Optical And Mechanical Structure Design And Research On Image Motion Compensation Technology Of Whisking Broom Space-based Infrared Imaging System

Space-based infrared imaging system is a kind of optical precision instrument,which is used as space vehicle as carrying platform and is applied to space environment.It is the main function of obtaining the images of ocean,ground and space moving objects.The spectrum has unique application value in night vision,smoke transmission and fog penetration.Therefore,there is great demand for the development of space-based infrared imaging system.In this paper,with the requirement of space-based infrared detection,based on the project of a space-based platform,the research is carried out on an infrared imaging system,which is applied to a low orbit solar synchronous orbit,effective width of 100 km,ground resolution about 10 meters,and working wavelength of 3?m-5?m.The main contents of this paper include the following aspects.1)In view of the requirement of technical index,this paper emphatically analyzes how to realize large width while guaranteeing high resolution,and compares various schemes,chooses the working mode of vertical rail swinging to meet the width requirement,and based on this mode of work,the coverage ability of infrared imaging system is analyzed.2)As the load of the two-dimensional rotation mechanism of the infrared imaging system,the weight characteristics of the infrared imaging system,including the weight,the center of mass and the moment of inertia,have a great influence on the control level of the servo system,and the installation space of the infrared imaging system is strictly limited by the satellite platform.Based on this,this paper puts forward the idea of compact,light and small design of lens.Through the rational selection of optical system structure,reasonable planning optical system turning direction and turning position,the reasonable layout of various components inside the lens is realized,achieved the goal of compact,light and small design of lens,and the telephoto ratio of lens reaches 0.21.3)The space environment of the space-based infrared imaging system is extremely complex.The periodic variation of the external heat flow and the alternating of the cold and black space will produce a great temperature difference.This is fatal to the infrared system.In this paper,the thermal environment adaptability of the infrared imaging system is designed.On the one hand,the non thermal design method is adopted to improve the adaptability of optical system,on the other hand,we use thermal control design to control the thermal environment of optical system.4)In this infrared imaging system,the target orientation is realized by the satellite attitude adjustment.The image of the target area is realized by its own swinging imaging working mode.In this mode,the image shift will generate in the flight direction and the yaw direction.Therefore,On the one hand,the system should have two dimensional rotating mechanism for imaging scavenging,on the other hand,the system should have two dimensional compensation mechanism to compensate for the image shift produced by the satellite motion and the scavenging.Based on this,a kind of compound axis rotating mechanism with coarse and fine tracking ability is designed,and the efficiency of infrared detector is raised and expanded.At the same time,the influence on the stability of the whole star platform is reduced,and the design process and selection method of the composite axis rotating mechanism are introduced in detail.5)The two-dimensional turntable is the realization unit of the rough tracking,its control residuals size directly affects the success or failure of the precision tracking.In this paper,a design method combining the design of two dimensional turntable with the requirement of servo control bandwidth is proposed.6)Considering that the system must undergo a rigorous mechanical environment in the process of satellite transportation and launch,the structure design requires high stiffness,high strength and low weight.The mounting bracket used to carry the camera body is the main load-bearing component in the whole system,and it has a very important influence on the mechanical performance of the camera.In this paper,a full carbon fiber material,high stiffness,high stability,high light weight,truss type mounting bracket is designed,fully utilized the advantage of high axial stiffness of carbon fiber wire,the designed mounting bracket is about 350 mm x 430 mm x 360 mm,the first step characteristic frequency is about 222.7Hz,the bearing mass is about 16 kg,and the weight of the body is only 3.8kg,which can meet the needs.7)The infrared camera designed in this paper is the composite axis rotation mechanism of the space-based moving base.If the image shift compensation can not be realized,the imaging quality of the camera will not be guaranteed.This paper uses the coordinate transformation method to establish the image shift compensation model of the two dimensional composite axis rotation mechanism of the space-based moving base,and uses the Monte Carlo algorithm to analys the image shift compensation residuals.Finally,the effectiveness of the system function and the image shift compensation model is verified by semi-physical simulation test and the external scene imaging test.