MINUTE DISPLACEMENT-MEASURING APPARATUS USING MOIRE FRINGE

PROBLEM TO BE SOLVED: To provide a minute displacement-measuring apparatus utilizing moire fringes which can quickly measure a displacement in an optional direction within a plane perpendicular to the direction of a collimation line of an object to be observed, in a non-contact manner with the use of moire fringes. SOLUTION: A checkered solid grating 1 is photographed by a TV camera 3. A photographed output is converted to a digital signal by an A/D converter 41 included in an image-processing circuit 4. Image data of the solid grating are stored in a memory 42. Image data of a reference grating formed separately and the stored image data of the solid grating are added and averaged by an operation circuit 43, whereby image data of moire fringes are output. A minute shift of an observation point is measured on the basis of a shift of the image data.