Patent ID: 7639593

Claim:
A multi-layer optical recording medium having at least three recording layers stacked with a transparent spacer layer interposed between each layer and the next layer, the multi-layer optical recording medium comprising: a signal intensity measuring region formed within a recording region of the multi-layer optical recording medium and divided into a plurality of areas, formed such that a reflectivity of each of the recording layers in an area having an identical address is allowed to have at least three different levels, and a reflectivity measuring region in which positions of inner circumference ends of the recording layers facing an inner hole are sequentially offset so that the recording layer closer to a light incident surface is more remote from the inner hole so as to enable a reproducing beam to illuminate and its reflection, a signal light beam, to exit at least one recording layer among the plurality of recording layers excluding the recording layer on the nearest side to incident light, through the transparent spacer layer and without passing through the other recording layers, wherein, in the signal intensity measuring region, different combinations of the recording layers and the reflectivities are assigned to the areas having different addresses, and the recording layers are areas capable of recording data.