Abstract:
A method of examining a storage disk is proposed. The method repeats steps of: executing a writing operation and a reading operation in sequence to recording tracks at first intervals so as to check a defect in the recording tracks based on the quality of a read signal; and selecting a recording track at a position spaced by a second interval larger than the first interval from a last recording track of the sequence, the recording track being a first recording track of the recording tracks at the first intervals. The method realizes detection of a defect for recording tracks at the first intervals in a concentrated manner. A recording track is then selected at a position spaced by the second interval from the sequence. A defect can reliably be detected without increasing the total number of recording tracks selected as sample tracks.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-114892 filed on Apr. 25, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of examining a storage disk having recording tracks at predetermined intervals. In particular, the present invention relates to a method of examining a storage or recording disk incorporated in a hard disk drive, HDD, for example. 
         [0004]    2. Description of the Prior Art 
         [0005]    A method of examining a storage or magnetic recording disk is well known. The method is designed to select a recording track every predetermined pitch (distance) on the magnetic recording disk. Writing and reading operation of data is executed to the selected recording tracks. A defect is determined based on the quality of a read signal read out of the selected recording track. 
         [0006]    An increased recording density requires an increase in the number of recording tracks. If a recording track is selected every predetermined pitch (distance) in the conventional manner, the ratio of sample tracks to the total amount of recording tracks decreases. The examination suffers from an increased probability of failure to detect a defect. On the other hand, if the ratio of sample tracks to the total amount of recording tracks is to be maintained, the pitch must be reduced. The number of sample tracks increases. The throughput thus deteriorates. 
       SUMMARY OF THE INVENTION 
       [0007]    It is accordingly an object of the present invention to provide a method of examining a storage disk enabling a reliable detection of a defect without deterioration of the throughput. 
         [0008]    According to a first aspect of the present invention, there is provided a method of examining a storage disk, comprising repeating steps of: executing a writing operation and a reading operation in sequence to recording tracks at first intervals so as to check a defect in the recording tracks based on the quality of a read signal; and selecting a recording track at a position spaced by a second interval larger than the first interval from a last recording track of the sequence, the recording track being a first recording track of the recording tracks at the first intervals. 
         [0009]    The method realizes detection of a defect for recording tracks at the first intervals in a concentrated manner. A recording track is then selected at a position spaced by the second interval from the sequence. In this manner, a defect can reliably be detected without increasing the total number of recording tracks selected as sample tracks. 
         [0010]    According to a second aspect of the present invention, there is provided a method of examining a storage disk, comprising: executing a writing operation and a reading operation in sequence to recording tracks at first intervals so as to check a defect in the recording tracks based on the quality of a read signal; and executing a writing operation and a reading operation in sequence to recording tracks at second intervals so as to check a defect in the recording tracks when a defect has been detected in the recording tracks at the first intervals, the second interval being set smaller than the first interval. 
         [0011]    The method allows examination on the recording tracks at relatively short intervals after a defect has been detected. A defect can thus reliably be detected without increasing the total number of recording tracks selected as sample tracks. 
         [0012]    A specific storage disk examining apparatus may be provided to realize the method according to the first aspect. The specific storage disk examining apparatus comprises: a spindle motor; a carriage related to the spindle motor; a head supported on the carriage for writing and reading operation of data; and a controller circuit controlling the operation of the carriage so as to control the positioning of the head. The controller circuit may repeat the operation to make the head discretely move at first intervals and the operation to make the head move by a second interval, the second interval being set larger than the first intervals. 
         [0013]    A specific storage disk examining apparatus may be provided to realize the method according to the first aspect. The specific storage disk examining comprises: storage disk examining apparatus comprising: a spindle motor; a carriage related to the spindle motor; a head supported on the carriage for writing and reading operation of data; and a controller circuit controlling the operation of the carriage so as to control the positioning of the head. The controller circuit makes the head discretely move at first intervals. The controller circuit makes the head discretely move at second intervals when a defect has been detected, the second intervals being set smaller than the first intervals. 
         [0014]    Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part will be obvious from the description, or may be learned by practice of the present invention. The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments in conjunction with the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a view schematically illustrating the structure of a storage disk examining apparatus according to an example of the present invention; 
           [0017]      FIG. 2  is a schematic view schematically illustrating the arrangement of recording tracks selected as sample tracks in accordance with a method of examining a recording track according to a first embodiment of the present invention; 
           [0018]      FIG. 3  is a view showing a defect distribution map established when a sample track is taken every 2 μm pitch; 
           [0019]      FIG. 4  is a view showing a defect distribution map established when a sample track is taken every 12 μm pitch; 
           [0020]      FIG. 5  is a view showing a defect distribution map established when a group of a recording track sequence including sample tracks is taken every 20 μm pitch; and 
           [0021]      FIG. 6  is a view showing a defect distribution map established when a group of a recording track sequence including sample tracks is taken every 30 μm; and 
           [0022]      FIG. 7  is a schematic view schematically illustrating the arrangement of recording tracks selected as sample tracks in accordance with a method of examining a recording track according to a second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]      FIG. 1  schematically illustrates the structure of a storage disk examining apparatus  11  according to an example of the present invention. The storage disk examining apparatus  11  includes a spindle motor  12 . A storage disk as a test sample, namely a magnetic recording disk  13 , is mounted on the spindle motor  12 , for example. The spindle motor  12  drives the magnetic recording disk  13  at a predetermined rotation speed. 
         [0024]    A so-called carriage  14  is related to the spindle motor  12 . A head suspension  15  is attached to the carriage  14 . A flexure is bonded to the head suspension  15 . A gimbal is defined in the flexure at the front or tip end of the head suspension  15 . A flying head slider  16  is mounted on the gimbal. The gimbal allows the flying head slider  16  to change its attitude relative to the head suspension  15 . A magnetic head, namely an electromagnetic transducer, is mounted on the flying head slider  16 . 
         [0025]    When the magnetic recording disk  13  rotates, the flying head slider  16  is allowed to receive airflow generated along the rotating magnetic recording disk  13 . The airflow serves to generate a positive pressure or a lift as well as a negative pressure on the flying head slider  16 . The flying head slider  16  is thus allowed to keep flying above the surface of the magnetic recording disk  13  during the rotation of the magnetic recording disk  13  at a higher stability established by the balance between the urging force of the head suspension  15  and the combination of the lift and the negative pressure. 
         [0026]    A power source, namely a voice coil motor, VCM,  17  is coupled to the carriage  14 . The voice coil motor  17  serves to drive the carriage  14  around a vertical support shaft  18 . The rotation of the carriage  14  allows the head suspensions  15  to swing. When the carriage  14  swings around the vertical support shaft  18  during the flight of the flying head slider  16 , the flying head slider  16  is allowed to move along the radial direction of the magnetic recording disk  13 . The electromagnetic transducer on the flying head slider  16  is in this manner positioned right above a target recording track on the magnetic recording disk  13 . 
         [0027]    A driver circuit  21  is connected to the spindle motor  12 . The driver circuit  21  is designed to control the rotation of the spindle motor  12 . A driver circuit  22  is connected to the voice coil motor  17 . The driver circuit  22  is designed to control the operation of the voice coil motor  17 . The operation of the voice coil motor  17  is controlled so as to position the electromagnetic transducer. A read/write circuit  23  is connected to the electromagnetic transducer on the flying head slider  16 . The read/write circuit  23  is designed to supply a sensing current to the read element of the electromagnetic transducer. Variation in the voltage appearing in the sensing current is utilized to discriminate binary data on a recording track. The read/write circuit  23  is also designed to supply a writing current to the write element of the electromagnetic transducer. A predetermine magnetic field is generated in the write element in response to the supply of the writing current. The magnetic field acts on the magnetic recording disk  13 . Binary data is in this manner written on a recording track on the magnetic recording disk  13 . 
         [0028]    A controller circuit  24  is connected to the driver circuit  21 , the driver circuit  22  and the read/write circuit  23 . The controller circuit  24  executes an examination in accordance with a predetermined software program. A storage medium  25  such as a memory is connected to the controller circuit  24 . The predetermined software program is stored in the storage medium  25 . 
         [0029]    Next, a detailed description will be made on the operation of the controller circuit  24  in accordance with a method of examining according to a first embodiment. When a test sample, namely the magnetic recording disk  13 , is mounted on the spindle motor  12 , the controller circuit  24  instructs the driver circuit  21  to drive the spindle motor  12 . A predetermined instruction signal is supplied to the driver circuit  21 . The driver circuit  21  drives the spindle motor  12  to rotate in response to reception of the instruction signal. The magnetic recording disk  13  is driven to rotate at a predetermined rotation speed. 
         [0030]    The controller circuit  24  instructs the driver circuit  22  to position the electromagnetic transducer. A predetermined instruction signal is supplied to the driver circuit  22 . The electromagnetic transducer is positioned right above a recording track as the first sample track. The recording track as the first sample track may be either the outermost or innermost one of the recording tracks. 
         [0031]    The controller circuit  24  instructs the read/write circuit  23  to write test data. Sample binary data is supplied from the controller circuit  24  to the read/write circuit  23 . The electromagnetic transducer serves to write the test data into the first sample track based on the supplied sample binary data. 
         [0032]    The controller circuit  24  instructs the read/write circuit  23  to read data. The read/write circuit  23  discriminates binary data by using variation in the voltage appearing in the sensing current. The result of discrimination is output to the controller circuit  24 . 
         [0033]    The controller circuit  24  compares the discriminated binary data with the sample binary data supplied to the read/write circuit  23 . If the discriminated binary data coincides with the sample binary data, the controller circuit  24  determines that the reading/writing operation of data is normal. If the discriminated binary data is different from the sample binary data, the controller circuit  24  determines detection of a defect. If the defect is observed over continuous data bits of the predetermined number or larger, the controller circuit  24  determines detection of a critical defect. The defect or critical defect is registered in the memory  25  along with the identifier of the recording track, for example. Simultaneously, the angular position of the defect is specified in the record. The encoder of the spindle motor  12 , the number of the servo sector on the magnetic recording disk  13 , or the like may be utilized to specify the angular position. 
         [0034]    When the writing/reading operation has been completed for the recording track as the first sample track, the controller circuit  24  instructs the driver circuit  22  to move the electromagnetic transducer. A predetermined instruction signal is supplied to the driver circuit  22 . As shown in  FIG. 2 , the electromagnetic transducer is moved from the first sample recording track  31  in the radial direction of the magnetic recording disk  13  by a first interval D 1 . Here, the first interval D 1  is set at 1 μm, for example. The electromagnetic transducer is positioned right above the second sample recording track  32 . Writing/reading operation of the sample binary data is executed in the same manner as described above. The controller circuit  24  checks a defect in the second sample recording track  32  based on the quality of the read signal in the same manner as described above. In this manner, writing/reading operation is effected on the sample recording tracks  31 ,  32 ,  33 ,  34 ,  35  in sequence at the first intervals D 1 . A defect is checked for each of the sample recording tracks  31 - 35  based on the quality of the read signal. 
         [0035]    A first sample recording track  41  is then selected at a position spaced from the last sample track of the aforementioned sequence, namely the sample recording track  35 , by a second interval D 2  larger than the first interval D 1 . Here, the second interval D 2  is set at 56 μm, for example. The electromagnetic transducer is moved from the sample recording track  35  in the radial direction of the magnetic recording disk  13  by the second interval D 2 . The electromagnetic transducer is thus positioned right above the first sample track of the following sequence, namely the first sample recording track  41 . Writing/reading operation of the sample binary data is effected in the same manner as described above. The controller circuit  24  checks a defect in the first sample recording track  41  based on the quality of the read signal in the same manner as described above. Writing/reading operation is subsequently executed for recording tracks  42 ,  43 ,  44 ,  45  in sequence at the first intervals D 1 . A defect is checked for each of the recording tracks  42 ,  43 ,  44 ,  45  based on the quality of the read signal. In this manner, the sample tracks are selected from groups of a recording track sequence spaced from one another at the second intervals D 2 . The sample tracks are spaced from one another at the intervals D 1  in the individual recording track sequence. 
         [0036]      FIG. 3  shows an example of a defect distribution map. Sample tracks were selected every 2 μm pitch from recording tracks of 200 nm pitch. When a defect was observed over 10 continuous data bits or more, for example, it was determined as a critical defect. In  FIG. 3 , a hollow dot mark denotes a critical defect. When a defect was observed over nine continuous data bits or less, it was determined as a minor defect. In  FIG. 3 , a black diamond mark denotes a minor defect. Two textural scratches  47 ,  48  can be observed in the defect distribution map of  FIG. 3 , for example. If a textural scratch is observed on the magnetic recording disk  13 , the magnetic recording disk  13  is excluded as an inappropriate product. In general, the surface of the substrate is subjected to texturing process in the process of making the magnetic recording disk  13 . A piece of cloth is urged against the surface of the rotating substrate in the texturing process. Abrasive grains are supplied between the cloth and the substrate. The piece of cloth reciprocates in the radial direction of the substrate. A textural scratch is caused due to the abrasive grains of relatively large size. The textural scratch appears as a wavy line extending in the circumferential direction of the substrate. 
         [0037]      FIG. 4  shows another example of a defect distribution map. The magnetic recording disk  13  having a defect of  FIG. 3  was examined so as to make this defect distribution map. A sample track was selected every 12 μm. The textural scratch was obviously fragmented. One critical defect was observed. Four successive minor defects  49  were observed. 
         [0038]      FIG. 5  shows another example of a defect distribution map. The magnetic recording disk  13  having a defect of  FIG. 3  was likewise examined so as to make this defect distribution map. A recording track sequence was taken every second interval D 2  of 20 μm. The individual recording track sequence comprised two recording tracks spaced from each other at the first interval D 1  of 2 μm. In other words, the total number of the recording tracks selected as sample tracks was set equal to that of the recording tracks of 12 μm pitch. One critical defect  51  and four minor defects  52  near the critical defect  51  were observed. It has been confirmed that a criterion is clarified for detection of a defect without changing the total number of the sample tracks. 
         [0039]      FIG. 6  shows another example of a defect distribution map. The magnetic recording disk  13  having a defect of  FIG. 3  was likewise examined so as to make this defect distribution map. A recording track sequence was taken every second interval D 2  of 30 μm. The individual recording track sequence included three recording tracks spaced from one another at first intervals D 1  of 2 μm. In other words, the total number of the recording tracks selected as sample tracks was set equal to that of the recording tracks of 12 μm pitch. One critical defect  51  and eleven (11) minor defects  53  near the critical defect  51  were observed. In addition, six of the minor defects  53 , namely minor defects  54 , were observed closest to one another in any other cases. It has been confirmed that a textural scratch can be detected with high accuracy in accordance with such a criterion. It has been observed that a criterion is further clarified for detection of a defect without changing the total number of sample tracks. 
         [0040]    Next, a detailed description will be made on the operation of the controller circuit  24  in accordance with a method of examining according to a second embodiment. Writing/reading operation of data is effected on the recording tracks  61 ,  62 ,  63  in sequence at first intervals R 1 . Here, the first interval R 1  is set at 12 μm, for example. A predetermined instruction signal is supplied from the controller circuit  24  to the driver circuit  22  so as to position the electromagnetic transducer in the same manner as described above. A defect is checked for each of the recording tracks  61 - 63  based on the quality of the read signal in the same manner as described above. 
         [0041]    If a defect  64  is detected in the recording track  63 , writing/reading operation is effected on recording tracks  65 ,  66 ,  67 ,  68  in sequence at second intervals R 2  smaller than the first intervals R 1 . Here, the second interval R 2  is set at 1 μm, for example. A defect is checked for each of the recording tracks  65 - 68  based on the quality of the read signal. If defects are continuously detected in the recording tracks  63 - 68 , the controller circuit  24  determines the existence of a textural scratch. 
         [0042]    It should be noted that the aforementioned first interval D 1 , second interval D 2 , first interval R 1  and second interval R 2  can appropriately be determined depending on the amplitude and/or the size of a textural scratch. 
         [0043]    The turn of the embodiments is not a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.