Digital image correlation (DIC) is a noncontact technique that is widely used for deformation measurement, but improving the calculation efficiency to achieve real-time DIC calculation has always been a big concern. A parallel temporal sequence DIC method is proposed, which chooses seed points to determine the integer-pixel displacement and applies the moving least-squares fitting technique to acquire the subpixel displacement. This method avoids traditional complex iterations and takes full advantage of the GPU parallel computing. Results of a simulation experiment and an actual experiment demonstrate the accuracy and efficiency of the proposed algorithm. The calculation speed in the simulation experiment of the proposed method achieved 463,320 POI/s, whereas the speed in the actual experiment was 432,866 POI/s, when the speed of the ICGN method was 2700 POI/s and 2074 POI/s under the same accuracy, respectively. Also, the subpixel displacement calculation made up less than 1% of the entire calculation. The computational efficiency could be further enhanced if a faster integer-pixel displacement calculation method is discovered or a parallel algorithm is used.
In this work, we propose an laser-interference based measurement method that employs a hardware device in the reference arm to track the out-of-plane displacement in the objective arm. Then a real-time one-point out-of-plane displacement measurement system is built up using a Michelson interferometer, a PZT device, a CCD camera and a tracking control system. The system works by checking the movement of fringes and then promoting PZT to track the displacement. A tracking algorithm including direction judgment and correlation computation is developed to decide whether PZT is started and the distance that PZT is ordered to move. Experimental results demonstrate the effectiveness of the system and finally the detailed mechanism of the system is discussed.