An optical device which generates an optically variable image, the image being optically variable in that it varies according to the position of observation, is manufactured by dividing an optically invariable image into multiple pixels. Color component values are determined for each pixel. For each of the pixels of the optically invariable image, there is determined an associated pixel surface structure which has a three-dimensional surface shape and curvature which is related via a mathematical of computer algorithm to the color component values of the associated pixel in the optically invariable image, each pixel surface structure being an individual reflective or diffractive surface structure which produces an observable optical effect. An assembly of the reflective or diffractive pixel surface structures is produced which when illuminated generates a plurality of observable optical effects which combine to form an optically variable reproduction of the optically invariable image.