基于Ward反射模型的航天密封圈表面缺陷检测

Surface Defect Detection for Aerospace Sealing Rings Based on Ward Reflection Model

为有效检测航天系统密封圈表面的缺陷,提出一种基于Ward反射模型的检测方法。根据Ward反射模型计算密封圈曲面在不同光源方向和不同观测方向下的辐射强度。通过计算得到密封圈表面的灰度阈值,提取出相机采集的密封圈表面高亮区域。对于不带缺陷的密封圈,当某区域产生缺陷后,该区域各像素点的表面法向发生改变,造成在相同的光源方向与观测方向下,表面灰度图像中高亮度区域与基于Ward模型的表面高辐射区域在数量和位置上不对等。由基于Ward模型的辐射图像确定比值ks,提取出该密封圈不带缺陷时其灰度图像中的高亮度区域。在提取出的相机采集的密封圈表面高亮区域中,结合图像噪声、密封圈表面细微粉尘和若该密封圈不带缺陷时的灰度图像中的高亮度区域这三者面积,筛选出密封圈缺陷区域。实验结果表明,该方法能够有效地提取密封圈表面的凹痕、飞边等缺陷,并能给出占据的像素面积。

In order to detect the surface defects of the sealing rings more effectively,a detection method is proposed based on Ward reflection model. It calculates radiation intensity of sealing ring surface under different light source directions and different observation directions according to Ward reflection model. The gray threshold value of the sealing surface is calculated, and the highlighted region of the sealing ring surface is extracted by the CCD camera. For sealing rings without defects,when a region is defective,the surface normal direction of each pixel in the region is changed compared with the original one,this results the high brightness region in the surface gray image is not equal to the number and position of the surface high radiation area based on the Ward model in the same direction of the light source and the direction of observation. The ratio ks is determined by the radiation image the Ward model based on,and the high brightness region of the gray image is extracted when the sealing ring is not defective. In the highlight area of the sealing ring surface which is acquired by the CCD camera,combined with the image noise,the fine dust on the surface of the sealing ring and the high brightness area in the gray image of the sealing rings without defects,the defect area of the sealing rings is selectell. Experimental results show that the proposed method can effectively extract the dent,flash and other defects on the sealing rings, and the pixel area of the defects is given.