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相移干涉法具有非接触、快速和高精度等优点,采用实验室组建的相移干涉系统进行平面度测量时,会产生280nm左右的测量误差。通过对系统误差的分析,发现由扩束器产生的波像差是测量误差的主要来源。为了校正该测量误差,采用Zernike多项式拟合波前像差,然后在平面度测量时扣除该数值拟合结果。实验结果表明,这种误差校正方法可以使λ/4平面反射镜的测量结果从误差校正前的320nm左右减小到120nm左右。
The phase-shift interferometry has the advantages of non-contact, fast and high accuracy. When using the phase-shifting interferometry system in laboratory to measure the flatness, the measurement error of about 280nm will be produced. By analyzing the systematic error, it is found that the wave aberration generated by the beam expander is the main source of measurement error. In order to correct this measurement error, the Zernike polynomial was used to fit the wavefront aberration and then the numerical fit was subtracted from the flatness measurement. The experimental results show that the error correction method can reduce the measurement result of the λ / 4 plane mirror from about 320 nm before error correction to about 120 nm.