US Patent 7230722 Shadow moire using non-zero talbot distance

A method for measuring deformation in specimens is provided. The method includes providing a shadow moiré system, the shadow moiré system including an illumination source, a reference grating and an image capture device and providing a specimen. The method further includes determining a selected distance between the specimen and the reference grating, and illuminating the specimen with light from the illumination source directed through the reference grating onto the specimen, thereby forming shadow moiré fringes onto the specimen. The method further includes capturing an image of the shadow moiré fringes by the image capture device.