Research On Optical Interferometric Array Configuration

Observation of the universe demands high resolution of the telescope.The traditional way to increase resolution of the telescope is increasing the aperture diameter of the telescope.However,the processing difficulty of the large aperture is great,and the cost is proportional to the square of aperture diameter,which will rise fast with the aperture diameter increasing.Moreover,too large aperture makes the mechanical support structure hard to be satisfactory,and makes the transportation difficult.Therefore,scientists desire to find a way to improve imaging resolution without increasing the aperture diameter.One way to achieve this is to adopt interferometric imaging technology,and the optical interferometric array is built with this technology for high resolution observation.Theoretically,the longest baseline of the interferometric array determines its limiting resolution.However,the sampling of spatial frequency by the interferometric array is discrete.If there are not enough apertures,the incomplete sampling of spatial frequency will cause the degradation of the reconstructed image,so that the theoretical resolution cannot be reached.Since the array configuration will affect the image quality,it is meaningful to design the array configuration for good image quality.This dissertation focuses on following up the predecessors' research on the interferometric array configuration,and discussing the relationship between the array configuration,UV-plane coverage and the image quality to provide more sufficient theoretical basis for real optical interferometric array configuration design.First,the background,significance,principle and key technology of interferometric imaging are introduced.The existing interferometric arrays are concluded.The issue of interferometric array configuration and the predecessors' research on it are summarized.Second,the relationship between image quality and UV-plane coverage is discussed.The image qualities of point target and extended target from uniform and nonuniform UV-plane coverage are analyzed.The results show that the large enough radius and the small enough sampling interval of UV-plane coverage are needed for the ideal PSF.When the maximum radius of UV-plane coverage is certain,reducing partial UVplane coverage will not reduce the width of PSF main lobe.When imaging the expanded target with uniform UV-plane coverage,the sampling interval and target size decide whether the image is aliasing.Third,the relationship between interferometric array configuration and UV-plane coverage is discussed.The characteristics of UV-plane coverage of different array shapes are analyzed.A method to design interferometric array configuration for expected UV-plane coverage is proposed.This method is good at design complex UVplane coverage.Fourth,the imaging resolution of common array configurations is studied.The point spread function simulation results of circular shape and Y-shape arrays with different aperture number and location are given.The results show that effective UV-plane coverage plays the most important role in deciding the intensity of PSF side lobe.With the aperture number increasing,the intensity of PSF side lobe of different array configuration decrease with gradually reduced speed.Fifth,a method to increase UV-plane coverage by moving the apertures when the aperture number is insufficient is discussed.A thought that finding the frequency components with high amplitude firstly and then obtaining other frequency components is proposed.To find the frequency components with high amplitude,an array configuration optimization method is presented.This method is able to find the optimal aperture locations fast,which provides the basis for subsequent aperture movement.Finally,an array configuration design is given when the interferometric array works with a large aperture telescope.The aperture number is decided firstly,and then the array configuration is designed according to the UV-plane coverage requirement.This method can obtain satisfactory array configuration,so that high resolution and high quality imaging can be achieved.