Quantitative and analytical analysis of modulation process of the collimator
is a great challenge, and is also of great value to the design and development
of Fourier transform imaging telescopes. The Hard X-ray Imager (HXI), as one of
the three payloads onboard the Advanced Space-based Solar Observatory(ASO-S)
mission, adopts modulating Fourier-Transformation imaging technique and will be
used to explore mechanism of energy release and transmission in solar flare
activities. In this paper, a mathematical model is developed to analyze the
modulation function under a simplified condition first. Then its behavior under
six degrees of freedom is calculated after adding the rotation matrix and
translation change to the model. In addition, unparalleled light and extended
sources also are considered so that our model can be used to analyze the X-ray
beam experiment. Next, applied to the practical HXI conditions, the model has
been confirmed not only by Geant4 simulations but also by some verification
experiments. Furthermore, how this model will help to improve the image
reconstruction process after the launch of ASO-S is also presented