JP2012155797A - Optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk drive capable of avoiding collision between an objective and an optical disk by performing suitable defocusing detection at a recording/reproduction fast-speed mode selected out of a plurality of supported recording/reproduction fast-speed modes.SOLUTION: An optical disk drive 1 includes: a laser unit 10 which emits laser light; an objective 13; a focus actuator 17 and a focus control part 21 which move the objective 13; an avoidance pulse output part 23 which controls the operation of the focus actuator 17 so that the objective 13 moves away from a surface of an optical disk OD; and a defocusing detection part 29 which detects defocusing occurring when a time for which the amplitude of an AS signal is equal to or less than a predetermined detection level lasts for a detection time determined according to a difference in fast speed of the optical disk OD or longer. When the defocusing is detected, the avoidance pulse output part 23 controls the focus actuator 17.

Description

  The present invention relates to an optical disk apparatus for recording and reproducing data recorded on a disc-shaped information carrier (hereinafter referred to as “optical disk”).

  Optical discs such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and BDs (Blu-ray Discs) are known as media on which large amounts of data are recorded, and are currently widely used.

  With the diversification of video formats and audio formats, various types of data are recorded on the optical disc. The transfer speed required for reproducing the video / audio data differs depending on the recorded data. The host device that outputs the video / audio data to the display, speakers, etc., checks what data is recorded from the optical disk loaded in the connected optical disk device, so that the required transfer speed is achieved. Change the double speed of the optical disk device.

  The recording density of the optical disc is determined by the spot diameter of the laser beam. As the spot diameter is smaller, a higher-density optical disc can be realized. The spot diameter of the laser beam is proportional to the laser wavelength and inversely proportional to the numerical aperture of the objective lens. Therefore, in order to reduce the spot diameter, it is necessary to shorten the laser wavelength and increase the numerical aperture.

  However, when the numerical aperture of the objective lens is increased, the focal length is shortened accordingly. When the focal length is shortened, the distance between the surface of the optical disk and the objective lens (working distance: hereinafter referred to as “WD”) is narrowed during recording on the disk or reproduction of the disk. Since the optical pickup is subjected to focus servo control, the objective lens normally does not come into contact with the optical disk surface. However, if the servo is released due to external vibration or scratches or dirt on the disk surface, the position of the objective lens cannot be controlled, and the objective lens may collide with the optical disk surface and damage the disk.

  In order to avoid such a situation, for example, in the optical disc apparatus described in Patent Document 1, focus control has been lost by comparing the signal amplitude obtained by the signal reproducing means with a predetermined detection level (hereinafter referred to as “ (Referred to as “out of focus”). That is, when the signal amplitude is lower than a predetermined detection level, it is determined that the signal is out of focus. When out-of-focus is detected, the optical disc apparatus generates an avoidance pulse to forcibly move the objective lens away from the disc surface.

  The optical disc apparatus described in Patent Document 1 can appropriately detect out-of-focus in correspondence with different types of discs. Specifically, in the case of BD, out-of-focus is detected when the signal amplitude is reduced by 35% with respect to the reproduction state, and in the case of DVD, out-of-focus is detected when it is reduced by 55%. As described above, the optical disc apparatus described in Patent Document 1 changes the threshold for detecting defocus according to the type of disc.

JP 2008-210489 A

  When detecting out-of-focus using the signal amplitude of the amount of reflected light, if there is a scratch or dirt on the surface of the optical disc, there is a risk that the out-of-focus will be erroneously detected. Since the amount of reflected light may decrease when passing through a scratched or dirty part, the focus error is detected erroneously even though the focus error has not actually occurred. In order to prevent such erroneous detection, a method is also known in which a counter is provided to determine out-of-focus when the detection level continues below a predetermined detection time and falls below the detection level.

  In order to avoid a collision between the objective lens and the disk surface, this detection time takes into account the worst-case objective lens behavior and optical disc surface vibration component that can be assumed when the WD and position are uncontrollable. Is set. In order to avoid collision between the objective lens and the optical disk, it is desirable to make the detection time as short as possible. However, in the case of recording / reproduction at low speed, if the detection time is short, there is a possibility of misdetecting defocus due to scratches or dirt. There is. On the other hand, in the case of recording / reproducing at a high speed, the displacement per unit time of the objective lens when the optical disk shakes is large. Therefore, if the detection time is long, detection of defocusing is delayed, and the risk of collision between the objective lens and the optical disk increases.

  In view of the above background, the present invention provides an optical disc apparatus capable of performing collision detection between an objective lens and an optical disc by performing appropriate defocus detection at a selected multiple speed among a plurality of supported recording / playback speeds. The purpose is to do.

  An optical disc apparatus according to the present invention is an optical disc apparatus capable of recording / reproducing at a plurality of double speeds, and includes a light source that emits laser light onto a recording layer of an optical disc loaded in the optical disc apparatus, and an objective that focuses the laser light. A lens, a focus actuator that moves the objective lens in a direction perpendicular to the disk surface of the optical disc, an electric signal generator that generates an electric signal based on reflected light from the recording layer, and an electric signal based on the electric signal A focus control unit that controls the operation of the focus actuator, an avoidance pulse output unit that controls the operation of the focus actuator so that the objective lens moves in a direction away from the disk surface of the optical disc, and the amplitude of the electrical signal Are compared with a predetermined detection level, and the amplitude of the electric signal is a predetermined detection level. A defocus detection unit that detects the occurrence of defocusing when the following time continues for a detection time determined according to the double speed of the optical disc, and the focus control unit according to the detection result of the defocus detection unit And a switching unit for switching between the operation control of the focus actuator by and the operation control of the focus actuator by the avoidance pulse output unit. An AS signal or an RF signal may be used as the electrical signal.

  According to the present invention, since the defocus is detected using the detection time determined according to the difference in the double speed of the optical disc, it is possible to appropriately detect the defocus according to the double speed. That is, at any double speed supported by the optical disk device, it avoids false detection of defocus due to scratches or dirt on the disk surface, and quickly generates an avoidance signal even when focus control is lost due to impact or the like. A function of avoiding a collision can be realized, and a highly reliable optical disc apparatus can be provided.

The figure which shows the structure of the optical disk apparatus of 1st Embodiment. 1 is a block diagram showing a connection configuration between an optical disc device, a host device, and a video / audio output device according to a first embodiment; The figure which shows the example of a circuit structure of an AS signal generation part The figure which shows the example of a circuit structure of an FE signal generation part. The figure which shows the example of a circuit structure of a TE signal generation part Diagram showing operation when out-of-focus is detected (A) A diagram showing the output of an AS signal when the optical disc has scratches or dirt at low speed, and (b) an AS signal output when the optical disc has scratches or dirt at high speed. Figure (A) The figure which shows WD when the surface shake occurs in the case of low speed, (b) The figure which shows the WD when the face shake occurs in the case of high speed. The figure which shows the structure of the optical disk apparatus of 2nd Embodiment. The figure which shows the structure of the optical disk apparatus of 3rd Embodiment.

Hereinafter, an optical disk device according to an embodiment of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of an optical disc device 1 according to the present embodiment, and FIG. 2 is a connection configuration of the optical disc device 1 according to the first embodiment, a host device 40, and a video / audio output device 44. FIG. The optical disc apparatus 1 can record / reproduce the optical disc OD at a plurality of double speeds. In FIG. 2, the optical disc apparatus 1 performs a start process at a predetermined start double speed with respect to the loaded optical disc OD. When the startup process is completed, the optical disc apparatus 1 transmits a startup process completion notification to the host device 40. The host device 40 acquires the data recorded on the optical disc OD from the optical disc device 1 and sets the reading double speed necessary for video / audio reproduction to the optical disc device 1. The optical disc apparatus 1 performs settings such as focus control and tracking control in accordance with the set double speed characteristics.

  The host apparatus 40 sequentially reads necessary data from the optical disk OD loaded in the optical disk apparatus 1 via an external interface (for example, APAPI) 41, and converts it into video / audio data by an internal decoder 42. The host device 40 transmits the converted video / audio data from the external interface (eg, HDMI) 43 to the video / audio output device (eg, liquid crystal TV) 44.

  Next, the optical disc apparatus 1 will be described with reference to FIG. The optical disc apparatus 1 includes a laser unit 10, a collimator lens 11, a beam splitter 12, an objective lens 13, a lens holder 14, a hologram element 15, and a light receiving element 16 as a configuration for an optical pickup. ing. The light beam emitted from the laser unit 10 passes through the collimator lens 11 and enters the beam splitter 12. The optical path is changed by the beam splitter 12 and enters the objective lens 13. The objective lens 13 condenses the incident light beam so as to produce a focal point on the recording layer of the optical disc OD.

  The reflected light diffracted and reflected by the recording layer of the optical disc OD passes through the objective lens 13 again and becomes parallel light. The reflected light that has become parallel light passes through the beam splitter 12. The reflected light that has passed through the beam splitter 12 is focused by the hologram element 15 so that the irradiation area has a predetermined size, and reaches the light receiving element 16. The light receiving element 16 is a quadrant detector in which the incident area is divided into four areas A, B, C, and D. The light receiving element 16 converts the incident light into an electric signal corresponding to the amount of irradiation light in each of the areas A, B, C, and D.

  The optical disc apparatus 1 includes a focus actuator 17 for driving the objective lens 13 and the lens holder 14 in a direction perpendicular to the recording layer of the optical disc OD, a tracking actuator 18 for driving in a parallel direction, and the focus actuator 17 and the tracking actuator 18 on the optical disc. A focus control unit 21 and a tracking control unit 22 that control to follow the surface deflection and eccentricity of the OD are provided. The focus control unit 21 controls the focus actuator 17 by transmitting a focus control signal to the drive circuit 19. The tracking control unit 22 controls the tracking actuator 18 by transmitting a tracking control signal to the drive circuit 20.

  The optical disc apparatus 1 also includes an avoidance pulse output unit 23 that controls the focus actuator 17 so that the objective lens 13 and the lens holder 14 are moved away from the optical disc OD. The avoidance pulse output unit 23 and the focus control unit 21 are connected to the focus actuator 17 via the switching unit 24. When the switching unit 24 switches between the avoidance pulse output unit 23 and the focus control unit 21, control of the normal focus actuator 17 that follows surface shake and control of collision avoidance that moves the objective lens 13 and the lens holder 14 away from the optical disk OD. Can be switched.

  The optical disc apparatus 1 includes an AS signal generation unit 25 that generates an all-sum (AS) signal based on the electrical signal converted by the light receiving element 16, an FE signal generation unit 26 that generates a focus error (FE) signal, A TE signal generation unit 27 that generates a tracking error (TE) signal and an RF signal generation unit 28 that generates a radio frequency (RF) signal that is a data signal are included. 3 to 5 are diagrams illustrating examples of circuit configurations of the AS signal generation unit 25, the FE signal generation unit 26, and the TE signal generation unit 27, respectively.

  The AS signal generation unit 25 inputs the generated AS signal to the out-of-focus detection unit 29. The out-of-focus detection unit 29 performs out-of-focus detection based on the input AS signal, and inputs an out-of-focus detection signal to the switching unit 24 when detecting out-of-focus. In response to this, the switching unit 24 switches the control of the focus actuator 17 from the focus control unit 21 to the avoidance pulse output unit 23.

  The FE signal generation unit 26 inputs the generated FE signal to the focus control unit 21. The focus control unit 21 controls the focus actuator 17 based on the input FE signal so that the light beam is focused on the recording layer of the optical disc OD. The TE signal generation unit 27 inputs the generated TE signal to the tracking control unit 22. The tracking controller 22 controls the tracking actuator 18 based on the input TE signal so that the light beam scans the track correctly.

  The optical disk apparatus 1 includes a waveform equalizer 32, a binarizing unit 33, a PLL unit 34, a demodulating unit 35, an error, as a configuration for reproducing the RF signal generated by the RF signal generating unit 28. A correction unit 36 and an I / F unit 37 are included. The RF signal generated by the RF signal generator 28 is equalized by the waveform equalizer 32, and the waveform is shaped. The shaped electrical signal is converted into a binarized signal by the binarizing unit 33. When the binarized signal is input to the PLL unit 34, data is extracted by synchronizing with the read clock, and is read as digital data via the demodulating unit 35 and the error correcting unit 36. The read digital data is transferred to the host device 40 via the I / F unit 37. The I / F unit 37 also has a function of receiving a request from the host device 40. The I / F unit 37 transmits a request received from the host device 40 to the system microcomputer 38, and the system microcomputer 38 controls the entire optical disc apparatus 1 according to the request.

  Next, the configuration of the out-of-focus detection unit 29 will be described. The out-of-focus detection unit 29 includes an out-of-focus detection level comparison unit 30 and an out-of-focus detection counter unit 31. The deviation detection level comparison unit 30 has a function of comparing the AS signal input from the AS signal generation unit 25 with a predetermined detection level and inputting the comparison result to the deviation detection counter unit 31. The outlier detection counter unit 31 determines whether or not the state in which the AS signal is equal to or lower than the predetermined detection level continues for a predetermined detection time or more based on the comparison result information input from the outlier detection level comparison unit 30. To do.

  Here, the predetermined detection time is a time determined according to the difference in the double speed of the optical disc OD. The system microcomputer 38 determines a predetermined detection time based on the information on the double speed of the optical disk OD, and inputs the predetermined detection time to the detachment detection counter unit 31. The detection time is set to be longer when the double speed is a low double speed than when the double speed is a high speed. This is because even if the scratches and dirt have the same size, the time required to read the portion (the reading light beam passes) is longer in the case of the low speed. The system microcomputer 38 may input information about the double speed of the optical disc OD to the outlier detection counter unit 31, and the outage detection counter unit 31 may determine a predetermined detection time.

  Next, the operation of the optical disc apparatus 1 configured as described above will be described. The optical disc apparatus 1 generates an RF signal based on the reflected light from the recording layer of the optical disc OD to reproduce the optical disc OD, generates an FE signal and a TE signal, and performs focus error control based on the FE signal and the TE signal. And tracking error control. Further, the optical disc apparatus 1 determines the detection time for detecting the defocus based on the information on the reproduction double speed of the optical disc OD by the system microcomputer 38, and inputs the data of the detection time to the defocus detection unit 29. The defocus detection unit 29 generates an AS signal based on the reflected light, performs a defocus detection process based on the AS signal, and controls the focus actuator 17 when the defocus is detected. By switching from 21 to the avoidance pulse output unit 23, collision avoidance control is performed.

  FIG. 6 is a diagram illustrating an operation when a focus out is detected. 6 shows the position of the objective lens 13 with respect to the recording surface of the optical disc OD, the middle part of FIG. 6 shows the output of the AS signal, and the lower part of FIG. 6 shows the focus control signal for the focus actuator 17. In the example shown in FIG. 6, the AS signal starts to decrease at time t <b> 1, becomes a predetermined detection level or lower at time t <b> 2, and the state where the AS signal is lower than the predetermined detection level continues until time t <b> 3. In this example, the time (t3-t2) is a predetermined detection time given from the system microcomputer 38. When the time t3 is reached, the defocus detection unit 29 detects defocus.

  When the out-of-focus detection unit 29 detects out-of-focus, control for the focus actuator 17 is switched from the focus control unit 21 to the avoidance pulse output unit 23. The avoidance pulse output unit 23 transmits an avoidance pulse as a focus control signal for the focus actuator 17, as shown in the lower part of FIG. The avoidance pulse is transmitted from time t3 to time t4. Thereby, as shown in the upper part of FIG. 6, the objective lens 13 is moved away from the disk surface, and the collision between the objective lens 13 and the optical disk OD can be avoided.

  In the optical disc apparatus 1 according to the present embodiment, the system microcomputer 38 determines a detection time used for detecting out-of-focus according to the reproduction / recording speed of the optical disc OD, and detects out-of-focus using the determined detection time. Therefore, the collision can be appropriately avoided at any double speed supported by the optical disc apparatus 1.

  FIGS. 7A and 7B are diagrams illustrating the output of the AS signal when the optical disc OD is scratched or dirty. FIG. 7A shows a case where the double speed is a low double speed, and FIG. 7B shows a case where the double speed is a high double speed. As can be seen by comparing FIG. 7A and FIG. 7B, the time during which the AS signal continues to decrease due to the same size of scratches and dirt is different between the low speed and the high speed. Therefore, if the same detection time is used for the low speed and the high speed, the out-of-focus state is not detected in the high speed mode, but it is erroneously detected that the focus is out in the low speed mode. In the present embodiment, when the double speed is low, the detection time is set longer than that when the double speed is high. Therefore, it is possible to prevent erroneous detection of defocusing at the low speed. In addition, when the double speed is high, it is preferable to shorten the detection time. The reason for this will be described with reference to FIG.

  FIG. 8A and FIG. 8B are diagrams showing WD when surface runout occurs. FIG. 8A shows a case where the double speed is low and FIG. 8B shows a case where the double speed is high. As can be seen from a comparison between FIG. 8A and FIG. 8B, since the surface shake at high speed is higher than that at low speed, the WD becomes 0 in a short time and the objective lens. 13 and the optical disc OD collide. When the double speed is high, the detection time for detecting out-of-focus can be shortened, so that out-of-focus can be detected earlier and collision due to surface shake can be prevented.

(Second Embodiment)
FIG. 9 is a diagram illustrating a configuration of the optical disc device 2 according to the second embodiment. The basic configuration of the optical disc apparatus 2 of the second embodiment is the same as that of the first embodiment. In the second embodiment, the out-of-focus detection unit 29a detects out-of-focus using an RF signal instead of an AS signal.

(Third embodiment)
FIG. 10 is a diagram illustrating a configuration of the optical disc device 3 according to the third embodiment. The basic configuration of the optical disc apparatus 3 of the third embodiment is the same as that of the first embodiment. In the third embodiment, the out-of-focus detection unit 29b switches the AS signal and the RF signal and performs out-of-focus detection using any one of the signals.

  The out-of-focus detection unit 29 receives the AS signal from the AS signal generation unit 25, and receives the RF signal from the out-of-focus detection level comparison unit 30 and the RF signal generation unit 28, which compares the received AS signal with a predetermined detection level. In addition, an outlier detection level comparison unit 30 is provided for comparing the received RF signal with a predetermined detection level. The detachment detection level comparison unit 30 and the detachment detection level comparison unit 30 a are connected to the detachment detection counter unit 31 via the switching unit 39. The switching unit 39 is connected to the system microcomputer 38. The switching unit 39 inputs the comparison result of either the AS signal or the RF signal to the detection counter unit 31 in accordance with a command from the system microcomputer 38.

  As described above, the AS signal and the RF signal are switched, and the out-of-focus detection is performed using any one of the signals. For example, when the RF signal cannot be obtained like a blank disk, the AS signal is switched to be used. It is possible to properly detect out of focus.

  As described above, the present invention has the effect of being able to perform appropriate defocus detection at a selected multiple speed among a plurality of supported recording / reproducing speeds, and the collision between the objective lens 13 and the optical disk. This is useful as an optical disk device or the like that can avoid the above.

1-3 Optical disc device 10 Laser unit 11 Collimator lens 12 Beam splitter 13 Objective lens 14 Lens holder 15 Hologram element 16 Light receiving element 17 Focus actuator 18 Tracking actuators 19 and 20 Drive circuit 21 Focus control unit 22 Tracking control unit 23 Avoidance pulse output unit 24 switching unit 25 AS signal generating unit 26 FE signal generating unit 27 TE signal generating unit 28 RF signal generating unit 29 defocusing detecting unit 30 deviating detection level comparing unit 31 deviating detection counter unit 32 waveform equalizer 33 binarizing unit 34 PLL Unit 35 demodulation unit 36 error correction unit 37 I / F unit 38 system microcomputer 39 switching unit 40 host device 41 APAPI I / F
42 Decoder 43 HDMI I / F
44 Video / audio output device

Claims (3)

An optical disc apparatus capable of recording and reproducing at a plurality of double speeds,
A light source that emits laser light to a recording layer of an optical disk loaded in the optical disk device;
An objective lens for focusing the laser beam;
A focus actuator for moving the objective lens in a direction perpendicular to the disk surface of the optical disk;
An electrical signal generator that generates an electrical signal based on the reflected light from the recording layer;
A focus control unit that controls the operation of the focus actuator based on the electrical signal;
An avoidance pulse output unit for controlling the operation of the focus actuator so that the objective lens moves in a direction away from the disk surface of the optical disk;
The amplitude of the electrical signal is compared with a predetermined detection level, and when the time when the amplitude of the electrical signal is equal to or lower than the predetermined detection level continues for a detection time determined according to the double speed of the optical disc, the focus is lost. An out-of-focus detector for detecting occurrence;
A switching unit that switches operation control of the focus actuator by the focus control unit and operation control of the focus actuator by the avoidance pulse output unit according to a detection result of the defocus detection unit;
An optical disc device comprising:   The optical disc apparatus according to claim 1, wherein the electrical signal generation unit generates an AS signal, and the out-of-focus detection unit detects out-of-focus by comparing the AS signal with the predetermined detection level.   The optical disc apparatus according to claim 1, wherein the electrical signal generation unit generates an RF signal, and the out-of-focus detection unit detects out-of-focus by comparing the RF signal with the predetermined detection level.

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