Directional phase-shift circular arrays targets for out-of-focus camera calibration

Abstract

We design a directional phase-shift circular arrays targets to calibrate camera system under the assumption that targets are in a defocus condition. In contrast to conventional camera calibration method, we can achieve accurate camera calibration with severely defocused images by using the proposed directional phase-shift circular arrays targets. In this paper, three directional phase-shift circular arrays targets are used to calibrate the measurement system. We set up a mathematical model to detect the feature points accurately even though the targets images are seriously blurred. In the experiments, the targets are displayed in a LCD monitor, camera system can capture the three targets images at the same position to extract the feature points. Gaussian filters are utilized to blur the targets images to simulate the fuzzy images. And we obtain targets images with different defocus degree by adjusting the depth range of the actual camera system. We have done a series comparative tests with checkerboard. We evaluate the performance of the proposed method on simulated and real data. Finally, the measurements of displacement and morphology are implemented. Experimental results indicate that the directional phase-shift circular arrays targets can be used to achieve accurate camera calibration parameters.