Multifunctional Astronomical Theodolite Image Acquisition Systems And Image Processing Systems

In recent years, the some scientists of Yunnan Astronomical Observatory have put forward a novel method for astronometry applications. They try to get the information about variation of underground substances by measuring changes of the local plumb line. This information maybe related to one of the premonitory symptoms of earthquake. The main measuring apparatus in the method is an asronometric telescope, called Multi-Function Astronomical Transit. As an important part of the telescope, an image acquisition system and an image processing system have to be designed and developed with the telescope’s being manufactured at the same time.This thesis describes development works and related results of the image acquisition system and the image processing system of the Multi-Function Astronomical Transit. First the research background and social significance of the project are introduced; then a simple decription of the mechanical structure and subsystems of Multi-Function Astronomical Transit is made in the thesis. An analysis and comparation of four methods in common use for image acquisition and transmission is made. And Ccombining with design requirements of the telescope, we determine general design scheme of the image acquisition system. When telescope is working, two trigger signals are generated by the telescope control system. They are used for control cameras grabbing, one for the digital camera, another for the two analog cameras. The two frame grabbers are separately mounted in two image workstations. Two frame grabbers and three cameras all operate in external trigger mode. The images acquired by image acquisition system are saved quickly in the computers. The image processing system is a software system, in which there are two algorithms:searching the star and centering the star. Since the image acquired by digital camera in the telescope is different from other astrometric telescopes, there is only one star in the image. Thus a more efficient searching algorithm, called searching single star method, is presented, that is, making the data smooth with a suitable method and then finding maximum value of pixels as the initial centroid of the star. After comparing the commonly used centering methods in astrometry and considering adaptability, accuracy, calculation volume and programming difficulty of these methods, we decide to use the two-dimensional modified moment method as the method of centering the star. Our method has a little difference with other methods in threshold selection. The results of image-processing are saved in the computers based on a required format. The time of the trial observation is already up to six months. So lots of data are acquired. A analysis of data processing proves that our design and development of the image acquisition system and the image processing system are correct.The research work of this dissertaion are supported by the Special Fund of Yunnan Province (YOHZ021001) and the Major Projects of Science and Technology Cooperation of Kunming (10H100102).