| There are many advantages for the system of optical communications,such as high communication capacity,great confidentiality,lower power consumption,and strong flexibility,which have been widely applied in space optical communications.With the advancement of the technology of astronomical telescope systems and the strong need for detection of dark space objects in deep space,the aperture of optical antennas are larger and larger,which changes from hundreds of millimeters to hundreds of meters now,such as James Webb Telescope and so on.However,the larger aperture telescopes increase the difficulty of manufacturing and processing for the optical antenna.The segmented antenna is one of the effective methods for reducing the cost of large-aperture optical antennas,which has widely been applied in many fields,such as astronomical observations,high-resolution imaging,solar concentrators and so on.Detailed design,simulation,analysis and verification have been performed for the system of segmented optical antenna.Firstly,three-dimensional rotation theory is used to establish three different types of models of sub-mirror segmented optical antenna,which are planar,spherical,and parabolic mirrors.The ray tracing of the segmented optical system is performed to obtain the spot diagram on receiving plane and the size of its spot by using the vector reflection theory.The optical properties of three kinds of segmented optical antennas are compared,which are mainly the spot size and the optical efficiency.The influence of the number of circles of the sub-mirror,the eccentricity of the secondary reflector and the tolerances of the segmented optical receiving antenna system,such as tilt ray incidence and on-axial defocusing of hyperboloid secondary mirror on the performance of the entire optical antenna system is discussed in detail.It is concluded that the segmented antenna composed of spherical sub-mirrors has better optical performance,which is more practical in the application by a series of analysis and comparison.In order to reduce the number of circles of the sub-mirror and the cost of processing,a 10-millimeter segmented optical receiving antenna composed of 36 hexagonal spherical sub-mirrors was designed to satisfy requirements of Strehl Ratio,whose receiving efficiency is 80.19%.The design of large-aperture segmented optical antenna is mainly based on Matlab programming to obtain the model.Models of segmented optical antenna system,thespot diagram and profile curve of the energy distribution on receiving plane are obtained by software Tracepro,which is the same with the results of Matlab programming.In combination with software Tracepro,the correctness of the Matlab programming modeling and simulation based on the three-dimensional rotation theory and the vector reflection theory is determined.In addition,a ring-focal antenna with off-axis rotated conicoid mirrors is designed based on the problem of shade resulted by secondary mirror severely in the system of traditional Cassegrain antenna,which lead to the lower transmission efficiency of optical antenna.The Cassegrain structure of the parabolic primary mirror and the hyperboloid secondary mirror is still applied in this ring-focal antenna.The transmission efficiency of the optical system is 98.88% because of the chamfering of the center of secondary mirror.Compared with the traditional Cassegrain optical antenna with the same diameter,the efficiency is improved by 23.42%.The ring-focal antenna can be applied in the system of large-aperture optical antenna.To further explore the optical performance of the designed ring-focus antenna,the impact of off-axis defocus and other tolerances on the spot size,transmission efficiency,and aberration of the optical transmitting and receiving antenna are also discussed in this paper. |
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