A design of a laser communications optical system with high transmitting and receiving performance is given. The traditional on-axis Cassegrain optical antenna has the default that the transmitting and receiving power decreased greatly because of the obscuration of the secondary mirror. Considering that the eccentric-pupil Cassegrain optical antenna is designed. The optical antenna system in transceiver has been designed by means of CODEV software. It improves the efficiency of transmitting and receiving power effectively. Its properties have been analyzed, such as gain, image quality, and transmission efficiency. Meanwhile, the materials of optical elements have been analyzed. The power decline curve has been obtained by means of the detailed analysis of antenna system in partial axis situation. The system includes transmitter channel, receiving channel and experiment channel. It can realize the functions of transmitter-receiver isolation and multi-light ways using dichroic mirrors and beam splitting prisms. The system volume and weight are reduced greatly. The complexity of conventional laser communication system is reduced enormously at the same time. It has important reference significance and application value.
The fine pointing mechanism of the Acquisition, Pointing and Tracking (APT) system in free space laser communication usually use four-quadrant detector (QD) to point and track the laser beam accurately. The positioning precision of QD is one of the key factors of the pointing accuracy to APT system. A positioning system is designed based on FPGA and DSP in this paper, which can realize the sampling of AD, the positioning algorithm and the control of the fast swing mirror. We analyze the positioning error of facular center calculated by universal algorithm when the facular energy obeys Gauss distribution from the working principle of QD. A database is built by calculation and simulation with MatLab software, in which the facular center calculated by universal algorithm is corresponded with the facular center of Gaussian beam, and the database is stored in two pieces of E2PROM as the external memory of DSP. The facular center of Gaussian beam is inquiry in the database on the basis of the facular center calculated by universal algorithm in DSP. The experiment results show that the positioning accuracy of the high-precision positioning system is much better than the positioning accuracy calculated by universal algorithm.
Celestial navigation subsystem of airborne celestial/inertial integrated navigation system periodically correct the positioning error and heading drift of the inertial navigation system, by which the inertial navigation system can greatly improve the accuracy of long-endurance navigation. Thus the navigation accuracy of airborne celestial navigation subsystem directly decides the accuracy of the integrated navigation system if it works for long time. By building the mathematical model of the airborne celestial navigation system based on the inertial navigation system, using the method of linear coordinate transformation, we establish the error transfer equation for the positioning algorithm of airborne celestial system. Based on these we built the positioning error model of the celestial navigation. And then, based on the positioning error model we analyze and simulate the positioning error which are caused by the error of the star tracking platform with the MATLAB software. Finally, the positioning error model is verified by the information of the star obtained from the optical measurement device in range and the device whose location are known. The analysis and simulation results show that the level accuracy and north accuracy of tracking platform are important factors that limit airborne celestial navigation systems to improve the positioning accuracy, and the positioning error have an approximate linear relationship with the level error and north error of tracking platform. The error of the verification results are in 1000m, which shows that the model is correct.
In order to improve the reliability and working performance of the optical window for airborne optoelectronic equipment, we conduct the aerodynamic analysis of airborne optoelectronic equipment under different flight speed, and get the aerodynamic load distribution of optical window under three different typical flight speed. By building the model of the optical window and simulating the model with the method of CFD, the deformation and stress caused by aerodynamic loading under different thickness of the optical window have been got. The results shows that the thickness of the optical window at 10mm could best meet the requirements of structural strength and quality. Then we analysis the impact of the deformation of the optical window on the imaging quality of the optical system. The deformation of the optical window is very tiny, and it is deformed from the flat into a spherical whose radius is very large. The MTF of the optical system after deformation are basically the same as its MTF before deformation. Thus, the impact of the deformation of the optical window on the imaging quality of the optical system can be ignored. The results of the analysis provide important reference for the design of the optical window for airborne optoelectronic equipment.
In order to improve high-speed laser space optical communications terminal receive energy and emission energy, meet the demand of mini-type and light-type for space-based bear platform, based on multiple-reflect coaxial optical receiving antenna structure, while considering the installation difficulty, a high-efficient optical system had been designed, which aperture is off-axial, both signal-receiving sub-optical system and emission sub-optical system share a same primary optical path. By the separating light lens behind the primary optical path, the received light with little energy will be filtered and shaped and then transmitted to each detector, at the same time, by the coupling element, the high-power laser will be coupling into optical antenna, and then emitted to outside. Applied the power-detected optical system evaluate principle, the optimized off-axial optical system's efficiency had been compared with the coaxial optical system. While, analyzed the Gauss beam energy distribution by numerical theory, discussed that whether off-axis optical system can be an emission terminal, verify the feasibility of the theory of the design of the system.