MIRROR IMAGING METHOD WITH SPECKLE PATTERN ILLUMINATED BY WHITE LIGHT FOR PLATE BENDING MEASUREMENT.

If an object surface is covered with some special coatings (e. g. minute glass-beads, silver-powder paint etc. ), it produces a random speckle pattern when illuminated by white light. By recording the variation of the white light speckle pattern while the object surface is being deformed, information on the displacement and deformation of the surface is recorded. This method is called white light specklegraphy. However, when the method is used for surface bending it only gives 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. The method is described, and its advantages are discussed.