Patent ID: 8218418

Claim:
An optical information medium measurement method for measuring a degree of modulation in an optical information medium of a multilayered structure having a plurality of information layers, the optical information medium measurement method comprising: a first step of measuring, via a measurement optical system having a normalize light receiving part size of Sd, a modulation degree of each respective information layer of the plurality of information layers of the optical information medium; a second step of obtaining a thickness between the plurality of information layers of the optical information medium; a third step of obtaining a reflectance of each respective information layer of the plurality of information layers of the optical information medium; and a fourth step of respectively converting the modulation degree of each respective information layer, as measured in the first step, into a respective modulation degree for a standard optical system having a normalize light receiving part size of Sdn differing from the normalize light receiving part size of Sd of the measurement optical system, based on (i) a value indicative of the thickness between the plurality of information layers, as obtained in the second step, and (ii) a value indicative of the reflectance of the respective information layer, as obtained in the third step.