The Research On Multi-projectors Large Format Mosaic

In recent years, with the continuous development of the projection display technology, large format mosaic technique has been widely used in command and control, virtual simulation training, industrial manufacturing and design, scientific research and complex decision-making, etc. At the same time it is increasing popular in exhibitions, advertising, and entertainment. But it is too expensive to use the large-screen display system, or high-performance projectors. So it has more practical value and significance to research the multi-projector high-resolution display system based on the camera.Based on the study of domestic and foreign large format multi-projector display, we research the technology further and get one seamless high-resolution image which is mosaiced by two images projected by two independent projectors on the display wall at last. The result meets the people's needs on the high-resolution and large visual display. In the experiment, we only need two projectors, two PC and one camera, so it is low-cost.The main work in this thesis is divided into the following two keys:(1)Geometric Correction:Look for the matrix transformation relationship among the projector space, projection screen space and camera space. Eventually get the position parameters of the two projection display area and pre-distortion matrix. Then do the pre-distortion on the projected images to achieve the geometric registration.(2)Color Correction:It is divided into two parts:one is the color calibration between the two projectors, and the other is the alpha blending in the overlapping regions.In the global color correction part, we get the color transfer function of each projector using the cubic b-spline theory, then calculate their public color gamut and calibrate the input value to reduce the difference of color between the two projectors. In the part of alpha blending, we select the suitable fusion function for the overlapping regions of the two images, to eliminate the highlight effect and achieve the purpose of seamless eventually.The main innovation and improvement in this thesis: (1) In the image fusion process, when we set value for the alpha channel in the overlap, do not use the overlapped information of the projection area, but the fixed overlapping pixel information of the original images, so as to avoid calculating the irregular overlapping regions in the projection area.(2) Emphasized the two different concepts:overlapping region and blending region. Choosing appropriate blending region, we can eliminate the highlight effect in the overlapping regions better, and achieve the purpose of seamless eventually.Owing to the price of the big screen display system and the complex operation, the demand for the low-cost big screen display system is increasing. So in my experiment, we select the low-cost and simple-operating instrument to do the research. After a long time of study and experiment, we get some experimental results, and confirm the practicability and importance of the research on the low-cost multi-projectors large format mosaic.