An interactive cameraless projector calibration method

The geometric calibration of projectors is a demanding task in many areas related to computer vision, virtual reality or augmented reality, to name some. Up to date, different methods have been proposed to retrieve the intrinsic and extrinsic parameters of projectors. During the last 20 years, researchers have used cameras as means to calibrate projectors in order to automatize the process. However, this might add: (1) complexity in terms of mathematical formulation; (2) restrictions in terms of camera locations relative to projectors; and (3) additional errors (those due to the camera calibration itself). Most of these camera-based methods make use of planar homographies, and others require an extended calibration process (for both the camera and the projector). In this paper, we present an approach that combines a direct transformation method (DLT) with projected augmented reality to perform an interactive calibration of projectors without the need for cameras. This method is based on non-coplanar points and 2D/3D correspondences, which are interactively established. Intrinsic and extrinsic calibration is achieved in a single step, making use of the DLT. The method rescues old approaches to calibrate projectors, but brings the new capabilities of interactive systems, all integrated in a single software solution. We conduct different experiments by considering two projector setups and two different sets of control points, proving that the accuracy of the method in the real space can be between one and two pixels.