Tomás María-Baralida, Ferrer Belén, Mas David
University Institute of Physics Applied to the Sciences and Technologies, University of Alicante, P.O. Box 99, 03080 Alicante, Spain.
Sensors (Basel). 2020 Nov 18;20(22):6596. doi: 10.3390/s20226596.
A known technique to obtain subpixel resolution by using object tracking through cross-correlation consists of interpolating the obtained correlation function and then refining peak location. Although the technique provides accurate results, peak location is usually biased toward the closest integer coordinate. This effect is known as the peak-locking error and it strongly limits this calculation technique's experimental accuracy. This error may differ depending on the scene and algorithm used to fit and interpolate the correlation peak, but in general, it may be attributed to a sampling problem and the presence of aliasing. Many studies in the literature analyze this effect in the Fourier domain. Here, we propose an alternative analysis on the spatial domain. According to our interpretation, the peak-locking error may be produced by a non-symmetrical sample distribution, thus provoking a bias in the result. According to this, the peak interpolant function, the size of the local domain and low-pass filters play a relevant role in diminishing the error. Our study explores these effects on different samples taken from the DIC Challenge database, and the results show that, in general, peak fitting with a Gaussian function on a relatively large domain provides the most accurate results.
一种通过互相关进行目标跟踪来获得亚像素分辨率的已知技术，包括对获得的相关函数进行插值，然后细化峰值位置。尽管该技术能提供准确的结果，但峰值位置通常会偏向最接近的整数坐标。这种效应被称为峰值锁定误差，它极大地限制了这种计算技术的实验精度。该误差可能因用于拟合和插值相关峰值的场景和算法而异，但一般来说，它可能归因于采样问题和混叠的存在。文献中的许多研究在傅里叶域分析这种效应。在此，我们提出一种在空间域的替代分析方法。根据我们的解释，峰值锁定误差可能由非对称样本分布产生，从而导致结果出现偏差。据此，峰值插值函数、局部域的大小和低通滤波器在减小误差方面起着重要作用。我们的研究探讨了这些效应对从DIC挑战数据库中获取的不同样本的影响，结果表明，一般来说，在相对较大的域上用高斯函数进行峰值拟合能提供最准确的结果。
