DIFRACTION SURFACES AND METHODS FOR THE MANUFACTURE THEREOF

摘要

A diffraction surface (10) and a method of making the surface. The surface (10) may be applied to labels and other items to identify the origin of the goods to which the label is attached. The surface (10) can include a block grating including ridges (11, 13) and recesses (15) in the enclosed squares or rectangles. The diffraction grating (10) is manufactured by processing a data stream indicative of the image, including obtaining a Fourier Transform of the data stream and preferably clipping and quantising the data stream, and deforming a plate surface in accordance with the data stream. Also claimed is a diffraction grating having spaced first and second portions each producing an image on a receiving surface in response to illumination by a reading light beam, configured such that when the reading light beam moves from the first to the second portion, a change occurs in the first image to produce the second image.