Optical Very Large Array (OVLA)
The Optical Very Large Array (OVLA) is a project that was the first proposal for a giant multi-telescope interferometer with high resolution direct imaging capabilities. It was proposed by Labeyrie in 1987. The original version of the OVLA called for 27 mobile 1.5-meter telescopes arrayed along an ellipse, which is the intersection between the ground plane and a virtual giant parabola pointing towards the star. As the star follows its diurnal path in the sky, the virtual parabola has to track it, so the telescopes are moving continuously on the ground to follow the ellipse distortion. Thus, no delay-line is required.
More recently, another concept was proposed for a giant direct imaging interferometer. Called Carlina Hypertelescope, it is simplified as it does not require mobile telescopes nor delay lines. Its design is analogous to the Arecibo radio telescope, with a diluted aperture, although working in the visible and near infrared, but has a diluted aperture which is rearranged in the beam combiner to provide a densified pupil (Labeyrie 1996, Borkowski et al.2005).
[This text is taken from the introduction to a paper called "The Optical Very Large Array project (OVLA): a concept for kilometric ground-based hypertelescopes by O. Lardi'ere1, J. Dejonghe1, L. Arnold, and A. Labeyrie.]