The Research Of Section Image Processing Technology In Railway Clearance Detection

Tunnel clearance detection is of great significance to ensure the safety of railway tunnel.With the rapid development of high-speed railway in recent years,the automatic detection method based on image processing has gradually become the mainstream technology.Due to the advantages of simple operation and high precision,the method of TV camera measurement has become the most widely used technique in many measurement methods.Among them,the fast and accurate extraction of laser line from the cross section image is a key step in the whole process,which is directly related to the accuracy of the calculation.However,there are many technical problems such as uneven illumination,cable,inner wall texture,and so on.In this thesis,the technology of image processing is used to study the extraction and post-processing algorithm of laser outline under the section in complex background.In this thesis,we consider the influence of the complex tunnel background on the boundary measurement,and propose a new algorithm for laser line contour extraction.The local threshold segmentation based on improved technology to preprocess the image section,combined with edge detection and line detection algorithm for detection of the linear features of the image,then analysis pixel gray value and eye tracking experiments to extract laser contour.A large number of tunnel detection results show that the contour extraction algorithm proposed in thesis has a strong stability and high accuracy,which is a good foundation for the subsequent measurement and off limits.Aiming at the phenomenon that the width of laser line is too thick and the curve is cut off,puts forward a scheme of laser line post-processing.We select the thinning algorithm to process the laser line image to get the single pixel contour,and then put forward two kinds of translation scheme to fix the position of the single pixel skeleton line.Then,the variance expression of the two schemes and the results of simulation experiments are given respectively.Finally,a fitting growth algorithm based on the connected region is proposed,which is used to fit the missing part of the laser line.The experimental results show that the proposed scheme can be used to fit the broken and missing parts of the laser line within the range of error tolerance.