Robust circular marker localization under non-uniform illuminations based on homomorphic filtering
Robust circular marker localization under non-uniform illuminations based on homomorphic filtering
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DOI：
10.1016/j.measurement.2020.108700
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发表时间：
2020-11
期刊：
影响因子：
5.6
通讯作者：
Shuai Dong;Jiangqin Ma;Zhilong Su;Chuanxi Li
中科院分区：
文献类型：
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作者：
Shuai Dong;Jiangqin Ma;Zhilong Su;Chuanxi Li
圆形标记广泛应用于基于图像的测量领域，例如视觉系统校准、位移测量和振动监测。通常，标记定位误差不可避免地导致不准确的结果。光照不均匀是影响圆形标记定位精度的关键因素之一。为了减少光照不均匀对图像质量的影响，提出了一种同态滤波-灰度加权质心法。首先，介绍了高频及其与GWCM结合的基本原理。最后，通过仿真实例分析了非均匀光照条件下，HF参数和不同定位方法对同心圆标记定位精度的影响。最后，采用单摄像机多光源成像系统对高频GWCM的有效性进行了验证。分析了不同光照不均匀情况下，包括光照移动、多光源、阴影区域等情况下，高频GWCM的定位精度和稳定性。结果表明，高频GWCM具有抗非均匀光照干扰的能力，是提高圆形标记定位精度的有效途径。
Circular markers are widely used in image-based measurement fields, e.g. vision system calibration, displacement measurement, and vibration monitoring. Generally, the marker positioning error inevitably leads to inaccurate results. As one of the key factors, the non-uniform illumination seriously affects the localization precision of circular markers. In order to reduce the influences of uneven lighting, a homomorphic filtering-gray weighted centroid method (HF-GWCM) is presented in this work. Firstly, the basic principles of both HF and its combination with GWCM are introduced. Subsequently, some simulation examples are conducted to analyze the localization accuracy of concentric circle markers under non-uniform illumination situations, which comprise the influences of HF parameters and different localization methods. Finally, a single camera imaging system with multiple light sources is employed to perform some tests for the effectiveness validation of HF-GWCM. Both positioning accuracy and stability of HF-GWCM are analyzed under different uneven illumination situations, including lighting movement, multiple light sources, and shaded region. Results demonstrate that HF-GWCM owns the ability to resist the interference of non-uniform illuminations, and it is also an effective way to improve the localization accuracy of circular markers.