The Research And Implementation Of Multi-Projector Mosaic Based On Camera Calibration

Large format high-resolution display systems are used in scientific visualization, industrial design, virtual manufacturing, and military simulation and entertainment applications. It is expensive to build such system by use large display wall or high quality projector, so the research that several projectors tiled to create a seamless, high-resolution display is more practical value and practical significance.There are three main aspects of projector mosaic: geometric calibration, color calibration and intensity blending. Geometric calibration is needed to remove the discontinuity caused by misaligned projectors in the overlapped regions; Due to photometric imbalance within and among the projectors, color calibration is needed to achieve uniform effectiveness of such a display; In order to seamlessly merge the images without any obvious overlapped region, intensity blending is needed.On the basis of previous research, the paper study and implement an approach based on camera calibration to constructing a large display by integrating multi-projectors. The research work is as follows:(1) The use of an ordinary camera as image acquisition and calibration equipment Because of the camera distortion, using the Zhang Zhengyou camera calibration method to calibration, and then correct the photographs captured by camera. The camera calibration ensures the theoretical correctness in the follow-up corresponding calculation.(2)Projecting black-white chessboard at the flat display screen, and getting the chessboard key point from projected images and captured images by using computer vision technology. The paper implements the multi-projector automatic geometric correction by calculating the homography between projected images and captured images.(3) The paper uses a nonlinear optimization method for the projector color correction. Color correction depends on the projected color and standard color. In order to obtain correspondence, each projector projects color chessboard at the display screen. Using camera to record every projection color value, and then calculating the homography between projected color and standard color.(4) Using the quadratic function to calculate the pixel weight in the intensity blending, and making its weight distribution uniform. According to the pixel position in the projector projection intersection, calculating the distance to the nearest side and making it as the variable of the quadratic function. The quadratic function calculates and corrects the pixel intensity value.Apart from the projects and computers, the system uses only an ordinary camera as a calibration tool, the camera has no specific demands even with distortion would not affect the final result. With the popularity of the camera in mobile phones and other devices, use of the calibration tool widely available, it greatly reduces the cost of the projector mosaic. The implementation of the projector mosaic is convenient; the approach can be used effectively to the large screen display in the schools, shopping malls and even the office, so that people can enjoy more charm of a high resolution, large format display in the fields of information interaction and digital entertainment.