Beam Combination for Wide Field Imaging

Abstract

ABSTRACT. Several limitations reduce the field of view in radiointerferometry. With an optical array, two of them can be overcome to some extent according to the beam combination method. A beam combination in the pupil plane can completely overcome one of them. In the image plane, a beam combination obeying the rules of geometrical optics can overcome both limitations in principle, but is difficult to achieve in practice. We discuss particularly the real case of a Michelson Stellar Interferometer where a periscope partially re-introduces these limitations, yielding a trade-off between the extension of the field of view and the use of the periscope.

Optical Interferometry

“…In contrast, in a Michelson interferometer there is no homothetic relation between the input and output pupils. 2 This means the object-image relationship can no longer be described as a convolution, because the rearrangement of the apertures rearranges the high-spatial frequency part of the object spectrum in the Fourier plane (Tallon & Tallon-Bosc 1992). This has an important consequence for off-axis objects: The image position does not coincide with the white-light fringe position (see Figure 1 in Tallon & Tallon-Bosc 1992).…”

“…2 This means the object-image relationship can no longer be described as a convolution, because the rearrangement of the apertures rearranges the high-spatial frequency part of the object spectrum in the Fourier plane (Tallon & Tallon-Bosc 1992). This has an important consequence for off-axis objects: The image position does not coincide with the white-light fringe position (see Figure 1 in Tallon & Tallon-Bosc 1992). For a finite spectral bandwidth this means the fringe contrast decreases with field angle and the field of view is limited; the maximum size of an image from a Michelson interferometer is ∼R ≡ λ/ λ resolution elements in diameter.…”