兩百萬畫素之高變倍率液態鏡頭光學變焦系統設計

High Zoom Ratio Optical Zoom System with Liquid Lens for Two Mega-Pixel Image Sensor

楊千立(Cian-Li Yang)

指導教授 ： 陳政寰

國立清華大學/工學院/動力機械工程學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00531

摘要

本研究主要針對使用液態透鏡之變焦系統進行研究。液態透鏡具有變動本身會聚光線能力的功能，因此可以在不需要移動元件的情況下，達成變焦的功能。液態透鏡提供了變焦系統設計上的嶄新思維，也具有使變焦系統輕薄短小的可能性。本研究提出了三種將液態透鏡應用於變焦系統的設計方式，各別具有不同的設計架構與系統特性，隨著每階段的演進，在變焦倍率上都有長足的進展。
第一種為二群液態透鏡組合變焦系統，將傳統變焦系統中可移動的變焦群及補償群都使用液態透鏡取代之，因此可在不需要任何移動元件的情況下，達成1.5倍的變焦倍率。但為了達成變焦功能，所需的液態表面曲率變化量過大，引發過大的像差，因此成像品質不佳。
第二種為液態補償式單移動群變焦系統，一個移動群負責改變系統焦距，液態透鏡則做為補償群之用。應用最小改變量原則可減輕液態透鏡在變焦時所負擔的補償量，可將變焦倍率提昇至2.5倍。但其變焦倍率之極限仍然被液態透鏡之表面曲率變化量所侷限，因此無法將變焦倍率突破至3倍以上。
第三種為光學補償式液態輔助變焦系統，結合傳統的光學補償透鏡，增加變焦過程中的後焦距交叉點，可在高變焦倍率的條件底下，減輕液態透鏡負擔的補償量。因此可以將變焦倍率大幅提昇至4倍。
本研究提出全視場角60度、變焦倍率最高4倍、整體厚度在30 mm以內且能適用於兩百萬畫素影像感測器之高變倍率液態透鏡變焦系統。其4倍之變倍率並不遜於市售之數位相機，僅使用1群移動群，與傳統4至5群的變焦系統相比，大幅減少機構製作的難度。而在厚度上仍然具有小型照相系統之特徵，提供了將變焦系統應用在照相手機與PC Camera上的可能性。

關鍵字

液態透鏡 ； 變焦系統

並列摘要

The objective of this research is to investigate the feasibility of a zoom system using liquid lens as the active element. Different from the conventional zoom lens which uses moving lens element to perform zoom function, the liquid lens changes system power without movement, which potentially provide a compact solution for zoom system. This research proposes three different types of liquid zoom system which have totally different design concept and system feature, and has its own limit on zoom ratio.
The first type is double liquid lens zoom system whose variator and compensator are replaced with liquid lens in traditional movable zoom system. The 1.5× zoom ratio had been achieved by double liquid lens zoom system without any movable component. But the large variation of the liquid surface curvature causes serious aberration and deteriorates image quality.
The second one is liquid-compensated movable zoom system. A movable lens performs the zoom function, and a liquid lens is used for correcting the image plane. The principle of smallest change has been applied for reducing the variation of the liquid surface curvature during the zooming process. The 2.5× zoom ratio had been achieved but has still been limited by the variation of the liquid surface curvature, and could not be exceed to 3×.
The third one is the combination of liquid lens and the concept of optically compensated zoom system. The zoom ratio could be improved to 4× because the zero-crossing of back focal shift during the zoom process, and the liquid lens is disposed to slightly correct the image plane in accordance.
This outcome of the research is a liquid zoom system for two mega-pixel image sensor with 60 degree full viewing angle, 4× zoom ratio and a total track less than 30 mm. The high zoom ratio of 4× is equivalent to digital camera but only one moving group compared with the four or five moving groups of the traditional zoom system. In conclusion, the liquid zoom system provides a compact solution for portable devices such as mobile phone camera and PC camera.

並列關鍵字

liquid lens ； zoom system

參考文獻

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