<p>An optical pickup (100) comprises a light source (101) for irradiating a recording medium (1) with light (L), a solid immersion lens (108) arranged in the optical path of irradiated light in proximity to the surface of the recording medium, a spot size enlarging means (102) arranged at a part in the optical path for enlarging the size of a spot formed on the bottom of the solid immersion lens by a part of irradiated light, and a gap error signal generating means (110) for controlling the gap between the above-mentioned surface and the solid immersion lens by receiving the light, which is caused by the part of the light and is reflected from the above-mentioned bottom.</p>
