Patent ID: 8228774

Claim:
An optical information medium measurement method for measuring a reflectance in an optical information medium of a multilayered structure having “N” information layers (2≦N, N: an integer), comprising: an acquiring step of acquiring a thickness between layers of the optical information medium in a measurement device; a detecting step of detecting a reflected light amount when focusing on an i-th layer, and calculating a ratio of the detected reflected light amount versus an incident light amount as an apparent reflectance in the measurement device; and a calculating step of calculating a reflectance of each of the layers of the optical information medium in the measurement device, wherein when it is assumed that the reflectance of the i-th layer (1≦i≦N, i: an integer) is represented by R i , a thickness between the i-th layer and a j-th layer (1≦j≦N, i≠j, j: an integer) acquired in the acquiring step is represented by d ij , a refractive index between the i-th layer and the j-th layer is represented by n, an apparent reflectance of each of the layers of the optical information medium determined in the detecting step is represented by S i , an area of a light receiving section in the measurement optical system is represented by S pd , a magnification of a detection system in the measurement optical system is represented by M, a normalize light receiving part size in the measurement optical system is represented by Sd(Sd=S pd /M 2 ), a numerical aperture in a measurement optical system is represented by NA, and a value θ satisfies a relation of sin θ=NA/n and falls within a range from 0 to π/2, “N” equations are established so as to satisfy an equation: S i =R i +Sd·[ΣR j /{π(2 ·d ij ·tan θ) 2 }] (Σ: addition of integers from 1 to N in a case of j≠i, with regard to j), and the reference R 1 is obtained in such a manner that the “N” equations for the apparent reflectance S i are solved with regard to the reflectance R i calculated in the calculating step.