A light-pickup device has a constitution in which a microcomputer executes control for applying offset voltage to a focus error signal by changing over connection of an FE offset circuit when a servo-processor kicks focus drive voltage for acceleration in order to change over information recording layers of an optical disk having two information recording layers on a plane thereof. The optical media make use of certain formulations of color forming coatings described herein. The outer balloon has an unstretched diameter equivalent to the minimum deployment diameter and the inner balloon has an unstretched diameter equivalent to the maximum deployment diameter. In one embodiment, the other node may be a logically nearby node to the compute node. An RF powder 11 is used in a powder form, wherein each particle 11a in the powder has an integrated circuit 13 formed on a substrate 12, an insulating layer 14 formed on the integrated circuit, and an antenna element 15 formed on the insulating layer. The heat insulation plates are set up below the top support.