Information recording and reproducing apparatus and method for controlling positions of optical pickup device and objective lens used for the apparatus

An information recording and reproducing apparatus comprising:

• an optical pickup device having:
• a light source which outputs a light beam having a predetermined wavelength;
• an objective lens which focuses the light beam from the light source in a recording layer of a recording medium and which captures the light beam reflected in the recording layer;
• an optical detector which converts to an electrical signal the light beam reflected in the recording layer, the light being captured by means of the objective lens and which outputs an electrical signal of a magnitude which corresponds to optical intensity;
• and a lens position control unit which controls a position of the objective lens so that a distance between the objective lens and the recording medium coincides with a focusing position of the light beam focused in the recording medium by means of the objective lens, based on an output of the optical detector;
• an output signal processor circuit which captures information recorded in the recording medium from a reflection light beam from the recording medium, the reflection light beam being detected by the optical detector;
• and
• a main control unit which controls operations of the optical pickup device and the output signal processor circuit,
• wherein the lens position control unit is such that a range for detecting an output from the optical detector for controlling a position of the objective lens is set in a range which is wider than a range in which a magnitude of an error signal for controlling a position of the objective lens is changed by a leakage signal component generated when the objective lens is moved in a direction which crosses a track of the recording medium.