Optical long-baseline interferometry: signal-to-noise ratio of Image reconstruction by optical phase-closure imaging and by speckle masking

Optical multiple-mirror interferometers in space can yield fascinating angular resolution. For example, at lambda ~100 nm and with an interferometer diameter of 20 m, a resolution of 0.001 sec of arc can be obtained. From the speckle interferograms recorded with ground-based interferometers or space interferometers, diffraction-limited images can be reconstructed by various methods. In this paper the signal-to-noise ratio of the two image reconstruction methods, optical phase-closure imaging and speckle masking (triple correlation), will be investigated. The results show that (1) phase-closure imaging yields images with higher signal to noise ratio than speckle masking for bright objects and (2) speckle masking yields images with higher signal-to-noise ratio than phase-closure imaging for faint objects.