The optimal design method for the extended source of interferometer

The optimal design for an extended source interferometer is discussed in this paper. Compared with the classical point source interferometer, interferometer with an extended source can decrease the coherent noise, dust/defects scattering effects and high-frequency error of reference surface significantly. The adjustable extended source model is introduced. The size, shape, and intensity distribution of the source are optimized by using the interferometer simulation platform which is established by Zemax optical design software and Matlab data analysis software in this paper. After determined parameters of the basic structure of the interferometer, an interferometer model was set up by using muti-configuration in the sequential mode of Zemax. The communication technique of DDE (Dynamic Data Exchange) between Zemax and Matlab was applied to the numeric simulation process. Under the control of Matlab, the field parameters of the optical system can be rectified, and it was easy to get a series of interferogram data. So it was convenient to calculate the visibility of interference fringes. The relation curves between the spatial coherence and the size, shape, intensity distribution of the extended source can be plotted by Matlab. In order to meet the operating requirements of different coherence lengths, Zemax was used to optimize the concrete forms of light sources. Simulation results show that short coherence length can be realized by the Sinc² - shaped extended source, while source of Cos - shape or Comb - shape can realize long coherence length.