The projector-camera system has recently been studied extensively as one of new information presenting systems. For generating screen images properly, it is important to calibrate projector-camera systems accurately. The existing methods for calibrating projector-camera systems are based on 4 markers on the screen and 4 light projections from projectors, and thus require at least 8 basis points totally in images. However, it is not easy to track 8 or more basis points reliably in images, if the projector camera system moves arbitrarily. Thus, we in this paper propose a method for generating screen images properly from less basis points in camera images.