Geometric Calibration For Seamless Mulit-projector Display System Automatically Based On Feedback Of The Camera

Multi-projector seamless system is a kind of display system which is formedby image stitching projected by multiple projectors together and has ultra-highresolution, oversized, sense of immersion strongly. It has flexible scalability, lowcost characteristics which can meet people’s growing demands for display systems.After years of development multi-projector display system has matured and has awide range of applications in the medical, entertainment, traffic control and otherfields. To achieve splicing images seamlessly and neatly projected by multip leprojectors, geometrically coherent content, display system must be geometricallycorrected. Traditional interactive manual geometric correction requires expensiveequipment and a lot of human resources to build and ma intain the system. Thisgreatly increases the cost and difficulty of realization of extensive application ofmulti-projector display system. Although existing automatic geometric correctionalgorithm avoids manual calibration proble ms by introducing the camera, it doesnot have high robustness; external uncertainties inevitably affect the correctioneffect which directly leads to failure of calibration.In this paper, a study on this problem is carried out.An algorithm which ismulti-projector geometric correction automatically based on the feedback from thecamera in two steps is proposed. The first step is coarse correction. Only need touse the camera of which calibration parameters are known to automaticallycomplete crating three groups geometric relationship between projection displayspace Dand camera space C, projectors buffer space Pand camera space C,the original image space and sub-image space as an auxiliary without manualinvolve ment.According to the established relationship among the three groups,make the image that will be projected pre-distort transformation so that the contentof fina l image on the projection display screen is neatly geometrically coherent.In order to further improve the accuracy and robustness of automaticgeometric correction, the second step named fine calibration is designed by theproposed algorithm. Firstly, catch the geometric correction effect by camera andmake the image do perspective transformation to the projection display screencoordinate space. Secondly, calculate the data of all projector calibration targetpoints and record them. Finally, determine the projector which doesn’t have idealgeometric correction effect, exceeding the threshold value. To achieve rapidjudgment, a method is designed according the rule that color will be changed whendifferent projectors’ overlay. According to the data of standard target points, calculate the perspective transforrmation matrixH idetermined by convertingfrom the error points position to target points position. Experimental resultsdemonstrate the feasibility of the proposed algorithm. Compared with theexisting automatic geometric correction algorithm, the proposed algorithm is moreflexib le and suitable for setting up and maintenance of large physical sizemulti-projector display system, can be used as reference for similar studies.