JP2010211850A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly set a signal value for deciding control constant of focus servo even when the focus servo is performed by an optical disk that has irregular amount of wobble. <P>SOLUTION: An optical device is provided with: an actuator 31 moving the focal point of a beam emitted to an optical disk 1 by driving an objective lens 32; a photodetector 4 detecting the beam reflected from the optical disk 1 and outputting it as a detection signal; and a servo control part 8 controlling the focal point of the beam from the detection signal of the photodetector 4 by driving the actuator 31. The servo control part 8 has a focus servo part 80 for inputting the detection signal of the photodetector 4 and driving the actuator 31 so that the beam is in focus on the basis of the predetermined control constant, and an initializing part 90 for deciding the control constant from the detection signal when the objective lens 32 is located within a predetermined range when the detection signal of the photodetector 4 is in focus. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical disk device, and more particularly to a technique for adjusting a focus error signal amplitude.

  In an optical disc apparatus that records information on an optical disc such as a CD (Compact Disc), a DVD (Digital Versatile Disc), or a BD (Blu-ray Disc), the focus servo adjustment that maintains the distance between the recording surface of the optical disc and the objective lens is It has been a problem from the past. In the conventional optical disk device, in order to correct the surface shake of the optical disk, a reference value for determining a focus servo control constant (such as a gain) using a focus error signal and an intensity signal detected from the optical sensor is set as an individual optical disk device. Set every time. Then, the optical disk device determines a control constant of the focus servo based on the set reference value, and displaces the objective lens by this control constant so that the beam from the laser is focused on the recording surface. Maintain the distance between the recording surface and the objective lens. For example, Patent Document 1 is known as an optical disk device that performs such focus servo.

JP 2006-73178 A

  In the optical disk device as described in Patent Document 1, a control constant (for example, a feedback gain) that follows the surface shake of the optical disk is obtained from the focus error signal at the start of focus servo. In this method, the value of the focus error signal when the objective lens that irradiates the laser is displaced and focused is learned, and the control constant is determined from this learned value.

  The amount of surface blur of an optical disk is determined by the standard of each disk. Normally, the amount of surface blur of an optical disk is within the range of the standard of each disk, but in recent years, optical disks have been manufactured in various parts of the world. In other cases, optical discs of poor quality must be reproduced / recorded by the optical disc device.

  When focus servo is started with an optical disc whose surface deflection is outside the standard range, the objective lens is driven in the same way as in the above conventional example, and when the focus error signal at the point of focus is learned, the amplitude level of the focus error signal Is smaller than that of an optical disc having a surface blur amount within a standard range. When the focus servo control constant is determined with the focus error signal having a low amplitude level, the follow-up performance of the focus servo may be reduced or the servo system may oscillate.

  Accordingly, the present invention has been made in view of the above problems, and even when focus servo is performed with an optical disc having a non-standard surface blur amount, a signal value for determining a focus servo control constant is appropriately set. For the purpose.

  The present invention provides a rotation control unit that controls the rotation of an optical disc, an objective lens that irradiates the optical disc with a beam from a laser, and drives the objective lens to move the focus of the beam that irradiates the optical disc in the focus direction. An actuator; an optical sensor that detects the beam reflected from the optical disk and outputs the detection signal; and a servo control unit that drives the actuator to control the focus of the beam from the detection signal of the optical sensor. In the optical disc apparatus, the servo control unit receives a detection signal of the optical sensor, and drives the actuator so that the beam is in focus based on a predetermined control constant; and the focus servo unit An initialization unit that inputs a detection signal of an optical sensor and determines the control constant; The initialization unit drives the optical disk at a predetermined rotation frequency to the rotation control unit and drives the actuator at a predetermined sweep frequency, and the beam is transmitted from the detection signal from the optical sensor. When it is detected that the optical disk is connected at a predetermined position as an in-focus state, and the position of the objective lens is within a predetermined range, a detection signal from the optical sensor is used to control the actuator. A learning unit that acquires the learning value; and a control constant setting unit that determines a control constant for driving the actuator from the acquired learning value.

  Therefore, according to the present invention, when the in-focus state is determined from the detection value of the optical sensor while driving the objective lens, the detection value of the optical sensor is used as a learning value when the position of the objective lens is within a predetermined range. Since the focus servo control constant is determined from this learned value, it is possible to determine the control constant from the learned value when the relative speed between the objective lens and the surface of the optical disk is high. Even when an optical disk exceeding the standard range is used, the followability of the focus servo can be ensured.

1 is a block diagram illustrating an optical disk device according to an embodiment of the present invention. FIG. 3 is a functional block diagram of a servo control unit according to the embodiment of this invention. The wiring diagram of the principal part of the connector for a branch, a branch cable, and a protocol analyzer which shows the 1st Embodiment of this invention. 4 shows an embodiment of the present invention, the position of the objective lens, the position of the optical disc, the relative speed of displacement of the optical disc surface and the objective lens in the focus direction, the amplitude value of the focus error signal, the value of the sum signal, and the time. This graph shows an example in which the sweep cycle of the objective lens is extremely longer than the rotation cycle of the optical disk. 4 shows an embodiment of the present invention, the position of the objective lens, the position of the optical disc, the relative speed of displacement of the optical disc surface and the objective lens in the focus direction, the amplitude value of the focus error signal, the value of the sum signal, and the time. In the graph showing the relationship, an example in which the sweep cycle of the objective lens approximates the rotation cycle of the optical disk is shown. 4 shows an embodiment of the present invention, the position of the objective lens, the position of the optical disc, the relative speed of displacement of the optical disc surface and the objective lens in the focus direction, the amplitude value of the focus error signal, the value of the sum signal, and the time. This graph shows an example in which the sweep cycle of the objective lens is extremely shorter than the rotation cycle of the optical disk.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration of an optical disk device according to an embodiment of the present invention.

  An optical disk apparatus according to an embodiment of the present invention includes a disk motor 2, an optical pickup 3, a photodetector 4, a temperature sensor 5, a motor drive unit 6, an RF signal generation unit 7, a servo control unit 8, and a laser power control unit 9. A laser driver 10, a decoder 11, a control unit 12, a memory 13, and an encoder 14.

  The disk motor 2 is driven by the motor driving unit 6 and rotates the optical disk 1. The motor drive unit 6 controls the rotation (rotation / stop, rotation speed) of the motor in accordance with an instruction from the control unit 12 constituted by a microcomputer.

  The optical pickup 3 is mainly composed of an actuator 31, an objective lens 32, a laser 33, a light receiving unit, a splitter, a photodetector 4 (optical sensor), and a temperature sensor 5. The laser 33 is a semiconductor laser (light emitting unit) that generates laser light (beam) having a predetermined intensity for recording and reproduction. Laser light emitted from the laser 33 is applied to the recording surface (optical disc surface) of the optical disc 1 through the objective lens 32. The light receiving unit receives the laser light reflected by the recording surface of the optical disc 1 through the objective lens 32, converts the received reflected light into an electric signal, and outputs the converted electric signal as a detection value. The objective lens 32 is driven by the actuator 31 and is adjusted so that the laser beam is focused on the optical disk surface. The actuator 31 is driven by the servo control unit 8. As an example of the optical pickup 3, as shown in FIG. 2, a splitter 34 is disposed between the objective lens 32 and the laser 33, and a cylindrical lens 35 that guides the laser light from the splitter 34 to the photodetector 4 is provided. A configuration is shown in which the detector 4 outputs a focus error signal by the critical aberration method.

  Laser light generated by the laser 33 is irradiated onto the optical disc 1 from the objective lens 32 via a splitter 34 (see FIG. 2), and laser light reflected from the optical disc 1 (hereinafter referred to as reflected light) is transmitted to the photodetector 4 by the splitter 34. Led. The laser beam generated by the laser 33 is separated by the splitter 34 and guided to the photodetector 4. The photodetector 4 outputs a detection value by the reflected light from the splitter 34 and the laser light separated by the splitter 34, and each control unit monitors the focus position of the laser light and the power of the laser light. The temperature sensor 5 detects the temperature of the optical pickup 3.

  The RF signal generation unit 7 performs analog processing (amplification, demodulation, etc.) of the signal from the optical pickup 3.

  The servo control unit 8 controls focus servo, tracking servo, and slide servo. That is, the focus servo controls the objective lens 32 by driving the actuator 31 so that the laser light is focused on the surface of the optical disc 1. The tracking servo controls the optical pickup 3 so as to follow the track of the optical disc 1. The slide servo controls the optical pickup to move to a predetermined position and keep the position.

  The laser power control unit 9 controls the output intensity of the laser light according to the laser output recorded in advance on the optical disc 1 or the laser output determined by OPC (Optimum Power Control). The laser driver 10 is a driver circuit that drives the laser 33. The laser driver 10 is controlled by the laser power control unit 9.

  The decoder 11 outputs a signal from the optical pickup 3 as an RF signal, a tracking error signal, a focus error signal, and the like. The encoder 14 generates data to be written on the optical disc 1.

  The control unit (microcomputer) 12 controls the operation of the optical disk device. For example, an OPC process for determining the intensity of the laser beam output from the laser 33 and a process for controlling the output of the laser beam during the recording operation are performed. The memory 13 stores a program executed by the control unit 12 and data necessary for executing the program.

  FIG. 2 is a functional block diagram of the servo control unit 8 of the present invention. In FIG. 2, the servo control unit 8 shows only the focus servo system. The servo control unit 8 performs tracking servo and slide servo in addition to the focus servo unit 80. In the following description, focus servo will be described, and the tracking servo and slide servo shall be controlled publicly or well-known.

  The servo control unit 8 in FIG. 2 inputs a focus error signal by the critical aberration method from the photodetector 4 that has received the reflected light from the optical disc 1, calculates the amount of focus shift, and the amount of shift and a predetermined gain. The focus servo unit 80 calculates a compensation value from (for example, feedback gain), outputs a drive signal value of the actuator 31 corresponding to the compensation value, drives the objective lens 32, and performs feedback control.

  Further, the servo control unit 8 learns a focus error signal in consideration of surface wobbling of the optical disc 1 in order to determine a control constant such as a gain of the focus servo unit 80 when the optical disc 1 is detected. An initialization unit 90 that determines the gain from the learning value is included.

  The configuration of the focus servo unit 80 includes a deviation detection unit 81 that receives a focus error signal from the light detector 4 to detect the focus state of the laser beam and detects the amount of defocus of the laser beam, The phase compensation unit 82 obtains a compensation value from a control constant including a predetermined gain by inputting a deviation amount, and a drive unit 83 that inputs a compensation value and outputs a drive signal value of the actuator 31.

  The initialization unit 90 determines a control constant in consideration of the amount of surface deflection of the optical disc 1 when the optical disc 1 is detected. The optical disk 1 is detected when the optical disk 1 is inserted by operating a tray (not shown) of the optical disk device. The deviation detection unit 81 also functions as a focus detection unit that detects the in-focus state.

  When the optical disc 1 is inserted, the initialization unit 90 sends a command to the drive unit 83 and the motor drive unit 6 so as to drive the objective lens 32 and the disc motor 2 with a predetermined drive pattern, and the laser 33 emits light. Commands the power control unit 9. Here, the drive pattern commanded by the initialization unit 90 includes, for example, a sweep operation that repeats an operation of bringing the objective lens 32 close to the optical disc 1 and then returning the objective lens 32 back to the optical pickup 3 in a predetermined cycle, and a predetermined operation of the disc motor 2. Drive at rotational frequency.

  The initialization unit 90 monitors the focus error signal and the position of the objective lens 32 during the period (initialization period) in which the objective lens 32 and the disk motor 2 are driven with the predetermined drive pattern, and the objective lens 32 is detected. When the position of is within a predetermined range, a focus error signal indicating the in-focus state is acquired as a learning value (a reference value for determining a control constant), and the amplitude value of this focus error signal (or the sum of the focus error signals) Control constants such as feedback gain are determined from the signal value). After the control constant is determined, the driving of the objective lens 32, the disk motor 2 and the laser 33 with a predetermined driving pattern is terminated, and the process shifts to reading / writing of the optical disk 1.

  For this reason, the initialization unit 90 includes an initialization drive unit 93 that instructs to drive the objective lens 32, the disk motor 2, and the laser 33 with a predetermined drive pattern, and an initialization period in which each unit is driven with a predetermined drive pattern. The focus error signal from the detector 4 and the drive signal from the drive unit 83 are monitored, and when the position of the objective lens 32 is within a predetermined range, a focus error signal indicating the in-focus state is acquired as a learning value. A learning unit 91 and a control constant setting unit 92 that calculates a focus servo control constant from the learning value acquired by the learning unit 91 and sets the control constant in the phase compensation unit 82 are provided.

  The initialization drive unit 93 sweeps the objective lens 32 beyond the standard range of the amount of surface blur of the optical disc 1. Then, the learning unit 91 monitors the drive signal value of the actuator 31 as the position of the objective lens 32. If the position of the objective lens 32 is within a predetermined range when the focus error signal is in a focused state, the learning unit 91 focuses. The error signal amplitude value (or sum signal value) is acquired as a learning value. The control constant setting unit 92 determines the control constant of the focus servo from the acquired learning value using a preset function or the like.

  FIG. 3 is a flowchart illustrating an example of control performed by the initialization unit 90 of the servo control unit 8.

  First, the initialization unit 90 instructs the motor drive unit 6 to drive the disk motor 2 at a predetermined rotation frequency in step S101. In step S102, the initialization unit 90 instructs the actuator 31 to perform a sweep operation at a predetermined cycle, and instructs the laser power control unit 9 to irradiate the laser 33. In step S103, the value of the counter N for counting the number of times in-focus state is reset to zero.

  Through steps S101 to S102, the optical disk 1 starts to rotate at a predetermined rotation frequency by the disk motor 2, and the position of the objective lens 32 is repeatedly brought into and out of contact with the optical disk 1 at a predetermined period. The focus error signal output from the photodetector 4 is brought into focus according to the position of the objective lens 32 and the surface blur of the optical disc 1.

  Next, in step S104, the initialization unit 90 determines whether or not the amplitude value (voltage) of the focus error signal has changed between 0 and the absolute value of the amplitude value has exceeded a predetermined threshold value Th1 and is in a focused state. Determine. When the focus error signal is in focus, the process proceeds to step S105, and when the focus error signal is not in focus, monitoring of the focus error signal is repeated.

  In step S105, the initialization unit 90 monitors the drive signal value of the actuator 31 as the position of the objective lens 32, and determines whether or not the position of the objective lens 32 is within a predetermined range. That is, the voltage of the drive signal is set to the drive signal value Vd, and the position of the objective lens 32 is within a predetermined range in the focus direction when the drive signal value Vd is not less than the first threshold Thv1 and not more than the second threshold Thv2. Judge that there is. Note that the threshold Thv1 <threshold Thv2 is set, and the relationship between the drive signal value Vd and the position of the objective lens 32 is, for example, that the objective lens 32 is closest to the optical disc 1 within a predetermined range when the drive signal value Vd = Thv2. When the drive signal value Vd = Thv1, the position of the objective lens 32 is the farthest position from the optical disc 1 within a predetermined range. Furthermore, the first threshold value Thv1 and the second threshold value Thv2 of the drive signal value Vd can be set as the standard range of the surface shake of the optical disc 1.

  In step S105, when it is determined that the position of the objective lens 32 is within the predetermined range, the process proceeds to step S106, and the amplitude value of the focus error signal acquired in step S104 is acquired as a learning value. Further, in step S107, a control constant such as a focus servo feedback gain is calculated and determined from the learned value using a predetermined function, and the initialization period is set by setting the control constant in the phase compensation unit 82 of the focus servo system. Exit. When the initialization period ends, the initialization drive unit 93 ends the sweep operation of the objective lens 32.

  On the other hand, if it is determined in step S105 that the drive signal value Vd is not within the predetermined range Thv1 to Thv2, the process proceeds to step S108, and a counter indicating the number of times the focus error signal is in focus. It is determined whether or not the value of N exceeds a predetermined threshold ThN. If the value of the counter N does not exceed the threshold value ThN, the process proceeds to step S109, the value of the counter N is incremented, and then the focus error signal monitoring in step S104 is repeated.

  On the other hand, when the value of the counter N exceeds the predetermined threshold value ThN, the process proceeds to step S110, where the initialization unit 90 compares the rotational frequency of the disk motor 2 and the sweep frequency of the objective lens 32 (rotational frequency / It is determined whether or not (sweep frequency) is not less than a predetermined threshold value ThR1 and not more than a threshold value ThR2. Note that the sweep frequency is the reciprocal of one cycle (sweep cycle) in which the objective lens 32 is moved closer to the optical disc 1 and then moved away from it. The threshold value ThR1 is set to 50%, for example, and the threshold value ThR2 is set to 200%, for example. Thereby, it is determined whether or not the region in which the rotation frequency and the sweep frequency are approximate, in other words, the state in which the focus position of the optical disc 1 is little changed.

  If it is determined in step S110 that the ratio between the rotation frequency and the sweep frequency is greater than or equal to the predetermined threshold ThR1 and less than or equal to the threshold ThR2, the process proceeds to step S111 because the change in the focus position of the optical disc 1 is small. , Change the phase of rotation frequency and sweep frequency. On the other hand, if it is determined that the ratio between the rotation frequency and the sweep frequency is less than the predetermined threshold ThR1, the process returns to step S104 to continue monitoring the focus error signal.

  In step S111, the sweep operation of the objective lens 32 is temporarily stopped, and the phase of the sweep frequency is shifted by a predetermined value (for example, 180 °). Next, the initialization unit 90 resets the value of the counter N in step S112 and returns to the focus error signal monitoring in step S104.

  With the above processing, when the focus error signal is in focus and the position of the objective lens 32 is within a predetermined range, the amplitude value of the focus error signal is acquired as a learning value, and the learning value is obtained from this learning value. Determine the control constant of the focus servo.

  On the other hand, if the position of the objective lens 32 is outside the predetermined range even if the number of times that the focus error signal is in focus exceeds the threshold ThN, the rotational frequency of the optical disc 1 and the sweep frequency of the objective lens 32 are approximate. The phase of the rotational frequency and the phase of the sweep frequency are relatively shifted so that the position of the objective lens 32 when the focus error signal is in focus and the state of the optical disc 1 are assumed. The relative position is changed, and the rotation period and the phase of the sweep frequency are controlled so that the focus error signal is in focus when the position of the objective lens 32 is within a predetermined range.

  4 to 6 are graphs showing how learning values are acquired under the control of the initialization unit 90. 4 to 6 show the position [μm] of the objective lens 32, the position [μm] of the optical disc 1, the relative speed [μm / sec] of the displacement of the surface of the optical disc 1 and the focus direction of the objective lens 32, respectively. It is a graph which shows the amplitude value [mV] of a focus error signal, the value [mV] of a sum signal, and time.

  FIG. 4 shows an example in which the sweep cycle of the objective lens 32 is extremely longer than the rotation cycle of the optical disc 1, and the ratio of the rotation frequency of the disc motor 2 to the sweep frequency of the objective lens 32 (rotation frequency / sweep frequency). Indicates a case where exceeds a predetermined threshold value ThR2. In this example, only a part of the sweep cycle of the objective lens 32 is shown, and the position of the objective lens 32 shows a case where the objective lens 32 moves away after being closest to the optical disc 1.

  The focus error signal is brought into focus at times T1 to T10 in the figure. From time T1 to time T6, the focus error signal is in focus. However, since the position of the objective lens 32 is not within a predetermined range (Thv2 and Thv1), the initialization unit 90 learns these focus error signals. It is not acquired as a value. In these in-focus states, the relative value of the displacement of the surface of the optical disc 1 and the displacement of the objective lens 32 is low, so the amplitude value of the focus error signal is low. If the control constant of the focus servo is determined with these low amplitude values, the focus servo system causes oscillation or the like as in the conventional example, and the followability of the focus servo is lowered.

  This relationship will be described with respect to times T1 and T2. In FIG. 4, the relative speeds at times T1 and T2 are closer to “0” than at other times. The sign of the relative speed changing to “+” or “−” across “0” indicates that the distance between the optical disc and the objective lens 32 reverses in the direction of contact / separation as time passes. This is because the focus error signal passes through the focal point without reaching the maximum or minimum at the portion where the sign of the relative speed is reversed.

  On the other hand, when the position of the objective lens 32 indicated at times T7 to T10 is within a predetermined range (Thv1 to Thv2), the relative speed between the optical disc 1 and the objective lens 32 when in focus is outside the predetermined range. The amplitude value of the focus error signal becomes the original size as the relative speed increases. The initialization unit 90 acquires the amplitude value of the focus error signal in the focused state at time T7 as a learning value. Therefore, since a focus error signal having a large amplitude value is obtained as a value for determining the control constant, the control constant of the focus servo system obtained from the learning value is stable even in the optical disc 1 whose surface blur exceeds the standard range. It will be a thing.

  In particular, by setting the first threshold value Thv1 and the second threshold value Thv2 of the drive signal value Vd to the standard range of the surface blur of the optical disc 1, the optical disc 1 whose surface blur exceeds the standard range, and the surface blur is within the standard range. The optical disk 1 can be handled equally, the control constant of the focus servo system can be stabilized, and the followability of the objective lens 32 in the focus direction can be ensured.

  In the above example, the focus error signal is used as the learning value. However, it is also possible to treat the sum signal of the photodetector 4 as the learning value and determine the control constant from the sum signal.

  FIG. 5 shows an example in which the sweep cycle of the objective lens 32 and the rotation cycle of the optical disc 1 are approximated, and the ratio (rotation frequency / sweep frequency) between the rotation frequency of the disc motor 2 and the sweep frequency of the objective lens 32 is shown. The case where the threshold value ThR1 is equal to or greater than the threshold value ThR2 is illustrated.

  In this example, the focus error signal is in focus at times T1 to T4. Here, if the threshold ThN = 3 in the flowchart of FIG. 3 above, the number of times the objective lens 32 is in focus outside the predetermined range at time T4 exceeds the threshold ThN = 3. The sweep operation is temporarily stopped and the sweep cycle is changed by 180 °. After the sweep cycle is changed, the position of the objective lens 32 is in focus within a predetermined range (Thv1 to Thv2) at time T6, and the initialization unit 90 sets the amplitude value of the focus error signal at time T6. Obtained as a learning value. The relative speed between the surface of the optical disk 1 and the objective lens 32 at time T6 is larger than when the position of the objective lens 32 is in a focused state outside the predetermined range, and the amplitude value of the focus error signal is also the original value. It becomes size. By determining the control constant of the focus servo from the learning value in which the amplitude value becomes the original size, the followability of the focus servo system can be improved, and even in the optical disc 1 whose surface blur exceeds the standard range, The control constant of the focus servo system obtained from the learning value is stable.

  FIG. 6 shows an example in which the sweep cycle of the objective lens 32 is extremely shorter than the rotation circumferential cycle of the optical disc 1, and the ratio of the rotation frequency of the disc motor 2 to the sweep frequency of the objective lens 32 (rotation frequency / sweep frequency). ) Is less than a predetermined threshold ThR1. In this example, only a part of the rotation period of the optical disc 1 is illustrated.

  The focus error signal is brought into focus at times T1 to T10 in the figure. From time T1 to T6, the focus error signal is in focus, but the position of the objective lens 32 is not within a predetermined range (the drive signal value is between Thv2 and Thv1). The focus error signal is not acquired as a learning value. In these in-focus states, the relative speed of the displacement speed of the surface of the optical disc 1 and the displacement speed of the objective lens 32 is relatively low, so the amplitude value of the focus error signal is smaller for the above reason. If the control constant of the focus servo is determined with these low amplitude values, the focus servo system may cause oscillation as in the conventional example.

  On the other hand, when the position of the objective lens 32 indicated at times T7 to T10 is within a predetermined range (Thv1 to Thv2), the relative speed between the optical disc 1 and the objective lens 32 when in focus is outside the predetermined range. The amplitude value of the focus error signal becomes the original size as the relative speed increases. The initialization unit 90 acquires the amplitude value of the focus error signal in the focused state at time T7 as a learning value. Therefore, since a focus error signal having a large amplitude value is obtained as a value for determining the control constant, the control constant of the focus servo system obtained from the learning value is stable even in the optical disc 1 whose surface blur exceeds the standard range. It will be a thing. In the above example, the focus error signal is used as a learning value, but the sum signal of the photodetector 4 can be handled as a learning value.

  As described above, in the present invention, the amplitude value of the focus error signal when the position of the objective lens 32 is within the predetermined range is used as a value for determining the control constant. Also in the optical disc 1, the focus error signal is acquired as a value for determining the control constant in a region where the relative speed of the surface of the optical disc 1 and the objective lens 32 in the focus direction is relatively high, so that the original amplitude value is obtained. Thus, the control constant can be determined by the focus error signal, and a stable focus servo can be realized even when the optical disc 1 whose surface blur is out of the standard range is used.

  In the above-described embodiment, the focus error signal when the position of the objective lens 32 is within the predetermined range is used. However, the focus error signal is generated a predetermined number of times after the position of the objective lens 32 is within the predetermined range. And the control constant may be determined from the average value of the amplitudes of the plurality of focus error signals, or the control constant may be determined from the value of the sum signal instead of the focus error signal. .

  In the above embodiment, the example in which the phase of the sweep cycle is changed when the phase of the rotation cycle of the optical disc 1 and the phase of the sweep cycle of the objective lens 32 are changed is shown. However, the rotation frequency of the disc motor 2 is temporarily changed. The phase of the rotation period of the optical disk 1 may be changed, and the phase of the sweep period of the objective lens 32 and the phase of the rotation period of the optical disk 1 may be changed relatively.

  In the above embodiment, the astigmatism method is used as the focus error signal. However, the present invention is not limited to this, and a known method such as the Foucault method or the spot size method can be appropriately selected.

  In the above embodiment, the configuration in which the control unit 12 and the servo control unit 8 are separated is shown. However, the control unit 12 may process the servo control unit 8.

  In the above embodiment, the example in which the learning unit 91 detects the focus has been described. However, the focus detection result of the deviation detection unit 81 may be transmitted to the learning unit 91.

  In the above embodiment, the drive signal of the actuator 31 is used as a value indicating the position of the objective lens 32. However, any other signal may be used as long as the position of the objective lens 32 in the focus direction can be grasped. May be.

  As described above, the present invention can provide an optical disk device capable of realizing stable focus servo even when using an optical disk whose surface deviation is outside the standard range.

DESCRIPTION OF SYMBOLS 1 Optical disk 4 Optical detector 8 Servo control part 31 Actuator 32 Objective lens 81 Deviation detection part 82 Phase compensation part 83 Drive part 90 Initialization part 91 Learning part 92 Control constant setting part 93 Initialization drive part

Claims (8)

A rotation control unit for controlling the rotation of the optical disc;
An objective lens for irradiating the optical disk with a beam from a laser;
An actuator that drives the objective lens to move the focal point of the beam applied to the optical disc in the focus direction;
An optical sensor that detects the beam reflected from the optical disc and outputs a detection signal;
In an optical disc apparatus comprising: a servo control unit that drives the actuator to control the focus of the beam from a detection signal of the optical sensor;
The servo control unit
A focus servo unit that inputs a detection signal of the optical sensor and drives the actuator so that the beam is in a focused state based on a predetermined control constant;
An initialization unit that inputs a detection signal of the optical sensor and determines the control constant;
The initialization unit includes:
An initialization drive unit that drives the optical disk at a predetermined rotation frequency to the rotation control unit and drives the actuator at a predetermined sweep frequency;
When the position of the objective lens is within a predetermined range when it is detected as a focused state from the detection signal from the optical sensor that the beam is connected at a predetermined position of the optical disc, the optical sensor A learning unit that obtains a detection signal from as a learning value for controlling the actuator;
A control constant setting unit for determining a control constant for driving the actuator from the acquired learning value;
An optical disk device comprising: The detection signal includes a focus error signal,
The optical disc apparatus according to claim 1, wherein the learning unit acquires the focus error signal as a learning value for controlling the actuator. The detection signal includes a sum signal and a focus error signal,
The in-focus detection unit is
When the sum signal exceeds a predetermined threshold and the focus error signal reaches a predetermined value, the in-focus state is determined,
The optical disc apparatus according to claim 1, wherein the learning unit acquires the sum signal as a learning value for controlling the actuator. The learning unit
When the focus detection unit detects the in-focus state, if the position of the objective lens is outside a predetermined range, the phase of the sweep frequency for driving the actuator and the phase of the rotation frequency for driving the optical disc The optical disk device according to claim 1, wherein the optical disk device is relatively changed. The learning unit
The phase of the sweep frequency for driving the actuator is changed when the position of the objective lens is outside a predetermined range when the focus detection unit detects the focus state. Item 5. The optical disk device according to Item 4. The learning unit
When the focus detection unit detects the in-focus state, if the position of the objective lens is out of a predetermined range, the phase of the rotation frequency for driving the optical disc is changed with respect to the rotation control unit. The optical disk apparatus according to claim 4, wherein a command to perform is transmitted. The learning unit
When the focus detection unit detects the in-focus state, the position of the objective lens is outside a predetermined range, and the ratio between the sweep frequency for driving the actuator and the rotation frequency for driving the optical disc The optical disk device according to claim 4, wherein the phase is relatively changed when is in a predetermined range. The initialization drive unit transmits a drive signal to the actuator,
The optical disk device according to claim 1, wherein the learning unit sets the driving signal as a position of the objective lens.

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