| 摘要 |
PROBLEM TO BE SOLVED: To estimate the amount of birefringence resulting from the influence of the stress applied to an optical disk when rotation. SOLUTION: A central processing unit (47) measures a signal acquired by reflecting from a reference optical disk by an optical pickup while moving optical pickups (15, 17) of a non-polarized optical system and a polarized optical system toward the circumference from an interior of the reference optical disk in a state of rotating at a desired rotation speed to be measured, and corrects the error and stores the signal as a reference signal. Then, the CPU measures the signal acquired by reflecting from a measurement object optical disk by both optical pickups while moving these optical pickups toward the circumference from the interior of the measurement object optical disk in a state of rotating at a desired rotation speed to be measured. Then, the amount of birefringence of measurement object optical disk is estimated from a falloff degree of a signal acquired by the measurement of the reference signal. COPYRIGHT: (C)2004,JPO&NCIPI
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