OPTICAL HEAD DEVICE, RECORDING AND/OR REPRODUCING DEVICE AND RECORDING AND/OR REPRODUCING METHOD

摘要

PROBLEM TO BE SOLVED: To provide an optical head and a recording and/or reproducing device which are simple and small sized as well as a recording and/or reproducing method by which the spherical aberration of a condensing spot is corrected by detecting a thickness error of a light transmission layer while information recording/reproducing is precisely performed. SOLUTION: A focal error with a medium surface 106a is detected by receiving a first reflection light 107a reflected on the medium surface 106a, and a focal with the surface of the light transmission layer 106a is detected by receiving a sound reflection light 107b reflected on the surface of the light transmission layer 106b which is formed on the medium surface 106a. A collimator lens 103 is moved in accordance with the focal error with the surface of the light transmission layer 106a.