JP2004265592A - Optical disk drive and objective lens driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of a recording/reproducing signal caused by AC tilting which cannot be corrected by a liquid crystal device due to the variation of the posture of a movable body, or the deterioration of control performance caused by unnecessary resonance which is caused when an objective lens is driven in a focusing direction or a tracking direction. <P>SOLUTION: The driving signal of a liquid crystal is superimposed on a focusing driving signal and a tracking driving signal and supplied to a movable body, separated by a frequency band on the movable body, and applied to the liquid crystal device. Thus the supply of driving signals to the movable body is performed through four wires. Consequently, an aberration correction function having no deterioration of aberration correcting capability caused by the movement of an objective lens in a tracking direction T is realized by mounting the liquid crystal device on the movable body, and signal is supplied through the four wires as in the conventional case. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an objective lens driving device, and in particular, to an objective lens driving device of a device for optically recording or reproducing information on a disc-shaped recording medium, wherein a liquid crystal element is mounted on a movable body of the objective lens driving device. The present invention relates to a device capable of correcting aberrations generated in the above-described optical information recording or reproducing apparatus.

  The objective lens driving device is incorporated in a device (hereinafter, referred to as an optical disk device) that optically records or reproduces information on a disc-shaped recording medium (hereinafter, referred to as a disk) such as a CD (compact disk), and records or reproduces information. The objective lens is mounted on an optical pickup equipped with an optical system for correcting the focusing error due to the vertical movement of the warpage of the disk and the tracking error due to the eccentricity. The disc is driven in two axes: a vertical direction (hereinafter, referred to as a focusing direction) and a predetermined radial direction of the disk (hereinafter, referred to as a tracking direction).

  In the optical disk device including the above-described objective lens driving device, if the optical axis of the objective lens is tilted relative to the disk surface (hereinafter, referred to as tilt), coma aberration occurs and the signal at the time of recording / reproduction deteriorates. It becomes a factor.

  In addition, variations in the thickness of the disc also cause spherical aberration, which is a factor in deteriorating signals during recording and reproduction.

  In particular, tolerances for tilt and variations in disk thickness during recording and reproduction on a high-density disk such as a DVD (digital versatile disk) are smaller than those of a CD, and aberrations caused by these factors are corrected. Function is required.

  Therefore, a system for correcting aberrations using a liquid crystal element has already been disclosed in Japanese Patent Application Laid-Open No. 10-20263.

  In the liquid crystal element for aberration correction, the control electrode is divided into a plurality of regions in a predetermined pattern, and the aberration is corrected by adjusting the phase difference of the transmitted laser light by adjusting the voltage applied to each region. I do.

  However, when the liquid crystal element as described above is arranged separately from the objective lens in the optical system of the optical pickup, when the objective lens moves in the tracking direction, the pattern of the control electrode of the liquid crystal and the optical axis of the objective lens are aligned. There is a problem that the aberration correction capability is reduced due to the positional deviation, that is, the generated aberration distribution and the deviation of the control electrode pattern, and the recording / reproducing signal is deteriorated.

  In order to solve this problem, by mounting the liquid crystal element on the movable body of the objective lens driving device and driving it integrally with the objective lens, the aberration correction ability is reduced even when the objective lens moves in the tracking direction. Therefore, the recording / reproducing signal does not deteriorate.

  However, the power supply lines required in the liquid crystal element for aberration correction include at least three power supply lines for applying the maximum voltage and the minimum voltage among the voltages applied to the respective regions of the control electrode and the voltage applied to the common electrode. is necessary.

  On the other hand, in such an objective lens driving device, four metal wires are used as a support mechanism for supporting a lens holder holding an objective lens so as to be elastically movable in at least two directions of a focusing direction and a tracking direction. The four metal wires are also used as power supply lines to the focusing coil and the tracking coil mounted on the lens holder.

  Therefore, as a power supply line for the liquid crystal element, a lead wire, an FPC, or the like is newly provided to supply a drive signal, or a drive signal is supplied using this metal wire by increasing the number of metal wires as a support mechanism. There is a need.

  When a drive signal is supplied by a lead wire, it is necessary to use a thin wire so that a negative force is not applied to the movable body. However, the workability during assembly is poor, which increases the man-hour and increases the cost. There is a problem of deteriorating reliability such as later disconnection.

  In addition, when a drive signal is supplied using an FPC, the reliability is improved as compared with a lead wire, but the reliability when repeatedly bent and stretched is used is lower than that of a metal wire. The movable body is subjected to a negative force in an arbitrary direction and magnitude depending on the movement and the ambient temperature. As a result, the recording / reproducing signal is degraded due to the occurrence of an AC tilt that cannot be corrected by the liquid crystal element due to the variation of the posture of the movable body, or unnecessary resonance when the objective lens is driven in the focusing direction and the tracking direction. There is a problem that the control performance is deteriorated due to the occurrence.

  Therefore, sufficient reliability can be ensured by increasing the number of metal wires as a support mechanism and supplying a drive signal.

  However, the four metal wires used for supplying the driving signals for the focusing drive and the tracking drive are added to the three wires used for supplying the drive signal for the liquid crystal element, so that a total of seven wires are used. In order to make the number of wires even, the support mechanism is constituted by at least eight metal wires.

  As a result of increasing the number of metal wires from four to eight, the material cost due to an increase in the number of parts, the operating cost due to an increase in the number of assembly steps, and the probability of occurrence of defective products increase, resulting in an increase in product cost. there were.

  Further, with the increase in the number of metal wires, factors of individual component variation and assembly variation increase, and as a result, an AC tilt that cannot be corrected by the liquid crystal element due to a variation in the posture of the movable body occurs. Therefore, there is a problem that the recording / reproducing signal is deteriorated due to the above, or the control performance is deteriorated due to occurrence of unnecessary resonance when the objective lens is driven in the focusing direction and the tracking direction.

  In addition, it is necessary to use a thinner metal wire in order to prevent an increase in the spring constant of the support mechanism due to the increase in the number of metal wires, and to secure driving sensitivity in the low frequency range in the focusing and tracking directions. There has been a problem that it is difficult to secure a single performance such as straightness of a wire, and the variation factor is further increased, thereby causing the occurrence of AC tilt and the occurrence of unnecessary resonance.

  The present invention has been made to solve such a problem, and a liquid crystal element is mounted on a movable body, so that an aberration correction function without deterioration of aberration correction ability due to movement of an objective lens in a tracking direction can be realized. At the same time, the number of power supply lines to the liquid crystal element by the metal wire as the support mechanism is reduced, and sufficient reliability is secured, and at the same time, the factors of variation are reduced, and the deterioration of the recording / reproducing signal due to the occurrence of AC tilt is unnecessary. It is an object of the present invention to provide an objective lens driving device capable of preventing deterioration of control performance due to occurrence of resonance.

  An objective lens driving device according to the present invention is used by being incorporated in a device that optically records or reproduces information on a disc-shaped recording medium, and has an optical axis in a focusing direction that is a direction perpendicular to the disc-shaped recording medium. A lens, a movable body having a lens holder for holding the objective lens, a base, and the movable body elastically movable with respect to the base in at least the focusing direction or a tracking direction that is a radial direction of the disc-shaped recording medium. A rod-shaped elastic support member made of at least four conductive materials and fixed at a distal end to the movable body and a proximal end to the base, and a driving force mounted on the movable body in at least the focusing direction. And a tracking coil mounted on the movable body and generating a driving force in at least the tracking direction. And a control electrode divided into a plurality of regions in a predetermined shape and a common electrode facing the control electrode, and a liquid crystal element mounted on the movable body so as to be located on the optical axis of the objective lens. A magnetic field generating means disposed on the base for applying a magnetic field to the focusing coil and the tracking coil, and superimposing a drive signal of the liquid crystal element on a drive signal of the focusing coil or the tracking coil. The signal is supplied by using a rod-shaped elastic support member.

  As described above, according to the first, second, and third aspects of the present invention, the driving signal of the liquid crystal element is supplied to the movable body while being superimposed on the focusing drive signal and the tracking drive signal. By separating the drive signal according to the frequency band and applying the drive signal to the liquid crystal element, the drive signal can be supplied to the movable body with four wires.

  Therefore, by mounting the liquid crystal element on the movable body, it is possible to realize the aberration correction function without deterioration of the aberration correction ability due to the movement of the objective lens in the tracking direction T, and to perform the signal using four wires as in the related art. As a result, it is possible to realize a highly reliable support mechanism using a metal wire, and at the same time, reduce the variation factor to eliminate the deterioration of the recording / reproducing signal due to the occurrence of AC tilt and the deterioration of the control performance due to the occurrence of unnecessary resonance. it can. Furthermore, since the number of wires does not increase, material costs due to an increase in the number of parts, work costs due to an increase in the number of assembling steps, and a probability of occurrence of defective products do not increase.

  According to the fourth and fifth aspects of the present invention, a liquid crystal driving signal is generated using the intermediate potential at both ends of the tracking coil or the focusing coil as a reference potential and supplied to the control electrode of the liquid crystal element and the tracking coil. Alternatively, by supplying an intermediate potential at both ends of the focusing coil to the common electrode of the liquid crystal element on the movable body, a drive signal can be supplied to the movable body with six wires.

  Therefore, by mounting the liquid crystal element on the movable body, it is possible to realize the aberration correction function without deterioration of the aberration correction ability due to the movement of the objective lens in the tracking direction T, and to reduce the number of power supply lines to the liquid crystal element. As a result, signals can be supplied by a total of six wires, so that a highly reliable support mechanism using a metal wire is realized, and at the same time, a variation factor is reduced to cause deterioration of a recording / reproducing signal due to AC tilt and occurrence of unnecessary resonance. Control performance degradation due to the above.

  Further, since the number of wires is reduced, it is possible to minimize the material cost due to the increase in the number of parts, the operation cost due to the increase in the number of assembly steps, and the probability of occurrence of defective products. Further, since the above-mentioned effect can be realized by using only two resistors in addition to the liquid crystal element as a component mounted on the movable body, the focusing direction and tracking can be performed at low cost while suppressing an increase in the weight of the movable body. The above effect can be realized without deteriorating the driving efficiency in the direction.

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

(Embodiment 1)
FIG. 1 is a configuration diagram showing a configuration of a driving circuit of an objective lens driving device according to a first embodiment of the present invention, FIG. 2 is a perspective view of the objective lens driving device according to the first embodiment of the present invention, and FIG. FIG. 4 is an optical configuration diagram of an optical pickup including the objective lens driving device according to the first embodiment, FIG. 4 is a pattern diagram of a control electrode of a liquid crystal element, and FIG. 5 is a cross-sectional view illustrating a structure of the liquid crystal element.

  In these figures, F is a focusing direction, T is a tracking direction, S is a tangential direction perpendicular to the focusing direction F and the tracking direction T, R is a radial direction that is a rotation direction around the tangential direction S, and K is an optical axis direction. Is shown.

  First, the configuration of the mechanism of the objective lens driving device according to the first embodiment of the present invention will be described with reference to FIGS.

  2 and 3, reference numeral 14 denotes a disk, 1 denotes an objective lens, and 2 denotes a lens holder made of molded resin. Reference numeral 4 denotes a focusing coil wound around and fixed to the lens holder 2 around the axis in the focusing direction F, 5 denotes a tracking coil wound around the axis in the tracking direction T and fixed to the lens holder 2, and 7 denotes the objective lens 1. A liquid crystal element 8a, 8b for correcting coma is fixedly mounted on the lens holder 2 so as to be positioned on the optical axis K, and is disposed on the side surface of the lens holder so as to sandwich the objective lens 1 along the tracking direction T. Capacitors 15b and 15c are mounted on the terminal plate 8b. Therefore, the movable body 12 is constituted by the objective lens 1, the lens holder 2, the focusing coil 4, the tracking coil 5, the liquid crystal element 7, the terminal plates 8a and 8b, and the capacitors 15a to 15d.

  Reference numerals 3a to 3d denote wires which are rod-shaped elastic support members made of substantially parallel conductive materials having axes in the tangential direction S. One ends of the wires 3a to 3d are fixed to the terminal plates 8a and 8b of the movable body 12 by soldering. I have.

  Reference numeral 11 denotes a wire holder to which one end of each of the wires 3a to 3d is fixed, and the wire holder 11 is fixed to the base 10.

  Reference numeral 13 denotes a tilt sensor which is fixed to the wire holder 11 and detects the inclination of the disk 14 in the radial direction R.

  Reference numerals 6a and 6b denote permanent magnets arranged so as to sandwich the movable body 12 in the tangential direction S and fixed to the base 10 so that the same poles are opposed to each other. And a part of the tracking coil 5.

  Therefore, the objective lens 1 is driven in the focusing direction F and the tracking direction T as follows.

  First, in the driving in the focusing direction F, the movable body 12 is supported by the wires 3a to 3d by receiving an electromagnetic force obtained by a part of the focusing coil 4 being orthogonal to the magnetic flux generated by the permanent magnets 6a and 6b. The amount of current flowing through the focusing coil 4 is obtained by performing a substantially translational movement to F, and the amount of movement of the objective lens 1 is adjusted.

  In the driving in the tracking direction T, the movable body 12 is supported by the wires 3a to 3d by receiving an electromagnetic force obtained when a part of the tracking coil 5 is orthogonal to the magnetic flux generated by the permanent magnets 6a and 6b. The amount of current flowing through the tracking coil 5 is obtained by performing substantially translational motion, and the amount of movement of the objective lens 1 is adjusted.

  Next, an optical configuration of an optical pickup including the objective lens driving device according to the first embodiment of the present invention will be described with reference to FIG.

  The optical configuration of the optical pickup including the objective lens driving device according to the first embodiment of the present invention includes a semiconductor laser 19 as a light source, a polarizing beam splitter 20, a condenser lens 21, a liquid crystal element 7, a quarter wavelength plate 22, an objective It comprises a lens 1, a disk 14, a cylindrical lens 23, and a photodetector 24.

  The optical pickup operates as follows. The P-polarized light beam emitted from the semiconductor laser 19 passes through the polarization beam splitter 20, becomes a substantially parallel light beam by the condenser lens 21, and passes through the liquid crystal element 7 and the 波長 wavelength plate 22. When passing through the quarter-wave plate 22, the light beam is changed from P-polarized light to circularly-polarized light. The light transmitted through the wavelength plate 22 is focused on the information recording surface of the disk 14 by the objective lens 1.

  The light reflected from the information recording surface of the disk 14 enters the objective lens 1 again and passes through the quarter-wave plate 22. Light transmitted through the quarter-wave plate 22 is changed from circularly polarized light to S-polarized light. The light transmitted through the 波長 wavelength plate 22 passes through the liquid crystal element 7, is reflected by the polarization beam splitter 20, and is condensed on a photodetector 24 by a cylindrical lens 23. The photodetector 24 photoelectrically converts the received light beam to form a reproduction signal, forms a focusing drive signal by an astigmatism method, and forms a tracking drive signal by a phase difference method or a push-pull method. The signal of is output.

  Further, the liquid crystal element 7 for correcting coma will be described with reference to FIGS. 1, 4 and 5. FIG. The liquid crystal element 7 has control electrodes 7a to 7e, a liquid crystal section 7g, and a common electrode 7f arranged in this order between substrates 7m and 7n made of glass. As shown in FIG. 4, the control electrodes 7a to 7e are divided into regions in accordance with the aberration distribution when a tilt in the radial direction occurs and are deposited on the inner surface of the base material 7m. It is uniformly deposited on top. Here, the control electrodes 7a to 7e and the common electrode 7f are transparent electrodes that apply an external signal to the liquid crystal unit 7g and transmit light.

  Further, as shown in FIG. 1, voltage dividing resistors 7h to 7k in which resistors are arranged in series between the control electrode 7a and the control electrode 7e constitute a contact between the voltage dividing resistor 7h and the voltage dividing resistor 7i and the control electrode. 7b, a contact between the voltage dividing resistor 7i and the voltage dividing resistor 7j is connected to the control electrode 7c, and a contact between the voltage dividing resistor 7j and the voltage dividing resistor 7k is connected to the control electrode 7d. Therefore, the difference between the potential of the control electrode 7a and the potential of the control electrode 7e is divided by the voltage dividing resistors 7h to 7k, and the divided potentials are applied to the control electrodes 7b, 7c, 7d. As a result, stepwise potentials are applied to the control electrodes 7a to 7e, respectively. The voltage dividing resistors 7h to 7k are formed of transparent thin film resistors that transmit light, and are deposited on the inner surfaces of the substrates 7m and 7n.

  The liquid crystal unit 7g can change the phase of the incident light beam according to the potential difference between the voltages of the control electrodes 7a to 7e with respect to the voltage of the common electrode 7f, and can adjust the amount of phase that changes according to the magnitude of the potential difference. As a result, the coma caused by the relative tilt between the disk 14 and the objective lens 1 can be corrected by applying a stepwise potential to each area of the control electrodes 7a to 7e as described above.

  Next, the configuration of the driving circuit of the objective lens driving device according to the first embodiment of the present invention will be described with reference to FIG. The drive system of the objective lens driving device according to the first embodiment of the present invention includes a tilt sensor 13, a liquid crystal control circuit 18, a focusing control circuit 16, a tracking control circuit 17, wires 3a to 3d, a focusing coil 4, a tracking coil 5, a capacitor. 15a to 15d and the liquid crystal element 7.

  The driving system of the objective lens driving device operates as follows. First, the tilt sensor 13 detects the amount of tilt, and the liquid crystal control circuit 18 generates a liquid crystal drive signal. On the other hand, a focusing error amount is detected by an astigmatism method, a focusing drive signal is detected by a focusing control circuit 16, a tracking error amount is detected by a phase difference method or a push-pull method, and a tracking drive signal is generated by a tracking control circuit 17. Here, the frequency band of the focusing drive signal and the tracking drive signal is a band of DC to 40 kHz, but the frequency band of the liquid crystal drive signal is 40 kHz or more.

  Therefore, when the highest potential is applied to the control electrode 7a and the lowest potential is applied to the control electrode 7d of the liquid crystal element 7, the signal having the highest potential among the liquid crystal drive signals output from the liquid crystal control circuit 18 is output from the focusing control circuit 16. It is supplied to the movable body 12 of the objective lens driving device through the wires 3a and 3b in a manner superimposed on the focusing drive signal to be performed. The superimposed signal is supplied to the focusing coil 4, and the objective lens 1 is driven in the focusing direction F based on the signal. The natural frequency of the movable body 12 is 40 kHz or less, and the objective lens 1 has a frequency of 40 kHz or more. Does not respond to signals. Further, the superimposed signal is also supplied to the liquid crystal element 7 via the capacitors 15a and 15b. The signal of 40 kHz or less is cut by the capacitors 15a and 15b and separated into only the liquid crystal drive signal generated by the liquid crystal control circuit 18. Then, it is applied to the common electrode 7f and the control electrode 7a of the liquid crystal element 7.

  Similarly, the signal having the lowest potential among the liquid crystal drive signals output from the liquid crystal control circuit 18 is superimposed on the tracking drive signal output from the tracking control circuit 17 and is moved through the wires 3c and 3d. To supply. The superimposed signal is supplied to the tracking coil 5, and the superimposed signal is also supplied to the liquid crystal element 7 via the capacitors 15c and 15d. Only the liquid crystal drive signal generated at 18 is applied to the common electrode 7f and the control electrode 7e of the liquid crystal element 7.

  Similarly, when the lowest potential is applied to the control electrode 7a and the highest potential is applied to the control electrode 7d of the liquid crystal element 7, the liquid crystal drive signal can be moved by the wires 3a to 3d by superimposing the liquid crystal drive signal on the focusing drive signal and the tracking drive signal. The liquid crystal element 7 is supplied to the liquid crystal element 7 by separating the signals into the common electrode 7f, the control electrode 7a, and the control electrode 7e.

  As described above, the drive signal of the liquid crystal element 7 is superimposed on the focusing drive signal and the tracking drive signal and supplied to the movable body 12, and the liquid crystal drive signal is separated on the movable body 12 by a frequency band and applied to the liquid crystal element. The supply of the drive signal to the movable body 12 can be performed by the four wires 3a to 3d. Therefore, by mounting the liquid crystal element 7 on the movable body 12, it is possible to realize an aberration correction function without deteriorating the aberration correction ability due to the movement of the objective lens 1 in the tracking direction T. Since a signal can be supplied by the wire 3, a highly reliable support mechanism using a metal wire is realized, and at the same time, a variation factor is reduced to deteriorate a recording / reproducing signal due to an AC tilt and a control performance due to an unnecessary resonance. Can be eliminated. Furthermore, since the number of wires does not increase, material costs due to an increase in the number of parts, work costs due to an increase in the number of assembling steps, and a probability of occurrence of defective products do not increase.

  In the above description, it is assumed that the liquid crystal element 7 has a control electrode pattern for coma aberration correction by tilting in the radial direction R. Similar effects can be obtained even with an electrode pattern. For example, the same effect can be obtained even with a pattern for correcting coma aberration by tilting in the tangential direction, a pattern for simultaneous correction of radial and tangential two axes, and a pattern for correcting spherical aberration.

  In the above description, the tilt sensor detects the amount of tilt error and generates the liquid crystal drive signal. However, it is sufficient that a signal that changes in accordance with the amount of tilt error can be detected. A liquid crystal drive signal may be generated so that the jitter value is detected and the value is minimized, or a liquid crystal drive signal is generated such that the amplitude of the reproduction signal of the disc is detected and the value is maximized. Is also good.

(Embodiment 2)
FIG. 6 is a configuration diagram showing a configuration of a drive circuit of the objective lens driving device according to the second embodiment of the present invention, and FIG. 7 is a perspective view of the objective lens driving device according to the second embodiment of the present invention.

  In these drawings, the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding reference numerals, and the optical configuration of the optical pickup including the objective lens driving device according to the second embodiment of the present invention, the structure of the liquid crystal element, and the like. The pattern of the control electrode is the same as in FIGS. 3, 4 and 5.

  The difference between the second embodiment and the first embodiment will be described below. 6 and 7, resistors 25a and 25b are mounted on the terminal plates 8a and 8b instead of the capacitors 15a to 15d. Therefore, the movable body 12 includes the objective lens 1, the lens holder 2, the focusing coil 4, and the tracking coil 5. , Liquid crystal element 7, terminal plates 8a and 8b, and resistors 25a to 25d.

  The movable body is supported so as to be movable in a focusing direction F or a tracking direction T by six wires 3a to 3f.

  The driving system of the objective lens driving device according to the second embodiment of the present invention includes a tilt sensor 13, a liquid crystal control circuit 18, a focusing control circuit 16, a tracking control circuit 17, wires 3a to 3f, focusing coils 4, tracking coils 5, resistors 25a to 25d and the liquid crystal element 7. Here, the resistors 25a and 25c and the resistors 25b and 25d are resistors having substantially the same resistance value.

  The driving system of the objective lens driving device operates as follows. First, a focusing error amount is detected by an astigmatism method, a focusing drive signal is detected by a focusing control circuit 16, a tracking error amount is detected by a phase difference method or a push-pull method, and a tracking drive signal is generated by a tracking control circuit 17.

  The focusing drive signal is supplied to the movable body 12 through the wires 3a and 3b, applied to the focusing coil 4, and the objective lens 1 is driven in the focusing direction F based on the focusing drive signal.

  The tracking drive signal is supplied to the movable body 12 via the wires 3c and 3d, applied to the tracking coil 5, and the objective lens 1 is driven in the tracking direction T based on the tracking drive signal.

  On the other hand, both ends of the tracking drive signal generated by the tracking control circuit 17 are connected by resistors 25c and 25d arranged in series, and an intermediate potential between the resistors 25c and 25d is input to the liquid crystal control circuit 18. Further, the tilt sensor 13 detects the amount of tilt, and the liquid crystal control circuit 18 generates a liquid crystal drive signal using the intermediate potential between the resistors 25c and 25d as a reference potential.

  Therefore, when the highest potential is applied to the control electrode 7a and the lowest potential is applied to the control electrode 7d of the liquid crystal element 7, the signal having the highest potential among the liquid crystal drive signals output from the liquid crystal control circuit 18 passes through the wire 3e via the lowest potential. Is supplied to the movable body 12 of the objective lens driving device through the wire 3f, and is applied to the control electrodes 7a and 7e of the liquid crystal element, respectively. Further, both ends of the tracking coil 5 are connected by resistors 25a and 25b arranged in series, and an intermediate potential between the resistors 25a and 25b is input to a common electrode 7f of the liquid crystal element 7. Therefore, the liquid crystal element is driven based on the liquid crystal drive signal using the intermediate potential at both ends of the tracking coil 5 as the reference potential.

  Similarly, when the lowest potential is applied to the control electrode 7a and the highest potential is applied to the control electrode 7d of the liquid crystal element 7, the signal having the highest potential among the liquid crystal driving signals output from the liquid crystal control circuit 18 is transmitted through the wire 3f. The signal having the lowest potential is supplied to the movable body 12 of the objective lens driving device through the wire 3e, and is applied to the control electrodes 7a and 7e of the liquid crystal element, respectively. Further, both ends of the tracking coil 5 are connected by resistors 25a and 25b arranged in series, and an intermediate potential between the resistors 25a and 25b is input to a common electrode 7f of the liquid crystal element 7. Therefore, the liquid crystal element is driven based on the liquid crystal drive signal using the intermediate potential at both ends of the tracking coil 5 as the reference potential.

  As described above, the liquid crystal drive signal is generated using the intermediate potential at both ends of the tracking coil 5 as the reference potential and supplied to the control electrodes 7a and 7e of the liquid crystal element 7, and the intermediate potential at both ends of the tracking coil 5 is By supplying the driving signal to the common electrode 7f of the liquid crystal element 7, the driving signal can be supplied to the movable body 12 with six wires 3a to 3f.

  Therefore, by mounting the liquid crystal element 7 on the movable body 12, it is possible to realize an aberration correction function without deteriorating the aberration correction ability due to the movement of the objective lens 1 in the tracking direction T, and a power supply line to the liquid crystal element 7. Therefore, the supply of signals through a total of six wires 3 can be realized, thereby realizing a highly reliable support mechanism using a metal wire, and at the same time, reducing the variation factor and deteriorating the recording / reproducing signal due to the occurrence of AC tilt. And deterioration of control performance due to occurrence of unnecessary resonance can be suppressed.

  Further, since the number of wires is reduced, it is possible to minimize the material cost due to the increase in the number of parts, the operation cost due to the increase in the number of assembly steps, and the probability of occurrence of defective products. Further, since the above-mentioned effect can be realized only by the resistors 25a and 25b in addition to the liquid crystal element as a component mounted on the movable body 12, focusing can be performed at low cost while suppressing an increase in the weight of the movable body 12. The above effects can be realized without deteriorating the driving efficiency in the direction and the tracking direction.

  In the above description, the resistors 25a and 25b are described as separate components. However, like the voltage-dividing resistors 7h to 7k, the resistors 25a and 25b can be configured as a transparent thin-film resistor inside the liquid crystal element 7. The component mounted on the body 12 is only the liquid crystal element 7, and the driving efficiency in the focusing and tracking directions can be further reduced at a lower cost.

  In the above description, the reference potential of the liquid crystal drive signal is generated by the intermediate potential obtained by connecting the resistors 25a, 25b and 25c, 25d to both ends of the tracking coil 5, but the tracking coil 5 is replaced with the focusing coil. It is needless to say that the same effect can be obtained even if it is generated by an intermediate potential obtained by connecting the resistors 25a, 25b and 25c, 25d to both ends of 4.

  In the above description, the liquid crystal element 7 has a control electrode pattern for coma aberration correction by tilting in the radial direction R. However, the control electrode pattern is not limited to coma aberration correction but can be any type of aberration correction control. Similar effects can be obtained even with an electrode pattern. For example, the same effect can be obtained even with a pattern for correcting coma aberration by tilting in the tangential direction, a pattern for simultaneous correction of radial and tangential two axes, and a pattern for correcting spherical aberration.

  Furthermore, in the above description, the tilt sensor detects the amount of tilt error to generate the liquid crystal drive signal. However, it is sufficient that a signal that changes in accordance with the amount of tilt error can be detected. The liquid crystal drive signal may be generated such that the jitter value is detected and the value is minimized, or the liquid crystal drive signal is generated such that the amplitude of the reproduction signal of the disc is detected and the value is maximized. May be.

  The present invention is useful as an optical disk device, an objective lens driving device, and the like.

FIG. 2 is a circuit diagram of a driving circuit of the objective lens driving device according to the first embodiment of the present invention. 1 is a perspective view of an objective lens driving device according to a first embodiment of the present invention. FIG. 1 is an optical configuration diagram of an optical pickup including an objective lens driving device according to a first embodiment of the present invention. Pattern diagram of control electrodes of liquid crystal elements in objective lens driving device according to Embodiment 1 of the present invention Sectional drawing which shows the structure of the liquid crystal element in the objective lens drive device by Embodiment 1 of this invention. Circuit diagram of a drive circuit of an objective lens drive device according to a second embodiment of the present invention 2 is a perspective view of an objective lens driving device according to a second embodiment of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3a-3f Wire 4 Focusing coil 5 Tracking coil 6a, 6b Permanent magnet 7 Liquid crystal element 7a-7e Control electrode 7f Common electrode 7g Liquid crystal part 7h-7k Voltage division resistance 7m, 7n Base material 8a, 8b terminal Plate 9a Conductor 10 Base 11 Wire Holder 12 Movable Body 13 Tilt Sensor 14 Disk 15a to 15d Capacitor 16 Focusing Control Circuit 17 Tracking Control Circuit 18 Liquid Crystal Control Circuit 19 Semiconductor Laser 20 Polarizing Beam Splitter 21 Condensing Lens 22 1/4 Wavelength Plate 23 Cylindrical lens 24 Photodetector 25a-25d Resistance K Optical axis F Focusing direction T Tracking direction R Radial direction S Tangent direction

Claims (9)

An objective lens having an optical axis in a focusing direction which is a direction perpendicular to the disc-shaped recording medium, which is used by being incorporated in an apparatus for optically recording or reproducing information on a disc-shaped recording medium, and a lens holding the objective lens A movable body having a holder,
A base, a support member that movably supports the movable body with respect to the base in at least the focusing direction or a tracking direction that is a radial direction of the disc-shaped recording medium, and mounted on the movable body and at least the focusing direction. A focusing coil that generates a driving force, a tracking coil that is mounted on the movable body and generates at least the driving force in the tracking direction, and at least four energizing lines that supply a current to the focusing coil and the tracking coil.
A control electrode divided into a plurality of regions in a predetermined shape and a common electrode facing the control electrode, a liquid crystal element mounted on the movable body so as to be located on the optical axis of the objective lens,
Magnetic field generating means disposed on the base to apply a magnetic field to the focusing coil and the tracking coil,
An objective lens driving device, wherein a signal for driving the liquid crystal element is superimposed on a signal for driving the focusing coil or the tracking coil, and a signal is supplied using the same energizing line. An objective lens having an optical axis in a focusing direction which is a direction perpendicular to the disc-shaped recording medium, which is used by being incorporated in an apparatus for optically recording or reproducing information on a disc-shaped recording medium, and a lens holding the objective lens A movable body having a holder,
A base and the movable body are supported at least in the focusing direction or the tracking direction that is a radial direction of the disc-shaped recording medium with respect to the base so that the movable body can be elastically moved. A rod-shaped elastic support member made of at least four conductive materials fixed to a base, a focusing coil mounted on the movable body for generating a driving force in at least the focusing direction, and at least the tracking mounted on the movable body A tracking coil that generates a driving force in the direction;
A control electrode divided into a plurality of regions in a predetermined shape and a common electrode facing the control electrode, a liquid crystal element mounted on the movable body so as to be located on the optical axis of the objective lens,
Magnetic field generating means disposed on the base to apply a magnetic field to the focusing coil and the tracking coil,
An objective lens driving device, wherein a signal for driving the liquid crystal element is superimposed on a signal for driving the focusing coil or the tracking coil and a signal is supplied using the same rod-shaped elastic support member. . 3. The objective lens driving device according to claim 1, wherein a signal for driving the liquid crystal element to be superimposed and a signal for driving the focusing coil or the tracking coil have different frequency bands. The signal for driving the liquid crystal element to be superimposed is in a frequency band higher than a frequency band of a signal for driving the focusing coil or the tracking coil. Objective lens driving device. The objective lens driving device according to claim 4, wherein a frequency band of a signal for driving the liquid crystal element is 40 kHz or more. The objective lens driving device according to any one of claims 1 to 5, wherein the focusing coil or the tracking coil is driven by supplying a superimposed signal to the focusing coil or the tracking coil. The liquid crystal element is driven by converting the superimposed signal into a signal for driving the liquid crystal element by a predetermined electric circuit on the movable portion and supplying the signal to the liquid crystal element. 5. The objective lens driving device according to any one of 5. The liquid crystal element is driven by separating the superimposed signal from a signal for driving the liquid crystal element by a predetermined electric circuit on the movable part and supplying the separated signal to the liquid crystal element. 5. The objective lens driving device according to any one of 5. A signal for driving the focusing coil or the tracking coil by supplying a superimposed signal to the focusing coil or the tracking coil, and driving the liquid crystal element by a predetermined electric circuit on the movable portion by driving the superimposed signal. The objective lens driving device according to any one of claims 1 to 5, wherein the liquid crystal element is driven by converting the liquid crystal element into a liquid crystal element and supplying the liquid crystal element to the liquid crystal element.

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