parallel to the DVD 150 and the CD 149, so as to be substantially perpendicular to the DVD 150 and the CD 149. The rising mirror 143 transmits the DVD output light, a part of the CD output light, and the BD output light.

  The rising mirror 144 reflects the outgoing light of the outgoing light for BD that is substantially parallel to the BD 151 so that the outgoing light is substantially perpendicular to the BD 151. Further, the rising mirror 144 transmits a part of the emitted light for BD, the emitted light for DVD, and the emitted light for CD.

  The objective lens 146 focuses the light for BD raised by the rising mirror 144 on the recording layer of the BD 151. The objective lens 147 focuses the raised DVD light on the recording layer of the DVD 150 and focuses the raised CD light on the CD 149 recording layer. The objective lens 146 and the objective lens 147 are incorporated in one objective lens driving unit 148.

  The light receiver 145 detects the light for CD, the light for DVD, and the light for BD transmitted through the rising mirror 145, converts them into electrical signals, and outputs them. The output signals are used for CD light amount control, DVD light amount control, and BD light amount control, respectively.

  The recording layer of CD149 is a single layer. The recording layer of the DVD 150 includes a single layer and a plurality of layers. Further, the recording layer of the BD 151 includes a single layer and a plurality of layers.

  The optical pickup device of the fourth embodiment is the same as that of the first to third embodiments with respect to the DVD, and the L1 layer which is a recording layer on the back side of the L0 layer of the DVD 150 regardless of the operation of the objective lens 147 in the tracking direction. The reflected light from the light is incident only on the annular zone in the Fresnel mirror 130 as the astigmatism generation element 125.

  Since the reflected light from the L1 layer of the DVD 150 is configured to enter only the annular portion of the astigmatism generation element 125, the degree of influence by the step portion is small. Therefore, the defect rate in the process of evaluating the characteristics by operating the objective lens 147 in the tracking direction using the DVD 150 can be reduced. That is, even when the objective lens 147 is operated in the tracking direction, the reflected light from the L1 layer is incident only on the annular portion of the astigmatism generation element 125, so that the reflected light disappearing state does not occur and this effect is poor. The rate can be lowered.

  Further, regarding the BD 151, in the fourth embodiment, since a Fresnel mirror or a Fresnel lens is not used as the astigmatism generation element 133, the reflected light disappearance state does not occur and the defect rate does not increase.

  In the fourth embodiment, the astigmatism generation element 125 is the Fresnel mirror 130, but a configuration using a Fresnel lens may be used. Also, a diffractive mirror or lens may be used. In addition, the ring zone portion preferably has a smooth surface shape, but may have a stepped surface shape.

(Embodiment 5)
The fifth embodiment will be described with reference to the drawings. FIG. 15 is a configuration diagram of an optical system in the optical pickup device of the fifth embodiment. The configuration of the fifth embodiment is exactly the same as the configuration of the fourth embodiment except that the astigmatism generation element 133 is formed inside the integrated prism 152 as the astigmatism generation element 153. The description of the fourth embodiment is used for descriptions other than the astigmatism generation element 153.

  The integrated prism 152 has the same configuration as the integrated prism 124, has an inclined surface inside, and an astigmatism generation element 153 is disposed on the inclined surface. The astigmatism generation element 153 includes a Fresnel mirror 154. The astigmatism generation element 153 has a plurality of annular portions and step portions connecting the adjacent annular portions, and the annular portion is a reflecting mirror portion. Regardless of the movement of the objective lens 146 in the tracking direction, the reflected light from the L1 layer on the back side of the L0 layer of the BD 151 is configured to be incident only on the annular zone in the Fresnel mirror 154.

  Since the reflected light from the L1 layer of the BD 151 is configured to enter only the annular portion of the astigmatism generation element 153, the degree of influence by the step portion is small. Therefore, the defect rate in the process of evaluating the characteristics by operating the objective lens 146 in the tracking direction using the BD 151 having a plurality of recording layers can be reduced to the same level as the optical pickup device of the fourth embodiment. That is, even when the objective lens 146 is operated in the tracking direction, the reflected light from the L1 layer is incident only on the annular portion of the astigmatism generation element 153, so that the reflected light disappearance state does not occur, and this effect is poor. The rate can be lowered. Furthermore, since the astigmatism generation element 133 can be eliminated in the fifth embodiment, a cheaper optical pickup device can be obtained.

  Although the astigmatism generation element 153 is the Fresnel mirror 154 in the fifth embodiment, a configuration using a Fresnel lens may be used. Also, a diffractive mirror or lens may be used. In addition, the ring zone portion preferably has a smooth surface shape, but may have a stepped surface shape.

(Embodiment 6)
The sixth embodiment will be described with reference to the drawings. FIG. 16 is a block diagram of an optical pickup device drive unit in the optical disk apparatus according to the sixth embodiment, FIG. 17 is a block diagram of the optical disk apparatus according to the sixth embodiment, and FIG. 18 is a diagram illustrating servo operations in the optical disk apparatus according to the sixth embodiment. It is a figure which shows a flow.

  In FIG. 16, the drive mechanism of the optical disk device 170 including a rotation drive unit that rotates the optical disk 20 and a moving unit that moves the optical pickup device 70 closer to or away from the rotation drive unit is referred to as an optical pickup module 160. The base 161 forms a framework of the optical pickup module 160, and the optical pickup module 160 is configured by arranging each component directly or indirectly on the base 161.

  The rotation drive unit includes a spindle motor 162 having a turntable 162a on which the optical disk 20 is placed. The spindle motor 162 is fixed to the base 161. The spindle motor 162 generates a rotational driving force that rotates the optical disc 20.

  The moving unit includes a feed motor 163, a screw shaft 164, a main shaft 165, and a sub shaft 166. The feed motor 163 is fixed to the base 161. The feed motor 163 generates a rotational driving force necessary for the optical pickup device 70 to move between the inner periphery and the outer periphery of the optical disc 20. As the feed motor 163, a stepping motor, a DC motor, or the like is used. The screw shaft 164 is spirally grooved and is connected to the feed motor 163 directly or via several stages of gears. In the sixth embodiment, the feed motor 163 is directly connected. The main shaft 165 and the sub shaft 166 are fixed to the base 161 via holding members at both ends. The main shaft 165 and the sub shaft 166 support the optical pickup device 70 so as to be movable in the radial direction of the optical disc 20. The optical pickup device 70 includes a rack 167 having guide teeth that mesh with the grooves of the screw shaft 164. The optical pickup device 70 can move between the inner periphery and the outer periphery of the optical disc 20 so that the rack 167 converts the rotational driving force of the feed motor 163 transmitted to the screw shaft 164 into a linear driving force.

  Note that the rotation driving unit is not limited to the configuration described in the sixth embodiment as long as it can rotate the optical disc 20 at a predetermined rotation speed. Further, the moving unit is not limited to the configuration described in the sixth embodiment as long as the moving unit can move the optical pickup device 70 to a predetermined position between the inner periphery and the outer periphery of the optical disc 20.

  The optical pickup device 70 has been described in the first embodiment, and has a configuration in which a cover 75 is attached to the configuration of FIG. The optical pickup device 70 may be replaced with the optical pickup device described in the second to fifth embodiments. The optical pickup device 70 includes a light source 11, an objective lens 19, a light receiver 23, and an astigmatism generation element 18. The light source 11 generates emitted light 25 toward the L0 layer 21 that is a predetermined recording layer of the optical disc 20. The objective lens 19 focuses the outgoing light 25 on the L0 layer 21. The light receiver 23 receives the reflected light 26, which is obtained by reflecting the outgoing light 25 on the L0 layer 21 and passing through the objective lens 19. The astigmatism generation element 18 is disposed between the objective lens 19 and the light receiver 23 and has focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light 26 focused toward the light receiver 23. Light for focus control is generated on the front side and the rear side of the light receiver 23, respectively. Here, the astigmatism generation element 18 is formed on the slope 16 and has a plurality of annular zones 29 and step portions 30 that connect the adjacent annular zones 29. In the optical pickup device 70, the reflected light 27 from the L1 layer 21, which is a recording layer on the back side of the L0 layer 21, regardless of the movement of the objective lens 19 in the tracking direction, the annular portion 29 in the astigmatism generation element 18. It was set as the structure which injects only into. Here, the astigmatism generation element 18 is the Fresnel mirror 28 having the annular portion 29 as a reflecting mirror portion, but may be a Fresnel lens. Also, a diffractive mirror or lens may be used. In addition, the ring zone portion 29 preferably has a smooth surface shape, but may have a stepped surface shape.

  In the optical pickup device 70, the reflected light 27 from the L1 layer 22 is configured to be incident only on the annular zone 29 of the astigmatism generation element 18, so that the degree of influence by the stepped portion 30 is small. Therefore, when manufacturing the optical disk device 170, the defect rate in the process of evaluating the characteristics by operating the objective lens 19 in the tracking direction using the optical disk 20 having a plurality of recording layers can be reduced. That is, in the optical pickup device 70, the reflected light 27 from the L1 layer 22 is incident only on the annular zone 29 of the astigmatism generation element 18 even during the operation of the objective lens 19 in the tracking direction. As a result, the defect rate when manufacturing the optical disc apparatus 170 can be reduced.

  The inclinations of the main shaft 165 and the sub shaft 166 are adjusted by an adjustment mechanism that constitutes a holding member so that laser light emitted from the objective lens 19 of the optical pickup device 70 is incident on the optical disk 20 at a right angle.

  In FIG. 17, the housing 171 of the optical disk apparatus 170 is configured by combining an upper housing 171a and a lower housing 171b and fixing them together using screws or the like. The tray 172 is provided in the housing 171 so as to be able to appear and disappear. In the tray 172, an optical pickup module 160 provided with a cover 168 is arranged from the lower surface side. The cover 168 has an opening to expose the objective lens 19 of the optical pickup device 70 and the turntable 162a of the spindle motor 162. Further, in the case of the sixth embodiment, the feed motor 163 is also exposed so that the thickness of the optical pickup module 160 is reduced. The tray 172 has an opening, and exposes at least a part of the objective lens 19, the turntable 162 a, and the cover 168. The bezel 173 is provided on the front end surface of the tray 172, and is configured to close the entrance and exit of the tray 172 when the tray 172 is stored in the housing 171. The bezel 173 is provided with an eject switch 174. When the eject switch 174 is pressed, the engagement between the housing 171 and the tray 172 is released, and the tray 172 can enter and leave the housing 171. The rails 175 are slidably attached to both sides of the tray 172 and the housing 171, respectively. A circuit board (not shown) is provided inside the housing 171 and the tray 172, and a signal processing system IC, a power supply circuit, and the like are mounted thereon. The external connector 176 is connected to a power / signal line provided in an electronic device such as a computer. Then, power is supplied into the optical disc device 170 via the external connector 176, an electric signal from the outside is guided into the optical disc device 170, or an electric signal generated by the optical disc device 170 is sent to an electronic device or the like. To do.

  A flow of focus control and tracking control of the optical pickup device 70 will be described. In FIG. 18, the light with wavelength λ1 for DVD and the light with wavelength λ2 emitted from the light source 11 are separated into light used for tracking control by the diffraction grating 13 of the diffraction element 12, respectively. Incident. The reflected light reflected by the optical disk 20 is separated by the beam splitter 17 of the integrated prism 14, and the astigmatism generation element 18 is converted into light having different focal lengths in two orthogonal sections including the optical axis. Incident. The laser beam that has passed through the astigmatism generation element 18 is used for focus control. The laser beam incident on the light receiver 23 is converted into an electrical signal for DVD focus control, CD focus control, DVD tracking control, and CD tracking control, and the circuit (not shown) of the optical disc apparatus 170 main body. It is sent to the analog signal processing unit 170a on the substrate.

  The analog signal processing unit 170a performs calculation / band processing on the input signal and outputs the result to the servo processing unit 170b. The servo processing unit 170b generates a focus error signal FES and a tracking error signal TES based on the signal from the analog signal processing unit 170a and outputs the focus error signal FES and the tracking error signal TES to the motor driving unit 170c. The motor drive unit 170c generates a current for driving the objective lens drive unit 74 on which the objective lens 19 is mounted based on the input focus error signal FES and tracking error signal TES. Thereby, control is performed so that the deviation of the focal point of the light beam collected on the optical disc 20 and the deviation with respect to the track are minimized.

  The controller 170d receives signals sent from the analog signal processing unit 170a, the servo processing unit 170b, and the motor driving unit 170c. The controller 170d performs arithmetic processing of these signals, sends the result (signal) of this arithmetic processing to each unit, and controls each unit by causing each unit to drive and execute processing.

  As described above, the optical disk device 170 according to the sixth embodiment includes the optical pickup device 70 according to the first embodiment. That is, since the reflected light 27 from the L1 layer 22 is configured to be incident only on the annular zone 29 of the astigmatism generation element 18 of the optical pickup device 70, the degree of influence by the stepped portion 30 is small. Therefore, when manufacturing the optical disk device 170, the optical pickup device 70 may reduce the defect rate in the process of evaluating the characteristics by operating the objective lens 19 in the tracking direction using the optical disk 20 having a plurality of recording layers. it can. That is, in the optical pickup device 70, the reflected light 27 from the L1 layer 22 is incident only on the annular zone 29 of the astigmatism generation element 18 even when the objective lens 19 is operated in the tracking direction. As a result, the defect rate when manufacturing the optical disc apparatus 170 can be reduced. Here, the optical pickup device 70 of the first embodiment may be replaced with the optical pickup device of the second to fifth embodiments.

  As described above, the optical pickup device and the optical disc device of the present invention have a low defect rate in the process of evaluating characteristics by operating the objective lens in the tracking direction using an optical disc having a plurality of recording layers. Therefore, the optical pickup device or the optical disk device is preferably mounted on an electronic device such as a personal computer or a notebook computer.

(A) The figure which shows the path | route of the reflected light from L0 layer in the optical pick-up apparatus of this Embodiment 1, (b) The figure which shows the path | route of the reflected light from L1 layer, (c) Integration in this Embodiment 1 Prism configuration diagram (A) The figure which shows the spot of the reflected light from the L0 layer which injects into the astigmatism generation element in this Embodiment 1, (b) From the L1 layer which injects into the astigmatism generation element in this Embodiment 1 The figure which shows the spot of reflected light, (c) The figure which shows the spot of the reflected light from the L0 layer which injects into the conventional astigmatism production element, (d) From the L1 layer which injects into the conventional astigmatism production element Diagram showing the spot of reflected light (A) The figure which shows the spot of the reflected light from L1 layer on the light receiver in this Embodiment 1, (b) The figure which shows the spot of the reflected light from L1 layer on the conventional light receiver (A) Perspective configuration diagram of diffraction element in Embodiment 1, (b) Perspective view from top surface of diffraction element, (c) Cross-sectional view from side surface of diffraction element (A) Cross section of a normal mirror, (b) Cross section of a Fresnel mirror (A) Operation diagram of astigmatism generation element, (b) Diagram showing light spot shape when optical disc is near, (c) Diagram showing light spot shape when optical disc is far away Configuration diagram of an optical system in the optical pickup device of the first embodiment Configuration diagram of optical pickup device according to Embodiment 1 (A) The figure which shows the spot of the reflected light from the L0 layer which injects into the astigmatism production | generation element of the other example 1 in this Embodiment 1, (b) Astigmatism of the other example 1 in this Embodiment 1 The figure which shows the spot of the reflected light from the L1 layer which injects into an aberration generating element, (c) The spot of the reflected light from the L0 layer which injects into the astigmatism generating element of the other example 2 in this Embodiment 1 is shown. FIG. 4D shows a spot of reflected light from the L1 layer incident on the astigmatism generation element of the other example 2 in the first embodiment. (A) Cross-sectional view of a normal mirror, (b) Cross-sectional view of a Fresnel mirror in the first embodiment, (c) Cross-sectional view of the Fresnel mirror in the second embodiment (A) The figure which shows the spot of the reflected light from the L0 layer which injects into the astigmatism generation element in this Embodiment 2, (b) From the L1 layer which injects into the astigmatism generation element in this Embodiment 2. Diagram showing the spot of reflected light Configuration diagram of integrated prism in optical pickup device of Embodiment 3 The block diagram of the integrated prism of the other example in the optical pick-up apparatus of this Embodiment 3. Configuration diagram of an optical system in the optical pickup device of the fourth embodiment Configuration diagram of an optical system in the optical pickup device of the fifth embodiment Configuration diagram of optical pickup device drive section in optical disk device of Embodiment 6 Configuration diagram of optical disc apparatus of Embodiment 6 The figure which shows the flow of the servo in the optical disk apparatus of this Embodiment 6. The figure which shows the optical system structure of the conventional optical pick-up apparatus. (A) Cross-sectional view of a normal reflecting mirror, (b) Cross-sectional view of a Fresnel mirror Plan view of astigmatism generating element composed of Fresnel mirror

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Light source 12 Diffraction element 12a, 12b, 12c Substrate 13 Diffraction grating 13a DVD Diffraction grating 13b CD Diffraction grating 13c 1st uneven part 13d 1st filling part 13e 2nd uneven part 13f 2nd filling part 14 Integrated prism 15, 16 Slope 17 Beam splitter 18 Astigmatism generation element 19 Objective lens 20 Optical disk 21 L0 layer 22 L1 layer 23 Light receiver 24 Light receiving part 25 Emitted light 26, 27 Reflected light 28 Fresnel mirror 29 Ring zone 30 Step part 31 Mirror 32 Fresnel mirror 33 Ring zone 34 Stepped portion 40 Astigmatism generating element 41 Reflected light 42, 43 Cross section 44, 45 Focus 46 Spot 47 Light receiver 48 Light receiving portion 50, 51, 52, 53, 54, 55 Spot 60 Wavelength plate 61 Collimating lens 62 Rising mirror 63 Light receiver 64 Recording 70 Optical pickup device 71 Base 72 Coupling base 73 Laser module 74 Objective lens drive unit 75 Cover 80, 84, 90 Fresnel mirror 81, 85, 91 Ring zone 82, 86, 92 Stepped portion 83, 87, 93 Astigmatism Generation element 101, 111 Integrated prism 102, 112 Slope 103, 113 Beam splitter 104, 114 Sensor surface 105, 116 Astigmatism generation element 106, 117 Fresnel lens 115 Substrate 121, 131 Light source 122 Diffraction element 123 Diffraction grating 124, 132, 152 Integrated prism 125, 133, 153 Astigmatism generation element 126, 134 Light receiver 127, 135 Coupling base 128, 136 Laser module 130 154 Fresnel mirror 140 Hologram 141 Beam splitter 142 Collimating lens 143, 144 Rising mirror 145 Light receiver 146, 147 Objective lens 148 Objective lens driver 149 CD
150 DVD
151 BD
160 Optical Pickup Module 161 Base 162 Spindle Motor 162a Turn Table 163 Feed Motor 164 Screw Shaft 165 Main Shaft 166 Sub Shaft 167 Rack 168 Cover 170 Optical Disc Device 170a Analog Signal Processing Unit 170b Servo Processing Unit 170c Motor Drive Unit 170d Controller 171 Housing 171a Upper housing 171b Lower housing 172 Tray 173 Bezel 174 Eject switch 175 Rail 176 External connector

Claims (8)

A light source that generates outgoing light toward a predetermined recording layer of the optical disc;
An objective lens that focuses the emitted light on the predetermined recording layer;
A light receiver that receives the reflected light that is reflected by the predetermined recording layer and passed through the objective lens;
The focal positions in two cross-sections that are arranged between the objective lens and the light receiver and are orthogonal to each other including the optical axis of the reflected light that is focused toward the light receiver and the front side of the light receiver, respectively. An astigmatism generating element that generates light for focus control on the rear side,
The astigmatism generation element is formed on a surface, and has a plurality of annular portions and a step portion connecting the adjacent annular portions,
Regardless of the movement of the objective lens in the tracking direction, the reflected light from the recording layer on the back side of the predetermined recording layer is configured to be incident only on the annular portion in the astigmatism generation element. An optical pickup device. 2. The optical pickup device according to claim 1, wherein the astigmatism generation element is a Fresnel mirror having the annular portion as a reflecting mirror portion. 2. The optical pickup device according to claim 1, wherein the astigmatism generation element is a Fresnel lens having the annular portion as a lens portion. The annular zone is formed in a concentric elliptical shape, and the reflected light from the recording layer on the back side is incident only on the innermost annular zone regardless of the movement of the objective lens in the tracking direction. The optical pickup device according to claim 1. 5. The optical pickup device according to claim 4, wherein reflected light from the predetermined recording layer is incident on a central portion of the innermost annular zone. The light source generates second outgoing light directed to a second optical disc having only one recording layer in the vicinity of the outgoing light, and the second outgoing light is reflected light reflected by the second optical disc. The optical pickup device according to claim 5, wherein the light is incident on a position shifted from a center portion of the innermost annular zone. 2. The optical pickup device according to claim 1, wherein the height difference of the innermost ring zone portion among the ring zone portions is larger than the height difference of the stepped portion. A light source that generates outgoing light toward a predetermined recording layer of the optical disc;
An objective lens that focuses the emitted light on the predetermined recording layer;
A light receiver that receives the reflected light that is reflected by the predetermined recording layer and passed through the objective lens;
The focal positions in two cross-sections that are arranged between the objective lens and the light receiver and are orthogonal to each other including the optical axis of the reflected light that is focused toward the light receiver and the front side of the light receiver, respectively. An astigmatism generating element that generates light for focus control on the rear side,
The astigmatism generation element is formed on a surface, and has a plurality of annular portions and a step portion connecting the adjacent annular portions,
Regardless of the movement of the objective lens in the tracking direction, the reflected light from the recording layer on the back side of the predetermined recording layer is configured to be incident only on the annular portion in the astigmatism generation element. Optical disk device to perform.

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