Optical images.

A substrate is arranged to provide at least one optically variable image, the substrate being formed with a plurality of groups of elemental areas, the different groups forming respective image pixels. The different elemental areas (A1 to An) of eachi group are tormed with respective grooves or ridges or sets of grooves or ridges (121 to 12n), which are at different orientations m the different elemental areas such that each elemental area of each pixel directs light to the viewer for a respective angle of view: for any given angle of view, the image seen by the viewer is made up of light reflected or refracted without interference from the different pixels, but only from a respective elemental area of each pixel.