Bionic Orientation and Visual Enhancement With a Novel Polarization Camera

The remarkable polarization vision of animals provides a significant inspiration for robotic navigation and visual enhancement, as polarization pattern provides additional information besides spectral signatures. A novel bio-inspired polarization camera is proposed in this paper, which can realize real-time image-based polarization measurement. The composition of the system is described and the optimal estimation of the polarization state is derived based on the least square algorithm. This paper concentrates particularly on the camera orientation algorithms and visual enhancement methods with it. To estimate the camera's heading angle with the skylight polarization pattern, the sun vector is established as an optimization problem of finding the minimum eigenvector. The solar meridian is also estimated from the degree of polarization pattern by detecting reflectional symmetry axes. The result shows that the measured polarization patterns are very close to the theory. The maximum orientation error of the proposed method based on angle of polarization is about 0.5°. The average error is 0.012° with standard deviation of 0.28°. Thus, the novel polarization camera could be used as sun compass. When observing scenes in distance, the polarization camera is used to decouple the airlight from the object radiance, which results in much better contrast. More importantly, the polarization information is helpful for scene identification and object detection. The result also shows that the polarization camera can reasonably cope with the semi-reflection problem.