OPTICAL RECORDING MEDIUM PRODUCTION METHOD, OPTICAL RECORDING MEDIUM, OPTICAL INFORMATION DEVICE, AND INFORMATION REPRODUCTION METHOD

摘要

Quality of a servo signal and a reproduction signal can be improved. The shape thicknesses tr1, tr2, ...,trN of a cover layer having a refractive index of nr1, nr2, ..., nrN, and first to (N-1)th intermediate layers are converted to thicknesses t1, t2, ..., tN of layers having a predetermined refractive index (no), which can cause the same spread amount as the optical beam spread amount caused by the thicknesses tr1, tr2, ..., trN. The difference (DEF) between the sum of thickness ti to thickness tj, and the sum of thickness tk to thickness tm is 1 µm or more (i, j, k, and m may represent any natural numbers which satisfy i=j