Mechanical setup for optical aperture synthesis for wide-field imaging

Abstract

Homothetic mapping is a technique that combines the images from several telescopes so that it looks like as though they came form a single large telescope. This technique enables a much wider interferometric field of image than current techniques can provide. To investigate the feasibility, a research testbed is build know as Delft Testbed interferometer (DTI). DTI simulates a configuration of three telescopes collecting light of a set of 3 stars. The stars are simulated by coupling light of a Xenon light source into three fibres, which illuminate a parabolic mirror. The light that is used has wavelengths of 500 nm - 800 nm. The light of the three telescopes will be combined in such a way that the beam arrangement in the pupil plane corresponds with the telescope arrangement and the Optical Path Difference (OPD) is minimized for the three beams. To achieve white light fringes with high visibility, the mechanical testbed that is 2 m x 1 m x 0.5 m in size, requires stable mounting of components. This paper describes the mounting of the diamond turned off-axis parabolic mirrors of 200 mm in diameter and 240 mm flat mirrors; furthermore, it describes components like the telescopes and the active controllable components for repositioning of the beam arrangement. Mechanisms were developed for alignment of piezo actuators and for delay lines. The delay lines can also be used to compensate pupil rotation. Test results demonstrate that the test setup is highly stable for temperature as well as for airflow, although the system is placed in a non-thermally controlled lab. This allows measurements of nm, in presence of μm disturbances.