Tilt cards trace back to corrugated pictures older than photography
That winking-eye postcard works because a sheet of tiny ridged lenses sends each thin stripe of an image in its own direction. Tilt it, and your eye catches a different picture. The idea is ancient in spirit: ridged double paintings were around in the 1600s, and turning pictures delighted English viewers a century before that.
A lenticular print starts with at least two pictures. Each is cut digitally into narrow strips, and the strips from all the pictures are woven together into one file, a step called interlacing. That combined image is printed either straight onto the smooth back of a plastic lens sheet or onto synthetic paper that gets laminated to it. Registration must be exact; if the slices drift even slightly under the lenses, the viewer sees ghosting and blur.
The lenses decide what effect you get. When a big change in angle is needed to switch images, you get a flip: a print at Centre Mario-Tremblay in Alma, Quebec, turns the hockey player from a boy with the Alma Eagles into a Montreal Canadien. A medium angle produces motion, zooms or morphs, as on the poster for Species II. A very small angle lets each eye see a slightly different frame, which creates depth without glasses; the Dolby-Philips display used 28 separate images this way. Stereo depth only works when the strips run side by side, because the two eyes sit horizontally apart.
Before true lenses, inventors used grooves and line screens. H.C.J. Deeks patented a ridged photographic postcard in 1906 and followed it with a colour-changing version in 1907. Auguste Berthier described a line-sheet autostereogram in Le Cosmos in May 1896, though few noticed, while Frederic Eugene Ives had more success from 1901. John Jacobson applied for a US patent in 1898 for a stereograph behind a channelled transparent mount, an early step toward the modern sheet.
Gabriel Lippmann, the Nobel-winning French physicist, proposed in 1908 a screen of tiny lenses modelled on insect eyes, each recording the scene from its own slight angle. Today the sheets are usually PETG or APET plastic, and the format had a burst of popularity in the 2000s, reaching trading cards, store signs and the May 2006 cover of Rolling Stone.
Source: Lenticular printing
