Some Key Techniques Of Fizeau-type Optical Aperture Synthesis Telescope

Optical interferometry is a significant technique utilized to measure astronomicalobjects with high angle resolution. Now, Fizeau-type optical aperture synthesistelescopes(FOAST) originated from stellar interferometers with long baselinesbecome highlight gradually. Because of common mount, multiple sub-apertures andshort baselines, FOAST make it feasible for instantaneous direct imaging throughfocal plane combination. This paper is concentrated on three key techniques ofFOAST composed of four sub-apertures: array configuration, image restoration andwavefront sensing.There are two optimal array configurations proposed instead of the symmetricalcircular distribution: the asymmetrical circular distribution and the Y-type distribution.The former is analyzed according to mean square error function, and the latter lies ongeometrical parameters determined by the least image restoration error criterion.The Wiener filter method is applied to image restoration in order to improve thequality of instantaneous FOAST imaging. During the design process of this filter, anapproximate Power Spectral Density estimate of signal & noise from degraded imagesby means of local mean & variance is presented. Subsequently, a maximumexpectation algorithm is also introduced into image restructuring by several imagesfrom different directions due to baselines rotation.Concerning adaptive optics of FOAT, a software simulation and an opticalexperiment has confirmed that it is feasible to measure wavefront errors with PyramidSensor(PS). Finally, a PS wavefront restructuring algorithm based on Southwellmodel is also designed.