Design Of Aero Zoom Optical System Based On Ultra-small Field Of View

With the development of modern warfare,mastering the battlefield situation and the intelligence information that changes instantaneously is the key to gain the initiative of the battlefield,and it is also an important magic weapon for winning the war.This requires that the reconnaissance system not only can master the global information from a large field of view,but also can track the observation target from long distance.Therefore,the zoom system is often used in military reconnaissance fields.With the development of technology,people hope that the reconnaissance camera has a larger field of vision to take over the overall situation,and also has the ability to observe from a long distances.For the optical system,the design requirements of these two capabilities are the opposite.The former requires the optical system have a short focal length with large field of view,while the latter requires the optical system have a long focal length with ultra-narrow field of view.According to the above requirements,this paper has carried out the design and research of the zoom lens optical system with ultra-narrow field of view.Starting from the basic theory of the zoom optical system,this paper analyzes the motion process of the zoom optical system,and deduces the process of Gaussian solution of the continuous zoom optical system.Then the technical target of the system is determined,and the advantages and disadvantages of the optical systems with different zoom structure were summarized.According to the technical target,a "mixed" design method is put forward,that is,the structure form with two optical channels.One optical channel adopts the mechanically-compensated continuous zoom structure with a zoom range of 20.5 mm to 420 mm,and the field of view of this optical system can be changed from 30 to 1.5 degrees.The results of aberration analysis show that the values of MTF curve in all field of view of the system are over 0.3 at the Nyquist frequency(91lp/mm)of the CCD.It is shown from the spot diagram analysis that the spot radius are small and dense,and the energy of the spot radius is basically concentrated in the size of the pixels(5.5?m).The distortion of the system is very small,and the maximum is no more than 3%.The system also has a good uniformity of image illumination.Comprehensive analysis shows that the continuous zoom optical system has good imaging quality.Another channel uses R-C optical system design,the system focal length can reach 2100 mm,and it can achieve 0.3° of the ultra-narrow field of view.The results of aberration analysis show that the system has good imaging quality and all technical target meet the design requirements.This dual-channel zoom system combines the features of the continuous zoom and the R-C system,and it overcomes the difficulty of the single optical channel optical system to realize wide field of view and long focal length at the same time.So that the whole system can master the global information at wide field of view,and can also track and observe the target at ultra-narrow field of view from a long distance.In this paper,the tolerance of optical system is analyzed and the reasonable tolerance range is given.According to the application environment of aerial camera,the imaging quality of optical system at high temperature(60?)and low temperature(-40?)and at different atmospheric pressure environment has been analyzed.The analysis results show that the image defocusing of the continuous zoom channel will occur when the temperature and air pressure change.In this paper,the focus compensation technique is used to compensate the defocus of the image surface.After compensation,the imaging quality of the system is improved obviously,which shows that the optical system has good temperature adaptability.