| Along with the increasing of the tenure of cars all over the world year after year, the problems of traffic safety has become more and more serious. Automobile active safety system, which bases on machine vision and image processing, has been more and more applied to automobile industry recently. Vehicle top-view technique is the most popular among them. After multiple cameras take the real time pictures around the car, it conducts some image processing to turn them to360degrees2D overlooking screens. This technology can provide auto panoramic image with no blind spots to the driver in real time, which is greatly helpful to safety driving.The article describes an embedded vehicle top-view system based on four ultra-wide-angle fish-eye camera. This system involves several key technologies, such as fish-eye image distortion correction, geometric transformation of images, image stitching, design of software and hardware in embedded system and so on. Firstly, after the analysis of the vision imaging coordinate system, an fish-eye camera imaging model is established. Internal and external parameters of the camera are calculated according to the model. By doing inverse operation to the data, we can get the corrected image and analyze the accuracy of the fish-eye camera model and calibration algorithm. Secondly, we can start the overall design of the vehicle top-view system. Four fish-eye cameras are installed around the body of the vehicle. The video data collected in time is transferred to the video decoder to be decoded. Later it is delivered to DSP(Digital Signal Processing). DSP is in charge of the demarcation and calculation of the data. After the demarcation and calculation, image maps and parameters forms of image location are created in the Flash memory. System will generate panoramic images directly by using the forms and then output panoramic virtual image. Then, the article analyzes some key technologies in the whole software and hardware system. Vehicle top-view system contains fish-eye video camera, video decoder, DSP controller, board video display, image capture card and calibration PC. Among this section, system workflow and data flow between the parts is emphatically introduced. Finally, design the overall framework of embedded software system. The software part is divided into three parts. They are hardware drivers, module application and integrated application. On this basis, three main threads, which are system management, signal acquisition and image processing, are wrote to complete the embedded software development in accordance with the requirements of the embedded operating system. The original multiple camera calibrates each camera respectively, which is time-consuming and labor-intensive. Through some simulation experiments, the fact is found that internal reference of automotive-grade fish-eye camera has great consistency, which implies we can apply the same internal reference to the same batch of cameras. This action has little effect on the quality of panoramic picture, but greatly reduces the complexity of embedded application development and loading calibration.Test experiments of vehicle top-view system in this paper were carried out on both model car experimental simulation platform and real vehicle platform. The experimental results show that the system image is clear, natural and has a good real-time. It can effectively reduce the driver’s blind spot and is an effective visual enhanced active safety assistance systems with high research and pragmatic value. |
