Realization of a kind of interferometric imaging telescope with four apertures

The Fizeau type interferometric telescope forms an array of several sub telescopes for direct imaging on the image plane based on the principle of optical interferometry. Compared to the optical long baseline interferometer, this kind of telescope can be used for real time imaging of celestial body due to some excellent characteristics such as sufficient spatial frequencies coverage, single mounting avoiding outer optical delay lines and so on. We have built an interferometric imaging telescope with four apertures. Although each aperture size is 100mm, but this telescope can reach the higher angular resolution which is equivalent to a monolithic telescope of 280mm aperture size through optimal array configuration. Some novel opto-mechanical structure design and error control methods have been applied to this telescope successfully. For example, in order to enhance the rigidity of mechanical system, a unique C-shape structure to replace the traditional azimuth axis is adapted. Piston, tip/tilt errors between all apertures can be detected at the same time by extracting signals from Modulation Transfer Function (MTF), so some classical beam splitters can be removed which will reduce light loss significantly. At present, we have finished the final assembly, co-phasing calibration and verifying of dynamic co-phasing close-loop methods at laboratory. The FWHM of far field image spot is 0.43 arcsecond which is consistent with theoretical values. The out-door astronomical observation will be carried out soon.