For example, in the information recording medium, such as a CD and a DVD, as described in patent documents 1 and 2 or the like, there are developed a multilayer type or dual layer type optical disc and so on, in which a plurality of recording layers are stacked or laminated on the same substrate. Then, in the information recording apparatus, such as a CD recorder, for recording information onto such a dual layer type optical disc, the information is recorded into a recording layer located on the front or the closest side as viewed from the emission or irradiation side of laser light (referred to as an “L0 layer” in this application, as occasion demands), in a rewritable method or irreversible change recording method by using heat or the like, by focusing the laser light for recording on the L0 layer. Moreover, the information is recorded into a recording layer located on the rear or the farthest side of the L0 layer as viewed from the irradiation side of the laser light (referred to as an “L1 layer” in this application), in a rewritable method or irreversible change recording method by using heat or the like, by focusing the laser light on the L1 layer through the L0 layer.
Moreover, in this type of optical disc or the like, the optimum power of a recording power is set by an OPC (Optimum Power Calibration) process, depending on the type of the optical disc, the type of the information recording/reproducing apparatus, the recording rate and so on. That is, the calibration for the recording power is performed. By this, it is possible to realize an appropriate recording operation in response to variation in characteristics of the information recording surface of the optical disc. For example, if the optical disc is loaded and a writing command is inputted, data for test writing is recorded into an OPC area with sequentially changing optical intensity, so that a so-called “test writing process” is performed. In particular, according to the patent document 1, the OPC area is provided for each of the two recording layers, and a technology of performing the OPC process for each of the two layers is disclosed.
Patent document 1: Japanese Patent Application Laying Open NO. 2000-311346
Patent document 2: Japanese Patent Application Laying Open NO. 2001-23237