Optical information recording medium, optical measuring method and optical information recording/reproducing method

摘要

An optical information recording medium having two or more information layers, wherein the irradiation of either the information layer with a laser beam converging thereon causes information signals to be recorded or reproduced; the nearer positioned information layer than the farthest information layer as viewed from the incidence side of the laser beam has a recording layer varying between two optically detectable states, and 0<=|T_c-T_a|/T_c<=0.1 where T_c is the transmittance of the nearer positioned information layer when the recording layer is in state (a) and T_a, the transmittance, when it is in state (b). This makes possible accurate accurately recording and reproduction of information onto and out of the farther information layer irrespective of whether or not any information is recorded on the nearer information layer.