Research On Pointing Error And Imaging Quality Of The Three-axis TDICCD Aerial Camera

Aerial remote sensing is a remote sensing technology to obtain ground target information from the air.It has the characteristics of flexibility,wide detection range,and timeliness.Aerial camera imaging by push-broom and swing-broom has become an important research direction of aerial remote sensing in recent years.How to ensure the pointing accuracy of the optical system and the working stability and reliability of the aerial camera is one of the difficulties,and it is also the key to ensuring the imaging quality of the aerial camera.The errors existing in the processing and assembly of aerial camera parts will affect the installation and positioning accuracy of internal optical components to varying degrees,which will lead to the optical axis pointing error.In addition,the vibration of the aircraft during flight will inevitably affect the relative position relationship between the optical components inside the aerial camera,resulting in blurring and distortion of the captured image.Therefore,it is of great theoretical significance and engineering application value to further improve the imaging performance of aerial cameras to study the influence of errors on the optical axis pointing accuracy and error correction methods,and to carry out the analysis and evaluation of the impact of vibration on the optical axis pointing and imaging quality.This paper takes the three-axis TDICCD aerial camera with push-broom and double-swingbroom functions independently developed by the project team as the research object.Aiming at the problems existing in the analysis of the optical axis pointing error,the optical axis pointing error correction,and the impact of vibration on the imaging quality,the specific work is as follows:(1)The design of the opto-mechanical system of the three-axis TDICCD aerial camera is carried out.The optical system design is carried out based on the short-range TDICCD imaging scheme of the aerial camera.It is determined that the aerial camera realizes flexible imaging with a large field of view through the rotation of three axes based on the push-broom and doubleswing-broom.The structural design of the optical component support structures and the rotating axes is carried out.The torque motors and photoelectric encoders are selected according to the servo control system.(2)A method for analyzing the optical axis pointing error of the three-axis TDICCD aerial camera is proposed to study the influence of the errors existing in the processing and assembly of the aerial camera parts on the optical axis pointing error.The errors are divided into static errors and dynamic errors for discussion.Based on the homogeneous coordinate transformation and multi-body system kinematics theory,the optical axis pointing error model of the three-axis TDICCD aerial camera is constructed through the analysis of the topological structure of the aerial camera.The mapping relationship between various errors and optical axis pointing error is established,and the variation law of optical axis pointing error with various errors is clarified.(3)A study of optical axis pointing error correction for the three-axis TDICCD aerial camera is carried out.A semi-parametric modeling correction method for the optical axis pointing error is proposed for nonlinear errors.The optical axis pointing error data is obtained through experiments and the model parameters are identified based on the genetic algorithm.Optical axis pointing error correction experiments are carried out.The experimental results show that both error correction methods can greatly reduce the optical axis pointing error.The correction errors of the parametric model have the problem of large differences in values between individuals.Compared with the parametric model,the correction errors of the semiparametric model are further reduced and have better stability.The error correction effect of the semi-parametric model is more significant.(4)An analysis and evaluation method for the influence of vibration on the optical axis pointing and imaging quality of the three-axis TDICCD aerial camera is proposed to explore the mapping relationship between vibration and imaging quality.The optical axis pointing disturbance trajectory caused by vibration is modeled based on ray tracing and homogeneous coordinate transformation.The vibration modulation transfer function(MTF)solution model and the TDICCD vibration simulation imaging model are established based on statistical moments.The impact of vibration on the optical axis pointing and imaging quality is analyzed and evaluated through the optical axis pointing disturbance trajectory,MTF,and TDICCD simulation image.The full-link comprehensive theoretical analysis from structural vibration response to imaging quality evaluation is realized.(5)The dynamic analysis and vibration test are carried out in order to verify the analysis and evaluation method of the impact of vibration on the imaging quality of the three-axis TDICCD aerial camera.The dynamic analysis of the aerial camera is carried out and the accuracy of the analysis results is verified by the modal test.The aerial camera vibration test is carried out to obtain the vibration displacements of optical components.The results show that with the increase of vibration,the optical axis pointing offset increases,the vibration MTF decreases significantly,the difference between the TDICCD simulated images and the original images further increases,and the image quality decreases rapidly.The aerial camera vibration imaging test is carried out to verify the validity and accuracy of the analysis and evaluation method for the impact of vibration on imaging quality.This paper focuses on the analysis of the optical axis pointing error,error correction,and research on the impact of vibration on the imaging quality of the three-axis TDICCD aerial camera.The optical axis pointing error analysis and correction method and the semi-parametric modeling correction method are proposed to greatly improve the optical axis pointing accuracy.The analysis and evaluation method of the impact of vibration on the optical axis pointing and imaging quality is also proposed to realize the comprehensive theoretical analysis of the impact of vibration on the imaging quality.A complete analytical link is constructed from structural vibration response to imaging quality evaluation.