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复杂物体的快速三维测量是光学三维轮廓术的难题之一。提出了基于调制度比的光学三维测量新方法,设计了基于共轴光路的测量系统。理论分析表明,在几何光学近似下,物体表面一点调制度比的对数与该点的高度成正比,因此可以用调制度比作为物体高度的载体。通过标定建立高度与调制度比的查找表,测量时利用CCD在两个不同的位置分别获取物体表面的光栅信息,利用傅里叶变换方法计算相应物点的调制度并计算比值,根据调制度比值通过查找表得到相应物点的高度信息。该方法采用共轴光路,有效避免了阴影和遮挡问题;采用调制度比作为物体高度测量的载体,只需要两幅光栅图就可以得到物体的高度信息,具有测量快速的优点。对高为79.51 mm的台阶测量的相对误差为0.86%,实验结果证实了该方法和系统的有效性。
Rapid 3D measurement of complex objects is one of the challenges of optical 3D profilometry. A new optical three-dimensional measurement method based on modulation ratio is proposed, and a measurement system based on coaxial optical path is designed. Theoretical analysis shows that under the geometrical optics approximation, the logarithm of the one-point modulation ratio of the object surface is directly proportional to the height of the point, so the modulation ratio can be used as the carrier of object height. Through the calibration, a look-up table with height-to-modulation ratio is established. The grating information of the surface of the object is obtained by CCD at two different positions during the measurement. The degree of modulation of the corresponding object point is calculated by Fourier transform and the ratio is calculated. Ratio through the look-up table to get the height information of the corresponding point. The method uses a coaxial optical path, which effectively avoids the shadowing and occlusion issues. Using the modulation ratio as the carrier of the object height measurement, only two raster images are needed to obtain the object height information, which has the advantages of rapid measurement. The relative error of the measurement of the step height of 79.51 mm is 0.86%, and the experimental results confirm the effectiveness of the method and the system.