| 摘要 |
PROBLEM TO BE SOLVED: To detect sensitivity of a focus servo mechanism. SOLUTION: An objective lens 4d is moved in its optical axis direction via a focus servo mechanism, when the objective lens 4d is moving, it is detected that the light beam emitted from an optical source 4a condensed with the objective lens 4d at the surface of an optical disc 101 arranged against an optical pickup device 4 is focuses and that the light beam is focused at the signal recording surface of the optical disc 101, the time required for detection of focusing condition in the other area is detected after the focusing condition in any one of the surface of optical disc 101 or signal recording surface thereof is detected, this time is compared with the predetermined time and the sensitivity of focus servo mechanism is detected on the basis of the result of comparison.
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