Research On Real-time Focusing Method Based On Parallax Ranging Of Photoelectric Tracking And Measuring Equipment

The blurring of defocus imaging caused by high-speed moving target in shooting range seriously affects the tracking performance and accuracy of photoelectric tracking and measuring equipment.Therefore,real-time focusing of photoelectric tracking and measuring equipment is required.The existing auto-focusing methods can be divided into three categories: ranging-based,image detection-based and image processing-based.The image detection method requires high illumination conditions,so the optical and mechanical structure of the equipment needs to be reformed,which affects the detection ability of the measuring head.At present,it has not been applied in the optical measuring equipment.Image processing method has no general and perfect theoretical model,high computational complexity and poor real-time performance.It's also can't meet the focusing requirements of optical measure-ment equipment.Therefore,the auto-focusing method based on ranging is mainly used in optical measuring equipment.Usually,laser,radar or intersection measurement of multiple devices are used to obtain target distance information for focusing.When laser and radar encounter small,long-range targets and poor atmospheric conditions,their low echo energy will cause the failure of reception for optical range finder.which limits the applicability of this focusing method.A real-time focusing method based on binocular parallax ranging on a single device is proposed,according to the characteristics of optical measuring equipment with multiple measuring heads and high tracking accuracy.The study of this method has important engineering application value.In this paper,the influence of the layout of the measuring head and angle error on the parallax ranging is discussed.The parallax ranging models with different focal lengths are established and the error analysis is carried out in detail.Combining with the focusing principle of optical system,the relationship between the aperture,focal length,baseline and measurement accuracy of optical measuring equipment is analyzed theoretically,in order to satisfy the focusing requirement.The results show that this method has better adaptability on equipment with small aperture,short focal length and long baseline.Namely:the parallax ranging and focusing method has good applicability for small optical measuring equipment with aperture of 100-200 mm,baseline of 120-700 mm and focal length of 400-1000 mm,on the premise that the pixel size of CCD is 5 um and the accuracy of measuring head is 0.7?.For medium-sized equipment with 200-300 mm aperture and 120-700 mm baseline,the focus requirement of 1000-2254 mm focal section can only be met.Large equipment with larger aperture and focal length will no longer be used.Combining with the specific parameters of an optical measuring equipment,the numerical simulation and real-time analysis of focusing based on ranging are carried out.Finally,the validity of the above conclusions is verified by the experimental data.