FOCUS CONTROL DEVICE, FOCUS CONTROL METHOD, FOCUS CONTROL PROGRAM, AND RECORDING MEDIUM CONTAINING THE FOCUS CONTROL PROGRAM

摘要

There are provided a focus control device, a focus control method, and a focus control program capable of stably reaching a desired layer for performing focus serve even when an optical recording medium has a plurality of information layers having different reflection factors. An information recording medium containing the focus control program is also provided. The focus control device includes: a microcomputer for measuring a reflection factor in the information layer according to an electric signal generated by a photo-detector; a microcomputer or a servo signal processing unit used when the reflection factors of the information layers measured by the microcomputer are different, for setting an amplification ratio of the electric signal generated by a photo detector for each of the information layers having different reflection factors; and an actuator used when focusing in a desired information layer by moving an objective lens for focusing in the direction having less number of other information layers.