JP2005285250A - Optical pickup and optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct or reduce astigmatism caused in the optional direction. <P>SOLUTION: The optical pickup 1 performs a recording/reproducing operation by converging a luminous flux of wavelength λ1 emitted from a light source 2 to the optical disk 10 by an objective lens 6 through a plurality of optical elements and detecting the luminous flux reflected from the optical disk 10 by a photodetector 8. In this optical pickup 1, a lens to change coma aberration and astigmatism in accordance with a viewing angle of the incident luminous flux is used for the objective lens 6, and a tilt correcting mechanism 9 for the optical pickup capable of adjusting an angle formed by the reference surface of the optical pickup 1 fixing the light source 2 and photodetector 8 thereon and the information recording surface of the optical disk 10, with respect to at least one direction in the information recording surface of the optical disk 10, and a tilt correction mechanism 7 for the objective lens capable of controlling an angle formed by the main plane of objective lens 6 and the information recording surface of the optical disk 10, with respect to at least one direction in the information recording surface of the optical disk 10, are provided to the optical pickup. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup and an optical disc drive for recording / reproducing an optical disc. More specifically, the present invention relates to a technique for improving signal quality by correcting astigmatism generated in an optical pickup optical system. is there.

  An optical disc device records and reproduces information by irradiating a recording surface on which a spiral or concentric track is formed on the optical disc, and reproduces and controls information based on reflected light from the recording surface. Signal generation is performed.

  The optical pickup is roughly composed of two optical systems. One is an illumination optical system including a light source, a plurality of optical elements that guide a light beam emitted from the light source to the objective lens, and the objective lens. The other is a detection optical system comprising a detection / separation unit that separates the reflected light beam from the objective lens into a separate optical path from the illumination optical system, a signal generation unit that divides or deforms the shape of the beam, and a divided light receiving element. .

  The light receiving element in the detection optical system outputs not only the reproduction information of the data recorded on the recording surface but also a signal (servo control signal) including information necessary for position control of the optical pickup device itself and the objective lens. Is done.

  By the way, the signal quality (reproduction signal and servo control signal) of the optical disc is largely due to the wavefront aberration of the illumination optical system. That is, if the wavefront aberration is large, the signal quality is deteriorated and it becomes difficult to record and reproduce information. It is known that the optical pickup generally requires the square average of wavefront aberration to be equal to or less than the Marechal Clarion (= 0.07λrms). The wavefront aberration in the optical pickup is dominated by third-order aberrations, and among them, power, spherical aberration, coma aberration, and astigmatism are particularly large.

  The power is corrected by moving the objective lens in the optical axis direction. With respect to coma aberration, a technique for correcting an optical disk by tilting an objective lens is generally known (see Patent Documents 1 and 2). Spherical aberration can be corrected by arranging an expander in the optical system (see Patent Document 3). Astigmatism can be suppressed by managing the individual surface accuracy to be small if the number of optical components of the optical pickup is small.

  However, in recent optical systems with a low wavelength (for example, 405 nm) aimed at increasing the capacity, the required surface accuracy becomes stricter by the wavelength ratio, and the number of optical components for correcting various aberrations is increased, resulting in sufficient astigmatism. It is difficult to make it smaller.

  By the way, in the optical system using the beam shaping means, astigmatism in 0 degree (shaping direction) or 90 degrees direction (non-shaping direction) can be corrected by adjusting the magnification of the light beam incident on the beam shaping. Is possible. Here, since the astigmatism of the optical component exists in an arbitrary direction, it is known that the astigmatism via the beam shaping means remains in the 45 degree or 135 degree direction.

  As a technique for correcting astigmatism in the direction of 45 degrees or 135 degrees when there is beam shaping, or astigmatism in any direction when there is no beam shaping, techniques described in Patent Document 4 and Non-Patent Document 1 It has been known.

  According to Patent Document 4, astigmatism of a light beam transmitted through a deflecting optical element is canceled by astigmatism generated by tilting a total reflection mirror in one direction and obliquely entering an incident light beam with respect to an objective lens. The technology is disclosed.

In Non-Patent Document 1, the astigmatism in the 45-degree direction remaining in the optical system via the beam shaping prism is shifted from the position of the light source in the emission direction with respect to the optical axis of the coupling lens, and the incident light flux to the objective lens. Is canceled by astigmatism generated by oblique incidence.
Japanese Patent No. 29224848 Japanese Patent Laid-Open No. 10-064094 JP 05-266511 A JP-A-6-89458 PIONEER R & D Vol. 11 No. 3 (Pioneer issued in November 2001)

  In recent years, optical pickups are required to be miniaturized, and a hologram unit in which a light source, a detection / separation unit, and a divided light receiving element are integrated is generally used as a means for that purpose. In such an optical system in which the illumination system and the detection system are integrated, the servo control signal is generally optimized by adjusting the dividing line of the hologram with respect to the light beam returned from the optical disk.

  However, in the optical system using the hologram unit, when the astigmatism of the illumination system described in Patent Document 4 or Non-Patent Document 1 is adjusted, a deviation occurs in the servo control signal, and position control of the objective lens is performed. May cause trouble.

  The present invention realizes reduction of astigmatism occurring in an arbitrary direction, and correction or reduction of astigmatism without degrading servo signals even in an optical system using a hologram unit. An object is to provide a pickup and an optical disk drive.

  In order to achieve the object, the invention according to claim 1 condenses a light beam of a predetermined wavelength emitted from a light source on an optical disk with an objective lens through a plurality of optical elements, and detects a light beam reflected from the optical disk with a light receiving element. Thus, in the optical pickup for recording / reproducing, the objective lens is a lens whose coma aberration and astigmatism change according to the angle of view of the incident light beam, and the light source and the light receiving element are fixed. An angle between the pickup reference surface and the information recording surface of the optical disc can be adjusted with respect to at least one direction within the information recording surface of the optical disc, and the objective lens main plane and the information recording surface of the optical disc form the optical pickup tilt correction mechanism. And an objective lens tilt correction mechanism capable of controlling the angle with respect to at least one direction within the information recording surface of the optical disc. . With this configuration, the objective lens main plane is tilted according to the tilt angle of the information recording surface of the optical disc, thereby correcting and reducing coma aberration, and at the same time, the reference plane of the optical pickup (main plane of the objective lens). Astigmatism can be corrected / reduced by inclining the surface substantially parallel to the information recording surface of the optical disc in accordance with the astigmatism of the optical system. Further, in this astigmatism adjustment, since the entire optical system of the optical pickup is tilted, there is an effect that the optical axis shift does not occur in the illumination system and the detection system.

  According to a second aspect of the present invention, in the first aspect of the invention, the objective lens tilt correction mechanism is provided with a follow-up means for performing variable control according to the inclination of the information recording surface of the optical disc in the circumference or the inner and outer circumferences. It is characterized by. In this way, by detecting the relative tilt between the objective lens and the optical disk and correcting the objective lens tilt using the result, there is no offset even when the astigmatism is adjusted. It is possible to correct aberrations.

  The invention according to claim 3 is characterized in that, in the invention according to claim 1, the optical pickup tilt correction mechanism is provided with an adjusting means capable of fixing after adjusting astigmatism. As described above, once the astigmatism is adjusted, the astigmatism shift with time can be prevented by fixing the optical pickup tilt correction mechanism.

  The invention according to claim 4 has at least two light sources having different wavelengths, and a light beam emitted from each light source is condensed on an optical disk by a single objective lens via a plurality of optical elements and reflected from the optical disk. In the optical pickup that performs recording / reproduction by detecting the light beam with a light receiving element, the objective lens and at least the lens that changes coma and astigmatism according to the angle of view of the light beam incident from the light source with the shortest wavelength, An optical pickup tilt correction mechanism capable of adjusting an angle between a reference surface of an optical pickup on which the light source and the light receiving element are fixed and an information recording surface of the optical disc with respect to at least one direction in the information recording surface of the optical disc; Objective lens capable of controlling the angle between the main plane and the information recording surface of the optical disc in at least one direction within the information recording surface of the optical disc Characterized in that a belt correction mechanism. As described above, in an optical pickup having a plurality of light sources having different wavelengths, coma aberration is corrected by tilting the main plane of the objective lens according to the tilt angle of the information recording surface of the optical disc with respect to the optical system having the shortest wavelength. At the same time, the reference surface of the optical pickup (a surface substantially parallel to the main plane of the objective lens) is tilted with respect to the information recording surface of the optical disc in accordance with the astigmatism of the optical system while reducing. Astigmatism can be corrected and reduced. Further, in this astigmatism adjustment, since the entire optical system of the optical pickup is tilted, there is an effect that the optical axis shift does not occur in the illumination system and the detection system.

  According to a fifth aspect of the present invention, in the invention according to the fourth aspect, when a light flux having the shortest wavelength is selected for the objective lens tilt correction mechanism, the optical recording medium has an information recording surface according to an inclination of an inner circumference or an inner circumference. A follow-up means capable of performing variable control is provided. As described above, even when the astigmatism is adjusted by detecting the relative tilt of the objective lens and the optical disc with respect to the optical system having the shortest wavelength and correcting the objective lens tilt using the result. It is possible to correct coma with high accuracy without causing an offset.

  According to a sixth aspect of the invention, in the fourth aspect of the invention, when the optical pickup tilt correction mechanism selects a light beam from a wavelength other than the shortest wavelength, the variable control is performed according to the inclination of the inner and outer circumferences of the optical disk. It is characterized by comprising a follow-up means capable of performing the above. As described above, coma aberration can be corrected by detecting the tilt of the optical disc with respect to an optical system having a long wavelength and correcting the optical pickup tilt using the result.

  According to a seventh aspect of the present invention, in the invention according to the sixth aspect, when a light flux having the shortest wavelength is selected for the optical pickup tilt correction mechanism, an angle formed by the reference surface of the optical pickup and the information recording surface of the optical disk is set. It is characterized by having a stationary means that can be fixed. As described above, the astigmatism shift with time can be prevented by adjusting the astigmatism once for the optical system having the shortest wavelength and then fixing the optical pickup tilt correction mechanism.

  According to an eighth aspect of the invention, there is provided the optical pickup tilt correction mechanism according to any one of the first to seventh aspects, wherein the optical pickup tilt correction mechanism has a reference for the optical pickup with respect to two different directions in the information recording surface of the optical disc. Means for adjusting the angle formed by the surface and the information recording surface of the optical disc, and the objective lens tilt correction mechanism is configured to record information on the objective lens main plane and the optical disc in two different directions within the information recording surface of the optical disc. Means for controlling the angle formed by the surfaces is provided. With this configuration, the angle formed by the objective lens main plane and the information recording surface of the optical disk is inclined in an arbitrary direction within the information recording surface of the optical disk, and at the same time, in an arbitrary direction within the information recording surface of the optical disk. Since the angle formed by the information recording surface of the optical disc and the reference surface of the optical pickup can be inclined, astigmatism occurring in an arbitrary direction can be corrected and reduced.

  According to a ninth aspect of the present invention, in the optical disk drive, the optical pickup according to any one of the first to eighth aspects is mounted. As described above, since the drive equipped with the optical pickup according to any one of claims 1 to 8 can sufficiently reduce coma and astigmatism, the signal quality (jitter and CN characteristics of the RF signal) is good. Can provide a drive.

  According to the present invention, the main plane of the objective lens is tilted according to the tilt angle of the information recording surface of the optical disc, thereby correcting and reducing coma aberration, and at the same time, the reference plane of the optical pickup (with respect to the main plane of the objective lens). Astigmatism can be corrected and reduced by inclining the substantially parallel surface) with respect to the information recording surface of the optical disc in accordance with the astigmatism of the optical system.

  Further, in this astigmatism adjustment, since the entire optical system of the optical pickup is tilted, there is an effect that the optical axis shift does not occur in the illumination system and the detection system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is an explanatory diagram showing a schematic configuration of an optical pickup according to Embodiment 1 of the present invention. The optical pickup 1 includes a light source 2 that emits divergent light having a wavelength λ1, detection / separation means 3 that is disposed on the optical path of divergent light from the light source 2, and a divergent light from the light source 2 that is substantially parallel. The coupling lens 4, the objective lens 6 for converging the parallel light beam into a minute spot, the parallel light beam from the coupling lens 4 is deflected to the objective lens 6, and the light beam reflected from the optical disk 10 is deflected to the coupling lens 4 side. A deflecting unit 5, an objective lens tilt correction mechanism 7 that can tilt the objective lens 6, and a light receiving element 8 that detects a light beam reflected from the optical disk 10 are provided.

  As the objective lens 6, a lens in which coma aberration and astigmatism change according to the angle of view of the incident light beam is used. Any configuration is acceptable.

  A light source 2, a light receiving element 8, and the like are fixed to a reference surface of the optical pickup 1, and the optical pickup 1 is supported by an optical pickup tilt correction mechanism 9 that can be tilted with respect to the optical disk 10. The objective lens 6 is supported on the optical pickup 1 by an objective lens tilt correction mechanism 7 so that the objective lens 6 can be tilted independently of the optical pickup 1.

  The optical pickup tilt correction mechanism 9 includes a mechanism for correcting tilt in the radial direction that is the circumferential direction of the optical disc 10 and the tangential direction that is orthogonal to the radial direction. The tilt angles in the radial and tangential two directions can be arbitrarily set. By tilting the optical pickup 1, the optical pickup 1 can be tilted in an arbitrary direction on the surface of the optical disc 10.

  The objective lens tilt correction mechanism 7 is also provided with a mechanism for tilt correction in the radial direction that is the circumferential direction of the optical disc 10 and the tangential direction orthogonal thereto, and the tilt angles in the radial and tangential two directions can be arbitrarily set, respectively. By tilting, the objective lens 6 can be tilted in an arbitrary direction on the surface of the optical disk 10.

  FIG. 2 is an explanatory diagram of the objective lens tilt correction mechanism. The objective lens 6 is installed in the objective lens movable unit 11. Further, magnets 12 are arranged in the radial direction that is the circumferential direction of the optical disk of the objective lens movable portion 11 and in the tangential direction orthogonal thereto. The objective lens fixing portion 13 is provided with a coil 14, and a current flows through the coil 14. The objective lens movable unit 11 is inclined by the principle of the lever by receiving a force from the current flowing through the coil 14 and the magnetic field of the magnet 12. By changing the direction and magnitude of the current flowing through the coil 14, the tilt of the objective lens 6 can be changed at high speed.

  The optical pickup 1 is separately provided with a tilt detection element for detecting the tilt of the main plane of the objective lens 6 and a tilt detection element for detecting the tilt of the information recording surface of the optical disc 10. The objective lens tilt correction mechanism 7 is driven based on the result of each tilt detection element.

  FIG. 3 is a side view showing a schematic configuration of the optical pickup tilt correction mechanism, and FIG. 4 is a plan view showing the overall configuration of the optical pickup tilt correction mechanism.

  As shown in FIG. 3, the optical pickup 1 is installed in the movable chassis 15. The movable chassis 15 is supported by a tilt adjusting screw 17 and a support portion 18 provided on the fixed chassis 16. By moving the tilt adjusting screw 17 up and down, the optical pickup 1 is tilted together with the movable chassis 15.

  The overall configuration of the optical pickup tilt correction mechanism 9 will be described with reference to FIG. An optical pickup tilt correction mechanism 9 is provided in the radial and tangential directions of the movable chassis 15. Thereby, the tilt of the movable chassis 15 and the fixed chassis 16 can be changed in an arbitrary direction. The fixed chassis 16 is provided with a spindle motor 19, and the inclination between the fixed chassis 16 and the optical disk installed on the spindle motor 19 is kept constant. Therefore, the optical pickup 1 can be tilted with respect to the optical disc.

  The optical pickup tilt correction mechanism 9 uses a means for increasing the coefficient of friction such as an adhesive so that the adjustment screw does not move after adjustment to minimize astigmatism occurring in the optical system of the optical pickup 1. To fix.

  Next, the astigmatism correction principle in the present embodiment will be described with reference to FIGS. 1 and 10 to 13.

  FIG. 10 is a diagram showing aberration characteristics with respect to the optical disc tilt when the objective lenses described in (Table 1) and (Table 2) are used. (Table 2) shows the aspheric coefficients of S1 and S2 in (Table 1).

  As shown in FIG. 10, coma aberration occurs when the optical disc tilt increases. FIG. 11 is a diagram showing aberration characteristics with respect to the objective lens tilt when the objective lenses described in (Table 1) and (Table 2) are used. As the objective lens tilt increases, astigmatism (AS) occurs along with coma. By utilizing this property and tilting the objective lens 6 together with the optical pickup 1, only astigmatism can be generated.

  FIG. 12 is a diagram showing the astigmatism characteristics when the reference surface of the optical pickup that fixes the light source and the light receiving element and the principal plane of the objective lens are simultaneously tilted with respect to the optical disc information recording surface. The reference plane of the optical pickup 1 and the tilt of the main plane of the objective lens 6 are tilted by the optical pickup tilt correction mechanism 9 and the objective lens tilt correction mechanism 7, respectively. As a result, coma is almost cancelled, while astigmatism increases with tilt. By utilizing this astigmatism, it is possible to cancel the astigmatism of the optical pickup 1.

  FIG. 13 shows a state in which astigmatism is corrected by tilting the optical pickup reference surface and the objective lens with respect to the optical disk information recording surface when the optical pickup optical system has astigmatism. FIG. It can be seen that the post-correction Δ mark has changed to almost zero compared to the astigmatism correction- ● mark.

  In order to create such a state in which astigmatism is reduced together with coma aberration, an angle at which coma aberration is minimized with respect to the information recording surface of the optical disk 10 with respect to the main surface of the objective lens 6 (0 in the above-described working example). The angle at which the astigmatism is minimized with respect to the information recording surface of the optical disc, with respect to the reference surface of the optical pickup 1 (a surface substantially parallel to the main plane of the objective lens 6). In the example, it is sufficient to incline to the corrected PU tilt amount * marked in FIG.

  Incidentally, in order to correct astigmatism occurring in an arbitrary direction, a mechanism for tilting the tilt of the optical pickup 1 and the objective lens 6 in an arbitrary direction is required. According to the first embodiment, the objective lens tilt correction mechanism 7 tilts the main plane of the objective lens 6 in the radial direction and the tangential direction with respect to the optical disk information recording surface, and the optical pickup tilt correction mechanism 9 Is inclined in the radial direction and the tangential direction with respect to the information recording surface of the optical disc 10. Therefore, by tilting the radial tangential at the same time, it is possible to generate the tilt of the optical pickup and the objective lens in an arbitrary direction. Therefore, according to the first embodiment, it is possible to correct astigmatism in all directions generated in the optical system of the optical pickup 1.

  In general, the optical disk 10 has a tilt within one circumference and a tilt amount between the inner and outer circumferences due to warping of the surface. Therefore, it is necessary to correct the coma aberration generated with the rotation of the optical disc 10 in a state where the astigmatism is corrected at a high speed. In the optical pickup 1 according to the first embodiment, the optical pickup reference surface is inclined with respect to the optical disc 10 in order to correct astigmatism. Therefore, the objective lens 6 is inclined, and only the inclination amount of the optical disc 10 is detected. If corrected, an offset occurs in coma.

  Therefore, first, the tilt detection of the objective lens 10 is performed simultaneously with the tilt detection of the optical disc 10. Then, the relative inclination between the objective lens 6 and the optical disc 10 is detected by performing a differential operation between them. By correcting the objective lens tilt with respect to the optical disc 10 with respect to the relative tilt between the objective lens 6 and the optical disc 10, the coma aberration caused by the tilt of the optical disc 10 can be accurately corrected.

  Since astigmatism hardly fluctuates depending on the optical disk 10, once it is corrected for astigmatism occurring in the optical pickup optical system, it does not need to be adjusted later. For this reason, the optical pickup tilt correction mechanism 9 first adjusts the reference surface of the optical pickup so that the astigmatism is minimized with respect to the information recording surface of the optical disc, and then completely fixes the optical pickup reference surface. Deviation can be prevented.

  Next, the second embodiment will be described by limiting to an optical pickup using light beams having wavelengths λ1 and λ2. Note that when the number of light sources having three or more wavelengths increases, it can be easily realized by increasing the number of optical systems having the same configuration as the wavelength λ2, and therefore the description of the multi-wavelength optical pickup is omitted. To do.

(Embodiment 2)
FIG. 5 is an explanatory diagram showing a schematic configuration of the optical pickup according to the second embodiment of the present invention. The optical pickup 20 includes at least a light source that emits divergent light having a wavelength λ1 and a hologram unit 21 that includes a light receiving element, a coupling lens 22 that converts the light into a substantially parallel light beam, and a light source that emits divergent light having a wavelength λ2. And a hologram unit 23 including a light receiving element, a coupling lens 24 for making it a substantially parallel light beam, an optical path combining prism 25 for combining a light beam with a wavelength λ1 and a light beam with a wavelength λ2, and a small amount of each parallel light beam The objective lens 26 for focusing on the spot, the deflecting means 28 for deflecting the parallel light beam from the optical path combining prism 25 to the objective lens 26, the light beam reflected from the optical disc 10 toward the optical path combining prism 25, and the objective lens 26 are tilted. And an objective lens tilt correction mechanism 27 capable of performing the above-described operation.

  The objective lens 26 is the same as the objective lens 6 of the first embodiment shown in FIG. 1, and the objective lens tilt correction mechanism 27 has the same configuration as the objective lens tilt correction mechanism 7 of the first embodiment shown in FIG. Therefore, the description is omitted.

  Hologram units 21 and 23 are fixed to the reference surface of the optical pickup 20, and the optical pickup 20 is supported by an optical pickup tilt correction mechanism 29 that can be tilted with respect to the optical disc 30. Similarly to the optical pickup tilt correction mechanism 9 of the first embodiment shown in FIGS. 1 and 4, the optical pickup tilt correction mechanism 29 also has a radial direction that is the circumferential direction of the optical disc 30 and a tangential direction that is orthogonal thereto. A tilt correction mechanism is provided, and the optical pickup 20 can be tilted in any direction on the surface of the optical disc 30 by arbitrarily tilting the tilt angles in the radial and tangential two directions.

  The optical pickup 20 is separately provided with a tilt detection element for detecting the tilt of the main plane of the objective lens 26 and a tilt detection element for detecting the tilt of the information recording surface of the optical disc 30. When the light flux of λ1 is selected, the objective lens tilt correction mechanism 27 is driven based on the result of each tilt detection element.

  FIG. 6 is a perspective view showing a main part of the optical pickup tilt correction mechanism of FIG. The optical pickup tilt correction mechanism 29 according to the second embodiment includes a motor 31, a gear 32, and a slope as shown in FIG. 6 instead of the tilt adjustment screw 17 in the optical pickup tilt correction mechanism 9 according to the first embodiment shown in FIG. The movable chassis 34 is driven by the conversion gear 33 having the above. That is, a part of the movable chassis 34 is brought into contact with the slope of the conversion gear 33 and the motor 31 is rotated, whereby the gear 32 and the conversion gear 33 are rotated and the movable chassis 34 is moved up and down. Since the movable chassis 34 moves up and down only at one corner, as a result, the entire movable chassis 34 is inclined with respect to the fixed chassis.

  Further, when the wavelengths λ2... Λn are selected, the optical pickup tilt correction mechanism 29 is controlled based on the signal received from the tilt detection element for detecting the tilt of the information recording surface of the optical disc 30. The optical pickup tilt correction mechanism 29 determines the angle formed by the information recording surface of the optical disc 30 and the reference surface of the optical pickup 20 when the wavelength λ1 is selected by the tilt detection element of the optical pickup 20 astigmatism of the optical system. It is necessary to fix after tilting to an angle that minimizes. Only the optical pickup tilt correction shown in FIG. 6 may cause the tilt to move due to disturbance (impact, vibration, etc.). As shown in FIG. 7, a worm gear having a high reduction ratio is provided between the shaft of the motor 31 and the gear. It is desirable to use a configuration such as using a stepping motor.

  By the way, the surface accuracy allowed for the optical component of the optical pickup becomes more severe as the wavelength of the light source is shorter. That is, when the surface accuracy is the same with respect to the light flux of each wavelength, the deterioration of the wavefront aberration becomes larger as the light flux has a shorter wavelength. For this reason, in an optical pickup having light sources with a plurality of wavelengths, astigmatism is optimized when the light source having the shortest wavelength λ1 is selected.

  Further, like the astigmatism, the coma aberration requires a higher accuracy as the wavelength is shorter. For this reason, for a light beam having a short wavelength λ1, the tilt within one circumference and the tilt between the inner and outer circumferences caused by distortion and warpage of the surface of the optical disk are corrected. Therefore, it is necessary to correct the coma generated with the rotation of the optical disk at a high speed while correcting the astigmatism. In the optical pickup according to the second embodiment, the optical pickup reference plane is inclined with respect to the optical disk in order to correct astigmatism. Therefore, the objective lens is inclined, and only the inclination amount of the optical disk is detected and corrected. An offset occurs in the coma aberration.

  Therefore, the tilt detection of the objective lens is performed simultaneously with the tilt detection of the optical disc. And the relative inclination of an objective lens and an optical disk is detected by performing the differential calculation. By correcting the objective lens tilt with respect to the optical disc with respect to the relative tilt between the objective lens and the optical disc, the coma aberration caused by the tilt of the optical disc can be accurately corrected.

  Further, when a light beam having a long wavelength of λ2... Λn is selected, it is not necessary to correct astigmatism, and it is not necessary to correct coma for the circumference of the optical disc. In other words, the aberration to be corrected only needs to be tilt correction caused by warpage in the inner and outer circumferences of the optical disk. In this case, it is desirable to correct the coma aberration only by optical pickup tilt correction. That is, the objective lens tilt correction mechanism 27 is fixed, and the optical pickup tilt correction mechanism 29 is variably controlled according to the optical disc tilt. Thereby, coma aberration due to the disc tilt can be sufficiently suppressed for the wavelengths λ2.

  The proper use of the aberration correction mechanism at each wavelength in the second embodiment is as shown in (Table 3).

  FIG. 8 is a block diagram showing the configuration of the optical disk drive of the present invention, and 51 shows an optical pickup having the same configuration as the optical pickup 20 shown in FIG.

  The emitted light of the semiconductor laser mounted on the optical pickup 51 is detected by a front monitor photodiode mounted on the optical pickup 51 and controlled by a laser controller 54 via a signal processing circuit 62. Driven.

  The light beam reflected from the surface of the optical disk 50 is detected by the divided light receiving element mounted on the optical pickup 51 and input to the signal processing circuit 62. The signal processing circuit 62 generates a focus error signal for focusing the objective lens and a track error signal for tracking the objective lens. The objective lens actuator mounted on the optical pickup 51 is controlled by the Fo controller 52 and the Tr controller 53, and is driven by the ACT driver 56. A reproduction signal is output from the signal processing circuit 62 according to the information recording surface.

  A spindle motor 59 that rotates the optical disk 50 is controlled by a spindle controller 55 and driven by a spindle driver 58.

  The optical disc tilt signal output from the optical pickup 51 is sent to the objective lens tilt controller 60 via the signal processing circuit 62. The objective lens tilt controller 60 generates a correction amount signal from the sent signal and sends it to the objective lens tilt driver 61. The objective lens tilt driver 61 generates a current to be passed through the tilt correction coil 14 (see FIG. 2) of the objective lens tilt correction mechanism 7 shown in FIG. 1 and sends it to the objective lens tilt correction mechanism 7 to control the tilt of the objective lens. I do.

  As described above, in a drive including the optical pickup 51 of a single light source, the tilt adjustment of the optical pickup 51 is performed at an angle at which astigmatism is minimized. On the other hand, the tilt correction of the objective lens is performed via the signal processing circuit 62, the objective lens tilt controller 60, and the objective lens tilt driver 61 based on the optical disc tilt signal obtained from the optical disc tilt detection element provided in the optical pickup 1. Control is performed to minimize coma.

  FIG. 9 is an explanatory diagram of an optical disk drive equipped with an optical pickup having a light source having two or more wavelengths, 51 is the same optical pickup as the optical pickup 20 shown in FIG. 5, and 65 is an optical pickup tilt correction mechanism 29 shown in FIG. The same optical pickup tilt correction mechanism is shown. In addition, about the member same as the member shown in FIG. 8, or the member of the same function, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  When the light source of wavelength λ1 is selected in the optical pickup 51, the optical pickup tilt correction mechanism 65 monitors the data read signal and the servo signal immediately after the optical pickup 51 is mounted on the drive, and is set to the optimum It is fixed after moving to a certain angle. The optical disc tilt signal output from the optical pickup 51 is sent to the objective lens tilt controller 60 via the signal processing circuit 62. The objective lens tilt controller 60 generates a correction amount signal from the sent signal and sends it to the objective lens tilt driver 61. The objective lens tilt driver 61 generates a current that flows through the coil 14 for tilt correction of the objective lens (see FIG. 2), sends it to the objective lens tilt correction mechanism, and performs tilt control of the objective lens.

  When a light source with wavelengths λ2... Λn is selected, the objective lens tilt correction mechanism 27 (see FIG. 5) is set by monitoring the data read signal and servo signal immediately after the optical pickup 51 is mounted on the drive. It is controlled to maintain the optimum angle. The optical disc tilt signal output from the optical pickup 51 is sent to the optical pickup tilt controller 63 via a signal processing circuit. The optical pickup tilt controller 63 generates a correction amount signal from the sent signal and sends it to the optical pickup tilt driver 64. The optical pickup tilt driver 64 generates a current that flows to the tilt adjustment motor of the optical pickup 51 and sends the current to the optical pickup tilt correction mechanism 65 to perform tilt control of the optical pickup.

  In the case of an optical pickup having a plurality of light sources, the optical pickup tilt correction mechanism 65 is fixed after being moved to an angle at which astigmatism is minimized for the light beam having the shortest wavelength λ1. Then, based on the tilt signal obtained from the differential calculation of the objective lens tilt sensor and the optical disc tilt sensor, the tilt correction of the objective lens is performed via the signal processing circuit 62, the objective lens tilt controller 60, and the objective lens tilt driver 61. The control for minimizing the coma aberration is performed.

  When the wavelengths λ2... Λn are selected, the objective lens tilt correction mechanism 65 monitors the data read signal and the servo signal immediately after the optical pickup 51 is mounted on the drive, and maintains the set optimum angle. To be controlled. Based on the optical disc tilt signal obtained from the optical disc tilt sensor, tilt correction of the optical pickup 51 is performed via the signal processing circuit 62, the optical pickup tilt controller 63, and the optical pickup tilt driver 64, and coma aberration is minimized. Control is performed.

  The present invention is applicable to an optical pickup, an optical pickup drive, an optical disc inspection machine, and the like for recording / reproducing an optical disc.

Explanatory drawing which shows schematic structure of the optical pick-up in Embodiment 1 of this invention. Explanatory drawing of objective lens tilt correction mechanism Side view showing schematic configuration of optical pickup tilt correction mechanism The top view which shows the whole structure of an optical pick-up tilt correction mechanism Explanatory drawing which shows schematic structure of the optical pick-up in Embodiment 2 of this invention. The perspective view which shows the principal part of the optical pick-up tilt correction mechanism of FIG. Explanatory drawing which shows the other structure of the principal part of the optical pick-up tilt correction mechanism of FIG. FIG. 8 is a block diagram showing the configuration of the optical disk drive of the present invention. FIG. 9 is an explanatory diagram of an optical disk drive equipped with an optical pickup having a light source having two or more wavelengths. The figure which shows the aberration characteristic with respect to optical disk tilt when the objective lens described in (Table 1) and (Table 2) is used. The figure which shows the aberration characteristic with respect to the objective lens tilt at the time of using the objective lens described in (Table 1) and (Table 2). The figure showing the astigmatism characteristics when the reference plane of the optical pickup that fixes the light source and the light receiving element and the principal plane of the objective lens are simultaneously tilted with respect to the optical disc information recording surface The figure which shows a mode when astigmatism is corrected by tilting the optical pickup reference surface and the objective lens with respect to the optical disc information recording surface when the optical pickup optical system has astigmatism.

Explanation of symbols

1, 20, 51 Optical pickup 2 Light source 3 Detection / separation means 4, 22, 24 Coupling lens 5, 28 Deflection means 6, 26 Objective lens 7, 27 Objective lens tilt correction mechanism 8 Light receiving element 9, 29 Optical pickup tilt correction mechanism DESCRIPTION OF SYMBOLS 10, 30, 50 Optical disk 11 Objective lens movable part 12 Magnet 13 Objective lens fixed part 14 Coil 15 Movable chassis 16 Fixed chassis 17 Tilt adjustment screw 18 Support part 19,59 Spindle motor 21, 23 Hologram unit 25 Optical path synthesis prism 52 Fo controller 53 Tr Controller 54 Laser Controller 55 Spindle Controller 56 ACT Driver 57 Laser Driver 58 Spindle Driver 60 Tilt Controller 61 Objective Lens Tilt Driver 62 Signal Processing Circuit 6 The optical pick-up tilt controller 64 the optical pick-up tilt driver

Claims (9)

In an optical pickup that performs recording / reproduction by converging a light beam of a predetermined wavelength emitted from a light source onto an optical disk with an objective lens via a plurality of optical elements, and detecting a light beam reflected from the optical disk with a light receiving element.
The objective lens is a lens that changes coma and astigmatism according to the angle of view of the incident light beam,
An optical pickup tilt correction mechanism capable of adjusting an angle between a reference surface of the optical pickup to which the light source and the light receiving element are fixed and an information recording surface of the optical disc with respect to at least one direction in the information recording surface of the optical disc; An optical pickup comprising an objective lens tilt correction mechanism capable of controlling an angle formed between an objective lens main plane and an information recording surface of an optical disc in at least one direction within the information recording surface of the optical disc.   2. The optical pickup according to claim 1, wherein the objective lens tilt correction mechanism is provided with tracking means for performing variable control in accordance with the inclination of the information recording surface of the optical disk in accordance with the inclination of the inner periphery or the inner periphery.   The optical pickup according to claim 1, wherein the optical pickup tilt correction mechanism includes an adjusting unit that can be fixed after adjusting astigmatism. Having at least two light sources having different wavelengths, the light beam emitted from each light source is condensed on the optical disk by a single objective lens through a plurality of optical elements, and the light beam reflected from the optical disk is detected by the light receiving element. With an optical pickup that performs recording and playback,
The objective lens and at least a lens that changes coma and astigmatism according to the angle of view of a light beam incident from a light source having the shortest wavelength,
An optical pickup tilt correction mechanism capable of adjusting an angle between a reference surface of an optical pickup to which the light source and the light receiving element are fixed and an information recording surface of the optical disc with respect to at least one direction in the information recording surface of the optical disc;
An optical pickup comprising an objective lens tilt correction mechanism capable of controlling an angle formed between an objective lens main plane and an information recording surface of an optical disc in at least one direction within the information recording surface of the optical disc.   The objective lens tilt correction mechanism includes a follow-up means capable of performing variable control in accordance with the inclination of the information recording surface of the optical disc in the circumference or the inner and outer circumferences when a light beam having the shortest wavelength is selected. The optical pickup according to claim 4.   The optical pickup tilt correction mechanism includes a follow-up unit capable of performing variable control according to the inclination of the inner and outer circumferences of the optical disc when a light beam is selected from wavelengths other than the shortest wavelength. Item 5. The optical pickup according to Item 4.   7. The optical pickup tilt correcting mechanism includes a stationary unit capable of fixing an angle formed by a reference surface of the optical pickup and an information recording surface of the optical disc when a light beam having the shortest wavelength is selected. The optical pickup described.   The objective lens tilt correction mechanism is provided with means for adjusting an angle formed by the reference surface of the optical pickup and the information recording surface of the optical disc with respect to two different directions in the information recording surface of the optical disc. 8. An apparatus according to claim 1, further comprising means for controlling an angle formed by the objective lens main plane and the information recording surface of the optical disc in two different directions in the information recording surface of the optical disc. The optical pickup according to claim 1.   An optical disk drive comprising the optical pickup according to any one of claims 1 to 8.

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