Research On Airborne Multi-band Common Aperture Dynamic Imaging Optical System

As an important means of acquiring information for military and civilian tasks such as high-definition remote sensing,mapping,searching and rescuing and so like,the functions and performances of the electro-optical(EO)payload have put forward new requirements of multi-band,long-range,high-precision dynamic imaging and detection.Moreover,due to the constraints of size,weight,power and cost(SWa P&C)constraints,improve the functional density of the payload is the best way to go.Furthermore,the future direction of EO payload can be described as from single-band split aperture to multi-band common aperture,from static imaging to continuous scanning to step gaze imaging,from a single field of view(FOV)to multi-FOV to continuous zoom FOV,and from the separate design of payload and platform to the direction of integration of optical-mechanical and control elements.An in-depth application study of these aspect has been done in this dissertation.According to the research background of multi-band co-aperture dynamic imaging optical system,the basic theories,methods and preferred optical configurations required are introduced from the dynamic imaging theory,the characteristics of imaging motion,and the comparison of the overall optical scheme.The existing dynamic optical systems and their practical applications are summarized,as well as their respective advantages and disadvantages.A dynamic optical imaging model using the method of the chi-square coordinate transformation is established.On the basis of this model,the influences of various parameters such as telescope magnification,detector integration time,platform angular scan speed,and imaging field of view on the residual image motion after compensation are analyzed.The results can provide a quantitative reference for the design of similar dynamic optical systems,especially the front telescope with large linear area.Two design and corresponding simulation analysis are carried out for the technical requirements of two different payload with pendulum scanning imaging function.The design of the continuous zoom optical system with stable external pupil and internal stop is studied.To address the pupil drift problem in the design of modular zoom optical system,pupil stability differential equation group is introduced,the image plane constant and pupil stability differential equation group in the zoom system is constructed,and the numerical solution of the equations is discussed.Two different design of infrared and visible continuous zoom optical systems with external pupil and internal stop are given,and the implementation and performance of the modular EO payload system are discussed with a typical front telescope.By introducing the free-form surface type into the design of low-noise infrared optical systems,two types of cooled infrared optical systems with external pupil and different surface types are designed,and the effects of different structures on the internal background radiation are compared.The comparison result show that,under the same technical requirements,the reflective objective has apparent advantages in transmittance,ghost disc and narcissus control;in the same operating temperature range and effective working waveband,internal background radiation of the reflective objective is notably reduced compared to the refractive objective,meanwhile,the implementation of thermal control scheme are simplified.Freeform reflective objective is a preferred configuration for the infrared thermal detection payload,which is conducive to the engineering realization of infrared detection of faint targets.By applying the research results of this dissertation,a multi-band common aperture dynamic imaging optical system is designed.The reflective front afocal telescope,the rear visible and mid-wave infrared zoom objective with external pupil,and the free-form long-wave infrared detection objective are completed and combined in the optical design software.The engineering feasibility of the design scheme is verified by the development and test of prototype.