近場光碟機的空氣軸承分析與實驗

Abstract

近場光學原理的應用得以大幅提升光碟片的容量。但因近場光學必須在極接近反射面處，約五十奈米的距離做讀取的動作，所以採用了類似硬碟機飛行讀寫頭的架構，利用飛行讀寫頭與光碟片間的空氣軸承來維持極低的穩定飛行高度。但主軸馬達的高速轉動引起碟片的振動、音圈馬達尋軌時造成負荷臂的變形和讀取頭與光碟片間的流場產生變化，都會影響飛行姿態與高度。本研究旨在探討近場光碟機飛行讀寫頭與光碟片介面之磨潤問題，首先建立懸吊組件與音圈馬達之動態分析，了解音圈馬達尋軌時所造成的懸吊組件之變形；再進行主軸馬達與光碟片之動態分析，最後由修正雷諾方程式建立飛行讀寫頭與光碟片介面之簡化流場模型，分析飛行高度與姿態的變化。本研究並且執行實驗，利用雷射都卜勒干涉儀的飛行高度量測數據比較模擬結果。

A near-field optical disk drive uses near-field optics to read/write disk data with a flying height at about 50 nm. However, there are some reasons that affect the flying height and attitude, such as disk vibration due to rotation of the spindle motor, deformation of the load-arm causing by a voice coil motor (VCM), fluid flow between the flying head and disk. This research aims to investigate dynamics of the air bearing between the flying head and disk. First, dynamic models of the suspension assembly and VCM are established to calculate deformation of the suspension assembly during seeking. This study employs a simplified fluid flow model based on a modified Reynolds equation for the air bearing to calculate variation of flying height. Finally, simulation results are compared by measurement results using a laser Doppler vibrometer.