为了实现对具有明显跳变面物体的轮廓测量, 建立了四步相移光栅投影的三维形貌测量系统, 并对所采用的四步相移测量算法进行研究。在介绍四步相移原理的基础上以有明显跳变面的三棱锥橡皮块为例, 建立针对明显跳变面的测量算法。通过对4幅相移图算术求和并除以4得到平均灰度图; 将平均灰度图二值化处理定位明显跳变面或阴影部分; 将二值化图像与包裹相位图卷积, 而后对包裹相位图进行解包裹, 从而得到正确的连续相位, 最终获取物体三维形貌。根据上述算法测量三棱锥的三维形貌并计算其体积, 测量实验表明: 被测物的体积平均相对精度为0.47%。

In order to achieve the measurement of objects with significant jumping surface profile,a three-dimensional shape measurement system based on fringe projection in four-step phase shifting was established and the adopted four-step phase-shift measurement algorithm was studied. After introducing the principle of four-step phase shifting, a measurement algorithm for the apparent jumping faces was established, by taking a triangular pyramid rubber with significant jump faces for example. Firstly, the average gray image was calculated through a sum of the four phase shifting images and divided by four. Secondly,the binaryzation of average gray image was processed to position the obvious jumping surface or shadows. Last but not least, the convolution of binary image with wrapped phase map was done and then the wrapped phase map was unwrapped to get the correct continuous phase and reconstruct the 3D shape of the object. Experiments were taken to calculate the volume of the triangular pyramid rubber by shape measurement with the proposed algorithm. Experimental results show that the mean precision of volume measurement is 0.47%, which proves the effectiveness of the proposed algorithm and its good precision.