Development of an aspherical shape measurement system for on-machine

针对超精密板条加工后的非球面，研制了一套机内测量系统：1)剪切干涉仪：研制了一种剪切干涉仪，用于超精密板条加工后的非球面的测量。由于工具柱覆盖了干涉图的一部分，对线阵CCD相机采集的干涉图的强度进行了分析。利用带片产生非球面波前。2)软件：开发了分析干涉图的软件。每次将被测表面旋转固定角度即可得到干涉图。因此，对每个干涉图进行分析，得到经过车削中心的线形，并将线形组合构成非球面。并提出了一种将曲线拟合到测量形状的算法。3)实验与结果：测量了一个中心点有形状误差的球面反射镜，以评估开发系统的能力。该系统的测量结果与菲索干涉仪的测量结果吻合较好。4)新原理的提出：提出了一种利用多曲率球面波前测量非球面的方法。仿真和实验验证了该方法的有效性。

To measure an aspherical surface processed by an ultra precision lath, an on-machine measurement system was developed as follows:1)Shearing interferometer : A shearing interferometer was developed to measure the asperical surface on the ultra precision lath just after the processing. Because a part of an interferogram was covered with a tool post, the intensity of the interferogram acquired by a line CCD camera was analyzed. And a zone plate was used to generate the aspherical wave front.2)Software : Software was developed to analyze the interferograms. The interferograms were obtained every time that the measured surface was turned fixed angle. Therefore, each interferogram was analyzed to obtained a line shape passing through the turning center and the line shapes were assembled to construct aspherical surface. And an algorism was developed to fit a curve into measured shape.3)Experiment and results : A spherical mirror with shape error in center point was measured to estimate an ability of developed system. The result obtained by developed system agree well with the result obtained by Fizeau interferometer.4)Proposal of new principle : A method of measurement using many sphere wave fronts with various curvatures was proposed to measure these aspherical surfaces. Validity of proposed method was confirmed by simulations and experiments.