| 摘要 |
An objective lens has an actuator base and a lens holder for supporting an objective lens. The lens holder has a shaft hole. A shaft is disposed on the actuator base and fitted to the shaft hole. A cover is attached to the actuator base so as to cover the lens holder in a manner that the cover comes into contact with or comes close to the top face of the shaft. Protrusions are disposed on an actuator base opposing face and a cover opposing face of the lens holder without contacting the shaft. When the protrusions are contacted with the actuator base and the cover, a predetermined gap is formed between the lens holder and the actuator base and between the lens holder and the cover, the gap is communicated with a space in the cover through the side of the protrusions.
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