Optical System Design Of Large Zoom Ratio Security Lens

Security lens is an important part of the security monitoring system and determines the imaging effect of the security monitoring system.In recent years,China's security monitoring strategy has developed in the direction of comprehensive urban and rural monitoring.The monitoring situation in cities is complicated,the rural population is sparse,and it is difficult to arrange the lines,which makes the market demand for zoom security lens,especially the large zoom ratio security lens,increasing day by day.Aiming at this development trend,a large zoom ratio security lens with a zoom ratio of 25 times is designed.This paper analyzes various zoom forms and selects the four component positive-compensated zoom form as the lens zoom structure.This paper introduces the Gauss theory of this zoom form,and expands the Gaussian initial parameters of the zoom system on the original basis,providing more possibilities for Gaussian calculations.After the Gaussian parameters calculation,graph of declination analysis,initial structure construction and optimization of ZEMAX software,the system design of the large zoom ratio security lens is completed.The large zoom ratio security lens designed in this paper is composed of four component 16 lenses,with a focal length ranging from 7.4mm to 185 mm,an F number of 5,and a 1/1.8-inch CCD,which has a CS-type interface,as the image receiver.The working distance is longer than 12 mm.Because the security lens requires a small volume,an aspherical optical plastic lens is added to the system to reduce the volume and the manufacturing cost.In the end,the total optical length of the system is less than 160 mm and the maximum lens diameter is less than 60 mm.At the same time,the imaging quality of the system is good,the on-axis point is greater than 0.3 at the cut-off frequency of 135.5 lp/mm,and the off-axis point is greater than 0.2 at the cut-off frequency.The cam curve of the system is obtained by using the point-fitting method.The curve is smooth without inflection points,and has a gentle slope.the image surface is stable during zooming,and the mechanical structure will not be stuck.Finally,ZEMAX is used to analyze the tolerance of the system,and the results meet the processing requirements.