一种改进的非球面同轴朗奇检测法

An Improved on-Axis Ronchi Test for Aspheric Surfaces Measurement

提出一种非球镜面形的同轴朗奇检测法,该方法使用一个半透半反镜,将点光源等效地置于非球面镜顶点的曲率中心附近,利用透射液晶显示(LCD)屏生成正弦条纹,并将其作为相移装置.在测量过程中,从点光源发出的光经过半透半反镜和待测镜面反射后,再透过半透半反镜和正弦条纹,形成的变形条纹由探测器接收.基于朗奇检测的几何原理分析采集到的条纹图,得到待测镜面偏离理想面形的偏差梯度,对其积分获得镜面偏差,从而重建待测非球面镜的面形.与传统的同轴朗奇法相比,所提方法可以避免由于光两次经过正弦条纹而引入的检测误差.此外,该方法具有较好的抗噪声能力.计算机模拟验证了所提方法的可行性.

An improved on-axis Ronchi test was proposed to measure aspheric mirror surfaces.In the proposed method,apoint source was located near the center of curvature of the test mirror by using a beam splitter.A transmission-type liquid crystal display(LCD)screen was employed to display sinusoidal fringes and work as the phase-shifting device.In the measurement process,the light from a point source was reflected by the beam splitter and the test mirror,and then it traveled through the beam splitter and the sinusoidal fringes.Deformed fringes were captured by a detector.By analyzing recorded fringes based on the geometric principle of the Ronchi test,the slopes of the deviations of the mirror were obtained.By integrating these slope,the deviations of the test mirror was restored,and then the shape of test mirror was reconstructed.Compared with the traditional on-aixs Ronchi test,the proposed method can avoid measurement error which is caused when light goes through sinusoidal fringes twice.Computer simulation was carried out to demonstrate the validity of the presented method.