抄録
We have already reported that the signal of single frequency pattern can be used for focus signal. A pick up method of focus signal using page data is proposed in this paper. We tried 3 types of mask pattern such as large circle, small circle, and straight line. Single frequency signal can be picked up using mask of small circle from page data. As the results, this signal can be used for focus servo signal and this method is feasible because of no additional patterns for data page or no additional optical elements.
