Patent ID: 8811140

Claim:
A recordable optical disk comprising: four recording layers configured to be provided over a disk substrate; and an optically-transparent layer configured to be formed on a laser-incident surface side, wherein four test areas for laser power control are each provided in an inner circumference side area closer to an inner circumference than a data zone in which user data is recorded in a respective one of the recording layers, the test areas of a first pair and the test areas of a second pair are so disposed as to be prevented from overlapping with each other in a layer direction if two test areas closer to a disk outer circumference, of the four test areas, are defined as the first pair and two test areas closer to a disk inner circumference, of the four test areas, are defined as the second pair, the two test areas of the first pair have the same consumption direction of the test area, and are so disposed that parts to be used next in the test areas are prevented from overlapping with each other in the layer direction, the two test areas of the second pair have the same consumption direction of the test area opposite to the consumption direction of the test area in the first pair, and are so disposed that parts to be used next in the test areas are prevented from overlapping with each other in the layer direction, the optical disk has a diameter of 12 cm, each of the test areas is formed with a radial width of about 250 μm in a range of 22.5 mm to 24.0 mm as a range of a radial position of the optical disk, the recording layers are so formed that a relative error in a radial position of the recording layers is within a tolerance of about 150 μm, an innermost circumference radial position of the test areas of the first pair and an outermost circumference radial position of the test areas of the second pair are disposed at positions that do not overlap with each other in the layer direction and have a gap distance of at least about 150 μm along a radial direction if the relative error in the radial position is zero, the two test areas of the first pair are formed at positions that do not overlap with each other in the layer direction and have a gap distance of at least about 50 μm along the radial direction if the relative error in the radial position is zero, and the two test areas of the second pair are formed at positions that do not overlap with each other in the layer direction and have a gap distance of at least about 50 μm along the radial direction if the relative error in the radial position is zero.