Flexible camera-projector calibration using superposed color checkerboards

Camera-projector calibration is essential in structured-light systems for three-dimensional imaging. A prevalent difficulty for calibration is that two different checkerboards must be captured. First, a physical checkerboard on the reference plane is required to obtain the camera parameters. Second, the physical checkerboard must be removed because it interferes with the projected pattern required to obtain the projector parameters. These requirements can be reduced if the camera is previously calibrated or specific arrangements are considered. However, the calibration procedure is very impractical and susceptible to misalignment errors. In this paper, a flexible camera-projector calibration method without any constraint on the position and orientation of the camera, the projector, and the reference plane, is proposed. For this, a physical checkerboard of a specific color is placed on the reference plane while the projector device projects another checkerboard with a different color. From an image captured by the camera, the two superposed checkerboards are recovered using the color information. In this way, the homographies required for calibration of both the camera and the projector are obtained simultaneously. The performance of the proposed method is verified experimentally by measuring the three-dimensional surface of three objects. Because of its high flexibility and accuracy, the proposed method is useful for in situ calibration of structured-light systems for three-dimensional imaging applications.