适合于微细加工的外差探测技术及应用(英文)

Heterodyne testing technique and its applications in micro-machining

本文详细地讨论了外差干涉仪的两个主要问题 ,即干涉仪的横向定位问题和非线性误差分析及其误差补偿问题。首先 ,提出了一种新颖的解析方法实现干涉仪亚微米级的高精度定位。该方法首先建立了测量光束扫过台阶边缘时测量相位渐变数学模型 ,并讨论了它与激光束分布的关系。文章利用以上数学模型对测量相位数据进行了详细地分析 ,实现了在一般激光束径时 ,干涉仪的定位精度为亚微米量级。另一方面 ,文章详细地分析了共光路干涉仪三个主要误差源。分析结果表明 :由Wollaston棱镜引起的误差主要是二阶误差 ,而由激光束的椭圆偏振化引起的误差为一阶误差。同时我们发现 :金属反射镜的方位误差可以使线偏振光经反射后变为椭圆偏振光 ,该椭圆偏振光具有不正交性和不相等偏心度 ,文章首次详细地分析了这种不正交性和不相等偏心度与反射镜方位误差的关系及其由此产生的非线性误差。最后 ,文章分析了干涉仪的误差补偿措施以提高整个干涉仪的测量精度。

Two main problems of heterodyne interferometer, lateral resolution of interferometer, and the nonli near errors and its compensation, are discussed by first introducing a new analy tical method to ac hieve positioning accuracy of sub-micron and then establishing a mathematical mo del o f the relationship between the measurement phase and the amplitude distribution of laser beam to explain the gradual change of the measu rement phase around the sharp step. The amplitude distribution of laser beam at the step can be got and the lateral positioning accuracy can be achieved to the magn itude of submicron by using the estimation method used for ordinary laser beam. The results of analysis of the three major nonlinear error sources of the common -path interferom eter show that the error caused by Wollaston prism is mainly second harmonic and the error caused by elliptical polarization of laser is firs t harmo nic. Further analysis indicates that the misorientation of metal mirror can ca use the two r eflecting beams to change from linear polarized beams into elliptical polarized bea ms with nonorthoganal and nonequal eccentricity, which can generate mainly the f i rst harmonic nonlinear error. In additions, error compensation methods are also proposed to improve the accuracy of the interferometer.