JP4525470B2 - Optical disc driving apparatus, optical disc apparatus and driving method thereof - Google Patents

Description

  The present invention relates to an optical disk drive apparatus that performs at least one of signal recording and reproduction using near-field light, an optical disk apparatus equipped with this drive apparatus, and a drive method thereof.

  In recent years, in order to improve the recording density of an optical disk using a laser beam, an optical disk apparatus that records or reproduces a signal using near-field light has been proposed. In an optical disc apparatus using near-field light, the gap between the disc and the end surface of a SIL (Solid Immersion Lens) installed on a condensing element such as an objective lens unit is controlled to a distance (near field) where near-field light is generated. There is a need. This distance is generally ½ of the wavelength of the input laser beam. For example, when a 400 nm blue-violet laser is used, the thickness is about 200 nm.

  For this reason, an optical recording / reproducing apparatus using near-field light has an overshoot that occurs at a distance of 1 μm or less at the start of control of the gap, which is not particularly problematic in a far-field optical system such as a DVD (Digital Versatile Disk). Then it becomes a problem. That is, even if an overshoot of 1 μm or less occurs at the start of control, the SIL collides with the disk, causing damage to both.

  In order to solve such a problem, there is a method of controlling the gap based on the return light amount of the laser light reflected from the disk side. For example, when a laser beam having a wavelength of 400 nm is used, the near-field state is generally ½ or less of the wavelength. For this reason, in the distance of 200 nm or more, that is, in the far field state, all the light from the laser light source incident on the SIL end surface at an angle causing total reflection is reflected on the SIL end surface, and the return light amount is constant. However, when the gap length is 200 nm or less, that is, in the near field state, a part of the light incident on the SIL end face through the SIL end face at an angle causing total reflection penetrates the SIL end face. When the gap between the SIL and the disk is zero, that is, when the SIL and the disk come into contact with each other, all the light incident on the SIL end surface at an angle causing total reflection penetrates the SIL end surface, and the total reflected return light amount becomes zero. In this technique, the total reflected return light amount is detected by a photodetector, and this is fed back to an SIL actuator (for example, a biaxial device for performing forcing servo and tracking servo) to perform SIL gap servo ( For example, see Patent Document 1.)

Further, for example, a threshold for determining the near field state is set, and the SIL is brought close to the disk until the threshold is detected. After the threshold is detected, the servo voltage is added to the approach voltage to perform servo. There is also a method (see, for example, Patent Document 2). In this case, the approach voltage is a ramp-like voltage (FIG. 8, etc. of Patent Document 2), and when the initial speed of the SIL at the start of the approach occurs, the vibration of the SIL occurs at the beginning of the approach (see Patent Document 2). (See FIG. 12). However, after that, it follows the target value (a distance of several tens of nanometers from the disk) along the ramp-like voltage.
JP 2001-76358 A (paragraph [0026], FIG. 3) Japanese Patent Laying-Open No. 2004-30821 (paragraph [0030], FIGS. 8 and 12)

  However, even with the apparatus described in Patent Document 2, there is still concern about vibration due to the initial speed of the SIL at the start of approach. Therefore, in order to increase the margin for avoiding the collision between the SIL and the disk and to more stably pull the SIL to the near field or the target value in the near field, some device is required.

  In particular, the disk rotates during signal recording or reproduction, and at this time, a so-called surface blur occurs on the disk. Surface wobbling is a phenomenon in which the signal recording surface of a rotating disk periodically sways. The amount of surface blur is generally about 100 μm at the maximum in the case of a Blu-ray disc. In the case of a disk used in a near field optical system, it is desired that the disk is smaller than that. Causes of surface runout include, for example, the processing accuracy of the clamper that clamps the disc, the particles between the clamper and the disc, the processing accuracy of the disc itself, or the deflection of the disc. If such surface blurring occurs, the SIL may collide with the disk even if there is a margin for avoiding a collision as in Patent Document 2.

  In view of the circumstances as described above, an object of the present invention is to provide an optical disc driving apparatus capable of reliably preventing a light condensing element from colliding with a disc, an optical disc apparatus equipped with the driving device, and a driving method thereof. There is.

  In order to achieve the above object, an optical disk drive device according to the present invention is disposed to face a light source that emits light, a rotation mechanism that rotates a disk capable of recording a signal, and the disk that is rotated by the rotation mechanism. A condensing element capable of condensing the light emitted from the light source on the disk as near-field light, a separating / contacting mechanism for separating and contacting the condensing element to the disk, and a separating mechanism. Based on distance detection means for detecting the distance between the condensing element that is in contact with and away from the disk, peak value detection means for detecting a peak value of periodic shake of the rotating disk, and a detection signal of the distance detection means Servo control for making the distance between the condensing element and the rotating disk constant is a position on the disk where a shake corresponding to the vicinity of the detected peak value occurs. And control means for controlling to start.

  In the present invention, servo control is started at a position on the disk where a shake corresponding to the vicinity of the detected peak value occurs. Therefore, even if the rotating disk is shaken, the disk shake reaches a peak at the start of servo control, and the speed of the shake becomes almost zero. As a result, even if the disc is shaken, it is possible to prevent the light collecting element from colliding with the disc.

  “Nearby” a peak value means not only when the peak value is reached, but also immediately before reaching the peak value. That is, the optical disk drive device can grasp the start timing of the gap servo control from the stored shake amount by storing the periodic shake amount in the memory. Thereby, the servo control can be started at a timing immediately before reaching the peak value. “Nearby” means, for example, a time range of several microseconds or less, nanosecond order or less around the peak value.

  Alternatively, since the time required for servo control is sufficiently shorter than the disk rotation cycle, once the peak value is obtained without storing the amount of periodic fluctuation in the memory, the peak value or near the peak value thereafter. It is of course possible to perform servo control in real time at the timing at which is detected.

  As light, for example, blue or blue-violet laser light having a wavelength of about 400 nm is used. However, the present invention is not limited to this, and laser light having a wavelength smaller than 400 nm or larger than 400 nm may be used.

  The condensing element refers to an objective lens or an optical system including the objective lens, and may be any element that can be moved by a separation mechanism.

  Examples of the separation / contact mechanism include a mechanism that moves by electromagnetic action, electrostatic action, piezoelectric action, or the like.

  In the present invention, based on the detection signal of the distance detecting means, the control means moves the condensing element until the distance becomes a first distance at which the light is condensed on the disk as near-field light. Based on the detection signal of the distance detection means in a state where the distance is the first distance, the first control means for controlling the disk to approach the disk, and the distance between the condensing element and the disk is And second control means for controlling to be the constant second distance.

  The “distance collected on the disk as near-field light” controlled by the first control means is preferably larger than the “certain distance” controlled by the second control means. Thereby, the possibility that the light condensing element collides with the disk is reduced. However, this is not necessarily the case, and the “certain distance” may be smaller than or equal to the “distance collected on the disk as near-field light”. In short, the servo control may be performed in a state where the light condensing element enters the near field. As an example of the control by the first control means and the control by the second control means, specifically, it can be realized by the technique disclosed in Japanese Patent Application Laid-Open No. 2004-30821. Or it is realizable also with the following structures.

  In the present invention, the control means includes a voltage applying means for applying a voltage change to the separation / contact mechanism in order to cause the condensing element to be separated from / contacted by the separation / contact mechanism; Hold the voltage value when the distance detecting means detects that the light converging element has approached until the distance from the light source becomes the first distance at which the light is condensed on the disk as near-field light. A holding means capable of releasing the held voltage; and applying a voltage that maximizes the held voltage value to the separation / connection mechanism in a state where the held voltage is released; And a distance between the light condensing element and the disk based on the detection signal in a state where the distance is equal to or less than the first distance. And a second control means for controlling such that said constant second distance. In the present invention, the voltage value in the near field is held by the holding means, and the held voltage is once released by the first control means. Since a voltage with the held voltage as a maximum value is applied to the separation / contact mechanism, the condensing element approaches from the distance (far field) that is not the near field to the near field, and condenses when the near field is reached. The element speed is almost zero. At this time, as described above, the speed of disk shake is also substantially zero, and is controlled by the second control means in this zero state. Thereby, overshoot can be avoided.

  In the present invention, the peak value detecting means includes angle detecting means for detecting an angle between the light collecting element and the signal recording surface of the disc. In the case of the present invention, if the optical disk drive device grasps the radial position on the disk where the light converging element is present, the amount of shake at that position can be estimated based on the detected angle. However, in the case of the present invention, it is only necessary to know the position in the rotational direction on the disk where the vibration corresponding to the vicinity of the peak value occurs or the timing of the occurrence of the vibration corresponding to the vicinity of the peak value. Therefore, an accurate shake amount is not necessary, and the output of the angle detection means may be used as it is. The angle detection means may be a tilt sensor or the like. Since the tilt sensor can be used to control the angle between the light condensing element and the signal recording surface of the disc, the use of the tilt sensor is very effective.

  In the present invention, the second control means performs control in a state where the maximum voltage is applied to the separation / connection mechanism by the first control means. As in the present invention according to claim 2, the second control means performs control in a state where the distance is equal to or less than the first distance. In this case, the second control means is, for example, an integrator or the like. , And the voltage value of the hold voltage can be controlled to be the second distance in a state secured by the integrator. That is, after the maximum voltage is applied by the first control means, the voltage may be released, and the control by the first control means may not be used during the control by the second control means. However, when shifting from the time when the maximum voltage is released to the second control means, the release of the maximum voltage may cause a disturbance for the second control means. According to the present invention, it is possible to prevent the occurrence of such a disturbance and allow the light collecting element to approach the disk more smoothly.

  In the present invention, the distance detecting means has a measuring means for measuring a return light amount of the light emitted from the light source from the light collecting element, and the control means is the return measured by the measuring means. Control may be performed based on the amount of light.

  An optical disc device according to the present invention is arranged to face a light source that emits light, a rotation mechanism that rotates a disc capable of recording a signal, and the disk that is rotated by the rotation mechanism, and the light emitted from the light source A condensing element capable of condensing light on the disk as near-field light, a separating / contacting mechanism for separating / contacting the condensing element to / from the disk, the condensing element separated / contacted by the separating / contacting mechanism, and the Distance detecting means for detecting a distance from the disk, peak value detecting means for detecting a peak value of periodic shake of the rotating disk, and the light collecting element and the rotation based on a detection signal of the distance detecting means Control for controlling servo control to make the distance to the disk constant so as to start at a position on the disk where the shake corresponding to the vicinity of the detected peak value occurs. And stage, while being controlled by said control means comprises at least one of available recording / reproducing mechanism of the play that and the recorded signal for recording the signal on the disc. In other words, the optical disc apparatus according to the present invention is obtained by adding the constituent elements of the “recording / reproducing mechanism” to the optical disc driving apparatus.

  The optical disk drive device driving method according to the present invention includes a light source that emits light, a rotation mechanism that rotates a disk capable of recording signals, and a disk that is rotated by the rotation mechanism and is opposed to the disk. A driving method of an optical disk drive device comprising a light collecting element capable of condensing the emitted light as near-field light on the disk, and detecting a peak value of periodic shaking of the rotating disk A servo control for detecting a distance between the disk and the condensing element and making the distance between the condensing element and the rotating disk constant based on the distance detection signal; Start at a position on the disk where a shake corresponding to the vicinity of the value occurs.

  As described above, according to the present invention, it is possible to reliably prevent the light collecting element from colliding with the disk.

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

  FIG. 1 is a diagram showing a configuration of an optical disc driving apparatus according to the first embodiment of the present invention. The optical disk drive 1 includes an optical head 28, a servo control system 40, and a spindle motor 48. The optical head 28 includes a laser diode (LD) 31 serving as a light source, collimator lenses 32 and 46, an anamorphic prism 33 for shaping laser light, a beam splitter (BS) 34, a quarter wavelength plate (QWP) 43, and chromatic aberration correction. It has a lens 44, a laser beam expansion lens 45, a Wollaston prism 35, condensing lenses 36 and 38, a condensing element 5, photo detectors (PD) 37 and 39, an auto power controller 41, and an LD driver 42.

  The Wollaston prism 35 is composed of two prisms, and light incident on the Wollaston prism 35 is emitted as two linearly polarized lights that are orthogonal to each other. The PD 37 outputs, to the servo control system 40, an RF reproduction signal for reproducing a signal recorded on the optical disc, a tracking error signal necessary for servo control, a gap error signal, and the like.

  The servo control system 40 includes a gap servo module (focusing servo module) 51, which will be described later, a tracking servo module 52, a tilt servo module 53, and a spindle servo module 54. The tracking servo module 52 performs tracking control of the light collecting element 5 based on the tracking error signal. The tilt servo module 53 controls the tilt angle of the light collecting element 5. The spindle servo module 54 controls the rotation of the spindle motor 48.

  The auto power controller 41 outputs a predetermined signal to the LD driver 42 based on the signal output from the PD 39 so that the laser power output from the LD 31 is constant.

  Next, the overall operation of the optical disk drive 1 will be described. For example, an optical disc 47 serving as a recording medium is set in the optical disc driving apparatus 1. Then, each servo control is performed by the servo control system 40. On the other hand, the laser light emitted from the LD 31 is converted into parallel light by the collimator lens 32 and shaped by the anamorphic prism 33. The laser light incident on the BS 34 is split by the BS 34 into light incident on the QWP 43 and light incident on the condenser lens 38. The laser light incident on the condenser lens 38 is controlled to have a constant power by the auto power controller 41 as described above. The light that has entered the QWP 43 is converted into circularly polarized light by the QWP 43, the chromatic aberration is corrected by the chromatic aberration correction lens 44, and enters the light collecting element 5 via the expansion lens 45 and the collimator lens 46.

  The laser light incident on the condensing element 5 is condensed as near-field light on the optical disc 47 as will be described later, and a signal is recorded on the optical disc 47. Alternatively, the laser light collected as near-field light on the optical disc 47 is incident on the optical disc 47 in order to read out the signal recorded on the optical disc 47, and the reflected light or diffracted light from the optical disc 47 is used as the condensing element 5. Receive. Reflected light or diffracted light from the optical disk 47 enters the BS 34 via the condensing element 5 as return light via the collimator lens 46, the expansion lens 45, the chromatic aberration correction lens 44, and the QWP 43. The laser light totally reflected by the BS 34 enters the PD 37 via the Wollaston prism 35 and the condenser lens 36. The PD 37 obtains an RF reproduction signal and a servo control signal, and the servo control signal is input to the servo control system 40 to perform each servo control.

  FIG. 2 is a side view showing the condensing element 5 and the optical disc 47. The condensing element 5 is disposed to face the optical disc 47. The condensing element 5 is configured by accommodating a SIL 2 and an aspheric lens 3 in a lens holder 4. The condensing element 5 is not limited to such a form, and may have any form as long as the laser light 24 can be guided to the optical disc 47 as near-field light. The end surface 2 a of the SIL 2 is disposed so as to face the recording surface 47 a of the disk 47. The lens holder 4 is installed on a triaxial actuator 6 constituting at least a part of the separation / contact mechanism. Although the triaxial actuator 6 is simplified in the figure, it is composed of, for example, a triaxial coil, a yoke, etc., and a focusing servo including a tracking servo and a gap servo when a current with a predetermined servo voltage flows through each coil. And tilt servo control. Note that the tracking servo module 52 and the tilt servo module 53 are not necessarily required when the present invention is applied to the optical disc driving apparatus 1 according to the embodiment.

  FIG. 3 is a block diagram showing an outline of the gap servo module 51. The controlled object is a triaxial actuator 6. Further, the detection amount (controlled amount) is the total reflected return light amount 24, which is detected by the PD 37 as described above. The detected total reflection return light amount 24 is normalized to 1 V, for example, by the normalization gain 18. The standardized signal is digitized by an AD (analog to digital) converter 19. The digitized total reflected return light amount is input to the data processing unit 10. The data processing unit 10 outputs a voltage for causing the SIL 2 of the light condensing element 5 to approach the optical disc 47, converted into an analog signal by a DA (digital to analog) converter 11, and output as an approach voltage 14. The A gap error signal 27 is input to the filter 13, converted to an analog signal by the DA converter 12, and output as a servo voltage 15. The approach voltage 14 and the servo voltage 15 are added and input to the driver 16, and the driver 16 drives the triaxial actuator 6 so that the gap error becomes zero.

  FIG. 4 is a block diagram showing details of the data processing unit 10.

  The data processing unit 10 receives the total reflected return light amount 24 and the gap servo switch 9. The gap servo switch 9 is, for example, a signal that is input to the data processing unit 10 when the optical disk 47 is loaded in the optical disk drive device 1, but is not limited to this time.

  The near-field detection level setting unit 21 sets a near-field detection level (voltage threshold for starting the gap servo), and the near-field detection level 8 is input to the system controller 20. The system controller 20 compares the total reflected return light amount 24 inputted with the near-field detection level 8 and, based on the comparison result, sends a predetermined control signal to the approach voltage generator 23 and the switch 26 as will be described later. Output.

  The near field detection level 8 is set as shown in FIG. 5, for example. That is, the near-field detection level 8 is set to a value larger than the target value 7 of the gap servo in the near field region. For example, in FIG. 5, when the value of the total reflected return light amount 24 in the far field region is normalized to 1 (V), it is set to 0.8 (V) in the linear region. The gap servo target value 7 is set by the gap servo target value setting unit 22 (see FIG. 4). As shown in FIG. 5, the gap servo target value 7 is set to a value smaller than 0.8 (V) within the linear region, for example, 0.5 (V).

  The system controller 20 compares the near-field level 8 with the total reflected return light amount (corresponding voltage value) 24. Based on the comparison result of the system controller 20, for example, when the total reflected return light amount 24 is larger than the near-field detection level 8, that is, when the SIL 2 is at the far field distance, the output signal 29 to the switch 26 of the system controller 20 becomes Low. . On the other hand, when the total reflected return light amount 24 is smaller than the near-field detection level 8, that is, when the end surface 2a of the SIL 2 is a near field distance, the output signal 29 becomes High. When the output signal 29 of the system controller 20 becomes High, the switch 26 is turned ON and the gap servo is started for the first time. The total reflected return light amount 24 is deviated by the gap servo target value 7 and input to the switch 26 as a deviation signal 25.

  The switch 26 outputs the deviation signal 25 as the servo voltage 27 when it is turned on as described above, that is, when there is a signal to start the gap servo. By such a gap servo, the gap between the end surface 2 a of the SIL 2 and the recording surface 47 a of the disk 47 is controlled so as to coincide with the gap servo target value 7.

  FIG. 6 is a block diagram showing a configuration of the approach voltage generator 23. The approach voltage generator 23 includes a ramp voltage generator 55, a sample hold circuit 57, a step voltage generator 56, a low pass filter 58, and a switch 59.

  When the control signal 65 from the system controller 20 based on the gap servo switch signal 9 is input, the ramp voltage generator 55 generates a ramp voltage and outputs it to the sample hold circuit 57.

  The sample hold circuit 57 generates a voltage generated by the lamp voltage generator 55 when there is a hold signal 67 from the system controller 20 based on the total reflected return light amount 24 being smaller than the near field detection level signal 8. Hold. The sample hold circuit 57 outputs the input ramp-shaped voltage or the voltage 62 obtained by holding it to the switch 59 and the step voltage generator 56.

  The step voltage generator 56 generates a step-like voltage when there is a control signal 66 from the system controller 20 based on the fact that the total reflected return light amount 24 is smaller than the near-field detection level signal 8, and a low-pass voltage is generated. Output to the filter 58.

  As shown in FIG. 7, the low-pass filter 58 outputs a voltage signal 63 obtained by integrating the voltage signal 64 to the switch 59.

  The switch 59 selects one of the hold voltage signal 62 and the output signal 63 of the low-pass filter 58 under the control signal 69 of the system controller 20, and outputs the selected one as the approach voltage 14.

  The operation of the gap servo module 51 configured as described above will be described. FIG. 8 is a flowchart showing an example of the operation. FIG. 9 is a timing chart showing the voltage applied to the triaxial actuator 6 and the total reflected return light amount in the operation.

  When the gap servo switch is turned on at time t0 and the signal 9 is input to the system controller 20 (step 801), the system controller 20 outputs a control signal 65 to the ramp voltage generator 55. Based on the control signal 65, the ramp voltage generator 55 generates a ramp voltage 71 (see FIG. 9) (step 802). The ramp voltage 71 is input to the switch 59, and the system controller 20 causes the switch 59 to output the voltage 62 as the approach voltage 14. The approach voltage 14 is input to the driver 16, and the driver 16 drives the triaxial actuator 6 based on the approach voltage 14. As a result, the condensing element 5 approaches the disk 47, and the total reflected return light amount starts to decrease, and the end surface 2a of the SIL 2 enters the near field.

  As shown in FIG. 5, for example, when the voltage of the total reflected return light amount 24 becomes 0.8 V or less, which is a voltage corresponding to the near-field detection level 8, (YES in Step 803), the system controller 20 outputs a hold signal 67 to the sample hold circuit 57. Based on this, the sample hold circuit 57 holds the ramp-shaped input voltage (step 804). In FIG. 9, the hold voltage at this time is V (V). The system controller 20 switches the switch 59 together with the output of the hold signal 67, thereby temporarily releasing the ramp-like approach voltage 14 that has been applied so far (step 805).

  Thereafter, the system controller 20 outputs a signal 66 for generating a stepped voltage in the step voltage generator 56 to the step voltage generator 56. Based on this, the step voltage generator 56 generates a step-like voltage with the maximum voltage V (V) at time t2 (step 806) (see FIG. 7). The hold voltage value V (V) may be stored in, for example, a memory (not shown) included in the system controller 20 or another memory. A step-like voltage is input to the switch 59 via the low-pass filter 58, and this signal is applied to the triaxial actuator 6 as the approach voltage 14. Since the approach voltage 14 from time t2 has the maximum value V (V), the speed of the SIL2 is almost zero when the end surface 2a of the SIL2 approaches the disk 47 to a position corresponding to the near field detection level 8. This is point A) at time t3. Further, when the voltage corresponding to the total reflected return light amount 24 becomes equal to or lower than the near-field detection level 8 (YES in Step 807), the system controller 20 sets the gap servo target value set by the gap servo target value setting unit 22. With the value 7 as a target value, the switch 26 is turned on to output the servo voltage 27 (step 808).

  FIG. 10 shows a change in the gap servo target value generated by the gap servo target value setting unit 22. The system controller 20 starts the gap servo so as to follow the target value based on the gap servo target value in a state where the approach voltage 14 of the constant value V (V) is applied.

  As described above, in this embodiment, the initial speed of the SIL 2 is zero at the time (t3) when the gap servo is started, and the gap servo is started from the initial speed zero. Accordingly, in FIG. 9, SIL 2 can be made to approach smoothly to the gap servo target value 7 as indicated by the waveform 73 of the total reflected return light amount. On the other hand, in the apparatus described in Patent Document 2, there is a concern about vibration due to the initial speed of the SIL as shown in FIG.

  Further, in the present embodiment, in the state where the approach voltage 14 is applied and the end surface 2a of the SIL 2 is in the near field, a voltage obtained by adding the servo voltage 27 to the approach voltage 14 is applied to the triaxial actuator 6. . As a result, the light condensing element 5 can be brought close to the disk 47 smoothly.

  It is also conceivable that the initial position of the light collecting element 5 (SIL2) before application of the approach voltage is set in advance so that the initial speed of the SIL2 becomes substantially zero when the near-field detection level is detected. However, in such a method, the initial position must be determined experimentally and experimentally. On the other hand, in the present embodiment, automatic control is possible, so that it is not necessary to design according to the form of the disk drive device or the disk itself.

  Next, an optical disk drive apparatus according to a second embodiment of the present invention will be described. In the second embodiment, the same members, functions, etc. of the optical disk drive device 1 according to the first embodiment will be described briefly or omitted, and different points will be mainly described.

  FIG. 11 is an enlarged view of the vicinity of the light collecting element according to the second embodiment. As shown in FIG. 11, a tilt sensor 29 is fixed to the lens holder 4 of the light collecting element 5. The tilt sensor 29 is a sensor that detects an inclination (angle) of the end surface 2a of the SIL 2a with respect to the signal recording surface 47a of the optical disc 47 (hereinafter, this angle is referred to as a tilt angle).

  FIG. 12 shows the mechanism of the tilt sensor 29. The tilt sensor 29 includes a laser light emitting unit 110 and a light receiving unit 111. The laser light emitted from the light emitting unit 110 irradiates and reflects the disk 47, and the light receiving unit 111 receives the return light.

  FIG. 13 is a plan view of the tilt sensor 29. The light receiving unit 111 is divided into two parts, an A part and a B part. The amount of light received by the A part or B part of the light receiving unit 111 varies depending on the tilt of the disk 47 with respect to the tilt sensor 29. Therefore, the tilt angle can be determined by taking the difference between the A portion and the B portion.

  FIG. 14 shows an output waveform of the tilt sensor 29. In FIG. 14, a voltage that is linear, that is, proportional to the tilt angle can be obtained within the tilt error detection range. Thus, if the tilt angle is known, the amount of surface deflection of the disk 47 can be estimated by using the tilt sensor 29.

FIG. 15 is a diagram for explaining a method for estimating the amount of surface shake based on the detection signal of the tilt sensor 29. In FIG. 15A, when the disc 47 is not shaken, the tilt angle of the disc 47 with respect to the tilt sensor 29 becomes zero. On the other hand, in FIG. 15 (b) or FIG. 15 (c), when the disc 47 is shaken, a tilt of + θ or −θ occurs with respect to the tilt sensor 29. What can be detected by the tilt sensor 29 is θ (tilt angle), and what is desired to be obtained is the surface shake amount d. The tilt angle θ is expressed as in equation (1).
sin θ = d / r (1)
In the equation (1), the tilt angle is very small and can be approximated to θ = d / r. Therefore, the surface shake amount d is calculated by the following equation (2).
d = r · θ (2)

  Attention is now paid to the tilt of the disk 47 with respect to the tilt sensor 29. However, since the tilt sensor 29 is fixed to the condensing element 5 as shown in FIG. 11, the “tilt angle” referred to in the present embodiment is the condensing element 5 (or the end surface 2a of the SIL 2) with respect to the disk 47. ) Tilt. That is, it is an angle between the disk 47 and the condensing element 5 and is a relative one. However, the present invention is not limited to this configuration, and at least a sensor for detecting the angle between the light collecting element 5 and the signal recording surface 47a of the disk 47 may be provided somewhere in the optical disk drive device.

  The tilt angle θ obtained by the tilt sensor 29 is constant regardless of the position of the tilt sensor 29 on the disk 47 in the radial direction of the disk 47. Therefore, in order to estimate the above-mentioned surface shake amount d (see Expression (2)), the position of the tilt sensor 29 on the disk 47 in the radial direction of the disk 47 (hereinafter referred to as the radial position) is grasped. There is a need. However, in the case of the present embodiment, as will be described later, the position in the rotation direction on the disk where the surface shake corresponding to the vicinity of the peak value of the surface shake amount occurs, or the surface corresponding to the vicinity of the peak value. It is only necessary to know the timing at which blurring occurs. Therefore, an accurate surface blur amount is not required, and the output of the tilt sensor 29 may be used as it is for peak detection.

  FIG. 16 is a block diagram showing the configuration of the gap servo module according to the second embodiment. The output of the tilt sensor 29 is input to the peak detector 30. The peak detector 30 estimates a surface shake amount based on a detection signal from the tilt sensor 29 and detects a peak value of the surface shake amount. FIG. 17 is a diagram illustrating an example of the amount of surface blur calculated by the peak detector 30. As described above, the same surface blur occurs every rotation period T of the disk 47. In the figure, for example, a deviation occurs in the periods a and c, and the inclination is negative in the periods b and d. As described above, the plus and minus correspond to the positive / negative of the tilt angle shown in FIG. 14 or the positive / negative of the surface blur amount d shown in FIG.

  The detection signal from the tilt sensor 29 is fed back to the tilt servo module 53 (see FIG. 1) and is controlled by the tilt servo module 53 so that the tilt angle becomes substantially zero as described above.

  In FIG. 17, at the top dead center X and the bottom dead center Y of the surface shake amount, the speed due to the surface shake of the disk 47 becomes zero. The peak detector 30 outputs a peak value detection timing signal 49 to the data processing unit 10 at the timing when the top dead center X or the bottom dead center Y is reached. The data processing unit 10 has the same configuration as that shown in FIGS.

  The operation of the optical disk drive configured as described above will be described. FIG. 18 is a flowchart showing the operation.

  When the disk 47 starts to be rotated by the spindle motor 48 (step 1701), the surface shake amount based on the detection signal of the tilt sensor 29 is measured (step 1702). The measurement of the amount of surface blur may be always performed. Alternatively, it may be performed after the rotational speed of the disk 47 reaches a predetermined rotational speed. Actually, while the disk 47 is rotating, the tilt sensor 29 works at any rotational speed, and the amount of surface shake is always measured as the output of the tilt sensor 29. The predetermined number of rotations may be, for example, the number of rotations at the time of signal recording or reproduction, or may be more or less.

  When the surface shake amount is measured and the surface shake amount reaches the peak value, that is, the top dead center X or the bottom dead center Y (YES in step 1703), SIL2 pull-in is started (step 1704). Here, in step 1703, the peak detector 30 may store the peak value from, for example, the amount of surface blur for at least one period after the first rotation or the subsequent rotation of the disk 47, for example. As a method for storing the peak value, for example, a voltage value corresponding to the peak value may be stored by a peak hold circuit or the like, and the peak value is determined by comparing the peak value with the output from the tilt sensor 29. It becomes possible to detect in real time. On the other hand, when the blur amount itself is stored, a surface blur signal corresponding to a count value of a pulse signal generated by an encoder (not shown) of the spindle motor 48 is stored in the memory. In this case, for example, a semiconductor memory or the like is used as the memory.

  In step 1704, the gap servo module 151 may perform the operations from step 802 to step 808 as shown in FIG. 8 when the data processor 10 receives the timing signal 49. Alternatively, in step 1704, steps 802 to 805 may be performed in the vicinity of a peak value in a certain cycle, and steps 806 to 808 may be performed in the vicinity of the peak in the next or subsequent at least one cycle.

  In FIG. 17, for example, when servo control is started at point E, the blur speed of the disk 47 is not zero, so there is a possibility of causing an overshoot as shown in FIG. 19, which is an ideal operation as shown in FIG. 10. There is a risk that However, in FIG. 19, overshoot occurs, but SIL2 does not collide with the disk 47.

  In contrast, in the present embodiment, servo control is started at a position on the disk 47 where a shake corresponding to the vicinity of the detected peak value occurs (servo control here refers to steps 802 to 805). Or control from step 802 to step 808.) Thus, even if the rotating disk 47 has runout, the runout peaked at the start of servo control, and the speed of the runout Nearly zero. Therefore, even when the disc 47 is shaken, the SIL 2 can be prevented from colliding with the disc.

  The present invention is not limited to the embodiment described above, and various modifications are possible.

  The optical system, sensor, and the like of the optical head 28 shown in FIG. 1 are merely examples, and are not limited to the functions and arrangement shown in FIG.

  In FIG. 8, ramp-like and step-like voltages are applied in step 802 and step 806. However, the voltage is not limited to these waveforms, and may be a voltage having a waveform similar to this. For example, in step 802, the stepped voltage can be changed to a voltage having a low-pass waveform. In step 806, a ramp-like voltage may be used, and this may be filtered with a low-pass filter having a relatively small time constant.

  In FIG. 9, the maximum voltage V is released at time t1, and the approach voltage application is resumed at t2. For example, once the maximum voltage V is stored, after the disk 47 is loaded in the optical disk apparatus, the operation of applying the ramp voltage 71 and releasing it once every repeated recording or reproducing operation is not performed. May be. That is, once the maximum voltage V is stored, the operation can be started from t2 in the second and subsequent recording or reproducing operations. Next, the operation of storing the maximum voltage V may be performed when another disk is loaded. However, it is of course possible to perform the operation from t0 and record the maximum voltage V for each recording or reproducing operation of one disc.

  Instead of the tilt sensor 29, a configuration in which the surface shake amount is measured by a laser Doppler interferometer, a laser displacement meter, or the like may be used. In this case, the laser Doppler interferometer or the like may be fixed to the condensing element 5 or may not be fixed.

It is a figure which shows the structure of the optical disk drive device based on the 1st Embodiment of this invention. It is the side view which showed the condensing element and the optical disk. It is a block diagram which shows the structure of a gap servo module. It is a block diagram which shows the structure of a data processing part. It is a graph which shows the relationship between a gap and the total reflected return light quantity. It is a block diagram which shows the structure of an approach voltage generation part. It is a figure which shows a mode when a step voltage is low-pass-filtered. It is a flowchart which shows an example of operation | movement of a gap servo module. FIG. 9 is a timing chart showing a voltage applied to a triaxial actuator and a total reflection return light amount in the operation in FIG. 8. It is a figure which shows the change of the gap servo target value produced | generated by the gap servo target value setting part. It is an enlarged view near the condensing element which concerns on the 2nd Embodiment of this invention. It is a figure which shows the mechanism of a tilt sensor. It is a top view of a tilt sensor. It is an output waveform of a tilt sensor. It is a figure for demonstrating the method when estimating the said amount of surface blurring based on the detection signal of a tilt sensor. It is a block diagram which shows the structure of the gap servo module which concerns on 2nd Embodiment. It is a figure which shows the example of the amount of surface blurring calculated by a peak detector. 6 is a flowchart showing the operation of the optical disk drive device according to the second embodiment. It is a figure which shows the state in which the overshoot has generate | occur | produced.

Explanation of symbols

V ... Hold voltage value 1 ... Optical disk drive device 5 ... Condensing element 6 ... Triaxial actuator 7 ... Gap servo target value 8 ... Near field detection level 10 ... Data processing unit 14 ... Proximity voltage 20 ... System controller 24 ... Total reflection return Light quantity 27 ... Servo voltage 30 ... Peak detector 31 ... Laser diode (LD)
37 ... Photo detector (PD)
47 ... Optical disc 51, 151 ... Gap servo module 57 ... Sample hold circuit

Claims (6)

A light source that emits light;
A rotating mechanism for rotating a disc capable of recording signals;
A light condensing element that is disposed to face the disk rotated by the rotating mechanism and is capable of condensing the light emitted from the light source onto the disk as near-field light;
A separation / contact mechanism for separating the light-collecting element from the disk;
A distance detecting means for detecting a distance between the light condensing element and the disc separated by the separation mechanism;
An angle detection means for detecting an angle between the light condensing element and the signal recording surface of the disk; and a peak value detection means for detecting a peak value of a periodic shake of the rotating disk by the angle detection means; ,
Servo control for making the distance between the light condensing element and the rotating disk constant based on the detection signal of the distance detection means is performed on the disk where the shake corresponding to the vicinity of the detected peak value occurs. An optical disk drive comprising: control means for controlling to start at a position. The optical disk drive device according to claim 1,
The control means includes
Based on the detection signal of the distance detecting means, the distance is controlled so that the condensing element is brought close to the disk until the distance becomes a first distance at which the light is condensed on the disk as near-field light. 1 control means;
In a state where the distance is the first distance, a second control is performed so that the distance between the light condensing element and the disk becomes the constant second distance based on a detection signal of the distance detection means. An optical disc drive apparatus comprising: The optical disk drive device according to claim 1,
The control means includes
Voltage application means for applying a voltage change to the separation / contact mechanism in order to cause the condensing element to be separated from / contacted by the separation / contact mechanism;
The distance detecting means detects that the condensing element has approached until the distance from the disk becomes a first distance at which the light is condensed on the disk as near-field light by the separation / contact mechanism. Holding means capable of holding the voltage value at the time and releasing the held voltage;
A first control for controlling the distance to be equal to or less than the first distance by applying a voltage that maximizes the held voltage value to the separation mechanism in a state where the held voltage is released. Control means,
Second control means for controlling the distance between the condensing element and the disk to be the constant second distance based on the detection signal in a state where the distance is equal to or less than the first distance. An optical disc drive device comprising: The optical disk drive device according to claim 2,
The optical disc drive apparatus, wherein the second control means controls the maximum voltage applied to the separation / connection mechanism by the first control means. The optical disc apparatus according to claim 1,
The distance detecting means has a measuring means for measuring the amount of light returned from the light collecting element of the light emitted from the light source,
The optical disk drive apparatus for controlling the control means based on the return light quantity measured by the measuring means. A light source that emits light;
A rotating mechanism for rotating a disc capable of recording signals;
A light condensing element that is disposed to face the disk rotated by the rotating mechanism and is capable of condensing the light emitted from the light source onto the disk as near-field light;
A separation / contact mechanism for separating the light-collecting element from the disk;
A distance detecting means for detecting a distance between the light condensing element and the disc separated by the separation mechanism;
An angle detection means for detecting an angle between the light condensing element and the signal recording surface of the disk; and a peak value detection means for detecting a peak value of a periodic shake of the rotating disk by the angle detection means; ,
Servo control for making the distance between the light condensing element and the rotating disk constant based on the detection signal of the distance detection means is performed on the disk where the shake corresponding to the vicinity of the detected peak value occurs. Control means for controlling to start at a position;
An optical disc apparatus comprising: a recording / reproducing mechanism capable of at least one of recording the signal on the disc and reproducing the recorded signal in a state controlled by the control means.

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