缸盖缺陷检测系统线阵相机现场标定方法

Calibration of line array camera for head defect detection system on cylinder cover

为检测某型号发动机缸盖表面缺陷,需获取缸盖表面的精确尺寸,本文设计了发动机缸盖表面视觉检测设备,应用该设备平台针对线阵相机中的镜头畸变提出了一种新的标定方法。首先,根据测量精度要求,设计缸盖视觉检测设备,利用高精度的设备平台确定线阵相机测量高度和成像角度;然后,通过建立的线阵相机成像的数学模型,忽略畸变情况下,在中心光轴处求得相面中心坐标,并利用最小二乘法求得相机内外参数;最后,考虑镜头畸变,建立畸变数学模型,利用最小误差法对镜头畸变参数标定。实验结果表明:该方法提高了相机的测量精度和稳定性,校正后图像的最大变形量不高于±0.25Pixel,测量平均误差为0.356%,可满足实际工程需要,具有较高的实用价值。

In order to detect surface defect of engine cylinder head, accuracy size data of the surface is needed. A visual detect device of engine cylinder head is designed, and a new calibration method is proposed for the purpose of correcting the linear array camera lens distortion. First, according to the detecting requirements, height and angle data of the linear array camera is determined using high-accuracy detection system. Second, by establishing the mathematical model of the linear array camera image, ignoring the distortion, the image center coordinates with respect to the optical axis are obtained, and the camera parameters are acquired by least square method. Finally, considering lens distortion, a mathematical distortion model is established. The obtained parameters are used as the initial values to solve the distortion parameters using minimum error method. Experimental results indicate that this algorithm can get higher accuracy and stability. The maximum distortion is less than ±0.25 pixel, and the average measuring error is 0.356%, which can meet the requirements of practical engineering and has high practical value.