Patent Publication Number: US-2010110849-A1

Title: Information recording/reproducing device and method

Description:
TECHNICAL FIELD 
     The present invention relates to, for example, an information recording/reproducing apparatus and method which records information onto a recording medium formed of a ferroelectric substance or the like, or which reproduces the recorded information, by using a plurality of probes arranged in an array form. 
     BACKGROUND ART 
     As this type of information recording/reproducing apparatus, there is an apparatus which brings a plurality of cantilever-type probes into contact with a high-density, small recording medium, thereby reading and/or writing information. For example, the information is recorded or reproduced by using the plurality of probes arranged in a direction perpendicular to a scanning direction to scan a plurality of linear information tracks having a predetermined length, in parallel. In such construction, for example, if there is a temperature difference between the recording medium and the probe array in which the plurality of probes are disposed, a difference in their thermal expansion coefficients causes a deviation between the information tracks and each probe, which makes it hardly possible to read and/or write the information. Thus, there has been suggested a technology in which the recording medium or the probe array is divided into a plurality of block areas and each of the block areas is driven independently (refer to a patent document 1).
     Patent document 1: Japanese Patent Publication No. 3029499   

     DISCLOSURE OF INVENTION 
     Subject To Be Solved By the Invention 
     In the aforementioned technology, however, the independent drive of each block area causes an increase in size of an actuator for drive, and this basically makes it hard to simplify and miniaturize the apparatus, which is technically problematic. In particular, in order to perform super high-density recording, it is extremely preferable to form the plurality of probes in a small area (or domain), so that the simplification or miniaturization of the apparatus here is extremely important. 
     In view of the aforementioned problems, it is therefore an object of the present invention to provide an information recording/reproducing apparatus and method which are suitable for the simplification of the apparatus structure. 
     Means For Solving the Object 
     The above object of the present invention can be achieved by an information recording/reproducing apparatus provided with: a recording medium having a recording surface; and a probe array for scanning a plurality of information tracks which are arranged in parallel along a track direction, in parallel in the track direction on the recording surface, thereby performing at least one process of information recording and reproduction, the probe array having a plurality of probes arranged in a crossing direction of crossing at least the track direction, at least one of the recording medium and the probe array being divided in the crossing direction into a plurality of divided portions each of which includes at least one information track or probe, the information recording/reproducing apparatus further comprising: a first driving device capable of driving each of the plurality of divided portions in the crossing direction; and a second driving device for driving the probe array with respect to the recording surface in the track direction. 
     According to the information recording/reproducing apparatus of the present invention, in its recording or reproduction operation, at least one process of information recording and reproduction is performed by the plurality of probes scanning the plurality of information tracks which are arranged in parallel along the track direction, in parallel in the track direction on the recording surface of the recording medium formed of a ferroelectric substance or the like. Such displacement or scanning of the probe array in the track direction is performed by the second driving device such as an actuator for scanning the probe array or the like. Here, the expression “the probe array having a plurality of probes arranged in a crossing direction” means that the plurality of probes are arranged in the crossing direction (e.g. in a longitudinal direction or a Y-direction) and that the plurality of probes may be arranged in the track direction (e.g. in a lateral direction or an X-direction). Typically, many probes are arranged even in the track direction, so that a large amount of information can be read or written, simultaneously. However, even if there is only one probe in the track direction, the effect of the present invention due to the adjustment in the crossing direction can be exerted properly. 
     In particular, in the present invention, one of the recording medium and the probe array is physically divided in the crossing direction into the plurality of divided portions each of which includes at least one information track or probe. In other words, if the recording medium is divided, each of the divided portions includes at least one information track. If the probe array is divided, each of the divided portions includes at least one probe. Incidentally, the number of information tracks or probes included in each of the divided portions may be the same or different. Moreover, the expression “being divided in the crossing direction” means being divided by a dividing line extending in a direction along the information tracks. At this time, one or a plurality of dividing lines may be set. 
     Each of the plurality of divided portions divided in the above manner can be driven in the crossing direction by the first driving device such as an actuator for adjusting a gap of the divided portions. In other words, the gap of the divided portions can be adjusted to a desired gap by the first driving device. Thus, for example, if thermal expansion or the like causes a deviation between the information tracks and the probes and if the probes cannot scan the information tracks, each of the plurality of divided portions is driven in the crossing direction before, simultaneously with, or in tandem with the aforementioned recording and reproduction, and the deviation can be corrected in each divided portion. Therefore, even if there is the deviation between the information tracks and the probes, it is possible to correctly record or reproduce the information. 
     Moreover, the effect of the deviation correction described above changes depending on the number of divided portions, and division into more divided portions provides finer correction. In contrast, the smaller number of divided portions simplifies the structure of the apparatus. Thus, the number of division is determined on the basis of a difference in coefficient of thermal expansion between the recording medium and the probe array, an operating temperature range of the apparatus, a track deviation allowable range in the recording or reproduction, or the like. 
     As explained above, according to the information recording/reproducing apparatus in the present invention, it is possible to correctly record or reproduce the information even if there is the deviation between the recording medium and the probes, while realizing the simple structure of the apparatus. 
     In one aspect of the information recording/reproducing apparatus of the present invention, the second driving device collectively drives the plurality of divided portions. 
     According to this aspect, the plurality of divided portions are correctively driven by the second driving device in the recording or reproduction operation. As described above, the deviation between the information tracks and the probes in the crossing direction is already corrected by performing the drive by the first driving device before the recording or reproduction operation. Thus, even if the plurality of divided portions are collectively driven by the second driving device, i.e. even if the probe array covering the plurality of divided portions is operated to perform the scanning, the recording or reproduction can be performed without problems. 
     As explained above, by collectively driving the plurality of divided portions, for example, unnecessary an increase, complication or enlargement of an actuator for drive. Thus, it is possible to prevent complication or enlargement of the apparatus. In other words, it is possible to further simplify or miniaturize the apparatus. 
     In another aspect of the information recording/reproducing apparatus of the present invention, the second driving device drives the other of the recording medium and the probe array that is not divided into the plurality of divided portions. 
     According to this aspect, in the recording or reproduction operation, the other of the recording medium and the probe array that is not divided into the plurality of divided portions is driven by the second driving device in the track direction. In other words, if the recording surface is divided, the recording medium is driven by the first driving device and the probe array is driven by the second driving device. Moreover, if the probe array is divided, the probe array is driven by the first driving device and the recording medium is driven by the second driving device. 
     By separately driving the recording medium and the probe array by using the first driving device and the second driving device, for example, it is unnecessary to adjacently dispose an actuator or the like. In other words, it is possible to prevent the structure of one portion of the entire apparatus from extremely becoming complicated. 
     As explained above, by driving the other of the recording medium and the probe array that is not divided into the plurality of divided portions by using the second driving device, it is possible to further simplify or miniaturize the apparatus. 
     In another aspect of the information recording/reproducing apparatus of the present invention, the first driving device can drive the plurality of divided portions by using a width which is greater than an interval between adjacent two divided portions of the plurality of divided portions. 
     According to this aspect, when the gap of the plurality of divided portions is adjusted, the plurality of divided portions are driven in the crossing direction by using the width which is greater than the interval between the adjacent two divided portions of the plurality of divided portions. Incidentally, the “interval” herein shall be the width of a space between the plurality of divided portions physically divided, in a state of being not driven by the first driving device. 
     In the aspect, in particular, as described above, the plurality of divided portions are driven by the width which is greater than the interval between the adjacent two divided portions (hereinafter, referred to as an interval of the divided portions, as occasion demands). Thus, for example, even if there is a deviation with the width which is greater than the interval of the divided portions, the deviation can be corrected by the drive in the crossing direction. In other words, as long as the divided portions move by the width which is greater than the interval, there is little deviation that cannot be corrected. Incidentally, if the divided portions are driven by the width which is greater than the interval of the divided portions, the adjacent divided portions likely collide with each other; however, the collision can be avoided by driving the divided portions in conjunction with each other (e.g. in the same direction). 
     Moreover, being driven by the width which is greater than the interval of the divided portions can be restated as the small interval of the divided portions with respect to the width by which the divided portions are driven in the crossing direction. Thus, since a dead space is not consumed for the interval of the divided portions, it is possible to further miniaturize the apparatus. 
     As explained above, by driving the plurality of divided portions by the width which is greater than the interval of the divided portions, it is possible to miniaturize the apparatus in response to the relatively large deviation. 
     In another aspect of the information recording/reproducing apparatus of the present invention, the first driving device and the second driving device mutually share an elastic member and an actuator, the elastic member movably supporting the plurality of divided portions in the crossing direction and in the track direction, the actuator capable of driving the plurality of divided portions in the crossing direction and in the track direction. 
     According to this aspect, the plurality of divided portions are supported by the elastic member movably in the crossing direction and in the track direction, and the plurality of divided portions can be driven by the actuator in the crossing direction and in the track direction. Incidentally, the “elastic member” is typically a spring and supports the plurality of divided portions by connecting the plurality of divided portions and a frame or the like placed around the divided portions. 
     In the aspect, in particular, since the plurality of divided portions are supported by the elastic member, even if the position is displaced by the drive by the actuator, the divided portions are kept supported certainly. Therefore, it is possible to record or reproduce the information certainly. 
     The above object of the present invention can be achieved by an information recording/reproducing method using an information recording/reproducing apparatus provided with: a recording medium having a recording surface; and a probe array for scanning a plurality of information tracks which are arranged in parallel along a track direction, in parallel in the track direction on the recording surface, thereby performing at least one process of information recording and reproduction, the probe array having a plurality of probes arranged in a crossing direction of crossing at least the track direction, at least one of the recording medium and the probe array being divided in the crossing direction into a plurality of divided portions each of which includes at least one information track or probe, the information recording/reproducing method provided with: a first driving process of driving each of the plurality of divided portions in the crossing direction; and a second driving process of driving the probe array with respect to the recording surface in the track direction. 
     According to the information recording/reproducing method of the present invention, in the first driving process, each of the plurality of divided portions is driven in the crossing direction before, simultaneously with, or in tandem with the aforementioned recording and reproduction. In other words, if there is a deviation between the probes and the information tracks, each of the plurality of divided portions is driven in the crossing direction, and the deviation is corrected in each divided portion. Typically, in the second driving process, the probe array is driven in the track direction with respect to the recording surface after or while the deviation is corrected. In other words, the recording or reproduction is performed by the probe array scanning the recording surface. Therefore, even if there is the deviation between the information tracks and the probes, it is possible to correctly record or reproduce the information. Incidentally, as described above, if there is no deviation, the first driving process may be omitted. 
     As explained above, according to the information recording/reproducing method of the present invention, it is possible to correctly record or reproduce the information even if there is the deviation between the recording medium and the probes, while realizing the simple structure of the apparatus. 
     Incidentally, even the information recording/reproducing method of the present invention can adopt the same various aspects as those of the information recording/reproducing apparatus of the present invention described above. 
     The operation and other advantages of the present invention will become more apparent from the embodiments described below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view showing the structure of an information recording/reproducing apparatus in a first embodiment. 
         FIG. 2  is a H-H′ cross sectional view in  FIG. 1 . 
         FIG. 3  is an enlarged side view showing a probe portion. 
         FIG. 4  is a plan view showing the structure of an electrostatic-drive actuator. 
         FIG. 5  are cross sectional views showing correction of a deviation between probes and information tracks. 
         FIG. 6  are plan views showing the structure of an information recording/reproducing apparatus in a second embodiment. 
     
    
    
     DESCRIPTION OF REFERENCE CODES 
     
         
           110  recording medium 
           120  information track 
           130  probe 
           140  first actuator 
           150  first spring 
           160  second actuator 
           170  second spring 
           210  first fixed part 
           220  second fixed part 
           300  probe array 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments below, an information recording/reproducing apparatus for recording information as a polarization direction onto a ferroelectric recording medium will be exemplified, which is one example of the information recording/reproducing apparatus of the present invention. 
     First Embodiment    
     Firstly, the structure of an information recording/reproducing apparatus in the first embodiment will be described with reference to  FIG. 1  to  FIG. 3 .  FIG. 1  is a plan view showing the structure of an information recording/reproducing apparatus in the first embodiment.  FIG. 2  is a H-H′ cross sectional view.  FIG. 3  is an enlarged side view showing a probe portion. Incidentally, in  FIG. 1 , for convenience of explanation, a probe array is transparently shown. 
     In  FIG. 1  and  FIG. 2 , the information recording/reproducing apparatus in the first embodiment is provided with a recording medium  110 ; a probe array  300  formed by arranging a plurality of probes  130 ; first actuators  140  and first springs  150 , which are one example of the “first driving device” of the present invention; second actuators  160  and second springs  170 , which are one example of the “second driving device” of the present invention; a first fixed part  210 ; and a second fixed part  220 . 
     The recording medium  110  is formed by supporting a ferroelectric thin film of a PZT (lead zirconate titanate), LiTaO 3  (lithium tantalite), or the like with a plate of silicon or the like. The recording medium  110  is physically divided into three divided portions in a Y-direction shown in the drawing, and there is a space (e.g. about 0.1 mm) between the adjacent two divided portions. Information is recorded on a recording surface  110   a  formed of a ferroelectric thin film, as a linear information track  120  extending in an X-direction in the drawing. Moreover, on the recording surface  110   a  which is unrecorded, a servo mark or the like indicating an interval of the information tracks  120  may be recorded. Incidentally, here, the recording medium  110  is divided into three divided portions; however, the division may be performed such that each divided portion includes at least one information track  120 , and the size of the divided portion (e.g. the number of tracks included) may be different in each divided portion. 
     The probe array  300  is, for example, a glass substrate, and the plurality of probes  130  are disposed on the substrate. For example, the probes  130  are disposed in a grid of 3×2 in each divided area, as shown in  FIG. 1 . 
     In  FIG. 3 , the probe  130  is, for example, a probe with a small tip made of silicon. The probe  130  is supported by a support part  135   a,  thereby being formed as a cantilever. Then, by bringing the tip into contact with the recording medium  110 , the information is recorded or reproduced. Incidentally, in addition to performing the information recording or reproduction, the probe  130  can also detect the position of the information track  120  for the purpose of Y-direction control of the recording medium  110  detailed later. 
     The first actuators  140  and the first springs  150  support the second fixed portion  220  movably to the first fixed portion  210  and drive the recording medium  110  together with the second fixed portion  220  in the X-direction. 
     The second actuators  160  and the second springs  170  support the recording medium  110  movably to the second fixed portion  220  in each divided portion and can drive the recording medium  110  independently in each divided portion in the Y-direction. Moreover, the divided portions can be also driven in conjunction with, simultaneously with, or in parallel with each other. 
     Incidentally, the drive methods of the first actuator  140  and the second actuator  160  described above can be selected as occasion demands, in accordance with an operation speed and a drive amount, such as an electrostatic drive method using a comblike electrode, an electromagnetic method using an electromagnetic actuator, and a piezoelectric drive method using a piezoelectric effect of a ferroelectric substance. Moreover, the driving portion may be disposed in the same surface as the recording medium  110  as shown in  FIG. 2 , or may be disposed below the recording medium  110 . Moreover, the first spring  150  and the second spring  160  are not only of a linear type shown in  FIG. 2  but also of an L type or a polygonal line type so that the operation is stabilized. The aforementioned actuators are disposed to be seen from the upper surface as shown in  FIG. 2 ; however, the placement is not limited to this, and various structures can be adopted: for example, using an electrostatic actuator with a comblike electrode sterically disposed on the back surface of the medium, an electromagnetic actuator obtained by applying a magnet onto the medium substrate, or the like. 
     Next, with reference to the operations of the information recording/reproducing apparatus in the first embodiment will be described with reference to  FIG. 4  and  FIG. 5  in addition to  FIG. 1  and  FIG. 2 . Here, an explanation will be given on the operations when the first actuator  140  and the second actuator  160  are electrostatic-drive actuators using the comblike electrode.  FIG. 4  is a plan view showing the structure of the electrostatic-drive actuator.  FIG. 5  are cross sectional views showing correction of a deviation between probes and information tracks. Incidentally, in  FIG. 4  and  FIG. 5 , for convenience of explanation, the number and interval or the like of the probes, the information tracks, and the teeth of the comblike electrode are simplified. 
     In  FIG. 4 , the drive in the X-direction of the recording medium  110  is performed by the first actuators  140 . For example, if a voltage is applied to a first actuator  140   a  on the left side of the two first actuators  140   a  and  140   b  disposed on the left and right of the recording medium  110 , the opposed teeth of the first actuator  140   a  attract each other, thereby narrowing the interval of the teeth. By this, the recording medium  110  is displaced to the left side in the drawing, together with the fixed part  220 . In the same manner, if a voltage is applied to the first actuator  140   b  on the right side, the recording medium  110  is displaced to the right side. At this time, the first springs  140  keeps supporting the second fixed part  220 . 
     By the drive in the X-direction of the recording medium  110  described above, for example, the information is recorded or reproduced by the probes  130 . In other words, when the recording medium  110  is driven in the X-direction, the relative position in the X-direction between the recording medium  110  and the probes  130  is changed, so that the probes  130  scan the information tracks  120  in the X-direction, and the information can be recorded or reproduced. 
     On the other hand, the drive in the Y-direction of the recording medium  110  is performed by the second actuators  160 . The operations of the second actuators  160  are the same as those of the first actuators described above. For example, if a voltage is applied to the second actuator  160   a,  the recording medium  110  is displaced to the upper side, and if a voltage is applied to the second actuator  160   b,  the recording medium  110  is displaced to the lower side. However, the recording medium  110  is divided in the Y-direction, so that as for the drive in the Y-direction, each divided portion is independently driven by providing the second actuators  160  and the second springs  170  in each divided portion. Incidentally, the drive width (or travel distance) of the recording medium  110  may be greater than an interval d 0  between the adjacent divided portions before the drive. The collision of the divided portions for the above reason can be avoided, for example, by driving the divided portions in conjunction with each other. 
     By the drive in the Y-direction of the recording medium  110  described above, it is possible to correct the deviation between the probes  130  and the information tracks  120  caused by a thermal expansion and an angle deviation or the like. Hereinafter, an example of the thermal expansion will be shown for specific explanation. Incidentally, in the example below, for convenience of explanation, it is assumed that only the probe array  300  is thermally expanded. 
     In  FIG. 5(   a ), if there is no thermal expansion, the probes  131  and  132  are in contact with the information tracks  121  and  125 , respectively. Here, if the thermal expansion occurs in the probe array  300  due to heat generated by the operations of the apparatus or the like, as shown in  FIG. 5(   b ), the interval of the probes  131  and  132  becomes wider, and a deviation occurs between the information tracks  121  and  125 . This makes it hardly possible to correctly record or reproduce the information. Here, if the aforementioned drive in the Y-direction is performed by the second actuators  160  to displace the recording medium  110  to the left side of  FIG. 5 , the probes  131  and  132  are brought into contact with the information tracks  121  and  126 , respectively. Thus, it is possible to correctly record or reproduce the information. 
     As described above, since the recording medium  110  can be driven in the Y-direction, even if there is the deviation between the probes  130  and the information tracks  120 , the deviation is corrected, and the information can be correctly recorded or reproduced. Moreover, without limited to the aforementioned example, if there is the deviation between the probes  130  and the information tracks  120 , it is possible to take a measure by adjusting the travel distance of each divided portion. In other words, the deviation can be corrected, regardless of the cause and magnitude of the deviation or the like. Incidentally, if there is no deviation between the probes  130  and the information tracks  120 , the drive in the Y-direction may be not performed. Moreover, the drive in the X-direction and the drive in the Y-direction can be also performed simultaneously. 
     As explained above, according to the information recording/reproducing apparatus in the embodiment, it is possible to correctly record or reproduce the information. 
     Second Embodiment   
     Next, an information recording/reproducing apparatus in a second embodiment will be described with reference to  FIG. 6 .  FIG. 6  are plan views showing the structure of the information recording/reproducing apparatus in the second embodiment. Incidentally, in the second embodiment, the structure of the driving portion and its partial drive method are different in comparison to the first embodiment, and the other structures and operations are substantially the same. Thus, in the second embodiment, the different structure and operation from those of the first embodiment will be explained in details, and the explanation of the other structures and operations will be omitted as occasion demands. 
     In  FIG. 6(   a ), in the information recording/reproducing apparatus in the second embodiment, the recording medium  110  is divided into three divided portions, and each divided portion is supported by the second actuators  160  and the second springs  170 , movably to the second fixed portion  220 . 
     In  FIG. 6(   b ), the probe array  300  is supported by the first actuators  140  and the first springs  150 , movably to the first fixed portion  210 . Moreover, the probe array  300  is disposed on the recording medium  110  in  FIG. 6(   a ) (i.e. on the front side of the paper). 
     In the information recording/reproducing apparatus in the second embodiment, the drive in the Y-direction is performed by that the recording medium  110  is driven by the second actuators  160 , as in the first embodiment; however, the drive in the X-direction is performed by that the probe array  300  is driven by the first actuators  140 . As described above, even if the probe array  300  is driven instead of the recording medium  110 , there is no difference from the change in the relative position in the X-direction between the recording medium  110  and the probe array  300 . Thus, for example, the information tracks  120  can be scanned by the probes  130 , and the information can be recorded or reproduced. 
     As explained above, according to the information recording/reproducing apparatus in the second embodiment, the local complication of the apparatus is prevented by separately disposing the first actuators  140  and the first springs  150  which are one example of the “first driving device” of the present invention, and the second actuators  160  and the second springs  170  which are one example of the “second driving device” of the present invention, on the recording medium  110  and the probe array  300 . Thus, it is possible to correctly record or reproduce the information by virtue of the simple structure of the apparatus. 
     Although an explanation was given on the case where the recording medium  110  is divided into the divided portions, the probe array  300  may be divided. In this case, the same effect is achieved by driving the probe array  300  in the Y-direction. 
     The present invention can be applied not only to an information recording/reproducing apparatus which uses the polarization of the ferroelectric substance explained in the aforementioned embodiments but also to an information recording/reproducing apparatus which uses a method of recording information as unevenness into a polymer film, a phase change method of recording information by crystallizing a phase change medium, a near-field recording method using a small optical spot, or the like. 
     The present invention is not limited to the aforementioned example, but various changes may be made, if desired, without departing from the essence or spirit of the invention which can be read from the claims and the entire specification. An information recording/reproducing apparatus and method, all of which involve such changes, are also intended to be within the technical scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The information recording/reproducing apparatus and method of the present invention can be applied to an information recording/reproducing apparatus or the like for recording information onto a recording medium formed of a ferroelectric substance or the like or reproducing the recorded information, by using a plurality of probes arranged in an array form.