Optical information medium measurement method, optical information medium, recording apparatus and reproducing apparatus

An optical information medium measurement method for measuring a difference in reflectance in an optical information medium of a multilayered structure having a plurality of information layers, comprising:

• a fifth step of obtaining an apparent reflectance corresponding to a ratio between a signal light amount and an incident light amount each obtained upon reproduction of information from each layer of the optical information medium, by use of a measurement optical system;
• a second step of obtaining a thickness between layers of the optical information medium;
• a third step of obtaining a reflectance of each layer of the optical information medium;
• and
• a sixth step of obtaining a result of conversion as a difference in reflectance for a standard optical system differing from the measurement optical system, from a value indicative of the apparent reflectance obtained in the fifth step, a value indicative of the thickness between layers, the thickness being obtained in the second step, and a value indicative of the reflectance of each layer, the reflectance being obtained in the third step.

An optical information medium of a multilayered structure having a plurality of information layers,

• the optical information medium being subjected to measurement by an optical information medium measurement method comprising:
• a first step of measuring a degree of modulation of each layer of the optical information medium, by use of a measurement optical system;
• a second step of obtaining a thickness between layers of the optical information medium;
• a third step of obtaining a reflectance of each layer of the optical information medium;
• and
• a fourth step of converting the modulation degree of each layer, the modulation degree being measured in the first step, into a modulation degree for a standard optical system differing from the measurement optical system, based on a value indicative of the thickness between layers, the thickness being obtained in the second step, and a value indicative of the reflectance of each layer, the reflectance being obtained in the third step.