JP2007220239A - Optical disk device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device capable of preventing the damaging of an objective lens or a disk caused by the defect of the disk, and its control method. <P>SOLUTION: When gap servo is executed in the area of a recording surface on which gap servo is to be started by a gap servo control system 35, if a defect is detected in the area by a camera 33, control is executed not to execute gap servo. Thus, the occurrence of damaging caused by the collision of an objective lens 26 with a disk D is prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that performs at least one of recording a signal on a disc-shaped recording medium and reproducing the recorded signal, and a control method for the optical disc apparatus.

  An optical disc (hereinafter, simply referred to as a disc) such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) is a removable medium that is loaded into the optical disc apparatus and removed from the optical disc apparatus. Therefore, dust such as dust or dust is likely to adhere to the disk on the recording surface of the signal. Further, when a disk is loaded into or removed from the optical disk apparatus, dust is likely to enter the casing from the loading port of the casing. When dust is mixed in the housing, the dust floats in the housing or adheres to the disk.

  Therefore, in particular, a master exposure apparatus provided with a dust measuring instrument that measures the amount of dust floating in the housing is disclosed (for example, see Patent Document 1). In this master exposure apparatus, the start and end of the exposure operation of the master are controlled according to the amount of dust measured by the dust measuring instrument.

The device disclosed in Patent Document 1 is a device that records a signal on a master disk using near-field light. As described above, in an optical disk device using near-field light, when recording or reproducing a signal, the distance between the objective lens and the signal recording surface of the disk needs to be controlled to a distance (near field) where the near-field light is generated. is there. This is hereinafter referred to as gap servo. For example, when a laser beam having a wavelength of about 400 nm is used, the near-field light is generated in a near-field state generally at a distance of ½ or less of the wavelength, and 100 nm or less for actual recording or reproduction. Must be controlled (see, for example, Patent Document 2).
JP 2004-334977 A (paragraph [0022], FIG. 1) JP 2005-259329 A (paragraph [0027])

  When an objective lens with a numerical aperture (NA) of 0.85 or higher is used, and dust is adhering to the disk, perform appropriate focusing servo and gap servo. The objective lens and the disk collide with each other through dust, and the objective lens or the disk may be damaged. In particular, an optical disk apparatus using near-field light has a large influence because an objective lens having a high numerical aperture of about NA = 1.8 is used.

  Further, not only when dust floating in the air adheres to the disc, but also when the disc is manufactured, the disc may be commercialized with dust attached to the surface of the signal recording surface. In that case, the flatness of the disk surface decreases. A disk including such a defect was not a problem when a signal was recorded or reproduced using a long-wavelength laser beam, but was not affected when a short-wavelength laser beam or near-field light was used. There is a risk that the objective lens and the disk may collide as described above.

  In view of the circumstances as described above, an object of the present invention is to provide an optical disc apparatus and a control method therefor that can prevent a situation where a condensing element or a recording medium is damaged due to a defect in the recording medium. is there.

  In order to achieve the above object, an optical disc apparatus according to the present invention comprises a rotational drive mechanism for rotationally driving a disc-shaped recording medium having a signal recording surface, and the signal to the recording medium rotationally driven by the rotational drive mechanism. A light condensing element for condensing a laser beam on the recording medium for recording or reproducing the signal, a distance control means for controlling a distance between the recording surface and the light condensing element, and on the recording surface Detection means for detecting a defect in an area where distance control is to be started by the distance control means, and whether the distance control is executed by the distance control means on the area according to a detection result of the detection means. Control means for controlling whether or not.

  In the present invention, when the distance control is performed on the region where the distance control is to be started by the distance control unit, the control unit does not perform the distance control when the detection unit detects a defect in the region. Control. Thereby, when the defect on the said area | region, for example, dust, has adhered to the condensing element, the situation where a condensing element and a recording medium collide and can be prevented can be prevented.

  “Condensing element” means an objective lens or an optical system that includes an objective lens and moves integrally with the objective lens by distance control means, and any element that can collect light on a recording medium. Good.

  “Distance control means” includes the meaning of means for performing focusing servo or means for performing gap servo. The focusing servo here is distance control when the NA of the objective lens is 0.85 or less. On the other hand, the gap servo is distance control when NA = 0.85 or when a signal is recorded or reproduced using near-field light. The gap servo here is distance control in a concept including “approaching operation” as will be described later.

  The “region where distance control should be started by the distance control means” may be an arbitrary region designated by a user's instruction or a predetermined region for starting distance control.

  The “defect” is not limited to dust adhering to the recording surface, but also includes a structural defect of the recording medium that occurs when the recording medium is manufactured.

  In the present invention, the detection means is an imaging means for imaging the area. For example, it is possible to reliably detect a defect by detecting a defect by obtaining an image with an imaging means, compared to a case where a defect is detected by irradiating a recording surface with laser light and the amount of reflected light. .

  In the present invention, the control means controls the distance control not to be executed when at least one defect of a predetermined number or more and a predetermined size or more is detected by the detection means. Thereby, it can prevent beforehand that dust etc. adhere to a condensing element and become dirty.

  In the present invention, the optical disc apparatus controls discharge so that the recording medium is discharged from the optical disc apparatus when at least one of a predetermined number or more and a predetermined size or more is detected by the detection means. Is further provided. The present invention includes a case where the detection operation of the detection means is performed a plurality of times. For example, when a defect is detected by the detecting means, the recording medium is cleaned, and then the defect is detected again. If the defect is still detected at that time, the recording medium is ejected. It only has to be done. The number of detection operations can be appropriately changed.

  In the present invention, the recording medium has a mark indicating a position where the distance control is performed in the area, and the detection unit is located at a position where the distance control is performed by detecting the mark. Detect defects. Thereby, the processing can be speeded up as compared with the case where a defect is detected in an arbitrary region.

  In the present invention, the detection means sets a region where the laser beam is focused on the recording surface during at least one rotation by the rotation drive mechanism as a region where the distance control is to be started by the distance control unit. , Detecting the defect. Thus, for example, a certain point on the recording surface is a region where the distance control is to be started, and a linear or planar region on the recording surface is a region where the distance control is to be started. However, there are more positions where the distance control on the recording surface can be executed, the processing speed is increased, and the distance control can be started reliably.

  In the present invention, the condensing element has a numerical aperture exceeding 0.85 and being condensed as near-field light. When the condensing element has a numerical aperture in such a range, the recording density by the recording medium is extremely high, and the operation by the distance control means must be performed with high accuracy. Therefore, the present invention is very effective.

  The method for controlling an optical disk apparatus according to the present invention includes a rotational drive mechanism that rotationally drives a disk-shaped recording medium having a signal recording surface, and records the signal on the recording medium that is rotationally driven by the rotational drive mechanism, or In order to reproduce the signal, a control method of an optical disc apparatus comprising: a condensing element that condenses laser light on the recording medium; and a distance control means that controls a distance between the recording surface and the condensing element. And detecting a defect in an area on the recording surface where distance control is to be started by the distance control means, and performing distance control by the distance control means on the area according to the detection result. Controlling whether or not to do so.

  As described above, according to the present invention, it is possible to prevent the condensing element or the recording medium from being damaged due to a defect in the recording medium.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view showing an optical disc apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing the internal structure of the optical disc apparatus 10 shown in FIG. In FIG. 2, the electric circuit board, wiring, and other mechanisms not related to the present invention are not shown.

  As shown in FIG. 1, the optical disc apparatus 10 includes a housing 5 and a recording / reproducing unit 15 disposed in the housing 5. As shown in FIG. 2, the housing 5 is configured such that a front panel 2 and a back panel 3 are erected on a base plate 1 provided at the bottom, and an interior is covered with an external cover 4. From this front panel 2, a disk tray 22 on which an optical disk medium D (hereinafter referred to as disk D) is mounted protrudes. That is, the disk tray 22 conveys the disk D between a position where recording is performed by a biaxial actuator 7 described later in the housing 5 and a position where a user outside the housing 5 can exchange the disk D. It is provided as possible.

  The front panel 2 of the housing 5 is provided with an opening 9 for inserting / removing the disk tray 22, and the opening 9 rotates in a range of about 90 degrees in conjunction with the insertion / removal of the disk tray 22. Is opened / closed by. In FIG. 2, the disk tray 22 is not shown. A tray panel 58 having an opening 58a through which the disk tray 22 is inserted and removed is disposed so as to face the opening 9 of the front panel 2.

  As shown in FIG. 1, for example, a type of disk accommodated in a disk cartridge 49 is used as the disk D. In FIG. 2, the cartridge 49 is not shown, and only the disk D is shown. However, the disk cartridge 49 is not necessarily required and may be a bare type. Further, as the disk D, for example, a type of disk that records or reproduces a signal by using near-field light is used. However, the present invention is not limited to this, and it may be a CD, a DVD, a BD (Blu-ray Disc (registered trademark)), or the like. When using near-field light, a recording density of 80 GB (gigabytes) per square inch or more is achieved.

  On the surface of the disc tray 22, a disc mounting recess 22a that conforms to the outer shape of the cartridge 49 is formed. The disc tray 22 is set with the disc D in the disc mounting recess 22a so that its signal recording surface E faces downward. It is conveyed in the state where it was done.

  The recording / reproducing unit 15 includes a clamp unit 17 that clamps the disk D, a spindle motor 18 that serves as a rotational drive mechanism that rotationally drives the clamped disk D, a signal recorded on the rotating disk, and the recorded signal. And an optical pickup 11 capable of at least one of reproducing.

  The optical pickup 11 includes a biaxial actuator 7 on which a condensing element such as an objective lens is mounted, and an optical system 8 on which a light source, a photodetector, a lens system, and the like are mounted. The optical system 8 is covered with a cover member 19, and detailed illustration is omitted here. The spindle motor 18 is held by a motor holder 67, for example. The clamp part 17 holds the disk D by, for example, holding the peripheral part of the center hole of the disk D with a magnet or the like. The disc mounting recess 22 a of the disc tray 22 is provided with a hole (not shown) for allowing a part of the clamp portion 17 to be inserted from the back side of the disc tray 22. Of course, the disc cartridge 49 is also provided with a hole (not shown) that is opened and closed by a shutter for the objective lens 26 (see FIG. 3) of the biaxial actuator 7 to access it.

  FIG. 3 is a perspective view showing the biaxial actuator 7. The biaxial actuator 7 may have a general configuration. For example, in the biaxial actuator 7, a wire support base 29 that supports the wire 28 is placed on and fixed to the base member 25. The tracking coil 31 and the focusing coil 32 are wound in a predetermined direction and attached to the bobbin 24, and the objective lens holder 23 that holds the objective lens 26 is mounted on the bobbin 24. The bobbin 24 is supported by the wire 28 and is movable in the tracking direction (Y-axis direction) and the focusing direction (gap direction) (Z direction). Magnets 27, 27 are respectively disposed at the front end and substantially the center of the base member 25, and these magnets 27 generate a magnetic field. The base member 25 is made of, for example, a magnetic material, and includes two attachment portions 25a to which the magnets 27 are attached, and two piece portions 25b that are erected so as to be inserted into holes 24a provided in the bobbin 24. Have. That is, the attachment portion 25a and the piece portion 25b are also made of a magnetic material, and the magnetic circuit is constituted by these and the magnet 27. According to such a configuration of the biaxial actuator 7, the objective lens 26 can be positioned at a predetermined address on the recording surface E of the signal of the disk D by applying a current to each of the coils 31 and 32. It becomes like this.

  Instead of the biaxial actuator 7, a triaxial actuator obtained by further adding an axis in the tilt direction (an inclination of the objective lens or the signal recording surface E of the disk with respect to the XY plane) in the biaxial direction may be used. .

  As the light source (not shown) included in the optical pickup 11, for example, a light source that emits laser light having a wavelength of about 400 nm is used. However, the design can be appropriately changed according to the type of the disk D. The optical system of the optical pickup 11 may have a known configuration as shown in FIG. 1 of Patent Document 2, for example, but is not limited thereto, and may be another known form. When near-field light is used, an objective lens 26 having NA (Numerical Aperture) of 1 or more is used. However, it goes without saying that an objective lens having an NA of less than 1 may be used depending on the wavelength of the laser beam.

  FIG. 4 is a perspective view showing the objective lens 26. The objective lens 26 is, for example, a SIL (Solid Immersion Lens), has a shape of a part of a sphere having a diameter of about 0.8 to 1 mm, and the upper portion of the objective lens 26 has a conical shape. The apex of the cone is a small plane of, for example, several tens of μm, and this becomes the end surface 26a of the objective lens 26 that faces the signal recording surface E of the disk D. The NA of the objective lens 26 is about 1.8. FIG. 5 is an enlarged plan view showing the end surface 26 a of the objective lens 26. The distance between the end surface 26a and the signal recording surface E of the disk D is the “gap” in the present embodiment. In addition to the objective lens 26, a condenser lens that collects laser light on the objective lens 26 is disposed in the objective lens holder 23 shown in FIG.

  FIG. 6 is a perspective view showing the optical disc apparatus 10 in a state where the front panel 2, the back panel 3, the tray panel 58, and the like of the housing are removed from the state shown in FIG. In the recording / reproducing unit 15, the clamp portion 17, the spindle motor 18, and the like are mounted on a movable base 48 that moves forward and backward in the Y-axis direction along the guide shaft 16. The tray panel 58 (see FIG. 2) is also connected to the movable base 48 so as to move integrally with the movable base 48. On the other hand, the optical pickup 11 is fixed on the base plate 1 or is fixed to a member such as a frame fixed to the base plate 1. The movable base 48 is connected to the movable shaft 14a of the sled motor 14 via an appropriate member 14b, and is configured to be movable in the Y-axis direction. The sled motor 14 has a potentiometer (not shown) that measures the amount of movement in the Y-axis direction, and thereby detects the position of the disk D due to the sled operation during recording or reproduction. By such a sled mechanism, the movable base 48, the spindle motor 18, the clamp part 17, and the tray panel 58 move integrally.

  In the housing 5, a loading mechanism (not shown) for transporting the disk tray 22 is provided between a position where a user outside the housing 5 can exchange the disk D and the clamp unit 17. The loading mechanism guides the conveyance of the disk tray 22 in the Y-axis direction along a pair of loading guides 21 provided to face each other in the housing 5. That is, the disc tray 22 is configured to be movable relative to the movable base 48, the spindle motor 18, the clamp unit 17, and the tray panel 58 that move together. In the state shown in FIG. 1, the movable base 48 is located closest to the front panel 2, and the disk tray 22 is arranged at a position closest to the clamp portion 17 during signal recording or reproduction.

  In the housing 5, the motor guide plate 12 is disposed to face both sides of the motor holder 67. 2 and 6, only one motor guide plate 12 is shown. The motor guide plate 12 is provided with a guide groove 12 a that engages and guides a guide pin 59 provided to protrude from the motor holder 67. A part of the guide groove 12a is formed obliquely on the front panel 2 side in the Y-axis direction. Accordingly, the guide pin 59 is guided along the guide groove 12a, whereby the motor holder 67 is moved up and down (moved obliquely) on the front panel 2 side. As the motor holder 67 moves up and down, the disc D is passed from the clamp portion 17 to the disc tray 22, and the disc D is passed from the disc tray 22 to the clamp portion 17. That is, since the disc tray 22 is fixed in the Z-axis direction, when the disc D is carried in, the motor holder 67 is raised by the drive of the sled motor 14, and the disc D is pushed up by the clamp portion 17. As a result, the disk D is transferred to the clamp unit 17. Conversely, when the disk D is ejected, the motor holder 67 is lowered by driving the sled motor 14, so that the disk D is transferred from the clamp portion 17 to the disk tray 22.

  FIG. 7 is a block diagram showing the configuration of the gap servo control system of the optical disc apparatus 10. The gap servo control system 35 includes a biaxial actuator 7, a photodetector 36, a standardized gain 41, an AD (analog to digital) converter 42, a gap servo target value setting unit 47, a switch 46, a filter 39, a DA (digital to) analog) converter 38 and driver 37.

  The controlled object is a biaxial actuator 7. The detected amount (controlled amount) is the amount of reflected return light 51 from the disk D and is detected by the photodetector 36. The detected reflected return light quantity 51 is normalized to 1 V, for example, by the normalization gain 41. The standardized signal is digitized by the AD converter 42. The digitized reflected return light quantity 51 is deviated from the target value 53 set by the gap servo target value setting unit 47, and a gap error signal is generated and input to the switch 46. When the switch 46 is turned on, that is, as described later, when the gap servo in the near field is started, the gap error signal 54 is output from the switch 46. The gap error signal 54 is phase-compensated by a filter 39 having a function such as phase compensation, converted into an analog signal by a DA (digital to analog) converter 38, and input to the driver 37. In response to the input signal, the driver 37 outputs a drive signal 58 so that the gap error signal 54 becomes zero, and drives the biaxial actuator 7.

  The gap servo control system 35 further includes a comparator 43 and a gap servo start threshold setting unit 44. The comparator 43 compares the reflected return light amount 51 output from the AD converter 42 with the voltage threshold value 52 for starting the gap servo in the near field set by the gap servo start threshold value setting unit 44, and the comparison result Is sent to the switch 46.

  The gap servo start threshold value 52 in the near field is set as shown in FIG. 8, for example. That is, the gap servo start threshold value 52 is set to a value larger than the target value 53 of the gap servo in the near field. For example, the gap servo start threshold value 52 is set to 0.8 (V) when the voltage value in the far field of the reflected return light amount 51 is normalized to 1 (V) in FIG.

  For example, when the reflected return light quantity 51 is larger than the gap servo start threshold value 52, that is, when the end surface 26a of the objective lens 26 is in the far field, the output of the comparator 43 becomes Low. On the other hand, when the reflected return light quantity 51 is smaller than the gap servo start threshold value 52, that is, when the end face 26a of the objective lens 26 is in the near field, it becomes High. When the output of the comparator 43 becomes High, the switch 46 is turned ON, and gap servo in the near field is started.

  When the end face 26a of the objective lens 26 is in the far field, the switch 46 is OFF (Low). At this time, an approach voltage for pulling the end surface 26a of the objective lens 26 from the far field to the near field to approach the disk is applied to a biaxial actuator (not shown). When the reflected return light quantity 51 becomes smaller than the gap servo start threshold value 52, the switch 46 is turned ON (High), and the gap servo in the near field is started with the approach voltage applied to the biaxial actuator.

  The “gap servo in the near field” in the present embodiment refers to a servo when the end surface 26a of the objective lens 26 enters the near field and after the switch 46 is turned on. This “gap servo in the near field (hereinafter simply referred to as“ near field servo ”)” and the operation during the transition from the end surface 26a of the objective lens 26 to the near field from when the end surface 26a is in the far field, Distinguish for convenience of explanation. That is, when the end face 26a of the objective lens 26 is in the far field and approaching the signal recording surface E of the disk D, and when the switch 46 is OFF, in the following description, “approach operation” It will be described separately from “near field servo”. In the following description, the concept including both “approaching operation” and “near field servo” is simply referred to as “gap servo”.

  FIG. 9 is a diagram showing a setting example of the gap servo start threshold value 52 and the gap servo target value 53 in the near field. For example, when the reflected return light quantity 51 is normalized so that the far field value is 1 (V), the gap servo target value 53 is set to 0.5 (V), for example.

  When the base material of the disk D is made of silicon, for example, the distance when the reflected return light quantity 51 starts to decrease is approximately 70 nm, the distance when the gap servo start threshold value 52 is reached is approximately 50 nm, and the gap servo target value 53 is approximately 25 nm. However, of course, these values vary depending on the wavelength of the laser beam.

  Returning to the description of FIG. A camera 33 that images the recording surface E of the disk D is provided in the housing 5. The camera 33 is fixed to the housing 5 and is supported by an appropriate member (not shown), for example. According to such a configuration, when the disk D is moved by the sled motor 14, the camera 33 moves on the recording surface E of the disk D in the radial direction (Y-axis direction). The camera 33 observes the presence or absence of defects on the recording surface E, for example, dust attached to the disk D. As the defect on the recording surface E, air bubbles are generated in the vicinity of the recording surface E when the disk D is manufactured, or dust or the like adhering at the time of manufacturing may be considered.

  The installation position of the camera 33 is not limited to the outer peripheral side of the disk D as illustrated, and may be installed on the inner peripheral side of the disk D from the illustrated position to the extent that the motor holder 67 does not interfere with the camera 33. Alternatively, when the disk D is made of a transparent base material, the camera 33 may capture images from the surface of the disk D (the surface opposite to the recording surface E). The camera 33 may not be fixed with respect to the housing 5, and may be configured to move in the radial direction of the disk D by a driving mechanism (not shown), for example. For example, a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor), or the like is used as an imaging element of the camera 33, but any element capable of converting two-dimensional image light into an electrical signal may be used.

  Alternatively, as shown in FIG. 10, a mirror 61 that reflects an image on the recording surface E of the disk D may be provided. An image reflected by the mirror 61 is taken by the camera 33. In FIG. 10, the reflection angle of the mirror 61 is almost a right angle, but the angle can be appropriately changed depending on the arrangement, shape, or structure of the camera 33. Further, there may be a plurality of mirrors 61, and the optical path of the image light may be folded back multiple times.

  FIG. 11 is a block diagram illustrating a configuration of a control system according to an embodiment of the optical disc apparatus 10. The system controller 45 acquires an image captured by the camera 33. The system controller 45 analyzes the image, and controls whether or not the gap servo control system 35 executes the gap servo according to the analysis result. Specifically, the system controller 45 sends a control signal to the driver 37 as shown in FIG. The gap servo control system 35 is a part of the control system 56 of the recording / reproducing unit, and the system controller 45 comprehensively controls the entire optical disc apparatus 10.

  FIG. 12 shows the voltage signal 51 of the reflected return light amount 1, the voltage signal (corresponding to the drive signal 58) applied to the axis actuator 7 and the guide voltage signal when the gap servo is performed by the gap servo control system 35. FIG. The guide voltage signals 52 and 53 correspond to the gap servo start threshold value 52 and the gap servo target value 53. The approach voltage is applied to the drive signal 58 of the biaxial actuator 7 at the point (A). Thereafter, at time (B), the voltage signal 51 of the amount of reflected return light falls below the guide voltage signal (gap servo start threshold 52 in the near field), the near field servo is started, and the guide voltage signal (gap servo in the near field) is started. It follows the target value 53). When the voltage signal 51 of the amount of reflected return light follows the gap servo target value 53, the system controller 45 starts signal recording or reproduction by the control system 56 of the recording / reproducing unit.

  FIG. 13 is a diagram illustrating a state in which the time axis is expanded at the time (B) illustrated in FIG. 12. As shown in FIG. 13, the voltage signal 51 of the amount of reflected return light is ideally drawn to a predetermined gap along the guide voltage signal 53. At this time, if the recording surface E of the disk D is dirty, the objective signal is lost. The end surface 26a of the lens 26 may be soiled to cause a malfunction such as a collision.

  FIG. 14 is a side view schematically showing how the objective lens 26 approaches the disk D by gap servo and dust is attached to the signal recording surface E. FIG. As shown in FIG. 14A, when dust 34 adheres to the signal recording surface E of the disk D, if the objective lens 26 approaches the recording surface E as shown in FIG. 26 and the disk D collide with each other through the dust 34. When the disk D is contaminated in this way, the object lens 26 is contaminated, and the amplitude of the gap error signal (GES) increases as shown in FIG. 15, and the amplitude of the tracking error signal (TES) decreases. Disturbed. In this case, it becomes impossible to shift to the tracking servo.

  Therefore, the optical disc apparatus according to the present embodiment operates as follows. FIG. 16 is a flowchart showing the operation.

  The system controller 45 drives the sled motor 14 so that the disk 33 reaches a position on the recording surface E of the disk D where the gap servo control system 35 images an area where gap servo should be started. Is moved (step 1601). The system controller 45 images the area with the camera 33 (step 1602).

  Here, the area where the gap servo is to be started may be an arbitrary area designated by a user instruction, for example, an area of user data that the objective lens 26 first tries to access when recording or reproducing a signal. Alternatively, it may be a predetermined area dedicated to starting the gap servo. In this case, a mark for exclusive use of the gap servo may be provided on the recording surface E. This mark may be recorded on the recording surface E by, for example, an uneven shape, or may be marked by printing or the like. Thereby, compared with the case where a defect is detected in an arbitrary region, the processing until gap servo is performed can be speeded up.

  FIG. 17 is an enlarged photograph showing the area when dust is attached to the area on the recording surface E imaged by the camera 33. For example, when gap servo is performed in the area F indicated by the broken line and the end face 26a of the objective lens 26 approaches, dust 34 adheres to the end face 26a as shown in FIG. FIG. 18 shows an image obtained by binarizing the image shown in FIG.

  As shown in FIG. 18, the system controller 45 determines whether dust of a predetermined number or more or a predetermined size or more has been detected, for example, by performing binarization processing and analyzing the image (step 1603). Preferably, the system controller 45 simply determines whether there is dust 34 or not. However, the present invention is not limited to this. This is because if dust less than a predetermined number or less than a predetermined size is detected, there may be cases where there is no effect on signal recording or reproduction. The condition for the number of dusts and the size condition may be AND conditions. Moreover, the conditions of the threshold value of the number of dusts and size can be set suitably.

  The image analysis is not limited to the binarization process as shown in FIG. 18, and may be analyzed at, for example, a gray level or a color level. The number of quantization bits at that time can be set as appropriate.

  Here, the “region where the gap servo should be started” corresponds to the range of the region F as shown in FIG. 17, for example, but is not limited to such a spot region. In other words, it is not limited to a zero-dimensional area. At the time of signal recording or reproduction, the disk D is rotated by the spindle motor 18, so that an image area for at least one round of the rotating disk D at a certain radial position on the recording surface E is the “gap servo”. It may be a “region to be started”. That is, it may be a linear (one-dimensional) area for one round. Since the recording signal is actually spiral, when the disk makes one round, the “radial position” is shifted by the track pitch.

  Alternatively, an area that is imaged not only for one round but also for appropriately set rounds may be set as an “area where gap servo should be started”. That is, a planar (two-dimensional) region may be used.

  As described above, by setting the “area where the gap servo should be started” as a one-dimensional or two-dimensional area, there is a position where the gap servo on the recording surface E may be executed. The processing speed is increased, and the gap servo can be started reliably.

  When a one-dimensional or two-dimensional area is imaged by the camera 33, the disk is discriminated so that the presence or absence of dust can be determined according to the performance of the imaging device of the camera 33, a processing circuit for imaging the image, and the like. The rotation speed may be set as appropriate.

  Returning to the description of FIG. In step 1603, when a predetermined number of particles or dust of a predetermined size or more is not detected, the system controller 45 performs gap servo control with the gap servo control system 35 in the imaged region (region where gap servo is started). Control to start (step 1604). After the gap servo is applied, a signal is recorded or reproduced (step 1605).

  FIG. 19 is a diagram illustrating a state of each signal when gap servo is appropriately performed. Compared with FIG. 15, in FIG. 19, there is no disturbance in the gap servo and tracking error signal.

  If dust of a predetermined number or more or a predetermined size or more is detected in step 1603, the gap servo is not performed and the system controller controls to eject the disc from the optical disc apparatus (step 1606). That is, in this case, the system controller 45 controls the driving of the sled motor 14 to remove the disk D from the clamp portion 17 and place the disk D on the disk tray 22, and further control the loading mechanism, thereby controlling the disk tray 22. Is pushed out of the housing 5. Alternatively, the system controller 45 may simply control the recording / reproduction unit control system 56 to stop without ejecting the disk D, or may warn by sound or display. When dust of a predetermined number or more or a predetermined size or more is detected, the gap servo is not performed, so that dust 34 adheres to the objective lens 26 and becomes dirty as shown in FIG. Can be prevented.

  FIG. 20 is a graph showing the results of observing the state of the recording surface E of several disks D. The horizontal axis represents the unique number of the disk D, and the vertical axis represents the number of defects having a dust diameter of about 10 μm or more. In this experiment, the experiment was performed with seven disks D. The fact that there are three data in one disk D indicates that the distances (radial positions) in the radial direction from the center of the circular disk in the area on the recording surface E to be measured are different. The number of defects represented by each bar represents the total amount of dust when the angle is measured 180 degrees (for the entire circumference) every 2 degrees at the same radial position. The radial positions from the center of the disk D, which are specific measurement objects, are 25 mm, 28 mm, and 31 mm, respectively.

  From this graph, for example, when the number of defects is 15 or more, the disk D may be controlled to be ejected as in step 1606 shown in FIG.

  As described above, in the present embodiment, when gap servo is executed in an area on the recording surface E where gap servo should be started by the gap servo control system 35, a defect is detected in that area by the camera 33. In this case, control is performed so that the gap servo is not executed. Thereby, the situation where the objective lens 26 and the disk D collide and are damaged can be prevented.

  In the present embodiment, in particular, the objective lens 26 having a numerical aperture (about 1.8) that exceeds 0.85 and is collected as near-field light is used. When the objective lens 26 has a numerical aperture in such a range, the recording density of the disk D is extremely high, and the operation by the gap servo control system 35 must be performed with high accuracy. Therefore, it is very effective that the system shown in FIGS. 11 and 16 is applied to the optical disc apparatus 10 using such near-field light.

  FIG. 21 is a flowchart showing the operation of the optical disc apparatus according to another embodiment. Steps 2101 to 2105 are the same as those in FIG. When dust of a predetermined number or more or a predetermined size or more is detected in step 2106, the system controller 45 cleans the recording surface E of the disk D (step 2106). Although the cleaning mechanism in this case is not shown, it may have a brush material, a paper material, or other members that are in contact with the disk D for cleaning. When the disk D is moved by the driving of the sled motor 14, the recording surface E and the brush material come into contact with each other, and dust is removed. In this case, the area imaged by the camera 33 may be cleaned, or the entire recording surface E may be cleaned.

  After cleaning, the system controller may re-image the same area on the recording surface and repeat the subsequent operations. The number of times of cleaning and the number of times of imaging by the camera 33 can be set as appropriate. If dust cannot be removed after cleaning once or multiple times, the disc may be ejected.

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

  In the above-described embodiment, the description has focused on the optical disc apparatus 10 that records or reproduces signals using near-field light. In this case, the gap servo control system 35 is taken as an example of distance control means. However, when an objective lens having an NA of 0.85 or less is used, a general focusing servo control system may be used instead of the gap servo control system 35.

  In the above embodiment, the camera 33 is used as means for detecting dust. However, the present invention is not limited to this, and a light source for irradiating light onto the recording surface E of the disk D and a photodetector that receives the light reflected from the recording surface E may be used as detection means. In this case, when the reflected light amount of light is detected by the photodetector, for example, when a reflected light amount that does not appear in the reflected light amount of the pit serving as the information source of the recorded information (for example, when the reflected light amount is extremely low) is detected, It can be determined that there is dust.

  The present invention can also be applied to the slot-in type optical disc apparatus 20 as shown in FIG. The slot-in method is a device that does not have the disc tray 22 shown in FIG. 1 and rotates the rollers by sandwiching the disc D with two or more rollers (not shown) provided in the housing 5, for example. Alternatively, as a slot-in method, there is a form in which the outer periphery of the disk D is held by an arm and the disk D is pulled into the housing 5.

1 is a perspective view showing an optical disc apparatus according to an embodiment of the present invention. It is a perspective view which shows the internal structure of the optical disk apparatus shown in FIG. It is a perspective view which shows a biaxial actuator. It is a perspective view which shows an objective lens. It is a plane enlarged photograph which shows the end surface of the objective lens shown in FIG. FIG. 3 is a perspective view showing the optical disc apparatus in a state where a front panel, a back panel, a tray panel and the like of the housing are removed from the state shown in FIG. 2. It is a block diagram which shows the structure of the control system of a gap servo. It is a figure which shows the gap servo start threshold value in a near field. It is the figure which showed the example of a setting of the gap servo start threshold value and gap servo target value in a near field. It is a figure which shows the form in which the mirror which reflects the image of the recording surface of a disc is provided. It is a block diagram which shows the structure of the control system which concerns on one embodiment of an optical disk apparatus. It is a figure which shows the voltage signal of the said reflected return light quantity when a gap servo is carried out by the gap servo control system, the voltage signal applied to a biaxial actuator, and a guide voltage signal. It is a figure which shows a mode that the time-axis was expanded at the time (B) shown in FIG. It is the side view which showed typically a mode that the objective lens approached the disk by the gap servo, and the dust adhered to the signal recording surface. It is a figure which shows a tracking error signal (TES) and a gap error signal (GES) when an objective lens is dirty. 5 is a flowchart showing an operation of the optical disc device according to the present embodiment. It is an enlarged photograph which shows the said area | region when dust has adhered to the area | region on the recording surface imaged with the camera. 18 shows an image obtained by binarizing the image shown in FIG. It is a figure which shows a gap error signal and a tracking error signal when gap servo is performed appropriately. It is a graph which shows the result of having observed the state of the recording surface of some discs. It is a flowchart which shows the operation | movement which concerns on other embodiment of the said optical disk apparatus. It is a perspective view which shows the external appearance of the optical disk apparatus based on other embodiment of this invention, and is a figure which shows the optical disk apparatus of a slot in system.

Explanation of symbols

D ... Optical disk medium E ... Signal recording surface 7 ... Biaxial actuator 10, 20 ... Optical disk device 11 ... Optical pickup 14 ... Thread motor 15 ... Recording / reproducing unit 26 ... Objective lens 26a ... End face 33 ... Camera 34 ... Dust 35 ... Gap servo Control system 45 ... System controller

Claims (8)

A rotational drive mechanism for rotationally driving a disk-shaped recording medium having a signal recording surface;
A light condensing element for condensing a laser beam on the recording medium in order to record the signal on the recording medium that is rotationally driven by the rotational driving mechanism or to reproduce the signal;
Distance control means for controlling the distance between the recording surface and the light collecting element;
Detecting means for detecting a defect in an area on the recording surface where distance control is to be started by the distance control means;
An optical disc apparatus comprising: a control unit that controls whether or not the distance control unit performs the distance control on the area according to a detection result of the detection unit. The optical disc apparatus according to claim 1,
The optical disc apparatus characterized in that the detection means is an imaging means for imaging the area. The optical disc apparatus according to claim 1,
The optical disc apparatus, wherein the control unit controls the distance control not to be executed when at least one defect of a predetermined number or more and a predetermined size or more is detected by the detection unit. The optical disc apparatus according to claim 1,
The apparatus further comprises discharge control means for controlling the recording medium to be discharged from the optical disc apparatus when at least one defect of a predetermined number or more and a predetermined size or more is detected by the detection means. Optical disk device to perform. The optical disc apparatus according to claim 1,
The recording medium has a mark indicating a position where the distance control is performed in the area,
The optical disc apparatus characterized in that the detection means detects a defect at a position where the distance control is executed by detecting the mark. The optical disc apparatus according to claim 1,
The detection means includes
The defect is detected by setting an area where the laser beam is focused on the recording surface during at least one rotation by the rotation driving mechanism as an area where the distance control is to be started. An optical disk device. The optical disc apparatus according to claim 1,
The optical disc apparatus, wherein the condensing element has a numerical aperture exceeding 0.85 and being condensed as near-field light. A rotational drive mechanism for rotationally driving a disk-shaped recording medium having a signal recording surface; and the recording medium for recording or reproducing the signal on the recording medium rotationally driven by the rotational drive mechanism A method of controlling an optical disc device comprising: a condensing element that condenses laser light; and a distance control unit that controls a distance between the recording surface and the condensing element;
Detecting a defect in an area on the recording surface where distance control is to be started by the distance control means;
And a step of controlling whether or not distance control is performed by the distance control means on the area according to the detection result.