Patent ID: 8437233

Claim:
An optical recording/reproduction method comprising: an illumination and light reception step for directing laser light through an objective lens while displacing the objective lens in the focusing direction to illuminate one of the recording layers of a multilayered optical disc having k recording layers (k being an integer equal to or greater than two) with a focused spot and receiving light reflected from the multilayered optical disc with a light receiving element; a signal processing step for generating a spherical aberration control signal for the focused spot from a received light signal output from the light receiving element on a basis of the received light; and a spherical aberration control step for controlling the spherical aberration according to the spherical aberration control signal; wherein the signal processing step includes a step of obtaining amplitude information about a focus error signal detected during the step of displacing the objective lens in the focusing direction; a step of calculating, from a ratio of an amplitude value of the focus error signal detected just after leaving a focal position of an arbitrary s-th recording layer of the multilayered optical disc (s being an integer satisfying (1≦s≦k)) and an amplitude value of the focus error signal detected just before passing through a focal position of an arbitrary t-th recording layer of the multilayered optical disc (t being an integer satisfying (1≦t≦k, t≠s)), an optimal amount of spherical aberration for the t-th recording layer; and a step of generating the spherical aberration control signal on a basis of the calculated optimal amount of spherical aberration.