Patent ID: 6674696
Filing Date: 2004-01-06
Classification: G11B

Abstract:
A focus controlling apparatus for focusing a light beam and positioning the focused light beam onto a signal recording layer of a signal recording media, comprising:a light beam focusing means having a numerical aperture of 0.6 or more; a focusing controlling means for providing a focus control to position the light beam focused by the light beam focusing means onto the signal recording layer of the recording media; and an offset adjusting means for adjusting an offset between the focused light beam focus positioned by the focus controlling means and the signal recording layer of the recording media depending upon an RF signal read from the recording media; wherein the offset adjusting means periodically moves the light beam focusing means within a predetermined optical-axial range to adjust the offset depending upon an amplitude of a signal read from the recording media at either end of the optical-axial range; and the light beam focusing means moves depicting a sine waveform.