新型透鏡式光學位移感測器設計與實作

Design and Implementation of a Novel Optical Displacement Encoder

陳群育(Chun-Yu Chen)

指導教授 ： 范憶華

中原大學/工學院/機械工程研究所/碩士(2010年)

https://doi.org/10.6840/cycu201200150

摘要

隨著微/奈米技術的蓬勃發展，許多微/奈米加工或量測系統的開發都有賴於奈米等級之位移量測或定位技術；然而現今具奈米等級解析度之感測器大多易受環境之干擾，且價格昂貴，於是如何開發同時具有微小化、高解析、低成本、易使用等優點之感測器，即是量測科技中一個重要的課題。
本文提出一種最高解析度為1nm，總行程可達5mm之新型光學位移感測器，本位移感測器是由雷射光源系統、光學透鏡系統以及光偵測器系統等三個部分所組成。本文有別於一般的雷射光學尺，藉由幾何光學之探討，設計一具有良好放大效能之光學透鏡，利用透鏡將光源放大的方式使雷射位移感測器的解析度達到1nm。本研究利用厚透鏡方程式推導出透鏡之曲率半徑與其放大倍率的關係，然而在實際的光學系統中，只有在近軸區域以很小孔徑角的光束所生成的像才是完善的，其餘經由透鏡折射後的像皆會產生像差，且愈遠離光軸像差愈大，因此本文透過設計透鏡之光線出射面的曲率半徑，藉此補償光線經透鏡放大後的差異。本研究使用直徑為0.2mm之雷射光源，直徑為12mm、厚度為2mm之雙凹透鏡，以光學設計軟體分析並模擬其光學特性，由模擬結果得知，當透鏡之光線入射面的曲率半徑為-6.25mm，光線出射面的曲率半徑為12.5mm，且光源移動範圍在距離透鏡光軸±2.5mm之內時，能以380mm的成像距離達到50倍之放大倍率以及 1.5nm的量測精度。

關鍵字

透鏡 ； 光學感測器

並列摘要

A novel optical displacement encoder with 1 nm resolution was proposed in this paper. The optical displacement encoder was composed of a laser light source, an optical mechanism, and a photo-detector. At present, the general laser optical displacement encoders were based on the moire or grating projection to measure the displacement of moving parts. The idea of this paper was different from the traditional laser optical displacement encoders. We designed an optical mechanism by geometrical optics to change the paths of light, and then to get a more visible position change in the optical detector to improve the measurement accuracy. Firstly, we used the equations of thick lens to develop the relationship between the rays of light and the radii of curvature of the lens. Because the light will be refracted twice after entering the lens, the same primitive displacement of the light in the different input positions will not have the same output displacement and the differences will be enlarging as the position of the light entering the lens is far away from the center of lens. Thus, we designed the radius of curvature of the exit surface on the lens to modify the paths of light to compensating the deviations on the detecting surface and getting higher measuring accuracy. The diameter and thickness of the double-concave lens are 12 mm of 2 mm was used to form the optical system. From the simulations by the optical design software of Light Tools showed that an optical mechanism with 5 mm stroke, which the lens radii of curvature of the incident and the exit surface on the lens were -0.625 cm and 1.25 cm, respectively, and the magnification was 50 times in imaging distance of 38 cm, could make the 1 nm movement intervals of light source to be about 50 nm movement intervals in the detecting surface. Thus we can combine the optical mechanism and a photo-detector array with 50 nm resolution and 25 cm total detecting length to form the optical displacement encoder with 1 nm measuring accuracy.

並列關鍵字

lens ； optical encoder

參考文獻

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