基于Zernike多项式的大口径离轴抛物面平行光管定焦技术

Focusing Technology Based on Zernike Polynomial for Large Aperture off-Axis Parabolic Collimator

根据Zernike多项式的第四项系数q。和Seidel像差Focus项的对应关系，选用Zernike多项式第四项的系数qt的值作为激光干涉仪法定焦的判据。利用该判据定焦，方法可行，定焦结果稳定。根据q值的正负可以判断干涉仪发出的球面波的交点处于大口径离轴抛物面平行光管的焦前或是焦后，从而指导干涉仪的前后移动。利用基于Zernike多项式的激光干涉仪法确定了大口径离轴抛物面平行光管的焦面，由标定实验可知，利用这种方法定焦效果不错，定焦后的平行光管出射光束平行性误差优于0．22。

Based on the corresponding relation of the fourth coefficient q from the Zernike polynomial and the focus item from the Seidel aberration, the value of the fourth coefficient q4 from the Zernike polynomial is used as the criterion of the focusing method for laser interferometer. The focusing method using the criterion is feasible and the result of focusing method is steady. Besides, the positive or negative of the q4 can be used to judge whether the piont of intersection of the spherical wave from the interferometer is in front of the focus plane or behind the focus plane of a large aperture off-axis parabolic collimator, which will guide the move direction. The focus plane of the large aperture off-axis parabolic collimator is confirmed by using this method. From the calibration experiment, It＇s known that the focusing effect is perfect and the parallelism error of emissive beam from collimator is less than 0.22.