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.