Design Of Rail Image Acquisition System Based On Linear CCD Camera

Rail image defect detection is to guarantee the safety of the railway transportsafety. However, track image acquisition is the basis and prerequisite for defectdetection, and at the same time it is the key to the whole image detection system. Theapplication of the CCD technology and the machine vision technology in the industryprovides a more effective and more economical way for orbital images acquisition.Through comparing the difference between linear array camera and camera andconsidering rail site environmental requirements, we can come up with a track imageacquisition system based on linear CCD camera.According to the function and characteristics of the system, we can expound itshardware and software respectively. Setting out from the camera selection, datastorage, lighting, the mileage records and other aspects, and through analysis andcalculating the related parameters of camera, lens detailed,we can build a hardwaresystem which is suitable for track image acquisition. In the meantime, combined withthe structure of rail and carrying car, we can design the fixed bracket and thenimprove the structure. In the end, we will focus on analyzing the camera trigger,mileage records and control software building the three parts.To obtain clear and undistorted orbital images, according to the characteristics ofthe linear CCD camera trigger, pulse information is collected by photoelectricencoder, frequency doubled and guided by single chip microcomputer to judge therunning direction of bearing car. Pulse information is converted to TTL levelinformation identified by the camera.TTL level information is transmitted to thecamera through26pin interfaces to trigger camera scanning track and taking pictures.Image quality is not affected by velocity, and image data is stored in industrial PCthrough the gigabit network transmission. The role of the mileage records is mainlyrecords the distance information of carrying vehicle and ensure the position of the railimages. By getting pulse number and wheel circumference of bearing car, theprinciple is calculated to get the actual mileage which displays in real time.According to the needs of the rail image acquisition system, dual camera control software is developed. Using multithreading technology, two cameras aresynchronously controlled, which is more convenient to the user action and systemdebugging. The software consists of many windows, including camera recognition,parameter setting, data transmission and display, image storage, mileage records, etc.Each window has its own independent modules and code functions and characteristicsof each module are analyzed to realize the software modular.The hardware structure of image acquisition system is designed by AutoCAD,and the singlechip control circuit is designed by Altium Designer, using VC++6.0torealize its microcontroller programming in compile Builder6.0interface. The imageacquisition system, through a number of experiments, which verify that the imageacquisition is not affected by the velocity change of bearing car, the accuracy ofmileage records and the completeness of the information stored in the image toillustrate it satisfies the request of designing.