A Dynamic Zone Plate Interferometer for measuring Aspherical Surfaces

光学表面粗糙度仪对于测量被测光学表面的形状与标准表面的形状之间的差异非常有用。但是，传统的方法需要相当大的修改，如果要扩展的应用：由于可测量的最大差异的表面是不是很大，它是相当困难的，直接获得非球面表面的误差。为此，需要使用计算全息（CGH）等特殊装置来获得变形或非球面的标准波前，而本课题所研究的动态波带片干涉仪（DZPI）可以在不需要计算全息或标准面的情况下测量变形或非球面的标准波前。在DZPI中，光源的波长被改变，以产生一系列具有不同半径的参考球体，由于每个干涉图显示了被测光学元件表面与许多参考球体之一之间的光程差，因此形状和表面都可以被测量。 ...更多信息 实验测量了两个F数为3和4的抛物面镜，用环形染料激光器作光源。在每一个波长处，记录干涉图并将其发送到计算机进行处理。由于波长变化的不连续性，很难使用传统的技术进行条纹分析。在此基础上，提出并应用了连续空间中的傅里叶分析方法，理论分析表明，在一定的参数范围内，傅里叶分析方法与最小二乘法是等价的，并从理论上分析了在观测系统存在加性噪声和非线性响应的情况下，该方法的定相误差。它表明，测量误差可以最小化与选择适当的系统参数。实验结果证明了DZPI测量非球面的可行性。少

Optical interierometers are quite useful for measuring the difference between the shape of an optical surface under test and that of a standard surface. But, conventional methods need considerable modification if the applications are to be extended : since the measurable maximum difference between surfaces is not large, it is quite difficult to obtain directly the error of aspherical surfaces. For this purpose, some special devices such as computer generated holograms or CGH are indispensable for obtaining the deformed or aspherical standard wavefronts.A dynamic zone plate interferometer (DZPI) being studied in this project can measure such surfaces without any need of either CGH or standard surface. The wavelength of the light source is changed in DZPI to generate a series of reference spheres with different radii, Since each interferogram shows the optical path difference between the surface of the optical element under test and one of the many reference shperes, both shape and surfa … More ce error can be calculated from a series of interierograms taken at different wavelengths.Two parabolic mirrors, whose F-numbers are 3 and 4, are experimentally measured As a light source, a ring dye laser is utilized. At each wavelength, an interferogram is recorded and sent to a computer to be processed. Because of the discontinuity of the wavelength change, it is difficult to use a conventional technique for fringe analysis. Then, a Fourier analysis in a continuous space is developed and applied, A theoretical analysis concludes that Fourier method become equivalent to the least square method for a certain set of the parameters used in the analysis.The phase determination error of the proposed method is also theoretically analzed in case of additive noise and nonlinear response through the observation system. It is shown that the measurement error can be minimized with a selection of appropriate system parameters. Experimental results ensure the feasibillity of the DZPI for measuring aspherical surfaces. Less