PROCEEDINGS ARTICLE | July 28, 2008
Proc. SPIE. 7013, Optical and Infrared Interferometry
KEYWORDS: Signal to noise ratio, Telescopes, Stars, Radio optics, Image restoration, Fourier transforms, Image resolution, Interferometry, Optical interferometry, Visibility
One of the aims of next generation optical interferometric instrumentation is to be able to make use of information
contained in the visibility phase to construct high dynamic range images.
Radio and optical interferometry are at the two extremes of phase corruption by the atmosphere. While in
radio it is possible to obtain calibrated phases for the science objects, in the optical this is currently not possible.
Instead, optical interferometry has relied on closure phase techniques to produce images. Such techniques allow
only to achieve modest dynamic ranges. However, with high contrast objects, for faint targets or when structure
detail is needed, phase referencing techniques as used in radio interferometry, should theoretically achieve higher
dynamic ranges for the same number of telescopes.
Our approach is not to provide evidence either for or against the hypothesis that phase referenced imaging
gives better dynamic range than closure phase imaging. Instead we wish to explore the potential of this technique
for future optical interferometry and also because image reconstruction in the optical using phase referencing
techniques has only been performed with limited success.
We have generated simulated, noisy, complex visibility data, analogous to the signal produced in radio interferometers,
using the VLTI as a template. We proceeded with image reconstruction using the radio image
reconstruction algorithms contained in aips imagr (clean algorithm). Our results show that image reconstruction
is successful in most of our science cases, yielding images with a 4 milliarcsecond resolution in K band.
We have also investigated the number of target candidates for optical phase referencing. Using the 2MASS
point source catalog, we show that there are several hundred objects with phase reference sources less than 30
arcseconds away, allowing to apply this technique.
