摘要
光学测量是一门发展迅速的信息测试技术,散斑计量作为光学测量领域中一类重要的测量方法,具有全场非接触、测量精度较高、测量方法简单等优点。
本文提出了一种改进的数字散斑摄影方法。通过对位移前后散斑图在计算机中叠合后快速傅立叶变换得到杨氏干涉条纹图,不经过条纹细化,直接再次对所得条纹图样的强度图像进行快速傅立叶变换从而得到该图像的空间频谱图样,进而可以直接得到原物体的位移。在再现过程中省去了空间光调制器件,简化了系统结构。在提取衍射亮点位置时,提出了一种基于像素扩展的亚像素处理方法,使得系统的测量精确度得到进一步提高。
按照理论方法,搭建了微米级位移数字散斑测量实验系统,并进行了大量的实验。实验中对散斑图不同模式的叠合做了比较,对物面的面内位移进行了测量并对亚像素处理方法进行验证。还使用白光光源代替激光光源进行了可行性验证。接着使用了旋转方式模拟得到双散斑图法,把测量物面的面内位移扩展到测物体空间三维位移。由选定的空间坐标系导出了本系统测量空间位移的公式,其只与两次拍摄散斑图的夹角有关。最后进行了测量空间位移的实验验证。
Optical measurement is an information measurement technology developing rapidly, speckle measurement as an important measurement method in optical measurement which have many advantages like non-contact measurement, high definition measurement and simple process.
This paper designed an advanced speckle photography method. Using Fast Fourier Transform process the speckle images attained the Young’s fringe image, then, using Fast Fourier Transform once again on intensity pattern of the Young’s fringe image attained its spatial spectrum pattern. We can measure the object`s displacement from the spatial spectrum pattern directly. In the process, it economized the spatial light modulator then simplified the system structure. In the paper also used a sub-pixel processing method with pixel expansion to improved accuracy of measurement system.
According to the theory above, we construct a digital speckle measurement system of the micron dimension and conduct a large number of experiments. Contrast the different of various incorporation methods with the two speckle images. Have a measurement with the in plane displacement and verified the sub-pixel processing method proposed above. We even used the white light displaced the laser to took the measurement experiment. Then simulated dual speckle pattern to extended the in plane displacement measurement to three-dimensional spatial displacement measurement by used a rotating method. Attained the displacement measurement equation of the system from selected the special space coordinates system. The equation just relate with values of two angles between the two speckle patterns taken on. Finally, we took some experiments to measure the spatial displacement.
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