On the basis of communication theory, the method of backward impulse responseis proposed to explain the phenomena of interference with an extended white light source. In this treatment, the mathematics is Simple while the physical meaning becomes clearer. In addition it is possible to reach a unified point of view. The following two examples will be demonstrated: 1) imaging interferometers, and 2) Lau effect and grating imaging. In the present paper, only the former is discussed. In this paper a generalized model for the imaging interferometer is proposed in terms of the backward impulse response. The necessary condition for constructing the exact system is that the backward impulse response to the image point at the sonroe plane through both the active beamsplitter and the compensator must have a form of single wavefront. A generalized expression for the intensity distribution of the resultant interferogram is derived with the conclusion that the complex amplitude of the image point is proportional to the integral of the square of the backward impulse response at the object plane and the object phase variation. This response directly determines different kind of interference. Three configurations with amplitude division,, polarization division and diffraction division are analysed in detail. The effect of color fringes caused by the dispersion in polychromatic illumination is also discussed.