【摘要】 本文提出一种利用表面反射成象原理测量表面弯曲斜率的白光散斑方法。给出了信息记录原理及三种记录光路,分析了产生测量误差的主要因素,初步探讨了测量灵敏度范围及提高杨氏条纹质量的基本途径。实验表明,本方法等价于一种具有连续变化栅线方位的Ligtenberg反射云纹方法,对于表面具有一定反射能力的平板型物体之弯曲斜率的测量是可行的。更多还原

【Abstract】 It is known that, if an object surface is covered with some special coatings (e. g. minute glass-beads, silver-powder paint etc.), it will give a kind of random speckle pattern while being illuminated by white light. By recording the variation of the white light speckle pattern while the object surface is being deformed, the information of displacement and deformation of the surface will be recorded. This forms a method called white light specklegraphy. In compari- son with the laser specklegraphic method, this method has such advantages as simplicity in setup, non-contacting with the surface, lower surface requirment, and higher accuracy and sensitivity. Moreover, when dealing with the speckle movement in space it is simpler, and therefore has a lower requirment for light source. However, as the speckle field reveals itself merely on the surface of the object, the common white light specklegraphic method for measuring surface bending can only give the surface deflection (the out-of-plane displacement caused by curving) but not the strain of flexure (the bending slope) in a direct way. In order to make up for this defect, a white light speckle method based on the imaging principle of reflection from the surface for directly measuring the surface bending slope is proposed in this article. The principal procedure of our method is like this: An once-exposed negative plate of laser speckle pattern is illuminated by white light and a virtual specklegram image is formed by reflection of the sample surface. Then, the image is recorded by a camera with isochronous double exposures before and after the deflection of the surface, and the slope iuformation of points on the sample surface can be obtained from this linearly-developed negative plate by pointwise Fourier filtering. The principle for information recording as well as three kinds of recording arrangement are described in detail. Some discussions on the main factors of measurement error, on the range of measurement sensit- ivity, and on the ways of improving the quality of Young’s fringes are also mentioned. Experimental results show that this method is analogous to some kind of Ligtenberg’s reflective moire method with a grating capable of varying its orientation continuously, but our method is even simpler, more feasible, and more convenient to be performed. It is applicable to measuring the bending slope of a plate surface with certain reflectivity.更多还原