Patent ID: 7349320

Claim:
An optical-disk drive device which operates at a numerical aperture that corresponds to each of a plurality of optical disks, comprising: a light source; a branching element which allows a luminous flux that is emitted from said light source to branch off to a first luminous flux and a second luminous flux; a first detector which receives the first luminous flux that is obtained from the branching by said branching element; a controller which controls the quantity of light that is emitted by said light source, according to the quantity of light that is received by said first detector; and a second detector which receives the second luminous flux after the second luminous flux is reflected by an optical disk, wherein: said first detector includes a first detection area in which an inner luminous flux of the first luminous flux is received, and at least one second detection area in which an outer luminous flux of the first luminous flux is received; and said controller switches, from a first control state in which the quantity of light that is emitted by said light source is controlled based on the quantity of light that is received in said first detection area, to a second control state in which the quantity of light that is emitted by said light source is controlled based on the quantity of light that is received in said first detection area and said second detection area, and vice versa.