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Polarization calibration of fisheye cameras using skylight in the wild
arXiv cs.RO0 views
arXiv:2611.08911v1 Announce Type: new Abstract: Skylight polarization provides directional cues for robotic navigation, but fisheye lens effects and analyzer imperfections can degrade polarization measurements across the field of view. We present a joint lens-analyzer calibration method that explicitly models incidence-dependent lens transmission together with analyzer gains and angular offsets in a unified eight-parameter formulation. Given known geometric calibration, rotations between camera frames can be estimated using visual features and cross-frame directional polarized light consistency can be used for polarization calibration. Therefore, our calibration approach requires only a short handheld outdoor sequence under natural skylight, without dedicated polarization calibration equipment or a predefined sky polarization model. On real-world outdoor sequences, the proposed method achieves a weighted cross-frame angle-of-linear-polarization (AoLP) mean absolute error below 0.5{\deg} across all incidence angles, with a 73.4% reduction in the 80{\deg}-90{\deg} incidence angle region, and generalizes to an independent sequence with an overall mean absolute error of 0.466{\deg} without refitting. Preliminary solar-azimuth experiments using a camera mounted on a quadruped robot further show improved alignment with the visible solar center, supporting the potential of calibrated AoLP measurements for relative-heading estimation and future polarization--inertial navigation. The calibration software tool will be released upon acceptance of this paper.
Source:https://arxiv.org/abs/2611.08911PreviousFATHOM: World-Model-Guided Diffusion Action-Trajectory Selection for Sparse-Marker AUV TrackingNextHomeLoop: A Simulation Framework and Benchmark for Robot-IoT Coordination in Everyday Domestic Assistance and Safety
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