The process can also be used to create images that change over time as the illumination changes, resulting in animated pictures that move just from changes in the sun's position, with no electronics or active control.
The basic concept is similar to those inexpensive 3-D displays sometimes used on postcards and novelty items, that use an overlay of plastic that contains a series of parallel linear lenses that create a visible set of vertical lines over the image. (It is a different approach from that used to create holograms, which require laser light to create.) In addition to three-dimensional images, these are sometimes used to present a series of images that change as you view them from different angles from side to side. This can simulate simple motion, such as a car moving along a road.
By using an array of tiny square lenses instead of the linear ones, such displays can also be made to change as you change the viewing angle up or down - making a "4-D" image. This reveals different views with horizontal as well as vertical movement of the viewer. The new "lighting aware" system adds additional layers of lenses and screens to add two more dimensions of change. The image that is seen is then not only based on the position of the viewer, but also on the direction of the illumination.
The new system, still in a relatively low-resolution laboratory proof-of-concept, could have applications including pictures used for training purposes, he said. In training someone how to carry out industrial inspections, an image of the device to be inspected would respond just like a real object when the inspector shines lights on it from different angles, for example.
Because the system is being built by hand from custom-made parts, Raskar says, the present version costs about $30 per pixel to make. Since it takes thousands of pixels to create a recognizable image, practical devices at an affordable price will require significant further development. "It will be at least 10 years before we have any realistic practical-sized displays," he estimates.