Abstract:
Provided is an optical disc drive device which stably controls an actuator of an optical pickup, by individually controlling an optical spot when following the guide track and an optical spot when recording/reproducing information on/from each recording layer. An optical spot when following the guide track and an optical spot when recording/reproducing information on/from each recording layer are individually controlled. At this time, the optical spot exclusive for the track and the optical spot exclusive for the recording/reproducing are formed on an optical disc.

Description:
INCORPORATION BY REFERENCE 
       [0001]    This application relates to and claims priority from Japanese Patent Application No. 2011-073880 filed on Mar. 30, 2011, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The present invention relates to an optical disc or optical disc device that can record and/or reproduce information for a recording layer without track grooves in the optical disc. 
         [0004]    (2) Description of the Related Art 
         [0005]    Japanese Patent Application Laid-Open No. 2003-59092 (hereinafter referred to as Patent Document 1) discloses an optical disc device that can record and/or reproduce information for a recording layer without track grooves in the optical disc. 
         [0006]    Japanese Patent Application Laid-Open No. 2008-299957 (hereinafter referred to as Patent Document 2) discloses a technique for maintaining high recording performance for the entire areas of the optical disc. 
       SUMMARY OF THE INVENTION 
       [0007]    In the technique disclosed in Patent Document 1, information data is recorded or reproduced on or from each recording layer with high accuracy along the guide track formed in advance on the guide track layer of the optical disc. However, in Patent Document 1, no consideration is made to a technique for controlling optical spots suitable for two laser beams making the maximum amplitude of, for example, a focus error signal or a tracking error signal. 
         [0008]    As disclosed in Patent Document 2, the recording and reproducing of Servo control signal is realized with the same laser beam for the recording layer as that of contents information signal in conventional optical disc devices, such as DVD, CD, and the like. 
         [0009]    An object of the present invention is to provide a disc device that can stably realize individual controlling of an optical spot for following the guide track and an optical spot for recording/reproducing information on/from each recording layer. 
         [0010]    The above problem can be overcome according to the claimed inventions, by way of example. 
         [0011]    According to the present invention, there is provided a disc device that can stably control the actuator of an optical pickup. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    These and other features, objects and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings wherein: 
           [0013]      FIG. 1  is a block diagram showing a configuration of an optical disc device according to an embodiment 1; 
           [0014]      FIG. 2  is an exemplary diagram showing a spiral direction of a tracking guide layer RL of an optical disc  1 ; 
           [0015]      FIG. 3  is an image diagram of optical spots on the tracking guide layer RL and a recording layer WL, of the embodiment 1; 
           [0016]      FIG. 4  is a block diagram showing a configuration of an optical disc device according to embodiment 2; and 
           [0017]      FIG. 5  is an image diagram showing optical spots on a tracking guide layer RL and a recording layer WL according to the embodiment 2. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0018]    Descriptions will now be made to an example of an optical disc device according to embodiments of the present invention. Configurations to be described now are examples only, and the present invention is not limited to the embodiments. 
       Embodiment 1 
       [0019]      FIG. 1  shows a block diagram of an optical disc device according to embodiment 1. An embodiment of the present invention will be described with reference to  FIG. 1 . 
         [0020]      FIG. 1  is a block diagram showing a configuration of an optical disc device according to the embodiment 1. In an optical pickup  2 , a laser light source  201  for servo is a semiconductor laser light source that emits red optical beams, for example, with a wavelength approximately 650 nm. In addition, the optical pickup  2  emits a predetermined amount of red optical beams Lr 1  under the control of a laser driving circuit  5 , onto a collimator lens  202 . The collimator lens  202  converts the red optical beam Lr 1  from diverging light to parallel light. Then, the converted light reaches a beam splitter  203 . The beam splitter  203  has a wavelength selection property (dichroic property), showing different reflectance values depending on the wavelength of the optical beam. The splitter  203  reflects approximately 100% of the optical beam with a wavelength approximately 650 nm, and also transmits approximately 100% of the optical beam with a wavelength approximately 405 nm. Thus, the splitter  203  reflects approximately 100% of the red optical beam Lr 1  with a wavelength approximately 650 nm toward a next beam splitter  204 . The red optical beam Lr 1  transmitted through the beam splitter  204  reaches an object lens  205 . The object lens  205  condenses the red optical beam Lr 1 , and irradiates the beam onto the tracking guide layer RL of the optical disc  1 . At this time, the red optical beam Lr 1  is reflected on the tracking guide layer RL of the optical disc  1 , and will be a red reflected beam Lr 2  toward an opposite direction of the red optical beam Lr 1 . 
         [0021]    The red reflected beam Lr 2  is converted into parallel light by the object lens  205 , and the converted light reaches the beam splitter  204 . At this time, the red reflected beam Lr 2  is reflected by the beam splitter  204  and reaches a condensing lens  207 . The condensing lens  207  converges the red optical beam Lr 2 , and irradiates the beam onto a photo detector  208 . A signal generation circuit  7  generates signals, and outputs the generated signals to a system controller  4 . Specifically, the signals to be generated by the circuit  7  are: a signal for servo control of a focus error signal and a tracking error signal output from the photo detector  208 ; a rotation synchronization signal for controlling the rotation of the optical disc  1  and a signal for reproducing an address of the track, from the wobbled track formed on the tracking guide layer RL; and a signal for reproducing information peculiar to a disc, such as the intensity of the optical beam for recording on the recording layer WL, or information for managing user data recorded on the recording layer WL. The system controller  4  outputs a focus control signal and a tracking control signal to the actuator driving circuit  10 , based on the focus error signal and the tracking error signal from the signal generation circuit  7 . The object lens  205  is configured to cooperate with an actuator  206 . The actuator  206  is driven into the focus direction and the tracking direction, in accordance with an output of the actuator driving circuit  10 . As a result, the servo control is realized in a state where the red optical beam Lr 1  follows the track while focusing on the tracking guide layer RL as a red optical focus Fr 1 . 
         [0022]    The track formed in the tracking guide layer RL of the optical disc  1  is made in a spiral form as shown in  FIG. 2 . The tracking control is done in such a manner that the red optical beam Lr 1  follows the track of the tracking guide layer, thereby enabling to perform the recording or reproducing continuously from the inner periphery to the outer periphery of the disc  1 . 
         [0023]    Accordingly, in the servo optical system of the optical pickup  2 , the red optical beam Lr 1  is irradiated onto the tracking guide layer RL of the optical disc  1 . Based on a received result of the red optical beam Lr 1  as a reflected light of the red optical beam, the focus control and the tracking control of the object lens  205  are achieved under the control of the system controller  4 . In addition, the red optical beam Lr 1  can be controlled to follow the track of the tracking guide layer RL. 
         [0024]    In the information optical system, a laser light source  209  for recording and reproducing data is a semiconductor laser light source for emitting, for example, blue laser light with a wavelength approximately 405 nm. The laser light source  209  emits a predetermined amount of blue optical beam Lb 0  under the control of a laser driving circuit  6  to a collimator lens  210 . The collimator lens  210  converts the blue optical beam Lb 0  from diverging light to parallel light. This light is reflected by a mirror  212 , and reaches a beam splitter  213 . The beam splitter  213  transmits a predetermined percentage of the blue optical beam Lb 0 , and the beam reaches a relay lens  214 . The relay lens  214  converts the blue optical beam Lb 0  from parallel light to converged light or diverging light with a movable lens  214 A, and changes the convergent state of the corresponding blue optical beam Lb 0  with a fixed lens  214 B. Then, the beam reaches the beam splitter  203 . 
         [0025]    The movable lens  214 A is set to be moved in an optical axis direction of the blue optical beam Lb 0  by a non-illustrated actuator. The movable lens  214 A is moved based on an output of a relay lens driving circuit  9 , thereby changing the convergent state of the blue optical beam Lb 0  emitted from the fixed lens  214 B. 
         [0026]    The beam splitter  203  transmits the blue optical beam Lb 0  in accordance with its wavelength. Then, the beam reaches the beam splitter  204 . The beam splitter  204  transmits a predetermined percentage of the blue optical beam Lb 0 . The beam Lb 0  reaches the object lens  205 . The object lens  205  condenses the blue optical beam Lb 0 , transmits the tracking guide layer RL of the optical disc  1 , and focuses the beam in the recording layer WL. The position of a blue light focus Fb 1  of the blue optical beam Lb 0  is fixed based on the convergent state in which it is emitted from the fixed lens  214 B of the relay lens  214 . That is, the blue optical focus Fb 1  is moved in a focus direction in the recording layer WL, in accordance with the position of the movable lens  214 A. As a result, the blue optical beam Lb 0  is irradiated from the tracking guide layer RL of the optical disc  1  to set the focus Fb 1  into the recording layer WL. Further, the depth Rd from the tracking guide layer RL of the corresponding focus Fb 1  is to be adjusted in accordance with the position of the movable lens  214  in the relay lens  214 . The moving distance of the movable lens  214 A is designed to be in proportion to the moving distance of the blue optical focus Fb 1  of the blue optical beam Lb 1 . For example, if the movable lens  214  is moved by 1 mm, the blue optical focus Fb of the blue optical beam Lb 0  is moved by 30 μm. 
         [0027]    The beam splitter  213  receives reflected light Lb 0   r  of the blue optical beam Lb 0 , thereby enabling to record and reproduce an arbitrary layer. The light is converged by a converging lens  215 , and irradiated onto a photo detector  216 . The photo detector  216  outputs a detected signal corresponding to an amount of detected light, to the signal generation circuit  8 . 
         [0028]    The signal generation circuit  8  generates a focus error signal representing an amount of deviation in a focus direction of the focus Fb 1  of the blue optical beam Lb 0 , and outputs the generated signal to the system controller  4 . 
         [0029]    The system controller  4  outputs a focus control signal based on the focus error signal from the signal generation circuit  8  to the relay lens driving circuit  9 . The actuator  214  is driven in a focus direction in accordance with the output of the relay lens driving circuit  9 , thereby performing the servo control in such a manner that the focus Fb 1  of the blue optical beam Lb 0  follows the recording layer WL. Further, the depth from the tracking guide layer RL of the corresponding focus Fb 1  is to be adjusted in accordance with the position of the movable lens  214 A of the relay lens  214 . As a result, as shown in  FIG. 3 , the blue optical beam Lb 0  is positioned in a focus position of the recording layer WL having a constant depth Rd(n) corresponding to “n” layer(s) from the tracking guide layer RL, thereby enabling to perform the recording/reproducing. 
         [0030]    The recording layer WL is a recording layer that records information thereon, upon irradiation of laser light of 405 nm onto the recording layer WL so as to optically change its form. When recording information on the recording layer WL, the blue optical beam Lb 0  with relatively high intensity is irradiated thereonto, thereby forming a recording mark in the focus Fb 1  of the recording layer WL. 
         [0031]    Thus formed recording marks are arranged in a plane-like form nearly parallel to a servo layer RL of the optical disc  1 . A plurality of recording layers can possibly be formed, by changing the depth Rd from the tracking guide layer RL of the focus Fb 1 , in accordance with the position of the movable lens  214 A of the relay lens  214 . 
         [0032]    When reproducing information from the recording layer WL, the blue optical beam Lb 0  is so set to be constant with low intensity that does not optically change the form of the recording layer WL, the depth Rd from the tracking guide layer RL of the corresponding focus Fb 1  is changed in accordance with the position of the movable lens  214 A of the relay lens  214 , the focus is made into an arbitrary layer of the recording layer WL, and its reflected light Lb 0   r  is received by the photo detector  216 , thereby enabling to reproduce the arbitrary layer. 
         [0033]    In the optical disc device having the semiconductor lasers with different wavelengths from each other (the laser light source  201  for servo and the laser light source  209  for recording/reproducing data like  FIG. 1 ), some control is possible unlike the conventional system that performs the focus control and the track control in one spot, like the optical disc device, such as the BD, DVD, CD, and the like. That is, if the installation angle of, for example, the laser light source  201  and the laser light source  209  is changed, the optical spot angles of the red light focus Fr 1  and the blue light focus Fb 1  can independently be controlled in relation to the tangential direction (hereinafter referred to as a direction “Tt”) of the guide track (see  FIG. 3 ) of the tracking guide layer RL. Thus, for example, as shown in  FIG. 3 , the track control is realized with the laser light source  201  installed at such an angle that the major axis of the optical spot of the red optical focus Fr 1  is parallel to the tangential direction “Tt” (Fr 1 _major axis//direction “Tt”) of the guide track, in relation to the major axis and minor axis of the red optical focus Fr 1 . This can enhance the push-pull amplitude in the push-pull system. The focus control is realized with the laser light source  209  installed at such an angle that the major axis of the optical spot of the blue optical focus Fb 1  is vertical to the tangential direction “Tt” (Fb 1 _major axis□direction Tt) of the guide track, in relation to the major axis and minor axis of the blue optical focus Fb 1 , as shown in  FIG. 3 . This can enhance the resolution for forming the recording/reproducing mark, when recording/reproducing data, and also results in recording/reproducing information data with high accuracy. 
         [0034]    In this embodiment, the red optical focus Fr 1 _major axis//direction “Tt” is set by way of example, along the blue optical focus Fb 1 _major axis direction “Tt”. Thus, “Fb 1 _major axis” is at an angle of 90° with respect to “Tt”, while “Fr 1 _major axis” is at an angle of 0° with respect to “Tt”. These angles are not necessarily 90° and 0°, as long as the maximum push-pull signal is attained, for example, in the push-pull system, or as long as the high resolution of the recording mark is attained in the case of recording. In the above description, the angel of the focus major axis has been changed in accordance with the installation angles of the laser light source  201  and the laser light source  209 . However, the angles may optically be changed, instead. 
       Embodiment 2 
       [0035]      FIG. 4  is a block diagram showing a configuration of an optical disc device according to embodiment 2. In this embodiment, a parallel plate  300  is inclined at a predetermined angle with respect to the optical beam emitted from the laser light source  209 . Other configurations of  FIG. 4  are the same as those of the embodiment 1, and thus will now be described again. In this embodiment, astigmatism correction is achieved only for the optical beam Lb 0  of the laser light source  209  using the parallel plate  300 . As a result, the ellipticity (ellipticity=Fb 1 _minor axis/Fb 1 _major axis) is set closer to 1, so as to make the ellipse have more rounded shape. Note that the ellipticity is a value as a ratio of Fb 1 _major axis and Fb 1 _minor axis of the optical spot Fb 1 . For example, as shown in  FIG. 5 , when recording/reproducing information, the ellipticity of the laser light is set closer to 1 in a manner that the optical spot Fb 1  is not affected by a neighbor recording mark and does not write over or delete the neighbor recording mark. That is, the optical spot Fb 1  (with the ellipticity suitable for recording/reproducing and hardly affected by the neighbor) is formed in the recording layer WL, thereby enabling to realize the focus control. 
         [0036]    In this embodiment, astigmatism correction is performed only for the optical spot of the laser light source  209 . However, this correction may be applied to the laser light source  201 , and may be applied to both lasers. It is not limited that the astigmatism correction is performed using the parallel plate  3 , and may be achieved using a cylindrical lens inserted in the device. 
       Embodiment 3 
       [0037]    In embodiment 3, in the configuration of the optical disc device according to the embodiment 2 of  FIG. 4 , the astigmatism correction is so performed as to set the ellipticity of the optical spot Fb 1  closer to 1 for more rounded shape, and the Fb 1 _major axis is inclined at 55° with respect to the direction “Tt” as described in the embodiment 1. As a result, it is possible to reduce the percentage in which the light of the optical spot Fb 1 _major axis is irradiated onto the neighbor recording mark. For example, the ellipticity can be set closer to 0.8 in order that the optical spot Fb 1  of the laser light source  209  for reproducing data is unlikely to be affected by the neighbor recording mark. If the optical spot is likely to be affected by the neighbor recording mark, the installation angle of the laser light source  209  is changed so as to change the angle of the optical spot Fb 1 , and the optical spot Fb 1  (with the ellipticity suitable for the reproducing mark and hardly affected by the neighbor) is formed in the recording film WL, thereby enabling to realize the focus control. As a result, information data can be reproduced with high accuracy. 
         [0038]    Accordingly, the preferred embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various changes may be made thereto. For example, the above-described embodiments have specifically been described for clearly describing the present invention, and do not necessarily include the above-described entire constituents. A part of the configuration of one embodiment may be replaced with another embodiment. In addition, a configuration of one embodiment may be added to the configuration of another embodiment. In the present invention, the descriptions have been made to the angle of Fr 1 _major axis at which the maximum amplitude is attained in the push-pull system. However, it is possible to apply other angles and ellipticity of Fr 1 _major axis that differ from those of the push-pull system, when generating a tracking error signal in accordance with a phase difference method, a 3 beam method, or a differential push-pull method. The direction and ellipticity of Fb 1 _major axis that are suitable for the recording and reproducing may be applied, when generating a focus error signal in accordance with a spot size method, a knife edge method, or the like. The spiral direction of the track of  FIG. 2  is toward the outer peripheral direction. However, the spiral direction may be toward inner peripheral direction. 
         [0039]    In the preferred embodiments of the present invention described above, a term “recording layer” is used. However, the existence of the “layer” is not always necessary. For example, the present invention may be applicable to a third-dimensional recording layer. The third-dimensional recording layer is called “layer”, but it has no layer, and the information signals are volume-recorded in it. 
         [0040]    While we have shown and described several embodiments in accordance with our invention, it should be understood that disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention. Therefore, we do not intend to be bound by the details shown in described herein but intend to cover all such changes and modifications that fall within the ambit of the appended claims.