新型波長調制外差光源應用於位移量測

A novel wavelength-modulated heterodyne light source for displacement measurement

鍾於哲(Yu-che Chung)

指導教授 ： 李朱育

國立中央大學/工學院/機械工程學系/碩士(2013年)

摘要

本論文提出一套新型的波長調制外差光源，並將此新型外差光源應用於一維
和二維準共光程光柵干涉儀之位移量測上。利用雷射二極體搭配雙折射晶體來產
生新型的外差光源，雷射二極體波長受到鋸齒波調制，並利用雙折射晶體具雙折
射率的特性，使得入射光的p 偏振光與s 偏振光產生一光程差，進而得到外差光
源。此新型外差光源的產生方式，可達到縮小體積與降低成本的功效。
首先利用四分之一波片來驗證此新型外差光源應用於相位解析的可行性，接
著應用於一維和二維準共光程光柵干涉儀之位移量測上，利用壓電平台來使光柵
位移，並利用鎖相放大器擷取因光柵位移而產生的相位變化，反推光柵位移量。
實驗證明本系統於一維準共光程光柵干涉儀之架構上量測解析度約為10
nm，於二維準共光程光柵干涉儀之Z 方向與Y 方向的量測解析度分別為10 nm
與20 nm，系統靈敏度為0.18°/nm。
關

關鍵字

外差光源 ； 位移量測 ； 外差干涉術 ； 繞射光柵

並列摘要

A novel “ Wavelength-modulated heterodyne light source ” was proposed. The novel heterodyne light source was applied to the displacement measurement based on one-dimensional or two-dimensional quasi-common optical
path grating interferometry. The novel heterodyne light source used here consists of a birefringent crystal and a laser diode. The wavelength of the laser diode is modulated
by a sawtooth current signal. As a consequence of the double refraction caused by the birefringent crystal, the modulated light signal is refracted by the birefringent crystal
with two different light paths, therefore , a novel “Wavelength-modulated heterodyne light source” was proposed. The heterodyne light source can be made to a relatively small size and save much cost compared with known heterodyne light sources at present.
We first use of a quarter wave plate to validate the feasibility of the phase demodulation, then the novel heterodyne light source was applied to displacement
measurement based on one-dimensional or two-dimensional quasi-common optical path grating interferometry. We let the grating is moved by the piezoelectric, the optical phase variation which results from the grating moving will be measured by the lock-in amplifier, therefore, we can get the grating movement.
From experiment results, the resolution of the one-dimensional quasi-common optical path grating interferometry is 10 nm. The resolution in z-direction and y-direction of the two-dimensional quasi-common optical path grating
interferometry are about 10 nm and 20 nm. The sensitivity is 0.18°/nm.

並列關鍵字

heterodyne light source ； displacement measurement ； heterodyne interferometry ； diffraction grating

參考文獻

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