Study On The Technique Of Real Time Alignment Of Optical System Of Telescope

As the telescope aperture is increasing and the optical system complexity is upgrading, dynamic alignment errors of the telescope in work process also increase. In order to make the telescope keeping best working state for a long time, the dynamic alignment error of the telescope must be corrected in the real time. In this paper, the real-time alignment method of the telescope optical path was studied, and a concrete implementing scheme was proposed about the core problem.Through in-depth study of the static alignment technology of telescope optical path, combining the demand of real-time alignment, the basic method of the real-time alignment of telescope optical path was put forward. The basic steps were as follows:quantifying the alignment error, designing the alignment detection optical path, testing information processing, solving the alignment error, the evaluation of the alignment state, and the correction of the alignment error. Among them, alignment state evaluation referred to quantitatively evaluating working condition according to the detection results of telescope working optical path. The correction process of the alignment error should be quick and smooth to ensure the stability of the working optical path. The basic method clarified the basic requirements and the work content of the real-time alignment, and it had a certain guiding significance.The algorithm for solving the alignment error was the core part of the real-time alignment of telescope optical path. The accurate solution of the alignment error or quantification of the judgment conditions and boundary conditions were mainly studied. The algorithms for solving the alignment error based on image information and based on wave front information were studied respectively.In terms of using image information to solve the alignment error, dynamic optical model was used to study the discrete array light source, out-of-focus stellar images and the slewing mechanism of the secondary mirror to solve the alignment error. Alignment error algorithm based on discrete array light source was using the discrete array reference light source to produce reference light, and then calculating the primary and secondary mirror alignment error through the change of light spot in the detector from the focal position. The result indicated that this method could obtain the alignment accuracy of37μm and50". The algorithm for solving the alignment error based on out-of-focus stellar images was using the secondary mirror to block the incident light, and calculating the primary and secondary mirror alignment error of the telescope according to the information inside and outside the ring of the out-of-focus stellar images. This algorithm for solving the alignment error was used for the alignment experiment of the primary and secondary mirrors of the RC horizon telescope, the best angular resolution of2.4" had been obtained. The algorithm for solving the alignment error based on the secondary mirror rotation was using a linear light source to generate a reference light. Then, the movement trajectory of the spot during the secondary mirror rotating was used to calculate the alignment error of the primary and secondary mirrors.In using the wave front information to solve the alignment error, the algorithms for solving the alignment error based on linear fit and astigmatic decomposition were studied. Linear fit algorithm referred as follows:firstly, a linear mapping relationship was established by analyzing the relationship of the Zernike coefficient between the pupil front wave error and the alignment error. Then the alignment error could be obtained according to the linear equations after the pupil wave front error was obtained. The results indicated that this method could achieve the alignment accuracy better than1μm and1". The algorithm for solving the alignment error based on astigmatic decomposition firstly obtained the size of the astigmatism with only two alignment error by astigmatic decomposition, and then solved the alignment error by the coma items. The results indicated that this method could achieve the alignment accuracy better than5μm and0.5"The alignment problems of the telescope work light and the detector module were mainly reflected in the stability of the relative position. To address the issue of multi-light path detection of quantum communication, small detection field of view, the real-time alignment of the work light and the detector module were achieved by the common optical axis detection method. The results of indoor test and outdoor experiment both achieved the expected goal and this method proved to be effective.Through the study on the real-time alignment of telescope optical path, a basic method to align the optical path in real time was proposed, and the solution for alignment error was in-depth studied. The research had some reference value on practical applications of engineering.