In situ media defect image analysis
The present invention is a method or apparatus configured for analyzing a data storage device containing a transducer head positionable adjacent a data storage media surface. First, a defect is detected in a region of the surface. Two or more readback signals are obtained, each received during a respective pass of the transducer head adjacent the defective region. The signals are then combined to define a category for the defective region, either automatically or by visual examination of an image. Preferably, all of the read signals are received from the transducer head while the data storage device remains sealed in a substantially opaque chamber. That way, the media defects of an entire population of data storage devices can be analyzed quickly, disassembling the drives for direct visual analysis only on a selective basis.
1. A method comprising imaging a characteristic size of a defective region of a data storage medium by combining a plurality of data readback signals received from different tracks adjacent the defective region, and indicating that the defective region is unreliable if a ratio defined by a size of a portion of the defective region with a less-than-expected readback signal strength compared to a total size of the detective region is greater than a preselected threshold.
2. The method of claim 1 further comprising categorizing the defective region by comparing the characteristic size of the defective region to a plurality of predefined category profiles.
3. The method of claim 2 wherein the categorizing step comprises identifying the defective region as likely being characteristic of a scratch.
4. The method of claim 1 wherein the imaging step comprises representing an array of data points each having independent coordinates X and Y with respect to the data storage media.
5. The method of claim 4 wherein the imaging step comprises representing an array of data points wherein each X and Y coordinate is associated with a corresponding Z coordinate relating to a strength of the associated readback signal.
6. The method of claim 2 wherein the categorizing step comprises identifying the defective region as likely being characteristic of corrosion.
7. The method of claim 1 , further comprising:
modifying a list of bad sectors in a manner that depends upon the imaging step; and
retaining the modified list in a memory.
8. A data storage apparatus comprising a list of bad sectors that is modified according to the method of claim 7 and stored in a memory.
9. The method of claim 2 , further comprising:
assigning a value to each of the defective regions according to the categorizing step; and
reworking the data storage medium if an aggregation of the assigned values exceeds a predetermined threshold.
10. The method of claim 1 in which the imaging step comprises receiving all of the plurality of readback signals from a transducer head of a sealed data storage apparatus in which the medium is rotated.
11. The method of claim 3 wherein the categorizing step identifies the defective region as likely being characteristic of a scratch if the characteristic size comprises a length that is greater than a width by a factor of about 2.5.
12. An apparatus comprising:
a data storage medium comprising a defective region; and
means for assigning a category for the defective region by combining a plurality of data readback signals received from different tracks adjacent the defective region, wherein the means for assigning comprises means for generating a topographical image of the defective region of the media surface.
13. The apparatus of claim 12 in which the means for assigning comprises defining a profile for each of at least 3 categories defining a set that includes the category assigned for the defective region.
14. The apparatus of claim 12 in which the means for assigning is completed while the combination of readback signals has been compared against at most 30 profiles each corresponding to a respective category, die assigned category being one of the respective categories.
15. The apparatus of claim 12 in which the means for assigning comprises a category identifier indicating whether the defective region is likely to contain a scratch.
16. The apparatus of claim 12 in which the means for assigning is configured to receive all of the plurality of read signals from the transducer head while the media storage and transducer head are sealed in a substantially opaque chamber.