| 摘要 |
A conventional mechanical precision measuring device is used effectively in the measurement of the eccentricity of a high density optical disc. A DVR optical disc 2 comprises a pattern 4 of fine depressions and protrusions conformed to the intended format of the disc (a first depressions and protrusions: pits and/or grooves) formed within an information recording area 6 of the disc, as well as a pattern 8 of fine depressions and protrusions for measuring the eccentricity (a second depressions and protrusions), which is formed in an area other than the information recording area 6 , and is formed in accordance with a CD format having lower recording density than that of the format defined for the DVR optical disc 2 . By using this pattern 8 of fine depressions and protrusions for mechanical detection, conventional mechanical precision measuring devices designed for the CD family can be used as it is, for measuring the eccentricity (mechanical precision) of the DVR optical disc 2.
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