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光干涉计量是一种以光的波长为计量单位的高精度计量方法。干涉检验所得到的直接结果通常是一幅或几幅干涉图形。被检光学面的形貌误差或被检光学系统的波像差等等都是以波长为间隔的等高线的形式反映在干涉图中。所以如何由干涉图准确判读被检波前的形状,获取被检波前形貌尽可能完整的信息,即干涉图的判读问题,是干涉计量中的一个十分重要的问题。本系统是以计算机技术和光电技术相结合的干涉计量方法,该方法首先将干涉仪所形成的干涉条纹通过图形数字化仪器转化成图形数据并以 Windows 标准位图格式存入计算机,获得原始图像数据,用自行设计的软件对该图像数据进行预处理,产生供给后续数据拟合中适用的初始数据,该初始数据是通过对干涉图条纹进行规律采样得到的,代表着干涉图形所包含的波前信息。在图形数据拟合时,主要应用了泽尼克(Zernike)多项式拟合的方法,其数学模型比较复杂,但其基本原理与傅里叶级数理论中把任意一个连续光滑曲线看成是由一系列不同频率、不同振幅的正弦和余弦曲线相叠加而成的概念相似,意同样也可以把任意一个被检波前看成是一系列不同形状、归一化的基本波面按一定权重系数叠加而成,基中每一种基元波面已知,而且具有相对简单的解析表达式。实验表明本系统能够较准确地给出被检波前的解析式,实现了干涉图的计算机判读。
Light interferometry is a high-precision measurement method that uses the wavelength of light as a unit of measure. The direct result of interference testing is usually one or more interference patterns. The topography of the examined optical surface or the optical aberrations of the optical system to be inspected are all reflected in the interferogram in the form of contour lines at the wavelength intervals. Therefore, it is a very important issue in interferometry that how to accurately interpret the shape of the detected wavefront by interferogram and get the information as complete as possible before the detected wavefront, that is, the interpretation of the interferogram. The system is a combination of computer technology and optoelectronic technology, interferometry method, the method of interference fringes formed by the interferometer first figure digitized instrument into graphical data and Windows standard bitmap format stored in the computer to obtain the original image data , Pre-processing the image data by using self-designed software to generate initial data that is suitable for subsequent data fitting. The initial data is obtained by regularly sampling the interference pattern fringes, and represents the wavefront included in the interference pattern information. In the fitting of graph data, Zernike polynomial fitting method is mainly applied. Its mathematical model is complicated, but the basic principle and the Fourier series theory consider any continuous smooth curve as a Series of different frequencies, different amplitudes of the sine and cosine curves formed by the concept of superimposed, meaning the same can also be detected as a wave front is a series of different shapes, the normalization of the basic wave surface by a certain weight coefficient overlay , The basis of each base wave surface is known, but also has a relatively simple analytical expression. Experiments show that the system can be more accurately given the pre-detected analytic formula to achieve the computer interpretation of the interferogram.