Study Of High Ratio Continuous Zoom System

In order to response to the market demand,in this article,we had a comprehensive understanding of the zoom optical system with large zoom ratio.Firstly,the design model of three component continuous zoom optical system is established.Based on the model,two large zoom ratio continuous zoom optical system had been designed.One of both systems was based on the 1920×1080 HD imaging CCD,the focal range is 6mm~600mm,the zoom ratio is 100 x,the range of F/# is 3~9.The system adopted a positive group compensation optical system structure,and three groups of independent motion to achieve continuous zoom.The system used spherical lens and CDGM glass material,greatly reducing the design and processing costs.In the article,the MTF?spot diagram?distortion of the system and so on had been analyzed.In the process of continuous zoom,the transfer function curve of the zoom optical system approached the diffraction limit at the central field of view.On the spot diagram,spot radius was less than the pixel size of detector.The maximum distortion occurred at the short focal and the value of the maximum distortion were less than 9%.In this article,two methods were used to design the curves of cam.One method was to use the software Code V to prepare the macro program to get the position of the moving component,and then through Origin table fitting into the curve.The other method was based on the mathematical model using Matlab programming.The cam curves obtained by the two methods were smooth without inflection point,and the similarity is high.The correctness and feasibility of the mathematical model are illustrated.The design result proves that the zoom system has the smooth zoom cam curve,high zoom ratio and excellent image.Under the guidance of the model,an example of a mechanical compensation continuous zoom optical system with compact structure,a large zoom ration,high resolution was designed matching 640×512 cooled detector with staring focal plane array.The spectral band of the system was 3.7~4.8?m,and F number was 4,achieving the zoom focal 9~740mm,a large zoom ratio of 80 x.By the virtue of secondary imaging structure and two 45°reflecting mirrors to fold the system.It was analyzed the continuous zoom system from MTF?spot diagram and narcissus.The design results prove that the zoom system has great narcissus controlled features excellent image and it has also been found to apply infrared imaging system matching with advanced middle wave detector greatly.