绝对检验参考镜误差分析与热变形模型建立

Study of the Error of the Reference Lens in Absolute Spherical Testing and the Thermal Deformation Model Establishment

绝对检验是提高菲佐(Fizeau)型干涉仪参考面面形精度的重要方法。研究了过程中温度、重力和夹持力对绝对检验精度的影响。采用Gram-Schmidt拟合方法对参考面面形的变形量进行了拟合,分析了K9、融石英和微晶材料的参考镜均匀温度变化下的热变形及由于热变形导致的相应泽尼克(Zernike)系数的变化。最后,分析了变形量对应的面形误差,建立了每种材料的热变形模型。结果表明,经过重力、夹持力和温度三者的叠加耦合,温度变化产生的变形量与温度变化量仍呈近似的线性关系。在相同的外界条件下,融石英材料产生的整体变形量最小;而微晶材料产生的热变形量最小。微晶参考面由于热变形产生的面形变化量均方根为0.37 nm/℃。

Absolute measurement is an important method achieve the high accuracy of the reference wave front in factors including temperature, gravity and clamping force to improve the accuracy of the Fizeau interferometer. To absolute spherical testing, the influence of environmental was studied. The Gram-Schmidt fitting was used to fit the deformation of the reference surface in representation of the Zernike coefficients. The contribution of the thermal deformation by temperature change and the change in Zernike coefficients caused just by temperature change were compared. The model of the thermal deformation was created and the corresponding aberration mode of the reference surface was analyzed which make the separation of the deformation caused by temperature possible so that the test accuracy can be enhanced. The result indicates that the deformation of fused silica is smaller than that of K9 and zerodur on the whole while the deformation of zerodur is smaller than that of K9 and fused silica in just temperature change. When the temperature takes one degree change, the root mean square of the zerodur surface reaches 0.37 nm.