Abstract: A recording device (1T or the like) is provided with (i) recording elements (50, 40) for recording data by irradiating a recording medium with laser beams; (ii) driving members (33T, 33F, 55T, 55F, 54) for performing tracking process or focusing process; (iii) a servo elements (31T, 31F) for automatically controlling the driving members based on an error signal; (iv) specifying elements (21, 22) for specifying an area where a recording medium characteristic (core eccentricity or the like) is not good, based on a high frequency component included in the error signal; and (v) a control unit (10) for (v-i) controlling the servo unit to change the gain in the automatic control, and for (v-ii) controlling the recording elements to change the recording power of the laser beams, in the specified area.

Abstract: A recording device (1T or the like) is provided with (i) recording means (50, 40) for recording data by irradiating a recording medium with laser beams; (ii) driving means (33T, 33F, 55T, 55F, 54) for performing tracking process or focusing process; (iii) a servo means (31T, 31F) for automatically controlling the driving means based on an error signal; (iv) specifying means (21, 22) for specifying an area where a recording medium characteristic (core eccentricity or the like) is not good, based on a high frequency component included in the error signal; and (v) a control means (10) for (v-i) controlling the servo means to change the gain in the automatic control, and for (v-ii) controlling the recording means to change the recording power of the laser beams, in the specified area

Abstract: There is provided an optical pickup which comprises a light source, an objective lens for converging a beam from the light source onto an optical disc, a diffraction grating for passing a beam returning from the optical disc, a photo-detector for receiving returning beams passing through the diffraction grating. The diffraction grating is divided into two areas, each area including alternatively arranged first diffraction grating pattern and second diffraction grating pattern.