JP2010198705A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup which corrects the coma aberration produced when moving the objective lens radially on an optical disk. <P>SOLUTION: This optical pickup includes a liquid crystal aberration correction element 6 in the optical path of the laser beam to correct the spherical aberration, and a data memory circuit 26 storing the spherical aberration correction data to correct the spherical aberration developed by the temperature changes of the objective lens 8 and the coma aberration correction data to correct the coma aberration produced by the radial displacement and temperature changes of the objective lens 8. It corrects the coma aberration produced as the objective lens 8 radially moves by controlling the optical axis of the objective lens 8 through controlling and driving the tilt coil 13 based on the coma aberration correction data stored in the data memory 26. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup device that performs reading operation of a signal recorded on an optical disc and recording operation of a signal on an optical disc by laser light.

  2. Description of the Related Art Optical disk apparatuses that can perform signal reading operation and signal recording operation by irradiating a signal recording layer of an optical disk with laser light emitted from an optical pickup device have become widespread.

  As an optical disk apparatus, an apparatus using an optical disk called a CD or a DVD is generally widespread. Recently, an optical disk with improved recording density, that is, an apparatus using a Blu-ray standard optical disk has been developed.

  As a laser beam for performing a read operation of a signal recorded on a CD standard optical disc, an infrared light having a wavelength of 780 nm is used. As a laser beam for performing a read operation of a signal recorded on a DVD standard optical disc, , Red light having a wavelength of 650 nm is used.

  Laser light having a short wavelength, for example, blue light having a wavelength of 405 nm, is used as a laser beam for performing a reading operation of a signal recorded on a Blu-ray standard optical disk for such CD standard and DVD standard optical disks. Has been.

  The thickness of the protective layer provided on the upper surface of the signal recording layer in the Blu-ray standard optical disc is 0.1 mm, and the aperture of the objective lens used to read out signals from the signal recording layer The number is set to 0.85.

  In the optical pickup device corresponding to the optical disc standard in which the recording density is improved, the optical characteristics required for improving the signal recording quality are becoming stricter as the recording density is improved. That is, in order to perform a signal reading operation and a signal recording operation that are recorded at a high density, it is necessary to make the shape of the spot generated on the signal recording layer by laser irradiation favorable.

  Aberrations such as spherical aberration, astigmatism, and coma aberration have an adverse effect on the spot shape. As a method for correcting such aberration, a control voltage is applied to an electrode pattern provided in advance to correct the aberration. A method of using a liquid crystal aberration correction element capable of correcting the aberration by changing the refractive index by applying the light and adding a phase difference to the transmitted laser light, or changing the distance between the two lenses. A method of using an aberration correction means called a beam expander that corrects the spherical aberration on the disk surface by changing the light divergence angle is adopted in many optical pickup apparatuses.

  In addition, the optical pickup device controls the drive current supplied to the laser diode so that the laser output suitable for reading the signal recorded on the optical disk and the laser output suitable for recording the signal on the optical disk can be obtained. It is configured to be able to.

Then, a control operation for focusing the spot of the laser beam emitted from the optical pickup device on the signal recording layer of the optical disc, that is, a focusing control operation or a control operation for tracking the spot of the laser beam to the signal track, that is, a tracking control operation is performed. It is configured to be able to.

  In the optical disk apparatus, the optical disk is mounted on a turntable that is rotationally driven by a spindle motor and is rotationally driven. However, due to warpage of the optical disk itself, the mounting state on the turntable, and mechanical errors. Tilt occurs on the optical disc. When the optical disc is tilted, the tilt of the optical axis of the laser beam with respect to the signal surface of the optical disc deviates from the optimum state.

  As the density of the signals recorded on the optical disc increases, the optical axis shift of the laser beam with respect to the signal surface of the optical disc described above becomes a big problem. An optical axis of a laser beam is provided by selecting and controlling a drive signal supplied to the focus coil by providing a tilt coil capable of performing a tilt adjustment operation, that is, a tilt coil capable of performing a so-called tilt control operation, and a plurality of focus coils. The thing which can adjust inclination is developed.

  In addition, the optical pickup device includes an objective lens that focuses the laser light emitted from the laser diode onto the signal recording layer of the optical disk. However, the objective lens is lighter and cheaper than a glass lens. For some reason, plastic lenses are used. However, such a plastic lens has a characteristic that the shape of the lens changes with a change in temperature. Therefore, there is a disadvantage that the optical characteristics of the lens change greatly and the above-mentioned aberration occurs.

  In the optical pickup device, the objective lens temperature changes because not only the ambient temperature changes, but also the lens holder on which the objective lens is fixed is displaced for focus control operation, tracking control operation, and tilt control operation. The heat generated from each drive coil provided for the purpose of generating the laser light and the heat generated by the driving operation of the laser diode that emits the laser light can be considered.

JP 2007-122842 A JP 2004-127422 A

  FIG. 3 illustrates a liquid crystal aberration correction element that is provided in an optical path between a laser diode that emits laser light and an objective lens that focuses the laser light on a signal recording layer of an optical disc and corrects spherical aberration. FIG. As is clear from the figure, a plurality of annular transparent electrode patterns are formed around the optical axis center P.

  That is, it is configured to correct the spherical aberration caused by the change in the thickness of the signal recording layer of the optical disc by changing the refractive index by selectively controlling the drive voltage supplied to the transparent electrode. ing.

  FIG. 4 is a diagram for explaining the relationship between the displacement operation of the objective lens and the liquid crystal aberration correction element. In the figure, the position of the objective lens indicated by a solid line indicates a reference position with respect to the main body constituting the optical pickup device, that is, a position not displaced in the radial direction of the optical disk, and is the center of the optical axis of the objective lens. Q is configured to be coaxial with the optical axis center P of the liquid crystal aberration correcting element described above.

  Spherical aberration can be accurately corrected if the optical axis center Q of the objective lens and the optical axis center P of the liquid crystal aberration correction element are coaxial, but tracking can be performed as the optical disk rotates due to eccentricity of the optical disk. When the deviation occurs, the objective lens is displaced in the radial direction of the optical disk, that is, in the direction of arrow A in FIG.

  In FIG. 4, when the objective lens is displaced to the position indicated by the broken line, the optical axis center of the objective lens moves from the position indicated by Q to the position indicated by R. When the objective lens is displaced to such a position, the optical axis center R of the objective lens is shifted from the optical axis center P of the liquid crystal aberration correction element, so that coma aberration occurs.

  A technique for correcting such coma aberration is described in Patent Document 1, but with such a configuration, not only the pattern shape of the transparent electrode formed on the liquid crystal aberration correction element is complicated, but also high accuracy. Since the control operation is required, there is a problem that it is not practical.

  In addition, since the aberration correction operation cannot be performed with respect to the temperature change of the objective lens, there is a problem that it is not possible to provide an optical pickup device suitable for an optical disc capable of performing a high density recording / reproducing operation.

  The present invention is intended to provide an optical pickup device that can solve such a problem.

  The optical pickup device of the present invention is provided in the optical path of laser light guided from the laser diode to the objective lens, and is provided for detecting the temperature of the objective lens, and a liquid crystal aberration correcting element for correcting spherical aberration. The temperature detection element, spherical aberration correction data for correcting spherical aberration due to temperature change of the objective lens, displacement amount in the radial direction of the objective lens and coma aberration correction data for correcting coma aberration due to temperature change are stored. An aberration correction data memory circuit is provided, and the spherical aberration caused by the temperature change of the objective lens is corrected by the control operation for the liquid crystal aberration correction element based on the spherical aberration correction data stored in the aberration correction data memory circuit. Together with the aberration correction data memory for coma that occurs with the displacement of the objective lens in the radial direction. It is configured to correct at the optical axis control operation of the objective lens by the drive control operation of the tilt coils based on the coma aberration correction data stored in the road.

  The optical pickup device of the present invention is provided in the optical path of laser light guided from the laser diode to the objective lens, and is provided for detecting the temperature of the objective lens and a liquid crystal aberration correcting element for correcting spherical aberration. The spherical aberration correction data for correcting the spherical aberration due to the temperature change of the objective lens, the amount of displacement of the objective lens in the radial direction, and the coma aberration correction data for correcting the coma aberration due to the temperature change are stored. The aberration correction data memory circuit is provided, and the spherical aberration generated with the temperature change of the objective lens is controlled by the control operation for the liquid crystal aberration correction element based on the spherical aberration correction data stored in the aberration correction data memory circuit. In addition to correcting the coma aberration caused by the displacement of the objective lens in the radial direction, the aberration correction data It is configured to correct at the optical axis control operation of the objective lens by the drive control operation of the tilt control mechanism based on the coma aberration correction data stored in the Lee circuits.

  The present invention is characterized in that spherical aberration correction data corresponding to the thickness of the protective layer provided between the signal recording layer of the optical disc and the optical disc surface is stored in the aberration correction data memory circuit. It is.

  Further, the present invention is characterized in that coma aberration correction data corresponding to the thickness of the protective layer provided between the signal recording layer of the optical disc and the optical disc surface is stored in the aberration correction data memory circuit. It is.

  The optical pickup device of the present invention is provided in the optical path of laser light guided from the laser diode to the objective lens, and is provided for detecting the temperature of the objective lens, and a liquid crystal aberration correcting element for correcting spherical aberration. The temperature detection element, spherical aberration correction data for correcting spherical aberration due to temperature change of the objective lens, displacement amount in the radial direction of the objective lens and coma aberration correction data for correcting coma aberration due to temperature change are stored. An aberration correction data memory circuit is provided, and the spherical aberration caused by the temperature change of the objective lens is corrected by the control operation for the liquid crystal aberration correction element based on the spherical aberration correction data stored in the aberration correction data memory circuit. Together with the aberration correction data memory for coma that occurs with the displacement of the objective lens in the radial direction. Since the correction is performed by the optical axis control operation of the objective lens by the drive control operation of the tilt coil based on the coma aberration correction data stored in the path, the spherical aberration correction operation and the coma aberration correction operation can be accurately performed. I can do it.

It is the schematic which shows Example 1 of the optical pick-up apparatus based on this invention. It is the schematic which shows Example 2 of the optical pick-up apparatus which concerns on this invention. It is a figure for demonstrating the liquid-crystal aberration correction element which comprises the optical pick-up apparatus based on this invention. It is a figure for demonstrating the objective lens which comprises the optical pick-up apparatus which concerns on this invention.

  The coma aberration is corrected by changing and correcting the tilt of the optical axis of the objective lens by the tilt control operation for the coma aberration caused by the displacement of the objective lens in the radial direction of the optical disk.

  In FIG. 1, reference numeral 1 denotes a laser diode that emits a laser beam having a wavelength of, for example, 405 nm, and 2 denotes a diffraction grating on which the laser beam emitted from the laser diode 1 is incident. The diffraction grating section 2a that separates the + 1st order light and the −1st order light and the ½ wavelength plate 2b that converts incident laser light into linearly polarized light in the S direction, for example.

  Denoted at 3 is a deflecting beam splitter on which the laser light transmitted through the diffraction grating 2 is incident, and is provided with a control film 3a that transmits the S-polarized laser light and reflects the laser light polarized in the P direction. . Reference numeral 4 denotes a quarter-wave plate provided at a position where the laser light transmitted through the control film 3a of the polarizing beam splitter 3 is incident. The incident laser light is changed from linearly polarized light to circularly polarized light, On the other hand, it has the effect of converting circularly polarized light into linearly polarized light.

  Reference numeral 5 denotes a collimating lens on which the laser beam from the laser diode 1 that has passed through the quarter-wave plate 4 is incident, and functions to convert the incident laser beam into parallel light. Reference numeral 6 denotes a liquid crystal aberration correction element on which the laser beam converted into parallel light by the collimating lens 5 is incident. An annular transparent electrode pattern as shown in FIG. 3 is provided to correct spherical aberration. Yes.

  7 is provided at a position where the laser beam transmitted through the liquid crystal aberration correction element 6 is incident, and is a rising mirror that reflects the incident laser beam in the direction of the objective lens, and 8 is reflected from the rising mirror 7. The objective lens to which the laser beam incident is incident, and has a function of condensing the laser beam as a spot on the signal recording layer provided on the optical disc D.

  In such a configuration, the laser light emitted from the laser diode 1 is transmitted through the diffraction grating 2, the polarization beam splitter 3, the quarter wavelength plate 4, the collimator lens 5, the liquid crystal aberration correction element 6, and the rising mirror 7. After being incident on the lens 8, the signal recording layer of the optical disc D is irradiated as a spot by the focusing operation of the objective lens 8, and the laser beam irradiated on the signal recording layer is reflected as return light. Become.

  The return light reflected from the signal recording layer of the optical disc D passes through the objective lens 8, the rising mirror 7, the liquid crystal aberration correction element 6, the collimator lens 5, and the quarter wavelength plate 4, and the control film 3 a of the polarization beam splitter 3. Is incident on. The return light incident on the control film 3a of the polarizing beam splitter 3 in this way is polarized into linearly polarized light in the P direction by the phase changing operation by the quarter wavelength plate, and thus passes through the control film 3a. However, it is reflected as control laser light.

  Reference numeral 9 denotes a sensor lens on which the control laser light reflected by the control film 3a of the polarizing beam splitter 3 is incident. The control laser light is collected in a light receiving portion provided in a photodetector 10 called a PDIC. The light is irradiated and irradiated. The photodetector 10 is provided with a known quadrant sensor or the like, and a signal generating operation and astigmatism accompanying a reading operation of a signal recorded on the signal recording layer of the optical disc D by the main beam irradiation operation. The signal generating operation for performing the focusing control operation by the method and the signal generating operation for performing the tracking control operation by the irradiation operation of the two sub beams are configured. Since such control operations for generating various signals are well known, the description thereof is omitted.

  As described above, the optical pickup device according to the present invention is configured. In this configuration, the objective lens 8 is attached to the signal surface of the optical disc D by, for example, four support wires on the base of the optical pickup device. Thus, it is fixed to a member called a lens holder that is supported so as to be capable of displacement in the vertical direction and in the radial direction of the optical disc D.

  Reference numeral 11 denotes a focus coil provided in a lens holder to which the objective lens 8 is fixed, and the objective lens 8 is perpendicular to the signal surface of the optical disc D in cooperation with a magnet fixed to the base. It has an action to be displaced. A tracking coil 12 is provided in a lens holder to which the objective lens 8 is fixed, and has an action of displacing the objective lens 8 in the radial direction of the optical disk D in cooperation with a magnet fixed to the base. Have.

  Further, the optical pickup device according to the present invention incorporates a tilt adjusting mechanism capable of adjusting the angle of the optical axis of the objective lens 8 with respect to the signal surface of the optical disc D, and 13 is a tilt coil for adjusting the tilt. It is.

In the optical pickup device having such a configuration, the drive signal supply operation to the focus coil 11 and the tracking coil 12 is performed via the four support wires described above, and the drive signal supply operation to the tilt coil 13 is performed separately. It is configured to be performed through a provided lead wire. In addition, some optical pickup devices are configured to support the lens holder with six support wires. In such a case, tilting is performed using two of the support wires. The driving signal is supplied to the coil.

  The configuration of the optical pickup device in which the focus coil 11, the tracking coil 12, and the tilt coil 13 described above are incorporated and the focusing control operation, tracking control operation, and tilt control operation by the driving operation of each coil are well known, and the description thereof is omitted. .

  Reference numeral 14 denotes an RF signal generation circuit for generating an RF signal which is a signal obtained in response to a reading operation of a signal recorded on the signal recording layer of the optical disc D from a sensor which receives the main beam constituting the photodetector 10. , 15 is a focus error signal generation circuit that generates a focus error signal, which is a signal obtained in accordance with a laser beam focusing operation from a sensor that receives a main beam, and 16 is a laser beam tracking operation from a sensor that receives a sub beam. The tracking error signal generation circuit generates a tracking error signal that is a signal obtained in response.

  A pickup control circuit 17 performs various control operations of the optical pickup device based on signals obtained from the RF signal generation circuit 14, the focus error signal generation circuit 15, the tracking error signal generation circuit 16, and the like. Reference numeral 18 denotes a focus coil drive circuit to which a focus control signal output from the pickup control circuit 17 is input based on a focus error signal generated and input from the focus error signal generation circuit 15. It is configured to supply a drive signal. Reference numeral 19 denotes a tracking coil drive circuit to which a tracking control signal output from the pickup control circuit 17 is input based on a tracking error signal generated and input from the tracking error signal generation circuit 16. It is configured to supply a drive signal.

  Reference numeral 20 denotes a disc tilt detection circuit that detects the tilt of the optical disc D relative to the reference surface when the optical disc D is placed on a turntable (not shown). As the detection operation by the disc tilt detection circuit 20, for example, the optical pickup device is moved from the inner peripheral side to the outer peripheral side of the optical disc D, and supplied to the focus coil 11 that changes in accordance with the focus control operation performed during that time. Changes in DC voltage can be used. That is, when the optical disc D is inclined, the distance between the objective lens 8 and the signal recording layer of the optical disc D changes as the optical pickup device moves from the inner circumference side to the outer circumference side, and the change The degree of inclination of the optical disc D can be recognized by measuring the degree of change of the DC drive signal for displacing the objective lens 8 in the direction perpendicular to the signal surface direction of the optical disc D to correct the above.

  In addition, a light-emitting diode for tilt detection is provided to irradiate the signal surface of the optical disc D, and a change in the reflection angle of the light emitted from the light-emitting diode to the signal surface of the optical disc D is utilized. It is also possible to detect the inclination. Since such a technique is well known, the description thereof is omitted.

  A liquid crystal drive control circuit 21 controls a spherical aberration correction operation by the liquid crystal aberration correction element 6 based on a control signal output from the pickup control circuit 17. The spherical aberration correction operation by the liquid crystal aberration correction element 6 is performed by a drive signal supply control operation for an annular transparent electrode pattern provided in the liquid crystal aberration correction element 6 as is well known. The control operation for the liquid crystal aberration correction element 6 for correcting the spherical aberration is, for example, a reproduction operation of a signal recorded on the signal recording layer of the optical disc D, and jitter included in the reproduction signal. The value is measured and the jitter value is minimized.

Reference numeral 22 denotes an objective lens displacement amount for detecting the displacement amount of the objective lens 8 from the drive signal supplied from the tracking coil drive circuit 19 to the tracking coil 12, that is, the displacement amount of the objective lens 8 relative to the base constituting the optical pickup device. This is a detection circuit. The signal track provided in the signal recording layer of the optical disc D is formed in a spiral shape, and it is necessary to displace the objective lens 8 in the radial direction of the optical disc D in order to make the laser spot follow the signal track. .

  The operation of displacing the objective lens 8 in the outer circumferential direction, which is the radial direction of the optical disk D, is performed by gradually increasing the DC voltage of the drive signal supplied from the tracking coil drive circuit 19 to the tracking coil 12. Therefore, the amount of displacement of the objective lens 8 relative to the base can be recognized by detecting the magnitude of the DC voltage.

  Reference numeral 23 denotes a tilt coil drive circuit that supplies a drive signal to the tilt coil 13 based on a tilt control signal output from the pickup control circuit 17, and reference numeral 24 denotes a temperature detection element provided in the vicinity of the objective lens 8. It is comprised with the element from which the value of electrical resistance changes with temperature, such as. A temperature detection circuit 25 detects a temperature based on a signal obtained from the temperature detection element 24, and the detected temperature data is output to the pickup control circuit 17.

  An aberration correction data memory circuit 26 stores aberration correction data for controlling the drive signals supplied to the liquid crystal drive control circuit 21 and the tilt drive circuit 23 based on the temperature data obtained from the temperature detection circuit 25. is there. The aberration correction data stored in the aberration correction data memory circuit 26 is the amount of aberration and its aberration generated in response to the temperature change of the objective lens 8 and the radial displacement of the optical disc D during the manufacture of the optical pickup device. Is determined by measuring and adjusting the relationship between the liquid crystal aberration correction element 6 and the control signal supplied to the tilt coil drive circuit 23.

  The coma generated when the signal recorded on the optical disc D is read is proportional to the amount of displacement of the objective lens 8 in the radial direction, and the optical axis of the objective lens 8 with respect to the signal surface of the optical disc D. It is known that coma aberration can be corrected by adjusting the angle of. The present invention has been made paying attention to such a point, and the aberration correction data memory circuit 26 has a tilt correction suitable for correcting coma generated due to the displacement of the objective lens 8. Data for performing the operation is stored.

  In such a configuration, the tilt control signal generated based on the signal obtained from the disk tilt detection circuit 20 and the data stored in the aberration correction data memory circuit 26, that is, the amount of displacement of the objective lens 8 in the radial direction. A tilt correction signal generated based on the corresponding aberration correction data and the aberration correction data corresponding to the temperature of the objective lens 8 is output from the pickup control circuit 17 to the tilt coil drive circuit 23. .

  Although the first embodiment of the present invention is configured as described above, the operation will be described next. Laser light emitted from the laser diode 1 is separated into three beams of zero-order light, + 1st-order light, and −1st-order light by the diffraction grating 2, converted into S-polarized light, and incident on the polarization beam splitter 3. .

  The laser light incident on the polarizing beam splitter 3 passes through the control film 3a provided on the polarizing beam splitter 3, and then enters the quarter wavelength plate 4 to be converted into circularly polarized light. The laser light converted into circularly polarized light by the quarter wavelength plate 4 is converted into parallel light by the collimator lens 5 and then incident on the objective lens 8 through the liquid crystal aberration correction element 6 and the rising mirror 7. .

  The laser light incident on the objective lens 8 is focused on the signal recording layer provided on the optical disc D by the focusing operation of the objective lens 8 to generate a desired spot. Further, the laser light irradiated to the signal recording layer by the focusing operation of the objective lens 8 is reflected as return light by the signal recording layer.

  The return light reflected by the signal recording layer is incident on the polarizing beam splitter 3 through the objective lens 8, the rising mirror 7, the liquid crystal aberration correction element 6, the collimator lens 5, and the quarter wavelength plate 4. Since the polarization direction of the return light incident on the polarization beam splitter 3 is converted into linearly polarized light in the P direction by the quarter wavelength plate 4, the return light is provided in the polarization beam splitter 3. The light is reflected as control laser light by the control film 3 a and is incident on the sensor lens 9.

  The laser light incident on the sensor lens 9 is added with astigmatism by the sensor lens 9 and is irradiated to a light receiving portion provided in the photodetector 10. When such a laser beam is applied to the photodetector 10, various signals are generated based on signals obtained from the sensors incorporated in the photodetector 10. That is, an RF signal, which is a signal obtained in response to a reading operation of a signal recorded on the optical disc D from a sensor that receives the main beam, is generated by the RF signal generation circuit 14 and the focus error signal generation circuit 15 and A focus error signal and a tracking error signal are generated from the tracking error signal generation circuit 16 and input to the pickup control circuit 17.

  When the various signals described above are input to the pickup control circuit 17, a focus control signal and a tracking control signal are output from the pickup control circuit 17 to the focus coil drive circuit 18 and the tracking coil drive circuit 19, respectively. As a result, a drive signal is supplied from the focus coil drive circuit 18 to the focus coil 11 and a drive signal is supplied from the tracking coil drive circuit 19 to the tracking coil 12.

  When such a drive signal is supplied, the displacement operation of the objective lens 8 in the direction perpendicular to the signal surface of the optical disk D by the focus coil 11 and the displacement operation of the objective lens 8 in the radial direction of the optical disk D by the tracking coil 12 are performed. Is done.

  Accordingly, the focus control operation and the tracking control operation of the optical pickup device are performed, and the reproduction operation of the signal recorded on the signal recording layer of the optical disc D can be performed. Such a reproduction signal is obtained as information data by demodulating the RF signal generated from the RF signal generation circuit 14.

  As described above, the read operation of the signal recorded on the signal recording layer of the optical disc D is performed, and when such a read operation is performed, the liquid crystal is applied to the transparent electrode pattern provided in the liquid crystal aberration correction element 6. A control signal is supplied from the drive control circuit 21 to perform an operation for correcting spherical aberration. The control operation for correcting the spherical aberration with respect to the liquid crystal aberration correction element 6 is performed so that the spherical aberration is minimized, and the control operation with respect to the liquid crystal aberration correction element 6 is performed with a jitter value included in the reproduction signal. Detection is performed so that the jitter value is minimized. In this embodiment, the control operation for spherical aberration correction for the liquid crystal aberration correction element 6 is performed using the jitter value. However, not only the method of minimizing the jitter value but also, for example, the RF signal It is also possible to configure so that the level is controlled to the maximum.

By performing the control operation on the liquid crystal aberration correcting element 6 described above, the spherical aberration that appears in the spot of the laser light incident on the objective lens 8 and irradiated on the signal recording layer of the optical disc D can be minimized. Is displaced in the radial direction of the optical disc D, so that coma aberration occurs. When the objective lens 8 is displaced in the radial direction, the value of the DC voltage included in the drive signal supplied from the tracking coil drive circuit 19 to the tracking coil 12 changes, so that the objective lens displacement detection circuit 22 determines the DC voltage value. By detecting this, an operation of detecting the amount of displacement of the objective lens 8 is performed.

  When the detection operation by the objective lens displacement detection circuit 22 is performed, the detection output is input to the pickup control circuit 17. When such a detection signal is input to the pickup control circuit 17, data stored in the aberration correction data memory circuit 26 corresponding to the amount of displacement of the objective lens 8 is read out and generated based on the data. A tilt correction signal is output from the pickup control circuit 17 to the tilt coil drive circuit 23. The magnitude of such a tilt correction signal is set to a value that changes the angle of the optical axis of the objective lens 8 in order to correct coma aberration that occurs in accordance with the amount of displacement of the objective lens 8 in the radial direction. Yes.

  A tilt correction signal is output from the pickup control circuit 17 to the tilt coil drive circuit 23 based on the data read from the aberration correction data memory circuit 26, and the tilt correction signal is output by the disk tilt detection circuit 20. In order to perform tilt adjustment corresponding to the disc tilt detected in advance, the tilt control signal supplied to the tilt coil drive circuit 23 is added to the tilt control signal.

  As described above, the tilt control signal output corresponding to the tilt of the disk is output to the tilt coil driving circuit 23 and the coma aberration generated due to the displacement of the objective lens 8 in the radial direction of the optical disk D is output. Since the tilt correction signal is supplied, the tilt control signal and the tilt correction signal are supplied from the tilt coil drive circuit 23 to the tilt coil 13.

  When such a tilt control signal and a tilt correction signal are supplied to the tilt coil 13, an operation for changing the angle of the optical axis of the objective lens 8 with respect to the signal surface of the optical disk D, that is, a tilt adjustment operation is performed. As a result, in addition to the tilt adjustment operation with respect to the tilt of the optical disc D, it is possible to suppress coma aberration that occurs due to the radial displacement of the objective lens 8.

  As described above, coma aberration generated according to the radial displacement of the objective lens 8 by changing the angle of the optical axis of the objective lens 8 based on the data stored in the aberration correction data memory circuit 26. Although corrected, the aberration correction data memory circuit 26 stores the data for controlling the liquid crystal aberration correction element 6 to correct the spherical aberration caused by the temperature change of the objective lens 8 and the spherical aberration caused by the temperature change. Data for correcting coma aberration generated in accordance with the displacement operation of the objective lens 8 in the radial direction in a state where the liquid crystal aberration correction element 6 is controlled to correct the above is stored.

  The various data stored in the aberration correction data memory circuit 26 described above correspond to changes in the amount of spherical aberration accompanying the temperature change of the objective lens 8 and the amount of displacement in the radial direction of the objective lens 8 when the optical pickup device is manufactured. It can be determined by measuring and adjusting the relationship between the amount of aberration generated and the control signal supplied to the liquid crystal aberration correction element 6 and the tilt coil drive circuit 23 in order to correct the aberration.

In the first embodiment described above, the optical pickup device including the tilt coil 13 that adjusts the angle of the optical axis of the objective lens 8 with respect to the signal surface of the optical disc D has been described. Next, the light that does not include the tilt coil 13 is described. The second embodiment shown in FIG. 2 will be described for the case where the pickup apparatus is implemented.

  In the figure, the same components as those in the embodiment shown in FIG. The optical pickup device shown in Embodiment 2 adjusts the angle of the optical axis with respect to the signal surface of the optical disc D of the objective lens 8 by controlling the drive signals supplied to the plurality of focus coils as described in Patent Document 2. A tilt control mechanism capable of performing an operation, that is, a tilt adjustment operation is incorporated.

  In the optical pickup device used in the embodiment shown in FIG. 2, for example, a first lens holder in which the objective lens 8 is fixed in order to perform a focus control operation is displaced in the direction perpendicular to the signal surface of the optical disc D. Two focus coils, a focus coil 11A and a second focus coil 11B, are incorporated.

  The focus control operation in the optical pickup device having such a configuration is as follows. The same drive signal is supplied to the first focus coil 11A and the second focus coil 11B, thereby moving the objective lens 8 in a direction perpendicular to the signal surface of the optical disc D. And by changing the angle of the optical axis without changing it.

  On the other hand, the operation of changing and adjusting the angle of the optical axis of the objective lens 8 with respect to the signal surface of the optical disc D, that is, the tilt control operation, supplies drive signals of different levels to the first focus coil 11A and the second focus coil 11B. Can be done. That is, when different levels of drive signals are supplied to the two focus coils, the displacement amount of each position of the lens holder differs depending on the level difference between the drive signals, and the lens holder tilts according to the difference.

  The angle of the optical axis with respect to the signal surface of the optical disk D of the objective lens 8 can be changed by changing the tilt of the lens holder accompanying such a difference in displacement. Therefore, even in an optical pickup device incorporating such a tilt control mechanism, the tilt control mechanism uses coma aberration generated by the spherical aberration correction operation by the liquid crystal aberration correction element 6 and the radial displacement of the objective lens 8. Thus, the correction can be performed in the same manner as in the first embodiment.

  The present invention is not limited to Blu-ray standard optical discs but also DVDs and other optical discs, as well as optical discs with higher density and optical signals that are recorded on optical discs having a plurality of signal recording layers. It can be used in a pickup device.

DESCRIPTION OF SYMBOLS 1 Laser diode 3 Polarizing beam splitter 5 Collimating lens 6 Liquid crystal aberration correction element 8 Objective lens 10 Photodetector 11 Focus coil 12 Tracking coil 13 Tilt coil 14 RF signal generation circuit 15 Focus error signal generation circuit 16 Tracking error signal generation circuit 17 Pickup Control circuit 20 Disk tilt detection circuit 21 Liquid crystal drive control circuit 22 Objective lens displacement detection circuit 23 Tilt coil drive circuit 25 Temperature detection circuit 26 Aberration correction data memory circuit D Optical disk

Claims (7)

An objective lens for focusing laser light emitted from a laser diode on a signal recording layer provided on the optical disc, a focus coil for displacing the objective lens in the surface direction of the optical disc, and the objective lens in the radial direction of the optical disc The optical pickup device includes a tracking coil that is displaced toward the optical disk and a tilt coil that corrects the tilt of the optical axis of the objective lens with respect to the optical disk surface, and is provided in the optical path of the laser light guided from the laser diode to the objective lens. Liquid crystal aberration correction element that corrects spherical aberration, a temperature detection element that is provided to detect the temperature of the objective lens, spherical aberration correction data that corrects spherical aberration due to temperature change of the objective lens, Comatic aberration due to radial displacement and temperature change An aberration correction data memory circuit in which coma aberration correction data to be corrected is stored is provided, and spherical aberration that occurs due to a temperature change of the objective lens is based on the spherical aberration correction data stored in the aberration correction data memory circuit. The coma aberration generated by the displacement operation in the radial direction of the objective lens is corrected by the control operation for the liquid crystal aberration correction element, and the tilt coil of the tilt coil based on the coma aberration correction data stored in the aberration correction data memory circuit is used. An optical pickup apparatus, wherein correction is performed by an optical axis control operation of an objective lens by a drive control operation. An objective lens for focusing laser light emitted from a laser diode on a signal recording layer provided on the optical disc, a focus coil for displacing the objective lens in the surface direction of the optical disc, and the objective lens in the radial direction of the optical disc An optical pickup device including a tracking coil that is displaced toward the optical disk surface and a tilt control mechanism that corrects an inclination of the optical axis of the objective lens with respect to the optical disk surface by a control operation of a drive signal to the focus coil. A liquid crystal aberration correction element that is provided in the optical path of the laser light guided to the lens and corrects spherical aberration, a temperature detection element that is provided to detect the temperature of the objective lens, and a temperature change of the objective lens Spherical aberration correction data to correct spherical aberration, objective lens An aberration correction data memory circuit for storing coma aberration correction data for correcting coma aberration associated with a change in the radial direction of the lens and a change in temperature is provided. The aberration correction data memory corrects the liquid crystal aberration correction element based on the spherical aberration correction data stored in the correction data memory circuit and corrects the coma aberration generated by the displacement of the objective lens in the radial direction. An optical pickup device, wherein correction is performed by an optical axis control operation of an objective lens by a drive control operation of the tilt control mechanism based on coma aberration correction data stored in a circuit. The spherical aberration correction data corresponding to the thickness of the protective layer provided between the signal recording layer of the optical disc and the optical disc surface is stored in the aberration correction data memory circuit. The optical pickup device described in 1. The coma aberration correction data corresponding to the thickness of the protective layer provided between the signal recording layer of the optical disc and the optical disc surface is stored in the aberration correction data memory circuit. The optical pickup device described in 1. 2. The optical pickup device according to claim 1, wherein a drive signal supplied to the tilt coil is generated according to a displacement amount of the objective lens. 3. The optical pickup device according to claim 2, wherein the drive control operation of the tilt control mechanism is performed according to the amount of displacement of the objective lens. 7. The optical pickup device according to claim 5, wherein a displacement amount of the objective lens is detected from a drive signal supplied to the tracking coil.

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