A method for projector brightness calibration for tiled displays

Many types of advanced visualizations can benefit from tiled displays. Tiled displays provide higher resolutions by combining multiple lower resolution displays. In this paper, we present a solution for one of the problems in projector-based tiled displays. While theoretically they allow seamless merging of each projection, several problems have to be overcome to achieve this. One of the problems is in overlapping areas of projections where the combined brightness is too high, so some sort of brightness correction has to be performed. This usually cannot be performed using a simple linear fading transformation due to non- linear brightness transfer functions of projectors which can even differ among projectors of the same model. In this paper, we propose a method for projector brightness correction in overlapping projection areas of tiled displays. A video camera is used to determine the optimal brightness correction factor for several image samples through an iterative process. After enough samples have been processed, we estimate a correction function for the entire image brightness range by fitting a simple curve. We present experimental results for different number of samples and different types of projector transfer functions. The validation of the results has been conducted by a second camera and by several observers using synthetic images and recorded video.