Sun Qiucheng, Hou Yueqian, Tan Qingchang, Li Guannan
College of Basic Science, Changchun University of Technology, Yanan Street 2055, Changchun 130012, China.
ScientificWorldJournal. 2013 Oct 27;2013:963621. doi: 10.1155/2013/963621. eCollection 2013.
Lens distortion practically presents in a real optical imaging system causing nonuniform geometric distortion in the images and gives rise to additional errors in the vision measurement. In this paper, a planar-dimensions vision measurement method is proposed by improving camera calibration, in which the lens distortion is corrected on the pixel plane of image. The method can be divided into three steps: firstly, the feature points, only in the small central region of the image, are used to get a more accurate perspective projection model; secondly, rather than defining a uniform model, the smoothing spline function is used to describe the lens distortion in the measurement region of image, and two correction functions can be obtained by fitting two deviation surfaces; finally, a measurement method for planar dimensions is proposed, in which accurate magnification factor of imaging system can be obtained by using the correction functions. The effectiveness of the method is demonstrated by applying the proposed method to the test of measuring shaft diameter. Experimental data prove that the accurate planar-dimensions measurements can be performed using the proposed method even if images are deformed by lens distortion.
镜头畸变在实际的光学成像系统中几乎都会出现，会导致图像中出现不均匀的几何畸变，并在视觉测量中产生额外误差。本文提出了一种通过改进相机标定的平面尺寸视觉测量方法，该方法在图像的像素平面上校正镜头畸变。该方法可分为三个步骤：首先，仅使用图像小中心区域的特征点来获得更精确的透视投影模型；其次，不是定义统一模型，而是使用平滑样条函数来描述图像测量区域中的镜头畸变，并通过拟合两个偏差曲面获得两个校正函数；最后，提出一种平面尺寸测量方法，其中使用校正函数可获得成像系统的精确放大倍数。通过将该方法应用于测量轴直径的测试，证明了该方法的有效性。实验数据证明，即使图像因镜头畸变而变形，使用该方法也能进行精确的平面尺寸测量。
