基于波长扫描塔尔博特效应的阶高测量理论研究  

Theoretical Study of Arbitrary Step-Height Measurement Based on Wavelength-Scanning Talbot Effect

作　　者：张成义[1] 李传起[1] 裴世鑫[1] 

机构地区：[1]南京信息工程大学物理系,江苏南京210044

出　　处：《光学学报》2008年第12期2307-2310,共4页Acta Optica Sinica

基　　金：江苏省自然科学基金(BK2008437);江苏省高校自然科学基金(08KJB140002)资助课题

摘　　要：近年来,多维阶高测量问题倍受关注,两波长或波长扫描方式的塔尔博特效应被应用于多维阶高测量。研究表明,基于塔尔博特(Talbot)效应的阶高测量方法具有仪器结构紧凑、无需机械扫描、稳定性高和测量范围大等优点。因没有光栅或检测器件的任何机械移动,可避免由此导致的相位问题及测量误差。取代相位信息,该方法采用衍射条纹的最大衬比度来判定塔尔博特像,测试中均采用占空比为1…2的龙基(Ronchi)光栅作为周期结构衍射物,利用不同波长塔尔博特像的像距来确定物体阶高。因为测量的是条纹衬比度而非绝对强度,所以阶高测量精度依赖于条纹衬比度,最大衬比度的获取与判定是非常重要的。在分析对比的基础上指出,采用非龙基型光栅,如正弦振幅光栅或相位光栅,能使成像条纹分布更合理,有效地提高成像条纹的衬比度。研究还表明,所采用周期结构衍射物的空间周期越小,分辨率就越高,从而给出了分辨率同衍射物空间周期的定量关系。Recently, arbitrary multi-dimensional step-height measurement has attracted much attention. Two wavelength Talbot effect or wavelength-scanning Talbot effect is implemented for the arbitrary step-height measurement. The main advantages of the method are non-mechanical scanning, high stability because of its common-path geometry and compactness. Without any mechanical movement of the grating or the detector in the longitudinal direction, the system is free from phase ambiguity problem and measurement errors caused by it. Instead of phase information, the maximum contrast of the high visibility bands is used to judge the occurrence of Talbot image, Ronchi grating with an open ratio of 0.5 is used for the periodic structure diffraction object, step-height measurement is given by the distance of self-image planes. Since the technique measures the fringe contrast rather than absolute intensity, accuracy of the step-height measurement depends on the fringe contrast. It is important that acquirement and judgement of the maximum contrast of the high visibility bands. It is pointed out that the smaller the pitch of the grating is, the better the lateral spatial resolution of the system will be. Further, non-Ronchi grating such as sinusoidal grating or phase grating can be used to improve the maximum contrast of the high visibility bands.

关 键 词：测量 阶高 波长扫描 塔尔博特效应 分辨率 

分 类 号：TN911.74[电子电信—通信与信息系统] O438.2[电子电信—信息与通信工程]