Optical disk, an optical disk barcode forming method, an optical disk reproduction apparatus, a marking forming apparatus, a method of forming a laser marking on an optical disk, and a method of manufacturing an optical disk

An optical disk comprising:

• a first recording area where main information is recorded;
• a second recording area, where barcode-like marks each of which has a strip-like configuration in a radius direction and which are disposed in a circumferential direction, are recorded as a sub information, said second recording area being formed in a circumferential direction, wherein;
• said first recording area contains at least a lead-in area from which data recording starts, and a control data area which represents a physical property of the optical disk;
• said second recording area is disposed inside said control data area on said first recording area and said second recording area is overlapped with the said lead-in area;
• said sub information is PE-modulated to be further RZ-modulated to be recorded on said second recording area so that a width of said barcode-like marks is half or less than a period of said barcode-like marks;
• there is a certain area where said barcode-like marks are not recorded, within said second recording area;
• and
• there is a guard band area on which at least an address is recorded, between at least a portion of said control data area and the second recording area
• wherein an identifier which indicates whether or not the barcode-like marks are present within the second recording area is provided in the control data area.