Patent ID: 7345973

Claim:
Writable optical disc for use in a recording device with an objective lens having an aperture NA comprising a plurality of recording layers L 0 , . . . , Ln−1 separated by a spacer material each time, each of the recording layers comprising an optimum power calibration area, wherein at least the optimum power calibration areas of the layers L 0 , . . . , Ln−2 or L 1 , . . . , Ln−1 have a first portion with an average reflection value representative of a recorded layer, the optimum power calibration areas of each recording layer L 0 , . . . , Ln−1 have a second portion with an average reflection value representative of an unrecorded layer, and said optimum power calibration areas partially overlap such that the first portions of each pair of consecutive recording layers Lk, Lk+1 form a step with a minimum step size w k,k+1 of w k , k + 1 = 2 ⁢ ɛ + NA n m 2 - NA 2 · Δ k , k + 1 , wherein ε denotes the maximum radial misalignment of each recording layer, Δ k,k+1 denotes the thickness of the spacer material between the consecutive layers Lk and Lk+1, and n m is the refractive index of the spacer material, and wherein the first portions of said plurality of recording layers have the form of a staircase.