| 摘要 |
PROBLEM TO BE SOLVED: To properly detect and control a microscopic interval between first and second objects, particularly a microscopic interval between the optical head 3 and the recording medium 9 of an optical recording deice. SOLUTION: The optical head 3 is provided with a solid immersion lens 32 serving as a near-field light generating means and a laser beam RL for effecting record of data on the recording medium 9 and reproduction of the data, etc., is incident on the solid immersion lens 32 from a vertical direction. Interval-detecting laser beam L1 and L2 having respective incident anglesθ1 andθ2 are also incident on the solid immersion lens 32 and are converged at the center position of the bottom surface of the solid immersion lens 32. As a result, near-field light beam N1 and N2 of different ranges as well as a recording near-field light beam RN seep from the bottom surface of the solid immersion lens 32 in the direction of the recording medium 9. When the recording medium 9 is present within the ranges of the near-field light beams N1 and N2, the near-field light beams are coupled with the recording medium 9 and propagating light beams result, so that the interval can be detected from changes in quantity of light caused by the coupling.
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