光碟機讀取頭聚焦機構設計與分析

The Design and Analysis of the Focusing Mechanism for a DVD Pickup Head

彭仁傑(Ren-Jay Peng)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(1999年)

摘要

本論文研究針對現有光碟機讀取頭之聚焦機構提供創新之改良設計，即以曲率微調反射薄膜之設計取代現有光碟機讀取頭之矩形反射玻片，優點是能夠藉由輕微改變曲率微調反射薄膜的曲率半徑而使雷射光更精確地聚焦於光碟片上，能夠克服光碟片高速旋轉時軸向的偏擺，改善傳統讀取頭的聚焦性能。
曲率微調反射薄膜是圓形的薄膜結構，其表面是不透光的反射層，背面則有加強結構及導電微線圈的設計，當導電微線圈通入電流時和外界之永久磁場產生感應電磁力驅使反射薄膜中央區域變形成有適當曲率半徑的拋物面，使入射之雷射光經過反射薄膜表面後收斂至聚焦交點。本文內容著重於曲率微調反射薄膜的設計與分析，首先藉由幾何光學原理探討反射薄膜的變形曲率半徑與聚焦光點之間的互動關係，規範出反射薄膜之變形範圍；再討論反射薄膜的結構設計以提高薄膜的第一自然頻率使之符合現有光碟機讀取頭的動態響應規格，運用最佳化分析獲得加強結構的最佳設計參數；其後分析含有加強結構的反射薄膜變形曲面靜態分析，討論施力位置、施力大小與反射薄膜變形曲面的曲率半徑之間相對應關係的研究。本研究已詳細分析與獲得薄膜結構最佳化設計及外力施加大小與曲率半徑變化關係，並提出曲率微調反射薄膜最佳之設計參數。

關鍵字

光碟機 ； 讀取頭 ； 曲率半徑 ； 反射薄膜 ； 磁

並列摘要

A new concept in designing the digital versatile disk-DVD pickup head is presented in the study. A deformable membrane for adaptive optics to meet the requirements of the focusing mechanism in the pickup head is designed and analyzed. It is intended to replace the conventional pickup head and can read both CD and DVD disks.
The flexible reflective membrane is made of polyimide and is coated with a reinforced ring of nickel to make its frequency high enough to avoid resonance during operation. A magnetic layer will then be coated under the membrane so that it can be deformed locally by the field of magnetic force.
The design and analysis including the dynamic characteristics of the membrane by using both the analytical and numerical solutions. The optical path is also studied to find out the initial design of the proper deflected membrane curvature. How to load the membrane so that it deforms with desired curvature is also calculated. From this through study in designing the mechanical, optical and magnetic behavior of the membrane, it provides a complete guide in realizing the prototype further in the continuing study.

並列關鍵字

DVD ； pickup head ； curvature ； flexible membrane ； magnetic

參考文獻

43 朱朝居, "DVD光學頭之光學系統介紹(上)," 光學工程, 54, pp.25-30.

44 朱朝居, "DVD光學頭之光學系統介紹(下)," 光學工程, 55, pp. 29-34.

46 施錫富, "微型光學讀寫頭簡介," 光學工程, 54, pp. 19-24.

48 胡恆敏, "光碟機避震機構分析研究," 光學工程, 54, pp. 31-35.

1 P.K.C. Wang, R.C. Gutierrez, R.K. Bartman, "A Method for Designing Electrostatic-Actuator Electrode Pattern in Micromachined Deformable Mirrors," Sensors and Actuators A, 55, pp.211-217,1996.