Motion cards are appearing everywhere these days. They have been around for some time, but have increased dramatically in the number of images on a card in recent years. Early versions only had two or three images, but new ones can hold enough images to simulate a couple seconds of video!

This card shows one image at this angle...

and another image at this angle...

and yet another at this angle. In fact, this card has about 20 different images depending on the angle of view.

Motion cards use a special technology called lenticular printing. This process takes a batch of images and prints alternating strips of each image on the back of a transparent plastic sheet. The plastic sheet has a series of curved ridges. Each curved ridge is a lenticule. When light passes through the plastic sheet, it is reflected from smooth white paper under the plastic sheet.

Each color represents a different image.

Each lenticule is approximately 0.3 millimeters wide. You can see them if you look closely at a motion card. You can also feel the ridges made by the lenticules.

The returning light passes through the image strips printed on the plastic sheet. The lenticule is made in such a way that it refracts the returning light at a specific angle and magnifies the image. The strips are aligned so that all of the strips for a particular image are refracted to the same point. Because of the refraction and magnification, what you see is a single, complete image that appears to cover the entire card. As you change the angle of the card in relation to your line of sight, you see the different image strips as a series of complete images.

A close-up of a motion card shows the curvature of the lenticules.

To learn more about motion cards, be sure to check out the patents on the process and the printing mechanism. Kodak, who calls their version of lenticular printing Dynamic Imaging, is a leader in this technology. They have been able to refine the process to the point that they can combine dozens of images in very tiny strips to make a card that is capable of displaying a smooth video or animation as you slowly change the viewing angle of the card. Kodak has some great examples of the various motion card techniques in use on this page.

Here are some interesting links: