Abstract:

In order to achieve better accuracy and speed in noncontact measurement based on vision, the camera measuring technologies and the laser measuring technologies can be integrated. In the registration process of the two measuring systems, the precise positioning of a particular marker (such as laser tags) is the key technology to improve the measurement accuracy.We propose a precise positioning method of laser tags. First, the GPUbased Histogram of Oriented Gradients (HOG) algorithm is used to detect the laser tags on the steel plate.Then,the image binarization is used for further precise positioning based on the centroid method. In the process of laser tag detection,the very large image can be detected in real time to meet the requirements of industrial measurement due to the parallel computing advantage of GPU.In the process,a novel binarization method based on Difference of Gaussian (DOG) is proposed,which can obtain better results than the traditional methods such as Otsu and Bernsen. Experimental results show that the accuracy of the proposed method can reach 1 mm or less. 

Key words: graphic processing unit（GPU）；histogram of oriented gradients（HOG）；laser tag；difference of gaussian（DOG）；image binarization