Research On Central Location Algorithm Of Laser Mixed Spots In CCD

During the process of detection of pavement height,the photoelectric receiver(CCD)of the laser displacement sensor is saturated,which causes the center position of the spot to shift,and leads to errors in the collected height data.In order to improve the detection accuracy of pavement height,three typical energy distribution models of mixed spot are studied in this paper.The reasons for the saturation of the spot are analyzed.The method of locating the main spot center of mixed spot is proposed.A laser displacement sensor based on the method of locating the main spot center is designed.Firstly,the laser displacement sensor is analyzed and designed from two parts,which are the optical system and circuit system.In the optical system,combined with the accuracy and volume requirements of the system,the appropriate optical path structure model is selected,and the optical parameters are designed.The in-depth analysis of the constant focusing optical path is carried out,and a direct optical path that satisfies the Scheimpflug condition is designed.In the circuit system,the functions and characteristics of each circuit are comprehensively analyzed,the driving circuit of the CCD,amplifying circuit and sampling circuit are designed,and the connection between the circuits is studied.Secondly,three typical energy distribution models of mixed spot in CCD are studied and the method of locating the main spot center of mixed spot is proposed.The optical imaging principle and saturation imaging principle of CCD and the cause of the formation of mixed spot are analyzed.Using Matlab simulation technology,three typical light intensity distribution models of the mixed spot are obtained,and analysis shows that the saturation of the mixed spot is related to the incident angle of the light and the incident light intensity.A variety of spot center location algorithms are studied and compared.The results show that the calculation error of centroid method is significantly lower than that of other algorithms.On the basis of the different number of peak values in three typical light intensity distribution models,the mixed spot is divided into three categories: two peaks,one peak and zero peak.According to this classification,three corresponding algorithms for calculating the center position of the main spot are designed,which are by derivative method,distance scalingmethod,OLS-RBF neural network prediction method.The centroid method and the method designed in this paper are used to locate the main spot center of the mixed spot.The experimental results show that the error of centroid method is greater than or equal to 40 pixels,while the error of the method designed in this paper is less than 5 pixels,which proves that the method designed in this paper has higher accuracy than the existing algorithm.Finally,a laser displacement sensor based on the main spot center location method is designed.The main spot center location algorithm is applied to the laser displacement sensor to measure the pavement at different heights.The measurement results reach the expected target,which indicates that the laser displacement sensor based on the main spot center location algorithm can complete the task of pavement height detection with high accuracy.