Patent ID: 7933184

Claim:
A multilayered optical disc having N (N is an integer at least equal to 3) information recording layers of rewritable or recordable type; wherein each of the information recording layers at least includes a test area to adjust conditions for recording and reproduction; wherein the test area in each layer includes a plurality of small segments; wherein the small segments include first small segments for test recording and second small segments where information is not test recorded; wherein when a minimum value of an interlayer distance of the information recording layers is d, a refractive index of a space layer between the recording layer is n, an opening ratio of an objective lens of an optical pickup used in recording/reproduction is NA, a track pitch is Tp, a radial position of the small segment is r, and a length of each small segment in a circumferential direction of the optical disc does not exceed [d×(NA/n)/{1−(NA/n)^2}^(1/2)]/Tp×(2πr).