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为了补偿激光外差干涉纳米测量中的非线性误差,提出了一种减小非线性误差的一次谐波方法。基于全反射理论分析了镀膜实体角锥棱镜反射光偏振特性,并由此推导出角锥棱镜反射光偏振特性及测量角锥棱镜以其运动方向为轴线的轴向旋转对激光外差干涉非线性误差一次谐波的影响模型。理论分析表明,测量角锥棱镜以其运动方向为轴线的轴向旋转会减小非线性误差一次谐波,当测量角锥棱镜轴向旋转97°时,可使非线性误差一次谐波达到最小,约为原有非线性误差一次谐波分量的1/20倍。当激光器出射的两束线偏振光存在6°非正交误差时,镀膜实体测量角锥棱镜轴向旋转角度从0°增加到97°,非线性误差一次谐波由5.30 nm减小到0.30 nm。
In order to compensate for the nonlinear error in the laser heterodyne interference nanometer measurement, a first harmonic method to reduce the nonlinear error is proposed. Based on the theory of total reflection, the polarization characteristics of the reflected light of the coated solid cube corner prism are analyzed, and the polarization characteristics of the reflected light from the cube corner prism and the axial rotation of the corner cube with respect to the movement direction of the cube corner prism are analyzed. Influence Model of Error First Harmonic. The theoretical analysis shows that measuring the axial rotation of the corner cube with its axis of motion will reduce the first-order nonlinearity of the nonlinear error. When the measuring cube-corner prism rotates 97 ° in axial direction, the first order nonlinear harmonic error can be minimized , About 1/20 times of the first harmonic component of the original nonlinear error. When there is a 6 ° non-orthogonal error between the two linearly polarized beams emitted by the laser, the axial rotation angle of the pyramid prism measured by the coated entity is increased from 0 ° to 97 °, and the first harmonic of the nonlinear error is reduced from 5.30 nm to 0.30 nm .