運用四象儀量測於近場光碟機讀寫頭之飛行高度控制

Abstract

為了實現近場光學以提昇資料的儲存容量與密度，近場光碟機的飛行讀寫頭機構必須使滑動片在碟片上方以穩定的高度飛行。由於軌距及飛行高度達到奈米等級，故讀寫頭的控制精度也必須相對提高。本研究利用壓電材料驅動讀寫頭的定位，使用四象儀光偵測器，並運用光槓桿原理以及加、減法運算電路，量測讀寫頭與碟片間的相對位置變化。為了使讀寫頭跟上近場光碟片瞬間的振動變形，採用對模型之不確定性及外界干擾具有強健性的順滑模態控制，以克服系統的非線性與外界干擾，即時調整讀寫頭的飛行高度，保持穩定的飛行高度。

To realize near-field optics and hence increase storage capacity and density in near-field optical disk drives, the flying pickup head has to enable the slider to fly at a stable height above the disk surface. Since both the precision of track pitch and the flying height reach nanoscale, it remains to increase the motion accuracy of a pickup head. In this study, a PZT bender is used as an actuator of the pickup head while quadrant photodetectors are used as sensors. Based on an optical lever method and addition-and-subtraction operations in op-amp circuits, the relative position variation between a disk and a pickup head is measured. This study designs a sliding mode controller inherited with robust properties to deal with model uncertainty and external disturbances, so as to maintain stable flying height.