Speckle shearography using a multiband light source

Applications for optical metrology usually use lasers as light sources, because of the excellent spatial and temporal coherence of the emitted light. By comparison, the demands of speckle shearography concerning the coherence of the light source are low. This enables certain white-light sources to be an option.

In this paper, the feasibility of low coherence shearography is shown. For this purpose an experimental setup is designed, composed of a mercury arc lamp, a spatial filter and a Michelson interferometer. With respect to speckle shearography, important characteristics of the light source are described and the mercury arc lamp is shown to be suitable. Finally, some experimental investigations of an object under load are presented.  

Measurement of pure curvature fringe distribution by using a double whole-field filtering technique

A double whole-field filtering technique to measure pure curvature fringe distribution of a deformed object is proposed. In this method, the slope fringes which are contained in the pattern of curvature fringes can be completely eliminated from the curvature fringes. Thus the pattern of pure curvature fringes with a good contrast can be obtained. Theoretical analysis and experimental results are given in this paper.  

旋转锥镜散斑剪切术测量动态扭率和斜率

采用旋转锥镜技术，进行激光散斑剪切照相，测量变形物体的动态扭率和斜率，拍摄一幅散斑图可获得扭率和斜率动态变化的全过程。  

Simple spatial filtering for shearograms

The spatial frequency spectrum of shearographic speckle patterns is analysed. Shearogram reconstruction with high contrast fringes is possible using spatial filters adapted to the spectrum. This filtering is not only possible in Fourier processing set-ups, but also can be easily realized with a camera and a white light source.