JP2006338827A - Optical disk apparatus, method for detecting position of optical disk apparatus, reproducing apparatus, and reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a reference position of an optical pickup against an optical disk without using exclusive parts such as a switch. <P>SOLUTION: The optical pickup 22 is moved from the outer peripheral side of the optical disk to the inner peripheral side and whether a focus error signal exceeds a threshold set for a reference level or not is discriminated. When the optical pickup 22 collides with the outer frame of a spindle motor 20, an objective lens 34 held by a suspension wire 94 is oscillated, the objective lens 34 is deviated from a just focus position and the focus error signal is increased/decreased from the reference level. When it is determined that the focus error signal exceeds the threshold, the collision of the optical pickup 22 with the outer frame of the spindle motor 20 is determined, the feeding operation of the optical pickup 22 is stopped and the stopped position is set as a reference position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus, an optical disc apparatus position detection method, a reproducing apparatus, and a reproducing method that can realize a mechanism for obtaining a reference position of an optical pickup with respect to a loaded optical disc with a smaller number of parts.

  In recent years, it has become common to use recordable optical disks as recording media for recording digital data. In the field of optical discs, a plurality of types of recordable optical discs having different physical characteristics while maintaining reproduction compatibility have been developed and put into practical use. These types of recordable optical discs are rapidly spreading because they have the same recording capacity as playback-only optical discs and are compatible with playback.

  As such recordable optical disks, there are CD-R (Compact Disc-Recordable) and CD-RW (Compact Disc-ReWritable), which conform to the CD (Compact Disc) standard, and the DVD (Digital Versatile Disc) standard. DVD-R (DVD Recordable), DVD + R (DVD + R format), DVD-RW (DVD Re-recordable), DVD + RW (DVD + RW format), and the like are widely known. The type conforming to the DVD standard is particularly popular because it has a large recording capacity of 4.7 GB (Giga Byte) or more.

  In such an optical disc, the physical addresses are assigned so as to increase from the inner circumference side toward the outer circumference side. Then, the management information of the disk and the data recorded on the disk, and the test writing area for adjusting the energy of the laser beam in the recordable disk are arranged from the innermost side of the disk.

  For example, in a read-only DVD, the innermost circumference of the disc is a lead-in area, and a reference code, information on the disc and data recorded on the disc, and the like are recorded. The outside of the reference code is a data area, and the outermost circumference is a lead-out area. In a recordable DVD (e.g., DVD-R), a PCA (Power Caribration Area) for performing test writing for laser power calibration at the time of recording and an RMA (Recording Information Management Area) are further provided on the inner peripheral side of the lead-in area ) And are arranged.

These areas need to be accessed first when the optical disk is loaded into the disk drive. For example, when a disk is loaded, the disk drive moves the optical pickup to the innermost circumferential position of the disk using a feed mechanism driven by a sled motor. Since the distance from the innermost circumferential position to the start position of the lead-in area is determined by the standard, if the optical pickup can be moved to the innermost circumferential position, the lead-in area can be accessed with reference to that position. Conventionally, the detection of the innermost peripheral position has been performed using dedicated components for position detection such as a switch, as described in Patent Document 1.
JP 2002-334451 A

  However, when a dedicated part such as a switch is provided for detecting the innermost peripheral position, there is a problem that it is difficult to reduce the cost of the apparatus. Further, conventionally, there has been a problem that there is no method for detecting the innermost circumferential position of the disk without using such a position detection switch.

  Accordingly, an object of the present invention is to provide an optical disc apparatus, an optical disc apparatus position detecting method, a reproducing apparatus and a reproducing method capable of detecting a reference position of an optical pickup with respect to an optical disc without using a dedicated component such as a switch. Is to provide.

  In order to solve the above-described problems, the present invention irradiates an optical disk with laser light, detects an reflected laser light reflected from the optical disk, and moves the optical pickup in the radial direction of the optical disk. A moving unit and a reference position detecting unit that detects a reference position in the radial direction of the optical pickup based on a change in reflected laser light detected by the moving optical pickup without tracking control by the moving unit; An optical disc apparatus characterized by the above.

  The present invention also includes a step of irradiating an optical disc with an optical pickup by an optical pickup and detecting reflected laser light reflected from the optical disc, a step of moving the optical pickup in the radial direction of the optical disc, And a reference position detecting step for detecting a reference position in the radial direction of the optical pickup based on a change in the reflected laser light detected by the moving optical pickup without performing tracking control by the step. This is a method for detecting the position of an optical disk device.

  The present invention also provides an optical pickup that irradiates an optical disc with laser light and detects reflected laser light reflected from the optical disc, a moving unit that moves the optical pickup in the radial direction of the optical disc, and a moving unit. A reference position detection unit that detects a reference position in the radial direction of the optical pickup based on a change in reflected laser light detected by the moving optical pickup without performing tracking control, and is moved from the reference position by the moving unit. A reproducing apparatus is characterized in that the optical pickup is moved to a predetermined position in the radial direction of the optical disc to start reproducing information recorded on the optical disc.

  The present invention also includes a step of irradiating an optical disc with an optical pickup by an optical pickup and detecting reflected laser light reflected from the optical disc, a step of moving the optical pickup in the radial direction of the optical disc, The step of detecting the reference position in the radial direction of the optical pickup based on the change of the reflected laser beam detected by the moving optical pickup without tracking control by the step, and the diameter of the optical disk from the reference position And reproducing the information recorded on the optical disk by moving the optical pickup to a predetermined position in the direction.

  As described above, the present invention irradiates an optical disk with laser light by an optical pickup, detects reflected laser light reflected from the optical disk, and moves in the radial direction of the optical disk without tracking control. Since the reference position in the radial direction of the optical pickup is detected based on the change in the reflected laser beam detected by the pickup, the reference position of the optical pickup in the radial direction of the optical disk is not used by a position detection dedicated component. Can be detected.

  Also, the present invention detects the reflected laser beam reflected from the optical disc by irradiating the optical disc with the optical disc by the optical pickup, and detects it by the optical pickup moving in the radial direction of the optical disc without tracking control. The reference position in the radial direction of the optical pickup is detected based on the change in the reflected laser beam, and the reproduction of the information recorded on the optical disk is started by moving the optical pickup from the reference position to a predetermined position in the radial direction of the optical disk. Therefore, the process of detecting the reference position of the optical pickup with respect to the radial direction of the optical disk and moving the optical pickup to a predetermined position can be performed without using a position detection dedicated component.

  In the present invention, a laser beam is irradiated onto an optical disk by an optical pickup, and a reflected laser beam reflected from the optical disk is detected. The optical pickup is detected by an optical pickup moving in the radial direction of the optical disk without performing tracking control. Since the reference position in the radial direction of the optical pickup is detected based on the change of the reflected laser beam, no dedicated parts are required to detect the reference position of the optical pickup in the radial direction of the optical disk, which reduces the cost. There is an effect that can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, for easy understanding, a system applicable to the embodiment of the present invention will be described. FIG. 1 shows an example of the configuration of an optical disc drive 1 applicable to the embodiment of the present invention. The optical disk 10 is engaged with the shaft 21 of the spindle motor 20 by a clamp mechanism (not shown) and can be driven to rotate by the spindle motor 20.

  An optical pickup 22 is disposed at a position facing the recording surface of the optical disc 10. The optical pickup 22 is placed on a sled 24 that can be moved in the radial direction of the optical disc 10 by a sled motor 23, and is moved in the radial direction of the optical disc 10 by a feeding mechanism that includes the sled motor 23 and the sled 24. .

  The optical pickup 10 includes a laser light source, a beam splitter, a grating, a photodetector, an objective lens, and the like. The laser light emitted from the laser light source is divided into a main beam and two side beams by the grating into three parts. Passes and enters the objective lens. The objective lens irradiates the recording film of the optical disc 10 with the incident main beam and two side beams. The laser light is reflected by the recording film of the optical disc 10, is incident on the beam splitter via the objective lens, is reflected by the beam splitter, and reaches the photodetector. The photodetector takes out and outputs push-pull signals of the main beam and the two side beams.

  The output of the optical pickup 22 is supplied to the signal processing unit 25. The signal processing unit 25 generates a focus error signal, a tracking error signal, and the like based on the output of the optical pickup 22 and supplies them to the microcomputer 27. The microcomputer 27 supplies a control signal to the servo control unit 28 based on these focus error signal and tracking error signal. The servo control unit 28 performs various servo controls such as spindle servo, thread servo, and servo (focus servo, tracking servo) for the objective lens based on the supplied control signal.

  In recording, the signal processing unit 25 performs error correction encoding processing and recording encoding processing on the recording data supplied via the host interface (I / F) 26, and further performs predetermined processing such as modulation processing. The signal processing is performed to generate a recording signal. The recording signal is supplied to the optical pickup 22 and is modulated and driven by a laser beam. During reproduction, the signal output from the optical pickup 22 is subjected to predetermined processing such as RF signal processing, binarization processing, PLL (Phase Locked Loop) synchronization processing, and recording code decoding processing, and digital data is extracted. . The digital data output from the signal processing unit 25 is output to an external device via the host I / F 26.

  Further, for example, at the time of recording, a recording command is also supplied via the host I / F 26 and passed to the microcomputer 27. The microcomputer 27 issues a command to start the recording operation to the servo control unit 28 based on the recording command. The servo control unit 28 controls the position of the optical pickup 22 based on the command from the microcomputer 27. Further, the microcomputer 27 sets recording conditions such as a write strategy, a recording power, and a defocus amount for the signal processing unit 25. The signal processing unit 25 performs modulation of the recording signal and drive control of the laser light source 30 according to the set recording conditions. Similarly, during reproduction, the signal processing unit 25 and the servo control unit 28 are controlled by the microcomputer 27.

  The microcomputer 27 is composed of, for example, a microprocessor, and controls the operation of the optical disc drive 1 as described above based on a program stored in advance in a ROM (Read Only Memory) (not shown). Note that it is preferable to use a ROM capable of rewriting data such as EEPROM (Electrically Erasable Programmable Read Only Memory) because the program stored in the ROM can be updated. The program data to be updated is supplied from the host I / F 26, for example.

  FIG. 2 conceptually shows an example optical path in the optical pickup 22. For example, laser light emitted from a laser light source 30 made of a laser diode is split into a main beam made of zero-order light and two side beams made of primary light by a grating 31, and a collimator lens via a beam splitter 32. 33 is incident. The laser light is converted into parallel light by the collimator lens 33, converged by the objective lens 34, and irradiated onto the recording surface of the optical disk 10. The laser light is reflected by the recording surface of the optical disc 10 and is incident on the beam splitter 32 via the objective lens 34 and the collimator lens 33. The reflected laser beam is reflected by the beam splitter 32 in a predetermined manner and is incident on the photodetector 40 through the cylindrical lens 35.

  FIG. 3 shows the appearance of an example of the objective lens 34 and an actuator that drives the objective lens 34. FIG. 3 shows an example of an actuator based on a wire drive system. The fixing portions 90A and 90B are fixed to the thread 61. Magnets 91A and 91B are attached to the fixing portions 90A and 90B, respectively. The objective lens 34 is supported on the fixed portion 90B by only four suspension wires 94, 94, 94, 94 (one of the four is not shown in FIG. 3). That is, the objective lens 34 is supported by the four suspension wires 94, 94, 94, 94 in a state of floating in the air. Therefore, the objective lens 34 can be easily moved up and down and left and right.

  A tracking coil 92 and a focus coil 93 are provided on the objective lens 34. The four suspension wires are connected, for example, in pairs of two so that current flows through the focus coil 92 and the tracking coil 93, respectively. By causing a current to flow through the suspension wires 94, 94, 94, 94, electromagnetic induction is generated in the focus coil 92 and the tracking coil 93, and the objective lens 34 can be moved vertically and horizontally by the magnetic force of the magnets 91A and 91B. .

  The structure of the actuator that drives the objective lens 34 is not limited to the above-described example, but the point that the objective lens 34 is supported so as to be movable up and down and left and right for control of focus and tracking is also the case with other structures. It is common.

  FIG. 4 schematically shows an exemplary structure of the recording layer of the optical disc 10. In the recording layer, grooves 70, 70,... Meandering at a predetermined frequency are formed as guide grooves for guiding a laser beam for recording to the track. A land 71 is formed between the groove 70 and the groove 70. In the DVD-R standard and the DVD-RW standard, the address information is indicated by a prepit (not shown) formed on the land 71, and in the DVD + R standard and the DVD + RW standard, the address information is indicated by a high frequency (not shown) superimposed on the wobble. Indicated.

  Data is recorded by forming a recording mark 72 on the groove 70 by laser light guided to the track by the groove 70. In rewritable optical discs such as the DVD-RW standard and the DVD + RW standard, the recording layer is constituted by a phase change film, and a reversible change between the crystalline and amorphous materials of the phase change film is used to make a recording mark. 72 can be formed and the formed recording mark 72 can be erased. The change of the phase change film is controlled by switching the emission intensity of the laser light to a predetermined value. By forming a new recording mark 72 immediately after erasing the recording mark 72, data can be overwritten and recorded.

  Next, a first embodiment of the present invention will be described. In the first embodiment of the present invention, the reference position of the optical pickup 22 is obtained using a focus error signal based on the output of the optical pickup 22.

  The focus error signal will be schematically described. In order to read information recorded on the recording film of the optical disc 10, it is necessary to perform a focusing operation in which the focused laser beam irradiated from the optical pickup 22 is focused on the recording film of the optical disc 10. In the focus operation, for example, the focus is adjusted by moving the position of the objective lens 34 with respect to the laser light source 30 in the optical axis direction.

  The focusing operation is performed based on a change in the amount of received laser light by the photodetector 40 in accordance with the distance between the objective lens 34 of the optical pickup 22 and the optical disk 10. For example, by using a known technique such as an astigmatism method using a cylindrical lens 35 and a quadrant detector, the actuator is moved up and down, for example, while the focus servo loop is initially turned off. A focus error signal having an S-shaped curve is detected by displacing 34 in the optical axis direction, and a zero-cross point of the focus error signal is searched. When the zero cross point is found, the actuator moves up and down, and the focus servo loop is turned on to apply focus servo.

  First, detection of the focus error signal will be schematically described with reference to FIGS. The reflected laser beam reflected by the optical disk 10 is reflected by the beam splitter 32 and received by the photodetector 40 via the cylindrical lens 35, as schematically shown in FIG.

  As is well known, the cylindrical lens 35 has a lens action only in one direction of the light beam (y direction in the example of 4). Therefore, although the concentrating point narrowed by the cylindrical lens 35 is generated at the point B, the converging point is not a point but a straight line in the y direction (actually an ellipse extending in the y direction). After passing the point B, the luminous flux in the x direction spreads, and at the point j, the converging point becomes circular in line with the spread in the y direction. Thereafter, only the light beam in the y direction converges and converges at a point A on a straight line in the x direction (an ellipse extending in the x direction).

  6 to 8 schematically show how the laser light is received by the photodetector 40 through the cylindrical lens 35 as described above. 6 to 8, for convenience, the light receiving surfaces divided into four parts of the photodetector 40 are the light receiving surface A, the light receiving surface B, the light receiving surface C, and the light receiving surface D, respectively. It is assumed that the direction formed by C matches.

  FIG. 6 shows an example in which the objective lens 34 is in the in-focus position with respect to the recording film of the optical disc 10. In FIG. 6A and similar figures to be described later, the grating 31, the collimator lens 33, and the cylindrical lens 35 are omitted in the configuration of the optical pickup 22.

  When the objective lens 34 is in the in-focus position, the optical path of the laser light is as schematically shown in FIG. 6A, and the laser light is received by the photodetector 40 at the point j in FIG. As a result, on the light receiving surface of the photodetector 40, as shown in an example in FIG. 6B, a circular spot 40A is formed to receive the laser light.

In the astigmatism method, detection outputs from the light receiving surfaces A to D of the photodetector 40 divided into four parts are used, respectively, and based on the differential output D _PP between the light receiving surfaces in the diagonal direction, as shown in Equation (1). Determine the in-focus position.
D _PP = (A + C) − (B + D) (1)
In other words, when in-focus position, as shown in Figure 6B, the laser beam forms a circular spot 40A at the light receiving surface of the photodetector 40, the value 0 of the differential output D _PP, the photodetector 40 The output is substantially constant at the reference level.

FIG. 7 shows an example in which the objective lens 34 moves from the in-focus position toward the optical disc 10 and the objective lens 34 comes closer to the recording film of the optical disc 10 than the in-focus position. In this case, the optical path of the laser beam is as schematically shown in FIG. 7A, and the laser beam is received by the photodetector 40 in the state of point B in FIG. As a result, on the light receiving surface of the photodetector 40, as shown in FIG. 7B, an elliptical spot 40A in which the laser light extends in the y direction, that is, the direction formed by the light receiving surfaces B and D is formed. Therefore, the differential output D _PP becomes a negative value based on the above-described equation (1), and the output of the photodetector 40 decreases below the reference level.

FIG. 8 shows an example in which the objective lens 34 moves from the in-focus position to the side opposite to the optical disc 10 and the objective lens 34 moves away from the in-focus position with respect to the recording film of the optical disc 10. In this case, the optical path of the laser light is as schematically shown in FIG. 8A, and the laser light is received by the photodetector 40 at the point A in FIG. As a result, on the light receiving surface of the photodetector 40, as shown in FIG. 8B, an elliptical spot 40A in which the laser light extends in the x direction, that is, the direction formed by the light receiving surfaces A and C is formed. Therefore, the differential output D _PP becomes a positive value based on the above equation (1), and the output of the photodetector 40 increases from the reference level.

During focusing operation, for example, while moving to a predetermined objective lens 34 in the optical axis direction by an actuator seeing a change in the differential output D _PP value, it detects a zero-cross point of the differential output D _PP value, if The focus position. FIG. 9 shows a change in an example of the differential output _DPP, that is, the focus error signal when the position of the objective lens 34 is moved. As described above, the focus error signal has positive and negative peaks at positions closer to and far from the optical disc 10 than the in-focus position, and changes linearly with respect to the focus deviation between the positive and negative peaks. Draw. By detecting the zero cross point between the positive and negative peaks in this focus error signal, the just focus position can be obtained.

  As described above, the objective lens 34 is supported by the four suspension wires 94, 94, 94, 94 in a state of floating in the air. For this reason, when the optical pickup 22 collides with any member or the like while being moved by the feeding mechanism, the objective lens 34 is swung. As shown in FIG. 9, since the potential of the focus error signal changes sharply with respect to the shift from the just focus position, the timing at which the optical pickup 22 collides is detected based on the change in the potential of the focus error signal. Can do. The innermost peripheral position of the optical disk 10 can be obtained with reference to the position where the optical pickup 22 collides with a predetermined member.

  This will be described in more detail with reference to FIGS. FIG. 10 is a flowchart showing an example of processing from when the optical disc drive 1 is started until the recording or reproduction standby state is entered. For example, when a drive reset command is supplied from the host via the host I / F 26 (step S10), in response to the drive reset command, initialization processing of the optical disc drive 1 is started in step S11. The initialization process is not limited to this, and may be started, for example, when the optical disk 10 is loaded in the optical disk drive 1. In the initialization process, for example, each circuit constituting the optical disc drive 1 is reset.

  When the initialization process is completed, the process proceeds to step S12. Whether or not the process has been normally completed with the optical pickup 22 in a predetermined position before the drive reset command in step S10 is issued. To be judged. The predetermined position indicates, for example, the start position of the recording area. If it is determined that the operation has not been completed normally at the predetermined position, the position of the optical pickup 22 needs to be initialized, and the process proceeds to step S13.

  For example, when the operation by the optical disk drive 1 is terminated by a method assumed as a normal operation of the apparatus, such as a stop operation for the apparatus in which the optical disk drive 1 is incorporated or a power OFF by a power switch operation, The optical disc drive 1 is controlled to turn on the power after the optical pickup 22 is always moved to a predetermined position. Then, information at the end is stored in, for example, a memory included in the microcomputer 27.

  As an example, when a playback or recording operation stop operation or a power OFF operation is performed on a device in which the optical disc drive 1 is incorporated, a command indicating that is sent from the CPU of the device via the host I / F 26. It is supplied to the microcomputer 27. The microcomputer 27 moves the optical pickup 22 to a predetermined position based on this command, and stores information indicating that the operation has been normally completed in a nonvolatile memory or the like.

  On the other hand, when the power cord is pulled out during the operation of the apparatus or when the battery for supplying the power for driving the apparatus is removed, the process ends exceptionally. At this time, the operation at the end of the optical disk drive 1 does not depend on the control of the microcomputer 27, the optical pickup 22 is not moved, and the information at the end is not stored in the memory.

  In this manner, the microcomputer 27 can determine whether or not the previous termination has been normally performed based on the information stored in the memory.

  In step S13, a process of temporarily moving the optical pickup 22 to a reference position and then moving the optical pickup 22 to a predetermined position is performed. Although the details will be described later, the reference position is detected based on a change in the reflected laser light reflected from the recording film by the laser light emitted from the optical pickup 22 to the recording film of the optical disc 10. Further, the movement at this time is performed in a state where tracking control is not performed. If the optical pickup 22 is moved to a predetermined position in step S13, the process proceeds to step S14.

  In step S14, it is detected whether or not the optical disc 10 has been recorded. If the optical disc 10 is a disc that has been recorded in the past, the optical pickup 22 is moved to the end position of the recorded area, and a recording or reproduction waiting state is entered.

  On the other hand, if it is determined in step S12 that the process ended at the predetermined position last time, the operation can be started at the current position of the optical pickup 22, so the process proceeds to step S14.

  That is, the position where the management information for managing the recording area on the optical disc 10 is recorded is determined in advance. Therefore, it is possible to move the optical pickup 22 from a predetermined position to a position where the management information is recorded, and read the management information to determine whether or not the optical disc 10 has been recorded. If the management information is unrecorded, there is no data to be reproduced on the optical disc 10, and the recording wait state is entered. On the other hand, if it is recorded in the management information that the optical disk 10 has been recorded, information on the recorded data is acquired and the reproduction wait state is obtained, or information on an unrecorded area is acquired and the recording is waited for. State.

  In step S12 described above, the predetermined position of the optical pickup 22 has been described as the start position of the recording area, but this is not limited to this example. That is, the predetermined position may be anywhere within the movable range of the optical pickup 22 as long as the position is determined in advance.

  FIG. 11 is a flowchart showing an example of processing according to the first embodiment in which the optical pickup 22 is moved to the predetermined position in step S13 described above. Prior to the processing of this flowchart, the focusing operation of the optical pickup 22 is performed. For example, the optical pickup 22 is sent to an appropriate position where the recording film is formed on the optical disc 10 to perform a focusing operation.

  In the first step S20, the microcomputer 27 moves the optical pickup 22 toward the inner peripheral side of the optical disk 10, for example, by the feeding mechanism. In step S21, the signal processing unit 25 detects a focus error (FE) signal based on the output of the optical pickup 22, determines whether or not the level of the focus error signal exceeds a threshold value, and uses the determination result as a threshold determination signal. Output. The threshold discrimination signal is supplied to the microcomputer 27.

In the next step S22, the microcomputer 27 determines whether or not the level of the focus error signal exceeds the threshold value _Fth based on the threshold value determination signal supplied from the signal processing unit 25. If it is determined that it has not exceeded, the process returns to step S20, and the feeding operation of the optical pickup 22 by the feeding mechanism and the detection of the focus error signal are continued.

On the other hand, if it is determined in step S22 that the level of the focus error signal has _{exceeded the} threshold value _Fth , the process proceeds to the next step S23, and the feeding operation of the optical pickup 22 by the feeding mechanism is stopped.

  The operation from step S20 to step S23 will be described more specifically with reference to FIG. In step S20, when the optical pickup 22 is moved toward the inner circumference side of the optical disc 10 by the feeding mechanism, the optical pickup 22 is moved to the inner circumference of the optical disc 10 in the optical disc drive 1 as shown in FIG. 12A. It collides with the member provided on the side. In the example of FIG. 12A, the optical pickup 22 collides with the outer shell of the spindle motor 20. In addition, the position where the optical pickup 22 is caused to collide with the member is desirably on the inner peripheral side with respect to a PCA (Power Caribration Area) in a DVD-R standard disc, for example.

  When the optical pickup 22 collides with the outer shell of the spindle motor 20, the objective lens 34 supported by the suspension wires 94, 94,... It will shift. Therefore, the focus error signal fluctuates as shown in FIG. 12B according to the swing.

The signal processing unit 25 determines whether or not the level of the focus error signal exceeds a preset threshold F while the optical pickup 22 is moved by the feeding mechanism (step S21). For example, when the threshold is a value F _th relative to the reference level when the reference level of the focus error signal is 0, in the example of FIG. 12B, (reference level + threshold F _th ) becomes the threshold F _th (+). , (Reference level−threshold value F _th ) becomes the threshold value F _th (−). That is, the absolute value of a value obtained by subtracting the reference level from the focus error signal is greater than or equal to a threshold F _th.

The determination result by the signal processing unit 25 in step S21 is supplied to the microcomputer 27 as a threshold determination signal for the focus error signal. When the absolute value of the value obtained by subtracting the reference level from the level of the focus error signal exceeds the threshold value F _th , it can be determined that the optical pickup 22 has collided with the outer shell of the spindle motor 20. Therefore, when the microcomputer 27 determines that the absolute value of the value obtained by subtracting the reference level from the focus error signal exceeds the threshold F _th based on the threshold determination signal, the feeding operation of the optical pickup 22 by the feeding mechanism is stopped in step S23. The

  When the feeding operation is stopped in step S23, the optical pickup 22 is moved by a predetermined distance by the feeding mechanism with reference to the position where the operation is stopped in the next step S24. For example, since the positions of the lead-in area and the recording information management area (RMA) of the optical disc 10 are determined according to the standards, the optical pickup 22 is first moved from the position where the operation is stopped to these positions to read the information, Based on the read information, the optical pickup 22 is moved to a predetermined position, for example, the start position of the recording area.

  The member that collides when the optical pickup 22 is moved to the inner peripheral side of the optical disk 10 is not limited to the outer shell of the spindle motor 20. For example, the optical pickup 22 can be moved by a feeding mechanism so as to collide with the shaft 21 attached to the spindle motor 20. Further, a dedicated member for position detection may be provided.

  Further, whether the loaded optical disk 10 is a ROM type, a write-once type, or a rewritable type can be determined based on, for example, the amount of reflected laser light with respect to the recording film of the optical disk 10.

  As described above, in the first embodiment of the present invention, the innermost peripheral position of the optical disc 10 of the optical pickup 22 is obtained by detecting the fluctuation of the focus error signal. There is no need to provide a new member.

  Further, when the optical pickup 22 detects a collision with a member provided on the inner peripheral side of the optical disc 10, the feeding operation by the feeding mechanism can be stopped immediately after the optical pickup 22 cannot be moved by the feeding mechanism. . Without this mechanism, the sled motor 23 that drives the feed mechanism rotates only as specified. Therefore, even if the optical pickup 22 collides with a reference member on the inner peripheral side, the rotation continues and generates abnormal noise. End up. According to the first embodiment of the present invention, such an abnormal noise can be prevented without providing a dedicated member for detecting the reference position.

In the above description, the reference position for obtaining the innermost peripheral position of the optical disc 10 is provided on the inner peripheral side of the optical disc 10. However, this is not limited to this example, and the reference position is provided on the outer peripheral side of the optical disc 10. You may do it. For example, as shown in FIG. 13, the optical pickup 22 is fed toward the outer peripheral side of the optical disc 10 by the feeding mechanism, and collides with a member 50 provided on the outer peripheral side of the optical disc 10. The optical pickup 22 is sent to the outer peripheral side by the feeding mechanism, the focus error signal is monitored, and if it is detected that the absolute value of the value obtained by subtracting the reference level from the focus error signal exceeds the threshold value _Fth , the optical pickup 22 by the feeding mechanism. Is stopped and the stop position is set as the reference position.

  Next, a second embodiment of the present invention will be described. In the second embodiment of the present invention, the reference position of the optical pickup 22 is obtained using a tracking error signal based on the output of the optical pickup 22.

  The tracking error signal will be schematically described. In order to write data to the optical disc 10 or read data from the optical disc 10, it is necessary to accurately obtain the position of the track on the optical disc 10. For example, in the case of a recordable type disc, tracking is performed by detecting a tracking error signal using a groove provided in advance on the disc to obtain a track position. A DPP (Differential Push-Pull) method is often used for detecting the tracking error signal.

  In the DPP method, as shown in an example in FIG. 14, laser light emitted from a laser light source 30 is converted into zero-order light (main beam 60) and two primary lights (side beams 61 </ b> A and 61 </ b> B) using a grating 31. The three divided beams are arranged so that the two side beams 61A and 61B are positioned on the lands 71A and 71B adjacent to the groove 70 when the main beam is on the groove 70, respectively. To do. Then, the reflected light from the optical disk 10 by each beam is detected by each of the two two-split optical detectors constituting the photodetector 40 to obtain a push-pull signal, and a predetermined calculation is performed based on the push-pull signal. Get a tracking error signal.

  FIG. 15 shows a basic configuration of a photodetector 40 applicable to the DPP method. The photodetector 40 has a four-divided shape including a four-divided element A to D at the center and a two-divided shape including two-divided elements E and F and two-divided elements G and H on both sides.

The reflected light of the main beam 60 is received by the four-divided elements A to D, and the push-pull signal mpp of the main beam 60 is obtained from the difference between the amount of light received by the elements A and D and the amount of light received by the elements B and C. This central element is divided into four because it also detects the focus error signal described above. Further, for example, the reflected light of the side beam 61A is received by the two-divided elements E and F, and the push-pull signal spp ₁ of the side beam 61A is obtained from the difference between the received light amounts of the elements E and F. Similarly, for example, the reflected light of the side beam 61B is received by the two-divided elements G and H, and the push-pull signal spp ₂ of the side beam 61B is obtained from the difference between the received light amounts of the elements G and H.

The differential signal D _PP obtained based on the output of the photodetector 40 is obtained by the following equation (2) when the output signals from the elements A to H are represented as A to H, respectively.
D _PP = (A + D) − (B + C) −α × {(E−F) + (G−H)} (2)
The coefficient α is a DPP gain determined by the side beam light amount, the gain of the photodetector 40, and the like.

According to this equation (2), when the main beam 60 accurately captures the groove 70 and the laser beam (main beam 60) accurately tracks the track, the differential signal _DPP has a value of approximately zero. Take. Similarly, when the main beam 60 and the side beams 61A and 61B are irradiated, for example, on a portion of the recording film where the track or groove is not formed, the recording film for laser light is applied to the light receiving surfaces A to H of the photodetector 40. Therefore, the differential signal _DPP becomes substantially zero, and the output of the photodetector 40 becomes substantially constant at the reference level.

On the other hand, the differential signal D _PP has a value corresponding to the magnitude of the deviation when the laser beam is deviated from the track, and has a positive or negative value depending on the direction of the deviation. The output of 40 increases or decreases around the reference level.

  In the second embodiment of the present invention, based on the change of the tracking error signal according to the state of the recording film when the optical pickup 22 is moved in the radial direction of the optical disk 10 by the feeding mechanism, the optical pickup 22 Find the reference position.

  FIG. 16 is a flowchart showing an example of processing according to the second embodiment in which the optical pickup 22 is moved to the predetermined position in step S13 described above. Note that the schematic operation after the optical disk drive 1 is started is the same as the operation described with reference to FIG. Prior to the processing of this flowchart, the focusing operation of the optical pickup 22 is performed. For example, the optical pickup 22 is sent to an appropriate position where the recording film is formed on the optical disc 10 to perform a focusing operation.

  The microcomputer 27 moves the optical pickup 22 toward, for example, the inner peripheral side of the optical disc 10 by the feeding mechanism (step S30). In step S31, the signal processing unit 25 detects a tracking error signal based on the output of the optical pickup 22, determines whether the level of the tracking error signal exceeds a threshold value, and outputs the determination result as a threshold value determination signal. The threshold discrimination signal is supplied to the microcomputer 27.

  In the next step S32, the microcomputer 27 determines whether or not the level of the tracking error signal exceeds the threshold value within a predetermined time based on the threshold value determination signal supplied from the signal processing unit 25. If it is determined that it has exceeded, the process returns to step S30, and the feeding operation of the optical pickup 22 by the feeding mechanism and the detection of the tracking error signal are continued.

  On the other hand, if it is determined in step S32 that the level of the tracking error signal has not exceeded the threshold value within a predetermined time, the process proceeds to the next step S33, and the feeding operation of the optical pickup 22 by the feeding mechanism is stopped.

  The operation from step S30 to step S33 will be described more specifically with reference to FIG. In step S30, when the optical pickup 22 is moved toward the inner peripheral side of the optical disc 10 by the feeding mechanism, the laser light emitted from the optical pickup 22 is emitted from the optical disc 10 as shown in FIG. 17A. The optical disk 10 is irradiated with the tracks or grooves 73 formed on the recording film 10 </ b> A straddling the radial direction of the optical disk 10.

  For this reason, there are a state in which tracking can be considered because the track or groove 73 is irradiated with laser light, and a state where tracking is not possible because the track or groove 73 is not irradiated with laser light. It will be repeated alternately. As a result, the tracking error signal periodically increases and decreases with respect to the reference level, as shown in an example in the period A in FIG. 17B.

  On the other hand, when the irradiation position of the laser light reaches an area where the track or groove 73 is not formed, the reflected laser light is received by the respective light receiving surfaces of the photodetector 40 with substantially the same amount of light. As shown in FIG. 1, the tracking error signal is maintained at the reference level.

  Therefore, for example, a threshold that can detect the level of the tracking error signal when tracking is not achieved is set with respect to the reference level of the tracking error signal, and whether or not the tracking error signal exceeds this threshold within a predetermined time. Determine whether. If the level of the tracking error signal does not exceed this threshold value within a predetermined time while the optical pickup 22 is being sent by the feeding mechanism, the tracking error signal is in the state of period B in FIG. It can be determined that the region irradiated with light is a region where no track or groove exists in the optical disc 10.

For example, the threshold value is a value T _th with respect to the reference level when the reference level of the tracking error signal is 0. In the case of FIG. 17B, (reference level + threshold value T _th ) is the threshold value T _th (+), and (reference level−threshold value T _th ) is the threshold value T _th (−). That is, it is determined whether or not the absolute value of the value obtained by subtracting the reference level from the tracking error signal exceeds the threshold value _Tth . Further, the predetermined time can correspond to, for example, a cycle in which the laser beam straddles the track or the groove at the feeding speed by the feeding mechanism.

The signal processing unit 25 determines whether or not the absolute value of the value obtained by subtracting the reference level from the level of the tracking error signal exceeds a preset threshold value T _th while the optical pickup 22 is moved by the feeding mechanism. (Step S31). The determination result is supplied to the microcomputer 27 as a threshold determination signal for the tracking error signal.

When the absolute value of the value obtained by subtracting the reference level from the level of the tracking error signal exceeds the threshold T _th within a predetermined time, the laser light emitted from the optical pickup 22 forms a track or groove in the optical disc 10. It can be determined that the region is irradiated. On the other hand, when the absolute value of the value obtained by subtracting the reference level from the level of the tracking error signal does not exceed the threshold value T _th for a predetermined time or longer, the track or groove in the optical disk 10 is formed in the laser light emitted from the optical pickup 22. It can be determined that the region that has not been irradiated is irradiated.

Therefore, if the microcomputer 27 determines that the absolute value of the value obtained by subtracting the reference level from the level of the tracking error signal does not exceed the threshold T _th for a predetermined time or more based on the threshold determination signal, in step S33, the light emitted from the feeding mechanism is detected. The feeding operation of the pickup 22 is stopped. When the feeding operation is stopped in step S33, in the next step S34, the optical pickup 22 is moved by a predetermined distance by the feeding mechanism with reference to the position where the operation is stopped.

  When the optical pickup 22 is moved toward the inner peripheral side of the optical disc 10, the position where the feeding operation of the optical pickup 22 is stopped in step S33 is, for example, a lead when the optical disc 10 is a ROM type disc. It is the beginning of the in area. When the optical disc 10 is a disc according to the DVD-R standard or the DVD-RW standard, the position where the feeding operation of the optical pickup 22 is stopped in step S33 is, for example, the head of the PCA, and this position is used as a reference. The lead-in area can be accessed.

  In the above description, the optical pickup 22 is moved from the outer peripheral side to the inner peripheral side of the optical disc 10 to detect the reference position. However, the application example of the second embodiment of the present invention is not limited to this. It is not limited to examples. That is, the second embodiment of the present invention is similarly applied when the optical pickup 22 is moved from the inner circumference side to the outer circumference side of the optical disc 10 as shown in FIG. be able to. In this case, the feeding operation of the optical pickup 22 is stopped at the outer edge portion of the lead-out area for both ROM type and recordable type discs.

  Thus, by detecting a change in the tracking error signal accompanying the movement of the optical pickup 22, the predetermined position on the optical disc 10 can be directly obtained as the reference position of the reference position of the optical pickup 22.

  In the above description, the reference position of the optical pickup 22 is obtained using the change of the focus signal or the tracking signal, but this is not limited to this example. For example, the reference position of the optical pickup 22 can be obtained based on the amount of reflected light from the optical disk 10 of the laser light emitted from the optical pickup 22. In the recording film, in the area where the track or groove is formed, the amount of reflected light is smaller than the area where the track or groove is not formed. Accordingly, by detecting the change in the amount of reflected light when the optical pickup 22 is moved toward the inner periphery or the outer periphery of the optical disc 10, the reference position is obtained in the same manner as in the second embodiment described above. be able to.

It is a block diagram which shows a structure of an example of the optical disk drive applicable to embodiment of this invention. It is a basic diagram which shows notionally the optical path of an example in an optical pick-up. It is an external view of an example of the actuator which drives an objective lens and an objective lens. It is a basic diagram which shows roughly the structure of an example of the recording layer of an optical disk. It is a basic diagram which shows an example light beam by a cylindrical lens. It is a schematic diagram which shows typically a mode that the laser beam was received by the photodetector through the cylindrical lens. It is a schematic diagram which shows typically a mode that the laser beam was received by the photodetector through the cylindrical lens. It is a schematic diagram which shows typically a mode that the laser beam was received by the photodetector through the cylindrical lens. It is a basic diagram which shows a change of an example of a focus error signal when the position of an objective lens is moved. 10 is a flowchart showing an example of processing from when the optical disk drive is activated until a recording or reproduction standby state is entered. It is a flowchart which shows an example of the process which moves an optical pick-up to the predetermined position by the 1st Embodiment of invention. It is a figure for demonstrating the relationship between the movement of an optical pick-up, and a focus signal. It is a figure for demonstrating the operation | movement which moves an optical pick-up toward the outer peripheral side of an optical disk. It is a figure for demonstrating a DPP system. It is a basic diagram which shows the fundamental structure of the photodetector applicable to a DPP system. It is a flowchart which shows an example of the process which moves an optical pick-up to the predetermined position by the 2nd Embodiment of invention. It is a figure for demonstrating the relationship between the movement of an optical pick-up, and a tracking error signal. It is a figure for demonstrating the operation | movement which moves an optical pick-up toward the outer peripheral side of an optical disk.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk drive 10 Optical disk 20 Spindle motor 22 Optical pick-up 23 Thread motor 24 Thread 25 Signal processing part 27 Microcomputer 34 Objective lens 40 Photo detector

Claims (9)

An optical pickup that irradiates an optical disc with laser light and detects reflected laser light reflected from the optical disc;
A moving unit for moving the optical pickup in the radial direction of the optical disc;
A reference position detecting unit for detecting a reference position in the radial direction of the optical pickup based on a change in the reflected laser beam detected by the moving optical pickup in a state where tracking control is not performed by the moving unit. An optical disc device characterized by the above. The optical disc apparatus according to claim 1,
The optical disk apparatus, wherein the reference position detection unit detects the reference position based on a focus error signal obtained from the reflected laser light. The optical disk apparatus according to claim 2, wherein
The reference position detection unit determines whether or not the focus error signal exceeds a threshold value, and detects the position where the focus error signal is determined to exceed the threshold value as the reference position. Optical disk device to perform. The optical disc apparatus according to claim 1,
The optical disk apparatus, wherein the reference position detection unit detects the reference position based on a tracking error signal obtained from the reflected laser beam. The optical disk apparatus according to claim 4, wherein
The reference position detection unit determines whether or not the tracking error signal exceeds a threshold value within a predetermined time, and detects a position determined not to exceed the threshold value even after the predetermined time has elapsed as the reference position. An optical disc apparatus characterized by that. The optical disc apparatus according to claim 1,
The optical disk apparatus, wherein the reference position detection unit detects the reference position based on a light amount of the reflected laser light. Irradiating the optical disk with laser light by an optical pickup and detecting the reflected laser light reflected from the optical disk;
A step of moving the optical pickup in the radial direction of the optical disc;
A reference position detecting step for detecting a reference position in the radial direction of the optical pickup based on a change in the reflected laser light detected by the optical pickup that is moving without performing tracking control in the moving step; A method for detecting the position of an optical disc apparatus, comprising: An optical pickup that irradiates an optical disc with laser light and detects reflected laser light reflected from the optical disc;
A moving unit for moving the optical pickup in the radial direction of the optical disc;
A reference position detecting unit for detecting a reference position in the radial direction of the optical pickup based on a change in the reflected laser light detected by the moving optical pickup without tracking control by the moving unit. And
A reproducing apparatus, wherein the optical pickup is moved from the reference position to a predetermined position in the radial direction of the optical disk by the moving unit, and reproduction of information recorded on the optical disk is started. Irradiating the optical disk with laser light by an optical pickup and detecting the reflected laser light reflected from the optical disk;
A step of moving the optical pickup in the radial direction of the optical disc;
A reference position detecting step for detecting a reference position in the radial direction of the optical pickup based on a change in the reflected laser light detected by the optical pickup that is moving without performing tracking control in the moving step; ,
And a step of starting reproduction of information recorded on the optical disc by moving the optical pickup from the reference position to a predetermined position in the radial direction of the optical disc.

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