| 摘要 |
An optical pickup (100) includes: an irradiating device (101) for irradiating a laser beam (LB); a first light focusing device (104) for focusing the laser beam on the recording medium (10); a collimator device (102) which is disposed on the optical path between the irradiating device and the first light focusing device and which can be displaced along the optical path of the laser beam; a splitting device (103) which reflects one portion of the laser beam and transmits therethrough another portion of the laser beam; a light receiving device (111) for receiving the reflected one portion of the laser beam; and a second light focusing device (112) for focusing, on the light receiving device, the reflected one portion of the laser beam, the light receiving device and the first light focusing device is disposed at a position at which rate of change in light density of the laser beam on the first light focusing device before and after displacement of the collimator device is substantially the same as that on the light receiving device before and after the displacement of the collimator device.
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