Optical disks such as DVDs (digital versatile disks) and Blu-ray Discs (registered trademark) are given multiple recording layers for the purpose of increasing their capacity. As these disks now have multiple layers, a tracking control method is known whereby data is recorded to or played back from the recording layers using guide tracks provided in a layer different from the recording layers. For example, optical drive devices, etc., are available that perform tracking control using light of 390 nm to 420 nm in wavelength (blue) to a guide tracking layer having grooved guide tracks provided in it, and record data to one of multiple recording layers using light of 650 nm to 680 nm in wavelength (red) (refer to Patent Literature 1, for example).
Even with such optical drive devices that record data to a multi-layer disk having multiple recording layers, it is important to calculate an optimal recording power by test-writing to each recording layer.
For example, assume that a PCA (power calibration area) used for test-writing purposes is provided in the same area of each recording layer in a multi-layer disk and that user data is recorded to fill the recording layers of the multi-layer disk one by one from the recording layer closest to the objective lens of the optical pickup. In this case, after the OPC (optimized power control) process is performed as a calibration process to adjust and optimize the intensity level (power level) of recording laser light in a given recording layer, the PCA is filled with dummy data, so that the OPC process in the next recording layer will be performed under the same conditions applicable to the user data area, because doing so is considered effective in ensuring that data is recorded in a stable manner (refer to Patent Literature 2, for example).
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