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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。
In recent years, the problem of multi-dimensional height measurement has drawn much attention. The Talbot effect of two wavelength or wavelength scanning methods has been applied to multi-dimensional step height measurement. Research shows that the Talbot-based step height measurement method has the advantages of compact structure, no mechanical scanning, high stability and large measuring range. Due to the absence of any mechanical movement of the grating or detection device, the resulting phase problems and measurement errors can be avoided. Instead of the phase information, this method uses the maximum contrast ratio of the diffraction fringes to determine the Talbot image, and all the Ronchi gratings with a duty ratio of 1 ... 2 are used as the periodic structure diffractors. In the test, different wavelength columns Erbol like distance to determine the object level. Because the stripe contrast is measured rather than the absolute intensity, the step height measurement accuracy depends on the stripe contrast and the determination and acquisition of the maximum contrast is very important. On the basis of analysis and comparison, it is pointed out that the use of non-dragon-based grating, such as sine amplitude grating or phase grating, can make the imaging fringe distribution more reasonable and effectively improve the contrast ratio of imaging fringes. The study also shows that the smaller the spatial period of the periodic structure diffractors used is, the higher the resolution is and the quantitative relationship between the resolution and the spatial period of the diffractors is given.