Novel spectral imaging method for Fizeau interferometer

There are two different types of beam combination: Fizeau interferometer and Michelson interferometer. Pupil plane beam combination is referred as Fizeau interferometer. On the other hand, image plane beam combination is referred as Michelson interferometer. In general, working principles of Michelson interferometers are based on double Fourier interferometry. It is possible to acquire two-dimensional spatial and one-dimensional spectral information of the sky by applying a Fourier transform spectrometer algorithm and the Van Cittert-Zernike theorem. This imaging scheme is referred to as the double Fourier interferometry. On the other hand, it is so far thought to be difficult to perform the imaging with a Fizeau interferometer, because Fizeau interferometers basically don't have a delay line that is equipped with Michelson interferometers. Here, Matsuo et al.¹ presented a new spectral imaging method for Fizeau interferometers, based on double Fourier interferometry. They noticed that a delay axis in Michelson interferometers is equal to the axis of a fringe pattern on an image plane in Fizeau interferometers. Therefore, this new approach can acquire three-dimensional information of the sky using a linear array detector placed on the image plane. In this paper, we compare the new spectral imaging method for Fizeau interferometer with the conventional one used for Michelson interferometer and discuss spectral resolutions and field of views of these imaging methods.