Impulse response function for common-path interferometers

The concept of an impulse response function (IRF) for interferometers - and especially for common-path interferometers - will be introduced as a tool for depicting fringe appearance in ESPI systems based on the shearing effect.(1) The impulse response function relates the measured phase change at an arbitrary position in the detector plane with a displacement in the object plane. Thus the IRF depicts the function of a specific filter placed in the Fourier plane of the common-path interferometer. A suite of filters will be introduced to show the specific way in which the filter will control the fringe interpretation.