Screen-monitored stitching deflectometry based on binocular stereo vision

The measurement accuracy of the current phase measuring deflectometry (PMD) methods for in-situ measure-ment of the surface shape of large-aperture optics, which are placed at different inclination angles, is affected by the varied pose and deformed shape of screen due to manufacturing, external force and temperature variation, etc. This paper proposes a novel PMD method, the screen-monitored stitching deflectometry (SMSD), by combining binocular stereo vision with stitching deflectometry. And a four-camera PMD measurement system is constructed accordingly. The coordinates of the point source are determined using binocular stereo vision technology; based on the acquired coordinates, the stereo-iterative reconstruction and stitching algorithm are used to achieve the surface shape measurement. Simulations and experiments are accomplished to validate the advantages of the proposed method in reducing measurement errors caused by the varied pose and deformed shape of screen.