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During the temperature difference of 10℃~230℃,three kinds of Shack-Hartman measuring methods are used to contrast atmospheric coherence length r0 with quadrant detector(QD),and Shack-Hartman(SH) and photomultiplier tube(PMT) respectively are applied to contrast refractive index structure parameter C2n with scintillation power spectrum.The experimental results show that: for r0,the stability of QD decreases more obviously than SH when there is strong turbulence,and for three Shack-Hartman methods,DIMM overcomes problems such as device jitter but brings in problem of inconsistency in direction which wave front method can avoid;for C2n,SH is more precise than PMT which fitting correlation coefficient is up to 0.96;for scintillation power spectrum,the maximum frequency SH tested is 15 Hz higher than that of PMT when it is 200℃ influenced by noise;through the analysis of Shack-Hartman sub-aperture scintillation power spectrum,the scintillation power spectrum is not able to be measured precisely and different sub-apertures accomplish the measurement turbulence uniformity when the same sub-aperture incident intensity is not in the CCD response linear interval.The results will provide an optimal test method and theoretical basis for turbulence cell.

In order to meet the practical requirement of airborne infrared searching and tracking systems,a dual Field-of-View(FOV) middle wave(MW) infrared optical system is designed based on the MW cooled detector with 320 pixel×250 pixel and a staring focal plane array.The system adopts the secondary imaging structure and a shield is installed in the first image surface station to reduce the stray light effect.The design results show that the system has a 100% cold shield efficiency;F number of the system keeps a constant as 4 and the image surface remains stable when only one piece of the optical lens is moved to switch the focus length between 800 mm and 400 mm;the field curvature and the distortion are less than 0.04 mm and 2.5%,respectively,and the MTF is more than 0.5 at 16 lp/mm.Obtained results demonstrate that the image quality meets the operational requirement.

This paper reviews the outstanding advantages of space laser communication and gives the operating plans of main foreign communication links and their technological parameters.It describes the present situation of space laser communication in the United States,Europe and Japan in detail,and explains the key technologies of space laser communication.It points out that the transmission speed of the laser communication will be faster and faster in future and the communicating model also can be changed from the points to points to the relaying repeater and constructing space communication networks.Finally,this paper introduces the development of space laser communication briefly in China.

The UV atmospheric transmission theory and the non-line of sight single scattering channel model were introduced.According to the model,the transmission loss caused by atmospheric channel under different structure design was quantitatively analyzed.Attenuation was quantitatively simulated under different atmospheres,communication patterns and structure parameters.Experimental results show that attenuation increases with increasing transmission distance;under different visibility,attenuation increasing different,and the higher visibility,the less attenuation,the far transmission distance;transmission distance increases with decreasing launching elevation and receiving elevation,and influence degree of launching elevation is more series than receiving elevation;transmission distance increases with increasing beam divergence angle and decreasing field angle,and influence degree of field angle is more series than beam divergence angle.

In order to satisfy the requirement of space optical communication system,and ensure relative stabilization of beaconing laser spot energy detected by photoelectric detector,an device for dynamic stabilizing laser energy is developed and dynamic light-adjusting technology of high frame frequency CCD camera based on liquid crystal is investigated.Compared with mechanical and electronic shutter,it proves the feasibility of dynamic light-adjusting technology based on liquid crystal.Then combined with the characteristic of space optical communication system,it is discussed the dynamic light-adjusting principle of high frame frequency CCD camera based on liquid crystal in detail.Finally,it presents the principle block diagram of the device,data and result of experiment.Experimental results indicate that the dynamic light-adjusting technology based on liquid crystal spatial light attenuator can achieve energy autocontrol of beaconing laser without moving optics,thereby ensuring relative stabilization of laser spot energy detected by photoelectric detector.It proves the feasibility of dynamic light-adjusting technology based on liquid crystal,at the same time it is pointed that liquid crystal as a new type dynamic optics module with flexible adjusting have wider application foreground in space optical communication system.

Aiming at stabilizational tracking technology for atmospheric laser communication system,sensitivity characteristics of the beam position detectors(CCD and QD) were analyzed.Five kinds of turbulence effects such as beam wander,intensity fluctuations,dispersed spot,angle of arrival fluctuation and beam spreading for tracking precision and their mathematical models were discussed.Then,simulation results of turbulence effects under various conditions were analyzed.Both the theoretical analysis and the experimental results show that tracking error of shape center capturing algorithms is less than tracking error of centroid localization algorithm.

The non-line of sight single scattering channel model and its solution in ellipsoidal coordinates are introduced.According to vertical transmitter-receiver model,the influence of atmospheric channel on ultraviolet communication system is analyzed.Under different weather conditions and different communication distances,the transmission loss,time-delay and pulse broaden etc.caused by atmospheric channel are quantificationally analyzed and simulated.The simulation results show that:the curve of energy attenuation with visibility dependence has inflection point that the better weather and the higher visibility do not result in greater system receiving energy;when the visibility equals to 18 km,the minimum of energy attenuation occurs;energy attenuation nonlinearly increases with the increase of communication distance,and the energy attenuation is almost 100 dB when the communication distance equals to 1 km;with the increase of the communication distance,both time delay and pulse broaden approximately linearly increase;the time delay is close to 5 μs and pulse broaden is greater than 10 μs when the communication distance equals to 1 km.